Merge branch 'master' into alias-based-completion2

.github/workflows/ci.yaml

@@ -24,6 +24,9 @@ jobs:
     runs-on: ${{ matrix.os }}
     env:
       CC: deny_c
+      # we want to build r-a on stable to check that it keeps building on stable,
+      # but we also want to test our proc-macro-srv which depends on nightly features
+      RUSTC_BOOTSTRAP: 1
 
     strategy:
       fail-fast: false
@@ -50,15 +53,15 @@ jobs:
         run: sed -i '/\[profile.dev]/a opt-level=1' Cargo.toml
 
       - name: Compile (tests)
-        run: cargo test --no-run --locked
+        run: cargo test --no-run --locked  --features sysroot-abi
 
       # It's faster to `test` before `build` ¯\_(ツ)_/¯
       - name: Compile (rust-analyzer)
         if: matrix.os == 'ubuntu-latest'
-        run: cargo build --quiet
+        run: cargo build --quiet --features sysroot-abi
 
       - name: Test
-        run: cargo test -- --nocapture --quiet
+        run: cargo test --features sysroot-abi -- --nocapture --quiet
 
       - name: Run analysis-stats on rust-analyzer
         if: matrix.os == 'ubuntu-latest'

Cargo.lock

@@ -1250,6 +1250,7 @@ dependencies = [
 name = "proc-macro-srv-cli"
 version = "0.0.0"
 dependencies = [
+ "proc-macro-api",
  "proc-macro-srv",
 ]
 
@@ -1457,7 +1458,7 @@ dependencies = [
  "parking_lot 0.12.1",
  "parking_lot_core 0.9.6",
  "proc-macro-api",
- "proc-macro-srv",
+ "proc-macro-srv-cli",
  "profile",
  "project-model",
  "rayon",
@@ -1641,9 +1642,9 @@ checksum = "a507befe795404456341dfab10cef66ead4c041f62b8b11bbb92bffe5d0953e0"
 
 [[package]]
 name = "smol_str"
-version = "0.1.25"
+version = "0.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9d268d24892b932cac466d214af6ec8a3ec99873f0f8664d9a384b49596db682"
+checksum = "74212e6bbe9a4352329b2f68ba3130c15a3f26fe88ff22dbdc6cdd58fa85e99c"
 dependencies = [
  "serde",
 ]

Cargo.toml

@@ -77,6 +77,7 @@ vfs = { path = "./crates/vfs", version = "0.0.0" }
 
 # non-local crates
 smallvec = { version = "1.10.0", features = ["const_new", "union", "const_generics"] }
+smol_str = "0.2.0"
 # the following crates are pinned to prevent us from pulling in syn 2 until all our dependencies have moved
 serde = { version = "=1.0.156", features = ["derive"] }
 serde_json = "1.0.94"

crates/base-db/src/fixture.rs

@@ -4,7 +4,8 @@ use std::{mem, str::FromStr, sync::Arc};
 use cfg::CfgOptions;
 use rustc_hash::FxHashMap;
 use test_utils::{
-    extract_range_or_offset, Fixture, RangeOrOffset, CURSOR_MARKER, ESCAPED_CURSOR_MARKER,
+    extract_range_or_offset, Fixture, FixtureWithProjectMeta, RangeOrOffset, CURSOR_MARKER,
+    ESCAPED_CURSOR_MARKER,
 };
 use tt::token_id::{Leaf, Subtree, TokenTree};
 use vfs::{file_set::FileSet, VfsPath};
@@ -12,7 +13,7 @@ use vfs::{file_set::FileSet, VfsPath};
 use crate::{
     input::{CrateName, CrateOrigin, LangCrateOrigin},
     Change, CrateDisplayName, CrateGraph, CrateId, Dependency, Edition, Env, FileId, FilePosition,
-    FileRange, ProcMacro, ProcMacroExpander, ProcMacroExpansionError, ProcMacros,
+    FileRange, ProcMacro, ProcMacroExpander, ProcMacroExpansionError, ProcMacros, ReleaseChannel,
     SourceDatabaseExt, SourceRoot, SourceRootId,
 };
 
@@ -102,7 +103,14 @@ impl ChangeFixture {
         ra_fixture: &str,
         mut proc_macro_defs: Vec<(String, ProcMacro)>,
     ) -> ChangeFixture {
-        let (mini_core, proc_macro_names, fixture) = Fixture::parse(ra_fixture);
+        let FixtureWithProjectMeta { fixture, mini_core, proc_macro_names, toolchain } =
+            FixtureWithProjectMeta::parse(ra_fixture);
+        let toolchain = toolchain
+            .map(|it| {
+                ReleaseChannel::from_str(&it)
+                    .unwrap_or_else(|| panic!("unknown release channel found: {it}"))
+            })
+            .unwrap_or(ReleaseChannel::Stable);
         let mut change = Change::new();
 
         let mut files = Vec::new();
@@ -166,7 +174,7 @@ impl ChangeFixture {
                         .as_deref()
                         .map(Arc::from)
                         .ok_or_else(|| "target_data_layout unset".into()),
-                    None,
+                    Some(toolchain),
                 );
                 let prev = crates.insert(crate_name.clone(), crate_id);
                 assert!(prev.is_none());
@@ -205,7 +213,7 @@ impl ChangeFixture {
                 default_target_data_layout
                     .map(|x| x.into())
                     .ok_or_else(|| "target_data_layout unset".into()),
-                None,
+                Some(toolchain),
             );
         } else {
             for (from, to, prelude) in crate_deps {
@@ -247,7 +255,7 @@ impl ChangeFixture {
                 false,
                 CrateOrigin::Lang(LangCrateOrigin::Core),
                 target_layout.clone(),
-                None,
+                Some(toolchain),
             );
 
             for krate in all_crates {
@@ -286,7 +294,7 @@ impl ChangeFixture {
                 true,
                 CrateOrigin::Local { repo: None, name: None },
                 target_layout,
-                None,
+                Some(toolchain),
             );
             proc_macros.insert(proc_macros_crate, Ok(proc_macro));
 

crates/hir-def/src/attr.rs

@@ -1,5 +1,7 @@
 //! A higher level attributes based on TokenTree, with also some shortcuts.
 
+pub mod builtin;
+
 #[cfg(test)]
 mod tests;
 
@@ -267,6 +269,10 @@ impl Attrs {
     pub fn is_proc_macro_derive(&self) -> bool {
         self.by_key("proc_macro_derive").exists()
     }
+
+    pub fn is_unstable(&self) -> bool {
+        self.by_key("unstable").exists()
+    }
 }
 
 use std::slice::Iter as SliceIter;

crates/hir-def/src/body.rs

@@ -13,10 +13,12 @@ use cfg::{CfgExpr, CfgOptions};
 use drop_bomb::DropBomb;
 use either::Either;
 use hir_expand::{
-    attrs::RawAttrs, hygiene::Hygiene, ExpandError, ExpandResult, HirFileId, InFile, MacroCallId,
+    ast_id_map::AstIdMap, attrs::RawAttrs, hygiene::Hygiene, name::Name, AstId, ExpandError,
+    ExpandResult, HirFileId, InFile, MacroCallId,
 };
 use la_arena::{Arena, ArenaMap};
 use limit::Limit;
+use once_cell::unsync::OnceCell;
 use profile::Count;
 use rustc_hash::FxHashMap;
 use syntax::{ast, AstPtr, SyntaxNode, SyntaxNodePtr};
@@ -24,7 +26,7 @@ use syntax::{ast, AstPtr, SyntaxNode, SyntaxNodePtr};
 use crate::{
     attr::Attrs,
     db::DefDatabase,
-    expr::{
+    hir::{
         dummy_expr_id, Binding, BindingId, Expr, ExprId, Label, LabelId, Pat, PatId, RecordFieldPat,
     },
     item_scope::BuiltinShadowMode,
@@ -36,7 +38,43 @@ use crate::{
     UnresolvedMacro,
 };
 
-pub use lower::LowerCtx;
+pub struct LowerCtx<'a> {
+    pub db: &'a dyn DefDatabase,
+    hygiene: Hygiene,
+    ast_id_map: Option<(HirFileId, OnceCell<Arc<AstIdMap>>)>,
+}
+
+impl<'a> LowerCtx<'a> {
+    pub fn new(db: &'a dyn DefDatabase, hygiene: &Hygiene, file_id: HirFileId) -> Self {
+        LowerCtx { db, hygiene: hygiene.clone(), ast_id_map: Some((file_id, OnceCell::new())) }
+    }
+
+    pub fn with_file_id(db: &'a dyn DefDatabase, file_id: HirFileId) -> Self {
+        LowerCtx {
+            db,
+            hygiene: Hygiene::new(db.upcast(), file_id),
+            ast_id_map: Some((file_id, OnceCell::new())),
+        }
+    }
+
+    pub fn with_hygiene(db: &'a dyn DefDatabase, hygiene: &Hygiene) -> Self {
+        LowerCtx { db, hygiene: hygiene.clone(), ast_id_map: None }
+    }
+
+    pub(crate) fn hygiene(&self) -> &Hygiene {
+        &self.hygiene
+    }
+
+    pub(crate) fn lower_path(&self, ast: ast::Path) -> Option<Path> {
+        Path::from_src(ast, self)
+    }
+
+    pub(crate) fn ast_id<N: syntax::AstNode>(&self, item: &N) -> Option<AstId<N>> {
+        let &(file_id, ref ast_id_map) = self.ast_id_map.as_ref()?;
+        let ast_id_map = ast_id_map.get_or_init(|| self.db.ast_id_map(file_id));
+        Some(InFile::new(file_id, ast_id_map.ast_id(item)))
+    }
+}
 
 /// A subset of Expander that only deals with cfg attributes. We only need it to
 /// avoid cyclic queries in crate def map during enum processing.
@@ -76,6 +114,10 @@ impl CfgExpander {
         let attrs = self.parse_attrs(db, owner);
         attrs.is_cfg_enabled(&self.cfg_options)
     }
+
+    pub(crate) fn hygiene(&self) -> &Hygiene {
+        &self.hygiene
+    }
 }
 
 impl Expander {
@@ -180,6 +222,10 @@ impl Expander {
         mark.bomb.defuse();
     }
 
+    pub fn ctx<'a>(&self, db: &'a dyn DefDatabase) -> LowerCtx<'a> {
+        LowerCtx::new(db, &self.cfg_expander.hygiene, self.current_file_id)
+    }
+
     pub(crate) fn to_source<T>(&self, value: T) -> InFile<T> {
         InFile { file_id: self.current_file_id, value }
     }
@@ -232,7 +278,7 @@ impl Expander {
             // The overflow error should have been reported when it occurred (see the next branch),
             // so don't return overflow error here to avoid diagnostics duplication.
             cov_mark::hit!(overflow_but_not_me);
-            return ExpandResult::only_err(ExpandError::RecursionOverflowPosioned);
+            return ExpandResult::only_err(ExpandError::RecursionOverflowPoisoned);
         } else if self.recursion_limit(db).check(self.recursion_depth + 1).is_err() {
             self.recursion_depth = usize::MAX;
             cov_mark::hit!(your_stack_belongs_to_me);
@@ -343,6 +389,8 @@ pub enum BodyDiagnostic {
     MacroError { node: InFile<AstPtr<ast::MacroCall>>, message: String },
     UnresolvedProcMacro { node: InFile<AstPtr<ast::MacroCall>>, krate: CrateId },
     UnresolvedMacroCall { node: InFile<AstPtr<ast::MacroCall>>, path: ModPath },
+    UnreachableLabel { node: InFile<AstPtr<ast::Lifetime>>, name: Name },
+    UndeclaredLabel { node: InFile<AstPtr<ast::Lifetime>>, name: Name },
 }
 
 impl Body {

crates/hir-def/src/body/lower.rs

@@ -7,77 +7,38 @@ use base_db::CrateId;
 use either::Either;
 use hir_expand::{
     ast_id_map::AstIdMap,
-    hygiene::Hygiene,
     name::{name, AsName, Name},
-    AstId, ExpandError, HirFileId, InFile,
+    AstId, ExpandError, InFile,
 };
 use intern::Interned;
 use la_arena::Arena;
-use once_cell::unsync::OnceCell;
 use profile::Count;
 use rustc_hash::FxHashMap;
 use smallvec::SmallVec;
 use syntax::{
     ast::{
-        self, ArrayExprKind, AstChildren, BlockExpr, HasArgList, HasLoopBody, HasName, LiteralKind,
+        self, ArrayExprKind, AstChildren, BlockExpr, HasArgList, HasLoopBody, HasName,
         SlicePatComponents,
     },
     AstNode, AstPtr, SyntaxNodePtr,
 };
 
 use crate::{
-    adt::StructKind,
-    body::{Body, BodySourceMap, Expander, ExprPtr, LabelPtr, LabelSource, PatPtr},
-    body::{BodyDiagnostic, ExprSource, PatSource},
-    builtin_type::{BuiltinFloat, BuiltinInt, BuiltinUint},
+    body::{Body, BodyDiagnostic, BodySourceMap, Expander, ExprPtr, LabelPtr, LowerCtx, PatPtr},
+    data::adt::StructKind,
     db::DefDatabase,
-    expr::{
-        dummy_expr_id, Array, Binding, BindingAnnotation, BindingId, ClosureKind, Expr, ExprId,
-        FloatTypeWrapper, Label, LabelId, Literal, MatchArm, Movability, Pat, PatId,
-        RecordFieldPat, RecordLitField, Statement,
+    hir::{
+        dummy_expr_id, Array, Binding, BindingAnnotation, BindingId, CaptureBy, ClosureKind, Expr,
+        ExprId, Label, LabelId, Literal, MatchArm, Movability, Pat, PatId, RecordFieldPat,
+        RecordLitField, Statement,
     },
     item_scope::BuiltinShadowMode,
-    item_tree::ItemTree,
     lang_item::LangItem,
     path::{GenericArgs, Path},
     type_ref::{Mutability, Rawness, TypeRef},
     AdtId, BlockId, BlockLoc, ModuleDefId, UnresolvedMacro,
 };
 
-pub struct LowerCtx<'a> {
-    pub db: &'a dyn DefDatabase,
-    hygiene: Hygiene,
-    ast_id_map: Option<(HirFileId, OnceCell<Arc<AstIdMap>>)>,
-}
-
-impl<'a> LowerCtx<'a> {
-    pub fn new(db: &'a dyn DefDatabase, file_id: HirFileId) -> Self {
-        LowerCtx {
-            db,
-            hygiene: Hygiene::new(db.upcast(), file_id),
-            ast_id_map: Some((file_id, OnceCell::new())),
-        }
-    }
-
-    pub fn with_hygiene(db: &'a dyn DefDatabase, hygiene: &Hygiene) -> Self {
-        LowerCtx { db, hygiene: hygiene.clone(), ast_id_map: None }
-    }
-
-    pub(crate) fn hygiene(&self) -> &Hygiene {
-        &self.hygiene
-    }
-
-    pub(crate) fn lower_path(&self, ast: ast::Path) -> Option<Path> {
-        Path::from_src(ast, self)
-    }
-
-    pub(crate) fn ast_id<N: AstNode>(&self, item: &N) -> Option<AstId<N>> {
-        let &(file_id, ref ast_id_map) = self.ast_id_map.as_ref()?;
-        let ast_id_map = ast_id_map.get_or_init(|| self.db.ast_id_map(file_id));
-        Some(InFile::new(file_id, ast_id_map.ast_id(item)))
-    }
-}
-
 pub(super) fn lower(
     db: &dyn DefDatabase,
     expander: Expander,
@@ -102,9 +63,11 @@ pub(super) fn lower(
             _c: Count::new(),
         },
         expander,
-        current_try_block: None,
+        current_try_block_label: None,
         is_lowering_assignee_expr: false,
         is_lowering_generator: false,
+        label_ribs: Vec::new(),
+        current_binding_owner: None,
     }
     .collect(params, body, is_async_fn)
 }
@@ -113,12 +76,57 @@ struct ExprCollector<'a> {
     db: &'a dyn DefDatabase,
     expander: Expander,
     ast_id_map: Arc<AstIdMap>,
-    body: Body,
     krate: CrateId,
+    body: Body,
     source_map: BodySourceMap,
-    current_try_block: Option<LabelId>,
+
     is_lowering_assignee_expr: bool,
     is_lowering_generator: bool,
+
+    current_try_block_label: Option<LabelId>,
+    // points to the expression that a try expression will target (replaces current_try_block_label)
+    // catch_scope: Option<ExprId>,
+    // points to the expression that an unlabeled control flow will target
+    // loop_scope: Option<ExprId>,
+    // needed to diagnose non label control flow in while conditions
+    // is_in_loop_condition: bool,
+
+    // resolution
+    label_ribs: Vec<LabelRib>,
+    current_binding_owner: Option<ExprId>,
+}
+
+#[derive(Clone, Debug)]
+struct LabelRib {
+    kind: RibKind,
+    // Once we handle macro hygiene this will need to be a map
+    label: Option<(Name, LabelId)>,
+}
+
+impl LabelRib {
+    fn new(kind: RibKind) -> Self {
+        LabelRib { kind, label: None }
+    }
+    fn new_normal(label: (Name, LabelId)) -> Self {
+        LabelRib { kind: RibKind::Normal, label: Some(label) }
+    }
+}
+
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+enum RibKind {
+    Normal,
+    Closure,
+    Constant,
+}
+
+impl RibKind {
+    /// This rib forbids referring to labels defined in upwards ribs.
+    fn is_label_barrier(self) -> bool {
+        match self {
+            RibKind::Normal => false,
+            RibKind::Closure | RibKind::Constant => true,
+        }
+    }
 }
 
 #[derive(Debug, Default)]
@@ -162,97 +170,35 @@ impl ExprCollector<'_> {
                 self.body.params.push(param_pat);
             }
 
-            for pat in param_list
-                .params()
-                .zip(attr_enabled)
-                .filter_map(|(param, enabled)| param.pat().filter(|_| enabled))
+            for (param, _) in param_list.params().zip(attr_enabled).filter(|(_, enabled)| *enabled)
             {
-                let param_pat = self.collect_pat(pat);
+                let param_pat = self.collect_pat_top(param.pat());
                 self.body.params.push(param_pat);
             }
         };
+        self.body.body_expr = self.with_label_rib(RibKind::Closure, |this| {
+            if is_async_fn {
+                match body {
+                    Some(e) => {
+                        let expr = this.collect_expr(e);
+                        this.alloc_expr_desugared(Expr::Async {
+                            id: None,
+                            statements: Box::new([]),
+                            tail: Some(expr),
+                        })
+                    }
+                    None => this.missing_expr(),
+                }
+            } else {
+                this.collect_expr_opt(body)
+            }
+        });
 
-        self.body.body_expr = if is_async_fn {
-            self.current_try_block =
-                Some(self.alloc_label_desugared(Label { name: Name::generate_new_name() }));
-            let expr = self.collect_expr_opt(body);
-            let expr = self.alloc_expr_desugared(Expr::Block {
-                id: None,
-                statements: Box::new([]),
-                tail: Some(expr),
-                label: self.current_try_block,
-            });
-            let expr = self.alloc_expr_desugared(Expr::Async {
-                id: None,
-                statements: Box::new([]),
-                tail: Some(expr),
-            });
-            expr
-        } else {
-            self.collect_expr_opt(body)
-        };
         (self.body, self.source_map)
     }
 
     fn ctx(&self) -> LowerCtx<'_> {
-        LowerCtx::new(self.db, self.expander.current_file_id)
-    }
-
-    fn alloc_expr(&mut self, expr: Expr, ptr: ExprPtr) -> ExprId {
-        let src = self.expander.to_source(ptr);
-        let id = self.make_expr(expr, src.clone());
-        self.source_map.expr_map.insert(src, id);
-        id
-    }
-    // FIXME: desugared exprs don't have ptr, that's wrong and should be fixed somehow.
-    fn alloc_expr_desugared(&mut self, expr: Expr) -> ExprId {
-        self.body.exprs.alloc(expr)
-    }
-    fn missing_expr(&mut self) -> ExprId {
-        self.alloc_expr_desugared(Expr::Missing)
-    }
-    fn make_expr(&mut self, expr: Expr, src: ExprSource) -> ExprId {
-        let id = self.body.exprs.alloc(expr);
-        self.source_map.expr_map_back.insert(id, src);
-        id
-    }
-
-    fn alloc_binding(&mut self, name: Name, mode: BindingAnnotation) -> BindingId {
-        self.body.bindings.alloc(Binding { name, mode, definitions: SmallVec::new() })
-    }
-    fn alloc_pat(&mut self, pat: Pat, ptr: PatPtr) -> PatId {
-        let src = self.expander.to_source(ptr);
-        let id = self.make_pat(pat, src.clone());
-        self.source_map.pat_map.insert(src, id);
-        id
-    }
-    // FIXME: desugared pats don't have ptr, that's wrong and should be fixed somehow.
-    fn alloc_pat_desugared(&mut self, pat: Pat) -> PatId {
-        self.body.pats.alloc(pat)
-    }
-    fn missing_pat(&mut self) -> PatId {
-        self.body.pats.alloc(Pat::Missing)
-    }
-    fn make_pat(&mut self, pat: Pat, src: PatSource) -> PatId {
-        let id = self.body.pats.alloc(pat);
-        self.source_map.pat_map_back.insert(id, src);
-        id
-    }
-
-    fn alloc_label(&mut self, label: Label, ptr: LabelPtr) -> LabelId {
-        let src = self.expander.to_source(ptr);
-        let id = self.make_label(label, src.clone());
-        self.source_map.label_map.insert(src, id);
-        id
-    }
-    // FIXME: desugared labels don't have ptr, that's wrong and should be fixed somehow.
-    fn alloc_label_desugared(&mut self, label: Label) -> LabelId {
-        self.body.labels.alloc(label)
-    }
-    fn make_label(&mut self, label: Label, src: LabelSource) -> LabelId {
-        let id = self.body.labels.alloc(label);
-        self.source_map.label_map_back.insert(id, src);
-        id
+        self.expander.ctx(self.db)
     }
 
     fn collect_expr(&mut self, expr: ast::Expr) -> ExprId {
@@ -264,6 +210,7 @@ impl ExprCollector<'_> {
         let syntax_ptr = AstPtr::new(&expr);
         self.check_cfg(&expr)?;
 
+        // FIXME: Move some of these arms out into separate methods for clarity
         Some(match expr {
             ast::Expr::IfExpr(e) => {
                 let then_branch = self.collect_block_opt(e.then_branch());
@@ -281,12 +228,12 @@ impl ExprCollector<'_> {
                 self.alloc_expr(Expr::If { condition, then_branch, else_branch }, syntax_ptr)
             }
             ast::Expr::LetExpr(e) => {
-                let pat = self.collect_pat_opt(e.pat());
+                let pat = self.collect_pat_top(e.pat());
                 let expr = self.collect_expr_opt(e.expr());
                 self.alloc_expr(Expr::Let { pat, expr }, syntax_ptr)
             }
             ast::Expr::BlockExpr(e) => match e.modifier() {
-                Some(ast::BlockModifier::Try(_)) => self.collect_try_block(e),
+                Some(ast::BlockModifier::Try(_)) => self.desugar_try_block(e),
                 Some(ast::BlockModifier::Unsafe(_)) => {
                     self.collect_block_(e, |id, statements, tail| Expr::Unsafe {
                         id,
@@ -296,28 +243,48 @@ impl ExprCollector<'_> {
                 }
                 Some(ast::BlockModifier::Label(label)) => {
                     let label = self.collect_label(label);
-                    self.collect_block_(e, |id, statements, tail| Expr::Block {
-                        id,
-                        statements,
-                        tail,
-                        label: Some(label),
+                    self.with_labeled_rib(label, |this| {
+                        this.collect_block_(e, |id, statements, tail| Expr::Block {
+                            id,
+                            statements,
+                            tail,
+                            label: Some(label),
+                        })
+                    })
+                }
+                Some(ast::BlockModifier::Async(_)) => {
+                    self.with_label_rib(RibKind::Closure, |this| {
+                        this.collect_block_(e, |id, statements, tail| Expr::Async {
+                            id,
+                            statements,
+                            tail,
+                        })
+                    })
+                }
+                Some(ast::BlockModifier::Const(_)) => {
+                    self.with_label_rib(RibKind::Constant, |this| {
+                        this.collect_as_a_binding_owner_bad(
+                            |this| {
+                                this.collect_block_(e, |id, statements, tail| Expr::Const {
+                                    id,
+                                    statements,
+                                    tail,
+                                })
+                            },
+                            syntax_ptr,
+                        )
                     })
                 }
-                Some(ast::BlockModifier::Async(_)) => self
-                    .collect_block_(e, |id, statements, tail| Expr::Async { id, statements, tail }),
-                Some(ast::BlockModifier::Const(_)) => self
-                    .collect_block_(e, |id, statements, tail| Expr::Const { id, statements, tail }),
                 None => self.collect_block(e),
             },
             ast::Expr::LoopExpr(e) => {
                 let label = e.label().map(|label| self.collect_label(label));
-                let body = self.collect_block_opt(e.loop_body());
+                let body = self.collect_labelled_block_opt(label, e.loop_body());
                 self.alloc_expr(Expr::Loop { body, label }, syntax_ptr)
             }
             ast::Expr::WhileExpr(e) => {
                 let label = e.label().map(|label| self.collect_label(label));
-                let body = self.collect_block_opt(e.loop_body());
-
+                let body = self.collect_labelled_block_opt(label, e.loop_body());
                 let condition = self.collect_expr_opt(e.condition());
 
                 self.alloc_expr(Expr::While { condition, body, label }, syntax_ptr)
@@ -325,8 +292,8 @@ impl ExprCollector<'_> {
             ast::Expr::ForExpr(e) => {
                 let label = e.label().map(|label| self.collect_label(label));
                 let iterable = self.collect_expr_opt(e.iterable());
-                let pat = self.collect_pat_opt(e.pat());
-                let body = self.collect_block_opt(e.loop_body());
+                let pat = self.collect_pat_top(e.pat());
+                let body = self.collect_labelled_block_opt(label, e.loop_body());
                 self.alloc_expr(Expr::For { iterable, pat, body, label }, syntax_ptr)
             }
             ast::Expr::CallExpr(e) => {
@@ -365,7 +332,7 @@ impl ExprCollector<'_> {
                         .arms()
                         .filter_map(|arm| {
                             self.check_cfg(&arm).map(|()| MatchArm {
-                                pat: self.collect_pat_opt(arm.pat()),
+                                pat: self.collect_pat_top(arm.pat()),
                                 expr: self.collect_expr_opt(arm.expr()),
                                 guard: arm
                                     .guard()
@@ -386,16 +353,20 @@ impl ExprCollector<'_> {
                     .unwrap_or(Expr::Missing);
                 self.alloc_expr(path, syntax_ptr)
             }
-            ast::Expr::ContinueExpr(e) => self.alloc_expr(
-                Expr::Continue { label: e.lifetime().map(|l| Name::new_lifetime(&l)) },
-                syntax_ptr,
-            ),
+            ast::Expr::ContinueExpr(e) => {
+                let label = self.resolve_label(e.lifetime()).unwrap_or_else(|e| {
+                    self.source_map.diagnostics.push(e);
+                    None
+                });
+                self.alloc_expr(Expr::Continue { label }, syntax_ptr)
+            }
             ast::Expr::BreakExpr(e) => {
+                let label = self.resolve_label(e.lifetime()).unwrap_or_else(|e| {
+                    self.source_map.diagnostics.push(e);
+                    None
+                });
                 let expr = e.expr().map(|e| self.collect_expr(e));
-                self.alloc_expr(
-                    Expr::Break { expr, label: e.lifetime().map(|l| Name::new_lifetime(&l)) },
-                    syntax_ptr,
-                )
+                self.alloc_expr(Expr::Break { expr, label }, syntax_ptr)
             }
             ast::Expr::ParenExpr(e) => {
                 let inner = self.collect_expr_opt(e.expr());
@@ -496,14 +467,16 @@ impl ExprCollector<'_> {
                     None => self.alloc_expr(Expr::Missing, syntax_ptr),
                 }
             }
-            ast::Expr::ClosureExpr(e) => {
+            ast::Expr::ClosureExpr(e) => self.with_label_rib(RibKind::Closure, |this| {
+                let (result_expr_id, prev_binding_owner) =
+                    this.initialize_binding_owner(syntax_ptr);
                 let mut args = Vec::new();
                 let mut arg_types = Vec::new();
                 if let Some(pl) = e.param_list() {
                     for param in pl.params() {
-                        let pat = self.collect_pat_opt(param.pat());
+                        let pat = this.collect_pat_top(param.pat());
                         let type_ref =
-                            param.ty().map(|it| Interned::new(TypeRef::from_ast(&self.ctx(), it)));
+                            param.ty().map(|it| Interned::new(TypeRef::from_ast(&this.ctx(), it)));
                         args.push(pat);
                         arg_types.push(type_ref);
                     }
@@ -511,14 +484,13 @@ impl ExprCollector<'_> {
                 let ret_type = e
                     .ret_type()
                     .and_then(|r| r.ty())
-                    .map(|it| Interned::new(TypeRef::from_ast(&self.ctx(), it)));
+                    .map(|it| Interned::new(TypeRef::from_ast(&this.ctx(), it)));
 
-                let prev_is_lowering_generator = self.is_lowering_generator;
-                self.is_lowering_generator = false;
+                let prev_is_lowering_generator = mem::take(&mut this.is_lowering_generator);
 
-                let body = self.collect_expr_opt(e.body());
+                let body = this.collect_expr_opt(e.body());
 
-                let closure_kind = if self.is_lowering_generator {
+                let closure_kind = if this.is_lowering_generator {
                     let movability = if e.static_token().is_some() {
                         Movability::Static
                     } else {
@@ -530,19 +502,21 @@ impl ExprCollector<'_> {
                 } else {
                     ClosureKind::Closure
                 };
-                self.is_lowering_generator = prev_is_lowering_generator;
-
-                self.alloc_expr(
-                    Expr::Closure {
-                        args: args.into(),
-                        arg_types: arg_types.into(),
-                        ret_type,
-                        body,
-                        closure_kind,
-                    },
-                    syntax_ptr,
-                )
-            }
+                this.is_lowering_generator = prev_is_lowering_generator;
+                let capture_by =
+                    if e.move_token().is_some() { CaptureBy::Value } else { CaptureBy::Ref };
+                this.is_lowering_generator = prev_is_lowering_generator;
+                this.current_binding_owner = prev_binding_owner;
+                this.body.exprs[result_expr_id] = Expr::Closure {
+                    args: args.into(),
+                    arg_types: arg_types.into(),
+                    ret_type,
+                    body,
+                    closure_kind,
+                    capture_by,
+                };
+                result_expr_id
+            }),
             ast::Expr::BinExpr(e) => {
                 let op = e.op_kind();
                 if let Some(ast::BinaryOp::Assignment { op: None }) = op {
@@ -581,7 +555,17 @@ impl ExprCollector<'_> {
                     }
                     ArrayExprKind::Repeat { initializer, repeat } => {
                         let initializer = self.collect_expr_opt(initializer);
-                        let repeat = self.collect_expr_opt(repeat);
+                        let repeat = self.with_label_rib(RibKind::Constant, |this| {
+                            if let Some(repeat) = repeat {
+                                let syntax_ptr = AstPtr::new(&repeat);
+                                this.collect_as_a_binding_owner_bad(
+                                    |this| this.collect_expr(repeat),
+                                    syntax_ptr,
+                                )
+                            } else {
+                                this.missing_expr()
+                            }
+                        });
                         self.alloc_expr(
                             Expr::Array(Array::Repeat { initializer, repeat }),
                             syntax_ptr,
@@ -627,23 +611,53 @@ impl ExprCollector<'_> {
         })
     }
 
+    fn initialize_binding_owner(
+        &mut self,
+        syntax_ptr: AstPtr<ast::Expr>,
+    ) -> (ExprId, Option<ExprId>) {
+        let result_expr_id = self.alloc_expr(Expr::Missing, syntax_ptr);
+        let prev_binding_owner = self.current_binding_owner.take();
+        self.current_binding_owner = Some(result_expr_id);
+        (result_expr_id, prev_binding_owner)
+    }
+
+    /// FIXME: This function is bad. It will produce a dangling `Missing` expr which wastes memory. Currently
+    /// it is used only for const blocks and repeat expressions, which are also hacky and ideally should have
+    /// their own body. Don't add more usage for this function so that we can remove this function after
+    /// separating those bodies.
+    fn collect_as_a_binding_owner_bad(
+        &mut self,
+        job: impl FnOnce(&mut ExprCollector<'_>) -> ExprId,
+        syntax_ptr: AstPtr<ast::Expr>,
+    ) -> ExprId {
+        let (id, prev_owner) = self.initialize_binding_owner(syntax_ptr);
+        let tmp = job(self);
+        self.body.exprs[id] = mem::replace(&mut self.body.exprs[tmp], Expr::Missing);
+        self.current_binding_owner = prev_owner;
+        id
+    }
+
     /// Desugar `try { <stmts>; <expr> }` into `'<new_label>: { <stmts>; ::std::ops::Try::from_output(<expr>) }`,
     /// `try { <stmts>; }` into `'<new_label>: { <stmts>; ::std::ops::Try::from_output(()) }`
     /// and save the `<new_label>` to use it as a break target for desugaring of the `?` operator.
-    fn collect_try_block(&mut self, e: BlockExpr) -> ExprId {
+    fn desugar_try_block(&mut self, e: BlockExpr) -> ExprId {
         let Some(try_from_output) = LangItem::TryTraitFromOutput.path(self.db, self.krate) else {
-            return self.alloc_expr_desugared(Expr::Missing);
+            return self.collect_block(e);
         };
-        let prev_try_block = self.current_try_block.take();
-        self.current_try_block =
-            Some(self.alloc_label_desugared(Label { name: Name::generate_new_name() }));
-        let expr_id = self.collect_block(e);
+        let label = self.alloc_label_desugared(Label { name: Name::generate_new_name() });
+        let old_label = self.current_try_block_label.replace(label);
+
+        let (btail, expr_id) = self.with_labeled_rib(label, |this| {
+            let mut btail = None;
+            let block = this.collect_block_(e, |id, statements, tail| {
+                btail = tail;
+                Expr::Block { id, statements, tail, label: Some(label) }
+            });
+            (btail, block)
+        });
+
         let callee = self.alloc_expr_desugared(Expr::Path(try_from_output));
-        let Expr::Block { label, tail, .. } = &mut self.body.exprs[expr_id] else {
-            unreachable!("It is the output of collect block");
-        };
-        *label = self.current_try_block;
-        let next_tail = match *tail {
+        let next_tail = match btail {
             Some(tail) => self.alloc_expr_desugared(Expr::Call {
                 callee,
                 args: Box::new([tail]),
@@ -662,10 +676,10 @@ impl ExprCollector<'_> {
             }
         };
         let Expr::Block { tail, .. } = &mut self.body.exprs[expr_id] else {
-            unreachable!("It is the output of collect block");
+            unreachable!("block was lowered to non-block");
         };
         *tail = Some(next_tail);
-        self.current_try_block = prev_try_block;
+        self.current_try_block_label = old_label;
         expr_id
     }
 
@@ -735,12 +749,13 @@ impl ExprCollector<'_> {
                     Expr::Call { callee, args: Box::new([x]), is_assignee_expr: false },
                     syntax_ptr.clone(),
                 );
-                if let Some(label) = self.current_try_block {
-                    let label = Some(self.body.labels[label].name.clone());
-                    self.alloc_expr(Expr::Break { expr: Some(result), label }, syntax_ptr.clone())
-                } else {
-                    self.alloc_expr(Expr::Return { expr: Some(result) }, syntax_ptr.clone())
-                }
+                self.alloc_expr(
+                    match self.current_try_block_label {
+                        Some(label) => Expr::Break { expr: Some(result), label: Some(label) },
+                        None => Expr::Return { expr: Some(result) },
+                    },
+                    syntax_ptr.clone(),
+                )
             },
         };
         let arms = Box::new([continue_arm, break_arm]);
@@ -785,7 +800,7 @@ impl ExprCollector<'_> {
                         krate: *krate,
                     });
                 }
-                Some(ExpandError::RecursionOverflowPosioned) => {
+                Some(ExpandError::RecursionOverflowPoisoned) => {
                     // Recursion limit has been reached in the macro expansion tree, but not in
                     // this very macro call. Don't add diagnostics to avoid duplication.
                 }
@@ -866,7 +881,7 @@ impl ExprCollector<'_> {
                 if self.check_cfg(&stmt).is_none() {
                     return;
                 }
-                let pat = self.collect_pat_opt(stmt.pat());
+                let pat = self.collect_pat_top(stmt.pat());
                 let type_ref =
                     stmt.ty().map(|it| Interned::new(TypeRef::from_ast(&self.ctx(), it)));
                 let initializer = stmt.initializer().map(|e| self.collect_expr(e));
@@ -911,10 +926,20 @@ impl ExprCollector<'_> {
         block: ast::BlockExpr,
         mk_block: impl FnOnce(Option<BlockId>, Box<[Statement]>, Option<ExprId>) -> Expr,
     ) -> ExprId {
-        let file_local_id = self.ast_id_map.ast_id(&block);
-        let ast_id = AstId::new(self.expander.current_file_id, file_local_id);
+        let block_has_items = {
+            let statement_has_item = block.statements().any(|stmt| match stmt {
+                ast::Stmt::Item(_) => true,
+                // Macro calls can be both items and expressions. The syntax library always treats
+                // them as expressions here, so we undo that.
+                ast::Stmt::ExprStmt(es) => matches!(es.expr(), Some(ast::Expr::MacroExpr(_))),
+                _ => false,
+            });
+            statement_has_item || matches!(block.tail_expr(), Some(ast::Expr::MacroExpr(_)))
+        };
 
-        let block_id = if ItemTree::block_has_items(self.db, ast_id.file_id, &block) {
+        let block_id = if block_has_items {
+            let file_local_id = self.ast_id_map.ast_id(&block);
+            let ast_id = AstId::new(self.expander.current_file_id, file_local_id);
             Some(self.db.intern_block(BlockLoc {
                 ast_id,
                 module: self.expander.def_map.module_id(self.expander.module),
@@ -966,32 +991,34 @@ impl ExprCollector<'_> {
         }
     }
 
-    fn collect_label(&mut self, ast_label: ast::Label) -> LabelId {
-        let label = Label {
-            name: ast_label.lifetime().as_ref().map_or_else(Name::missing, Name::new_lifetime),
-        };
-        self.alloc_label(label, AstPtr::new(&ast_label))
+    fn collect_labelled_block_opt(
+        &mut self,
+        label: Option<LabelId>,
+        expr: Option<ast::BlockExpr>,
+    ) -> ExprId {
+        match label {
+            Some(label) => self.with_labeled_rib(label, |this| this.collect_block_opt(expr)),
+            None => self.collect_block_opt(expr),
+        }
     }
 
-    fn collect_pat(&mut self, pat: ast::Pat) -> PatId {
-        self.collect_pat_(pat, &mut BindingList::default())
-    }
+    // region: patterns
 
-    fn collect_pat_opt(&mut self, pat: Option<ast::Pat>) -> PatId {
+    fn collect_pat_top(&mut self, pat: Option<ast::Pat>) -> PatId {
         match pat {
-            Some(pat) => self.collect_pat(pat),
+            Some(pat) => self.collect_pat(pat, &mut BindingList::default()),
             None => self.missing_pat(),
         }
     }
 
-    fn collect_pat_(&mut self, pat: ast::Pat, binding_list: &mut BindingList) -> PatId {
+    fn collect_pat(&mut self, pat: ast::Pat, binding_list: &mut BindingList) -> PatId {
         let pattern = match &pat {
             ast::Pat::IdentPat(bp) => {
                 let name = bp.name().map(|nr| nr.as_name()).unwrap_or_else(Name::missing);
 
                 let annotation =
                     BindingAnnotation::new(bp.mut_token().is_some(), bp.ref_token().is_some());
-                let subpat = bp.pat().map(|subpat| self.collect_pat_(subpat, binding_list));
+                let subpat = bp.pat().map(|subpat| self.collect_pat(subpat, binding_list));
 
                 let is_simple_ident_pat =
                     annotation == BindingAnnotation::Unannotated && subpat.is_none();
@@ -1045,7 +1072,7 @@ impl ExprCollector<'_> {
                 Pat::TupleStruct { path, args, ellipsis }
             }
             ast::Pat::RefPat(p) => {
-                let pat = self.collect_pat_opt_(p.pat(), binding_list);
+                let pat = self.collect_pat_opt(p.pat(), binding_list);
                 let mutability = Mutability::from_mutable(p.mut_token().is_some());
                 Pat::Ref { pat, mutability }
             }
@@ -1055,10 +1082,10 @@ impl ExprCollector<'_> {
                 path.map(Pat::Path).unwrap_or(Pat::Missing)
             }
             ast::Pat::OrPat(p) => {
-                let pats = p.pats().map(|p| self.collect_pat_(p, binding_list)).collect();
+                let pats = p.pats().map(|p| self.collect_pat(p, binding_list)).collect();
                 Pat::Or(pats)
             }
-            ast::Pat::ParenPat(p) => return self.collect_pat_opt_(p.pat(), binding_list),
+            ast::Pat::ParenPat(p) => return self.collect_pat_opt(p.pat(), binding_list),
             ast::Pat::TuplePat(p) => {
                 let (args, ellipsis) = self.collect_tuple_pat(p.fields(), binding_list);
                 Pat::Tuple { args, ellipsis }
@@ -1073,7 +1100,7 @@ impl ExprCollector<'_> {
                     .fields()
                     .filter_map(|f| {
                         let ast_pat = f.pat()?;
-                        let pat = self.collect_pat_(ast_pat, binding_list);
+                        let pat = self.collect_pat(ast_pat, binding_list);
                         let name = f.field_name()?.as_name();
                         Some(RecordFieldPat { name, pat })
                     })
@@ -1092,15 +1119,9 @@ impl ExprCollector<'_> {
 
                 // FIXME properly handle `RestPat`
                 Pat::Slice {
-                    prefix: prefix
-                        .into_iter()
-                        .map(|p| self.collect_pat_(p, binding_list))
-                        .collect(),
-                    slice: slice.map(|p| self.collect_pat_(p, binding_list)),
-                    suffix: suffix
-                        .into_iter()
-                        .map(|p| self.collect_pat_(p, binding_list))
-                        .collect(),
+                    prefix: prefix.into_iter().map(|p| self.collect_pat(p, binding_list)).collect(),
+                    slice: slice.map(|p| self.collect_pat(p, binding_list)),
+                    suffix: suffix.into_iter().map(|p| self.collect_pat(p, binding_list)).collect(),
                 }
             }
             #[rustfmt::skip] // https://github.com/rust-lang/rustfmt/issues/5676
@@ -1131,12 +1152,18 @@ impl ExprCollector<'_> {
                 Pat::Missing
             }
             ast::Pat::BoxPat(boxpat) => {
-                let inner = self.collect_pat_opt_(boxpat.pat(), binding_list);
+                let inner = self.collect_pat_opt(boxpat.pat(), binding_list);
                 Pat::Box { inner }
             }
             ast::Pat::ConstBlockPat(const_block_pat) => {
-                if let Some(expr) = const_block_pat.block_expr() {
-                    let expr_id = self.collect_block(expr);
+                if let Some(block) = const_block_pat.block_expr() {
+                    let expr_id = self.with_label_rib(RibKind::Constant, |this| {
+                        let syntax_ptr = AstPtr::new(&block.clone().into());
+                        this.collect_as_a_binding_owner_bad(
+                            |this| this.collect_block(block),
+                            syntax_ptr,
+                        )
+                    });
                     Pat::ConstBlock(expr_id)
                 } else {
                     Pat::Missing
@@ -1148,7 +1175,7 @@ impl ExprCollector<'_> {
                     let src = self.expander.to_source(Either::Left(AstPtr::new(&pat)));
                     let pat =
                         self.collect_macro_call(call, macro_ptr, true, |this, expanded_pat| {
-                            this.collect_pat_opt_(expanded_pat, binding_list)
+                            this.collect_pat_opt(expanded_pat, binding_list)
                         });
                     self.source_map.pat_map.insert(src, pat);
                     return pat;
@@ -1162,9 +1189,9 @@ impl ExprCollector<'_> {
         self.alloc_pat(pattern, Either::Left(ptr))
     }
 
-    fn collect_pat_opt_(&mut self, pat: Option<ast::Pat>, binding_list: &mut BindingList) -> PatId {
+    fn collect_pat_opt(&mut self, pat: Option<ast::Pat>, binding_list: &mut BindingList) -> PatId {
         match pat {
-            Some(pat) => self.collect_pat_(pat, binding_list),
+            Some(pat) => self.collect_pat(pat, binding_list),
             None => self.missing_pat(),
         }
     }
@@ -1180,12 +1207,14 @@ impl ExprCollector<'_> {
         // We want to skip the `..` pattern here, since we account for it above.
         let args = args
             .filter(|p| !matches!(p, ast::Pat::RestPat(_)))
-            .map(|p| self.collect_pat_(p, binding_list))
+            .map(|p| self.collect_pat(p, binding_list))
             .collect();
 
         (args, ellipsis)
     }
 
+    // endregion: patterns
+
     /// Returns `None` (and emits diagnostics) when `owner` if `#[cfg]`d out, and `Some(())` when
     /// not.
     fn check_cfg(&mut self, owner: &dyn ast::HasAttrs) -> Option<()> {
@@ -1213,42 +1242,118 @@ impl ExprCollector<'_> {
     fn add_definition_to_binding(&mut self, binding_id: BindingId, pat_id: PatId) {
         self.body.bindings[binding_id].definitions.push(pat_id);
     }
-}
 
-impl From<ast::LiteralKind> for Literal {
-    fn from(ast_lit_kind: ast::LiteralKind) -> Self {
-        match ast_lit_kind {
-            // FIXME: these should have actual values filled in, but unsure on perf impact
-            LiteralKind::IntNumber(lit) => {
-                if let builtin @ Some(_) = lit.suffix().and_then(BuiltinFloat::from_suffix) {
-                    Literal::Float(
-                        FloatTypeWrapper::new(lit.float_value().unwrap_or(Default::default())),
-                        builtin,
-                    )
-                } else if let builtin @ Some(_) = lit.suffix().and_then(BuiltinUint::from_suffix) {
-                    Literal::Uint(lit.value().unwrap_or(0), builtin)
-                } else {
-                    let builtin = lit.suffix().and_then(BuiltinInt::from_suffix);
-                    Literal::Int(lit.value().unwrap_or(0) as i128, builtin)
+    // region: labels
+
+    fn collect_label(&mut self, ast_label: ast::Label) -> LabelId {
+        let label = Label {
+            name: ast_label.lifetime().as_ref().map_or_else(Name::missing, Name::new_lifetime),
+        };
+        self.alloc_label(label, AstPtr::new(&ast_label))
+    }
+
+    fn resolve_label(
+        &self,
+        lifetime: Option<ast::Lifetime>,
+    ) -> Result<Option<LabelId>, BodyDiagnostic> {
+        let Some(lifetime) = lifetime else {
+            return Ok(None)
+        };
+        let name = Name::new_lifetime(&lifetime);
+
+        for (rib_idx, rib) in self.label_ribs.iter().enumerate().rev() {
+            if let Some((label_name, id)) = &rib.label {
+                if *label_name == name {
+                    return if self.is_label_valid_from_rib(rib_idx) {
+                        Ok(Some(*id))
+                    } else {
+                        Err(BodyDiagnostic::UnreachableLabel {
+                            name,
+                            node: InFile::new(
+                                self.expander.current_file_id,
+                                AstPtr::new(&lifetime),
+                            ),
+                        })
+                    };
                 }
             }
-            LiteralKind::FloatNumber(lit) => {
-                let ty = lit.suffix().and_then(BuiltinFloat::from_suffix);
-                Literal::Float(FloatTypeWrapper::new(lit.value().unwrap_or(Default::default())), ty)
-            }
-            LiteralKind::ByteString(bs) => {
-                let text = bs.value().map(Box::from).unwrap_or_else(Default::default);
-                Literal::ByteString(text)
-            }
-            LiteralKind::String(s) => {
-                let text = s.value().map(Box::from).unwrap_or_else(Default::default);
-                Literal::String(text)
-            }
-            LiteralKind::Byte(b) => {
-                Literal::Uint(b.value().unwrap_or_default() as u128, Some(BuiltinUint::U8))
-            }
-            LiteralKind::Char(c) => Literal::Char(c.value().unwrap_or_default()),
-            LiteralKind::Bool(val) => Literal::Bool(val),
         }
+
+        Err(BodyDiagnostic::UndeclaredLabel {
+            name,
+            node: InFile::new(self.expander.current_file_id, AstPtr::new(&lifetime)),
+        })
+    }
+
+    fn is_label_valid_from_rib(&self, rib_index: usize) -> bool {
+        !self.label_ribs[rib_index + 1..].iter().any(|rib| rib.kind.is_label_barrier())
+    }
+
+    fn with_label_rib<T>(&mut self, kind: RibKind, f: impl FnOnce(&mut Self) -> T) -> T {
+        self.label_ribs.push(LabelRib::new(kind));
+        let res = f(self);
+        self.label_ribs.pop();
+        res
+    }
+
+    fn with_labeled_rib<T>(&mut self, label: LabelId, f: impl FnOnce(&mut Self) -> T) -> T {
+        self.label_ribs.push(LabelRib::new_normal((self.body[label].name.clone(), label)));
+        let res = f(self);
+        self.label_ribs.pop();
+        res
+    }
+    // endregion: labels
+}
+
+impl ExprCollector<'_> {
+    fn alloc_expr(&mut self, expr: Expr, ptr: ExprPtr) -> ExprId {
+        let src = self.expander.to_source(ptr);
+        let id = self.body.exprs.alloc(expr);
+        self.source_map.expr_map_back.insert(id, src.clone());
+        self.source_map.expr_map.insert(src, id);
+        id
+    }
+    // FIXME: desugared exprs don't have ptr, that's wrong and should be fixed somehow.
+    fn alloc_expr_desugared(&mut self, expr: Expr) -> ExprId {
+        self.body.exprs.alloc(expr)
+    }
+    fn missing_expr(&mut self) -> ExprId {
+        self.alloc_expr_desugared(Expr::Missing)
+    }
+
+    fn alloc_binding(&mut self, name: Name, mode: BindingAnnotation) -> BindingId {
+        self.body.bindings.alloc(Binding {
+            name,
+            mode,
+            definitions: SmallVec::new(),
+            owner: self.current_binding_owner,
+        })
+    }
+
+    fn alloc_pat(&mut self, pat: Pat, ptr: PatPtr) -> PatId {
+        let src = self.expander.to_source(ptr);
+        let id = self.body.pats.alloc(pat);
+        self.source_map.pat_map_back.insert(id, src.clone());
+        self.source_map.pat_map.insert(src, id);
+        id
+    }
+    // FIXME: desugared pats don't have ptr, that's wrong and should be fixed somehow.
+    fn alloc_pat_desugared(&mut self, pat: Pat) -> PatId {
+        self.body.pats.alloc(pat)
+    }
+    fn missing_pat(&mut self) -> PatId {
+        self.body.pats.alloc(Pat::Missing)
+    }
+
+    fn alloc_label(&mut self, label: Label, ptr: LabelPtr) -> LabelId {
+        let src = self.expander.to_source(ptr);
+        let id = self.body.labels.alloc(label);
+        self.source_map.label_map_back.insert(id, src.clone());
+        self.source_map.label_map.insert(src, id);
+        id
+    }
+    // FIXME: desugared labels don't have ptr, that's wrong and should be fixed somehow.
+    fn alloc_label_desugared(&mut self, label: Label) -> LabelId {
+        self.body.labels.alloc(label)
     }
 }

crates/hir-def/src/body/pretty.rs

@@ -5,7 +5,9 @@ use std::fmt::{self, Write};
 use syntax::ast::HasName;
 
 use crate::{
-    expr::{Array, BindingAnnotation, BindingId, ClosureKind, Literal, Movability, Statement},
+    hir::{
+        Array, BindingAnnotation, BindingId, CaptureBy, ClosureKind, Literal, Movability, Statement,
+    },
     pretty::{print_generic_args, print_path, print_type_ref},
     type_ref::TypeRef,
 };
@@ -13,20 +15,16 @@ use crate::{
 use super::*;
 
 pub(super) fn print_body_hir(db: &dyn DefDatabase, body: &Body, owner: DefWithBodyId) -> String {
-    let needs_semi;
     let header = match owner {
         DefWithBodyId::FunctionId(it) => {
-            needs_semi = false;
             let item_tree_id = it.lookup(db).id;
-            format!("fn {}(…) ", item_tree_id.item_tree(db)[item_tree_id.value].name)
+            format!("fn {}", item_tree_id.item_tree(db)[item_tree_id.value].name)
         }
         DefWithBodyId::StaticId(it) => {
-            needs_semi = true;
             let item_tree_id = it.lookup(db).id;
             format!("static {} = ", item_tree_id.item_tree(db)[item_tree_id.value].name)
         }
         DefWithBodyId::ConstId(it) => {
-            needs_semi = true;
             let item_tree_id = it.lookup(db).id;
             let name = match &item_tree_id.item_tree(db)[item_tree_id.value].name {
                 Some(name) => name.to_string(),
@@ -35,7 +33,6 @@ pub(super) fn print_body_hir(db: &dyn DefDatabase, body: &Body, owner: DefWithBo
             format!("const {name} = ")
         }
         DefWithBodyId::VariantId(it) => {
-            needs_semi = false;
             let src = it.parent.child_source(db);
             let variant = &src.value[it.local_id];
             let name = match &variant.name() {
@@ -47,8 +44,18 @@ pub(super) fn print_body_hir(db: &dyn DefDatabase, body: &Body, owner: DefWithBo
     };
 
     let mut p = Printer { body, buf: header, indent_level: 0, needs_indent: false };
+    if let DefWithBodyId::FunctionId(it) = owner {
+        p.buf.push('(');
+        body.params.iter().zip(&db.function_data(it).params).for_each(|(&param, ty)| {
+            p.print_pat(param);
+            p.buf.push(':');
+            p.print_type_ref(ty);
+        });
+        p.buf.push(')');
+        p.buf.push(' ');
+    }
     p.print_expr(body.body_expr);
-    if needs_semi {
+    if matches!(owner, DefWithBodyId::StaticId(_) | DefWithBodyId::ConstId(_)) {
         p.buf.push(';');
     }
     p.buf
@@ -219,14 +226,14 @@ impl<'a> Printer<'a> {
             }
             Expr::Continue { label } => {
                 w!(self, "continue");
-                if let Some(label) = label {
-                    w!(self, " {}", label);
+                if let Some(lbl) = label {
+                    w!(self, " {}", self.body[*lbl].name);
                 }
             }
             Expr::Break { expr, label } => {
                 w!(self, "break");
-                if let Some(label) = label {
-                    w!(self, " {}", label);
+                if let Some(lbl) = label {
+                    w!(self, " {}", self.body[*lbl].name);
                 }
                 if let Some(expr) = expr {
                     self.whitespace();
@@ -355,7 +362,7 @@ impl<'a> Printer<'a> {
                 self.print_expr(*index);
                 w!(self, "]");
             }
-            Expr::Closure { args, arg_types, ret_type, body, closure_kind } => {
+            Expr::Closure { args, arg_types, ret_type, body, closure_kind, capture_by } => {
                 match closure_kind {
                     ClosureKind::Generator(Movability::Static) => {
                         w!(self, "static ");
@@ -365,6 +372,12 @@ impl<'a> Printer<'a> {
                     }
                     _ => (),
                 }
+                match capture_by {
+                    CaptureBy::Value => {
+                        w!(self, "move ");
+                    }
+                    CaptureBy::Ref => (),
+                }
                 w!(self, "|");
                 for (i, (pat, ty)) in args.iter().zip(arg_types.iter()).enumerate() {
                     if i != 0 {

crates/hir-def/src/body/scope.rs

@@ -8,7 +8,7 @@ use rustc_hash::FxHashMap;
 use crate::{
     body::Body,
     db::DefDatabase,
-    expr::{Binding, BindingId, Expr, ExprId, LabelId, Pat, PatId, Statement},
+    hir::{Binding, BindingId, Expr, ExprId, LabelId, Pat, PatId, Statement},
     BlockId, DefWithBodyId,
 };
 

crates/hir-def/src/child_by_source.rs

@@ -10,9 +10,8 @@ use syntax::ast::HasDocComments;
 
 use crate::{
     db::DefDatabase,
-    dyn_map::DynMap,
+    dyn_map::{keys, DynMap},
     item_scope::ItemScope,
-    keys,
     src::{HasChildSource, HasSource},
     AdtId, AssocItemId, DefWithBodyId, EnumId, EnumVariantId, FieldId, ImplId, Lookup, MacroId,
     ModuleDefId, ModuleId, TraitId, VariantId,

crates/hir-def/src/data.rs

@@ -1,5 +1,7 @@
 //! Contains basic data about various HIR declarations.
 
+pub mod adt;
+
 use std::sync::Arc;
 
 use hir_expand::{name::Name, AstId, ExpandResult, HirFileId, InFile, MacroCallId, MacroDefKind};
@@ -28,7 +30,7 @@ use crate::{
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct FunctionData {
     pub name: Name,
-    pub params: Vec<(Option<Name>, Interned<TypeRef>)>,
+    pub params: Vec<Interned<TypeRef>>,
     pub ret_type: Interned<TypeRef>,
     pub attrs: Attrs,
     pub visibility: RawVisibility,
@@ -98,7 +100,7 @@ impl FunctionData {
             params: enabled_params
                 .clone()
                 .filter_map(|id| match &item_tree[id] {
-                    Param::Normal(name, ty) => Some((name.clone(), ty.clone())),
+                    Param::Normal(ty) => Some(ty.clone()),
                     Param::Varargs => None,
                 })
                 .collect(),

crates/hir-def/src/data/adt.rs

@@ -473,7 +473,7 @@ fn lower_struct(
     trace: &mut Trace<FieldData, Either<ast::TupleField, ast::RecordField>>,
     ast: &InFile<ast::StructKind>,
 ) -> StructKind {
-    let ctx = LowerCtx::new(db, ast.file_id);
+    let ctx = LowerCtx::new(db, &expander.hygiene(), ast.file_id);
 
     match &ast.value {
         ast::StructKind::Tuple(fl) => {

crates/hir-def/src/db.rs

@@ -9,10 +9,10 @@ use la_arena::ArenaMap;
 use syntax::{ast, AstPtr};
 
 use crate::{
-    adt::{EnumData, StructData},
     attr::{Attrs, AttrsWithOwner},
     body::{scope::ExprScopes, Body, BodySourceMap},
     data::{
+        adt::{EnumData, StructData},
         ConstData, FunctionData, ImplData, Macro2Data, MacroRulesData, ProcMacroData, StaticData,
         TraitAliasData, TraitData, TypeAliasData,
     },

crates/hir-def/src/dyn_map.rs

@@ -21,6 +21,8 @@
 //!
 //! This is a work of fiction. Any similarities to Kotlin's `BindingContext` are
 //! a coincidence.
+pub mod keys;
+
 use std::{
     hash::Hash,
     marker::PhantomData,

crates/hir-def/src/generics.rs

@@ -12,7 +12,6 @@ use hir_expand::{
 use intern::Interned;
 use la_arena::{Arena, ArenaMap, Idx};
 use once_cell::unsync::Lazy;
-use std::ops::DerefMut;
 use stdx::impl_from;
 use syntax::ast::{self, HasGenericParams, HasName, HasTypeBounds};
 
@@ -20,8 +19,7 @@ use crate::{
     body::{Expander, LowerCtx},
     child_by_source::ChildBySource,
     db::DefDatabase,
-    dyn_map::DynMap,
-    keys,
+    dyn_map::{keys, DynMap},
     src::{HasChildSource, HasSource},
     type_ref::{LifetimeRef, TypeBound, TypeRef},
     AdtId, ConstParamId, GenericDefId, HasModule, LifetimeParamId, LocalLifetimeParamId,
@@ -177,7 +175,7 @@ impl GenericParams {
                 // Don't create an `Expander` nor call `loc.source(db)` if not needed since this
                 // causes a reparse after the `ItemTree` has been created.
                 let mut expander = Lazy::new(|| Expander::new(db, loc.source(db).file_id, module));
-                for (_, param) in &func_data.params {
+                for param in &func_data.params {
                     generic_params.fill_implicit_impl_trait_args(db, &mut expander, param);
                 }
 
@@ -329,7 +327,7 @@ impl GenericParams {
     pub(crate) fn fill_implicit_impl_trait_args(
         &mut self,
         db: &dyn DefDatabase,
-        expander: &mut impl DerefMut<Target = Expander>,
+        expander: &mut Expander,
         type_ref: &TypeRef,
     ) {
         type_ref.walk(&mut |type_ref| {
@@ -351,7 +349,7 @@ impl GenericParams {
                 let macro_call = mc.to_node(db.upcast());
                 match expander.enter_expand::<ast::Type>(db, macro_call) {
                     Ok(ExpandResult { value: Some((mark, expanded)), .. }) => {
-                        let ctx = LowerCtx::new(db, expander.current_file_id());
+                        let ctx = expander.ctx(db);
                         let type_ref = TypeRef::from_ast(&ctx, expanded);
                         self.fill_implicit_impl_trait_args(db, expander, &type_ref);
                         expander.exit(db, mark);

crates/hir-def/src/hir.rs

@@ -12,12 +12,15 @@
 //!
 //! See also a neighboring `body` module.
 
+pub mod type_ref;
+
 use std::fmt;
 
 use hir_expand::name::Name;
 use intern::Interned;
 use la_arena::{Idx, RawIdx};
 use smallvec::SmallVec;
+use syntax::ast;
 
 use crate::{
     builtin_type::{BuiltinFloat, BuiltinInt, BuiltinUint},
@@ -28,10 +31,10 @@ use crate::{
 
 pub use syntax::ast::{ArithOp, BinaryOp, CmpOp, LogicOp, Ordering, RangeOp, UnaryOp};
 
-pub type ExprId = Idx<Expr>;
-
 pub type BindingId = Idx<Binding>;
 
+pub type ExprId = Idx<Expr>;
+
 /// FIXME: this is a hacky function which should be removed
 pub(crate) fn dummy_expr_id() -> ExprId {
     ExprId::from_raw(RawIdx::from(u32::MAX))
@@ -102,6 +105,45 @@ impl Literal {
     }
 }
 
+impl From<ast::LiteralKind> for Literal {
+    fn from(ast_lit_kind: ast::LiteralKind) -> Self {
+        use ast::LiteralKind;
+        match ast_lit_kind {
+            // FIXME: these should have actual values filled in, but unsure on perf impact
+            LiteralKind::IntNumber(lit) => {
+                if let builtin @ Some(_) = lit.suffix().and_then(BuiltinFloat::from_suffix) {
+                    Literal::Float(
+                        FloatTypeWrapper::new(lit.float_value().unwrap_or(Default::default())),
+                        builtin,
+                    )
+                } else if let builtin @ Some(_) = lit.suffix().and_then(BuiltinUint::from_suffix) {
+                    Literal::Uint(lit.value().unwrap_or(0), builtin)
+                } else {
+                    let builtin = lit.suffix().and_then(BuiltinInt::from_suffix);
+                    Literal::Int(lit.value().unwrap_or(0) as i128, builtin)
+                }
+            }
+            LiteralKind::FloatNumber(lit) => {
+                let ty = lit.suffix().and_then(BuiltinFloat::from_suffix);
+                Literal::Float(FloatTypeWrapper::new(lit.value().unwrap_or(Default::default())), ty)
+            }
+            LiteralKind::ByteString(bs) => {
+                let text = bs.value().map(Box::from).unwrap_or_else(Default::default);
+                Literal::ByteString(text)
+            }
+            LiteralKind::String(s) => {
+                let text = s.value().map(Box::from).unwrap_or_else(Default::default);
+                Literal::String(text)
+            }
+            LiteralKind::Byte(b) => {
+                Literal::Uint(b.value().unwrap_or_default() as u128, Some(BuiltinUint::U8))
+            }
+            LiteralKind::Char(c) => Literal::Char(c.value().unwrap_or_default()),
+            LiteralKind::Bool(val) => Literal::Bool(val),
+        }
+    }
+}
+
 #[derive(Debug, Clone, Eq, PartialEq)]
 pub enum Expr {
     /// This is produced if the syntax tree does not have a required expression piece.
@@ -168,11 +210,11 @@ pub enum Expr {
         arms: Box<[MatchArm]>,
     },
     Continue {
-        label: Option<Name>,
+        label: Option<LabelId>,
     },
     Break {
         expr: Option<ExprId>,
-        label: Option<Name>,
+        label: Option<LabelId>,
     },
     Return {
         expr: Option<ExprId>,
@@ -233,6 +275,7 @@ pub enum Expr {
         ret_type: Option<Interned<TypeRef>>,
         body: ExprId,
         closure_kind: ClosureKind,
+        capture_by: CaptureBy,
     },
     Tuple {
         exprs: Box<[ExprId]>,
@@ -250,6 +293,14 @@ pub enum ClosureKind {
     Async,
 }
 
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum CaptureBy {
+    /// `move |x| y + x`.
+    Value,
+    /// `move` keyword was not specified.
+    Ref,
+}
+
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub enum Movability {
     Static,
@@ -442,6 +493,22 @@ pub struct Binding {
     pub name: Name,
     pub mode: BindingAnnotation,
     pub definitions: SmallVec<[PatId; 1]>,
+    /// Id of the closure/generator that owns this binding. If it is owned by the
+    /// top level expression, this field would be `None`.
+    pub owner: Option<ExprId>,
+}
+
+impl Binding {
+    pub fn is_upvar(&self, relative_to: ExprId) -> bool {
+        match self.owner {
+            Some(x) => {
+                // We assign expression ids in a way that outer closures will recieve
+                // a lower id
+                x.into_raw() < relative_to.into_raw()
+            }
+            None => true,
+        }
+    }
 }
 
 #[derive(Debug, Clone, Eq, PartialEq)]

crates/hir-def/src/hir/type_ref.rs

@@ -13,7 +13,7 @@ use syntax::ast::{self, HasName};
 use crate::{
     body::LowerCtx,
     builtin_type::{BuiltinInt, BuiltinType, BuiltinUint},
-    expr::Literal,
+    hir::Literal,
     path::Path,
 };
 

crates/hir-def/src/item_tree.rs

@@ -152,14 +152,6 @@ impl ItemTree {
         &self.top_level
     }
 
-    pub fn block_has_items(
-        db: &dyn DefDatabase,
-        file_id: HirFileId,
-        block: &ast::BlockExpr,
-    ) -> bool {
-        lower::Ctx::new(db, file_id).block_has_items(block)
-    }
-
     /// Returns the inner attributes of the source file.
     pub fn top_level_attrs(&self, db: &dyn DefDatabase, krate: CrateId) -> Attrs {
         Attrs::filter(
@@ -614,7 +606,7 @@ pub struct Function {
 
 #[derive(Debug, Clone, Eq, PartialEq)]
 pub enum Param {
-    Normal(Option<Name>, Interned<TypeRef>),
+    Normal(Interned<TypeRef>),
     Varargs,
 }
 

crates/hir-def/src/item_tree/lower.rs

@@ -29,7 +29,7 @@ impl<'a> Ctx<'a> {
             db,
             tree: ItemTree::default(),
             source_ast_id_map: db.ast_id_map(file),
-            body_ctx: crate::body::LowerCtx::new(db, file),
+            body_ctx: crate::body::LowerCtx::with_file_id(db, file),
         }
     }
 
@@ -101,34 +101,6 @@ impl<'a> Ctx<'a> {
         self.tree
     }
 
-    pub(super) fn block_has_items(mut self, block: &ast::BlockExpr) -> bool {
-        let statement_has_item = block
-            .statements()
-            .find_map(|stmt| match stmt {
-                ast::Stmt::Item(item) => self.lower_mod_item(&item),
-                // Macro calls can be both items and expressions. The syntax library always treats
-                // them as expressions here, so we undo that.
-                ast::Stmt::ExprStmt(es) => match es.expr()? {
-                    ast::Expr::MacroExpr(expr) => self.lower_mod_item(&expr.macro_call()?.into()),
-                    _ => None,
-                },
-                _ => None,
-            })
-            .is_some();
-        if statement_has_item {
-            return true;
-        }
-
-        if let Some(ast::Expr::MacroExpr(expr)) = block.tail_expr() {
-            if let Some(call) = expr.macro_call() {
-                if let Some(_) = self.lower_mod_item(&call.into()) {
-                    return true;
-                }
-            }
-        }
-        false
-    }
-
     fn data(&mut self) -> &mut ItemTreeData {
         self.tree.data_mut()
     }
@@ -321,7 +293,7 @@ impl<'a> Ctx<'a> {
                     }
                 };
                 let ty = Interned::new(self_type);
-                let idx = self.data().params.alloc(Param::Normal(None, ty));
+                let idx = self.data().params.alloc(Param::Normal(ty));
                 self.add_attrs(
                     idx.into(),
                     RawAttrs::new(self.db.upcast(), &self_param, self.hygiene()),
@@ -334,19 +306,7 @@ impl<'a> Ctx<'a> {
                     None => {
                         let type_ref = TypeRef::from_ast_opt(&self.body_ctx, param.ty());
                         let ty = Interned::new(type_ref);
-                        let mut pat = param.pat();
-                        // FIXME: This really shouldn't be here, in fact FunctionData/ItemTree's function shouldn't know about
-                        // pattern names at all
-                        let name = 'name: loop {
-                            match pat {
-                                Some(ast::Pat::RefPat(ref_pat)) => pat = ref_pat.pat(),
-                                Some(ast::Pat::IdentPat(ident)) => {
-                                    break 'name ident.name().map(|it| it.as_name())
-                                }
-                                _ => break 'name None,
-                            }
-                        };
-                        self.data().params.alloc(Param::Normal(name, ty))
+                        self.data().params.alloc(Param::Normal(ty))
                     }
                 };
                 self.add_attrs(idx.into(), RawAttrs::new(self.db.upcast(), &param, self.hygiene()));

crates/hir-def/src/item_tree/pretty.rs

@@ -257,21 +257,15 @@ impl<'a> Printer<'a> {
                 w!(self, "(");
                 if !params.is_empty() {
                     self.indented(|this| {
-                        for (i, param) in params.clone().enumerate() {
+                        for param in params.clone() {
                             this.print_attrs_of(param);
                             match &this.tree[param] {
-                                Param::Normal(name, ty) => {
-                                    match name {
-                                        Some(name) => w!(this, "{}: ", name),
-                                        None => w!(this, "_: "),
+                                Param::Normal(ty) => {
+                                    if flags.contains(FnFlags::HAS_SELF_PARAM) {
+                                        w!(this, "self: ");
                                     }
                                     this.print_type_ref(ty);
-                                    w!(this, ",");
-                                    if flags.contains(FnFlags::HAS_SELF_PARAM) && i == 0 {
-                                        wln!(this, "  // self");
-                                    } else {
-                                        wln!(this);
-                                    }
+                                    wln!(this, ",");
                                 }
                                 Param::Varargs => {
                                     wln!(this, "...");

crates/hir-def/src/item_tree/tests.rs

@@ -165,7 +165,7 @@ trait Tr: SuperTrait + 'lifetime {
     fn method(&self);
 }
         "#,
-        expect![[r##"
+        expect![[r#"
             pub static mut ST: () = _;
 
             pub(self) const _: Anon = _;
@@ -174,8 +174,8 @@ trait Tr: SuperTrait + 'lifetime {
             #[inner_attr_in_fn]
             pub(self) fn f(
                 #[attr]
-                arg: u8,
-                _: (),
+                u8,
+                (),
             ) -> () { ... }
 
             pub(self) trait Tr<Self>
@@ -186,10 +186,10 @@ trait Tr: SuperTrait + 'lifetime {
                 pub(self) type Assoc: AssocBound = Default;
 
                 pub(self) fn method(
-                    _: &Self,  // self
+                    self: &Self,
                 ) -> ();
             }
-        "##]],
+        "#]],
     );
 }
 
@@ -336,7 +336,7 @@ trait Tr<'a, T: 'a>: Super where Self: for<'a> Tr<'a, T> {}
                 T: 'b
             {
                 pub(self) fn f<G>(
-                    arg: impl Copy,
+                    impl Copy,
                 ) -> impl Copy
                 where
                     G: 'a { ... }

crates/hir-def/src/layout.rs

@@ -92,6 +92,7 @@ pub enum LayoutError {
     SizeOverflow,
     TargetLayoutNotAvailable,
     HasPlaceholder,
+    HasErrorType,
     NotImplemented,
     Unknown,
 }

crates/hir-def/src/lib.rs

@@ -18,24 +18,21 @@ pub mod db;
 
 pub mod attr;
 pub mod path;
-pub mod type_ref;
 pub mod builtin_type;
-pub mod builtin_attr;
 pub mod per_ns;
 pub mod item_scope;
 
 pub mod dyn_map;
-pub mod keys;
 
 pub mod item_tree;
 
-pub mod adt;
 pub mod data;
 pub mod generics;
 pub mod lang_item;
 pub mod layout;
 
-pub mod expr;
+pub mod hir;
+pub use self::hir::type_ref;
 pub mod body;
 pub mod resolver;
 
@@ -82,8 +79,8 @@ use syntax::ast;
 use ::tt::token_id as tt;
 
 use crate::{
-    adt::VariantData,
     builtin_type::BuiltinType,
+    data::adt::VariantData,
     item_tree::{
         Const, Enum, Function, Impl, ItemTreeId, ItemTreeNode, MacroDef, MacroRules, ModItem,
         Static, Struct, Trait, TraitAlias, TypeAlias, Union,
@@ -236,7 +233,7 @@ pub struct EnumVariantId {
     pub local_id: LocalEnumVariantId,
 }
 
-pub type LocalEnumVariantId = Idx<adt::EnumVariantData>;
+pub type LocalEnumVariantId = Idx<data::adt::EnumVariantData>;
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
 pub struct FieldId {
@@ -244,7 +241,7 @@ pub struct FieldId {
     pub local_id: LocalFieldId,
 }
 
-pub type LocalFieldId = Idx<adt::FieldData>;
+pub type LocalFieldId = Idx<data::adt::FieldData>;
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
 pub struct ConstId(salsa::InternId);

crates/hir-def/src/macro_expansion_tests/builtin_derive_macro.rs

@@ -16,7 +16,7 @@ struct Foo;
 #[derive(Copy)]
 struct Foo;
 
-impl < > core::marker::Copy for Foo< > {}"#]],
+impl < > core::marker::Copy for Foo< > where {}"#]],
     );
 }
 
@@ -41,7 +41,7 @@ macro Copy {}
 #[derive(Copy)]
 struct Foo;
 
-impl < > crate ::marker::Copy for Foo< > {}"#]],
+impl < > crate ::marker::Copy for Foo< > where {}"#]],
     );
 }
 
@@ -57,7 +57,7 @@ struct Foo<A, B>;
 #[derive(Copy)]
 struct Foo<A, B>;
 
-impl <T0: core::marker::Copy, T1: core::marker::Copy, > core::marker::Copy for Foo<T0, T1, > {}"#]],
+impl <A: core::marker::Copy, B: core::marker::Copy, > core::marker::Copy for Foo<A, B, > where {}"#]],
     );
 }
 
@@ -74,7 +74,7 @@ struct Foo<A, B, 'a, 'b>;
 #[derive(Copy)]
 struct Foo<A, B, 'a, 'b>;
 
-impl <T0: core::marker::Copy, T1: core::marker::Copy, > core::marker::Copy for Foo<T0, T1, > {}"#]],
+impl <A: core::marker::Copy, B: core::marker::Copy, > core::marker::Copy for Foo<A, B, > where {}"#]],
     );
 }
 
@@ -90,7 +90,7 @@ struct Foo<A, B>;
 #[derive(Clone)]
 struct Foo<A, B>;
 
-impl <T0: core::clone::Clone, T1: core::clone::Clone, > core::clone::Clone for Foo<T0, T1, > {}"#]],
+impl <A: core::clone::Clone, B: core::clone::Clone, > core::clone::Clone for Foo<A, B, > where {}"#]],
     );
 }
 
@@ -106,6 +106,6 @@ struct Foo<const X: usize, T>(u32);
 #[derive(Clone)]
 struct Foo<const X: usize, T>(u32);
 
-impl <const T0: usize, T1: core::clone::Clone, > core::clone::Clone for Foo<T0, T1, > {}"#]],
+impl <const X: usize, T: core::clone::Clone, > core::clone::Clone for Foo<X, T, > where {}"#]],
     );
 }

crates/hir-def/src/nameres/attr_resolution.rs

@@ -4,7 +4,8 @@ use hir_expand::{attrs::Attr, MacroCallId};
 use syntax::{ast, SmolStr};
 
 use crate::{
-    attr_macro_as_call_id, builtin_attr,
+    attr::builtin::{find_builtin_attr_idx, TOOL_MODULES},
+    attr_macro_as_call_id,
     db::DefDatabase,
     item_scope::BuiltinShadowMode,
     macro_id_to_def_id,
@@ -76,19 +77,15 @@ impl DefMap {
             let pred = |n: &_| *n == name;
 
             let registered = self.registered_tools.iter().map(SmolStr::as_str);
-            let is_tool = builtin_attr::TOOL_MODULES.iter().copied().chain(registered).any(pred);
+            let is_tool = TOOL_MODULES.iter().copied().chain(registered).any(pred);
             // FIXME: tool modules can be shadowed by actual modules
             if is_tool {
                 return true;
             }
 
             if segments.len() == 1 {
-                let registered = self.registered_attrs.iter().map(SmolStr::as_str);
-                let is_inert = builtin_attr::INERT_ATTRIBUTES
-                    .iter()
-                    .map(|it| it.name)
-                    .chain(registered)
-                    .any(pred);
+                let mut registered = self.registered_attrs.iter().map(SmolStr::as_str);
+                let is_inert = find_builtin_attr_idx(&name).is_some() || registered.any(pred);
                 return is_inert;
             }
         }

crates/hir-def/src/nameres/path_resolution.rs

@@ -331,11 +331,11 @@ impl DefMap {
                         Some(local_id) => {
                             let variant = EnumVariantId { parent: e, local_id };
                             match &*enum_data.variants[local_id].variant_data {
-                                crate::adt::VariantData::Record(_) => {
+                                crate::data::adt::VariantData::Record(_) => {
                                     PerNs::types(variant.into(), Visibility::Public)
                                 }
-                                crate::adt::VariantData::Tuple(_)
-                                | crate::adt::VariantData::Unit => {
+                                crate::data::adt::VariantData::Tuple(_)
+                                | crate::data::adt::VariantData::Unit => {
                                     PerNs::both(variant.into(), variant.into(), Visibility::Public)
                                 }
                             }

crates/hir-def/src/resolver.rs

@@ -12,8 +12,8 @@ use crate::{
     body::scope::{ExprScopes, ScopeId},
     builtin_type::BuiltinType,
     db::DefDatabase,
-    expr::{BindingId, ExprId, LabelId},
     generics::{GenericParams, TypeOrConstParamData},
+    hir::{BindingId, ExprId, LabelId},
     item_scope::{BuiltinShadowMode, BUILTIN_SCOPE},
     lang_item::LangItemTarget,
     nameres::DefMap,

crates/hir-expand/src/builtin_derive_macro.rs

@@ -1,11 +1,12 @@
 //! Builtin derives.
 
 use base_db::{CrateOrigin, LangCrateOrigin};
+use std::collections::HashSet;
 use tracing::debug;
 
 use crate::tt::{self, TokenId};
 use syntax::{
-    ast::{self, AstNode, HasGenericParams, HasModuleItem, HasName},
+    ast::{self, AstNode, HasGenericParams, HasModuleItem, HasName, HasTypeBounds, PathType},
     match_ast,
 };
 
@@ -60,8 +61,11 @@ pub fn find_builtin_derive(ident: &name::Name) -> Option<BuiltinDeriveExpander>
 
 struct BasicAdtInfo {
     name: tt::Ident,
-    /// `Some(ty)` if it's a const param of type `ty`, `None` if it's a type param.
-    param_types: Vec<Option<tt::Subtree>>,
+    /// first field is the name, and
+    /// second field is `Some(ty)` if it's a const param of type `ty`, `None` if it's a type param.
+    /// third fields is where bounds, if any
+    param_types: Vec<(tt::Subtree, Option<tt::Subtree>, Option<tt::Subtree>)>,
+    associated_types: Vec<tt::Subtree>,
 }
 
 fn parse_adt(tt: &tt::Subtree) -> Result<BasicAdtInfo, ExpandError> {
@@ -86,18 +90,28 @@ fn parse_adt(tt: &tt::Subtree) -> Result<BasicAdtInfo, ExpandError> {
             },
         }
     };
-    let name = name.ok_or_else(|| {
-        debug!("parsed item has no name");
-        ExpandError::Other("missing name".into())
-    })?;
-    let name_token_id =
-        token_map.token_by_range(name.syntax().text_range()).unwrap_or_else(TokenId::unspecified);
-    let name_token = tt::Ident { span: name_token_id, text: name.text().into() };
+    let mut param_type_set: HashSet<String> = HashSet::new();
     let param_types = params
         .into_iter()
         .flat_map(|param_list| param_list.type_or_const_params())
         .map(|param| {
-            if let ast::TypeOrConstParam::Const(param) = param {
+            let name = {
+                let this = param.name();
+                match this {
+                    Some(x) => {
+                        param_type_set.insert(x.to_string());
+                        mbe::syntax_node_to_token_tree(x.syntax()).0
+                    }
+                    None => tt::Subtree::empty(),
+                }
+            };
+            let bounds = match &param {
+                ast::TypeOrConstParam::Type(x) => {
+                    x.type_bound_list().map(|x| mbe::syntax_node_to_token_tree(x.syntax()).0)
+                }
+                ast::TypeOrConstParam::Const(_) => None,
+            };
+            let ty = if let ast::TypeOrConstParam::Const(param) = param {
                 let ty = param
                     .ty()
                     .map(|ty| mbe::syntax_node_to_token_tree(ty.syntax()).0)
@@ -105,27 +119,97 @@ fn parse_adt(tt: &tt::Subtree) -> Result<BasicAdtInfo, ExpandError> {
                 Some(ty)
             } else {
                 None
-            }
+            };
+            (name, ty, bounds)
         })
         .collect();
-    Ok(BasicAdtInfo { name: name_token, param_types })
+    let is_associated_type = |p: &PathType| {
+        if let Some(p) = p.path() {
+            if let Some(parent) = p.qualifier() {
+                if let Some(x) = parent.segment() {
+                    if let Some(x) = x.path_type() {
+                        if let Some(x) = x.path() {
+                            if let Some(pname) = x.as_single_name_ref() {
+                                if param_type_set.contains(&pname.to_string()) {
+                                    // <T as Trait>::Assoc
+                                    return true;
+                                }
+                            }
+                        }
+                    }
+                }
+                if let Some(pname) = parent.as_single_name_ref() {
+                    if param_type_set.contains(&pname.to_string()) {
+                        // T::Assoc
+                        return true;
+                    }
+                }
+            }
+        }
+        false
+    };
+    let associated_types = node
+        .descendants()
+        .filter_map(PathType::cast)
+        .filter(is_associated_type)
+        .map(|x| mbe::syntax_node_to_token_tree(x.syntax()).0)
+        .collect::<Vec<_>>();
+    let name = name.ok_or_else(|| {
+        debug!("parsed item has no name");
+        ExpandError::Other("missing name".into())
+    })?;
+    let name_token_id =
+        token_map.token_by_range(name.syntax().text_range()).unwrap_or_else(TokenId::unspecified);
+    let name_token = tt::Ident { span: name_token_id, text: name.text().into() };
+    Ok(BasicAdtInfo { name: name_token, param_types, associated_types })
 }
 
+/// Given that we are deriving a trait `DerivedTrait` for a type like:
+///
+/// ```ignore (only-for-syntax-highlight)
+/// struct Struct<'a, ..., 'z, A, B: DeclaredTrait, C, ..., Z> where C: WhereTrait {
+///     a: A,
+///     b: B::Item,
+///     b1: <B as DeclaredTrait>::Item,
+///     c1: <C as WhereTrait>::Item,
+///     c2: Option<<C as WhereTrait>::Item>,
+///     ...
+/// }
+/// ```
+///
+/// create an impl like:
+///
+/// ```ignore (only-for-syntax-highlight)
+/// impl<'a, ..., 'z, A, B: DeclaredTrait, C, ... Z> where
+///     C:                       WhereTrait,
+///     A: DerivedTrait + B1 + ... + BN,
+///     B: DerivedTrait + B1 + ... + BN,
+///     C: DerivedTrait + B1 + ... + BN,
+///     B::Item:                 DerivedTrait + B1 + ... + BN,
+///     <C as WhereTrait>::Item: DerivedTrait + B1 + ... + BN,
+///     ...
+/// {
+///     ...
+/// }
+/// ```
+///
+/// where B1, ..., BN are the bounds given by `bounds_paths`.'. Z is a phantom type, and
+/// therefore does not get bound by the derived trait.
 fn expand_simple_derive(tt: &tt::Subtree, trait_path: tt::Subtree) -> ExpandResult<tt::Subtree> {
     let info = match parse_adt(tt) {
         Ok(info) => info,
         Err(e) => return ExpandResult::with_err(tt::Subtree::empty(), e),
     };
+    let mut where_block = vec![];
     let (params, args): (Vec<_>, Vec<_>) = info
         .param_types
         .into_iter()
-        .enumerate()
-        .map(|(idx, param_ty)| {
-            let ident = tt::Leaf::Ident(tt::Ident {
-                span: tt::TokenId::unspecified(),
-                text: format!("T{idx}").into(),
-            });
+        .map(|(ident, param_ty, bound)| {
             let ident_ = ident.clone();
+            if let Some(b) = bound {
+                let ident = ident.clone();
+                where_block.push(quote! { #ident : #b , });
+            }
             if let Some(ty) = param_ty {
                 (quote! { const #ident : #ty , }, quote! { #ident_ , })
             } else {
@@ -134,9 +218,16 @@ fn expand_simple_derive(tt: &tt::Subtree, trait_path: tt::Subtree) -> ExpandResu
             }
         })
         .unzip();
+
+    where_block.extend(info.associated_types.iter().map(|x| {
+        let x = x.clone();
+        let bound = trait_path.clone();
+        quote! { #x : #bound , }
+    }));
+
     let name = info.name;
     let expanded = quote! {
-        impl < ##params > #trait_path for #name < ##args > {}
+        impl < ##params > #trait_path for #name < ##args > where ##where_block {}
     };
     ExpandResult::ok(expanded)
 }

crates/hir-expand/src/lib.rs

@@ -55,7 +55,7 @@ pub type ExpandResult<T> = ValueResult<T, ExpandError>;
 pub enum ExpandError {
     UnresolvedProcMacro(CrateId),
     Mbe(mbe::ExpandError),
-    RecursionOverflowPosioned,
+    RecursionOverflowPoisoned,
     Other(Box<str>),
 }
 
@@ -70,7 +70,7 @@ impl fmt::Display for ExpandError {
         match self {
             ExpandError::UnresolvedProcMacro(_) => f.write_str("unresolved proc-macro"),
             ExpandError::Mbe(it) => it.fmt(f),
-            ExpandError::RecursionOverflowPosioned => {
+            ExpandError::RecursionOverflowPoisoned => {
                 f.write_str("overflow expanding the original macro")
             }
             ExpandError::Other(it) => f.write_str(it),

crates/hir-expand/src/name.rs

@@ -120,8 +120,7 @@ impl Name {
         use std::sync::atomic::{AtomicUsize, Ordering};
         static CNT: AtomicUsize = AtomicUsize::new(0);
         let c = CNT.fetch_add(1, Ordering::Relaxed);
-        // FIXME: Currently a `__RA_generated_name` in user code will break our analysis
-        Name::new_text(format!("__RA_geneated_name_{c}").into())
+        Name::new_text(format!("<ra@gennew>{c}").into())
     }
 
     /// Returns the tuple index this name represents if it is a tuple field.

crates/hir-ty/src/chalk_db.rs

@@ -9,7 +9,7 @@ use chalk_solve::rust_ir::{self, OpaqueTyDatumBound, WellKnownTrait};
 
 use base_db::CrateId;
 use hir_def::{
-    expr::Movability,
+    hir::Movability,
     lang_item::{lang_attr, LangItem, LangItemTarget},
     AssocItemId, BlockId, GenericDefId, HasModule, ItemContainerId, Lookup, TypeAliasId,
 };
@@ -18,9 +18,10 @@ use hir_expand::name::name;
 use crate::{
     db::HirDatabase,
     display::HirDisplay,
-    from_assoc_type_id, from_chalk_trait_id, make_binders, make_single_type_binders,
+    from_assoc_type_id, from_chalk_trait_id, from_foreign_def_id, make_binders,
+    make_single_type_binders,
     mapping::{from_chalk, ToChalk, TypeAliasAsValue},
-    method_resolution::{TyFingerprint, ALL_FLOAT_FPS, ALL_INT_FPS},
+    method_resolution::{TraitImpls, TyFingerprint, ALL_FLOAT_FPS, ALL_INT_FPS},
     to_assoc_type_id, to_chalk_trait_id,
     traits::ChalkContext,
     utils::generics,
@@ -106,6 +107,19 @@ impl<'a> chalk_solve::RustIrDatabase<Interner> for ChalkContext<'a> {
             _ => self_ty_fp.as_ref().map(std::slice::from_ref).unwrap_or(&[]),
         };
 
+        let trait_module = trait_.module(self.db.upcast());
+        let type_module = match self_ty_fp {
+            Some(TyFingerprint::Adt(adt_id)) => Some(adt_id.module(self.db.upcast())),
+            Some(TyFingerprint::ForeignType(type_id)) => {
+                Some(from_foreign_def_id(type_id).module(self.db.upcast()))
+            }
+            Some(TyFingerprint::Dyn(trait_id)) => Some(trait_id.module(self.db.upcast())),
+            _ => None,
+        };
+
+        let mut def_blocks =
+            [trait_module.containing_block(), type_module.and_then(|it| it.containing_block())];
+
         // Note: Since we're using impls_for_trait, only impls where the trait
         // can be resolved should ever reach Chalk. impl_datum relies on that
         // and will panic if the trait can't be resolved.
@@ -120,6 +134,14 @@ impl<'a> chalk_solve::RustIrDatabase<Interner> for ChalkContext<'a> {
                 .and_then(|map| map.parent())
                 .and_then(|module| module.containing_block())
         })
+        .inspect(|&block_id| {
+            // make sure we don't search the same block twice
+            def_blocks.iter_mut().for_each(|block| {
+                if *block == Some(block_id) {
+                    *block = None;
+                }
+            });
+        })
         .filter_map(|block_id| self.db.trait_impls_in_block(block_id));
 
         let id_to_chalk = |id: hir_def::ImplId| id.to_chalk(self.db);
@@ -127,18 +149,27 @@ impl<'a> chalk_solve::RustIrDatabase<Interner> for ChalkContext<'a> {
         match fps {
             [] => {
                 debug!("Unrestricted search for {:?} impls...", trait_);
-                impl_maps.into_iter().chain(block_impls).for_each(|impls| {
+                let mut f = |impls: Arc<TraitImpls>| {
                     result.extend(impls.for_trait(trait_).map(id_to_chalk));
-                });
+                };
+                impl_maps.into_iter().chain(block_impls).for_each(&mut f);
+                def_blocks
+                    .into_iter()
+                    .filter_map(|it| self.db.trait_impls_in_block(it?))
+                    .for_each(f);
             }
             fps => {
-                impl_maps.into_iter().chain(block_impls).for_each(|impls| {
-                    result.extend(
-                        fps.iter().flat_map(|fp| {
+                let mut f =
+                    |impls: Arc<TraitImpls>| {
+                        result.extend(fps.iter().flat_map(|fp| {
                             impls.for_trait_and_self_ty(trait_, *fp).map(id_to_chalk)
-                        }),
-                    );
-                });
+                        }));
+                    };
+                impl_maps.into_iter().chain(block_impls).for_each(&mut f);
+                def_blocks
+                    .into_iter()
+                    .filter_map(|it| self.db.trait_impls_in_block(it?))
+                    .for_each(f);
             }
         }
 
@@ -384,8 +415,8 @@ impl<'a> chalk_solve::RustIrDatabase<Interner> for ChalkContext<'a> {
         let input_output = crate::make_type_and_const_binders(it, input_output);
 
         let movability = match self.db.body(parent)[expr] {
-            hir_def::expr::Expr::Closure {
-                closure_kind: hir_def::expr::ClosureKind::Generator(movability),
+            hir_def::hir::Expr::Closure {
+                closure_kind: hir_def::hir::ClosureKind::Generator(movability),
                 ..
             } => movability,
             _ => unreachable!("non generator expression interned as generator"),

crates/hir-ty/src/chalk_ext.rs

@@ -12,8 +12,9 @@ use hir_def::{
 use crate::{
     db::HirDatabase, from_assoc_type_id, from_chalk_trait_id, from_foreign_def_id,
     from_placeholder_idx, to_chalk_trait_id, utils::generics, AdtId, AliasEq, AliasTy, Binders,
-    CallableDefId, CallableSig, DynTy, FnPointer, ImplTraitId, Interner, Lifetime, ProjectionTy,
-    QuantifiedWhereClause, Substitution, TraitRef, Ty, TyBuilder, TyKind, TypeFlags, WhereClause,
+    CallableDefId, CallableSig, ClosureId, DynTy, FnPointer, ImplTraitId, Interner, Lifetime,
+    ProjectionTy, QuantifiedWhereClause, Substitution, TraitRef, Ty, TyBuilder, TyKind, TypeFlags,
+    WhereClause,
 };
 
 pub trait TyExt {
@@ -28,6 +29,7 @@ pub trait TyExt {
     fn as_adt(&self) -> Option<(hir_def::AdtId, &Substitution)>;
     fn as_builtin(&self) -> Option<BuiltinType>;
     fn as_tuple(&self) -> Option<&Substitution>;
+    fn as_closure(&self) -> Option<ClosureId>;
     fn as_fn_def(&self, db: &dyn HirDatabase) -> Option<FunctionId>;
     fn as_reference(&self) -> Option<(&Ty, Lifetime, Mutability)>;
     fn as_reference_or_ptr(&self) -> Option<(&Ty, Rawness, Mutability)>;
@@ -128,6 +130,13 @@ impl TyExt for Ty {
         }
     }
 
+    fn as_closure(&self) -> Option<ClosureId> {
+        match self.kind(Interner) {
+            TyKind::Closure(id, _) => Some(*id),
+            _ => None,
+        }
+    }
+
     fn as_fn_def(&self, db: &dyn HirDatabase) -> Option<FunctionId> {
         match self.callable_def(db) {
             Some(CallableDefId::FunctionId(func)) => Some(func),

crates/hir-ty/src/consteval.rs

@@ -3,7 +3,7 @@
 use base_db::CrateId;
 use chalk_ir::{BoundVar, DebruijnIndex, GenericArgData};
 use hir_def::{
-    expr::Expr,
+    hir::Expr,
     path::Path,
     resolver::{Resolver, ValueNs},
     type_ref::ConstRef,

crates/hir-ty/src/consteval/tests.rs

@@ -1105,6 +1105,81 @@ fn try_block() {
     );
 }
 
+#[test]
+fn closures() {
+    check_number(
+        r#"
+    //- minicore: fn, copy
+    const GOAL: i32 = {
+        let y = 5;
+        let c = |x| x + y;
+        c(2)
+    };
+        "#,
+        7,
+    );
+    check_number(
+        r#"
+    //- minicore: fn, copy
+    const GOAL: i32 = {
+        let y = 5;
+        let c = |(a, b): &(i32, i32)| *a + *b + y;
+        c(&(2, 3))
+    };
+        "#,
+        10,
+    );
+    check_number(
+        r#"
+    //- minicore: fn, copy
+    const GOAL: i32 = {
+        let mut y = 5;
+        let c = |x| {
+            y = y + x;
+        };
+        c(2);
+        c(3);
+        y
+    };
+        "#,
+        10,
+    );
+    check_number(
+        r#"
+    //- minicore: fn, copy
+    struct X(i32);
+    impl X {
+        fn mult(&mut self, n: i32) {
+            self.0 = self.0 * n
+        }
+    }
+    const GOAL: i32 = {
+        let x = X(1);
+        let c = || {
+            x.mult(2);
+            || {
+                x.mult(3);
+                || {
+                    || {
+                        x.mult(4);
+                        || {
+                            x.mult(x.0);
+                            || {
+                                x.0
+                            }
+                        }
+                    }
+                }
+            }
+        };
+        let r = c()()()()()();
+        r + x.0
+    };
+        "#,
+        24 * 24 * 2,
+    );
+}
+
 #[test]
 fn or_pattern() {
     check_number(

crates/hir-ty/src/db.rs

@@ -6,7 +6,7 @@ use std::sync::Arc;
 use base_db::{impl_intern_key, salsa, CrateId, Upcast};
 use hir_def::{
     db::DefDatabase,
-    expr::ExprId,
+    hir::ExprId,
     layout::{Layout, LayoutError, TargetDataLayout},
     AdtId, BlockId, ConstId, ConstParamId, DefWithBodyId, EnumVariantId, FunctionId, GenericDefId,
     ImplId, LifetimeParamId, LocalFieldId, TypeOrConstParamId, VariantId,
@@ -19,9 +19,9 @@ use crate::{
     consteval::ConstEvalError,
     method_resolution::{InherentImpls, TraitImpls, TyFingerprint},
     mir::{BorrowckResult, MirBody, MirLowerError},
-    Binders, CallableDefId, Const, FnDefId, GenericArg, ImplTraitId, InferenceResult, Interner,
-    PolyFnSig, QuantifiedWhereClause, ReturnTypeImplTraits, Substitution, TraitRef, Ty, TyDefId,
-    ValueTyDefId,
+    Binders, CallableDefId, ClosureId, Const, FnDefId, GenericArg, ImplTraitId, InferenceResult,
+    Interner, PolyFnSig, QuantifiedWhereClause, ReturnTypeImplTraits, Substitution, TraitRef, Ty,
+    TyDefId, ValueTyDefId,
 };
 use hir_expand::name::Name;
 
@@ -38,8 +38,11 @@ pub trait HirDatabase: DefDatabase + Upcast<dyn DefDatabase> {
     #[salsa::cycle(crate::mir::mir_body_recover)]
     fn mir_body(&self, def: DefWithBodyId) -> Result<Arc<MirBody>, MirLowerError>;
 
+    #[salsa::invoke(crate::mir::mir_body_for_closure_query)]
+    fn mir_body_for_closure(&self, def: ClosureId) -> Result<Arc<MirBody>, MirLowerError>;
+
     #[salsa::invoke(crate::mir::borrowck_query)]
-    fn borrowck(&self, def: DefWithBodyId) -> Result<Arc<BorrowckResult>, MirLowerError>;
+    fn borrowck(&self, def: DefWithBodyId) -> Result<Arc<[BorrowckResult]>, MirLowerError>;
 
     #[salsa::invoke(crate::lower::ty_query)]
     #[salsa::cycle(crate::lower::ty_recover)]

crates/hir-ty/src/diagnostics/decl_check.rs

@@ -16,8 +16,8 @@ use std::fmt;
 
 use base_db::CrateId;
 use hir_def::{
-    adt::VariantData,
-    expr::{Pat, PatId},
+    data::adt::VariantData,
+    hir::{Pat, PatId},
     src::HasSource,
     AdtId, AttrDefId, ConstId, EnumId, FunctionId, ItemContainerId, Lookup, ModuleDefId, StaticId,
     StructId,

crates/hir-ty/src/diagnostics/expr.rs

@@ -27,7 +27,7 @@ use crate::{
 
 pub(crate) use hir_def::{
     body::Body,
-    expr::{Expr, ExprId, MatchArm, Pat, PatId},
+    hir::{Expr, ExprId, MatchArm, Pat, PatId},
     LocalFieldId, VariantId,
 };
 

crates/hir-ty/src/diagnostics/match_check.rs

@@ -1,6 +1,6 @@
 //! Validation of matches.
 //!
-//! This module provides lowering from [hir_def::expr::Pat] to [self::Pat] and match
+//! This module provides lowering from [hir_def::hir::Pat] to [self::Pat] and match
 //! checking algorithm.
 //!
 //! It is modeled on the rustc module `rustc_mir_build::thir::pattern`.
@@ -12,7 +12,7 @@ pub(crate) mod usefulness;
 
 use chalk_ir::Mutability;
 use hir_def::{
-    adt::VariantData, body::Body, expr::PatId, AdtId, EnumVariantId, LocalFieldId, VariantId,
+    body::Body, data::adt::VariantData, hir::PatId, AdtId, EnumVariantId, LocalFieldId, VariantId,
 };
 use hir_expand::name::Name;
 use stdx::{always, never};
@@ -125,15 +125,15 @@ impl<'a> PatCtxt<'a> {
         let variant = self.infer.variant_resolution_for_pat(pat);
 
         let kind = match self.body[pat] {
-            hir_def::expr::Pat::Wild => PatKind::Wild,
+            hir_def::hir::Pat::Wild => PatKind::Wild,
 
-            hir_def::expr::Pat::Lit(expr) => self.lower_lit(expr),
+            hir_def::hir::Pat::Lit(expr) => self.lower_lit(expr),
 
-            hir_def::expr::Pat::Path(ref path) => {
+            hir_def::hir::Pat::Path(ref path) => {
                 return self.lower_path(pat, path);
             }
 
-            hir_def::expr::Pat::Tuple { ref args, ellipsis } => {
+            hir_def::hir::Pat::Tuple { ref args, ellipsis } => {
                 let arity = match *ty.kind(Interner) {
                     TyKind::Tuple(arity, _) => arity,
                     _ => {
@@ -146,7 +146,7 @@ impl<'a> PatCtxt<'a> {
                 PatKind::Leaf { subpatterns }
             }
 
-            hir_def::expr::Pat::Bind { id, subpat, .. } => {
+            hir_def::hir::Pat::Bind { id, subpat, .. } => {
                 let bm = self.infer.pat_binding_modes[&pat];
                 let name = &self.body.bindings[id].name;
                 match (bm, ty.kind(Interner)) {
@@ -161,13 +161,13 @@ impl<'a> PatCtxt<'a> {
                 PatKind::Binding { name: name.clone(), subpattern: self.lower_opt_pattern(subpat) }
             }
 
-            hir_def::expr::Pat::TupleStruct { ref args, ellipsis, .. } if variant.is_some() => {
+            hir_def::hir::Pat::TupleStruct { ref args, ellipsis, .. } if variant.is_some() => {
                 let expected_len = variant.unwrap().variant_data(self.db.upcast()).fields().len();
                 let subpatterns = self.lower_tuple_subpats(args, expected_len, ellipsis);
                 self.lower_variant_or_leaf(pat, ty, subpatterns)
             }
 
-            hir_def::expr::Pat::Record { ref args, .. } if variant.is_some() => {
+            hir_def::hir::Pat::Record { ref args, .. } if variant.is_some() => {
                 let variant_data = variant.unwrap().variant_data(self.db.upcast());
                 let subpatterns = args
                     .iter()
@@ -187,12 +187,12 @@ impl<'a> PatCtxt<'a> {
                     }
                 }
             }
-            hir_def::expr::Pat::TupleStruct { .. } | hir_def::expr::Pat::Record { .. } => {
+            hir_def::hir::Pat::TupleStruct { .. } | hir_def::hir::Pat::Record { .. } => {
                 self.errors.push(PatternError::UnresolvedVariant);
                 PatKind::Wild
             }
 
-            hir_def::expr::Pat::Or(ref pats) => PatKind::Or { pats: self.lower_patterns(pats) },
+            hir_def::hir::Pat::Or(ref pats) => PatKind::Or { pats: self.lower_patterns(pats) },
 
             _ => {
                 self.errors.push(PatternError::Unimplemented);
@@ -279,8 +279,8 @@ impl<'a> PatCtxt<'a> {
         }
     }
 
-    fn lower_lit(&mut self, expr: hir_def::expr::ExprId) -> PatKind {
-        use hir_def::expr::{Expr, Literal::Bool};
+    fn lower_lit(&mut self, expr: hir_def::hir::ExprId) -> PatKind {
+        use hir_def::hir::{Expr, Literal::Bool};
 
         match self.body[expr] {
             Expr::Literal(Bool(value)) => PatKind::LiteralBool { value },

crates/hir-ty/src/diagnostics/unsafe_check.rs

@@ -3,7 +3,7 @@
 
 use hir_def::{
     body::Body,
-    expr::{Expr, ExprId, UnaryOp},
+    hir::{Expr, ExprId, UnaryOp},
     resolver::{resolver_for_expr, ResolveValueResult, ValueNs},
     DefWithBodyId,
 };

crates/hir-ty/src/display.rs

@@ -7,8 +7,8 @@ use std::fmt::{self, Debug};
 use base_db::CrateId;
 use chalk_ir::{BoundVar, TyKind};
 use hir_def::{
-    adt::VariantData,
     body,
+    data::adt::VariantData,
     db::DefDatabase,
     find_path,
     generics::{TypeOrConstParamData, TypeParamProvenance},
@@ -23,6 +23,7 @@ use hir_expand::{hygiene::Hygiene, name::Name};
 use intern::{Internable, Interned};
 use itertools::Itertools;
 use smallvec::SmallVec;
+use stdx::never;
 
 use crate::{
     db::HirDatabase,
@@ -64,6 +65,7 @@ pub struct HirFormatter<'a> {
     curr_size: usize,
     pub(crate) max_size: Option<usize>,
     omit_verbose_types: bool,
+    closure_style: ClosureStyle,
     display_target: DisplayTarget,
 }
 
@@ -87,6 +89,7 @@ pub trait HirDisplay {
         max_size: Option<usize>,
         omit_verbose_types: bool,
         display_target: DisplayTarget,
+        closure_style: ClosureStyle,
     ) -> HirDisplayWrapper<'a, Self>
     where
         Self: Sized,
@@ -95,7 +98,14 @@ pub trait HirDisplay {
             !matches!(display_target, DisplayTarget::SourceCode { .. }),
             "HirDisplayWrapper cannot fail with DisplaySourceCodeError, use HirDisplay::hir_fmt directly instead"
         );
-        HirDisplayWrapper { db, t: self, max_size, omit_verbose_types, display_target }
+        HirDisplayWrapper {
+            db,
+            t: self,
+            max_size,
+            omit_verbose_types,
+            display_target,
+            closure_style,
+        }
     }
 
     /// Returns a `Display`able type that is human-readable.
@@ -109,6 +119,7 @@ pub trait HirDisplay {
             t: self,
             max_size: None,
             omit_verbose_types: false,
+            closure_style: ClosureStyle::ImplFn,
             display_target: DisplayTarget::Diagnostics,
         }
     }
@@ -128,6 +139,7 @@ pub trait HirDisplay {
             t: self,
             max_size,
             omit_verbose_types: true,
+            closure_style: ClosureStyle::ImplFn,
             display_target: DisplayTarget::Diagnostics,
         }
     }
@@ -147,6 +159,7 @@ pub trait HirDisplay {
             curr_size: 0,
             max_size: None,
             omit_verbose_types: false,
+            closure_style: ClosureStyle::ImplFn,
             display_target: DisplayTarget::SourceCode { module_id },
         }) {
             Ok(()) => {}
@@ -166,6 +179,7 @@ pub trait HirDisplay {
             t: self,
             max_size: None,
             omit_verbose_types: false,
+            closure_style: ClosureStyle::ImplFn,
             display_target: DisplayTarget::Test,
         }
     }
@@ -253,7 +267,6 @@ impl DisplayTarget {
 pub enum DisplaySourceCodeError {
     PathNotFound,
     UnknownType,
-    Closure,
     Generator,
 }
 
@@ -274,9 +287,23 @@ pub struct HirDisplayWrapper<'a, T> {
     t: &'a T,
     max_size: Option<usize>,
     omit_verbose_types: bool,
+    closure_style: ClosureStyle,
     display_target: DisplayTarget,
 }
 
+#[derive(Debug, PartialEq, Eq, Clone, Copy)]
+pub enum ClosureStyle {
+    /// `impl FnX(i32, i32) -> i32`, where `FnX` is the most special trait between `Fn`, `FnMut`, `FnOnce` that the
+    /// closure implements. This is the default.
+    ImplFn,
+    /// `|i32, i32| -> i32`
+    RANotation,
+    /// `{closure#14825}`, useful for some diagnostics (like type mismatch) and internal usage.
+    ClosureWithId,
+    /// `…`, which is the `TYPE_HINT_TRUNCATION`
+    Hide,
+}
+
 impl<T: HirDisplay> HirDisplayWrapper<'_, T> {
     pub fn write_to<F: HirWrite>(&self, f: &mut F) -> Result<(), HirDisplayError> {
         self.t.hir_fmt(&mut HirFormatter {
@@ -287,8 +314,14 @@ impl<T: HirDisplay> HirDisplayWrapper<'_, T> {
             max_size: self.max_size,
             omit_verbose_types: self.omit_verbose_types,
             display_target: self.display_target,
+            closure_style: self.closure_style,
         })
     }
+
+    pub fn with_closure_style(mut self, c: ClosureStyle) -> Self {
+        self.closure_style = c;
+        self
+    }
 }
 
 impl<'a, T> fmt::Display for HirDisplayWrapper<'a, T>
@@ -919,26 +952,42 @@ impl HirDisplay for Ty {
                     }
                 }
             }
-            TyKind::Closure(.., substs) => {
-                if f.display_target.is_source_code() {
-                    return Err(HirDisplayError::DisplaySourceCodeError(
-                        DisplaySourceCodeError::Closure,
-                    ));
+            TyKind::Closure(id, substs) => {
+                if f.display_target.is_source_code() && f.closure_style != ClosureStyle::ImplFn {
+                    never!("Only `impl Fn` is valid for displaying closures in source code");
+                }
+                match f.closure_style {
+                    ClosureStyle::Hide => return write!(f, "{TYPE_HINT_TRUNCATION}"),
+                    ClosureStyle::ClosureWithId => {
+                        return write!(f, "{{closure#{:?}}}", id.0.as_u32())
+                    }
+                    _ => (),
                 }
                 let sig = substs.at(Interner, 0).assert_ty_ref(Interner).callable_sig(db);
                 if let Some(sig) = sig {
+                    let (def, _) = db.lookup_intern_closure((*id).into());
+                    let infer = db.infer(def);
+                    let (_, kind) = infer.closure_info(id);
+                    match f.closure_style {
+                        ClosureStyle::ImplFn => write!(f, "impl {kind:?}(")?,
+                        ClosureStyle::RANotation => write!(f, "|")?,
+                        _ => unreachable!(),
+                    }
                     if sig.params().is_empty() {
-                        write!(f, "||")?;
                     } else if f.should_truncate() {
-                        write!(f, "|{TYPE_HINT_TRUNCATION}|")?;
+                        write!(f, "{TYPE_HINT_TRUNCATION}")?;
                     } else {
-                        write!(f, "|")?;
                         f.write_joined(sig.params(), ", ")?;
-                        write!(f, "|")?;
                     };
-
-                    write!(f, " -> ")?;
-                    sig.ret().hir_fmt(f)?;
+                    match f.closure_style {
+                        ClosureStyle::ImplFn => write!(f, ")")?,
+                        ClosureStyle::RANotation => write!(f, "|")?,
+                        _ => unreachable!(),
+                    }
+                    if f.closure_style == ClosureStyle::RANotation || !sig.ret().is_unit() {
+                        write!(f, " -> ")?;
+                        sig.ret().hir_fmt(f)?;
+                    }
                 } else {
                     write!(f, "{{closure}}")?;
                 }

crates/hir-ty/src/infer.rs

@@ -18,11 +18,12 @@ use std::{convert::identity, ops::Index};
 
 use chalk_ir::{cast::Cast, DebruijnIndex, Mutability, Safety, Scalar, TypeFlags};
 use either::Either;
+use hir_def::hir::LabelId;
 use hir_def::{
     body::Body,
     builtin_type::{BuiltinInt, BuiltinType, BuiltinUint},
     data::{ConstData, StaticData},
-    expr::{BindingAnnotation, BindingId, ExprId, ExprOrPatId, PatId},
+    hir::{BindingAnnotation, BindingId, ExprId, ExprOrPatId, PatId},
     lang_item::{LangItem, LangItemTarget},
     layout::Integer,
     path::{ModPath, Path},
@@ -32,15 +33,15 @@ use hir_def::{
     TraitId, TypeAliasId, VariantId,
 };
 use hir_expand::name::{name, Name};
-use la_arena::ArenaMap;
+use la_arena::{ArenaMap, Entry};
 use rustc_hash::{FxHashMap, FxHashSet};
 use stdx::{always, never};
 
 use crate::{
     db::HirDatabase, fold_tys, infer::coerce::CoerceMany, lower::ImplTraitLoweringMode,
-    static_lifetime, to_assoc_type_id, AliasEq, AliasTy, DomainGoal, GenericArg, Goal, ImplTraitId,
-    InEnvironment, Interner, ProjectionTy, RpitId, Substitution, TraitRef, Ty, TyBuilder, TyExt,
-    TyKind,
+    static_lifetime, to_assoc_type_id, traits::FnTrait, AliasEq, AliasTy, ClosureId, DomainGoal,
+    GenericArg, Goal, ImplTraitId, InEnvironment, Interner, ProjectionTy, RpitId, Substitution,
+    TraitRef, Ty, TyBuilder, TyExt, TyKind,
 };
 
 // This lint has a false positive here. See the link below for details.
@@ -51,6 +52,8 @@ pub use coerce::could_coerce;
 #[allow(unreachable_pub)]
 pub use unify::could_unify;
 
+pub(crate) use self::closure::{CaptureKind, CapturedItem, CapturedItemWithoutTy};
+
 pub(crate) mod unify;
 mod path;
 mod expr;
@@ -102,6 +105,8 @@ pub(crate) fn infer_query(db: &dyn HirDatabase, def: DefWithBodyId) -> Arc<Infer
 
     ctx.infer_mut_body();
 
+    ctx.infer_closures();
+
     Arc::new(ctx.resolve_all())
 }
 
@@ -188,7 +193,7 @@ pub enum InferenceDiagnostic {
         /// Contains the type the field resolves to
         field_with_same_name: Option<Ty>,
     },
-    // FIXME: Make this proper
+    // FIXME: This should be emitted in body lowering
     BreakOutsideOfLoop {
         expr: ExprId,
         is_break: bool,
@@ -311,6 +316,13 @@ pub enum AutoBorrow {
     RawPtr(Mutability),
 }
 
+impl AutoBorrow {
+    fn mutability(self) -> Mutability {
+        let (AutoBorrow::Ref(m) | AutoBorrow::RawPtr(m)) = self;
+        m
+    }
+}
+
 #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
 pub enum PointerCast {
     /// Go from a fn-item type to a fn-pointer type.
@@ -372,6 +384,9 @@ pub struct InferenceResult {
     pub pat_adjustments: FxHashMap<PatId, Vec<Ty>>,
     pub pat_binding_modes: FxHashMap<PatId, BindingMode>,
     pub expr_adjustments: FxHashMap<ExprId, Vec<Adjustment>>,
+    pub(crate) closure_info: FxHashMap<ClosureId, (Vec<CapturedItem>, FnTrait)>,
+    // FIXME: remove this field
+    pub mutated_bindings_in_closure: FxHashSet<BindingId>,
 }
 
 impl InferenceResult {
@@ -408,6 +423,9 @@ impl InferenceResult {
             _ => None,
         })
     }
+    pub(crate) fn closure_info(&self, closure: &ClosureId) -> &(Vec<CapturedItem>, FnTrait) {
+        self.closure_info.get(closure).unwrap()
+    }
 }
 
 impl Index<ExprId> for InferenceResult {
@@ -459,6 +477,14 @@ pub(crate) struct InferenceContext<'a> {
     resume_yield_tys: Option<(Ty, Ty)>,
     diverges: Diverges,
     breakables: Vec<BreakableContext>,
+
+    // fields related to closure capture
+    current_captures: Vec<CapturedItemWithoutTy>,
+    current_closure: Option<ClosureId>,
+    /// Stores the list of closure ids that need to be analyzed before this closure. See the
+    /// comment on `InferenceContext::sort_closures`
+    closure_dependecies: FxHashMap<ClosureId, Vec<ClosureId>>,
+    deferred_closures: FxHashMap<ClosureId, Vec<(Ty, Ty, Vec<Ty>, ExprId)>>,
 }
 
 #[derive(Clone, Debug)]
@@ -468,7 +494,7 @@ struct BreakableContext {
     /// The coercion target of the context.
     coerce: Option<CoerceMany>,
     /// The optional label of the context.
-    label: Option<name::Name>,
+    label: Option<LabelId>,
     kind: BreakableKind,
 }
 
@@ -483,21 +509,21 @@ enum BreakableKind {
 
 fn find_breakable<'c>(
     ctxs: &'c mut [BreakableContext],
-    label: Option<&name::Name>,
+    label: Option<LabelId>,
 ) -> Option<&'c mut BreakableContext> {
     let mut ctxs = ctxs
         .iter_mut()
         .rev()
         .take_while(|it| matches!(it.kind, BreakableKind::Block | BreakableKind::Loop));
     match label {
-        Some(_) => ctxs.find(|ctx| ctx.label.as_ref() == label),
+        Some(_) => ctxs.find(|ctx| ctx.label == label),
         None => ctxs.find(|ctx| matches!(ctx.kind, BreakableKind::Loop)),
     }
 }
 
 fn find_continuable<'c>(
     ctxs: &'c mut [BreakableContext],
-    label: Option<&name::Name>,
+    label: Option<LabelId>,
 ) -> Option<&'c mut BreakableContext> {
     match label {
         Some(_) => find_breakable(ctxs, label).filter(|it| matches!(it.kind, BreakableKind::Loop)),
@@ -526,6 +552,10 @@ impl<'a> InferenceContext<'a> {
             resolver,
             diverges: Diverges::Maybe,
             breakables: Vec::new(),
+            current_captures: vec![],
+            current_closure: None,
+            deferred_closures: FxHashMap::default(),
+            closure_dependecies: FxHashMap::default(),
         }
     }
 
@@ -617,7 +647,7 @@ impl<'a> InferenceContext<'a> {
         let ctx = crate::lower::TyLoweringContext::new(self.db, &self.resolver)
             .with_impl_trait_mode(ImplTraitLoweringMode::Param);
         let mut param_tys =
-            data.params.iter().map(|(_, type_ref)| ctx.lower_ty(type_ref)).collect::<Vec<_>>();
+            data.params.iter().map(|type_ref| ctx.lower_ty(type_ref)).collect::<Vec<_>>();
         // Check if function contains a va_list, if it does then we append it to the parameter types
         // that are collected from the function data
         if data.is_varargs() {
@@ -646,36 +676,16 @@ impl<'a> InferenceContext<'a> {
         let return_ty = if let Some(rpits) = self.db.return_type_impl_traits(func) {
             // RPIT opaque types use substitution of their parent function.
             let fn_placeholders = TyBuilder::placeholder_subst(self.db, func);
-            fold_tys(
-                return_ty,
-                |ty, _| {
-                    let opaque_ty_id = match ty.kind(Interner) {
-                        TyKind::OpaqueType(opaque_ty_id, _) => *opaque_ty_id,
-                        _ => return ty,
-                    };
-                    let idx = match self.db.lookup_intern_impl_trait_id(opaque_ty_id.into()) {
-                        ImplTraitId::ReturnTypeImplTrait(_, idx) => idx,
-                        _ => unreachable!(),
-                    };
-                    let bounds = (*rpits).map_ref(|rpits| {
-                        rpits.impl_traits[idx].bounds.map_ref(|it| it.into_iter())
-                    });
-                    let var = self.table.new_type_var();
-                    let var_subst = Substitution::from1(Interner, var.clone());
-                    for bound in bounds {
-                        let predicate =
-                            bound.map(|it| it.cloned()).substitute(Interner, &fn_placeholders);
-                        let (var_predicate, binders) = predicate
-                            .substitute(Interner, &var_subst)
-                            .into_value_and_skipped_binders();
-                        always!(binders.is_empty(Interner)); // quantified where clauses not yet handled
-                        self.push_obligation(var_predicate.cast(Interner));
-                    }
-                    self.result.type_of_rpit.insert(idx, var.clone());
-                    var
-                },
-                DebruijnIndex::INNERMOST,
-            )
+            let result =
+                self.insert_inference_vars_for_rpit(return_ty, rpits.clone(), fn_placeholders);
+            let rpits = rpits.skip_binders();
+            for (id, _) in rpits.impl_traits.iter() {
+                if let Entry::Vacant(e) = self.result.type_of_rpit.entry(id) {
+                    never!("Missed RPIT in `insert_inference_vars_for_rpit`");
+                    e.insert(TyKind::Error.intern(Interner));
+                }
+            }
+            result
         } else {
             return_ty
         };
@@ -684,6 +694,50 @@ impl<'a> InferenceContext<'a> {
         self.return_coercion = Some(CoerceMany::new(self.return_ty.clone()));
     }
 
+    fn insert_inference_vars_for_rpit<T>(
+        &mut self,
+        t: T,
+        rpits: Arc<chalk_ir::Binders<crate::ReturnTypeImplTraits>>,
+        fn_placeholders: Substitution,
+    ) -> T
+    where
+        T: crate::HasInterner<Interner = Interner> + crate::TypeFoldable<Interner>,
+    {
+        fold_tys(
+            t,
+            |ty, _| {
+                let opaque_ty_id = match ty.kind(Interner) {
+                    TyKind::OpaqueType(opaque_ty_id, _) => *opaque_ty_id,
+                    _ => return ty,
+                };
+                let idx = match self.db.lookup_intern_impl_trait_id(opaque_ty_id.into()) {
+                    ImplTraitId::ReturnTypeImplTrait(_, idx) => idx,
+                    _ => unreachable!(),
+                };
+                let bounds = (*rpits)
+                    .map_ref(|rpits| rpits.impl_traits[idx].bounds.map_ref(|it| it.into_iter()));
+                let var = self.table.new_type_var();
+                let var_subst = Substitution::from1(Interner, var.clone());
+                for bound in bounds {
+                    let predicate =
+                        bound.map(|it| it.cloned()).substitute(Interner, &fn_placeholders);
+                    let (var_predicate, binders) =
+                        predicate.substitute(Interner, &var_subst).into_value_and_skipped_binders();
+                    always!(binders.is_empty(Interner)); // quantified where clauses not yet handled
+                    let var_predicate = self.insert_inference_vars_for_rpit(
+                        var_predicate,
+                        rpits.clone(),
+                        fn_placeholders.clone(),
+                    );
+                    self.push_obligation(var_predicate.cast(Interner));
+                }
+                self.result.type_of_rpit.insert(idx, var.clone());
+                var
+            },
+            DebruijnIndex::INNERMOST,
+        )
+    }
+
     fn infer_body(&mut self) {
         match self.return_coercion {
             Some(_) => self.infer_return(self.body.body_expr),

crates/hir-ty/src/infer/closure.rs

@@ -1,12 +1,29 @@
 //! Inference of closure parameter types based on the closure's expected type.
 
-use chalk_ir::{cast::Cast, AliasEq, AliasTy, FnSubst, WhereClause};
-use hir_def::{expr::ExprId, HasModule};
+use std::{cmp, collections::HashMap, convert::Infallible, mem};
+
+use chalk_ir::{cast::Cast, AliasEq, AliasTy, FnSubst, Mutability, TyKind, WhereClause};
+use hir_def::{
+    hir::{
+        Array, BinaryOp, BindingAnnotation, BindingId, CaptureBy, Expr, ExprId, Pat, PatId,
+        Statement, UnaryOp,
+    },
+    lang_item::LangItem,
+    resolver::{resolver_for_expr, ResolveValueResult, ValueNs},
+    FieldId, HasModule, VariantId,
+};
+use hir_expand::name;
+use rustc_hash::FxHashMap;
 use smallvec::SmallVec;
+use stdx::never;
 
 use crate::{
-    to_chalk_trait_id, utils, ChalkTraitId, DynTy, FnPointer, FnSig, Interner, Substitution, Ty,
-    TyExt, TyKind,
+    mir::{BorrowKind, ProjectionElem},
+    static_lifetime, to_chalk_trait_id,
+    traits::FnTrait,
+    utils::{self, pattern_matching_dereference_count},
+    Adjust, Adjustment, Canonical, CanonicalVarKinds, ChalkTraitId, ClosureId, DynTy, FnPointer,
+    FnSig, InEnvironment, Interner, Substitution, Ty, TyBuilder, TyExt,
 };
 
 use super::{Expectation, InferenceContext};
@@ -86,3 +103,700 @@ impl InferenceContext<'_> {
         None
     }
 }
+
+// The below functions handle capture and closure kind (Fn, FnMut, ..)
+
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub(crate) struct HirPlace {
+    pub(crate) local: BindingId,
+    pub(crate) projections: Vec<ProjectionElem<Infallible, Ty>>,
+}
+impl HirPlace {
+    fn ty(&self, ctx: &mut InferenceContext<'_>) -> Ty {
+        let mut ty = ctx.table.resolve_completely(ctx.result[self.local].clone());
+        for p in &self.projections {
+            ty = p.projected_ty(ty, ctx.db, |_, _| {
+                unreachable!("Closure field only happens in MIR");
+            });
+        }
+        ty.clone()
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
+pub(crate) enum CaptureKind {
+    ByRef(BorrowKind),
+    ByValue,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub(crate) struct CapturedItem {
+    pub(crate) place: HirPlace,
+    pub(crate) kind: CaptureKind,
+    pub(crate) ty: Ty,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub(crate) struct CapturedItemWithoutTy {
+    pub(crate) place: HirPlace,
+    pub(crate) kind: CaptureKind,
+}
+
+impl CapturedItemWithoutTy {
+    fn with_ty(self, ctx: &mut InferenceContext<'_>) -> CapturedItem {
+        let ty = self.place.ty(ctx).clone();
+        let ty = match &self.kind {
+            CaptureKind::ByValue => ty,
+            CaptureKind::ByRef(bk) => {
+                let m = match bk {
+                    BorrowKind::Mut { .. } => Mutability::Mut,
+                    _ => Mutability::Not,
+                };
+                TyKind::Ref(m, static_lifetime(), ty).intern(Interner)
+            }
+        };
+        CapturedItem { place: self.place, kind: self.kind, ty }
+    }
+}
+
+impl InferenceContext<'_> {
+    fn place_of_expr(&mut self, tgt_expr: ExprId) -> Option<HirPlace> {
+        let r = self.place_of_expr_without_adjust(tgt_expr)?;
+        let default = vec![];
+        let adjustments = self.result.expr_adjustments.get(&tgt_expr).unwrap_or(&default);
+        apply_adjusts_to_place(r, adjustments)
+    }
+
+    fn place_of_expr_without_adjust(&mut self, tgt_expr: ExprId) -> Option<HirPlace> {
+        match &self.body[tgt_expr] {
+            Expr::Path(p) => {
+                let resolver = resolver_for_expr(self.db.upcast(), self.owner, tgt_expr);
+                if let Some(r) = resolver.resolve_path_in_value_ns(self.db.upcast(), p) {
+                    if let ResolveValueResult::ValueNs(v) = r {
+                        if let ValueNs::LocalBinding(b) = v {
+                            return Some(HirPlace { local: b, projections: vec![] });
+                        }
+                    }
+                }
+            }
+            Expr::Field { expr, name } => {
+                let mut place = self.place_of_expr(*expr)?;
+                if let TyKind::Tuple(..) = self.expr_ty(*expr).kind(Interner) {
+                    let index = name.as_tuple_index()?;
+                    place.projections.push(ProjectionElem::TupleOrClosureField(index))
+                } else {
+                    let field = self.result.field_resolution(tgt_expr)?;
+                    place.projections.push(ProjectionElem::Field(field));
+                }
+                return Some(place);
+            }
+            _ => (),
+        }
+        None
+    }
+
+    fn push_capture(&mut self, capture: CapturedItemWithoutTy) {
+        self.current_captures.push(capture);
+    }
+
+    fn ref_expr(&mut self, expr: ExprId) {
+        if let Some(place) = self.place_of_expr(expr) {
+            self.add_capture(place, CaptureKind::ByRef(BorrowKind::Shared));
+        }
+        self.walk_expr(expr);
+    }
+
+    fn add_capture(&mut self, place: HirPlace, kind: CaptureKind) {
+        if self.is_upvar(&place) {
+            self.push_capture(CapturedItemWithoutTy { place, kind });
+        }
+    }
+
+    fn mutate_expr(&mut self, expr: ExprId) {
+        if let Some(place) = self.place_of_expr(expr) {
+            self.add_capture(
+                place,
+                CaptureKind::ByRef(BorrowKind::Mut { allow_two_phase_borrow: false }),
+            );
+        }
+        self.walk_expr(expr);
+    }
+
+    fn consume_expr(&mut self, expr: ExprId) {
+        if let Some(place) = self.place_of_expr(expr) {
+            self.consume_place(place);
+        }
+        self.walk_expr(expr);
+    }
+
+    fn consume_place(&mut self, place: HirPlace) {
+        if self.is_upvar(&place) {
+            let ty = place.ty(self).clone();
+            let kind = if self.is_ty_copy(ty) {
+                CaptureKind::ByRef(BorrowKind::Shared)
+            } else {
+                CaptureKind::ByValue
+            };
+            self.push_capture(CapturedItemWithoutTy { place, kind });
+        }
+    }
+
+    fn walk_expr_with_adjust(&mut self, tgt_expr: ExprId, adjustment: &[Adjustment]) {
+        if let Some((last, rest)) = adjustment.split_last() {
+            match last.kind {
+                Adjust::NeverToAny | Adjust::Deref(None) | Adjust::Pointer(_) => {
+                    self.walk_expr_with_adjust(tgt_expr, rest)
+                }
+                Adjust::Deref(Some(m)) => match m.0 {
+                    Some(m) => {
+                        self.ref_capture_with_adjusts(m, tgt_expr, rest);
+                    }
+                    None => unreachable!(),
+                },
+                Adjust::Borrow(b) => {
+                    self.ref_capture_with_adjusts(b.mutability(), tgt_expr, rest);
+                }
+            }
+        } else {
+            self.walk_expr_without_adjust(tgt_expr);
+        }
+    }
+
+    fn ref_capture_with_adjusts(&mut self, m: Mutability, tgt_expr: ExprId, rest: &[Adjustment]) {
+        let capture_kind = match m {
+            Mutability::Mut => {
+                CaptureKind::ByRef(BorrowKind::Mut { allow_two_phase_borrow: false })
+            }
+            Mutability::Not => CaptureKind::ByRef(BorrowKind::Shared),
+        };
+        if let Some(place) = self.place_of_expr_without_adjust(tgt_expr) {
+            if let Some(place) = apply_adjusts_to_place(place, rest) {
+                if self.is_upvar(&place) {
+                    self.push_capture(CapturedItemWithoutTy { place, kind: capture_kind });
+                }
+            }
+        }
+        self.walk_expr_with_adjust(tgt_expr, rest);
+    }
+
+    fn walk_expr(&mut self, tgt_expr: ExprId) {
+        if let Some(x) = self.result.expr_adjustments.get_mut(&tgt_expr) {
+            // FIXME: this take is completely unneeded, and just is here to make borrow checker
+            // happy. Remove it if you can.
+            let x_taken = mem::take(x);
+            self.walk_expr_with_adjust(tgt_expr, &x_taken);
+            *self.result.expr_adjustments.get_mut(&tgt_expr).unwrap() = x_taken;
+        } else {
+            self.walk_expr_without_adjust(tgt_expr);
+        }
+    }
+
+    fn walk_expr_without_adjust(&mut self, tgt_expr: ExprId) {
+        match &self.body[tgt_expr] {
+            Expr::If { condition, then_branch, else_branch } => {
+                self.consume_expr(*condition);
+                self.consume_expr(*then_branch);
+                if let &Some(expr) = else_branch {
+                    self.consume_expr(expr);
+                }
+            }
+            Expr::Async { statements, tail, .. }
+            | Expr::Const { statements, tail, .. }
+            | Expr::Unsafe { statements, tail, .. }
+            | Expr::Block { statements, tail, .. } => {
+                for s in statements.iter() {
+                    match s {
+                        Statement::Let { pat, type_ref: _, initializer, else_branch } => {
+                            if let Some(else_branch) = else_branch {
+                                self.consume_expr(*else_branch);
+                                if let Some(initializer) = initializer {
+                                    self.consume_expr(*initializer);
+                                }
+                                return;
+                            }
+                            if let Some(initializer) = initializer {
+                                self.walk_expr(*initializer);
+                                if let Some(place) = self.place_of_expr(*initializer) {
+                                    let ty = self.expr_ty(*initializer);
+                                    self.consume_with_pat(
+                                        place,
+                                        ty,
+                                        BindingAnnotation::Unannotated,
+                                        *pat,
+                                    );
+                                }
+                            }
+                        }
+                        Statement::Expr { expr, has_semi: _ } => {
+                            self.consume_expr(*expr);
+                        }
+                    }
+                }
+                if let Some(tail) = tail {
+                    self.consume_expr(*tail);
+                }
+            }
+            Expr::While { condition, body, label: _ }
+            | Expr::For { iterable: condition, pat: _, body, label: _ } => {
+                self.consume_expr(*condition);
+                self.consume_expr(*body);
+            }
+            Expr::Call { callee, args, is_assignee_expr: _ } => {
+                self.consume_expr(*callee);
+                self.consume_exprs(args.iter().copied());
+            }
+            Expr::MethodCall { receiver, args, .. } => {
+                self.consume_expr(*receiver);
+                self.consume_exprs(args.iter().copied());
+            }
+            Expr::Match { expr, arms } => {
+                self.consume_expr(*expr);
+                for arm in arms.iter() {
+                    self.consume_expr(arm.expr);
+                }
+            }
+            Expr::Break { expr, label: _ }
+            | Expr::Return { expr }
+            | Expr::Yield { expr }
+            | Expr::Yeet { expr } => {
+                if let &Some(expr) = expr {
+                    self.consume_expr(expr);
+                }
+            }
+            Expr::RecordLit { fields, spread, .. } => {
+                if let &Some(expr) = spread {
+                    self.consume_expr(expr);
+                }
+                self.consume_exprs(fields.iter().map(|x| x.expr));
+            }
+            Expr::Field { expr, name: _ } => self.select_from_expr(*expr),
+            Expr::UnaryOp { expr, op: UnaryOp::Deref } => {
+                if let Some((f, _)) = self.result.method_resolution(tgt_expr) {
+                    let mutability = 'b: {
+                        if let Some(deref_trait) =
+                            self.resolve_lang_item(LangItem::DerefMut).and_then(|x| x.as_trait())
+                        {
+                            if let Some(deref_fn) =
+                                self.db.trait_data(deref_trait).method_by_name(&name![deref_mut])
+                            {
+                                break 'b deref_fn == f;
+                            }
+                        }
+                        false
+                    };
+                    if mutability {
+                        self.mutate_expr(*expr);
+                    } else {
+                        self.ref_expr(*expr);
+                    }
+                } else {
+                    self.select_from_expr(*expr);
+                }
+            }
+            Expr::UnaryOp { expr, op: _ }
+            | Expr::Array(Array::Repeat { initializer: expr, repeat: _ })
+            | Expr::Await { expr }
+            | Expr::Loop { body: expr, label: _ }
+            | Expr::Let { pat: _, expr }
+            | Expr::Box { expr }
+            | Expr::Cast { expr, type_ref: _ } => {
+                self.consume_expr(*expr);
+            }
+            Expr::Ref { expr, rawness: _, mutability } => match mutability {
+                hir_def::type_ref::Mutability::Shared => self.ref_expr(*expr),
+                hir_def::type_ref::Mutability::Mut => self.mutate_expr(*expr),
+            },
+            Expr::BinaryOp { lhs, rhs, op } => {
+                let Some(op) = op else {
+                    return;
+                };
+                if matches!(op, BinaryOp::Assignment { .. }) {
+                    self.mutate_expr(*lhs);
+                    self.consume_expr(*rhs);
+                    return;
+                }
+                self.consume_expr(*lhs);
+                self.consume_expr(*rhs);
+            }
+            Expr::Range { lhs, rhs, range_type: _ } => {
+                if let &Some(expr) = lhs {
+                    self.consume_expr(expr);
+                }
+                if let &Some(expr) = rhs {
+                    self.consume_expr(expr);
+                }
+            }
+            Expr::Index { base, index } => {
+                self.select_from_expr(*base);
+                self.consume_expr(*index);
+            }
+            Expr::Closure { .. } => {
+                let ty = self.expr_ty(tgt_expr);
+                let TyKind::Closure(id, _) = ty.kind(Interner) else {
+                    never!("closure type is always closure");
+                    return;
+                };
+                let (captures, _) =
+                    self.result.closure_info.get(id).expect(
+                        "We sort closures, so we should always have data for inner closures",
+                    );
+                let mut cc = mem::take(&mut self.current_captures);
+                cc.extend(
+                    captures
+                        .iter()
+                        .filter(|x| self.is_upvar(&x.place))
+                        .map(|x| CapturedItemWithoutTy { place: x.place.clone(), kind: x.kind }),
+                );
+                self.current_captures = cc;
+            }
+            Expr::Array(Array::ElementList { elements: exprs, is_assignee_expr: _ })
+            | Expr::Tuple { exprs, is_assignee_expr: _ } => {
+                self.consume_exprs(exprs.iter().copied())
+            }
+            Expr::Missing
+            | Expr::Continue { .. }
+            | Expr::Path(_)
+            | Expr::Literal(_)
+            | Expr::Underscore => (),
+        }
+    }
+
+    fn expr_ty(&mut self, expr: ExprId) -> Ty {
+        self.result[expr].clone()
+    }
+
+    fn is_upvar(&self, place: &HirPlace) -> bool {
+        let b = &self.body[place.local];
+        if let Some(c) = self.current_closure {
+            let (_, root) = self.db.lookup_intern_closure(c.into());
+            return b.is_upvar(root);
+        }
+        false
+    }
+
+    fn is_ty_copy(&self, ty: Ty) -> bool {
+        if let TyKind::Closure(id, _) = ty.kind(Interner) {
+            // FIXME: We handle closure as a special case, since chalk consider every closure as copy. We
+            // should probably let chalk know which closures are copy, but I don't know how doing it
+            // without creating query cycles.
+            return self.result.closure_info.get(id).map(|x| x.1 == FnTrait::Fn).unwrap_or(true);
+        }
+        let crate_id = self.owner.module(self.db.upcast()).krate();
+        let Some(copy_trait) = self.db.lang_item(crate_id, LangItem::Copy).and_then(|x| x.as_trait()) else {
+            return false;
+        };
+        let trait_ref = TyBuilder::trait_ref(self.db, copy_trait).push(ty).build();
+        let env = self.db.trait_environment_for_body(self.owner);
+        let goal = Canonical {
+            value: InEnvironment::new(&env.env, trait_ref.cast(Interner)),
+            binders: CanonicalVarKinds::empty(Interner),
+        };
+        self.db.trait_solve(crate_id, None, goal).is_some()
+    }
+
+    fn select_from_expr(&mut self, expr: ExprId) {
+        self.walk_expr(expr);
+    }
+
+    fn adjust_for_move_closure(&mut self) {
+        for capture in &mut self.current_captures {
+            if let Some(first_deref) =
+                capture.place.projections.iter().position(|proj| *proj == ProjectionElem::Deref)
+            {
+                capture.place.projections.truncate(first_deref);
+            }
+            capture.kind = CaptureKind::ByValue;
+        }
+    }
+
+    fn minimize_captures(&mut self) {
+        self.current_captures.sort_by_key(|x| x.place.projections.len());
+        let mut hash_map = HashMap::<HirPlace, usize>::new();
+        let result = mem::take(&mut self.current_captures);
+        for item in result {
+            let mut lookup_place = HirPlace { local: item.place.local, projections: vec![] };
+            let mut it = item.place.projections.iter();
+            let prev_index = loop {
+                if let Some(k) = hash_map.get(&lookup_place) {
+                    break Some(*k);
+                }
+                match it.next() {
+                    Some(x) => lookup_place.projections.push(x.clone()),
+                    None => break None,
+                }
+            };
+            match prev_index {
+                Some(p) => {
+                    self.current_captures[p].kind =
+                        cmp::max(item.kind, self.current_captures[p].kind);
+                }
+                None => {
+                    hash_map.insert(item.place.clone(), self.current_captures.len());
+                    self.current_captures.push(item);
+                }
+            }
+        }
+    }
+
+    fn consume_with_pat(
+        &mut self,
+        mut place: HirPlace,
+        mut ty: Ty,
+        mut bm: BindingAnnotation,
+        pat: PatId,
+    ) {
+        match &self.body[pat] {
+            Pat::Missing | Pat::Wild => (),
+            Pat::Tuple { args, ellipsis } => {
+                pattern_matching_dereference(&mut ty, &mut bm, &mut place);
+                let (al, ar) = args.split_at(ellipsis.unwrap_or(args.len()));
+                let subst = match ty.kind(Interner) {
+                    TyKind::Tuple(_, s) => s,
+                    _ => return,
+                };
+                let fields = subst.iter(Interner).map(|x| x.assert_ty_ref(Interner)).enumerate();
+                let it = al.iter().zip(fields.clone()).chain(ar.iter().rev().zip(fields.rev()));
+                for (arg, (i, ty)) in it {
+                    let mut p = place.clone();
+                    p.projections.push(ProjectionElem::TupleOrClosureField(i));
+                    self.consume_with_pat(p, ty.clone(), bm, *arg);
+                }
+            }
+            Pat::Or(pats) => {
+                for pat in pats.iter() {
+                    self.consume_with_pat(place.clone(), ty.clone(), bm, *pat);
+                }
+            }
+            Pat::Record { args, .. } => {
+                pattern_matching_dereference(&mut ty, &mut bm, &mut place);
+                let subst = match ty.kind(Interner) {
+                    TyKind::Adt(_, s) => s,
+                    _ => return,
+                };
+                let Some(variant) = self.result.variant_resolution_for_pat(pat) else {
+                    return;
+                };
+                match variant {
+                    VariantId::EnumVariantId(_) | VariantId::UnionId(_) => {
+                        self.consume_place(place)
+                    }
+                    VariantId::StructId(s) => {
+                        let vd = &*self.db.struct_data(s).variant_data;
+                        let field_types = self.db.field_types(variant);
+                        for field_pat in args.iter() {
+                            let arg = field_pat.pat;
+                            let Some(local_id) = vd.field(&field_pat.name) else {
+                                continue;
+                            };
+                            let mut p = place.clone();
+                            p.projections.push(ProjectionElem::Field(FieldId {
+                                parent: variant.into(),
+                                local_id,
+                            }));
+                            self.consume_with_pat(
+                                p,
+                                field_types[local_id].clone().substitute(Interner, subst),
+                                bm,
+                                arg,
+                            );
+                        }
+                    }
+                }
+            }
+            Pat::Range { .. }
+            | Pat::Slice { .. }
+            | Pat::ConstBlock(_)
+            | Pat::Path(_)
+            | Pat::Lit(_) => self.consume_place(place),
+            Pat::Bind { id, subpat: _ } => {
+                let mode = self.body.bindings[*id].mode;
+                if matches!(mode, BindingAnnotation::Ref | BindingAnnotation::RefMut) {
+                    bm = mode;
+                }
+                let capture_kind = match bm {
+                    BindingAnnotation::Unannotated | BindingAnnotation::Mutable => {
+                        self.consume_place(place);
+                        return;
+                    }
+                    BindingAnnotation::Ref => BorrowKind::Shared,
+                    BindingAnnotation::RefMut => BorrowKind::Mut { allow_two_phase_borrow: false },
+                };
+                self.add_capture(place, CaptureKind::ByRef(capture_kind));
+            }
+            Pat::TupleStruct { path: _, args, ellipsis } => {
+                pattern_matching_dereference(&mut ty, &mut bm, &mut place);
+                let subst = match ty.kind(Interner) {
+                    TyKind::Adt(_, s) => s,
+                    _ => return,
+                };
+                let Some(variant) = self.result.variant_resolution_for_pat(pat) else {
+                    return;
+                };
+                match variant {
+                    VariantId::EnumVariantId(_) | VariantId::UnionId(_) => {
+                        self.consume_place(place)
+                    }
+                    VariantId::StructId(s) => {
+                        let vd = &*self.db.struct_data(s).variant_data;
+                        let (al, ar) = args.split_at(ellipsis.unwrap_or(args.len()));
+                        let fields = vd.fields().iter();
+                        let it =
+                            al.iter().zip(fields.clone()).chain(ar.iter().rev().zip(fields.rev()));
+                        let field_types = self.db.field_types(variant);
+                        for (arg, (i, _)) in it {
+                            let mut p = place.clone();
+                            p.projections.push(ProjectionElem::Field(FieldId {
+                                parent: variant.into(),
+                                local_id: i,
+                            }));
+                            self.consume_with_pat(
+                                p,
+                                field_types[i].clone().substitute(Interner, subst),
+                                bm,
+                                *arg,
+                            );
+                        }
+                    }
+                }
+            }
+            Pat::Ref { pat, mutability: _ } => {
+                if let Some((inner, _, _)) = ty.as_reference() {
+                    ty = inner.clone();
+                    place.projections.push(ProjectionElem::Deref);
+                    self.consume_with_pat(place, ty, bm, *pat)
+                }
+            }
+            Pat::Box { .. } => (), // not supported
+        }
+    }
+
+    fn consume_exprs(&mut self, exprs: impl Iterator<Item = ExprId>) {
+        for expr in exprs {
+            self.consume_expr(expr);
+        }
+    }
+
+    fn closure_kind(&self) -> FnTrait {
+        let mut r = FnTrait::Fn;
+        for x in &self.current_captures {
+            r = cmp::min(
+                r,
+                match &x.kind {
+                    CaptureKind::ByRef(BorrowKind::Unique | BorrowKind::Mut { .. }) => {
+                        FnTrait::FnMut
+                    }
+                    CaptureKind::ByRef(BorrowKind::Shallow | BorrowKind::Shared) => FnTrait::Fn,
+                    CaptureKind::ByValue => FnTrait::FnOnce,
+                },
+            )
+        }
+        r
+    }
+
+    fn analyze_closure(&mut self, closure: ClosureId) -> FnTrait {
+        let (_, root) = self.db.lookup_intern_closure(closure.into());
+        self.current_closure = Some(closure);
+        let Expr::Closure { body, capture_by, .. } = &self.body[root] else {
+            unreachable!("Closure expression id is always closure");
+        };
+        self.consume_expr(*body);
+        for item in &self.current_captures {
+            if matches!(item.kind, CaptureKind::ByRef(BorrowKind::Mut { .. })) {
+                // FIXME: remove the `mutated_bindings_in_closure` completely and add proper fake reads in
+                // MIR. I didn't do that due duplicate diagnostics.
+                self.result.mutated_bindings_in_closure.insert(item.place.local);
+            }
+        }
+        // closure_kind should be done before adjust_for_move_closure
+        let closure_kind = self.closure_kind();
+        match capture_by {
+            CaptureBy::Value => self.adjust_for_move_closure(),
+            CaptureBy::Ref => (),
+        }
+        self.minimize_captures();
+        let result = mem::take(&mut self.current_captures);
+        let captures = result.into_iter().map(|x| x.with_ty(self)).collect::<Vec<_>>();
+        self.result.closure_info.insert(closure, (captures, closure_kind));
+        closure_kind
+    }
+
+    pub(crate) fn infer_closures(&mut self) {
+        let deferred_closures = self.sort_closures();
+        for (closure, exprs) in deferred_closures.into_iter().rev() {
+            self.current_captures = vec![];
+            let kind = self.analyze_closure(closure);
+
+            for (derefed_callee, callee_ty, params, expr) in exprs {
+                if let &Expr::Call { callee, .. } = &self.body[expr] {
+                    let mut adjustments =
+                        self.result.expr_adjustments.remove(&callee).unwrap_or_default();
+                    self.write_fn_trait_method_resolution(
+                        kind,
+                        &derefed_callee,
+                        &mut adjustments,
+                        &callee_ty,
+                        &params,
+                        expr,
+                    );
+                    self.result.expr_adjustments.insert(callee, adjustments);
+                }
+            }
+        }
+    }
+
+    /// We want to analyze some closures before others, to have a correct analysis:
+    /// * We should analyze nested closures before the parent, since the parent should capture some of
+    ///   the things that its children captures.
+    /// * If a closure calls another closure, we need to analyze the callee, to find out how we should
+    ///   capture it (e.g. by move for FnOnce)
+    ///
+    /// These dependencies are collected in the main inference. We do a topological sort in this function. It
+    /// will consume the `deferred_closures` field and return its content in a sorted vector.
+    fn sort_closures(&mut self) -> Vec<(ClosureId, Vec<(Ty, Ty, Vec<Ty>, ExprId)>)> {
+        let mut deferred_closures = mem::take(&mut self.deferred_closures);
+        let mut dependents_count: FxHashMap<ClosureId, usize> =
+            deferred_closures.keys().map(|x| (*x, 0)).collect();
+        for (_, deps) in &self.closure_dependecies {
+            for dep in deps {
+                *dependents_count.entry(*dep).or_default() += 1;
+            }
+        }
+        let mut queue: Vec<_> =
+            deferred_closures.keys().copied().filter(|x| dependents_count[x] == 0).collect();
+        let mut result = vec![];
+        while let Some(x) = queue.pop() {
+            if let Some(d) = deferred_closures.remove(&x) {
+                result.push((x, d));
+            }
+            for dep in self.closure_dependecies.get(&x).into_iter().flat_map(|x| x.iter()) {
+                let cnt = dependents_count.get_mut(dep).unwrap();
+                *cnt -= 1;
+                if *cnt == 0 {
+                    queue.push(*dep);
+                }
+            }
+        }
+        result
+    }
+}
+
+fn apply_adjusts_to_place(mut r: HirPlace, adjustments: &[Adjustment]) -> Option<HirPlace> {
+    for adj in adjustments {
+        match &adj.kind {
+            Adjust::Deref(None) => {
+                r.projections.push(ProjectionElem::Deref);
+            }
+            _ => return None,
+        }
+    }
+    Some(r)
+}
+
+fn pattern_matching_dereference(
+    cond_ty: &mut Ty,
+    binding_mode: &mut BindingAnnotation,
+    cond_place: &mut HirPlace,
+) {
+    let cnt = pattern_matching_dereference_count(cond_ty, binding_mode);
+    cond_place.projections.extend((0..cnt).map(|_| ProjectionElem::Deref));
+}

crates/hir-ty/src/infer/coerce.rs

@@ -7,9 +7,9 @@
 
 use std::{iter, sync::Arc};
 
-use chalk_ir::{cast::Cast, BoundVar, Goal, Mutability, TyVariableKind};
+use chalk_ir::{cast::Cast, BoundVar, Goal, Mutability, TyKind, TyVariableKind};
 use hir_def::{
-    expr::ExprId,
+    hir::ExprId,
     lang_item::{LangItem, LangItemTarget},
 };
 use stdx::always;
@@ -22,7 +22,7 @@ use crate::{
         TypeError, TypeMismatch,
     },
     static_lifetime, Canonical, DomainGoal, FnPointer, FnSig, Guidance, InEnvironment, Interner,
-    Solution, Substitution, TraitEnvironment, Ty, TyBuilder, TyExt, TyKind,
+    Solution, Substitution, TraitEnvironment, Ty, TyBuilder, TyExt,
 };
 
 use super::unify::InferenceTable;
@@ -111,6 +111,8 @@ impl CoerceMany {
         // pointers to have a chance at getting a match. See
         // https://github.com/rust-lang/rust/blob/7b805396bf46dce972692a6846ce2ad8481c5f85/src/librustc_typeck/check/coercion.rs#L877-L916
         let sig = match (self.merged_ty().kind(Interner), expr_ty.kind(Interner)) {
+            (TyKind::FnDef(x, _), TyKind::FnDef(y, _)) if x == y => None,
+            (TyKind::Closure(x, _), TyKind::Closure(y, _)) if x == y => None,
             (TyKind::FnDef(..) | TyKind::Closure(..), TyKind::FnDef(..) | TyKind::Closure(..)) => {
                 // FIXME: we're ignoring safety here. To be more correct, if we have one FnDef and one Closure,
                 // we should be coercing the closure to a fn pointer of the safety of the FnDef

crates/hir-ty/src/infer/expr.rs

@@ -10,10 +10,10 @@ use chalk_ir::{
     cast::Cast, fold::Shift, DebruijnIndex, GenericArgData, Mutability, TyKind, TyVariableKind,
 };
 use hir_def::{
-    expr::{
+    generics::TypeOrConstParamData,
+    hir::{
         ArithOp, Array, BinaryOp, ClosureKind, Expr, ExprId, LabelId, Literal, Statement, UnaryOp,
     },
-    generics::TypeOrConstParamData,
     lang_item::LangItem,
     path::{GenericArg, GenericArgs},
     BlockId, ConstParamId, FieldId, ItemContainerId, Lookup,
@@ -86,10 +86,10 @@ impl<'a> InferenceContext<'a> {
         }
     }
 
-    pub(super) fn infer_expr_coerce_never(&mut self, expr: ExprId, expected: &Expectation) -> Ty {
+    fn infer_expr_coerce_never(&mut self, expr: ExprId, expected: &Expectation) -> Ty {
         let ty = self.infer_expr_inner(expr, expected);
         // While we don't allow *arbitrary* coercions here, we *do* allow
-        // coercions from ! to `expected`.
+        // coercions from `!` to `expected`.
         if ty.is_never() {
             if let Some(adjustments) = self.result.expr_adjustments.get(&expr) {
                 return if let [Adjustment { kind: Adjust::NeverToAny, target }] = &**adjustments {
@@ -99,13 +99,22 @@ impl<'a> InferenceContext<'a> {
                 };
             }
 
-            let adj_ty = self.table.new_type_var();
-            self.write_expr_adj(
-                expr,
-                vec![Adjustment { kind: Adjust::NeverToAny, target: adj_ty.clone() }],
-            );
-            adj_ty
+            if let Some(target) = expected.only_has_type(&mut self.table) {
+                self.coerce(Some(expr), &ty, &target)
+                    .expect("never-to-any coercion should always succeed")
+            } else {
+                ty
+            }
         } else {
+            if let Some(expected_ty) = expected.only_has_type(&mut self.table) {
+                let could_unify = self.unify(&ty, &expected_ty);
+                if !could_unify {
+                    self.result.type_mismatches.insert(
+                        expr.into(),
+                        TypeMismatch { expected: expected_ty, actual: ty.clone() },
+                    );
+                }
+            }
             ty
         }
     }
@@ -212,7 +221,7 @@ impl<'a> InferenceContext<'a> {
                 self.diverges = Diverges::Maybe;
                 TyBuilder::unit()
             }
-            Expr::Closure { body, args, ret_type, arg_types, closure_kind } => {
+            Expr::Closure { body, args, ret_type, arg_types, closure_kind, capture_by: _ } => {
                 assert_eq!(args.len(), arg_types.len());
 
                 let mut sig_tys = Vec::with_capacity(arg_types.len() + 1);
@@ -247,7 +256,7 @@ impl<'a> InferenceContext<'a> {
                 })
                 .intern(Interner);
 
-                let (ty, resume_yield_tys) = match closure_kind {
+                let (id, ty, resume_yield_tys) = match closure_kind {
                     ClosureKind::Generator(_) => {
                         // FIXME: report error when there are more than 1 parameter.
                         let resume_ty = match sig_tys.first() {
@@ -267,7 +276,7 @@ impl<'a> InferenceContext<'a> {
                         let generator_id = self.db.intern_generator((self.owner, tgt_expr)).into();
                         let generator_ty = TyKind::Generator(generator_id, subst).intern(Interner);
 
-                        (generator_ty, Some((resume_ty, yield_ty)))
+                        (None, generator_ty, Some((resume_ty, yield_ty)))
                     }
                     ClosureKind::Closure | ClosureKind::Async => {
                         let closure_id = self.db.intern_closure((self.owner, tgt_expr)).into();
@@ -276,8 +285,11 @@ impl<'a> InferenceContext<'a> {
                             Substitution::from1(Interner, sig_ty.clone()),
                         )
                         .intern(Interner);
-
-                        (closure_ty, None)
+                        self.deferred_closures.entry(closure_id).or_default();
+                        if let Some(c) = self.current_closure {
+                            self.closure_dependecies.entry(c).or_default().push(closure_id);
+                        }
+                        (Some(closure_id), closure_ty, None)
                     }
                 };
 
@@ -293,6 +305,7 @@ impl<'a> InferenceContext<'a> {
 
                 // FIXME: lift these out into a struct
                 let prev_diverges = mem::replace(&mut self.diverges, Diverges::Maybe);
+                let prev_closure = mem::replace(&mut self.current_closure, id);
                 let prev_ret_ty = mem::replace(&mut self.return_ty, ret_ty.clone());
                 let prev_ret_coercion =
                     mem::replace(&mut self.return_coercion, Some(CoerceMany::new(ret_ty)));
@@ -306,6 +319,7 @@ impl<'a> InferenceContext<'a> {
                 self.diverges = prev_diverges;
                 self.return_ty = prev_ret_ty;
                 self.return_coercion = prev_ret_coercion;
+                self.current_closure = prev_closure;
                 self.resume_yield_tys = prev_resume_yield_tys;
 
                 ty
@@ -331,43 +345,28 @@ impl<'a> InferenceContext<'a> {
                 let (param_tys, ret_ty) = match res {
                     Some((func, params, ret_ty)) => {
                         let mut adjustments = auto_deref_adjust_steps(&derefs);
+                        if let TyKind::Closure(c, _) =
+                            self.table.resolve_completely(callee_ty.clone()).kind(Interner)
+                        {
+                            if let Some(par) = self.current_closure {
+                                self.closure_dependecies.entry(par).or_default().push(*c);
+                            }
+                            self.deferred_closures.entry(*c).or_default().push((
+                                derefed_callee.clone(),
+                                callee_ty.clone(),
+                                params.clone(),
+                                tgt_expr,
+                            ));
+                        }
                         if let Some(fn_x) = func {
-                            match fn_x {
-                                FnTrait::FnOnce => (),
-                                FnTrait::FnMut => {
-                                    if !matches!(
-                                        derefed_callee.kind(Interner),
-                                        TyKind::Ref(Mutability::Mut, _, _)
-                                    ) {
-                                        adjustments.push(Adjustment::borrow(
-                                            Mutability::Mut,
-                                            derefed_callee.clone(),
-                                        ));
-                                    }
-                                }
-                                FnTrait::Fn => {
-                                    if !matches!(
-                                        derefed_callee.kind(Interner),
-                                        TyKind::Ref(Mutability::Not, _, _)
-                                    ) {
-                                        adjustments.push(Adjustment::borrow(
-                                            Mutability::Not,
-                                            derefed_callee.clone(),
-                                        ));
-                                    }
-                                }
-                            }
-                            let trait_ = fn_x
-                                .get_id(self.db, self.table.trait_env.krate)
-                                .expect("We just used it");
-                            let trait_data = self.db.trait_data(trait_);
-                            if let Some(func) = trait_data.method_by_name(&fn_x.method_name()) {
-                                let subst = TyBuilder::subst_for_def(self.db, trait_, None)
-                                    .push(callee_ty.clone())
-                                    .push(TyBuilder::tuple_with(params.iter().cloned()))
-                                    .build();
-                                self.write_method_resolution(tgt_expr, func, subst)
-                            }
+                            self.write_fn_trait_method_resolution(
+                                fn_x,
+                                &derefed_callee,
+                                &mut adjustments,
+                                &callee_ty,
+                                &params,
+                                tgt_expr,
+                            );
                         }
                         self.write_expr_adj(*callee, adjustments);
                         (params, ret_ty)
@@ -459,8 +458,8 @@ impl<'a> InferenceContext<'a> {
                 self.resolver.reset_to_guard(g);
                 ty
             }
-            Expr::Continue { label } => {
-                if let None = find_continuable(&mut self.breakables, label.as_ref()) {
+            &Expr::Continue { label } => {
+                if let None = find_continuable(&mut self.breakables, label) {
                     self.push_diagnostic(InferenceDiagnostic::BreakOutsideOfLoop {
                         expr: tgt_expr,
                         is_break: false,
@@ -469,9 +468,9 @@ impl<'a> InferenceContext<'a> {
                 };
                 self.result.standard_types.never.clone()
             }
-            Expr::Break { expr, label } => {
-                let val_ty = if let Some(expr) = *expr {
-                    let opt_coerce_to = match find_breakable(&mut self.breakables, label.as_ref()) {
+            &Expr::Break { expr, label } => {
+                let val_ty = if let Some(expr) = expr {
+                    let opt_coerce_to = match find_breakable(&mut self.breakables, label) {
                         Some(ctxt) => match &ctxt.coerce {
                             Some(coerce) => coerce.expected_ty(),
                             None => {
@@ -490,13 +489,13 @@ impl<'a> InferenceContext<'a> {
                     TyBuilder::unit()
                 };
 
-                match find_breakable(&mut self.breakables, label.as_ref()) {
+                match find_breakable(&mut self.breakables, label) {
                     Some(ctxt) => match ctxt.coerce.take() {
                         Some(mut coerce) => {
-                            coerce.coerce(self, *expr, &val_ty);
+                            coerce.coerce(self, expr, &val_ty);
 
                             // Avoiding borrowck
-                            let ctxt = find_breakable(&mut self.breakables, label.as_ref())
+                            let ctxt = find_breakable(&mut self.breakables, label)
                                 .expect("breakable stack changed during coercion");
                             ctxt.may_break = true;
                             ctxt.coerce = Some(coerce);
@@ -897,6 +896,41 @@ impl<'a> InferenceContext<'a> {
         TyKind::OpaqueType(opaque_ty_id, Substitution::from1(Interner, inner_ty)).intern(Interner)
     }
 
+    pub(crate) fn write_fn_trait_method_resolution(
+        &mut self,
+        fn_x: FnTrait,
+        derefed_callee: &Ty,
+        adjustments: &mut Vec<Adjustment>,
+        callee_ty: &Ty,
+        params: &Vec<Ty>,
+        tgt_expr: ExprId,
+    ) {
+        match fn_x {
+            FnTrait::FnOnce => (),
+            FnTrait::FnMut => {
+                if !matches!(derefed_callee.kind(Interner), TyKind::Ref(Mutability::Mut, _, _)) {
+                    adjustments.push(Adjustment::borrow(Mutability::Mut, derefed_callee.clone()));
+                }
+            }
+            FnTrait::Fn => {
+                if !matches!(derefed_callee.kind(Interner), TyKind::Ref(Mutability::Not, _, _)) {
+                    adjustments.push(Adjustment::borrow(Mutability::Not, derefed_callee.clone()));
+                }
+            }
+        }
+        let Some(trait_) = fn_x.get_id(self.db, self.table.trait_env.krate) else {
+            return;
+        };
+        let trait_data = self.db.trait_data(trait_);
+        if let Some(func) = trait_data.method_by_name(&fn_x.method_name()) {
+            let subst = TyBuilder::subst_for_def(self.db, trait_, None)
+                .push(callee_ty.clone())
+                .push(TyBuilder::tuple_with(params.iter().cloned()))
+                .build();
+            self.write_method_resolution(tgt_expr, func, subst.clone());
+        }
+    }
+
     fn infer_expr_array(
         &mut self,
         array: &Array,
@@ -1900,7 +1934,6 @@ impl<'a> InferenceContext<'a> {
         cb: impl FnOnce(&mut Self) -> T,
     ) -> (Option<Ty>, T) {
         self.breakables.push({
-            let label = label.map(|label| self.body[label].name.clone());
             BreakableContext { kind, may_break: false, coerce: ty.map(CoerceMany::new), label }
         });
         let res = cb(self);

crates/hir-ty/src/infer/mutability.rs

@@ -3,7 +3,7 @@
 
 use chalk_ir::Mutability;
 use hir_def::{
-    expr::{Array, BindingAnnotation, Expr, ExprId, PatId, Statement, UnaryOp},
+    hir::{Array, BinaryOp, BindingAnnotation, Expr, ExprId, PatId, Statement, UnaryOp},
     lang_item::LangItem,
 };
 use hir_expand::name;
@@ -80,6 +80,9 @@ impl<'a> InferenceContext<'a> {
                 self.infer_mut_expr(*expr, m);
                 for arm in arms.iter() {
                     self.infer_mut_expr(arm.expr, Mutability::Not);
+                    if let Some(g) = arm.guard {
+                        self.infer_mut_expr(g, Mutability::Not);
+                    }
                 }
             }
             Expr::Yield { expr }
@@ -158,14 +161,19 @@ impl<'a> InferenceContext<'a> {
                 let mutability = lower_to_chalk_mutability(*mutability);
                 self.infer_mut_expr(*expr, mutability);
             }
+            Expr::BinaryOp { lhs, rhs, op: Some(BinaryOp::Assignment { .. }) } => {
+                self.infer_mut_expr(*lhs, Mutability::Mut);
+                self.infer_mut_expr(*rhs, Mutability::Not);
+            }
             Expr::Array(Array::Repeat { initializer: lhs, repeat: rhs })
             | Expr::BinaryOp { lhs, rhs, op: _ }
             | Expr::Range { lhs: Some(lhs), rhs: Some(rhs), range_type: _ } => {
                 self.infer_mut_expr(*lhs, Mutability::Not);
                 self.infer_mut_expr(*rhs, Mutability::Not);
             }
-            // not implemented
-            Expr::Closure { .. } => (),
+            Expr::Closure { body, .. } => {
+                self.infer_mut_expr(*body, Mutability::Not);
+            }
             Expr::Tuple { exprs, is_assignee_expr: _ }
             | Expr::Array(Array::ElementList { elements: exprs, is_assignee_expr: _ }) => {
                 self.infer_mut_not_expr_iter(exprs.iter().copied());

crates/hir-ty/src/infer/pat.rs

@@ -5,7 +5,7 @@ use std::iter::repeat_with;
 use chalk_ir::Mutability;
 use hir_def::{
     body::Body,
-    expr::{Binding, BindingAnnotation, BindingId, Expr, ExprId, ExprOrPatId, Literal, Pat, PatId},
+    hir::{Binding, BindingAnnotation, BindingId, Expr, ExprId, ExprOrPatId, Literal, Pat, PatId},
     path::Path,
 };
 use hir_expand::name::Name;

crates/hir-ty/src/inhabitedness.rs

@@ -6,8 +6,8 @@ use chalk_ir::{
     DebruijnIndex,
 };
 use hir_def::{
-    adt::VariantData, attr::Attrs, visibility::Visibility, AdtId, EnumVariantId, HasModule, Lookup,
-    ModuleId, VariantId,
+    attr::Attrs, data::adt::VariantData, visibility::Visibility, AdtId, EnumVariantId, HasModule,
+    Lookup, ModuleId, VariantId,
 };
 use rustc_hash::FxHashSet;
 

crates/hir-ty/src/lang_items.rs

@@ -1,6 +1,6 @@
 //! Functions to detect special lang items
 
-use hir_def::{adt::StructFlags, lang_item::LangItem, AdtId};
+use hir_def::{data::adt::StructFlags, lang_item::LangItem, AdtId};
 use hir_expand::name::Name;
 
 use crate::db::HirDatabase;

crates/hir-ty/src/layout.rs

@@ -229,11 +229,24 @@ pub fn layout_of_ty(db: &dyn HirDatabase, ty: &Ty, krate: CrateId) -> Result<Lay
                 }
             }
         }
-        TyKind::Closure(_, _) | TyKind::Generator(_, _) | TyKind::GeneratorWitness(_, _) => {
+        TyKind::Closure(c, _) => {
+            let (def, _) = db.lookup_intern_closure((*c).into());
+            let infer = db.infer(def);
+            let (captures, _) = infer.closure_info(c);
+            let fields = captures
+                .iter()
+                .map(|x| layout_of_ty(db, &x.ty, krate))
+                .collect::<Result<Vec<_>, _>>()?;
+            let fields = fields.iter().collect::<Vec<_>>();
+            let fields = fields.iter().collect::<Vec<_>>();
+            cx.univariant(dl, &fields, &ReprOptions::default(), StructKind::AlwaysSized)
+                .ok_or(LayoutError::Unknown)?
+        }
+        TyKind::Generator(_, _) | TyKind::GeneratorWitness(_, _) => {
             return Err(LayoutError::NotImplemented)
         }
+        TyKind::Error => return Err(LayoutError::HasErrorType),
         TyKind::AssociatedType(_, _)
-        | TyKind::Error
         | TyKind::Alias(_)
         | TyKind::Placeholder(_)
         | TyKind::BoundVar(_)

crates/hir-ty/src/layout/adt.rs

@@ -3,7 +3,7 @@
 use std::ops::Bound;
 
 use hir_def::{
-    adt::VariantData,
+    data::adt::VariantData,
     layout::{Integer, IntegerExt, Layout, LayoutCalculator, LayoutError, RustcEnumVariantIdx},
     AdtId, EnumVariantId, HasModule, LocalEnumVariantId, VariantId,
 };

crates/hir-ty/src/layout/tests.rs

@@ -11,6 +11,8 @@ use crate::{db::HirDatabase, test_db::TestDB, Interner, Substitution};
 
 use super::layout_of_ty;
 
+mod closure;
+
 fn current_machine_data_layout() -> String {
     project_model::target_data_layout::get(None, None, &HashMap::default()).unwrap()
 }
@@ -81,8 +83,8 @@ fn check_size_and_align(ra_fixture: &str, minicore: &str, size: u64, align: u64)
 #[track_caller]
 fn check_size_and_align_expr(ra_fixture: &str, minicore: &str, size: u64, align: u64) {
     let l = eval_expr(ra_fixture, minicore).unwrap();
-    assert_eq!(l.size.bytes(), size);
-    assert_eq!(l.align.abi.bytes(), align);
+    assert_eq!(l.size.bytes(), size, "size mismatch");
+    assert_eq!(l.align.abi.bytes(), align, "align mismatch");
 }
 
 #[track_caller]
@@ -118,13 +120,31 @@ macro_rules! size_and_align {
     };
 }
 
+#[macro_export]
 macro_rules! size_and_align_expr {
+    (minicore: $($x:tt),*; stmts: [$($s:tt)*] $($t:tt)*) => {
+        {
+            #[allow(dead_code)]
+            #[allow(unused_must_use)]
+            #[allow(path_statements)]
+            {
+                $($s)*
+                let val = { $($t)* };
+                $crate::layout::tests::check_size_and_align_expr(
+                    &format!("{{ {} let val = {{ {} }}; val }}", stringify!($($s)*), stringify!($($t)*)),
+                    &format!("//- minicore: {}\n", stringify!($($x),*)),
+                    ::std::mem::size_of_val(&val) as u64,
+                    ::std::mem::align_of_val(&val) as u64,
+                );
+            }
+        }
+    };
     ($($t:tt)*) => {
         {
             #[allow(dead_code)]
             {
                 let val = { $($t)* };
-                check_size_and_align_expr(
+                $crate::layout::tests::check_size_and_align_expr(
                     stringify!($($t)*),
                     "",
                     ::std::mem::size_of_val(&val) as u64,
@@ -212,6 +232,45 @@ fn return_position_impl_trait() {
         fn foo() -> (impl T, impl T, impl T) { (2i64, 5i32, 7i32) }
         foo()
     }
+    size_and_align_expr! {
+        minicore: iterators;
+        stmts: []
+        trait Tr {}
+        impl Tr for i32 {}
+        fn foo() -> impl Iterator<Item = impl Tr> {
+            [1, 2, 3].into_iter()
+        }
+        let mut iter = foo();
+        let item = iter.next();
+        (iter, item)
+    }
+    size_and_align_expr! {
+        minicore: future;
+        stmts: []
+        use core::{future::Future, task::{Poll, Context}, pin::pin};
+        use std::{task::Wake, sync::Arc};
+        trait Tr {}
+        impl Tr for i32 {}
+        async fn f() -> impl Tr {
+            2
+        }
+        fn unwrap_fut<T>(inp: impl Future<Output = T>) -> Poll<T> {
+            // In a normal test we could use `loop {}` or `panic!()` here,
+            // but rustc actually runs this code.
+            let pinned = pin!(inp);
+            struct EmptyWaker;
+            impl Wake for EmptyWaker {
+                fn wake(self: Arc<Self>) {
+                }
+            }
+            let waker = Arc::new(EmptyWaker).into();
+            let mut context = Context::from_waker(&waker);
+            let x = pinned.poll(&mut context);
+            x
+        }
+        let x = unwrap_fut(f());
+        x
+    }
     size_and_align_expr! {
         struct Foo<T>(T, T, (T, T));
         trait T {}

crates/hir-ty/src/layout/tests/closure.rs

@@ -0,0 +1,175 @@
+use crate::size_and_align_expr;
+
+#[test]
+fn zero_capture_simple() {
+    size_and_align_expr! {
+        |x: i32| x + 2
+    }
+}
+
+#[test]
+fn move_simple() {
+    size_and_align_expr! {
+        minicore: copy;
+        stmts: []
+        let y: i32 = 5;
+        move |x: i32| {
+            x + y
+        }
+    }
+}
+
+#[test]
+fn ref_simple() {
+    size_and_align_expr! {
+        minicore: copy;
+        stmts: [
+            let y: i32 = 5;
+        ]
+        |x: i32| {
+            x + y
+        }
+    }
+    size_and_align_expr! {
+        minicore: copy;
+        stmts: [
+            let mut y: i32 = 5;
+        ]
+        |x: i32| {
+            y = y + x;
+            y
+        }
+    }
+    size_and_align_expr! {
+        minicore: copy;
+        stmts: [
+            struct X(i32, i64);
+            let x: X = X(2, 6);
+        ]
+        || {
+            x
+        }
+    }
+}
+
+#[test]
+fn ref_then_mut_then_move() {
+    size_and_align_expr! {
+        minicore: copy;
+        stmts: [
+            struct X(i32, i64);
+            let mut x: X = X(2, 6);
+        ]
+        || {
+            &x;
+            &mut x;
+            x;
+        }
+    }
+}
+
+#[test]
+fn nested_closures() {
+    size_and_align_expr! {
+        || {
+            || {
+                || {
+                    let x = 2;
+                    move || {
+                        move || {
+                            x
+                        }
+                    }
+                }
+            }
+        }
+    }
+}
+
+#[test]
+fn capture_specific_fields() {
+    size_and_align_expr! {
+        struct X(i64, i32, (u8, i128));
+        let y: X = X(2, 5, (7, 3));
+        move |x: i64| {
+            y.0 + x + (y.2 .0 as i64)
+        }
+    }
+    size_and_align_expr! {
+        struct X(i64, i32, (u8, i128));
+        let y: X = X(2, 5, (7, 3));
+        move |x: i64| {
+            let _ = &y;
+            y.0 + x + (y.2 .0 as i64)
+        }
+    }
+    size_and_align_expr! {
+        minicore: copy;
+        stmts: [
+            struct X(i64, i32, (u8, i128));
+            let y: X = X(2, 5, (7, 3));
+        ]
+        let y = &y;
+        move |x: i64| {
+            y.0 + x + (y.2 .0 as i64)
+        }
+    }
+    size_and_align_expr! {
+        struct X(i64, i32, (u8, i128));
+        let y: X = X(2, 5, (7, 3));
+        move |x: i64| {
+            let X(a, _, (b, _)) = y;
+            a + x + (b as i64)
+        }
+    }
+    size_and_align_expr! {
+        struct X(i64, i32, (u8, i128));
+        let y = &&X(2, 5, (7, 3));
+        move |x: i64| {
+            let X(a, _, (b, _)) = y;
+            *a + x + (*b as i64)
+        }
+    }
+    size_and_align_expr! {
+        struct X(i64, i32, (u8, i128));
+        let y: X = X(2, 5, (7, 3));
+        move |x: i64| {
+            match y {
+                X(a, _, (b, _)) => a + x + (b as i64),
+            }
+        }
+    }
+    size_and_align_expr! {
+        struct X(i64, i32, (u8, i128));
+        let y: X = X(2, 5, (7, 3));
+        move |x: i64| {
+            let X(a @ 2, _, (b, _)) = y else { return 5 };
+            a + x + (b as i64)
+        }
+    }
+}
+
+#[test]
+fn ellipsis_pattern() {
+    size_and_align_expr! {
+        struct X(i8, u16, i32, u64, i128, u8);
+        let y: X = X(1, 2, 3, 4, 5, 6);
+        move |_: i64| {
+            let X(_a, .., _b, _c) = y;
+        }
+    }
+    size_and_align_expr! {
+        struct X { a: i32, b: u8, c: i128}
+        let y: X = X { a: 1, b: 2, c: 3 };
+        move |_: i64| {
+            let X { a, b, .. } = y;
+            _ = (a, b);
+        }
+    }
+    size_and_align_expr! {
+        let y: (&&&(i8, u16, i32, u64, i128, u8), u16, i32, u64, i128, u8) = (&&&(1, 2, 3, 4, 5, 6), 2, 3, 4, 5, 6);
+        move |_: i64| {
+            let ((_a, .., _b, _c), .., _e, _f) = y;
+        }
+    }
+}

crates/hir-ty/src/lib.rs

@@ -44,7 +44,7 @@ use chalk_ir::{
     NoSolution, TyData,
 };
 use either::Either;
-use hir_def::{expr::ExprId, type_ref::Rawness, TypeOrConstParamId};
+use hir_def::{hir::ExprId, type_ref::Rawness, TypeOrConstParamId};
 use hir_expand::name;
 use la_arena::{Arena, Idx};
 use mir::MirEvalError;

crates/hir-ty/src/lower.rs

@@ -18,9 +18,9 @@ use chalk_ir::{
 
 use either::Either;
 use hir_def::{
-    adt::StructKind,
-    body::{Expander, LowerCtx},
+    body::Expander,
     builtin_type::BuiltinType,
+    data::adt::StructKind,
     generics::{
         TypeOrConstParamData, TypeParamProvenance, WherePredicate, WherePredicateTypeTarget,
     },
@@ -380,7 +380,7 @@ impl<'a> TyLoweringContext<'a> {
                     let macro_call = macro_call.to_node(self.db.upcast());
                     match expander.enter_expand::<ast::Type>(self.db.upcast(), macro_call) {
                         Ok(ExpandResult { value: Some((mark, expanded)), .. }) => {
-                            let ctx = LowerCtx::new(self.db.upcast(), expander.current_file_id());
+                            let ctx = expander.ctx(self.db.upcast());
                             let type_ref = TypeRef::from_ast(&ctx, expanded);
 
                             drop(expander);
@@ -988,7 +988,7 @@ impl<'a> TyLoweringContext<'a> {
                         // ignore `T: Drop` or `T: Destruct` bounds.
                         // - `T: ~const Drop` has a special meaning in Rust 1.61 that we don't implement.
                         //   (So ideally, we'd only ignore `~const Drop` here)
-                        // - `Destruct` impls are built-in in 1.62 (current nightlies as of 08-04-2022), so until
+                        // - `Destruct` impls are built-in in 1.62 (current nightly as of 08-04-2022), so until
                         //   the builtin impls are supported by Chalk, we ignore them here.
                         if let Some(lang) = lang_attr(self.db.upcast(), tr.hir_trait_id()) {
                             if matches!(lang, LangItem::Drop | LangItem::Destruct) {
@@ -1082,23 +1082,23 @@ impl<'a> TyLoweringContext<'a> {
                     associated_ty_id: to_assoc_type_id(associated_ty),
                     substitution,
                 };
-                let mut preds: SmallVec<[_; 1]> = SmallVec::with_capacity(
+                let mut predicates: SmallVec<[_; 1]> = SmallVec::with_capacity(
                     binding.type_ref.as_ref().map_or(0, |_| 1) + binding.bounds.len(),
                 );
                 if let Some(type_ref) = &binding.type_ref {
                     let ty = self.lower_ty(type_ref);
                     let alias_eq =
                         AliasEq { alias: AliasTy::Projection(projection_ty.clone()), ty };
-                    preds.push(crate::wrap_empty_binders(WhereClause::AliasEq(alias_eq)));
+                    predicates.push(crate::wrap_empty_binders(WhereClause::AliasEq(alias_eq)));
                 }
                 for bound in binding.bounds.iter() {
-                    preds.extend(self.lower_type_bound(
+                    predicates.extend(self.lower_type_bound(
                         bound,
                         TyKind::Alias(AliasTy::Projection(projection_ty.clone())).intern(Interner),
                         false,
                     ));
                 }
-                preds
+                predicates
             })
     }
 
@@ -1165,7 +1165,7 @@ impl<'a> TyLoweringContext<'a> {
                 return None;
             }
 
-            // As multiple occurrences of the same auto traits *are* permitted, we dedulicate the
+            // As multiple occurrences of the same auto traits *are* permitted, we deduplicate the
             // bounds. We shouldn't have repeated elements besides auto traits at this point.
             bounds.dedup();
 
@@ -1634,7 +1634,7 @@ fn fn_sig_for_fn(db: &dyn HirDatabase, def: FunctionId) -> PolyFnSig {
     let ctx_params = TyLoweringContext::new(db, &resolver)
         .with_impl_trait_mode(ImplTraitLoweringMode::Variable)
         .with_type_param_mode(ParamLoweringMode::Variable);
-    let params = data.params.iter().map(|(_, tr)| ctx_params.lower_ty(tr)).collect::<Vec<_>>();
+    let params = data.params.iter().map(|tr| ctx_params.lower_ty(tr)).collect::<Vec<_>>();
     let ctx_ret = TyLoweringContext::new(db, &resolver)
         .with_impl_trait_mode(ImplTraitLoweringMode::Opaque)
         .with_type_param_mode(ParamLoweringMode::Variable);

crates/hir-ty/src/method_resolution.rs

@@ -7,9 +7,11 @@ use std::{ops::ControlFlow, sync::Arc};
 use base_db::{CrateId, Edition};
 use chalk_ir::{cast::Cast, Mutability, TyKind, UniverseIndex, WhereClause};
 use hir_def::{
-    adt::StructFlags, data::ImplData, item_scope::ItemScope, nameres::DefMap, AssocItemId, BlockId,
-    ConstId, FunctionId, HasModule, ImplId, ItemContainerId, Lookup, ModuleDefId, ModuleId,
-    TraitId,
+    data::{adt::StructFlags, ImplData},
+    item_scope::ItemScope,
+    nameres::DefMap,
+    AssocItemId, BlockId, ConstId, FunctionId, HasModule, ImplId, ItemContainerId, Lookup,
+    ModuleDefId, ModuleId, TraitId,
 };
 use hir_expand::name::Name;
 use rustc_hash::{FxHashMap, FxHashSet};
@@ -952,7 +954,14 @@ fn iterate_method_candidates_with_autoref(
         )
     };
 
-    iterate_method_candidates_by_receiver(receiver_ty, first_adjustment.clone())?;
+    let mut maybe_reborrowed = first_adjustment.clone();
+    if let Some((_, _, m)) = receiver_ty.value.as_reference() {
+        // Prefer reborrow of references to move
+        maybe_reborrowed.autoref = Some(m);
+        maybe_reborrowed.autoderefs += 1;
+    }
+
+    iterate_method_candidates_by_receiver(receiver_ty, maybe_reborrowed)?;
 
     let refed = Canonical {
         value: TyKind::Ref(Mutability::Not, static_lifetime(), receiver_ty.value.clone())

crates/hir-ty/src/mir.rs

@@ -3,11 +3,12 @@
 use std::{fmt::Display, iter};
 
 use crate::{
-    infer::PointerCast, Const, ConstScalar, InferenceResult, Interner, MemoryMap, Substitution, Ty,
+    db::HirDatabase, infer::PointerCast, ClosureId, Const, ConstScalar, InferenceResult, Interner,
+    MemoryMap, Substitution, Ty, TyKind,
 };
 use chalk_ir::Mutability;
 use hir_def::{
-    expr::{BindingId, Expr, ExprId, Ordering, PatId},
+    hir::{BindingId, Expr, ExprId, Ordering, PatId},
     DefWithBodyId, FieldId, UnionId, VariantId,
 };
 use la_arena::{Arena, ArenaMap, Idx, RawIdx};
@@ -19,9 +20,11 @@ mod pretty;
 
 pub use borrowck::{borrowck_query, BorrowckResult, MutabilityReason};
 pub use eval::{interpret_mir, pad16, Evaluator, MirEvalError};
-pub use lower::{lower_to_mir, mir_body_query, mir_body_recover, MirLowerError};
+pub use lower::{
+    lower_to_mir, mir_body_for_closure_query, mir_body_query, mir_body_recover, MirLowerError,
+};
 use smallvec::{smallvec, SmallVec};
-use stdx::impl_from;
+use stdx::{impl_from, never};
 
 use super::consteval::{intern_const_scalar, try_const_usize};
 
@@ -89,11 +92,12 @@ impl Operand {
     }
 }
 
-#[derive(Debug, PartialEq, Eq, Clone)]
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
 pub enum ProjectionElem<V, T> {
     Deref,
     Field(FieldId),
-    TupleField(usize),
+    // FIXME: get rid of this, and use FieldId for tuples and closures
+    TupleOrClosureField(usize),
     Index(V),
     ConstantIndex { offset: u64, min_length: u64, from_end: bool },
     Subslice { from: u64, to: u64, from_end: bool },
@@ -101,6 +105,63 @@ pub enum ProjectionElem<V, T> {
     OpaqueCast(T),
 }
 
+impl<V, T> ProjectionElem<V, T> {
+    pub fn projected_ty(
+        &self,
+        base: Ty,
+        db: &dyn HirDatabase,
+        closure_field: impl FnOnce(ClosureId, usize) -> Ty,
+    ) -> Ty {
+        match self {
+            ProjectionElem::Deref => match &base.data(Interner).kind {
+                TyKind::Raw(_, inner) | TyKind::Ref(_, _, inner) => inner.clone(),
+                _ => {
+                    never!("Overloaded deref is not a projection");
+                    return TyKind::Error.intern(Interner);
+                }
+            },
+            ProjectionElem::Field(f) => match &base.data(Interner).kind {
+                TyKind::Adt(_, subst) => {
+                    db.field_types(f.parent)[f.local_id].clone().substitute(Interner, subst)
+                }
+                _ => {
+                    never!("Only adt has field");
+                    return TyKind::Error.intern(Interner);
+                }
+            },
+            ProjectionElem::TupleOrClosureField(f) => match &base.data(Interner).kind {
+                TyKind::Tuple(_, subst) => subst
+                    .as_slice(Interner)
+                    .get(*f)
+                    .map(|x| x.assert_ty_ref(Interner))
+                    .cloned()
+                    .unwrap_or_else(|| {
+                        never!("Out of bound tuple field");
+                        TyKind::Error.intern(Interner)
+                    }),
+                TyKind::Closure(id, _) => closure_field(*id, *f),
+                _ => {
+                    never!("Only tuple or closure has tuple or closure field");
+                    return TyKind::Error.intern(Interner);
+                }
+            },
+            ProjectionElem::Index(_) => match &base.data(Interner).kind {
+                TyKind::Array(inner, _) | TyKind::Slice(inner) => inner.clone(),
+                _ => {
+                    never!("Overloaded index is not a projection");
+                    return TyKind::Error.intern(Interner);
+                }
+            },
+            ProjectionElem::ConstantIndex { .. }
+            | ProjectionElem::Subslice { .. }
+            | ProjectionElem::OpaqueCast(_) => {
+                never!("We don't emit these yet");
+                return TyKind::Error.intern(Interner);
+            }
+        }
+    }
+}
+
 type PlaceElem = ProjectionElem<LocalId, Ty>;
 
 #[derive(Debug, Clone, PartialEq, Eq)]
@@ -123,7 +184,7 @@ pub enum AggregateKind {
     Tuple(Ty),
     Adt(VariantId, Substitution),
     Union(UnionId, FieldId),
-    //Closure(LocalDefId, SubstsRef),
+    Closure(Ty),
     //Generator(LocalDefId, SubstsRef, Movability),
 }
 
@@ -418,7 +479,7 @@ pub enum Terminator {
     },
 }
 
-#[derive(Debug, PartialEq, Eq, Clone)]
+#[derive(Debug, PartialEq, Eq, Clone, Copy, PartialOrd, Ord)]
 pub enum BorrowKind {
     /// Data must be immutable and is aliasable.
     Shared,
@@ -588,32 +649,32 @@ impl Display for BinOp {
     }
 }
 
-impl From<hir_def::expr::ArithOp> for BinOp {
-    fn from(value: hir_def::expr::ArithOp) -> Self {
+impl From<hir_def::hir::ArithOp> for BinOp {
+    fn from(value: hir_def::hir::ArithOp) -> Self {
         match value {
-            hir_def::expr::ArithOp::Add => BinOp::Add,
-            hir_def::expr::ArithOp::Mul => BinOp::Mul,
-            hir_def::expr::ArithOp::Sub => BinOp::Sub,
-            hir_def::expr::ArithOp::Div => BinOp::Div,
-            hir_def::expr::ArithOp::Rem => BinOp::Rem,
-            hir_def::expr::ArithOp::Shl => BinOp::Shl,
-            hir_def::expr::ArithOp::Shr => BinOp::Shr,
-            hir_def::expr::ArithOp::BitXor => BinOp::BitXor,
-            hir_def::expr::ArithOp::BitOr => BinOp::BitOr,
-            hir_def::expr::ArithOp::BitAnd => BinOp::BitAnd,
+            hir_def::hir::ArithOp::Add => BinOp::Add,
+            hir_def::hir::ArithOp::Mul => BinOp::Mul,
+            hir_def::hir::ArithOp::Sub => BinOp::Sub,
+            hir_def::hir::ArithOp::Div => BinOp::Div,
+            hir_def::hir::ArithOp::Rem => BinOp::Rem,
+            hir_def::hir::ArithOp::Shl => BinOp::Shl,
+            hir_def::hir::ArithOp::Shr => BinOp::Shr,
+            hir_def::hir::ArithOp::BitXor => BinOp::BitXor,
+            hir_def::hir::ArithOp::BitOr => BinOp::BitOr,
+            hir_def::hir::ArithOp::BitAnd => BinOp::BitAnd,
         }
     }
 }
 
-impl From<hir_def::expr::CmpOp> for BinOp {
-    fn from(value: hir_def::expr::CmpOp) -> Self {
+impl From<hir_def::hir::CmpOp> for BinOp {
+    fn from(value: hir_def::hir::CmpOp) -> Self {
         match value {
-            hir_def::expr::CmpOp::Eq { negated: false } => BinOp::Eq,
-            hir_def::expr::CmpOp::Eq { negated: true } => BinOp::Ne,
-            hir_def::expr::CmpOp::Ord { ordering: Ordering::Greater, strict: false } => BinOp::Ge,
-            hir_def::expr::CmpOp::Ord { ordering: Ordering::Greater, strict: true } => BinOp::Gt,
-            hir_def::expr::CmpOp::Ord { ordering: Ordering::Less, strict: false } => BinOp::Le,
-            hir_def::expr::CmpOp::Ord { ordering: Ordering::Less, strict: true } => BinOp::Lt,
+            hir_def::hir::CmpOp::Eq { negated: false } => BinOp::Eq,
+            hir_def::hir::CmpOp::Eq { negated: true } => BinOp::Ne,
+            hir_def::hir::CmpOp::Ord { ordering: Ordering::Greater, strict: false } => BinOp::Ge,
+            hir_def::hir::CmpOp::Ord { ordering: Ordering::Greater, strict: true } => BinOp::Gt,
+            hir_def::hir::CmpOp::Ord { ordering: Ordering::Less, strict: false } => BinOp::Le,
+            hir_def::hir::CmpOp::Ord { ordering: Ordering::Less, strict: true } => BinOp::Lt,
         }
     }
 }
@@ -847,6 +908,87 @@ pub struct MirBody {
     pub arg_count: usize,
     pub binding_locals: ArenaMap<BindingId, LocalId>,
     pub param_locals: Vec<LocalId>,
+    /// This field stores the closures directly owned by this body. It is used
+    /// in traversing every mir body.
+    pub closures: Vec<ClosureId>,
+}
+
+impl MirBody {
+    fn walk_places(&mut self, mut f: impl FnMut(&mut Place)) {
+        fn for_operand(op: &mut Operand, f: &mut impl FnMut(&mut Place)) {
+            match op {
+                Operand::Copy(p) | Operand::Move(p) => {
+                    f(p);
+                }
+                Operand::Constant(_) => (),
+            }
+        }
+        for (_, block) in self.basic_blocks.iter_mut() {
+            for statement in &mut block.statements {
+                match &mut statement.kind {
+                    StatementKind::Assign(p, r) => {
+                        f(p);
+                        match r {
+                            Rvalue::ShallowInitBox(o, _)
+                            | Rvalue::UnaryOp(_, o)
+                            | Rvalue::Cast(_, o, _)
+                            | Rvalue::Use(o) => for_operand(o, &mut f),
+                            Rvalue::CopyForDeref(p)
+                            | Rvalue::Discriminant(p)
+                            | Rvalue::Len(p)
+                            | Rvalue::Ref(_, p) => f(p),
+                            Rvalue::CheckedBinaryOp(_, o1, o2) => {
+                                for_operand(o1, &mut f);
+                                for_operand(o2, &mut f);
+                            }
+                            Rvalue::Aggregate(_, ops) => {
+                                for op in ops {
+                                    for_operand(op, &mut f);
+                                }
+                            }
+                        }
+                    }
+                    StatementKind::Deinit(p) => f(p),
+                    StatementKind::StorageLive(_)
+                    | StatementKind::StorageDead(_)
+                    | StatementKind::Nop => (),
+                }
+            }
+            match &mut block.terminator {
+                Some(x) => match x {
+                    Terminator::SwitchInt { discr, .. } => for_operand(discr, &mut f),
+                    Terminator::FalseEdge { .. }
+                    | Terminator::FalseUnwind { .. }
+                    | Terminator::Goto { .. }
+                    | Terminator::Resume
+                    | Terminator::GeneratorDrop
+                    | Terminator::Abort
+                    | Terminator::Return
+                    | Terminator::Unreachable => (),
+                    Terminator::Drop { place, .. } => {
+                        f(place);
+                    }
+                    Terminator::DropAndReplace { place, value, .. } => {
+                        f(place);
+                        for_operand(value, &mut f);
+                    }
+                    Terminator::Call { func, args, destination, .. } => {
+                        for_operand(func, &mut f);
+                        args.iter_mut().for_each(|x| for_operand(x, &mut f));
+                        f(destination);
+                    }
+                    Terminator::Assert { cond, .. } => {
+                        for_operand(cond, &mut f);
+                    }
+                    Terminator::Yield { value, resume_arg, .. } => {
+                        for_operand(value, &mut f);
+                        f(resume_arg);
+                    }
+                },
+                None => (),
+            }
+        }
+    }
 }
 
 fn const_as_usize(c: &Const) -> usize {

crates/hir-ty/src/mir/borrowck.rs

@@ -3,13 +3,13 @@
 // Currently it is an ad-hoc implementation, only useful for mutability analysis. Feel free to remove all of these
 // if needed for implementing a proper borrow checker.
 
-use std::sync::Arc;
+use std::{iter, sync::Arc};
 
 use hir_def::DefWithBodyId;
 use la_arena::ArenaMap;
 use stdx::never;
 
-use crate::db::HirDatabase;
+use crate::{db::HirDatabase, ClosureId};
 
 use super::{
     BasicBlockId, BorrowKind, LocalId, MirBody, MirLowerError, MirSpan, Place, ProjectionElem,
@@ -29,14 +29,48 @@ pub struct BorrowckResult {
     pub mutability_of_locals: ArenaMap<LocalId, MutabilityReason>,
 }
 
+fn all_mir_bodies(
+    db: &dyn HirDatabase,
+    def: DefWithBodyId,
+) -> Box<dyn Iterator<Item = Result<Arc<MirBody>, MirLowerError>> + '_> {
+    fn for_closure(
+        db: &dyn HirDatabase,
+        c: ClosureId,
+    ) -> Box<dyn Iterator<Item = Result<Arc<MirBody>, MirLowerError>> + '_> {
+        match db.mir_body_for_closure(c) {
+            Ok(body) => {
+                let closures = body.closures.clone();
+                Box::new(
+                    iter::once(Ok(body))
+                        .chain(closures.into_iter().flat_map(|x| for_closure(db, x))),
+                )
+            }
+            Err(e) => Box::new(iter::once(Err(e))),
+        }
+    }
+    match db.mir_body(def) {
+        Ok(body) => {
+            let closures = body.closures.clone();
+            Box::new(
+                iter::once(Ok(body)).chain(closures.into_iter().flat_map(|x| for_closure(db, x))),
+            )
+        }
+        Err(e) => Box::new(iter::once(Err(e))),
+    }
+}
+
 pub fn borrowck_query(
     db: &dyn HirDatabase,
     def: DefWithBodyId,
-) -> Result<Arc<BorrowckResult>, MirLowerError> {
+) -> Result<Arc<[BorrowckResult]>, MirLowerError> {
     let _p = profile::span("borrowck_query");
-    let body = db.mir_body(def)?;
-    let r = BorrowckResult { mutability_of_locals: mutability_of_locals(&body), mir_body: body };
-    Ok(Arc::new(r))
+    let r = all_mir_bodies(db, def)
+        .map(|body| {
+            let body = body?;
+            Ok(BorrowckResult { mutability_of_locals: mutability_of_locals(&body), mir_body: body })
+        })
+        .collect::<Result<Vec<_>, MirLowerError>>()?;
+    Ok(r.into())
 }
 
 fn is_place_direct(lvalue: &Place) -> bool {
@@ -60,7 +94,7 @@ fn place_case(lvalue: &Place) -> ProjectionCase {
             ProjectionElem::ConstantIndex { .. }
             | ProjectionElem::Subslice { .. }
             | ProjectionElem::Field(_)
-            | ProjectionElem::TupleField(_)
+            | ProjectionElem::TupleOrClosureField(_)
             | ProjectionElem::Index(_) => {
                 is_part_of = true;
             }

crates/hir-ty/src/mir/eval.rs

@@ -25,8 +25,8 @@ use crate::{
     mapping::from_chalk,
     method_resolution::{is_dyn_method, lookup_impl_method},
     traits::FnTrait,
-    CallableDefId, Const, ConstScalar, FnDefId, GenericArgData, Interner, MemoryMap, Substitution,
-    TraitEnvironment, Ty, TyBuilder, TyExt,
+    CallableDefId, ClosureId, Const, ConstScalar, FnDefId, GenericArgData, Interner, MemoryMap,
+    Substitution, TraitEnvironment, Ty, TyBuilder, TyExt,
 };
 
 use super::{
@@ -92,6 +92,7 @@ pub struct Evaluator<'a> {
 enum Address {
     Stack(usize),
     Heap(usize),
+    Invalid(usize),
 }
 
 use Address::*;
@@ -169,8 +170,10 @@ impl Address {
     fn from_usize(x: usize) -> Self {
         if x > usize::MAX / 2 {
             Stack(x - usize::MAX / 2)
+        } else if x > usize::MAX / 4 {
+            Heap(x - usize::MAX / 4)
         } else {
-            Heap(x)
+            Invalid(x)
         }
     }
 
@@ -181,7 +184,8 @@ impl Address {
     fn to_usize(&self) -> usize {
         let as_num = match self {
             Stack(x) => *x + usize::MAX / 2,
-            Heap(x) => *x,
+            Heap(x) => *x + usize::MAX / 4,
+            Invalid(x) => *x,
         };
         as_num
     }
@@ -190,6 +194,7 @@ impl Address {
         match self {
             Stack(x) => Stack(f(*x)),
             Heap(x) => Heap(f(*x)),
+            Invalid(x) => Invalid(f(*x)),
         }
     }
 
@@ -209,6 +214,7 @@ pub enum MirEvalError {
     UndefinedBehavior(&'static str),
     Panic(String),
     MirLowerError(FunctionId, MirLowerError),
+    MirLowerErrorForClosure(ClosureId, MirLowerError),
     TypeIsUnsized(Ty, &'static str),
     NotSupported(String),
     InvalidConst(Const),
@@ -238,6 +244,9 @@ impl std::fmt::Debug for MirEvalError {
             Self::MirLowerError(arg0, arg1) => {
                 f.debug_tuple("MirLowerError").field(arg0).field(arg1).finish()
             }
+            Self::MirLowerErrorForClosure(arg0, arg1) => {
+                f.debug_tuple("MirLowerError").field(arg0).field(arg1).finish()
+            }
             Self::InvalidVTableId(arg0) => f.debug_tuple("InvalidVTableId").field(arg0).finish(),
             Self::NotSupported(arg0) => f.debug_tuple("NotSupported").field(arg0).finish(),
             Self::InvalidConst(arg0) => {
@@ -355,16 +364,15 @@ impl Evaluator<'_> {
             self.ty_filler(&locals.body.locals[p.local].ty, locals.subst, locals.body.owner)?;
         let mut metadata = None; // locals are always sized
         for proj in &p.projection {
+            let prev_ty = ty.clone();
+            ty = proj.projected_ty(ty, self.db, |c, f| {
+                let (def, _) = self.db.lookup_intern_closure(c.into());
+                let infer = self.db.infer(def);
+                let (captures, _) = infer.closure_info(&c);
+                captures.get(f).expect("broken closure field").ty.clone()
+            });
             match proj {
                 ProjectionElem::Deref => {
-                    ty = match &ty.data(Interner).kind {
-                        TyKind::Raw(_, inner) | TyKind::Ref(_, _, inner) => inner.clone(),
-                        _ => {
-                            return Err(MirEvalError::TypeError(
-                                "Overloaded deref in MIR is disallowed",
-                            ))
-                        }
-                    };
                     metadata = if self.size_of(&ty, locals)?.is_none() {
                         Some(Interval { addr: addr.offset(self.ptr_size()), size: self.ptr_size() })
                     } else {
@@ -377,78 +385,41 @@ impl Evaluator<'_> {
                     let offset =
                         from_bytes!(usize, self.read_memory(locals.ptr[*op], self.ptr_size())?);
                     metadata = None; // Result of index is always sized
-                    match &ty.data(Interner).kind {
-                        TyKind::Ref(_, _, inner) => match &inner.data(Interner).kind {
-                            TyKind::Slice(inner) => {
-                                ty = inner.clone();
-                                let ty_size = self.size_of_sized(
-                                    &ty,
-                                    locals,
-                                    "slice inner type should be sized",
-                                )?;
-                                let value = self.read_memory(addr, self.ptr_size() * 2)?;
-                                addr = Address::from_bytes(&value[0..8])?.offset(ty_size * offset);
-                            }
-                            x => not_supported!("MIR index for ref type {x:?}"),
-                        },
-                        TyKind::Array(inner, _) | TyKind::Slice(inner) => {
-                            ty = inner.clone();
-                            let ty_size = self.size_of_sized(
-                                &ty,
-                                locals,
-                                "array inner type should be sized",
-                            )?;
-                            addr = addr.offset(ty_size * offset);
-                        }
-                        x => not_supported!("MIR index for type {x:?}"),
-                    }
+                    let ty_size =
+                        self.size_of_sized(&ty, locals, "array inner type should be sized")?;
+                    addr = addr.offset(ty_size * offset);
+                }
+                &ProjectionElem::TupleOrClosureField(f) => {
+                    let layout = self.layout(&prev_ty)?;
+                    let offset = layout.fields.offset(f).bytes_usize();
+                    addr = addr.offset(offset);
+                    metadata = None; // tuple field is always sized
+                }
+                ProjectionElem::Field(f) => {
+                    let layout = self.layout(&prev_ty)?;
+                    let variant_layout = match &layout.variants {
+                        Variants::Single { .. } => &layout,
+                        Variants::Multiple { variants, .. } => {
+                            &variants[match f.parent {
+                                hir_def::VariantId::EnumVariantId(x) => {
+                                    RustcEnumVariantIdx(x.local_id)
+                                }
+                                _ => {
+                                    return Err(MirEvalError::TypeError(
+                                        "Multivariant layout only happens for enums",
+                                    ))
+                                }
+                            }]
+                        }
+                    };
+                    let offset = variant_layout
+                        .fields
+                        .offset(u32::from(f.local_id.into_raw()) as usize)
+                        .bytes_usize();
+                    addr = addr.offset(offset);
+                    // FIXME: support structs with unsized fields
+                    metadata = None;
                 }
-                &ProjectionElem::TupleField(f) => match &ty.data(Interner).kind {
-                    TyKind::Tuple(_, subst) => {
-                        let layout = self.layout(&ty)?;
-                        ty = subst
-                            .as_slice(Interner)
-                            .get(f)
-                            .ok_or(MirEvalError::TypeError("not enough tuple fields"))?
-                            .assert_ty_ref(Interner)
-                            .clone();
-                        let offset = layout.fields.offset(f).bytes_usize();
-                        addr = addr.offset(offset);
-                        metadata = None; // tuple field is always sized
-                    }
-                    _ => return Err(MirEvalError::TypeError("Only tuple has tuple fields")),
-                },
-                ProjectionElem::Field(f) => match &ty.data(Interner).kind {
-                    TyKind::Adt(adt, subst) => {
-                        let layout = self.layout_adt(adt.0, subst.clone())?;
-                        let variant_layout = match &layout.variants {
-                            Variants::Single { .. } => &layout,
-                            Variants::Multiple { variants, .. } => {
-                                &variants[match f.parent {
-                                    hir_def::VariantId::EnumVariantId(x) => {
-                                        RustcEnumVariantIdx(x.local_id)
-                                    }
-                                    _ => {
-                                        return Err(MirEvalError::TypeError(
-                                            "Multivariant layout only happens for enums",
-                                        ))
-                                    }
-                                }]
-                            }
-                        };
-                        ty = self.db.field_types(f.parent)[f.local_id]
-                            .clone()
-                            .substitute(Interner, subst);
-                        let offset = variant_layout
-                            .fields
-                            .offset(u32::from(f.local_id.into_raw()) as usize)
-                            .bytes_usize();
-                        addr = addr.offset(offset);
-                        // FIXME: support structs with unsized fields
-                        metadata = None;
-                    }
-                    _ => return Err(MirEvalError::TypeError("Only adt has fields")),
-                },
                 ProjectionElem::ConstantIndex { .. } => {
                     not_supported!("constant index")
                 }
@@ -845,6 +816,15 @@ impl Evaluator<'_> {
                             values.iter().copied(),
                         )?)
                     }
+                    AggregateKind::Closure(ty) => {
+                        let layout = self.layout(&ty)?;
+                        Owned(self.make_by_layout(
+                            layout.size.bytes_usize(),
+                            &layout,
+                            None,
+                            values.iter().copied(),
+                        )?)
+                    }
                 }
             }
             Rvalue::Cast(kind, operand, target_ty) => match kind {
@@ -1065,6 +1045,9 @@ impl Evaluator<'_> {
         let (mem, pos) = match addr {
             Stack(x) => (&self.stack, x),
             Heap(x) => (&self.heap, x),
+            Invalid(_) => {
+                return Err(MirEvalError::UndefinedBehavior("read invalid memory address"))
+            }
         };
         mem.get(pos..pos + size).ok_or(MirEvalError::UndefinedBehavior("out of bound memory read"))
     }
@@ -1073,6 +1056,9 @@ impl Evaluator<'_> {
         let (mem, pos) = match addr {
             Stack(x) => (&mut self.stack, x),
             Heap(x) => (&mut self.heap, x),
+            Invalid(_) => {
+                return Err(MirEvalError::UndefinedBehavior("write invalid memory address"))
+            }
         };
         mem.get_mut(pos..pos + r.len())
             .ok_or(MirEvalError::UndefinedBehavior("out of bound memory write"))?
@@ -1394,6 +1380,25 @@ impl Evaluator<'_> {
         Ok(())
     }
 
+    fn exec_closure(
+        &mut self,
+        closure: ClosureId,
+        closure_data: Interval,
+        generic_args: &Substitution,
+        destination: Interval,
+        args: &[IntervalAndTy],
+    ) -> Result<()> {
+        let mir_body = self
+            .db
+            .mir_body_for_closure(closure)
+            .map_err(|x| MirEvalError::MirLowerErrorForClosure(closure, x))?;
+        let arg_bytes = iter::once(Ok(closure_data.get(self)?.to_owned()))
+            .chain(args.iter().map(|x| Ok(x.get(&self)?.to_owned())))
+            .collect::<Result<Vec<_>>>()?;
+        let bytes = self.interpret_mir(&mir_body, arg_bytes.into_iter(), generic_args.clone())?;
+        destination.write_from_bytes(self, &bytes)
+    }
+
     fn exec_fn_def(
         &mut self,
         def: FnDefId,
@@ -1546,6 +1551,9 @@ impl Evaluator<'_> {
             TyKind::Function(_) => {
                 self.exec_fn_pointer(func_data, destination, &args[1..], locals)?;
             }
+            TyKind::Closure(closure, subst) => {
+                self.exec_closure(*closure, func_data, subst, destination, &args[1..])?;
+            }
             x => not_supported!("Call FnTrait methods with type {x:?}"),
         }
         Ok(())

crates/hir-ty/src/mir/lower.rs

@@ -4,9 +4,9 @@ use std::{iter, mem, sync::Arc};
 
 use chalk_ir::{BoundVar, ConstData, DebruijnIndex, TyKind};
 use hir_def::{
-    adt::{StructKind, VariantData},
     body::Body,
-    expr::{
+    data::adt::{StructKind, VariantData},
+    hir::{
         Array, BindingAnnotation, BindingId, ExprId, LabelId, Literal, MatchArm, Pat, PatId,
         RecordFieldPat, RecordLitField,
     },
@@ -21,9 +21,16 @@ use la_arena::ArenaMap;
 use rustc_hash::FxHashMap;
 
 use crate::{
-    consteval::ConstEvalError, db::HirDatabase, display::HirDisplay, infer::TypeMismatch,
-    inhabitedness::is_ty_uninhabited_from, layout::layout_of_ty, mapping::ToChalk, static_lifetime,
-    utils::generics, Adjust, Adjustment, AutoBorrow, CallableDefId, TyBuilder, TyExt,
+    consteval::ConstEvalError,
+    db::HirDatabase,
+    display::HirDisplay,
+    infer::{CaptureKind, CapturedItem, TypeMismatch},
+    inhabitedness::is_ty_uninhabited_from,
+    layout::layout_of_ty,
+    mapping::ToChalk,
+    static_lifetime,
+    utils::generics,
+    Adjust, Adjustment, AutoBorrow, CallableDefId, TyBuilder, TyExt,
 };
 
 use super::*;
@@ -47,7 +54,7 @@ struct MirLowerCtx<'a> {
     current_loop_blocks: Option<LoopBlocks>,
     // FIXME: we should resolve labels in HIR lowering and always work with label id here, not
     // with raw names.
-    labeled_loop_blocks: FxHashMap<Name, LoopBlocks>,
+    labeled_loop_blocks: FxHashMap<LabelId, LoopBlocks>,
     discr_temp: Option<Place>,
     db: &'a dyn HirDatabase,
     body: &'a Body,
@@ -74,10 +81,12 @@ pub enum MirLowerError {
     BreakWithoutLoop,
     Loop,
     /// Something that should never happen and is definitely a bug, but we don't want to panic if it happened
-    ImplementationError(&'static str),
+    ImplementationError(String),
     LangItemNotFound(LangItem),
     MutatingRvalue,
     UnresolvedLabel,
+    UnresolvedUpvar(Place),
+    UnaccessableLocal,
 }
 
 macro_rules! not_supported {
@@ -88,8 +97,8 @@ macro_rules! not_supported {
 
 macro_rules! implementation_error {
     ($x: expr) => {{
-        ::stdx::never!("MIR lower implementation bug: {}", $x);
-        return Err(MirLowerError::ImplementationError($x));
+        ::stdx::never!("MIR lower implementation bug: {}", format!($x));
+        return Err(MirLowerError::ImplementationError(format!($x)));
     }};
 }
 
@@ -116,7 +125,44 @@ impl MirLowerError {
 
 type Result<T> = std::result::Result<T, MirLowerError>;
 
-impl MirLowerCtx<'_> {
+impl<'ctx> MirLowerCtx<'ctx> {
+    fn new(
+        db: &'ctx dyn HirDatabase,
+        owner: DefWithBodyId,
+        body: &'ctx Body,
+        infer: &'ctx InferenceResult,
+    ) -> Self {
+        let mut basic_blocks = Arena::new();
+        let start_block = basic_blocks.alloc(BasicBlock {
+            statements: vec![],
+            terminator: None,
+            is_cleanup: false,
+        });
+        let locals = Arena::new();
+        let binding_locals: ArenaMap<BindingId, LocalId> = ArenaMap::new();
+        let mir = MirBody {
+            basic_blocks,
+            locals,
+            start_block,
+            binding_locals,
+            param_locals: vec![],
+            owner,
+            arg_count: body.params.len(),
+            closures: vec![],
+        };
+        let ctx = MirLowerCtx {
+            result: mir,
+            db,
+            infer,
+            body,
+            owner,
+            current_loop_blocks: None,
+            labeled_loop_blocks: Default::default(),
+            discr_temp: None,
+        };
+        ctx
+    }
+
     fn temp(&mut self, ty: Ty) -> Result<LocalId> {
         if matches!(ty.kind(Interner), TyKind::Slice(_) | TyKind::Dyn(_)) {
             implementation_error!("unsized temporaries");
@@ -268,7 +314,7 @@ impl MirLowerCtx<'_> {
                         self.push_assignment(
                             current,
                             place,
-                            Operand::Copy(self.result.binding_locals[pat_id].into()).into(),
+                            Operand::Copy(self.binding_local(pat_id)?.into()).into(),
                             expr_id.into(),
                         );
                         Ok(Some(current))
@@ -579,19 +625,19 @@ impl MirLowerCtx<'_> {
                     Ok(None)
                 }
             },
-            Expr::Break { expr, label } => {
+            &Expr::Break { expr, label } => {
                 if let Some(expr) = expr {
                     let loop_data = match label {
-                        Some(l) => self.labeled_loop_blocks.get(l).ok_or(MirLowerError::UnresolvedLabel)?,
+                        Some(l) => self.labeled_loop_blocks.get(&l).ok_or(MirLowerError::UnresolvedLabel)?,
                         None => self.current_loop_blocks.as_ref().ok_or(MirLowerError::BreakWithoutLoop)?,
                     };
-                    let Some(c) = self.lower_expr_to_place(*expr, loop_data.place.clone(), current)? else {
+                    let Some(c) = self.lower_expr_to_place(expr, loop_data.place.clone(), current)? else {
                         return Ok(None);
                     };
                     current = c;
                 }
                 let end = match label {
-                    Some(l) => self.labeled_loop_blocks.get(l).ok_or(MirLowerError::UnresolvedLabel)?.end.expect("We always generate end for labeled loops"),
+                    Some(l) => self.labeled_loop_blocks.get(&l).ok_or(MirLowerError::UnresolvedLabel)?.end.expect("We always generate end for labeled loops"),
                     None => self.current_loop_end()?,
                 };
                 self.set_goto(current, end);
@@ -713,20 +759,20 @@ impl MirLowerCtx<'_> {
                 Ok(Some(current))
             }
             Expr::Box { .. } => not_supported!("box expression"),
-            Expr::Field { .. } | Expr::Index { .. } | Expr::UnaryOp { op: hir_def::expr::UnaryOp::Deref, .. } => {
+            Expr::Field { .. } | Expr::Index { .. } | Expr::UnaryOp { op: hir_def::hir::UnaryOp::Deref, .. } => {
                 let Some((p, current)) = self.lower_expr_as_place_without_adjust(current, expr_id, true)? else {
                     return Ok(None);
                 };
                 self.push_assignment(current, place, Operand::Copy(p).into(), expr_id.into());
                 Ok(Some(current))
             }
-            Expr::UnaryOp { expr, op: op @ (hir_def::expr::UnaryOp::Not | hir_def::expr::UnaryOp::Neg) } => {
+            Expr::UnaryOp { expr, op: op @ (hir_def::hir::UnaryOp::Not | hir_def::hir::UnaryOp::Neg) } => {
                 let Some((operand, current)) = self.lower_expr_to_some_operand(*expr, current)? else {
                     return Ok(None);
                 };
                 let operation = match op {
-                    hir_def::expr::UnaryOp::Not => UnOp::Not,
-                    hir_def::expr::UnaryOp::Neg => UnOp::Neg,
+                    hir_def::hir::UnaryOp::Not => UnOp::Not,
+                    hir_def::hir::UnaryOp::Neg => UnOp::Neg,
                     _ => unreachable!(),
                 };
                 self.push_assignment(
@@ -739,7 +785,7 @@ impl MirLowerCtx<'_> {
             },
             Expr::BinaryOp { lhs, rhs, op } => {
                 let op = op.ok_or(MirLowerError::IncompleteExpr)?;
-                if let hir_def::expr::BinaryOp::Assignment { op } = op {
+                if let hir_def::hir::BinaryOp::Assignment { op } = op {
                     if op.is_some() {
                         not_supported!("assignment with arith op (like +=)");
                     }
@@ -765,13 +811,13 @@ impl MirLowerCtx<'_> {
                     place,
                     Rvalue::CheckedBinaryOp(
                         match op {
-                            hir_def::expr::BinaryOp::LogicOp(op) => match op {
-                                hir_def::expr::LogicOp::And => BinOp::BitAnd, // FIXME: make these short circuit
-                                hir_def::expr::LogicOp::Or => BinOp::BitOr,
+                            hir_def::hir::BinaryOp::LogicOp(op) => match op {
+                                hir_def::hir::LogicOp::And => BinOp::BitAnd, // FIXME: make these short circuit
+                                hir_def::hir::LogicOp::Or => BinOp::BitOr,
                             },
-                            hir_def::expr::BinaryOp::ArithOp(op) => BinOp::from(op),
-                            hir_def::expr::BinaryOp::CmpOp(op) => BinOp::from(op),
-                            hir_def::expr::BinaryOp::Assignment { .. } => unreachable!(), // handled above
+                            hir_def::hir::BinaryOp::ArithOp(op) => BinOp::from(op),
+                            hir_def::hir::BinaryOp::CmpOp(op) => BinOp::from(op),
+                            hir_def::hir::BinaryOp::Assignment { .. } => unreachable!(), // handled above
                         },
                         lhs_op,
                         rhs_op,
@@ -823,7 +869,51 @@ impl MirLowerCtx<'_> {
                 );
                 Ok(Some(current))
             },
-            Expr::Closure { .. } => not_supported!("closure"),
+            Expr::Closure { .. } => {
+                let ty = self.expr_ty(expr_id);
+                let TyKind::Closure(id, _) = ty.kind(Interner) else {
+                    not_supported!("closure with non closure type");
+                };
+                self.result.closures.push(*id);
+                let (captures, _) = self.infer.closure_info(id);
+                let mut operands = vec![];
+                for capture in captures.iter() {
+                    let p = Place {
+                        local: self.binding_local(capture.place.local)?,
+                        projection: capture.place.projections.clone().into_iter().map(|x| {
+                            match x {
+                                ProjectionElem::Deref => ProjectionElem::Deref,
+                                ProjectionElem::Field(x) => ProjectionElem::Field(x),
+                                ProjectionElem::TupleOrClosureField(x) => ProjectionElem::TupleOrClosureField(x),
+                                ProjectionElem::ConstantIndex { offset, min_length, from_end } => ProjectionElem::ConstantIndex { offset, min_length, from_end },
+                                ProjectionElem::Subslice { from, to, from_end } => ProjectionElem::Subslice { from, to, from_end },
+                                ProjectionElem::OpaqueCast(x) => ProjectionElem::OpaqueCast(x),
+                                ProjectionElem::Index(x) => match x { },
+                            }
+                        }).collect(),
+                    };
+                    match &capture.kind {
+                        CaptureKind::ByRef(bk) => {
+                            let tmp: Place = self.temp(capture.ty.clone())?.into();
+                            self.push_assignment(
+                                current,
+                                tmp.clone(),
+                                Rvalue::Ref(bk.clone(), p),
+                                expr_id.into(),
+                            );
+                            operands.push(Operand::Move(tmp));
+                        },
+                        CaptureKind::ByValue => operands.push(Operand::Move(p)),
+                    }
+                }
+                self.push_assignment(
+                    current,
+                    place,
+                    Rvalue::Aggregate(AggregateKind::Closure(ty), operands),
+                    expr_id.into(),
+                );
+                Ok(Some(current))
+            },
             Expr::Tuple { exprs, is_assignee_expr: _ } => {
                 let Some(values) = exprs
                         .iter()
@@ -893,7 +983,7 @@ impl MirLowerCtx<'_> {
                 let index = name
                     .as_tuple_index()
                     .ok_or(MirLowerError::TypeError("named field on tuple"))?;
-                place.projection.push(ProjectionElem::TupleField(index))
+                place.projection.push(ProjectionElem::TupleOrClosureField(index))
             } else {
                 let field =
                     self.infer.field_resolution(expr_id).ok_or(MirLowerError::UnresolvedField)?;
@@ -910,7 +1000,7 @@ impl MirLowerCtx<'_> {
             .size
             .bytes_usize();
         let bytes = match l {
-            hir_def::expr::Literal::String(b) => {
+            hir_def::hir::Literal::String(b) => {
                 let b = b.as_bytes();
                 let mut data = vec![];
                 data.extend(0usize.to_le_bytes());
@@ -919,7 +1009,7 @@ impl MirLowerCtx<'_> {
                 mm.insert(0, b.to_vec());
                 return Ok(Operand::from_concrete_const(data, mm, ty));
             }
-            hir_def::expr::Literal::ByteString(b) => {
+            hir_def::hir::Literal::ByteString(b) => {
                 let mut data = vec![];
                 data.extend(0usize.to_le_bytes());
                 data.extend(b.len().to_le_bytes());
@@ -927,11 +1017,11 @@ impl MirLowerCtx<'_> {
                 mm.insert(0, b.to_vec());
                 return Ok(Operand::from_concrete_const(data, mm, ty));
             }
-            hir_def::expr::Literal::Char(c) => u32::from(*c).to_le_bytes().into(),
-            hir_def::expr::Literal::Bool(b) => vec![*b as u8],
-            hir_def::expr::Literal::Int(x, _) => x.to_le_bytes()[0..size].into(),
-            hir_def::expr::Literal::Uint(x, _) => x.to_le_bytes()[0..size].into(),
-            hir_def::expr::Literal::Float(f, _) => match size {
+            hir_def::hir::Literal::Char(c) => u32::from(*c).to_le_bytes().into(),
+            hir_def::hir::Literal::Bool(b) => vec![*b as u8],
+            hir_def::hir::Literal::Int(x, _) => x.to_le_bytes()[0..size].into(),
+            hir_def::hir::Literal::Uint(x, _) => x.to_le_bytes()[0..size].into(),
+            hir_def::hir::Literal::Float(f, _) => match size {
                 8 => f.into_f64().to_le_bytes().into(),
                 4 => f.into_f32().to_le_bytes().into(),
                 _ => {
@@ -1119,19 +1209,18 @@ impl MirLowerCtx<'_> {
             // bad as we may emit end (unneccessary unreachable block) for unterminating loop, but
             // it should not affect correctness.
             self.current_loop_end()?;
-            self.labeled_loop_blocks.insert(
-                self.body.labels[label].name.clone(),
-                self.current_loop_blocks.as_ref().unwrap().clone(),
-            )
+            self.labeled_loop_blocks
+                .insert(label, self.current_loop_blocks.as_ref().unwrap().clone())
         } else {
             None
         };
         self.set_goto(prev_block, begin);
         f(self, begin)?;
-        let my = mem::replace(&mut self.current_loop_blocks, prev)
-            .ok_or(MirLowerError::ImplementationError("current_loop_blocks is corrupt"))?;
+        let my = mem::replace(&mut self.current_loop_blocks, prev).ok_or(
+            MirLowerError::ImplementationError("current_loop_blocks is corrupt".to_string()),
+        )?;
         if let Some(prev) = prev_label {
-            self.labeled_loop_blocks.insert(self.body.labels[label.unwrap()].name.clone(), prev);
+            self.labeled_loop_blocks.insert(label.unwrap(), prev);
         }
         Ok(my.end)
     }
@@ -1161,7 +1250,9 @@ impl MirLowerCtx<'_> {
         let r = match self
             .current_loop_blocks
             .as_mut()
-            .ok_or(MirLowerError::ImplementationError("Current loop access out of loop"))?
+            .ok_or(MirLowerError::ImplementationError(
+                "Current loop access out of loop".to_string(),
+            ))?
             .end
         {
             Some(x) => x,
@@ -1169,7 +1260,9 @@ impl MirLowerCtx<'_> {
                 let s = self.new_basic_block();
                 self.current_loop_blocks
                     .as_mut()
-                    .ok_or(MirLowerError::ImplementationError("Current loop access out of loop"))?
+                    .ok_or(MirLowerError::ImplementationError(
+                        "Current loop access out of loop".to_string(),
+                    ))?
                     .end = Some(s);
                 s
             }
@@ -1183,7 +1276,7 @@ impl MirLowerCtx<'_> {
 
     /// This function push `StorageLive` statement for the binding, and applies changes to add `StorageDead` in
     /// the appropriated places.
-    fn push_storage_live(&mut self, b: BindingId, current: BasicBlockId) {
+    fn push_storage_live(&mut self, b: BindingId, current: BasicBlockId) -> Result<()> {
         // Current implementation is wrong. It adds no `StorageDead` at the end of scope, and before each break
         // and continue. It just add a `StorageDead` before the `StorageLive`, which is not wrong, but unneeeded in
         // the proper implementation. Due this limitation, implementing a borrow checker on top of this mir will falsely
@@ -1208,9 +1301,10 @@ impl MirLowerCtx<'_> {
             .copied()
             .map(MirSpan::PatId)
             .unwrap_or(MirSpan::Unknown);
-        let l = self.result.binding_locals[b];
+        let l = self.binding_local(b)?;
         self.push_statement(current, StatementKind::StorageDead(l).with_span(span));
         self.push_statement(current, StatementKind::StorageLive(l).with_span(span));
+        Ok(())
     }
 
     fn resolve_lang_item(&self, item: LangItem) -> Result<LangItemTarget> {
@@ -1220,14 +1314,14 @@ impl MirLowerCtx<'_> {
 
     fn lower_block_to_place(
         &mut self,
-        statements: &[hir_def::expr::Statement],
+        statements: &[hir_def::hir::Statement],
         mut current: BasicBlockId,
         tail: Option<ExprId>,
         place: Place,
     ) -> Result<Option<Idx<BasicBlock>>> {
         for statement in statements.iter() {
             match statement {
-                hir_def::expr::Statement::Let { pat, initializer, else_branch, type_ref: _ } => {
+                hir_def::hir::Statement::Let { pat, initializer, else_branch, type_ref: _ } => {
                     if let Some(expr_id) = initializer {
                         let else_block;
                         let Some((init_place, c)) =
@@ -1258,12 +1352,18 @@ impl MirLowerCtx<'_> {
                             }
                         }
                     } else {
+                        let mut err = None;
                         self.body.walk_bindings_in_pat(*pat, |b| {
-                            self.push_storage_live(b, current);
+                            if let Err(e) = self.push_storage_live(b, current) {
+                                err = Some(e);
+                            }
                         });
+                        if let Some(e) = err {
+                            return Err(e);
+                        }
                     }
                 }
-                hir_def::expr::Statement::Expr { expr, has_semi: _ } => {
+                hir_def::hir::Statement::Expr { expr, has_semi: _ } => {
                     let Some((_, c)) = self.lower_expr_as_place(current, *expr, true)? else {
                         return Ok(None);
                     };
@@ -1276,6 +1376,67 @@ impl MirLowerCtx<'_> {
             None => Ok(Some(current)),
         }
     }
+
+    fn lower_params_and_bindings(
+        &mut self,
+        params: impl Iterator<Item = (PatId, Ty)> + Clone,
+        pick_binding: impl Fn(BindingId) -> bool,
+    ) -> Result<BasicBlockId> {
+        let base_param_count = self.result.param_locals.len();
+        self.result.param_locals.extend(params.clone().map(|(x, ty)| {
+            let local_id = self.result.locals.alloc(Local { ty });
+            if let Pat::Bind { id, subpat: None } = self.body[x] {
+                if matches!(
+                    self.body.bindings[id].mode,
+                    BindingAnnotation::Unannotated | BindingAnnotation::Mutable
+                ) {
+                    self.result.binding_locals.insert(id, local_id);
+                }
+            }
+            local_id
+        }));
+        // and then rest of bindings
+        for (id, _) in self.body.bindings.iter() {
+            if !pick_binding(id) {
+                continue;
+            }
+            if !self.result.binding_locals.contains_idx(id) {
+                self.result
+                    .binding_locals
+                    .insert(id, self.result.locals.alloc(Local { ty: self.infer[id].clone() }));
+            }
+        }
+        let mut current = self.result.start_block;
+        for ((param, _), local) in
+            params.zip(self.result.param_locals.clone().into_iter().skip(base_param_count))
+        {
+            if let Pat::Bind { id, .. } = self.body[param] {
+                if local == self.binding_local(id)? {
+                    continue;
+                }
+            }
+            let r = self.pattern_match(
+                current,
+                None,
+                local.into(),
+                self.result.locals[local].ty.clone(),
+                param,
+                BindingAnnotation::Unannotated,
+            )?;
+            if let Some(b) = r.1 {
+                self.set_terminator(b, Terminator::Unreachable);
+            }
+            current = r.0;
+        }
+        Ok(current)
+    }
+
+    fn binding_local(&self, b: BindingId) -> Result<LocalId> {
+        match self.result.binding_locals.get(b) {
+            Some(x) => Ok(*x),
+            None => Err(MirLowerError::UnaccessableLocal),
+        }
+    }
 }
 
 fn cast_kind(source_ty: &Ty, target_ty: &Ty) -> Result<CastKind> {
@@ -1299,6 +1460,87 @@ fn cast_kind(source_ty: &Ty, target_ty: &Ty) -> Result<CastKind> {
     })
 }
 
+pub fn mir_body_for_closure_query(
+    db: &dyn HirDatabase,
+    closure: ClosureId,
+) -> Result<Arc<MirBody>> {
+    let (owner, expr) = db.lookup_intern_closure(closure.into());
+    let body = db.body(owner);
+    let infer = db.infer(owner);
+    let Expr::Closure { args, body: root, .. } = &body[expr] else {
+        implementation_error!("closure expression is not closure");
+    };
+    let TyKind::Closure(_, substs) = &infer[expr].kind(Interner) else {
+        implementation_error!("closure expression is not closure");
+    };
+    let (captures, _) = infer.closure_info(&closure);
+    let mut ctx = MirLowerCtx::new(db, owner, &body, &infer);
+    ctx.result.arg_count = args.len() + 1;
+    // 0 is return local
+    ctx.result.locals.alloc(Local { ty: infer[*root].clone() });
+    ctx.result.locals.alloc(Local { ty: infer[expr].clone() });
+    let Some(sig) = substs.at(Interner, 0).assert_ty_ref(Interner).callable_sig(db) else {
+        implementation_error!("closure has not callable sig");
+    };
+    let current = ctx.lower_params_and_bindings(
+        args.iter().zip(sig.params().iter()).map(|(x, y)| (*x, y.clone())),
+        |_| true,
+    )?;
+    if let Some(b) = ctx.lower_expr_to_place(*root, return_slot().into(), current)? {
+        ctx.set_terminator(b, Terminator::Return);
+    }
+    let mut upvar_map: FxHashMap<LocalId, Vec<(&CapturedItem, usize)>> = FxHashMap::default();
+    for (i, capture) in captures.iter().enumerate() {
+        let local = ctx.binding_local(capture.place.local)?;
+        upvar_map.entry(local).or_default().push((capture, i));
+    }
+    let mut err = None;
+    let closure_local = ctx.result.locals.iter().nth(1).unwrap().0;
+    ctx.result.walk_places(|p| {
+        if let Some(x) = upvar_map.get(&p.local) {
+            let r = x.iter().find(|x| {
+                if p.projection.len() < x.0.place.projections.len() {
+                    return false;
+                }
+                for (x, y) in p.projection.iter().zip(x.0.place.projections.iter()) {
+                    match (x, y) {
+                        (ProjectionElem::Deref, ProjectionElem::Deref) => (),
+                        (ProjectionElem::Field(x), ProjectionElem::Field(y)) if x == y => (),
+                        (
+                            ProjectionElem::TupleOrClosureField(x),
+                            ProjectionElem::TupleOrClosureField(y),
+                        ) if x == y => (),
+                        _ => return false,
+                    }
+                }
+                true
+            });
+            match r {
+                Some(x) => {
+                    p.local = closure_local;
+                    let prev_projs =
+                        mem::replace(&mut p.projection, vec![PlaceElem::TupleOrClosureField(x.1)]);
+                    if x.0.kind != CaptureKind::ByValue {
+                        p.projection.push(ProjectionElem::Deref);
+                    }
+                    p.projection.extend(prev_projs.into_iter().skip(x.0.place.projections.len()));
+                }
+                None => err = Some(p.clone()),
+            }
+        }
+    });
+    ctx.result.binding_locals = ctx
+        .result
+        .binding_locals
+        .into_iter()
+        .filter(|x| ctx.body[x.0].owner == Some(expr))
+        .collect();
+    if let Some(err) = err {
+        return Err(MirLowerError::UnresolvedUpvar(err));
+    }
+    Ok(Arc::new(ctx.result))
+}
+
 pub fn mir_body_query(db: &dyn HirDatabase, def: DefWithBodyId) -> Result<Arc<MirBody>> {
     let _p = profile::span("mir_body_query").detail(|| match def {
         DefWithBodyId::FunctionId(it) => db.function_data(it).name.to_string(),
@@ -1336,86 +1578,29 @@ pub fn lower_to_mir(
     if let Some((_, x)) = infer.type_mismatches().next() {
         return Err(MirLowerError::TypeMismatch(x.clone()));
     }
-    let mut basic_blocks = Arena::new();
-    let start_block =
-        basic_blocks.alloc(BasicBlock { statements: vec![], terminator: None, is_cleanup: false });
-    let mut locals = Arena::new();
+    let mut ctx = MirLowerCtx::new(db, owner, body, infer);
     // 0 is return local
-    locals.alloc(Local { ty: infer[root_expr].clone() });
-    let mut binding_locals: ArenaMap<BindingId, LocalId> = ArenaMap::new();
+    ctx.result.locals.alloc(Local { ty: infer[root_expr].clone() });
+    let binding_picker = |b: BindingId| {
+        if root_expr == body.body_expr {
+            body[b].owner.is_none()
+        } else {
+            body[b].owner == Some(root_expr)
+        }
+    };
     // 1 to param_len is for params
-    let param_locals: Vec<LocalId> = if let DefWithBodyId::FunctionId(fid) = owner {
+    let current = if let DefWithBodyId::FunctionId(fid) = owner {
         let substs = TyBuilder::placeholder_subst(db, fid);
         let callable_sig = db.callable_item_signature(fid.into()).substitute(Interner, &substs);
-        body.params
-            .iter()
-            .zip(callable_sig.params().iter())
-            .map(|(&x, ty)| {
-                let local_id = locals.alloc(Local { ty: ty.clone() });
-                if let Pat::Bind { id, subpat: None } = body[x] {
-                    if matches!(
-                        body.bindings[id].mode,
-                        BindingAnnotation::Unannotated | BindingAnnotation::Mutable
-                    ) {
-                        binding_locals.insert(id, local_id);
-                    }
-                }
-                local_id
-            })
-            .collect()
+        ctx.lower_params_and_bindings(
+            body.params.iter().zip(callable_sig.params().iter()).map(|(x, y)| (*x, y.clone())),
+            binding_picker,
+        )?
     } else {
-        if !body.params.is_empty() {
-            return Err(MirLowerError::TypeError("Unexpected parameter for non function body"));
-        }
-        vec![]
+        ctx.lower_params_and_bindings([].into_iter(), binding_picker)?
     };
-    // and then rest of bindings
-    for (id, _) in body.bindings.iter() {
-        if !binding_locals.contains_idx(id) {
-            binding_locals.insert(id, locals.alloc(Local { ty: infer[id].clone() }));
-        }
-    }
-    let mir = MirBody {
-        basic_blocks,
-        locals,
-        start_block,
-        binding_locals,
-        param_locals,
-        owner,
-        arg_count: body.params.len(),
-    };
-    let mut ctx = MirLowerCtx {
-        result: mir,
-        db,
-        infer,
-        body,
-        owner,
-        current_loop_blocks: None,
-        labeled_loop_blocks: Default::default(),
-        discr_temp: None,
-    };
-    let mut current = start_block;
-    for (&param, local) in body.params.iter().zip(ctx.result.param_locals.clone().into_iter()) {
-        if let Pat::Bind { id, .. } = body[param] {
-            if local == ctx.result.binding_locals[id] {
-                continue;
-            }
-        }
-        let r = ctx.pattern_match(
-            current,
-            None,
-            local.into(),
-            ctx.result.locals[local].ty.clone(),
-            param,
-            BindingAnnotation::Unannotated,
-        )?;
-        if let Some(b) = r.1 {
-            ctx.set_terminator(b, Terminator::Unreachable);
-        }
-        current = r.0;
-    }
     if let Some(b) = ctx.lower_expr_to_place(root_expr, return_slot().into(), current)? {
-        ctx.result.basic_blocks[b].terminator = Some(Terminator::Return);
+        ctx.set_terminator(b, Terminator::Return);
     }
     Ok(ctx.result)
 }

crates/hir-ty/src/mir/lower/as_place.rs

@@ -141,7 +141,7 @@ impl MirLowerCtx<'_> {
                 }
             }
             Expr::UnaryOp { expr, op } => match op {
-                hir_def::expr::UnaryOp::Deref => {
+                hir_def::hir::UnaryOp::Deref => {
                     if !matches!(
                         self.expr_ty(*expr).kind(Interner),
                         TyKind::Ref(..) | TyKind::Raw(..)

crates/hir-ty/src/mir/lower/pattern_matching.rs

@@ -1,5 +1,7 @@
 //! MIR lowering for patterns
 
+use crate::utils::pattern_matching_dereference_count;
+
 use super::*;
 
 macro_rules! not_supported {
@@ -52,7 +54,7 @@ impl MirLowerCtx<'_> {
                     args,
                     *ellipsis,
                     subst.iter(Interner).enumerate().map(|(i, x)| {
-                        (PlaceElem::TupleField(i), x.assert_ty_ref(Interner).clone())
+                        (PlaceElem::TupleOrClosureField(i), x.assert_ty_ref(Interner).clone())
                     }),
                     &cond_place,
                     binding_mode,
@@ -142,7 +144,7 @@ impl MirLowerCtx<'_> {
                 if matches!(mode, BindingAnnotation::Ref | BindingAnnotation::RefMut) {
                     binding_mode = mode;
                 }
-                self.push_storage_live(*id, current);
+                self.push_storage_live(*id, current)?;
                 self.push_assignment(
                     current,
                     target_place.into(),
@@ -387,13 +389,6 @@ fn pattern_matching_dereference(
     binding_mode: &mut BindingAnnotation,
     cond_place: &mut Place,
 ) {
-    while let Some((ty, _, mu)) = cond_ty.as_reference() {
-        if mu == Mutability::Mut && *binding_mode != BindingAnnotation::Ref {
-            *binding_mode = BindingAnnotation::RefMut;
-        } else {
-            *binding_mode = BindingAnnotation::Ref;
-        }
-        *cond_ty = ty.clone();
-        cond_place.projection.push(ProjectionElem::Deref);
-    }
+    let cnt = pattern_matching_dereference_count(cond_ty, binding_mode);
+    cond_place.projection.extend((0..cnt).map(|_| ProjectionElem::Deref));
 }

crates/hir-ty/src/mir/pretty.rs

@@ -1,8 +1,11 @@
 //! A pretty-printer for MIR.
 
-use std::fmt::{Debug, Display, Write};
+use std::{
+    fmt::{Debug, Display, Write},
+    mem,
+};
 
-use hir_def::{body::Body, expr::BindingId};
+use hir_def::{body::Body, hir::BindingId};
 use hir_expand::name::Name;
 use la_arena::ArenaMap;
 
@@ -20,7 +23,7 @@ impl MirBody {
     pub fn pretty_print(&self, db: &dyn HirDatabase) -> String {
         let hir_body = db.body(self.owner);
         let mut ctx = MirPrettyCtx::new(self, &hir_body, db);
-        ctx.for_body();
+        ctx.for_body(ctx.body.owner);
         ctx.result
     }
 
@@ -42,7 +45,7 @@ struct MirPrettyCtx<'a> {
     hir_body: &'a Body,
     db: &'a dyn HirDatabase,
     result: String,
-    ident: String,
+    indent: String,
     local_to_binding: ArenaMap<LocalId, BindingId>,
 }
 
@@ -88,22 +91,43 @@ impl Display for LocalName {
 }
 
 impl<'a> MirPrettyCtx<'a> {
-    fn for_body(&mut self) {
-        wln!(self, "// {:?}", self.body.owner);
+    fn for_body(&mut self, name: impl Debug) {
+        wln!(self, "// {:?}", name);
         self.with_block(|this| {
             this.locals();
             wln!(this);
             this.blocks();
         });
+        for &closure in &self.body.closures {
+            let body = match self.db.mir_body_for_closure(closure) {
+                Ok(x) => x,
+                Err(e) => {
+                    wln!(self, "// error in {closure:?}: {e:?}");
+                    continue;
+                }
+            };
+            let result = mem::take(&mut self.result);
+            let indent = mem::take(&mut self.indent);
+            let mut ctx = MirPrettyCtx {
+                body: &body,
+                local_to_binding: body.binding_locals.iter().map(|(x, y)| (*y, x)).collect(),
+                result,
+                indent,
+                ..*self
+            };
+            ctx.for_body(closure);
+            self.result = ctx.result;
+            self.indent = ctx.indent;
+        }
     }
 
     fn with_block(&mut self, f: impl FnOnce(&mut MirPrettyCtx<'_>)) {
-        self.ident += "    ";
+        self.indent += "    ";
         wln!(self, "{{");
         f(self);
         for _ in 0..4 {
             self.result.pop();
-            self.ident.pop();
+            self.indent.pop();
         }
         wln!(self, "}}");
     }
@@ -114,7 +138,7 @@ impl<'a> MirPrettyCtx<'a> {
             body,
             db,
             result: String::new(),
-            ident: String::new(),
+            indent: String::new(),
             local_to_binding,
             hir_body,
         }
@@ -122,7 +146,7 @@ impl<'a> MirPrettyCtx<'a> {
 
     fn write_line(&mut self) {
         self.result.push('\n');
-        self.result += &self.ident;
+        self.result += &self.indent;
     }
 
     fn write(&mut self, line: &str) {
@@ -247,7 +271,7 @@ impl<'a> MirPrettyCtx<'a> {
                         }
                     }
                 }
-                ProjectionElem::TupleField(x) => {
+                ProjectionElem::TupleOrClosureField(x) => {
                     f(this, local, head);
                     w!(this, ".{}", x);
                 }
@@ -302,6 +326,11 @@ impl<'a> MirPrettyCtx<'a> {
                 self.operand_list(x);
                 w!(self, ")");
             }
+            Rvalue::Aggregate(AggregateKind::Closure(_), x) => {
+                w!(self, "Closure(");
+                self.operand_list(x);
+                w!(self, ")");
+            }
             Rvalue::Aggregate(AggregateKind::Union(_, _), x) => {
                 w!(self, "Union(");
                 self.operand_list(x);

crates/hir-ty/src/tests.rs

@@ -17,7 +17,7 @@ use expect_test::Expect;
 use hir_def::{
     body::{Body, BodySourceMap, SyntheticSyntax},
     db::{DefDatabase, InternDatabase},
-    expr::{ExprId, PatId},
+    hir::{ExprId, PatId},
     item_scope::ItemScope,
     nameres::DefMap,
     src::HasSource,
@@ -198,8 +198,8 @@ fn check_impl(ra_fixture: &str, allow_none: bool, only_types: bool, display_sour
 
         for (expr_or_pat, mismatch) in inference_result.type_mismatches() {
             let Some(node) = (match expr_or_pat {
-                hir_def::expr::ExprOrPatId::ExprId(expr) => expr_node(&body_source_map, expr, &db),
-                hir_def::expr::ExprOrPatId::PatId(pat) => pat_node(&body_source_map, pat, &db),
+                hir_def::hir::ExprOrPatId::ExprId(expr) => expr_node(&body_source_map, expr, &db),
+                hir_def::hir::ExprOrPatId::PatId(pat) => pat_node(&body_source_map, pat, &db),
             }) else { continue; };
             let range = node.as_ref().original_file_range(&db);
             let actual = format!(

crates/hir-ty/src/tests/coercion.rs

@@ -575,7 +575,7 @@ fn two_closures_lub() {
 fn foo(c: i32) {
     let add = |a: i32, b: i32| a + b;
     let sub = |a, b| a - b;
-            //^^^^^^^^^^^^ |i32, i32| -> i32
+            //^^^^^^^^^^^^ impl Fn(i32, i32) -> i32
     if c > 42 { add } else { sub };
   //^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ fn(i32, i32) -> i32
 }
@@ -875,6 +875,16 @@ fn test() {
 fn adjust_index() {
     check_no_mismatches(
         r"
+//- minicore: index, slice, coerce_unsized
+fn test() {
+    let x = [1, 2, 3];
+    x[2] = 6;
+ // ^ adjustments: Borrow(Ref(Mut))
+}
+    ",
+    );
+    check_no_mismatches(
+        r"
 //- minicore: index
 struct Struct;
 impl core::ops::Index<usize> for Struct {
@@ -902,3 +912,32 @@ fn test() {
 }",
     );
 }
+
+#[test]
+fn regression_14443_dyn_coercion_block_impls() {
+    check_no_mismatches(
+        r#"
+//- minicore: coerce_unsized
+trait T {}
+
+fn dyn_t(d: &dyn T) {}
+
+fn main() {
+    struct A;
+    impl T for A {}
+
+    let a = A;
+
+    let b = {
+        struct B;
+        impl T for B {}
+
+        B
+    };
+
+    dyn_t(&a);
+    dyn_t(&b);
+}
+"#,
+    )
+}

crates/hir-ty/src/tests/macros.rs

@@ -198,7 +198,7 @@ fn expr_macro_def_expanded_in_various_places() {
             100..119 'for _ ...!() {}': ()
             104..105 '_': {unknown}
             117..119 '{}': ()
-            124..134 '|| spam!()': || -> isize
+            124..134 '|| spam!()': impl Fn() -> isize
             140..156 'while ...!() {}': ()
             154..156 '{}': ()
             161..174 'break spam!()': !
@@ -279,7 +279,7 @@ fn expr_macro_rules_expanded_in_various_places() {
             114..133 'for _ ...!() {}': ()
             118..119 '_': {unknown}
             131..133 '{}': ()
-            138..148 '|| spam!()': || -> isize
+            138..148 '|| spam!()': impl Fn() -> isize
             154..170 'while ...!() {}': ()
             168..170 '{}': ()
             175..188 'break spam!()': !

crates/hir-ty/src/tests/method_resolution.rs

@@ -388,6 +388,24 @@ mod bar_test {
     );
 }
 
+#[test]
+fn infer_trait_method_multiple_mutable_reference() {
+    check_types(
+        r#"
+trait Trait {
+    fn method(&mut self) -> i32 { 5 }
+}
+struct S;
+impl Trait for &mut &mut S {}
+fn test() {
+    let s = &mut &mut &mut S;
+    s.method();
+  //^^^^^^^^^^ i32
+}
+        "#,
+    );
+}
+
 #[test]
 fn infer_trait_method_generic_1() {
     // the trait implementation is intentionally incomplete -- it shouldn't matter
@@ -1722,7 +1740,7 @@ fn test() {
     Foo.foo();
   //^^^ adjustments: Borrow(Ref(Not))
     (&Foo).foo();
-  // ^^^^ adjustments: ,
+  // ^^^^ adjustments: Deref(None), Borrow(Ref(Not))
 }
 "#,
     );

crates/hir-ty/src/tests/patterns.rs

@@ -70,8 +70,8 @@ fn infer_pattern() {
             228..233 '&true': &bool
             229..233 'true': bool
             234..236 '{}': ()
-            246..252 'lambda': |u64, u64, i32| -> i32
-            255..287 '|a: u6...b; c }': |u64, u64, i32| -> i32
+            246..252 'lambda': impl Fn(u64, u64, i32) -> i32
+            255..287 '|a: u6...b; c }': impl Fn(u64, u64, i32) -> i32
             256..257 'a': u64
             264..265 'b': u64
             267..268 'c': i32
@@ -476,7 +476,7 @@ fn infer_adt_pattern() {
             183..184 'x': usize
             190..191 'x': usize
             201..205 'E::B': E
-            209..212 'foo': {unknown}
+            209..212 'foo': bool
             216..217 '1': usize
             227..231 'E::B': E
             235..237 '10': usize
@@ -677,25 +677,25 @@ fn test() {
             51..58 'loop {}': !
             56..58 '{}': ()
             72..171 '{     ... x); }': ()
-            78..81 'foo': fn foo<&(i32, &str), i32, |&(i32, &str)| -> i32>(&(i32, &str), |&(i32, &str)| -> i32) -> i32
+            78..81 'foo': fn foo<&(i32, &str), i32, impl Fn(&(i32, &str)) -> i32>(&(i32, &str), impl Fn(&(i32, &str)) -> i32) -> i32
             78..105 'foo(&(...y)| x)': i32
             82..91 '&(1, "a")': &(i32, &str)
             83..91 '(1, "a")': (i32, &str)
             84..85 '1': i32
             87..90 '"a"': &str
-            93..104 '|&(x, y)| x': |&(i32, &str)| -> i32
+            93..104 '|&(x, y)| x': impl Fn(&(i32, &str)) -> i32
             94..101 '&(x, y)': &(i32, &str)
             95..101 '(x, y)': (i32, &str)
             96..97 'x': i32
             99..100 'y': &str
             103..104 'x': i32
-            142..145 'foo': fn foo<&(i32, &str), &i32, |&(i32, &str)| -> &i32>(&(i32, &str), |&(i32, &str)| -> &i32) -> &i32
+            142..145 'foo': fn foo<&(i32, &str), &i32, impl Fn(&(i32, &str)) -> &i32>(&(i32, &str), impl Fn(&(i32, &str)) -> &i32) -> &i32
             142..168 'foo(&(...y)| x)': &i32
             146..155 '&(1, "a")': &(i32, &str)
             147..155 '(1, "a")': (i32, &str)
             148..149 '1': i32
             151..154 '"a"': &str
-            157..167 '|(x, y)| x': |&(i32, &str)| -> &i32
+            157..167 '|(x, y)| x': impl Fn(&(i32, &str)) -> &i32
             158..164 '(x, y)': (i32, &str)
             159..160 'x': &i32
             162..163 'y': &&str

crates/hir-ty/src/tests/regression.rs

@@ -270,7 +270,7 @@ fn infer_std_crash_5() {
             61..320 '{     ...     }': ()
             75..79 'name': &{unknown}
             82..166 'if doe...     }': &{unknown}
-            85..98 'doesnt_matter': {unknown}
+            85..98 'doesnt_matter': bool
             99..128 '{     ...     }': &{unknown}
             113..118 'first': &{unknown}
             134..166 '{     ...     }': &{unknown}
@@ -279,7 +279,7 @@ fn infer_std_crash_5() {
             181..188 'content': &{unknown}
             191..313 'if ICE...     }': &{unknown}
             194..231 'ICE_RE..._VALUE': {unknown}
-            194..247 'ICE_RE...&name)': {unknown}
+            194..247 'ICE_RE...&name)': bool
             241..246 '&name': &&{unknown}
             242..246 'name': &{unknown}
             248..276 '{     ...     }': &{unknown}
@@ -805,19 +805,19 @@ fn issue_4966() {
             225..229 'iter': T
             244..246 '{}': Vec<A>
             258..402 '{     ...r(); }': ()
-            268..273 'inner': Map<|&f64| -> f64>
-            276..300 'Map { ... 0.0 }': Map<|&f64| -> f64>
-            285..298 '|_: &f64| 0.0': |&f64| -> f64
+            268..273 'inner': Map<impl Fn(&f64) -> f64>
+            276..300 'Map { ... 0.0 }': Map<impl Fn(&f64) -> f64>
+            285..298 '|_: &f64| 0.0': impl Fn(&f64) -> f64
             286..287 '_': &f64
             295..298 '0.0': f64
-            311..317 'repeat': Repeat<Map<|&f64| -> f64>>
-            320..345 'Repeat...nner }': Repeat<Map<|&f64| -> f64>>
-            338..343 'inner': Map<|&f64| -> f64>
-            356..359 'vec': Vec<IntoIterator::Item<Repeat<Map<|&f64| -> f64>>>>
-            362..371 'from_iter': fn from_iter<IntoIterator::Item<Repeat<Map<|&f64| -> f64>>>, Repeat<Map<|&f64| -> f64>>>(Repeat<Map<|&f64| -> f64>>) -> Vec<IntoIterator::Item<Repeat<Map<|&f64| -> f64>>>>
-            362..379 'from_i...epeat)': Vec<IntoIterator::Item<Repeat<Map<|&f64| -> f64>>>>
-            372..378 'repeat': Repeat<Map<|&f64| -> f64>>
-            386..389 'vec': Vec<IntoIterator::Item<Repeat<Map<|&f64| -> f64>>>>
+            311..317 'repeat': Repeat<Map<impl Fn(&f64) -> f64>>
+            320..345 'Repeat...nner }': Repeat<Map<impl Fn(&f64) -> f64>>
+            338..343 'inner': Map<impl Fn(&f64) -> f64>
+            356..359 'vec': Vec<IntoIterator::Item<Repeat<Map<impl Fn(&f64) -> f64>>>>
+            362..371 'from_iter': fn from_iter<IntoIterator::Item<Repeat<Map<impl Fn(&f64) -> f64>>>, Repeat<Map<impl Fn(&f64) -> f64>>>(Repeat<Map<impl Fn(&f64) -> f64>>) -> Vec<IntoIterator::Item<Repeat<Map<impl Fn(&f64) -> f64>>>>
+            362..379 'from_i...epeat)': Vec<IntoIterator::Item<Repeat<Map<impl Fn(&f64) -> f64>>>>
+            372..378 'repeat': Repeat<Map<impl Fn(&f64) -> f64>>
+            386..389 'vec': Vec<IntoIterator::Item<Repeat<Map<impl Fn(&f64) -> f64>>>>
             386..399 'vec.foo_bar()': {unknown}
         "#]],
     );
@@ -852,7 +852,7 @@ fn main() {
             123..126 'S()': S<i32>
             132..133 's': S<i32>
             132..144 's.g(|_x| {})': ()
-            136..143 '|_x| {}': |&i32| -> ()
+            136..143 '|_x| {}': impl Fn(&i32)
             137..139 '_x': &i32
             141..143 '{}': ()
             150..151 's': S<i32>
@@ -1067,6 +1067,23 @@ fn parse_arule() {
     )
 }
 
+#[test]
+fn nested_closure() {
+    check_types(
+        r#"
+//- minicore: fn, option
+
+fn map<T, U>(o: Option<T>, f: impl FnOnce(T) -> U) -> Option<U> { loop {} }
+
+fn test() {
+    let o = Some(Some(2));
+    map(o, |s| map(s, |x| x));
+                    // ^ i32
+}
+        "#,
+    );
+}
+
 #[test]
 fn call_expected_type_closure() {
     check_types(
@@ -1759,13 +1776,14 @@ const C: usize = 2 + 2;
 
 #[test]
 fn regression_14456() {
-    check_no_mismatches(
+    check_types(
         r#"
 //- minicore: future
 async fn x() {}
 fn f() {
     let fut = x();
-    let t = [0u8; 2 + 2];
+    let t = [0u8; { let a = 2 + 2; a }];
+      //^ [u8; 4]
 }
 "#,
     );
@@ -1802,3 +1820,21 @@ where
 "#,
     );
 }
+
+#[test]
+fn match_ergonomics_with_binding_modes_interaction() {
+    check_types(
+        r"
+enum E { A }
+fn foo() {
+    match &E::A {
+        b @ (x @ E::A | x) => {
+            b;
+          //^ &E
+            x;
+          //^ &E
+        }
+    }
+}",
+    );
+}

crates/hir-ty/src/tests/simple.rs

@@ -1906,8 +1906,8 @@ fn closure_return() {
         "#,
         expect![[r#"
             16..58 '{     ...; }; }': u32
-            26..27 'x': || -> usize
-            30..55 '|| -> ...n 1; }': || -> usize
+            26..27 'x': impl Fn() -> usize
+            30..55 '|| -> ...n 1; }': impl Fn() -> usize
             42..55 '{ return 1; }': usize
             44..52 'return 1': !
             51..52 '1': usize
@@ -1925,8 +1925,8 @@ fn closure_return_unit() {
         "#,
         expect![[r#"
             16..47 '{     ...; }; }': u32
-            26..27 'x': || -> ()
-            30..44 '|| { return; }': || -> ()
+            26..27 'x': impl Fn()
+            30..44 '|| { return; }': impl Fn()
             33..44 '{ return; }': ()
             35..41 'return': !
         "#]],
@@ -1943,8 +1943,8 @@ fn closure_return_inferred() {
         "#,
         expect![[r#"
             16..46 '{     ..." }; }': u32
-            26..27 'x': || -> &str
-            30..43 '|| { "test" }': || -> &str
+            26..27 'x': impl Fn() -> &str
+            30..43 '|| { "test" }': impl Fn() -> &str
             33..43 '{ "test" }': &str
             35..41 '"test"': &str
         "#]],
@@ -2050,7 +2050,7 @@ fn fn_pointer_return() {
             47..120 '{     ...hod; }': ()
             57..63 'vtable': Vtable
             66..90 'Vtable...| {} }': Vtable
-            83..88 '|| {}': || -> ()
+            83..88 '|| {}': impl Fn()
             86..88 '{}': ()
             100..101 'm': fn()
             104..110 'vtable': Vtable
@@ -2142,9 +2142,9 @@ fn main() {
             149..151 'Ok': Ok<(), ()>(()) -> Result<(), ()>
             149..155 'Ok(())': Result<(), ()>
             152..154 '()': ()
-            167..171 'test': fn test<(), (), || -> impl Future<Output = Result<(), ()>>, impl Future<Output = Result<(), ()>>>(|| -> impl Future<Output = Result<(), ()>>)
+            167..171 'test': fn test<(), (), impl Fn() -> impl Future<Output = Result<(), ()>>, impl Future<Output = Result<(), ()>>>(impl Fn() -> impl Future<Output = Result<(), ()>>)
             167..228 'test(|...    })': ()
-            172..227 '|| asy...     }': || -> impl Future<Output = Result<(), ()>>
+            172..227 '|| asy...     }': impl Fn() -> impl Future<Output = Result<(), ()>>
             175..227 'async ...     }': impl Future<Output = Result<(), ()>>
             191..205 'return Err(())': !
             198..201 'Err': Err<(), ()>(()) -> Result<(), ()>
@@ -2270,8 +2270,8 @@ fn infer_labelled_break_with_val() {
         "#,
         expect![[r#"
             9..335 '{     ...  }; }': ()
-            19..21 '_x': || -> bool
-            24..332 '|| 'ou...     }': || -> bool
+            19..21 '_x': impl Fn() -> bool
+            24..332 '|| 'ou...     }': impl Fn() -> bool
             27..332 ''outer...     }': bool
             40..332 '{     ...     }': ()
             54..59 'inner': i8
@@ -2695,6 +2695,179 @@ impl B for Astruct {}
     )
 }
 
+#[test]
+fn capture_kinds_simple() {
+    check_types(
+        r#"
+struct S;
+
+impl S {
+    fn read(&self) -> &S { self }
+    fn write(&mut self) -> &mut S { self }
+    fn consume(self) -> S { self }
+}
+
+fn f() {
+    let x = S;
+    let c1 = || x.read();
+      //^^ impl Fn() -> &S
+    let c2 = || x.write();
+      //^^ impl FnMut() -> &mut S
+    let c3 = || x.consume();
+      //^^ impl FnOnce() -> S
+    let c3 = || x.consume().consume().consume();
+      //^^ impl FnOnce() -> S
+    let c3 = || x.consume().write().read();
+      //^^ impl FnOnce() -> &S
+    let x = &mut x;
+    let c1 = || x.write();
+      //^^ impl FnMut() -> &mut S
+    let x = S;
+    let c1 = || { let ref t = x; t };
+      //^^ impl Fn() -> &S
+    let c2 = || { let ref mut t = x; t };
+      //^^ impl FnMut() -> &mut S
+    let c3 = || { let t = x; t };
+      //^^ impl FnOnce() -> S
+}
+    "#,
+    )
+}
+
+#[test]
+fn capture_kinds_closure() {
+    check_types(
+        r#"
+//- minicore: copy, fn
+fn f() {
+    let mut x = 2;
+    x = 5;
+    let mut c1 = || { x = 3; x };
+      //^^^^^^ impl FnMut() -> i32
+    let mut c2 = || { c1() };
+      //^^^^^^ impl FnMut() -> i32
+    let mut c1 = || { x };
+      //^^^^^^ impl Fn() -> i32
+    let mut c2 = || { c1() };
+      //^^^^^^ impl Fn() -> i32
+    struct X;
+    let x = X;
+    let mut c1 = || { x };
+      //^^^^^^ impl FnOnce() -> X
+    let mut c2 = || { c1() };
+      //^^^^^^ impl FnOnce() -> X
+}
+        "#,
+    );
+}
+
+#[test]
+fn capture_kinds_overloaded_deref() {
+    check_types(
+        r#"
+//- minicore: fn, deref_mut
+use core::ops::{Deref, DerefMut};
+
+struct Foo;
+impl Deref for Foo {
+    type Target = (i32, u8);
+    fn deref(&self) -> &(i32, u8) {
+        &(5, 2)
+    }
+}
+impl DerefMut for Foo {
+    fn deref_mut(&mut self) -> &mut (i32, u8) {
+        &mut (5, 2)
+    }
+}
+fn test() {
+    let mut x = Foo;
+    let c1 = || *x;
+      //^^ impl Fn() -> (i32, u8)
+    let c2 = || { *x = (2, 5); };
+      //^^ impl FnMut()
+    let c3 = || { x.1 };
+      //^^ impl Fn() -> u8
+    let c4 = || { x.1 = 6; };
+      //^^ impl FnMut()
+}
+       "#,
+    );
+}
+
+#[test]
+fn capture_kinds_with_copy_types() {
+    check_types(
+        r#"
+//- minicore: copy, clone, derive
+#[derive(Clone, Copy)]
+struct Copy;
+struct NotCopy;
+#[derive(Clone, Copy)]
+struct Generic<T>(T);
+
+trait Tr {
+    type Assoc;
+}
+
+impl Tr for Copy {
+    type Assoc = NotCopy;
+}
+
+#[derive(Clone, Copy)]
+struct AssocGeneric<T: Tr>(T::Assoc);
+
+fn f() {
+    let a = Copy;
+    let b = NotCopy;
+    let c = Generic(Copy);
+    let d = Generic(NotCopy);
+    let e: AssocGeneric<Copy> = AssocGeneric(NotCopy);
+    let c1 = || a;
+      //^^ impl Fn() -> Copy
+    let c2 = || b;
+      //^^ impl FnOnce() -> NotCopy
+    let c3 = || c;
+      //^^ impl Fn() -> Generic<Copy>
+    let c3 = || d;
+      //^^ impl FnOnce() -> Generic<NotCopy>
+    let c3 = || e;
+      //^^ impl FnOnce() -> AssocGeneric<Copy>
+}
+    "#,
+    )
+}
+
+#[test]
+fn derive_macro_should_work_for_associated_type() {
+    check_types(
+        r#"
+//- minicore: copy, clone, derive
+#[derive(Clone)]
+struct X;
+#[derive(Clone)]
+struct Y;
+
+trait Tr {
+    type Assoc;
+}
+
+impl Tr for X {
+    type Assoc = Y;
+}
+
+#[derive(Clone)]
+struct AssocGeneric<T: Tr>(T::Assoc);
+
+fn f() {
+    let e: AssocGeneric<X> = AssocGeneric(Y);
+    let e_clone = e.clone();
+      //^^^^^^^ AssocGeneric<X>
+}
+    "#,
+    )
+}
+
 #[test]
 fn cfgd_out_assoc_items() {
     check_types(
@@ -3291,6 +3464,19 @@ fn f<T>(t: Ark<T>) {
     );
 }
 
+#[test]
+fn const_dependent_on_local() {
+    check_types(
+        r#"
+fn main() {
+    let s = 5;
+    let t = [2; s];
+      //^ [i32; _]
+}
+"#,
+    );
+}
+
 #[test]
 fn issue_14275() {
     // FIXME: evaluate const generic

crates/hir-ty/src/tests/traits.rs

@@ -90,7 +90,7 @@ fn infer_async_closure() {
 async fn test() {
     let f = async move |x: i32| x + 42;
     f;
-//  ^ |i32| -> impl Future<Output = i32>
+//  ^ impl Fn(i32) -> impl Future<Output = i32>
     let a = f(4);
     a;
 //  ^ impl Future<Output = i32>
@@ -99,7 +99,7 @@ async fn test() {
 //  ^ i32
     let f = async move || 42;
     f;
-//  ^ || -> impl Future<Output = i32>
+//  ^ impl Fn() -> impl Future<Output = i32>
     let a = f();
     a;
 //  ^ impl Future<Output = i32>
@@ -116,7 +116,7 @@ async fn test() {
     };
     let _: Option<u64> = c().await;
     c;
-//  ^ || -> impl Future<Output = Option<u64>>
+//  ^ impl Fn() -> impl Future<Output = Option<u64>>
 }
 "#,
     );
@@ -550,7 +550,7 @@ fn test() -> u64 {
             53..54 'a': S
             57..58 'S': S(fn(u32) -> u64) -> S
             57..74 'S(|i| ...s u64)': S
-            59..73 '|i| 2*i as u64': |u32| -> u64
+            59..73 '|i| 2*i as u64': impl Fn(u32) -> u64
             60..61 'i': u32
             63..64 '2': u64
             63..73 '2*i as u64': u64
@@ -1333,9 +1333,9 @@ fn foo<const C: u8, T>() -> (impl FnOnce(&str, T), impl Trait<u8>) {
 }
 "#,
         expect![[r#"
-            134..165 '{     ...(C)) }': (|&str, T| -> (), Bar<u8>)
-            140..163 '(|inpu...ar(C))': (|&str, T| -> (), Bar<u8>)
-            141..154 '|input, t| {}': |&str, T| -> ()
+            134..165 '{     ...(C)) }': (impl Fn(&str, T), Bar<u8>)
+            140..163 '(|inpu...ar(C))': (impl Fn(&str, T), Bar<u8>)
+            141..154 '|input, t| {}': impl Fn(&str, T)
             142..147 'input': &str
             149..150 't': T
             152..154 '{}': ()
@@ -1506,8 +1506,8 @@ fn main() {
             71..105 '{     ...()); }': ()
             77..78 'f': fn f(&dyn Fn(S))
             77..102 'f(&|nu...foo())': ()
-            79..101 '&|numb....foo()': &|S| -> ()
-            80..101 '|numbe....foo()': |S| -> ()
+            79..101 '&|numb....foo()': &impl Fn(S)
+            80..101 '|numbe....foo()': impl Fn(S)
             81..87 'number': S
             89..95 'number': S
             89..101 'number.foo()': ()
@@ -1912,13 +1912,13 @@ fn test() {
             131..132 'f': F
             151..153 '{}': Lazy<T, F>
             251..497 '{     ...o(); }': ()
-            261..266 'lazy1': Lazy<Foo, || -> Foo>
-            283..292 'Lazy::new': fn new<Foo, || -> Foo>(|| -> Foo) -> Lazy<Foo, || -> Foo>
-            283..300 'Lazy::...| Foo)': Lazy<Foo, || -> Foo>
-            293..299 '|| Foo': || -> Foo
+            261..266 'lazy1': Lazy<Foo, impl Fn() -> Foo>
+            283..292 'Lazy::new': fn new<Foo, impl Fn() -> Foo>(impl Fn() -> Foo) -> Lazy<Foo, impl Fn() -> Foo>
+            283..300 'Lazy::...| Foo)': Lazy<Foo, impl Fn() -> Foo>
+            293..299 '|| Foo': impl Fn() -> Foo
             296..299 'Foo': Foo
             310..312 'r1': usize
-            315..320 'lazy1': Lazy<Foo, || -> Foo>
+            315..320 'lazy1': Lazy<Foo, impl Fn() -> Foo>
             315..326 'lazy1.foo()': usize
             368..383 'make_foo_fn_ptr': fn() -> Foo
             399..410 'make_foo_fn': fn make_foo_fn() -> Foo
@@ -1963,20 +1963,20 @@ fn test() {
             163..167 '1u32': u32
             174..175 'x': Option<u32>
             174..190 'x.map(...v + 1)': Option<u32>
-            180..189 '|v| v + 1': |u32| -> u32
+            180..189 '|v| v + 1': impl Fn(u32) -> u32
             181..182 'v': u32
             184..185 'v': u32
             184..189 'v + 1': u32
             188..189 '1': u32
             196..197 'x': Option<u32>
             196..212 'x.map(... 1u64)': Option<u64>
-            202..211 '|_v| 1u64': |u32| -> u64
+            202..211 '|_v| 1u64': impl Fn(u32) -> u64
             203..205 '_v': u32
             207..211 '1u64': u64
             222..223 'y': Option<i64>
             239..240 'x': Option<u32>
             239..252 'x.map(|_v| 1)': Option<i64>
-            245..251 '|_v| 1': |u32| -> i64
+            245..251 '|_v| 1': impl Fn(u32) -> i64
             246..248 '_v': u32
             250..251 '1': i64
         "#]],
@@ -2005,11 +2005,11 @@ fn test<F: FnOnce(u32) -> u64>(f: F) {
   //^^^^ u64
     let g = |v| v + 1;
               //^^^^^ u64
-          //^^^^^^^^^ |u64| -> u64
+          //^^^^^^^^^ impl Fn(u64) -> u64
     g(1u64);
   //^^^^^^^ u64
     let h = |v| 1u128 + v;
-          //^^^^^^^^^^^^^ |u128| -> u128
+          //^^^^^^^^^^^^^ impl Fn(u128) -> u128
 }"#,
     );
 }
@@ -2062,17 +2062,17 @@ fn test() {
             312..314 '{}': ()
             330..489 '{     ... S); }': ()
             340..342 'x1': u64
-            345..349 'foo1': fn foo1<S, u64, |S| -> u64>(S, |S| -> u64) -> u64
+            345..349 'foo1': fn foo1<S, u64, impl Fn(S) -> u64>(S, impl Fn(S) -> u64) -> u64
             345..368 'foo1(S...hod())': u64
             350..351 'S': S
-            353..367 '|s| s.method()': |S| -> u64
+            353..367 '|s| s.method()': impl Fn(S) -> u64
             354..355 's': S
             357..358 's': S
             357..367 's.method()': u64
             378..380 'x2': u64
-            383..387 'foo2': fn foo2<S, u64, |S| -> u64>(|S| -> u64, S) -> u64
+            383..387 'foo2': fn foo2<S, u64, impl Fn(S) -> u64>(impl Fn(S) -> u64, S) -> u64
             383..406 'foo2(|...(), S)': u64
-            388..402 '|s| s.method()': |S| -> u64
+            388..402 '|s| s.method()': impl Fn(S) -> u64
             389..390 's': S
             392..393 's': S
             392..402 's.method()': u64
@@ -2081,14 +2081,14 @@ fn test() {
             421..422 'S': S
             421..446 'S.foo1...hod())': u64
             428..429 'S': S
-            431..445 '|s| s.method()': |S| -> u64
+            431..445 '|s| s.method()': impl Fn(S) -> u64
             432..433 's': S
             435..436 's': S
             435..445 's.method()': u64
             456..458 'x4': u64
             461..462 'S': S
             461..486 'S.foo2...(), S)': u64
-            468..482 '|s| s.method()': |S| -> u64
+            468..482 '|s| s.method()': impl Fn(S) -> u64
             469..470 's': S
             472..473 's': S
             472..482 's.method()': u64
@@ -2562,9 +2562,9 @@ fn main() {
             72..74 '_v': F
             117..120 '{ }': ()
             132..163 '{     ... }); }': ()
-            138..148 'f::<(), _>': fn f<(), |&()| -> ()>(|&()| -> ())
+            138..148 'f::<(), _>': fn f<(), impl Fn(&())>(impl Fn(&()))
             138..160 'f::<()... z; })': ()
-            149..159 '|z| { z; }': |&()| -> ()
+            149..159 '|z| { z; }': impl Fn(&())
             150..151 'z': &()
             153..159 '{ z; }': ()
             155..156 'z': &()
@@ -2721,9 +2721,9 @@ fn main() {
             983..998 'Vec::<i32>::new': fn new<i32>() -> Vec<i32>
             983..1000 'Vec::<...:new()': Vec<i32>
             983..1012 'Vec::<...iter()': IntoIter<i32>
-            983..1075 'Vec::<...one })': FilterMap<IntoIter<i32>, |i32| -> Option<u32>>
+            983..1075 'Vec::<...one })': FilterMap<IntoIter<i32>, impl Fn(i32) -> Option<u32>>
             983..1101 'Vec::<... y; })': ()
-            1029..1074 '|x| if...None }': |i32| -> Option<u32>
+            1029..1074 '|x| if...None }': impl Fn(i32) -> Option<u32>
             1030..1031 'x': i32
             1033..1074 'if x >...None }': Option<u32>
             1036..1037 'x': i32
@@ -2736,7 +2736,7 @@ fn main() {
             1049..1057 'x as u32': u32
             1066..1074 '{ None }': Option<u32>
             1068..1072 'None': Option<u32>
-            1090..1100 '|y| { y; }': |u32| -> ()
+            1090..1100 '|y| { y; }': impl Fn(u32)
             1091..1092 'y': u32
             1094..1100 '{ y; }': ()
             1096..1097 'y': u32
@@ -2979,13 +2979,13 @@ fn foo() {
             52..126 '{     ...)(s) }': ()
             62..63 's': Option<i32>
             66..78 'Option::None': Option<i32>
-            88..89 'f': |Option<i32>| -> ()
-            92..111 '|x: Op...2>| {}': |Option<i32>| -> ()
+            88..89 'f': impl Fn(Option<i32>)
+            92..111 '|x: Op...2>| {}': impl Fn(Option<i32>)
             93..94 'x': Option<i32>
             109..111 '{}': ()
             117..124 '(&f)(s)': ()
-            118..120 '&f': &|Option<i32>| -> ()
-            119..120 'f': |Option<i32>| -> ()
+            118..120 '&f': &impl Fn(Option<i32>)
+            119..120 'f': impl Fn(Option<i32>)
             122..123 's': Option<i32>
         "#]],
     );
@@ -3072,15 +3072,15 @@ fn foo() {
             228..229 's': Option<i32>
             232..236 'None': Option<i32>
             246..247 'f': Box<dyn FnOnce(&Option<i32>)>
-            281..294 'box (|ps| {})': Box<|&Option<i32>| -> ()>
-            286..293 '|ps| {}': |&Option<i32>| -> ()
+            281..294 'box (|ps| {})': Box<impl Fn(&Option<i32>)>
+            286..293 '|ps| {}': impl Fn(&Option<i32>)
             287..289 'ps': &Option<i32>
             291..293 '{}': ()
             300..301 'f': Box<dyn FnOnce(&Option<i32>)>
             300..305 'f(&s)': ()
             302..304 '&s': &Option<i32>
             303..304 's': Option<i32>
-            281..294: expected Box<dyn FnOnce(&Option<i32>)>, got Box<|&Option<i32>| -> ()>
+            281..294: expected Box<dyn FnOnce(&Option<i32>)>, got Box<impl Fn(&Option<i32>)>
         "#]],
     );
 }
@@ -3811,6 +3811,35 @@ fn f() {
     );
 }
 
+#[test]
+fn regression_14443_trait_solve() {
+    check_no_mismatches(
+        r#"
+trait T {
+    fn f(&self) {}
+}
+
+
+fn main() {
+    struct A;
+    impl T for A {}
+
+    let a = A;
+
+    let b = {
+        struct B;
+        impl T for B {}
+
+        B
+    };
+
+    a.f();
+    b.f();
+}
+"#,
+    )
+}
+
 #[test]
 fn associated_type_sized_bounds() {
     check_infer(
@@ -4286,3 +4315,63 @@ impl Trait for () {
     "#,
     );
 }
+
+#[test]
+fn derive_macro_bounds() {
+    check_types(
+        r#"
+        //- minicore: clone, derive
+        #[derive(Clone)]
+        struct Copy;
+        struct NotCopy;
+        #[derive(Clone)]
+        struct Generic<T>(T);
+        trait Tr {
+            type Assoc;
+        }
+        impl Tr for Copy {
+            type Assoc = NotCopy;
+        }
+        #[derive(Clone)]
+        struct AssocGeneric<T: Tr>(T::Assoc);
+
+        #[derive(Clone)]
+        struct AssocGeneric2<T: Tr>(<T as Tr>::Assoc);
+
+        #[derive(Clone)]
+        struct AssocGeneric3<T: Tr>(Generic<T::Assoc>);
+
+        #[derive(Clone)]
+        struct Vec<T>();
+
+        #[derive(Clone)]
+        struct R1(Vec<R2>);
+        #[derive(Clone)]
+        struct R2(R1);
+
+        fn f() {
+            let x = (&Copy).clone();
+              //^ Copy
+            let x = (&NotCopy).clone();
+              //^ &NotCopy
+            let x = (&Generic(Copy)).clone();
+              //^ Generic<Copy>
+            let x = (&Generic(NotCopy)).clone();
+              //^ &Generic<NotCopy>
+            let x: &AssocGeneric<Copy> = &AssocGeneric(NotCopy);
+            let x = x.clone();
+              //^ &AssocGeneric<Copy>
+            let x: &AssocGeneric2<Copy> = &AssocGeneric2(NotCopy);
+            let x = x.clone();
+              //^ &AssocGeneric2<Copy>
+            let x: &AssocGeneric3<Copy> = &AssocGeneric3(Generic(NotCopy));
+            let x = x.clone();
+              //^ &AssocGeneric3<Copy>
+            let x = (&R1(Vec())).clone();
+              //^ R1
+            let x = (&R2(R1(Vec()))).clone();
+              //^ R2
+        }
+        "#,
+    );
+}

crates/hir-ty/src/traits.rs

@@ -4,7 +4,7 @@ use std::{env::var, sync::Arc};
 
 use chalk_ir::GoalData;
 use chalk_recursive::Cache;
-use chalk_solve::{logging_db::LoggingRustIrDatabase, Solver};
+use chalk_solve::{logging_db::LoggingRustIrDatabase, rust_ir, Solver};
 
 use base_db::CrateId;
 use hir_def::{
@@ -177,8 +177,10 @@ fn is_chalk_print() -> bool {
     std::env::var("CHALK_PRINT").is_ok()
 }
 
-#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
+#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord)]
 pub enum FnTrait {
+    // Warning: Order is important. If something implements `x` it should also implement
+    // `y` if `y <= x`.
     FnOnce,
     FnMut,
     Fn,
@@ -193,6 +195,14 @@ impl FnTrait {
         }
     }
 
+    pub const fn to_chalk_ir(self) -> rust_ir::ClosureKind {
+        match self {
+            FnTrait::FnOnce => rust_ir::ClosureKind::FnOnce,
+            FnTrait::FnMut => rust_ir::ClosureKind::FnMut,
+            FnTrait::Fn => rust_ir::ClosureKind::Fn,
+        }
+    }
+
     pub fn method_name(self) -> Name {
         match self {
             FnTrait::FnOnce => name!(call_once),

crates/hir-ty/src/utils.rs

@@ -4,7 +4,7 @@
 use std::iter;
 
 use base_db::CrateId;
-use chalk_ir::{cast::Cast, fold::Shift, BoundVar, DebruijnIndex};
+use chalk_ir::{cast::Cast, fold::Shift, BoundVar, DebruijnIndex, Mutability};
 use either::Either;
 use hir_def::{
     db::DefDatabase,
@@ -12,6 +12,7 @@ use hir_def::{
         GenericParams, TypeOrConstParamData, TypeParamProvenance, WherePredicate,
         WherePredicateTypeTarget,
     },
+    hir::BindingAnnotation,
     lang_item::LangItem,
     resolver::{HasResolver, TypeNs},
     type_ref::{TraitBoundModifier, TypeRef},
@@ -24,7 +25,8 @@ use rustc_hash::FxHashSet;
 use smallvec::{smallvec, SmallVec};
 
 use crate::{
-    db::HirDatabase, ChalkTraitId, Interner, Substitution, TraitRef, TraitRefExt, WhereClause,
+    db::HirDatabase, ChalkTraitId, Interner, Substitution, TraitRef, TraitRefExt, Ty, TyExt,
+    WhereClause,
 };
 
 pub(crate) fn fn_traits(
@@ -352,3 +354,20 @@ pub fn is_fn_unsafe_to_call(db: &dyn HirDatabase, func: FunctionId) -> bool {
         _ => false,
     }
 }
+
+pub(crate) fn pattern_matching_dereference_count(
+    cond_ty: &mut Ty,
+    binding_mode: &mut BindingAnnotation,
+) -> usize {
+    let mut r = 0;
+    while let Some((ty, _, mu)) = cond_ty.as_reference() {
+        if mu == Mutability::Mut && *binding_mode != BindingAnnotation::Ref {
+            *binding_mode = BindingAnnotation::RefMut;
+        } else {
+            *binding_mode = BindingAnnotation::Ref;
+        }
+        *cond_ty = ty.clone();
+        r += 1;
+    }
+    r
+}

crates/hir/src/diagnostics.rs

@@ -50,7 +50,9 @@ diagnostics![
     PrivateField,
     ReplaceFilterMapNextWithFindMap,
     TypeMismatch,
+    UndeclaredLabel,
     UnimplementedBuiltinMacro,
+    UnreachableLabel,
     UnresolvedExternCrate,
     UnresolvedField,
     UnresolvedImport,
@@ -61,6 +63,13 @@ diagnostics![
     UnusedMut,
 ];
 
+#[derive(Debug)]
+pub struct BreakOutsideOfLoop {
+    pub expr: InFile<AstPtr<ast::Expr>>,
+    pub is_break: bool,
+    pub bad_value_break: bool,
+}
+
 #[derive(Debug)]
 pub struct UnresolvedModule {
     pub decl: InFile<AstPtr<ast::Module>>,
@@ -84,6 +93,17 @@ pub struct UnresolvedMacroCall {
     pub path: ModPath,
     pub is_bang: bool,
 }
+#[derive(Debug, Clone, Eq, PartialEq)]
+pub struct UnreachableLabel {
+    pub node: InFile<AstPtr<ast::Lifetime>>,
+    pub name: Name,
+}
+
+#[derive(Debug, Clone, Eq, PartialEq)]
+pub struct UndeclaredLabel {
+    pub node: InFile<AstPtr<ast::Lifetime>>,
+    pub name: Name,
+}
 
 #[derive(Debug, Clone, Eq, PartialEq)]
 pub struct InactiveCode {
@@ -166,13 +186,6 @@ pub struct PrivateField {
     pub field: Field,
 }
 
-#[derive(Debug)]
-pub struct BreakOutsideOfLoop {
-    pub expr: InFile<AstPtr<ast::Expr>>,
-    pub is_break: bool,
-    pub bad_value_break: bool,
-}
-
 #[derive(Debug)]
 pub struct MissingUnsafe {
     pub expr: InFile<AstPtr<ast::Expr>>,

crates/hir/src/display.rs

@@ -1,6 +1,6 @@
 //! HirDisplay implementations for various hir types.
 use hir_def::{
-    adt::VariantData,
+    data::adt::VariantData,
     generics::{
         TypeOrConstParamData, TypeParamProvenance, WherePredicate, WherePredicateTypeTarget,
     },
@@ -8,6 +8,7 @@ use hir_def::{
     type_ref::{TypeBound, TypeRef},
     AdtId, GenericDefId,
 };
+use hir_expand::name;
 use hir_ty::{
     display::{
         write_bounds_like_dyn_trait_with_prefix, write_visibility, HirDisplay, HirDisplayError,
@@ -76,22 +77,22 @@ impl HirDisplay for Function {
         };
 
         let mut first = true;
-        for (name, type_ref) in &data.params {
+        // FIXME: Use resolved `param.ty` once we no longer discard lifetimes
+        for (type_ref, param) in data.params.iter().zip(self.assoc_fn_params(db)) {
+            let local = param.as_local(db).map(|it| it.name(db));
             if !first {
                 f.write_str(", ")?;
             } else {
                 first = false;
-                if data.has_self_param() {
+                if local == Some(name!(self)) {
                     write_self_param(type_ref, f)?;
                     continue;
                 }
             }
-            match name {
+            match local {
                 Some(name) => write!(f, "{name}: ")?,
                 None => f.write_str("_: ")?,
             }
-            // FIXME: Use resolved `param.ty` or raw `type_ref`?
-            // The former will ignore lifetime arguments currently.
             type_ref.hir_fmt(f)?;
         }
 

crates/hir/src/from_id.rs

@@ -4,7 +4,7 @@
 //! are splitting the hir.
 
 use hir_def::{
-    expr::{BindingId, LabelId},
+    hir::{BindingId, LabelId},
     AdtId, AssocItemId, DefWithBodyId, EnumVariantId, FieldId, GenericDefId, GenericParamId,
     ModuleDefId, VariantId,
 };

crates/hir/src/lib.rs

@@ -39,10 +39,10 @@ use arrayvec::ArrayVec;
 use base_db::{CrateDisplayName, CrateId, CrateOrigin, Edition, FileId, ProcMacroKind};
 use either::Either;
 use hir_def::{
-    adt::VariantData,
     body::{BodyDiagnostic, SyntheticSyntax},
-    expr::{BindingAnnotation, BindingId, ExprOrPatId, LabelId, Pat},
+    data::adt::VariantData,
     generics::{LifetimeParamData, TypeOrConstParamData, TypeParamProvenance},
+    hir::{BindingAnnotation, BindingId, ExprOrPatId, LabelId, Pat},
     item_tree::ItemTreeNode,
     lang_item::{LangItem, LangItemTarget},
     layout::{Layout, LayoutError, ReprOptions},
@@ -88,9 +88,10 @@ pub use crate::{
         AnyDiagnostic, BreakOutsideOfLoop, ExpectedFunction, InactiveCode, IncoherentImpl,
         IncorrectCase, InvalidDeriveTarget, MacroError, MalformedDerive, MismatchedArgCount,
         MissingFields, MissingMatchArms, MissingUnsafe, NeedMut, NoSuchField, PrivateAssocItem,
-        PrivateField, ReplaceFilterMapNextWithFindMap, TypeMismatch, UnimplementedBuiltinMacro,
-        UnresolvedExternCrate, UnresolvedField, UnresolvedImport, UnresolvedMacroCall,
-        UnresolvedMethodCall, UnresolvedModule, UnresolvedProcMacro, UnusedMut,
+        PrivateField, ReplaceFilterMapNextWithFindMap, TypeMismatch, UndeclaredLabel,
+        UnimplementedBuiltinMacro, UnreachableLabel, UnresolvedExternCrate, UnresolvedField,
+        UnresolvedImport, UnresolvedMacroCall, UnresolvedMethodCall, UnresolvedModule,
+        UnresolvedProcMacro, UnusedMut,
     },
     has_source::HasSource,
     semantics::{PathResolution, Semantics, SemanticsScope, TypeInfo, VisibleTraits},
@@ -108,9 +109,8 @@ pub use crate::{
 pub use {
     cfg::{CfgAtom, CfgExpr, CfgOptions},
     hir_def::{
-        adt::StructKind,
-        attr::{Attrs, AttrsWithOwner, Documentation},
-        builtin_attr::AttributeTemplate,
+        attr::{builtin::AttributeTemplate, Attrs, AttrsWithOwner, Documentation},
+        data::adt::StructKind,
         find_path::PrefixKind,
         import_map,
         nameres::ModuleSource,
@@ -129,7 +129,7 @@ pub use {
         ExpandResult, HirFileId, InFile, MacroFile, Origin,
     },
     hir_ty::{
-        display::{HirDisplay, HirDisplayError, HirWrite},
+        display::{ClosureStyle, HirDisplay, HirDisplayError, HirWrite},
         mir::MirEvalError,
         PointerCast, Safety,
     },
@@ -1393,6 +1393,12 @@ impl DefWithBody {
                     }
                     .into(),
                 ),
+                BodyDiagnostic::UnreachableLabel { node, name } => {
+                    acc.push(UnreachableLabel { node: node.clone(), name: name.clone() }.into())
+                }
+                BodyDiagnostic::UndeclaredLabel { node, name } => {
+                    acc.push(UndeclaredLabel { node: node.clone(), name: name.clone() }.into())
+                }
             }
         }
 
@@ -1405,14 +1411,6 @@ impl DefWithBody {
                     let field = source_map.field_syntax(expr);
                     acc.push(NoSuchField { field }.into())
                 }
-                &hir_ty::InferenceDiagnostic::BreakOutsideOfLoop {
-                    expr,
-                    is_break,
-                    bad_value_break,
-                } => {
-                    let expr = expr_syntax(expr);
-                    acc.push(BreakOutsideOfLoop { expr, is_break, bad_value_break }.into())
-                }
                 &hir_ty::InferenceDiagnostic::MismatchedArgCount { call_expr, expected, found } => {
                     acc.push(
                         MismatchedArgCount { call_expr: expr_syntax(call_expr), expected, found }
@@ -1484,6 +1482,14 @@ impl DefWithBody {
                         .into(),
                     )
                 }
+                &hir_ty::InferenceDiagnostic::BreakOutsideOfLoop {
+                    expr,
+                    is_break,
+                    bad_value_break,
+                } => {
+                    let expr = expr_syntax(expr);
+                    acc.push(BreakOutsideOfLoop { expr, is_break, bad_value_break }.into())
+                }
             }
         }
         for (pat_or_expr, mismatch) in infer.type_mismatches() {
@@ -1524,35 +1530,44 @@ impl DefWithBody {
 
         let hir_body = db.body(self.into());
 
-        if let Ok(borrowck_result) = db.borrowck(self.into()) {
-            let mir_body = &borrowck_result.mir_body;
-            let mol = &borrowck_result.mutability_of_locals;
-            for (binding_id, _) in hir_body.bindings.iter() {
-                let need_mut = &mol[mir_body.binding_locals[binding_id]];
-                let local = Local { parent: self.into(), binding_id };
-                match (need_mut, local.is_mut(db)) {
-                    (mir::MutabilityReason::Mut { .. }, true)
-                    | (mir::MutabilityReason::Not, false) => (),
-                    (mir::MutabilityReason::Mut { spans }, false) => {
-                        for span in spans {
-                            let span: InFile<SyntaxNodePtr> = match span {
-                                mir::MirSpan::ExprId(e) => match source_map.expr_syntax(*e) {
-                                    Ok(s) => s.map(|x| x.into()),
-                                    Err(_) => continue,
-                                },
-                                mir::MirSpan::PatId(p) => match source_map.pat_syntax(*p) {
-                                    Ok(s) => s.map(|x| match x {
-                                        Either::Left(e) => e.into(),
-                                        Either::Right(e) => e.into(),
-                                    }),
-                                    Err(_) => continue,
-                                },
-                                mir::MirSpan::Unknown => continue,
-                            };
-                            acc.push(NeedMut { local, span }.into());
+        if let Ok(borrowck_results) = db.borrowck(self.into()) {
+            for borrowck_result in borrowck_results.iter() {
+                let mir_body = &borrowck_result.mir_body;
+                let mol = &borrowck_result.mutability_of_locals;
+                for (binding_id, _) in hir_body.bindings.iter() {
+                    let Some(&local) = mir_body.binding_locals.get(binding_id) else {
+                        continue;
+                    };
+                    let need_mut = &mol[local];
+                    let local = Local { parent: self.into(), binding_id };
+                    match (need_mut, local.is_mut(db)) {
+                        (mir::MutabilityReason::Mut { .. }, true)
+                        | (mir::MutabilityReason::Not, false) => (),
+                        (mir::MutabilityReason::Mut { spans }, false) => {
+                            for span in spans {
+                                let span: InFile<SyntaxNodePtr> = match span {
+                                    mir::MirSpan::ExprId(e) => match source_map.expr_syntax(*e) {
+                                        Ok(s) => s.map(|x| x.into()),
+                                        Err(_) => continue,
+                                    },
+                                    mir::MirSpan::PatId(p) => match source_map.pat_syntax(*p) {
+                                        Ok(s) => s.map(|x| match x {
+                                            Either::Left(e) => e.into(),
+                                            Either::Right(e) => e.into(),
+                                        }),
+                                        Err(_) => continue,
+                                    },
+                                    mir::MirSpan::Unknown => continue,
+                                };
+                                acc.push(NeedMut { local, span }.into());
+                            }
+                        }
+                        (mir::MutabilityReason::Not, true) => {
+                            if !infer.mutated_bindings_in_closure.contains(&binding_id) {
+                                acc.push(UnusedMut { local }.into())
+                            }
                         }
                     }
-                    (mir::MutabilityReason::Not, true) => acc.push(UnusedMut { local }.into()),
                 }
             }
         }
@@ -1838,7 +1853,7 @@ impl Param {
     }
 
     pub fn name(&self, db: &dyn HirDatabase) -> Option<Name> {
-        db.function_data(self.func.id).params[self.idx].0.clone()
+        Some(self.as_local(db)?.name(db))
     }
 
     pub fn as_local(&self, db: &dyn HirDatabase) -> Option<Local> {
@@ -1879,7 +1894,7 @@ impl SelfParam {
         func_data
             .params
             .first()
-            .map(|(_, param)| match &**param {
+            .map(|param| match &**param {
                 TypeRef::Reference(.., mutability) => match mutability {
                     hir_def::type_ref::Mutability::Shared => Access::Shared,
                     hir_def::type_ref::Mutability::Mut => Access::Exclusive,
@@ -2690,9 +2705,7 @@ impl BuiltinAttr {
     }
 
     fn builtin(name: &str) -> Option<Self> {
-        hir_def::builtin_attr::INERT_ATTRIBUTES
-            .iter()
-            .position(|tool| tool.name == name)
+        hir_def::attr::builtin::find_builtin_attr_idx(name)
             .map(|idx| BuiltinAttr { krate: None, idx: idx as u32 })
     }
 
@@ -2700,14 +2713,14 @@ impl BuiltinAttr {
         // FIXME: Return a `Name` here
         match self.krate {
             Some(krate) => db.crate_def_map(krate).registered_attrs()[self.idx as usize].clone(),
-            None => SmolStr::new(hir_def::builtin_attr::INERT_ATTRIBUTES[self.idx as usize].name),
+            None => SmolStr::new(hir_def::attr::builtin::INERT_ATTRIBUTES[self.idx as usize].name),
         }
     }
 
     pub fn template(&self, _: &dyn HirDatabase) -> Option<AttributeTemplate> {
         match self.krate {
             Some(_) => None,
-            None => Some(hir_def::builtin_attr::INERT_ATTRIBUTES[self.idx as usize].template),
+            None => Some(hir_def::attr::builtin::INERT_ATTRIBUTES[self.idx as usize].template),
         }
     }
 }
@@ -2730,7 +2743,7 @@ impl ToolModule {
     }
 
     fn builtin(name: &str) -> Option<Self> {
-        hir_def::builtin_attr::TOOL_MODULES
+        hir_def::attr::builtin::TOOL_MODULES
             .iter()
             .position(|&tool| tool == name)
             .map(|idx| ToolModule { krate: None, idx: idx as u32 })
@@ -2740,7 +2753,7 @@ impl ToolModule {
         // FIXME: Return a `Name` here
         match self.krate {
             Some(krate) => db.crate_def_map(krate).registered_tools()[self.idx as usize].clone(),
-            None => SmolStr::new(hir_def::builtin_attr::TOOL_MODULES[self.idx as usize]),
+            None => SmolStr::new(hir_def::attr::builtin::TOOL_MODULES[self.idx as usize]),
         }
     }
 }
@@ -3379,7 +3392,12 @@ impl Type {
     }
 
     pub fn as_callable(&self, db: &dyn HirDatabase) -> Option<Callable> {
+        let mut the_ty = &self.ty;
         let callee = match self.ty.kind(Interner) {
+            TyKind::Ref(_, _, ty) if ty.as_closure().is_some() => {
+                the_ty = ty;
+                Callee::Closure(ty.as_closure().unwrap())
+            }
             TyKind::Closure(id, _) => Callee::Closure(*id),
             TyKind::Function(_) => Callee::FnPtr,
             TyKind::FnDef(..) => Callee::Def(self.ty.callable_def(db)?),
@@ -3394,7 +3412,7 @@ impl Type {
             }
         };
 
-        let sig = self.ty.callable_sig(db)?;
+        let sig = the_ty.callable_sig(db)?;
         Some(Callable { ty: self.clone(), sig, callee, is_bound_method: false })
     }
 

crates/hir/src/semantics.rs

@@ -8,7 +8,7 @@ use base_db::{FileId, FileRange};
 use either::Either;
 use hir_def::{
     body,
-    expr::Expr,
+    hir::Expr,
     macro_id_to_def_id,
     resolver::{self, HasResolver, Resolver, TypeNs},
     type_ref::Mutability,
@@ -1065,7 +1065,7 @@ impl<'db> SemanticsImpl<'db> {
 
     fn resolve_type(&self, ty: &ast::Type) -> Option<Type> {
         let analyze = self.analyze(ty.syntax())?;
-        let ctx = body::LowerCtx::new(self.db.upcast(), analyze.file_id);
+        let ctx = body::LowerCtx::with_file_id(self.db.upcast(), analyze.file_id);
         let ty = hir_ty::TyLoweringContext::new(self.db, &analyze.resolver)
             .lower_ty(&crate::TypeRef::from_ast(&ctx, ty.clone()));
         Some(Type::new_with_resolver(self.db, &analyze.resolver, ty))
@@ -1672,7 +1672,7 @@ impl<'a> SemanticsScope<'a> {
     /// Resolve a path as-if it was written at the given scope. This is
     /// necessary a heuristic, as it doesn't take hygiene into account.
     pub fn speculative_resolve(&self, path: &ast::Path) -> Option<PathResolution> {
-        let ctx = body::LowerCtx::new(self.db.upcast(), self.file_id);
+        let ctx = body::LowerCtx::with_file_id(self.db.upcast(), self.file_id);
         let path = Path::from_src(path.clone(), &ctx)?;
         resolve_hir_path(self.db, &self.resolver, &path)
     }

crates/hir/src/semantics/source_to_def.rs

@@ -14,7 +14,7 @@
 //! expression, an item definition.
 //!
 //! Knowing only the syntax gives us relatively little info. For example,
-//! looking at the syntax of the function we can realise that it is a part of an
+//! looking at the syntax of the function we can realize that it is a part of an
 //! `impl` block, but we won't be able to tell what trait function the current
 //! function overrides, and whether it does that correctly. For that, we need to
 //! go from [`ast::Fn`] to [`crate::Function`], and that's exactly what this
@@ -88,9 +88,11 @@
 use base_db::FileId;
 use hir_def::{
     child_by_source::ChildBySource,
-    dyn_map::DynMap,
-    expr::{BindingId, LabelId},
-    keys::{self, Key},
+    dyn_map::{
+        keys::{self, Key},
+        DynMap,
+    },
+    hir::{BindingId, LabelId},
     AdtId, ConstId, ConstParamId, DefWithBodyId, EnumId, EnumVariantId, FieldId, FunctionId,
     GenericDefId, GenericParamId, ImplId, LifetimeParamId, MacroId, ModuleId, StaticId, StructId,
     TraitAliasId, TraitId, TypeAliasId, TypeParamId, UnionId, VariantId,

crates/hir/src/source_analyzer.rs

@@ -17,7 +17,7 @@ use hir_def::{
         scope::{ExprScopes, ScopeId},
         Body, BodySourceMap,
     },
-    expr::{ExprId, Pat, PatId},
+    hir::{ExprId, Pat, PatId},
     lang_item::LangItem,
     macro_id_to_def_id,
     path::{ModPath, Path, PathKind},
@@ -463,7 +463,7 @@ impl SourceAnalyzer {
         db: &dyn HirDatabase,
         macro_call: InFile<&ast::MacroCall>,
     ) -> Option<Macro> {
-        let ctx = body::LowerCtx::new(db.upcast(), macro_call.file_id);
+        let ctx = body::LowerCtx::with_file_id(db.upcast(), macro_call.file_id);
         let path = macro_call.value.path().and_then(|ast| Path::from_src(ast, &ctx))?;
         self.resolver.resolve_path_as_macro(db.upcast(), path.mod_path()?).map(|it| it.into())
     }

crates/ide-assists/src/handlers/convert_nested_function_to_closure.rs

@@ -0,0 +1,209 @@
+use ide_db::assists::{AssistId, AssistKind};
+use syntax::ast::{self, HasGenericParams, HasName};
+use syntax::{AstNode, SyntaxKind};
+
+use crate::assist_context::{AssistContext, Assists};
+
+// Assist: convert_nested_function_to_closure
+//
+// Converts a function that is defined within the body of another function into a closure.
+//
+// ```
+// fn main() {
+//     fn fo$0o(label: &str, number: u64) {
+//         println!("{}: {}", label, number);
+//     }
+//
+//     foo("Bar", 100);
+// }
+// ```
+// ->
+// ```
+// fn main() {
+//     let foo = |label: &str, number: u64| {
+//         println!("{}: {}", label, number);
+//     };
+//
+//     foo("Bar", 100);
+// }
+// ```
+pub(crate) fn convert_nested_function_to_closure(
+    acc: &mut Assists,
+    ctx: &AssistContext<'_>,
+) -> Option<()> {
+    let name = ctx.find_node_at_offset::<ast::Name>()?;
+    let function = name.syntax().parent().and_then(ast::Fn::cast)?;
+
+    if !is_nested_function(&function) || is_generic(&function) || has_modifiers(&function) {
+        return None;
+    }
+
+    let target = function.syntax().text_range();
+    let body = function.body()?;
+    let name = function.name()?;
+    let param_list = function.param_list()?;
+
+    acc.add(
+        AssistId("convert_nested_function_to_closure", AssistKind::RefactorRewrite),
+        "Convert nested function to closure",
+        target,
+        |edit| {
+            let params = &param_list.syntax().text().to_string();
+            let params = params.strip_prefix("(").unwrap_or(params);
+            let params = params.strip_suffix(")").unwrap_or(params);
+
+            let mut body = body.to_string();
+            if !has_semicolon(&function) {
+                body.push(';');
+            }
+            edit.replace(target, format!("let {name} = |{params}| {body}"));
+        },
+    )
+}
+
+/// Returns whether the given function is nested within the body of another function.
+fn is_nested_function(function: &ast::Fn) -> bool {
+    function.syntax().ancestors().skip(1).find_map(ast::Item::cast).map_or(false, |it| {
+        matches!(it, ast::Item::Fn(_) | ast::Item::Static(_) | ast::Item::Const(_))
+    })
+}
+
+/// Returns whether the given nested function has generic parameters.
+fn is_generic(function: &ast::Fn) -> bool {
+    function.generic_param_list().is_some()
+}
+
+/// Returns whether the given nested function has any modifiers:
+///
+/// - `async`,
+/// - `const` or
+/// - `unsafe`
+fn has_modifiers(function: &ast::Fn) -> bool {
+    function.async_token().is_some()
+        || function.const_token().is_some()
+        || function.unsafe_token().is_some()
+}
+
+/// Returns whether the given nested function has a trailing semicolon.
+fn has_semicolon(function: &ast::Fn) -> bool {
+    function
+        .syntax()
+        .next_sibling_or_token()
+        .map(|t| t.kind() == SyntaxKind::SEMICOLON)
+        .unwrap_or(false)
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::tests::{check_assist, check_assist_not_applicable};
+
+    use super::convert_nested_function_to_closure;
+
+    #[test]
+    fn convert_nested_function_to_closure_works() {
+        check_assist(
+            convert_nested_function_to_closure,
+            r#"
+fn main() {
+    fn $0foo(a: u64, b: u64) -> u64 {
+        2 * (a + b)
+    }
+
+    _ = foo(3, 4);
+}
+            "#,
+            r#"
+fn main() {
+    let foo = |a: u64, b: u64| {
+        2 * (a + b)
+    };
+
+    _ = foo(3, 4);
+}
+            "#,
+        );
+    }
+
+    #[test]
+    fn convert_nested_function_to_closure_works_with_existing_semicolon() {
+        check_assist(
+            convert_nested_function_to_closure,
+            r#"
+fn main() {
+    fn foo$0(a: u64, b: u64) -> u64 {
+        2 * (a + b)
+    };
+
+    _ = foo(3, 4);
+}
+            "#,
+            r#"
+fn main() {
+    let foo = |a: u64, b: u64| {
+        2 * (a + b)
+    };
+
+    _ = foo(3, 4);
+}
+            "#,
+        );
+    }
+
+    #[test]
+    fn convert_nested_function_to_closure_is_not_suggested_on_top_level_function() {
+        check_assist_not_applicable(
+            convert_nested_function_to_closure,
+            r#"
+fn ma$0in() {}
+            "#,
+        );
+    }
+
+    #[test]
+    fn convert_nested_function_to_closure_is_not_suggested_when_cursor_off_name() {
+        check_assist_not_applicable(
+            convert_nested_function_to_closure,
+            r#"
+fn main() {
+    fn foo(a: u64, $0b: u64) -> u64 {
+        2 * (a + b)
+    }
+
+    _ = foo(3, 4);
+}
+            "#,
+        );
+    }
+
+    #[test]
+    fn convert_nested_function_to_closure_is_not_suggested_if_function_has_generic_params() {
+        check_assist_not_applicable(
+            convert_nested_function_to_closure,
+            r#"
+fn main() {
+    fn fo$0o<S: Into<String>>(s: S) -> String {
+        s.into()
+    }
+
+    _ = foo("hello");
+}
+            "#,
+        );
+    }
+
+    #[test]
+    fn convert_nested_function_to_closure_is_not_suggested_if_function_has_modifier() {
+        check_assist_not_applicable(
+            convert_nested_function_to_closure,
+            r#"
+fn main() {
+    const fn fo$0o(s: String) -> String {
+        s
+    }
+
+    _ = foo("hello");
+}
+            "#,
+        );
+    }
+}

crates/ide-assists/src/handlers/extract_function.rs

@@ -70,6 +70,11 @@ pub(crate) fn extract_function(acc: &mut Assists, ctx: &AssistContext<'_>) -> Op
     }
 
     let node = ctx.covering_element();
+    if matches!(node.kind(), T!['{'] | T!['}'] | T!['('] | T![')'] | T!['['] | T![']']) {
+        cov_mark::hit!(extract_function_in_braces_is_not_applicable);
+        return None;
+    }
+
     if node.kind() == COMMENT {
         cov_mark::hit!(extract_function_in_comment_is_not_applicable);
         return None;
@@ -5800,4 +5805,40 @@ fn $0fun_name() -> ControlFlow<()> {
 "#,
         );
     }
+
+    #[test]
+    fn in_left_curly_is_not_applicable() {
+        cov_mark::check!(extract_function_in_braces_is_not_applicable);
+        check_assist_not_applicable(extract_function, r"fn foo() { $0}$0");
+    }
+
+    #[test]
+    fn in_right_curly_is_not_applicable() {
+        cov_mark::check!(extract_function_in_braces_is_not_applicable);
+        check_assist_not_applicable(extract_function, r"fn foo() $0{$0 }");
+    }
+
+    #[test]
+    fn in_left_paren_is_not_applicable() {
+        cov_mark::check!(extract_function_in_braces_is_not_applicable);
+        check_assist_not_applicable(extract_function, r"fn foo( $0)$0 { }");
+    }
+
+    #[test]
+    fn in_right_paren_is_not_applicable() {
+        cov_mark::check!(extract_function_in_braces_is_not_applicable);
+        check_assist_not_applicable(extract_function, r"fn foo $0($0 ) { }");
+    }
+
+    #[test]
+    fn in_left_brack_is_not_applicable() {
+        cov_mark::check!(extract_function_in_braces_is_not_applicable);
+        check_assist_not_applicable(extract_function, r"fn foo(arr: &mut [i32$0]$0) {}");
+    }
+
+    #[test]
+    fn in_right_brack_is_not_applicable() {
+        cov_mark::check!(extract_function_in_braces_is_not_applicable);
+        check_assist_not_applicable(extract_function, r"fn foo(arr: &mut $0[$0i32]) {}");
+    }
 }

crates/ide-assists/src/handlers/extract_variable.rs

@@ -1,3 +1,4 @@
+use hir::TypeInfo;
 use stdx::format_to;
 use syntax::{
     ast::{self, AstNode},
@@ -46,21 +47,24 @@ pub(crate) fn extract_variable(acc: &mut Assists, ctx: &AssistContext<'_>) -> Op
         .take_while(|it| ctx.selection_trimmed().contains_range(it.text_range()))
         .find_map(valid_target_expr)?;
 
-    if let Some(ty_info) = ctx.sema.type_of_expr(&to_extract) {
-        if ty_info.adjusted().is_unit() {
-            return None;
-        }
+    let ty = ctx.sema.type_of_expr(&to_extract).map(TypeInfo::adjusted);
+    if matches!(&ty, Some(ty_info) if ty_info.is_unit()) {
+        return None;
     }
 
-    let reference_modifier = match get_receiver_type(ctx, &to_extract) {
+    let parent = to_extract.syntax().parent().and_then(ast::Expr::cast);
+    let needs_adjust = parent
+        .as_ref()
+        .map_or(false, |it| matches!(it, ast::Expr::FieldExpr(_) | ast::Expr::MethodCallExpr(_)));
+
+    let reference_modifier = match ty.filter(|_| needs_adjust) {
         Some(receiver_type) if receiver_type.is_mutable_reference() => "&mut ",
         Some(receiver_type) if receiver_type.is_reference() => "&",
         _ => "",
     };
 
-    let parent_ref_expr = to_extract.syntax().parent().and_then(ast::RefExpr::cast);
-    let var_modifier = match parent_ref_expr {
-        Some(expr) if expr.mut_token().is_some() => "mut ",
+    let var_modifier = match parent {
+        Some(ast::Expr::RefExpr(expr)) if expr.mut_token().is_some() => "mut ",
         _ => "",
     };
 
@@ -164,22 +168,6 @@ fn valid_target_expr(node: SyntaxNode) -> Option<ast::Expr> {
     }
 }
 
-fn get_receiver_type(ctx: &AssistContext<'_>, expression: &ast::Expr) -> Option<hir::Type> {
-    let receiver = get_receiver(expression.clone())?;
-    Some(ctx.sema.type_of_expr(&receiver)?.original())
-}
-
-/// In the expression `a.b.c.x()`, find `a`
-fn get_receiver(expression: ast::Expr) -> Option<ast::Expr> {
-    match expression {
-        ast::Expr::FieldExpr(field) if field.expr().is_some() => {
-            let nested_expression = &field.expr()?;
-            get_receiver(nested_expression.to_owned())
-        }
-        _ => Some(expression),
-    }
-}
-
 #[derive(Debug)]
 enum Anchor {
     Before(SyntaxNode),
@@ -944,6 +932,11 @@ struct S {
     vec: Vec<u8>
 }
 
+struct Vec<T>;
+impl<T> Vec<T> {
+    fn push(&mut self, _:usize) {}
+}
+
 fn foo(s: &mut S) {
     $0s.vec$0.push(0);
 }"#,
@@ -952,6 +945,11 @@ struct S {
     vec: Vec<u8>
 }
 
+struct Vec<T>;
+impl<T> Vec<T> {
+    fn push(&mut self, _:usize) {}
+}
+
 fn foo(s: &mut S) {
     let $0vec = &mut s.vec;
     vec.push(0);
@@ -973,6 +971,10 @@ struct X {
 struct S {
     vec: Vec<u8>
 }
+struct Vec<T>;
+impl<T> Vec<T> {
+    fn push(&mut self, _:usize) {}
+}
 
 fn foo(f: &mut Y) {
     $0f.field.field.vec$0.push(0);
@@ -987,6 +989,10 @@ struct X {
 struct S {
     vec: Vec<u8>
 }
+struct Vec<T>;
+impl<T> Vec<T> {
+    fn push(&mut self, _:usize) {}
+}
 
 fn foo(f: &mut Y) {
     let $0vec = &mut f.field.field.vec;
@@ -1123,7 +1129,7 @@ struct S {
 }
 
 fn foo(s: S) {
-    let $0x = s.sub;
+    let $0x = &s.sub;
     x.do_thing();
 }"#,
         );
@@ -1189,7 +1195,7 @@ impl X {
 
 fn foo() {
     let local = &mut S::new();
-    let $0x = &mut local.sub;
+    let $0x = &local.sub;
     x.do_thing();
 }"#,
         );

crates/ide-assists/src/handlers/generate_function.rs

@@ -1910,7 +1910,6 @@ fn bar(new: fn) ${0:-> _} {
 
     #[test]
     fn add_function_with_closure_arg() {
-        // FIXME: The argument in `bar` is wrong.
         check_assist(
             generate_function,
             r"
@@ -1925,7 +1924,7 @@ fn foo() {
     bar(closure)
 }
 
-fn bar(closure: _) {
+fn bar(closure: impl Fn(i64) -> i64) {
     ${0:todo!()}
 }
 ",

crates/ide-assists/src/handlers/reorder_impl_items.rs

@@ -21,7 +21,7 @@ use crate::{AssistContext, AssistId, AssistKind, Assists};
 // }
 //
 // struct Bar;
-// $0impl Foo for Bar {
+// $0impl Foo for Bar$0 {
 //     const B: u8 = 17;
 //     fn c() {}
 //     type A = String;
@@ -45,6 +45,16 @@ use crate::{AssistContext, AssistId, AssistKind, Assists};
 pub(crate) fn reorder_impl_items(acc: &mut Assists, ctx: &AssistContext<'_>) -> Option<()> {
     let impl_ast = ctx.find_node_at_offset::<ast::Impl>()?;
     let items = impl_ast.assoc_item_list()?;
+
+    // restrict the range
+    // if cursor is in assoc_items, abort
+    let assoc_range = items.syntax().text_range();
+    let cursor_position = ctx.offset();
+    if assoc_range.contains_inclusive(cursor_position) {
+        cov_mark::hit!(not_applicable_editing_assoc_items);
+        return None;
+    }
+
     let assoc_items = items.assoc_items().collect::<Vec<_>>();
 
     let path = impl_ast
@@ -264,9 +274,9 @@ trait Bar {
 }
 
 struct Foo;
-impl Bar for Foo {
+$0impl Bar for Foo {
     type Fooo = ();
-    type Foo = ();$0
+    type Foo = ();
 }"#,
             r#"
 trait Bar {
@@ -281,4 +291,29 @@ impl Bar for Foo {
 }"#,
         )
     }
+
+    #[test]
+    fn not_applicable_editing_assoc_items() {
+        cov_mark::check!(not_applicable_editing_assoc_items);
+        check_assist_not_applicable(
+            reorder_impl_items,
+            r#"
+trait Bar {
+    type T;
+    const C: ();
+    fn a() {}
+    fn z() {}
+    fn b() {}
+}
+struct Foo;
+impl Bar for Foo {
+    type T = ();$0
+    const C: () = ();
+    fn z() {}
+    fn a() {}
+    fn b() {}
+}
+        "#,
+        )
+    }
 }

crates/ide-assists/src/handlers/sort_items.rs

@@ -116,9 +116,11 @@ trait AddRewrite {
         new: Vec<T>,
         target: TextRange,
     ) -> Option<()>;
+    fn yeet() {}
 }
 
 impl AddRewrite for Assists {
+    fn yeet() {}
     fn add_rewrite<T: AstNode>(
         &mut self,
         label: &str,

crates/ide-assists/src/lib.rs

@@ -122,6 +122,7 @@ mod handlers {
     mod convert_iter_for_each_to_for;
     mod convert_let_else_to_match;
     mod convert_match_to_let_else;
+    mod convert_nested_function_to_closure;
     mod convert_tuple_struct_to_named_struct;
     mod convert_named_struct_to_tuple_struct;
     mod convert_to_guarded_return;
@@ -228,8 +229,9 @@ mod handlers {
             convert_iter_for_each_to_for::convert_iter_for_each_to_for,
             convert_iter_for_each_to_for::convert_for_loop_with_for_each,
             convert_let_else_to_match::convert_let_else_to_match,
-            convert_named_struct_to_tuple_struct::convert_named_struct_to_tuple_struct,
             convert_match_to_let_else::convert_match_to_let_else,
+            convert_named_struct_to_tuple_struct::convert_named_struct_to_tuple_struct,
+            convert_nested_function_to_closure::convert_nested_function_to_closure,
             convert_to_guarded_return::convert_to_guarded_return,
             convert_tuple_struct_to_named_struct::convert_tuple_struct_to_named_struct,
             convert_two_arm_bool_match_to_matches_macro::convert_two_arm_bool_match_to_matches_macro,

crates/ide-assists/src/tests/generated.rs

@@ -494,6 +494,31 @@ impl Point {
     )
 }
 
+#[test]
+fn doctest_convert_nested_function_to_closure() {
+    check_doc_test(
+        "convert_nested_function_to_closure",
+        r#####"
+fn main() {
+    fn fo$0o(label: &str, number: u64) {
+        println!("{}: {}", label, number);
+    }
+
+    foo("Bar", 100);
+}
+"#####,
+        r#####"
+fn main() {
+    let foo = |label: &str, number: u64| {
+        println!("{}: {}", label, number);
+    };
+
+    foo("Bar", 100);
+}
+"#####,
+    )
+}
+
 #[test]
 fn doctest_convert_to_guarded_return() {
     check_doc_test(
@@ -2116,7 +2141,7 @@ trait Foo {
 }
 
 struct Bar;
-$0impl Foo for Bar {
+$0impl Foo for Bar$0 {
     const B: u8 = 17;
     fn c() {}
     type A = String;

crates/ide-assists/src/tests/sourcegen.rs

@@ -90,8 +90,6 @@ impl Assist {
             let comment_blocks = sourcegen::CommentBlock::extract("Assist", &text);
 
             for block in comment_blocks {
-                // FIXME: doesn't support blank lines yet, need to tweak
-                // `extract_comment_blocks` for that.
                 let id = block.id;
                 assert!(
                     id.chars().all(|it| it.is_ascii_lowercase() || it == '_'),

crates/ide-completion/src/completions.rs

@@ -23,7 +23,7 @@ pub(crate) mod env_vars;
 
 use std::iter;
 
-use hir::{known, ScopeDef, Variant};
+use hir::{known, HasAttrs, ScopeDef, Variant};
 use ide_db::{imports::import_assets::LocatedImport, SymbolKind};
 use syntax::ast;
 
@@ -173,6 +173,9 @@ impl Completions {
         resolution: hir::ScopeDef,
         doc_aliases: Vec<syntax::SmolStr>,
     ) {
+        if !ctx.check_stability(resolution.attrs(ctx.db).as_deref()) {
+            return;
+        }
         let is_private_editable = match ctx.def_is_visible(&resolution) {
             Visible::Yes => false,
             Visible::Editable => true,
@@ -198,6 +201,9 @@ impl Completions {
         local_name: hir::Name,
         resolution: hir::ScopeDef,
     ) {
+        if !ctx.check_stability(resolution.attrs(ctx.db).as_deref()) {
+            return;
+        }
         let is_private_editable = match ctx.def_is_visible(&resolution) {
             Visible::Yes => false,
             Visible::Editable => true,
@@ -220,6 +226,9 @@ impl Completions {
         path_ctx: &PathCompletionCtx,
         e: hir::Enum,
     ) {
+        if !ctx.check_stability(Some(&e.attrs(ctx.db))) {
+            return;
+        }
         e.variants(ctx.db)
             .into_iter()
             .for_each(|variant| self.add_enum_variant(ctx, path_ctx, variant, None));
@@ -233,6 +242,9 @@ impl Completions {
         local_name: hir::Name,
         doc_aliases: Vec<syntax::SmolStr>,
     ) {
+        if !ctx.check_stability(Some(&module.attrs(ctx.db))) {
+            return;
+        }
         self.add_path_resolution(
             ctx,
             path_ctx,
@@ -249,6 +261,9 @@ impl Completions {
         mac: hir::Macro,
         local_name: hir::Name,
     ) {
+        if !ctx.check_stability(Some(&mac.attrs(ctx.db))) {
+            return;
+        }
         let is_private_editable = match ctx.is_visible(&mac) {
             Visible::Yes => false,
             Visible::Editable => true,
@@ -272,6 +287,9 @@ impl Completions {
         func: hir::Function,
         local_name: Option<hir::Name>,
     ) {
+        if !ctx.check_stability(Some(&func.attrs(ctx.db))) {
+            return;
+        }
         let is_private_editable = match ctx.is_visible(&func) {
             Visible::Yes => false,
             Visible::Editable => true,
@@ -296,6 +314,9 @@ impl Completions {
         receiver: Option<hir::Name>,
         local_name: Option<hir::Name>,
     ) {
+        if !ctx.check_stability(Some(&func.attrs(ctx.db))) {
+            return;
+        }
         let is_private_editable = match ctx.is_visible(&func) {
             Visible::Yes => false,
             Visible::Editable => true,
@@ -320,6 +341,9 @@ impl Completions {
         func: hir::Function,
         import: LocatedImport,
     ) {
+        if !ctx.check_stability(Some(&func.attrs(ctx.db))) {
+            return;
+        }
         let is_private_editable = match ctx.is_visible(&func) {
             Visible::Yes => false,
             Visible::Editable => true,
@@ -340,6 +364,9 @@ impl Completions {
     }
 
     pub(crate) fn add_const(&mut self, ctx: &CompletionContext<'_>, konst: hir::Const) {
+        if !ctx.check_stability(Some(&konst.attrs(ctx.db))) {
+            return;
+        }
         let is_private_editable = match ctx.is_visible(&konst) {
             Visible::Yes => false,
             Visible::Editable => true,
@@ -356,6 +383,9 @@ impl Completions {
         ctx: &CompletionContext<'_>,
         type_alias: hir::TypeAlias,
     ) {
+        if !ctx.check_stability(Some(&type_alias.attrs(ctx.db))) {
+            return;
+        }
         let is_private_editable = match ctx.is_visible(&type_alias) {
             Visible::Yes => false,
             Visible::Editable => true,
@@ -372,6 +402,9 @@ impl Completions {
         ctx: &CompletionContext<'_>,
         type_alias: hir::TypeAlias,
     ) {
+        if !ctx.check_stability(Some(&type_alias.attrs(ctx.db))) {
+            return;
+        }
         self.add_opt(render_type_alias_with_eq(RenderContext::new(ctx), type_alias));
     }
 
@@ -382,6 +415,9 @@ impl Completions {
         variant: hir::Variant,
         path: hir::ModPath,
     ) {
+        if !ctx.check_stability(Some(&variant.attrs(ctx.db))) {
+            return;
+        }
         if let Some(builder) =
             render_variant_lit(RenderContext::new(ctx), path_ctx, None, variant, Some(path))
         {
@@ -396,6 +432,9 @@ impl Completions {
         variant: hir::Variant,
         local_name: Option<hir::Name>,
     ) {
+        if !ctx.check_stability(Some(&variant.attrs(ctx.db))) {
+            return;
+        }
         if let PathCompletionCtx { kind: PathKind::Pat { pat_ctx }, .. } = path_ctx {
             cov_mark::hit!(enum_variant_pattern_path);
             self.add_variant_pat(ctx, pat_ctx, Some(path_ctx), variant, local_name);
@@ -417,6 +456,9 @@ impl Completions {
         field: hir::Field,
         ty: &hir::Type,
     ) {
+        if !ctx.check_stability(Some(&field.attrs(ctx.db))) {
+            return;
+        }
         let is_private_editable = match ctx.is_visible(&field) {
             Visible::Yes => false,
             Visible::Editable => true,
@@ -441,6 +483,9 @@ impl Completions {
         path: Option<hir::ModPath>,
         local_name: Option<hir::Name>,
     ) {
+        if !ctx.check_stability(Some(&strukt.attrs(ctx.db))) {
+            return;
+        }
         if let Some(builder) =
             render_struct_literal(RenderContext::new(ctx), path_ctx, strukt, path, local_name)
         {
@@ -455,6 +500,9 @@ impl Completions {
         path: Option<hir::ModPath>,
         local_name: Option<hir::Name>,
     ) {
+        if !ctx.check_stability(Some(&un.attrs(ctx.db))) {
+            return;
+        }
         let item = render_union_literal(RenderContext::new(ctx), un, path, local_name);
         self.add_opt(item);
     }
@@ -466,6 +514,8 @@ impl Completions {
         field: usize,
         ty: &hir::Type,
     ) {
+        // Only used for (unnamed) tuples, whose all fields *are* stable. No need to check
+        // stability here.
         let item = render_tuple_field(RenderContext::new(ctx), receiver, field, ty);
         self.add(item);
     }
@@ -487,6 +537,9 @@ impl Completions {
         variant: hir::Variant,
         local_name: Option<hir::Name>,
     ) {
+        if !ctx.check_stability(Some(&variant.attrs(ctx.db))) {
+            return;
+        }
         self.add_opt(render_variant_pat(
             RenderContext::new(ctx),
             pattern_ctx,
@@ -504,6 +557,9 @@ impl Completions {
         variant: hir::Variant,
         path: hir::ModPath,
     ) {
+        if !ctx.check_stability(Some(&variant.attrs(ctx.db))) {
+            return;
+        }
         let path = Some(&path);
         self.add_opt(render_variant_pat(
             RenderContext::new(ctx),
@@ -522,6 +578,9 @@ impl Completions {
         strukt: hir::Struct,
         local_name: Option<hir::Name>,
     ) {
+        if !ctx.check_stability(Some(&strukt.attrs(ctx.db))) {
+            return;
+        }
         self.add_opt(render_struct_pat(RenderContext::new(ctx), pattern_ctx, strukt, local_name));
     }
 }

crates/ide-completion/src/completions/dot.rs

@@ -172,6 +172,43 @@ fn foo(s: S) { s.$0 }
         );
     }
 
+    #[test]
+    fn no_unstable_method_on_stable() {
+        check(
+            r#"
+//- /main.rs crate:main deps:std
+fn foo(s: std::S) { s.$0 }
+//- /std.rs crate:std
+pub struct S;
+impl S {
+    #[unstable]
+    pub fn bar(&self) {}
+}
+"#,
+            expect![""],
+        );
+    }
+
+    #[test]
+    fn unstable_method_on_nightly() {
+        check(
+            r#"
+//- toolchain:nightly
+//- /main.rs crate:main deps:std
+fn foo(s: std::S) { s.$0 }
+//- /std.rs crate:std
+pub struct S;
+impl S {
+    #[unstable]
+    pub fn bar(&self) {}
+}
+"#,
+            expect![[r#"
+                me bar() fn(&self)
+            "#]],
+        );
+    }
+
     #[test]
     fn test_struct_field_completion_self() {
         check(

crates/ide-completion/src/completions/env_vars.rs

@@ -37,9 +37,9 @@ pub(crate) fn complete_cargo_env_vars(
     guard_env_macro(expanded, &ctx.sema)?;
     let range = expanded.text_range_between_quotes()?;
 
-    CARGO_DEFINED_VARS.iter().for_each(|(var, detail)| {
+    CARGO_DEFINED_VARS.into_iter().for_each(|&(var, detail)| {
         let mut item = CompletionItem::new(CompletionItemKind::Keyword, range, var);
-        item.detail(*detail);
+        item.detail(detail);
         item.add_to(acc);
     });
 

crates/ide-completion/src/completions/flyimport.rs

@@ -262,8 +262,10 @@ fn import_on_the_fly(
         .into_iter()
         .filter(ns_filter)
         .filter(|import| {
+            let original_item = &import.original_item;
             !ctx.is_item_hidden(&import.item_to_import)
-                && !ctx.is_item_hidden(&import.original_item)
+                && !ctx.is_item_hidden(original_item)
+                && ctx.check_stability(original_item.attrs(ctx.db).as_deref())
         })
         .sorted_by_key(|located_import| {
             compute_fuzzy_completion_order_key(&located_import.import_path, &user_input_lowercased)
@@ -302,8 +304,10 @@ fn import_on_the_fly_pat_(
         .into_iter()
         .filter(ns_filter)
         .filter(|import| {
+            let original_item = &import.original_item;
             !ctx.is_item_hidden(&import.item_to_import)
-                && !ctx.is_item_hidden(&import.original_item)
+                && !ctx.is_item_hidden(original_item)
+                && ctx.check_stability(original_item.attrs(ctx.db).as_deref())
         })
         .sorted_by_key(|located_import| {
             compute_fuzzy_completion_order_key(&located_import.import_path, &user_input_lowercased)

crates/ide-completion/src/completions/item_list/trait_impl.rs

@@ -150,21 +150,24 @@ fn complete_trait_impl(
     impl_def: &ast::Impl,
 ) {
     if let Some(hir_impl) = ctx.sema.to_def(impl_def) {
-        get_missing_assoc_items(&ctx.sema, impl_def).into_iter().for_each(|item| {
-            use self::ImplCompletionKind::*;
-            match (item, kind) {
-                (hir::AssocItem::Function(func), All | Fn) => {
-                    add_function_impl(acc, ctx, replacement_range, func, hir_impl)
+        get_missing_assoc_items(&ctx.sema, impl_def)
+            .into_iter()
+            .filter(|item| ctx.check_stability(Some(&item.attrs(ctx.db))))
+            .for_each(|item| {
+                use self::ImplCompletionKind::*;
+                match (item, kind) {
+                    (hir::AssocItem::Function(func), All | Fn) => {
+                        add_function_impl(acc, ctx, replacement_range, func, hir_impl)
+                    }
+                    (hir::AssocItem::TypeAlias(type_alias), All | TypeAlias) => {
+                        add_type_alias_impl(acc, ctx, replacement_range, type_alias, hir_impl)
+                    }
+                    (hir::AssocItem::Const(const_), All | Const) => {
+                        add_const_impl(acc, ctx, replacement_range, const_, hir_impl)
+                    }
+                    _ => {}
                 }
-                (hir::AssocItem::TypeAlias(type_alias), All | TypeAlias) => {
-                    add_type_alias_impl(acc, ctx, replacement_range, type_alias, hir_impl)
-                }
-                (hir::AssocItem::Const(const_), All | Const) => {
-                    add_const_impl(acc, ctx, replacement_range, const_, hir_impl)
-                }
-                _ => {}
-            }
-        });
+            });
     }
 }
 

crates/ide-completion/src/completions/use_.rs

@@ -52,6 +52,9 @@ pub(crate) fn complete_use_path(
                         )
                     };
                     for (name, def) in module_scope {
+                        if !ctx.check_stability(def.attrs(ctx.db).as_deref()) {
+                            continue;
+                        }
                         let is_name_already_imported = name
                             .as_text()
                             .map_or(false, |text| already_imported_names.contains(text.as_str()));

crates/ide-completion/src/context.rs

@@ -367,6 +367,8 @@ pub(crate) struct CompletionContext<'a> {
     pub(super) krate: hir::Crate,
     /// The module of the `scope`.
     pub(super) module: hir::Module,
+    /// Whether nightly toolchain is used. Cached since this is looked up a lot.
+    is_nightly: bool,
 
     /// The expected name of what we are completing.
     /// This is usually the parameter name of the function argument we are completing.
@@ -386,7 +388,7 @@ pub(crate) struct CompletionContext<'a> {
     pub(super) depth_from_crate_root: usize,
 }
 
-impl<'a> CompletionContext<'a> {
+impl CompletionContext<'_> {
     /// The range of the identifier that is being completed.
     pub(crate) fn source_range(&self) -> TextRange {
         let kind = self.original_token.kind();
@@ -459,6 +461,12 @@ impl<'a> CompletionContext<'a> {
         }
     }
 
+    /// Checks whether this item should be listed in regards to stability. Returns `true` if we should.
+    pub(crate) fn check_stability(&self, attrs: Option<&hir::Attrs>) -> bool {
+        let Some(attrs) = attrs else { return true; };
+        !attrs.is_unstable() || self.is_nightly
+    }
+
     /// Whether the given trait is an operator trait or not.
     pub(crate) fn is_ops_trait(&self, trait_: hir::Trait) -> bool {
         match trait_.attrs(self.db).lang() {
@@ -632,6 +640,11 @@ impl<'a> CompletionContext<'a> {
         let krate = scope.krate();
         let module = scope.module();
 
+        let toolchain = db.crate_graph()[krate.into()].channel;
+        // `toolchain == None` means we're in some detached files. Since we have no information on
+        // the toolchain being used, let's just allow unstable items to be listed.
+        let is_nightly = matches!(toolchain, Some(base_db::ReleaseChannel::Nightly) | None);
+
         let mut locals = FxHashMap::default();
         scope.process_all_names(&mut |name, scope| {
             if let ScopeDef::Local(local) = scope {
@@ -651,6 +664,7 @@ impl<'a> CompletionContext<'a> {
             token,
             krate,
             module,
+            is_nightly,
             expected_name,
             expected_type,
             qualifier_ctx,

crates/ide-completion/src/tests.rs

@@ -23,6 +23,7 @@ mod type_pos;
 mod use_tree;
 mod visibility;
 
+use expect_test::Expect;
 use hir::PrefixKind;
 use ide_db::{
     base_db::{fixture::ChangeFixture, FileLoader, FilePosition},
@@ -215,6 +216,11 @@ pub(crate) fn check_edit_with_config(
     assert_eq_text!(&ra_fixture_after, &actual)
 }
 
+fn check_empty(ra_fixture: &str, expect: Expect) {
+    let actual = completion_list(ra_fixture);
+    expect.assert_eq(&actual);
+}
+
 pub(crate) fn get_all_items(
     config: CompletionConfig,
     code: &str,

crates/ide-completion/src/tests/expression.rs

@@ -1,18 +1,13 @@
 //! Completion tests for expressions.
 use expect_test::{expect, Expect};
 
-use crate::tests::{check_edit, completion_list, BASE_ITEMS_FIXTURE};
+use crate::tests::{check_edit, check_empty, completion_list, BASE_ITEMS_FIXTURE};
 
 fn check(ra_fixture: &str, expect: Expect) {
     let actual = completion_list(&format!("{BASE_ITEMS_FIXTURE}{ra_fixture}"));
     expect.assert_eq(&actual)
 }
 
-fn check_empty(ra_fixture: &str, expect: Expect) {
-    let actual = completion_list(ra_fixture);
-    expect.assert_eq(&actual);
-}
-
 #[test]
 fn complete_literal_struct_with_a_private_field() {
     // `FooDesc.bar` is private, the completion should not be triggered.
@@ -997,3 +992,105 @@ fn foo() { if foo {} el$0 { let x = 92; } }
         "#]],
     );
 }
+
+#[test]
+fn expr_no_unstable_item_on_stable() {
+    check_empty(
+        r#"
+//- /main.rs crate:main deps:std
+use std::*;
+fn main() {
+    $0
+}
+//- /std.rs crate:std
+#[unstable]
+pub struct UnstableThisShouldNotBeListed;
+"#,
+        expect![[r#"
+            fn main()      fn()
+            md std
+            bt u32
+            kw const
+            kw crate::
+            kw enum
+            kw extern
+            kw false
+            kw fn
+            kw for
+            kw if
+            kw if let
+            kw impl
+            kw let
+            kw loop
+            kw match
+            kw mod
+            kw return
+            kw self::
+            kw static
+            kw struct
+            kw trait
+            kw true
+            kw type
+            kw union
+            kw unsafe
+            kw use
+            kw while
+            kw while let
+            sn macro_rules
+            sn pd
+            sn ppd
+        "#]],
+    );
+}
+
+#[test]
+fn expr_unstable_item_on_nightly() {
+    check_empty(
+        r#"
+//- toolchain:nightly
+//- /main.rs crate:main deps:std
+use std::*;
+fn main() {
+    $0
+}
+//- /std.rs crate:std
+#[unstable]
+pub struct UnstableButWeAreOnNightlyAnyway;
+"#,
+        expect![[r#"
+            fn main()                 fn()
+            md std
+            st UnstableButWeAreOnNightlyAnyway
+            bt u32
+            kw const
+            kw crate::
+            kw enum
+            kw extern
+            kw false
+            kw fn
+            kw for
+            kw if
+            kw if let
+            kw impl
+            kw let
+            kw loop
+            kw match
+            kw mod
+            kw return
+            kw self::
+            kw static
+            kw struct
+            kw trait
+            kw true
+            kw type
+            kw union
+            kw unsafe
+            kw use
+            kw while
+            kw while let
+            sn macro_rules
+            sn pd
+            sn ppd
+        "#]],
+    );
+}