Auto merge of #3197 - RalfJung:rustup, r=RalfJung

Rustup

also move some fail tests into suitable subdirectories

.github/workflows/ci.yml

@@ -56,7 +56,7 @@ jobs:
           - name: mingw-check-tidy
             os: ubuntu-20.04-4core-16gb
             env: {}
-          - name: x86_64-gnu-llvm-15
+          - name: x86_64-gnu-llvm-16
             env:
               ENABLE_GCC_CODEGEN: "1"
             os: ubuntu-20.04-16core-64gb
@@ -302,10 +302,6 @@ jobs:
             env:
               RUST_BACKTRACE: 1
             os: ubuntu-20.04-8core-32gb
-          - name: x86_64-gnu-llvm-15
-            env:
-              RUST_BACKTRACE: 1
-            os: ubuntu-20.04-8core-32gb
           - name: x86_64-gnu-nopt
             os: ubuntu-20.04-4core-16gb
             env: {}

.mailmap

@@ -575,7 +575,8 @@ Val Markovic <val@markovic.io>
 Valerii Lashmanov <vflashm@gmail.com>
 Vitali Haravy <HumaneProgrammer@gmail.com> Vitali Haravy <humaneprogrammer@gmail.com>
 Vitaly Shukela <vi0oss@gmail.com>
-Waffle Maybe <waffle.lapkin@gmail.com>
+Waffle Lapkin <waffle.lapkin@gmail.com>
+Waffle Lapkin <waffle.lapkin@tasking.com>
 Wesley Wiser <wwiser@gmail.com> <wesleywiser@microsoft.com>
 whitequark <whitequark@whitequark.org>
 William Ting <io@williamting.com> <william.h.ting@gmail.com>

compiler/rustc_ast/src/ast.rs

@@ -645,6 +645,7 @@ impl Pat {
             // These patterns do not contain subpatterns, skip.
             PatKind::Wild
             | PatKind::Rest
+            | PatKind::Never
             | PatKind::Lit(_)
             | PatKind::Range(..)
             | PatKind::Ident(..)
@@ -795,6 +796,9 @@ pub enum PatKind {
     /// only one rest pattern may occur in the pattern sequences.
     Rest,
 
+    // A never pattern `!`
+    Never,
+
     /// Parentheses in patterns used for grouping (i.e., `(PAT)`).
     Paren(P<Pat>),
 
@@ -817,7 +821,7 @@ pub enum BorrowKind {
     Raw,
 }
 
-#[derive(Clone, PartialEq, Encodable, Decodable, Debug, Copy)]
+#[derive(Clone, Copy, Debug, PartialEq, Encodable, Decodable, HashStable_Generic)]
 pub enum BinOpKind {
     /// The `+` operator (addition)
     Add,
@@ -858,9 +862,9 @@ pub enum BinOpKind {
 }
 
 impl BinOpKind {
-    pub fn to_string(&self) -> &'static str {
+    pub fn as_str(&self) -> &'static str {
         use BinOpKind::*;
-        match *self {
+        match self {
             Add => "+",
             Sub => "-",
             Mul => "*",
@@ -881,19 +885,25 @@ impl BinOpKind {
             Gt => ">",
         }
     }
-    pub fn lazy(&self) -> bool {
+
+    pub fn is_lazy(&self) -> bool {
         matches!(self, BinOpKind::And | BinOpKind::Or)
     }
 
     pub fn is_comparison(&self) -> bool {
         use BinOpKind::*;
-        // Note for developers: please keep this as is;
+        // Note for developers: please keep this match exhaustive;
         // we want compilation to fail if another variant is added.
         match *self {
             Eq | Lt | Le | Ne | Gt | Ge => true,
             And | Or | Add | Sub | Mul | Div | Rem | BitXor | BitAnd | BitOr | Shl | Shr => false,
         }
     }
+
+    /// Returns `true` if the binary operator takes its arguments by value.
+    pub fn is_by_value(self) -> bool {
+        !self.is_comparison()
+    }
 }
 
 pub type BinOp = Spanned<BinOpKind>;
@@ -901,7 +911,7 @@ pub type BinOp = Spanned<BinOpKind>;
 /// Unary operator.
 ///
 /// Note that `&data` is not an operator, it's an `AddrOf` expression.
-#[derive(Clone, Encodable, Decodable, Debug, Copy)]
+#[derive(Clone, Copy, Debug, PartialEq, Encodable, Decodable, HashStable_Generic)]
 pub enum UnOp {
     /// The `*` operator for dereferencing
     Deref,
@@ -912,13 +922,18 @@ pub enum UnOp {
 }
 
 impl UnOp {
-    pub fn to_string(op: UnOp) -> &'static str {
+    pub fn as_str(&self) -> &'static str {
-        match op {
+        match self {
             UnOp::Deref => "*",
             UnOp::Not => "!",
             UnOp::Neg => "-",
         }
     }
+
+    /// Returns `true` if the unary operator takes its argument by value.
+    pub fn is_by_value(self) -> bool {
+        matches!(self, Self::Neg | Self::Not)
+    }
 }
 
 /// A statement

compiler/rustc_ast/src/mut_visit.rs

@@ -1249,7 +1249,7 @@ pub fn noop_visit_pat<T: MutVisitor>(pat: &mut P<Pat>, vis: &mut T) {
     let Pat { id, kind, span, tokens } = pat.deref_mut();
     vis.visit_id(id);
     match kind {
-        PatKind::Wild | PatKind::Rest => {}
+        PatKind::Wild | PatKind::Rest | PatKind::Never => {}
         PatKind::Ident(_binding_mode, ident, sub) => {
             vis.visit_ident(ident);
             visit_opt(sub, |sub| vis.visit_pat(sub));

compiler/rustc_ast/src/token.rs

@@ -756,6 +756,11 @@ impl Token {
         )
     }
 
+    /// Returns `true` if the token is the integer literal.
+    pub fn is_integer_lit(&self) -> bool {
+        matches!(self.kind, Literal(Lit { kind: LitKind::Integer, .. }))
+    }
+
     /// Returns `true` if the token is a non-raw identifier for which `pred` holds.
     pub fn is_non_raw_ident_where(&self, pred: impl FnOnce(Ident) -> bool) -> bool {
         match self.ident() {

compiler/rustc_ast/src/visit.rs

@@ -559,7 +559,7 @@ pub fn walk_pat<'a, V: Visitor<'a>>(visitor: &mut V, pattern: &'a Pat) {
             walk_list!(visitor, visit_expr, lower_bound);
             walk_list!(visitor, visit_expr, upper_bound);
         }
-        PatKind::Wild | PatKind::Rest => {}
+        PatKind::Wild | PatKind::Rest | PatKind::Never => {}
         PatKind::Tuple(elems) | PatKind::Slice(elems) | PatKind::Or(elems) => {
             walk_list!(visitor, visit_pat, elems);
         }

compiler/rustc_ast_lowering/src/asm.rs

@@ -228,6 +228,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                                 parent_def_id.def_id,
                                 node_id,
                                 DefPathData::AnonConst,
+                                DefKind::AnonConst,
                                 *op_sp,
                             );
                             let anon_const = AnonConst { id: node_id, value: P(expr) };

compiler/rustc_ast_lowering/src/expr.rs

@@ -12,7 +12,7 @@ use rustc_ast::ptr::P as AstP;
 use rustc_ast::*;
 use rustc_data_structures::stack::ensure_sufficient_stack;
 use rustc_hir as hir;
-use rustc_hir::def::Res;
+use rustc_hir::def::{DefKind, Res};
 use rustc_hir::definitions::DefPathData;
 use rustc_session::errors::report_lit_error;
 use rustc_span::source_map::{respan, Spanned};
@@ -72,7 +72,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
             let kind = match &e.kind {
                 ExprKind::Array(exprs) => hir::ExprKind::Array(self.lower_exprs(exprs)),
                 ExprKind::ConstBlock(c) => {
-                    let c = self.with_new_scopes(|this| hir::ConstBlock {
+                    let c = self.with_new_scopes(c.value.span, |this| hir::ConstBlock {
                         def_id: this.local_def_id(c.id),
                         hir_id: this.lower_node_id(c.id),
                         body: this.lower_const_body(c.value.span, Some(&c.value)),
@@ -189,7 +189,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     None,
                     e.span,
                     hir::CoroutineSource::Block,
-                    |this| this.with_new_scopes(|this| this.lower_block_expr(block)),
+                    |this| this.with_new_scopes(e.span, |this| this.lower_block_expr(block)),
                 ),
                 ExprKind::Await(expr, await_kw_span) => self.lower_expr_await(*await_kw_span, expr),
                 ExprKind::Closure(box Closure {
@@ -323,7 +323,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     None,
                     e.span,
                     hir::CoroutineSource::Block,
-                    |this| this.with_new_scopes(|this| this.lower_block_expr(block)),
+                    |this| this.with_new_scopes(e.span, |this| this.lower_block_expr(block)),
                 ),
                 ExprKind::Yield(opt_expr) => self.lower_expr_yield(e.span, opt_expr.as_deref()),
                 ExprKind::Err => hir::ExprKind::Err(
@@ -350,30 +350,8 @@ impl<'hir> LoweringContext<'_, 'hir> {
         }
     }
 
-    fn lower_binop(&mut self, b: BinOp) -> hir::BinOp {
+    fn lower_binop(&mut self, b: BinOp) -> BinOp {
-        Spanned {
+        Spanned { node: b.node, span: self.lower_span(b.span) }
-            node: match b.node {
-                BinOpKind::Add => hir::BinOpKind::Add,
-                BinOpKind::Sub => hir::BinOpKind::Sub,
-                BinOpKind::Mul => hir::BinOpKind::Mul,
-                BinOpKind::Div => hir::BinOpKind::Div,
-                BinOpKind::Rem => hir::BinOpKind::Rem,
-                BinOpKind::And => hir::BinOpKind::And,
-                BinOpKind::Or => hir::BinOpKind::Or,
-                BinOpKind::BitXor => hir::BinOpKind::BitXor,
-                BinOpKind::BitAnd => hir::BinOpKind::BitAnd,
-                BinOpKind::BitOr => hir::BinOpKind::BitOr,
-                BinOpKind::Shl => hir::BinOpKind::Shl,
-                BinOpKind::Shr => hir::BinOpKind::Shr,
-                BinOpKind::Eq => hir::BinOpKind::Eq,
-                BinOpKind::Lt => hir::BinOpKind::Lt,
-                BinOpKind::Le => hir::BinOpKind::Le,
-                BinOpKind::Ne => hir::BinOpKind::Ne,
-                BinOpKind::Ge => hir::BinOpKind::Ge,
-                BinOpKind::Gt => hir::BinOpKind::Gt,
-            },
-            span: self.lower_span(b.span),
-        }
     }
 
     fn lower_legacy_const_generics(
@@ -395,7 +373,13 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 let node_id = self.next_node_id();
 
                 // Add a definition for the in-band const def.
-                self.create_def(parent_def_id.def_id, node_id, DefPathData::AnonConst, f.span);
+                self.create_def(
+                    parent_def_id.def_id,
+                    node_id,
+                    DefPathData::AnonConst,
+                    DefKind::AnonConst,
+                    f.span,
+                );
 
                 let anon_const = AnonConst { id: node_id, value: arg };
                 generic_args.push(AngleBracketedArg::Arg(GenericArg::Const(anon_const)));
@@ -524,7 +508,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     this.mark_span_with_reason(
                         DesugaringKind::TryBlock,
                         expr.span,
-                        this.allow_try_trait.clone(),
+                        Some(this.allow_try_trait.clone()),
                     ),
                     expr,
                 )
@@ -532,7 +516,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 let try_span = this.mark_span_with_reason(
                     DesugaringKind::TryBlock,
                     this.tcx.sess.source_map().end_point(body.span),
-                    this.allow_try_trait.clone(),
+                    Some(this.allow_try_trait.clone()),
                 );
 
                 (try_span, this.expr_unit(try_span))
@@ -612,8 +596,11 @@ impl<'hir> LoweringContext<'_, 'hir> {
         let output = ret_ty.unwrap_or_else(|| hir::FnRetTy::DefaultReturn(self.lower_span(span)));
 
         // Resume argument type: `ResumeTy`
-        let unstable_span =
+        let unstable_span = self.mark_span_with_reason(
-            self.mark_span_with_reason(DesugaringKind::Async, span, self.allow_gen_future.clone());
+            DesugaringKind::Async,
+            span,
+            Some(self.allow_gen_future.clone()),
+        );
         let resume_ty = hir::QPath::LangItem(hir::LangItem::ResumeTy, unstable_span);
         let input_ty = hir::Ty {
             hir_id: self.next_id(),
@@ -735,7 +722,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
             let unstable_span = self.mark_span_with_reason(
                 DesugaringKind::Async,
                 span,
-                self.allow_gen_future.clone(),
+                Some(self.allow_gen_future.clone()),
             );
             self.lower_attrs(
                 inner_hir_id,
@@ -772,17 +759,17 @@ impl<'hir> LoweringContext<'_, 'hir> {
         match self.coroutine_kind {
             Some(hir::CoroutineKind::Async(_)) => {}
             Some(hir::CoroutineKind::Coroutine) | Some(hir::CoroutineKind::Gen(_)) | None => {
-                self.tcx.sess.emit_err(AwaitOnlyInAsyncFnAndBlocks {
+                return hir::ExprKind::Err(self.tcx.sess.emit_err(AwaitOnlyInAsyncFnAndBlocks {
                     await_kw_span,
                     item_span: self.current_item,
-                });
+                }));
             }
         }
         let span = self.mark_span_with_reason(DesugaringKind::Await, await_kw_span, None);
         let gen_future_span = self.mark_span_with_reason(
             DesugaringKind::Await,
             full_span,
-            self.allow_gen_future.clone(),
+            Some(self.allow_gen_future.clone()),
         );
         let expr = self.lower_expr_mut(expr);
         let expr_hir_id = expr.hir_id;
@@ -935,9 +922,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
     ) -> hir::ExprKind<'hir> {
         let (binder_clause, generic_params) = self.lower_closure_binder(binder);
 
-        let (body_id, coroutine_option) = self.with_new_scopes(move |this| {
+        let (body_id, coroutine_option) = self.with_new_scopes(fn_decl_span, move |this| {
-            let prev = this.current_item;
-            this.current_item = Some(fn_decl_span);
             let mut coroutine_kind = None;
             let body_id = this.lower_fn_body(decl, |this| {
                 let e = this.lower_expr_mut(body);
@@ -946,7 +931,6 @@ impl<'hir> LoweringContext<'_, 'hir> {
             });
             let coroutine_option =
                 this.coroutine_movability_for_fn(decl, fn_decl_span, coroutine_kind, movability);
-            this.current_item = prev;
             (body_id, coroutine_option)
         });
 
@@ -1032,7 +1016,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
         let outer_decl =
             FnDecl { inputs: decl.inputs.clone(), output: FnRetTy::Default(fn_decl_span) };
 
-        let body = self.with_new_scopes(|this| {
+        let body = self.with_new_scopes(fn_decl_span, |this| {
             // FIXME(cramertj): allow `async` non-`move` closures with arguments.
             if capture_clause == CaptureBy::Ref && !decl.inputs.is_empty() {
                 this.tcx.sess.emit_err(AsyncNonMoveClosureNotSupported { fn_decl_span });
@@ -1054,7 +1038,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     async_ret_ty,
                     body.span,
                     hir::CoroutineSource::Closure,
-                    |this| this.with_new_scopes(|this| this.lower_expr_mut(body)),
+                    |this| this.with_new_scopes(fn_decl_span, |this| this.lower_expr_mut(body)),
                 );
                 let hir_id = this.lower_node_id(inner_closure_id);
                 this.maybe_forward_track_caller(body.span, closure_hir_id, hir_id);
@@ -1494,7 +1478,9 @@ impl<'hir> LoweringContext<'_, 'hir> {
         match self.coroutine_kind {
             Some(hir::CoroutineKind::Gen(_)) => {}
             Some(hir::CoroutineKind::Async(_)) => {
-                self.tcx.sess.emit_err(AsyncCoroutinesNotSupported { span });
+                return hir::ExprKind::Err(
+                    self.tcx.sess.emit_err(AsyncCoroutinesNotSupported { span }),
+                );
             }
             Some(hir::CoroutineKind::Coroutine) | None => {
                 if !self.tcx.features().coroutines {
@@ -1640,13 +1626,13 @@ impl<'hir> LoweringContext<'_, 'hir> {
         let unstable_span = self.mark_span_with_reason(
             DesugaringKind::QuestionMark,
             span,
-            self.allow_try_trait.clone(),
+            Some(self.allow_try_trait.clone()),
         );
         let try_span = self.tcx.sess.source_map().end_point(span);
         let try_span = self.mark_span_with_reason(
             DesugaringKind::QuestionMark,
             try_span,
-            self.allow_try_trait.clone(),
+            Some(self.allow_try_trait.clone()),
         );
 
         // `Try::branch(<expr>)`
@@ -1739,7 +1725,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
         let unstable_span = self.mark_span_with_reason(
             DesugaringKind::YeetExpr,
             span,
-            self.allow_try_trait.clone(),
+            Some(self.allow_try_trait.clone()),
         );
 
         let from_yeet_expr = self.wrap_in_try_constructor(

compiler/rustc_ast_lowering/src/index.rs

@@ -10,7 +10,7 @@ use rustc_middle::ty::TyCtxt;
 use rustc_span::{Span, DUMMY_SP};
 
 /// A visitor that walks over the HIR and collects `Node`s into a HIR map.
-pub(super) struct NodeCollector<'a, 'hir> {
+struct NodeCollector<'a, 'hir> {
     tcx: TyCtxt<'hir>,
 
     bodies: &'a SortedMap<ItemLocalId, &'hir Body<'hir>>,

compiler/rustc_ast_lowering/src/item.rs

@@ -7,7 +7,6 @@ use hir::definitions::DefPathData;
 use rustc_ast::ptr::P;
 use rustc_ast::visit::AssocCtxt;
 use rustc_ast::*;
-use rustc_data_structures::sorted_map::SortedMap;
 use rustc_errors::ErrorGuaranteed;
 use rustc_hir as hir;
 use rustc_hir::def::{DefKind, Res};
@@ -55,42 +54,7 @@ impl<'a, 'hir> ItemLowerer<'a, 'hir> {
         owner: NodeId,
         f: impl FnOnce(&mut LoweringContext<'_, 'hir>) -> hir::OwnerNode<'hir>,
     ) {
-        let allow_gen_future = Some(if self.tcx.features().async_fn_track_caller {
+        let mut lctx = LoweringContext::new(self.tcx, self.resolver);
-            [sym::gen_future, sym::closure_track_caller][..].into()
-        } else {
-            [sym::gen_future][..].into()
-        });
-        let mut lctx = LoweringContext {
-            // Pseudo-globals.
-            tcx: self.tcx,
-            resolver: self.resolver,
-            arena: self.tcx.hir_arena,
-
-            // HirId handling.
-            bodies: Vec::new(),
-            attrs: SortedMap::default(),
-            children: Vec::default(),
-            current_hir_id_owner: hir::CRATE_OWNER_ID,
-            item_local_id_counter: hir::ItemLocalId::new(0),
-            node_id_to_local_id: Default::default(),
-            trait_map: Default::default(),
-
-            // Lowering state.
-            catch_scope: None,
-            loop_scope: None,
-            is_in_loop_condition: false,
-            is_in_trait_impl: false,
-            is_in_dyn_type: false,
-            coroutine_kind: None,
-            task_context: None,
-            current_item: None,
-            impl_trait_defs: Vec::new(),
-            impl_trait_bounds: Vec::new(),
-            allow_try_trait: Some([sym::try_trait_v2, sym::yeet_desugar_details][..].into()),
-            allow_gen_future,
-            generics_def_id_map: Default::default(),
-            host_param_id: None,
-        };
         lctx.with_hir_id_owner(owner, |lctx| f(lctx));
 
         for (def_id, info) in lctx.children {
@@ -136,39 +100,9 @@ impl<'a, 'hir> ItemLowerer<'a, 'hir> {
 
     fn lower_assoc_item(&mut self, item: &AssocItem, ctxt: AssocCtxt) {
         let def_id = self.resolver.node_id_to_def_id[&item.id];
-
         let parent_id = self.tcx.local_parent(def_id);
         let parent_hir = self.lower_node(parent_id).unwrap();
-        self.with_lctx(item.id, |lctx| {
+        self.with_lctx(item.id, |lctx| lctx.lower_assoc_item(item, ctxt, parent_hir))
-            // Evaluate with the lifetimes in `params` in-scope.
-            // This is used to track which lifetimes have already been defined,
-            // and which need to be replicated when lowering an async fn.
-
-            match parent_hir.node().expect_item().kind {
-                hir::ItemKind::Impl(impl_) => {
-                    lctx.is_in_trait_impl = impl_.of_trait.is_some();
-                }
-                hir::ItemKind::Trait(_, _, generics, _, _) if lctx.tcx.features().effects => {
-                    lctx.host_param_id = generics
-                        .params
-                        .iter()
-                        .find(|param| {
-                            parent_hir
-                                .attrs
-                                .get(param.hir_id.local_id)
-                                .iter()
-                                .any(|attr| attr.has_name(sym::rustc_host))
-                        })
-                        .map(|param| param.def_id);
-                }
-                _ => {}
-            }
-
-            match ctxt {
-                AssocCtxt::Trait => hir::OwnerNode::TraitItem(lctx.lower_trait_item(item)),
-                AssocCtxt::Impl => hir::OwnerNode::ImplItem(lctx.lower_impl_item(item)),
-            }
-        })
     }
 
     fn lower_foreign_item(&mut self, item: &ForeignItem) {
@@ -268,9 +202,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 body,
                 ..
             }) => {
-                self.with_new_scopes(|this| {
+                self.with_new_scopes(ident.span, |this| {
-                    this.current_item = Some(ident.span);
-
                     // Note: we don't need to change the return type from `T` to
                     // `impl Future<Output = T>` here because lower_body
                     // only cares about the input argument patterns in the function
@@ -480,7 +412,9 @@ impl<'hir> LoweringContext<'_, 'hir> {
             }
             ItemKind::MacroDef(MacroDef { body, macro_rules }) => {
                 let body = P(self.lower_delim_args(body));
-                let macro_kind = self.resolver.decl_macro_kind(self.local_def_id(id));
+                let DefKind::Macro(macro_kind) = self.tcx.def_kind(self.local_def_id(id)) else {
+                    unreachable!()
+                };
                 let macro_def = self.arena.alloc(ast::MacroDef { body, macro_rules: *macro_rules });
                 hir::ItemKind::Macro(macro_def, macro_kind)
             }
@@ -609,6 +543,42 @@ impl<'hir> LoweringContext<'_, 'hir> {
         }
     }
 
+    fn lower_assoc_item(
+        &mut self,
+        item: &AssocItem,
+        ctxt: AssocCtxt,
+        parent_hir: &'hir hir::OwnerInfo<'hir>,
+    ) -> hir::OwnerNode<'hir> {
+        // Evaluate with the lifetimes in `params` in-scope.
+        // This is used to track which lifetimes have already been defined,
+        // and which need to be replicated when lowering an async fn.
+
+        match parent_hir.node().expect_item().kind {
+            hir::ItemKind::Impl(impl_) => {
+                self.is_in_trait_impl = impl_.of_trait.is_some();
+            }
+            hir::ItemKind::Trait(_, _, generics, _, _) if self.tcx.features().effects => {
+                self.host_param_id = generics
+                    .params
+                    .iter()
+                    .find(|param| {
+                        parent_hir
+                            .attrs
+                            .get(param.hir_id.local_id)
+                            .iter()
+                            .any(|attr| attr.has_name(sym::rustc_host))
+                    })
+                    .map(|param| param.def_id);
+            }
+            _ => {}
+        }
+
+        match ctxt {
+            AssocCtxt::Trait => hir::OwnerNode::TraitItem(self.lower_trait_item(item)),
+            AssocCtxt::Impl => hir::OwnerNode::ImplItem(self.lower_impl_item(item)),
+        }
+    }
+
     fn lower_foreign_item(&mut self, i: &ForeignItem) -> &'hir hir::ForeignItem<'hir> {
         let hir_id = self.lower_node_id(i.id);
         let owner_id = hir_id.expect_owner();
@@ -865,7 +835,6 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 },
             ),
             AssocItemKind::Fn(box Fn { sig, generics, body, .. }) => {
-                self.current_item = Some(i.span);
                 let asyncness = sig.header.asyncness;
                 let body_id = self.lower_maybe_async_body(
                     i.span,
@@ -1399,6 +1368,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     self.local_def_id(parent_node_id),
                     param_node_id,
                     DefPathData::TypeNs(sym::host),
+                    DefKind::ConstParam,
                     span,
                 );
                 self.host_param_id = Some(def_id);
@@ -1457,8 +1427,13 @@ impl<'hir> LoweringContext<'_, 'hir> {
 
         if let Some((span, hir_id, def_id)) = host_param_parts {
             let const_node_id = self.next_node_id();
-            let anon_const: LocalDefId =
+            let anon_const = self.create_def(
-                self.create_def(def_id, const_node_id, DefPathData::AnonConst, span);
+                def_id,
+                const_node_id,
+                DefPathData::AnonConst,
+                DefKind::AnonConst,
+                span,
+            );
 
             let const_id = self.next_id();
             let const_expr_id = self.next_id();

compiler/rustc_ast_lowering/src/lib.rs

@@ -35,7 +35,6 @@
 #![doc(rust_logo)]
 #![feature(box_patterns)]
 #![feature(let_chains)]
-#![feature(never_type)]
 #![recursion_limit = "256"]
 #![deny(rustc::untranslatable_diagnostic)]
 #![deny(rustc::diagnostic_outside_of_impl)]
@@ -67,7 +66,6 @@ use rustc_middle::{
     ty::{ResolverAstLowering, TyCtxt},
 };
 use rustc_session::parse::{add_feature_diagnostics, feature_err};
-use rustc_span::hygiene::MacroKind;
 use rustc_span::symbol::{kw, sym, Ident, Symbol};
 use rustc_span::{DesugaringKind, Span, DUMMY_SP};
 use smallvec::SmallVec;
@@ -133,8 +131,8 @@ struct LoweringContext<'a, 'hir> {
     /// NodeIds that are lowered inside the current HIR owner.
     node_id_to_local_id: FxHashMap<NodeId, hir::ItemLocalId>,
 
-    allow_try_trait: Option<Lrc<[Symbol]>>,
+    allow_try_trait: Lrc<[Symbol]>,
-    allow_gen_future: Option<Lrc<[Symbol]>>,
+    allow_gen_future: Lrc<[Symbol]>,
 
     /// Mapping from generics `def_id`s to TAIT generics `def_id`s.
     /// For each captured lifetime (e.g., 'a), we create a new lifetime parameter that is a generic
@@ -145,6 +143,46 @@ struct LoweringContext<'a, 'hir> {
     host_param_id: Option<LocalDefId>,
 }
 
+impl<'a, 'hir> LoweringContext<'a, 'hir> {
+    fn new(tcx: TyCtxt<'hir>, resolver: &'a mut ResolverAstLowering) -> Self {
+        Self {
+            // Pseudo-globals.
+            tcx,
+            resolver: resolver,
+            arena: tcx.hir_arena,
+
+            // HirId handling.
+            bodies: Vec::new(),
+            attrs: SortedMap::default(),
+            children: Vec::default(),
+            current_hir_id_owner: hir::CRATE_OWNER_ID,
+            item_local_id_counter: hir::ItemLocalId::new(0),
+            node_id_to_local_id: Default::default(),
+            trait_map: Default::default(),
+
+            // Lowering state.
+            catch_scope: None,
+            loop_scope: None,
+            is_in_loop_condition: false,
+            is_in_trait_impl: false,
+            is_in_dyn_type: false,
+            coroutine_kind: None,
+            task_context: None,
+            current_item: None,
+            impl_trait_defs: Vec::new(),
+            impl_trait_bounds: Vec::new(),
+            allow_try_trait: [sym::try_trait_v2, sym::yeet_desugar_details].into(),
+            allow_gen_future: if tcx.features().async_fn_track_caller {
+                [sym::gen_future, sym::closure_track_caller].into()
+            } else {
+                [sym::gen_future].into()
+            },
+            generics_def_id_map: Default::default(),
+            host_param_id: None,
+        }
+    }
+}
+
 trait ResolverAstLoweringExt {
     fn legacy_const_generic_args(&self, expr: &Expr) -> Option<Vec<usize>>;
     fn get_partial_res(&self, id: NodeId) -> Option<PartialRes>;
@@ -153,7 +191,6 @@ trait ResolverAstLoweringExt {
     fn get_lifetime_res(&self, id: NodeId) -> Option<LifetimeRes>;
     fn take_extra_lifetime_params(&mut self, id: NodeId) -> Vec<(Ident, NodeId, LifetimeRes)>;
     fn remap_extra_lifetime_params(&mut self, from: NodeId, to: NodeId);
-    fn decl_macro_kind(&self, def_id: LocalDefId) -> MacroKind;
 }
 
 impl ResolverAstLoweringExt for ResolverAstLowering {
@@ -217,10 +254,6 @@ impl ResolverAstLoweringExt for ResolverAstLowering {
         let lifetimes = self.extra_lifetime_params_map.remove(&from).unwrap_or_default();
         self.extra_lifetime_params_map.insert(to, lifetimes);
     }
-
-    fn decl_macro_kind(&self, def_id: LocalDefId) -> MacroKind {
-        self.builtin_macro_kinds.get(&def_id).copied().unwrap_or(MacroKind::Bang)
-    }
 }
 
 /// Context of `impl Trait` in code, which determines whether it is allowed in an HIR subtree,
@@ -467,6 +500,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         parent: LocalDefId,
         node_id: ast::NodeId,
         data: DefPathData,
+        def_kind: DefKind,
         span: Span,
     ) -> LocalDefId {
         debug_assert_ne!(node_id, ast::DUMMY_NODE_ID);
@@ -478,7 +512,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
             self.tcx.hir().def_key(self.local_def_id(node_id)),
         );
 
-        let def_id = self.tcx.at(span).create_def(parent, data).def_id();
+        let def_id = self.tcx.at(span).create_def(parent, data, def_kind).def_id();
 
         debug!("create_def: def_id_to_node_id[{:?}] <-> {:?}", def_id, node_id);
         self.resolver.node_id_to_def_id.insert(node_id, def_id);
@@ -780,6 +814,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                     self.current_hir_id_owner.def_id,
                     param,
                     DefPathData::LifetimeNs(kw::UnderscoreLifetime),
+                    DefKind::LifetimeParam,
                     ident.span,
                 );
                 debug!(?_def_id);
@@ -843,7 +878,10 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         result
     }
 
-    fn with_new_scopes<T>(&mut self, f: impl FnOnce(&mut Self) -> T) -> T {
+    fn with_new_scopes<T>(&mut self, scope_span: Span, f: impl FnOnce(&mut Self) -> T) -> T {
+        let current_item = self.current_item;
+        self.current_item = Some(scope_span);
+
         let was_in_loop_condition = self.is_in_loop_condition;
         self.is_in_loop_condition = false;
 
@@ -855,6 +893,8 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
 
         self.is_in_loop_condition = was_in_loop_condition;
 
+        self.current_item = current_item;
+
         ret
     }
 
@@ -1192,6 +1232,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                                     parent_def_id.def_id,
                                     node_id,
                                     DefPathData::AnonConst,
+                                    DefKind::AnonConst,
                                     span,
                                 );
 
@@ -1203,7 +1244,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                                     tokens: None,
                                 };
 
-                                let ct = self.with_new_scopes(|this| hir::AnonConst {
+                                let ct = self.with_new_scopes(span, |this| hir::AnonConst {
                                     def_id,
                                     hir_id: this.lower_node_id(node_id),
                                     body: this.lower_const_body(path_expr.span, Some(&path_expr)),
@@ -1429,6 +1470,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                             self.current_hir_id_owner.def_id,
                             *def_node_id,
                             DefPathData::TypeNs(ident.name),
+                            DefKind::TyParam,
                             span,
                         );
                         let (param, bounds, path) = self.lower_universal_param_and_bounds(
@@ -1582,6 +1624,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
             self.current_hir_id_owner.def_id,
             opaque_ty_node_id,
             DefPathData::ImplTrait,
+            DefKind::OpaqueTy,
             opaque_ty_span,
         );
         debug!(?opaque_ty_def_id);
@@ -1636,6 +1679,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                     opaque_ty_def_id,
                     duplicated_lifetime_node_id,
                     DefPathData::LifetimeNs(lifetime.ident.name),
+                    DefKind::LifetimeParam,
                     lifetime.ident.span,
                 );
                 captured_to_synthesized_mapping.insert(old_def_id, duplicated_lifetime_def_id);
@@ -2207,7 +2251,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
     }
 
     fn lower_anon_const(&mut self, c: &AnonConst) -> hir::AnonConst {
-        self.with_new_scopes(|this| hir::AnonConst {
+        self.with_new_scopes(c.value.span, |this| hir::AnonConst {
             def_id: this.local_def_id(c.id),
             hir_id: this.lower_node_id(c.id),
             body: this.lower_const_body(c.value.span, Some(&c.value)),
@@ -2505,8 +2549,13 @@ impl<'hir> GenericArgsCtor<'hir> {
         });
         lcx.attrs.insert(hir_id.local_id, std::slice::from_ref(attr));
 
-        let def_id =
+        let def_id = lcx.create_def(
-            lcx.create_def(lcx.current_hir_id_owner.def_id, id, DefPathData::AnonConst, span);
+            lcx.current_hir_id_owner.def_id,
+            id,
+            DefPathData::AnonConst,
+            DefKind::AnonConst,
+            span,
+        );
         lcx.children.push((def_id, hir::MaybeOwner::NonOwner(hir_id)));
         self.args.push(hir::GenericArg::Const(hir::ConstArg {
             value: hir::AnonConst { def_id, hir_id, body },

compiler/rustc_ast_lowering/src/lifetime_collector.rs

@@ -108,7 +108,7 @@ impl<'ast> Visitor<'ast> for LifetimeCollectVisitor<'ast> {
     }
 }
 
-pub fn lifetimes_in_bounds(
+pub(crate) fn lifetimes_in_bounds(
     resolver: &ResolverAstLowering,
     bounds: &GenericBounds,
 ) -> Vec<Lifetime> {

compiler/rustc_ast_lowering/src/pat.rs

@@ -18,12 +18,13 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         self.arena.alloc(self.lower_pat_mut(pattern))
     }
 
-    pub(crate) fn lower_pat_mut(&mut self, mut pattern: &Pat) -> hir::Pat<'hir> {
+    fn lower_pat_mut(&mut self, mut pattern: &Pat) -> hir::Pat<'hir> {
         ensure_sufficient_stack(|| {
             // loop here to avoid recursion
             let node = loop {
                 match &pattern.kind {
                     PatKind::Wild => break hir::PatKind::Wild,
+                    PatKind::Never => break hir::PatKind::Never,
                     PatKind::Ident(binding_mode, ident, sub) => {
                         let lower_sub = |this: &mut Self| sub.as_ref().map(|s| this.lower_pat(s));
                         break self.lower_pat_ident(pattern, *binding_mode, *ident, lower_sub);

compiler/rustc_ast_passes/src/feature_gate.rs

@@ -555,6 +555,7 @@ pub fn check_crate(krate: &ast::Crate, sess: &Session, features: &Features) {
     gate_all!(explicit_tail_calls, "`become` expression is experimental");
     gate_all!(generic_const_items, "generic const items are experimental");
     gate_all!(unnamed_fields, "unnamed fields are not yet fully implemented");
+    gate_all!(never_patterns, "`!` patterns are experimental");
 
     if !visitor.features.negative_bounds {
         for &span in spans.get(&sym::negative_bounds).iter().copied().flatten() {

compiler/rustc_ast_pretty/src/pprust/state.rs

@@ -151,7 +151,7 @@ pub fn print_crate<'a>(
 /// Note: some old proc macros parse pretty-printed output, so changes here can
 /// break old code. For example:
 /// - #63896: `#[allow(unused,` must be printed rather than `#[allow(unused ,`
-/// - #73345: `#[allow(unused)] must be printed rather than `# [allow(unused)]
+/// - #73345: `#[allow(unused)]` must be printed rather than `# [allow(unused)]`
 ///
 fn space_between(tt1: &TokenTree, tt2: &TokenTree) -> bool {
     use token::*;
@@ -1343,6 +1343,7 @@ impl<'a> State<'a> {
         is that it doesn't matter */
         match &pat.kind {
             PatKind::Wild => self.word("_"),
+            PatKind::Never => self.word("!"),
             PatKind::Ident(BindingAnnotation(by_ref, mutbl), ident, sub) => {
                 if *by_ref == ByRef::Yes {
                     self.word_nbsp("ref");

compiler/rustc_ast_pretty/src/pprust/state/expr.rs

@@ -255,12 +255,12 @@ impl<'a> State<'a> {
 
         self.print_expr_maybe_paren(lhs, left_prec);
         self.space();
-        self.word_space(op.node.to_string());
+        self.word_space(op.node.as_str());
         self.print_expr_maybe_paren(rhs, right_prec)
     }
 
     fn print_expr_unary(&mut self, op: ast::UnOp, expr: &ast::Expr) {
-        self.word(ast::UnOp::to_string(op));
+        self.word(op.as_str());
         self.print_expr_maybe_paren(expr, parser::PREC_PREFIX)
     }
 
@@ -470,7 +470,7 @@ impl<'a> State<'a> {
                 let prec = AssocOp::Assign.precedence() as i8;
                 self.print_expr_maybe_paren(lhs, prec + 1);
                 self.space();
-                self.word(op.node.to_string());
+                self.word(op.node.as_str());
                 self.word_space("=");
                 self.print_expr_maybe_paren(rhs, prec);
             }

compiler/rustc_attr/src/builtin.rs

@@ -985,7 +985,7 @@ pub fn parse_repr_attr(sess: &Session, attr: &Attribute) -> Vec<ReprAttr> {
                         Ok(literal) => acc.push(ReprPacked(literal)),
                         Err(message) => literal_error = Some(message),
                     };
-                } else if matches!(name, sym::C | sym::simd | sym::transparent)
+                } else if matches!(name, sym::Rust | sym::C | sym::simd | sym::transparent)
                     || int_type_of_word(name).is_some()
                 {
                     recognised = true;
@@ -1018,7 +1018,7 @@ pub fn parse_repr_attr(sess: &Session, attr: &Attribute) -> Vec<ReprAttr> {
                             });
                         } else if matches!(
                             meta_item.name_or_empty(),
-                            sym::C | sym::simd | sym::transparent
+                            sym::Rust | sym::C | sym::simd | sym::transparent
                         ) || int_type_of_word(meta_item.name_or_empty()).is_some()
                         {
                             recognised = true;
@@ -1043,7 +1043,7 @@ pub fn parse_repr_attr(sess: &Session, attr: &Attribute) -> Vec<ReprAttr> {
                             );
                         } else if matches!(
                             meta_item.name_or_empty(),
-                            sym::C | sym::simd | sym::transparent
+                            sym::Rust | sym::C | sym::simd | sym::transparent
                         ) || int_type_of_word(meta_item.name_or_empty()).is_some()
                         {
                             recognised = true;

compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs

@@ -2352,7 +2352,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                                     Applicability::MaybeIncorrect,
                                 );
                             } else {
-                                err.note("the result of `format_args!` can only be assigned directly if no placeholders in it's arguments are used");
+                                err.note("the result of `format_args!` can only be assigned directly if no placeholders in its arguments are used");
                                 err.note("to learn more, visit <https://doc.rust-lang.org/std/macro.format_args.html>");
                             }
                             suggested = true;

compiler/rustc_borrowck/src/lib.rs

@@ -42,6 +42,7 @@ use rustc_target::abi::FieldIdx;
 use smallvec::SmallVec;
 use std::cell::RefCell;
 use std::collections::BTreeMap;
+use std::marker::PhantomData;
 use std::ops::Deref;
 use std::rc::Rc;
 
@@ -100,7 +101,7 @@ use renumber::RegionCtxt;
 rustc_fluent_macro::fluent_messages! { "../messages.ftl" }
 
 /// Associate some local constants with the `'tcx` lifetime
-struct TyCtxtConsts<'tcx>(TyCtxt<'tcx>);
+struct TyCtxtConsts<'tcx>(PhantomData<&'tcx ()>);
 impl<'tcx> TyCtxtConsts<'tcx> {
     const DEREF_PROJECTION: &'tcx [PlaceElem<'tcx>; 1] = &[ProjectionElem::Deref];
 }

compiler/rustc_builtin_macros/src/format.rs

@@ -672,30 +672,22 @@ fn report_missing_placeholders(
                     if explained.contains(&sub) {
                         continue;
                     }
-                    explained.insert(sub.clone());
+                    explained.insert(sub);
 
                     if !found_foreign {
                         found_foreign = true;
                         show_doc_note = true;
                     }
 
-                    if let Some(inner_sp) = pos {
+                    let sp = fmt_span.from_inner(pos);
-                        let sp = fmt_span.from_inner(inner_sp);
 
-                        if success {
+                    if success {
-                            suggestions.push((sp, trn));
+                        suggestions.push((sp, trn));
-                        } else {
-                            diag.span_note(
-                                sp,
-                                format!("format specifiers use curly braces, and {}", trn),
-                            );
-                        }
                     } else {
-                        if success {
+                        diag.span_note(
-                            diag.help(format!("`{}` should be written as `{}`", sub, trn));
+                            sp,
-                        } else {
+                            format!("format specifiers use curly braces, and {}", trn),
-                            diag.note(format!("`{}` should use curly braces, and {}", sub, trn));
+                        );
-                        }
                     }
                 }
 

compiler/rustc_builtin_macros/src/format_foreign.rs

@@ -19,10 +19,10 @@ pub(crate) mod printf {
             }
         }
 
-        pub fn position(&self) -> Option<InnerSpan> {
+        pub fn position(&self) -> InnerSpan {
             match self {
-                Substitution::Format(fmt) => Some(fmt.position),
+                Substitution::Format(fmt) => fmt.position,
-                &Substitution::Escape((start, end)) => Some(InnerSpan::new(start, end)),
+                &Substitution::Escape((start, end)) => InnerSpan::new(start, end),
             }
         }
 
@@ -302,10 +302,9 @@ pub(crate) mod printf {
         fn next(&mut self) -> Option<Self::Item> {
             let (mut sub, tail) = parse_next_substitution(self.s)?;
             self.s = tail;
-            if let Some(InnerSpan { start, end }) = sub.position() {
+            let InnerSpan { start, end } = sub.position();
-                sub.set_position(start + self.pos, end + self.pos);
+            sub.set_position(start + self.pos, end + self.pos);
-                self.pos += end;
+            self.pos += end;
-            }
             Some(sub)
         }
 
@@ -629,9 +628,9 @@ pub mod shell {
             }
         }
 
-        pub fn position(&self) -> Option<InnerSpan> {
+        pub fn position(&self) -> InnerSpan {
             let (Self::Ordinal(_, pos) | Self::Name(_, pos) | Self::Escape(pos)) = self;
-            Some(InnerSpan::new(pos.0, pos.1))
+            InnerSpan::new(pos.0, pos.1)
         }
 
         pub fn set_position(&mut self, start: usize, end: usize) {
@@ -664,10 +663,9 @@ pub mod shell {
         fn next(&mut self) -> Option<Self::Item> {
             let (mut sub, tail) = parse_next_substitution(self.s)?;
             self.s = tail;
-            if let Some(InnerSpan { start, end }) = sub.position() {
+            let InnerSpan { start, end } = sub.position();
-                sub.set_position(start + self.pos, end + self.pos);
+            sub.set_position(start + self.pos, end + self.pos);
-                self.pos += end;
+            self.pos += end;
-            }
             Some(sub)
         }
 

compiler/rustc_codegen_llvm/src/attributes.rs

@@ -4,7 +4,7 @@ use rustc_codegen_ssa::traits::*;
 use rustc_hir::def_id::DefId;
 use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrFlags;
 use rustc_middle::ty::{self, TyCtxt};
-use rustc_session::config::OptLevel;
+use rustc_session::config::{FunctionReturn, OptLevel};
 use rustc_span::symbol::sym;
 use rustc_target::spec::abi::Abi;
 use rustc_target::spec::{FramePointer, SanitizerSet, StackProbeType, StackProtector};
@@ -118,6 +118,15 @@ pub fn frame_pointer_type_attr<'ll>(cx: &CodegenCx<'ll, '_>) -> Option<&'ll Attr
     Some(llvm::CreateAttrStringValue(cx.llcx, "frame-pointer", attr_value))
 }
 
+fn function_return_attr<'ll>(cx: &CodegenCx<'ll, '_>) -> Option<&'ll Attribute> {
+    let function_return_attr = match cx.sess().opts.unstable_opts.function_return {
+        FunctionReturn::Keep => return None,
+        FunctionReturn::ThunkExtern => AttributeKind::FnRetThunkExtern,
+    };
+
+    Some(function_return_attr.create_attr(cx.llcx))
+}
+
 /// Tell LLVM what instrument function to insert.
 #[inline]
 fn instrument_function_attr<'ll>(cx: &CodegenCx<'ll, '_>) -> SmallVec<[&'ll Attribute; 4]> {
@@ -331,8 +340,9 @@ pub fn from_fn_attrs<'ll, 'tcx>(
         to_add.push(llvm::CreateAttrString(cx.llcx, "use-sample-profile"));
     }
 
-    // FIXME: none of these three functions interact with source level attributes.
+    // FIXME: none of these functions interact with source level attributes.
     to_add.extend(frame_pointer_type_attr(cx));
+    to_add.extend(function_return_attr(cx));
     to_add.extend(instrument_function_attr(cx));
     to_add.extend(nojumptables_attr(cx));
     to_add.extend(probestack_attr(cx));

compiler/rustc_codegen_llvm/src/context.rs

@@ -134,18 +134,6 @@ pub unsafe fn create_module<'ll>(
 
     let mut target_data_layout = sess.target.data_layout.to_string();
     let llvm_version = llvm_util::get_version();
-    if llvm_version < (16, 0, 0) {
-        if sess.target.arch == "s390x" {
-            // LLVM 16 data layout changed to always set 64-bit vector alignment,
-            // which is conditional in earlier LLVM versions.
-            // https://reviews.llvm.org/D131158 for the discussion.
-            target_data_layout = target_data_layout.replace("-v128:64", "");
-        } else if sess.target.arch == "riscv64" {
-            // LLVM 16 introduced this change so as to produce more efficient code.
-            // See https://reviews.llvm.org/D116735 for the discussion.
-            target_data_layout = target_data_layout.replace("-n32:64-", "-n64-");
-        }
-    }
     if llvm_version < (17, 0, 0) {
         if sess.target.arch.starts_with("powerpc") {
             // LLVM 17 specifies function pointer alignment for ppc:

compiler/rustc_codegen_llvm/src/llvm/ffi.rs

@@ -200,6 +200,7 @@ pub enum AttributeKind {
     AllocatedPointer = 38,
     AllocAlign = 39,
     SanitizeSafeStack = 40,
+    FnRetThunkExtern = 41,
 }
 
 /// LLVMIntPredicate

compiler/rustc_codegen_ssa/src/back/link.rs

@@ -44,7 +44,7 @@ use tempfile::Builder as TempFileBuilder;
 use itertools::Itertools;
 use std::cell::OnceCell;
 use std::collections::BTreeSet;
-use std::ffi::OsString;
+use std::ffi::{OsStr, OsString};
 use std::fs::{read, File, OpenOptions};
 use std::io::{BufWriter, Write};
 use std::ops::Deref;
@@ -2527,7 +2527,7 @@ fn add_native_libs_from_crate(
             NativeLibKind::WasmImportModule => {}
             NativeLibKind::LinkArg => {
                 if link_static {
-                    cmd.arg(name);
+                    cmd.linker_arg(OsStr::new(name), verbatim);
                 }
             }
         }

compiler/rustc_codegen_ssa/src/back/linker.rs

@@ -196,6 +196,14 @@ pub trait Linker {
     fn add_no_exec(&mut self) {}
     fn add_as_needed(&mut self) {}
     fn reset_per_library_state(&mut self) {}
+    fn linker_arg(&mut self, arg: &OsStr, verbatim: bool) {
+        self.linker_args(&[arg], verbatim);
+    }
+    fn linker_args(&mut self, args: &[&OsStr], _verbatim: bool) {
+        args.into_iter().for_each(|a| {
+            self.cmd().arg(a);
+        });
+    }
 }
 
 impl dyn Linker + '_ {
@@ -223,38 +231,12 @@ pub struct GccLinker<'a> {
 }
 
 impl<'a> GccLinker<'a> {
-    /// Passes an argument directly to the linker.
+    fn linker_arg(&mut self, arg: impl AsRef<OsStr>) {
-    ///
+        Linker::linker_arg(self, arg.as_ref(), false);
-    /// When the linker is not ld-like such as when using a compiler as a linker, the argument is
-    /// prepended by `-Wl,`.
-    fn linker_arg(&mut self, arg: impl AsRef<OsStr>) -> &mut Self {
-        self.linker_args(&[arg]);
-        self
     }
-
+    fn linker_args(&mut self, args: &[impl AsRef<OsStr>]) {
-    /// Passes a series of arguments directly to the linker.
+        let args_vec: Vec<&OsStr> = args.iter().map(|x| x.as_ref()).collect();
-    ///
+        Linker::linker_args(self, &args_vec, false);
-    /// When the linker is ld-like, the arguments are simply appended to the command. When the
-    /// linker is not ld-like such as when using a compiler as a linker, the arguments are joined by
-    /// commas to form an argument that is then prepended with `-Wl`. In this situation, only a
-    /// single argument is appended to the command to ensure that the order of the arguments is
-    /// preserved by the compiler.
-    fn linker_args(&mut self, args: &[impl AsRef<OsStr>]) -> &mut Self {
-        if self.is_ld {
-            args.into_iter().for_each(|a| {
-                self.cmd.arg(a);
-            });
-        } else {
-            if !args.is_empty() {
-                let mut s = OsString::from("-Wl");
-                for a in args {
-                    s.push(",");
-                    s.push(a);
-                }
-                self.cmd.arg(s);
-            }
-        }
-        self
     }
 
     fn takes_hints(&self) -> bool {
@@ -361,6 +343,30 @@ impl<'a> GccLinker<'a> {
 }
 
 impl<'a> Linker for GccLinker<'a> {
+    /// Passes a series of arguments directly to the linker.
+    ///
+    /// When the linker is ld-like, the arguments are simply appended to the command. When the
+    /// linker is not ld-like such as when using a compiler as a linker, the arguments are joined by
+    /// commas to form an argument that is then prepended with `-Wl`. In this situation, only a
+    /// single argument is appended to the command to ensure that the order of the arguments is
+    /// preserved by the compiler.
+    fn linker_args(&mut self, args: &[&OsStr], verbatim: bool) {
+        if self.is_ld || verbatim {
+            args.into_iter().for_each(|a| {
+                self.cmd.arg(a);
+            });
+        } else {
+            if !args.is_empty() {
+                let mut s = OsString::from("-Wl");
+                for a in args {
+                    s.push(",");
+                    s.push(a);
+                }
+                self.cmd.arg(s);
+            }
+        }
+    }
+
     fn cmd(&mut self) -> &mut Command {
         &mut self.cmd
     }
@@ -531,7 +537,7 @@ impl<'a> Linker for GccLinker<'a> {
             self.linker_arg("-force_load");
             self.linker_arg(&lib);
         } else {
-            self.linker_arg("--whole-archive").cmd.arg(lib);
+            self.linker_args(&[OsString::from("--whole-archive"), lib.into()]);
             self.linker_arg("--no-whole-archive");
         }
     }
@@ -1302,6 +1308,8 @@ impl<'a> Linker for WasmLd<'a> {
     }
 
     fn optimize(&mut self) {
+        // The -O flag is, as of late 2023, only used for merging of strings and debuginfo, and
+        // only differentiates -O0 and -O1. It does not apply to LTO.
         self.cmd.arg(match self.sess.opts.optimize {
             OptLevel::No => "-O0",
             OptLevel::Less => "-O1",
@@ -1354,7 +1362,31 @@ impl<'a> Linker for WasmLd<'a> {
     fn subsystem(&mut self, _subsystem: &str) {}
 
     fn linker_plugin_lto(&mut self) {
-        // Do nothing for now
+        match self.sess.opts.cg.linker_plugin_lto {
+            LinkerPluginLto::Disabled => {
+                // Nothing to do
+            }
+            LinkerPluginLto::LinkerPluginAuto => {
+                self.push_linker_plugin_lto_args();
+            }
+            LinkerPluginLto::LinkerPlugin(_) => {
+                self.push_linker_plugin_lto_args();
+            }
+        }
+    }
+}
+
+impl<'a> WasmLd<'a> {
+    fn push_linker_plugin_lto_args(&mut self) {
+        let opt_level = match self.sess.opts.optimize {
+            config::OptLevel::No => "O0",
+            config::OptLevel::Less => "O1",
+            config::OptLevel::Default => "O2",
+            config::OptLevel::Aggressive => "O3",
+            // wasm-ld only handles integer LTO opt levels. Use O2
+            config::OptLevel::Size | config::OptLevel::SizeMin => "O2",
+        };
+        self.cmd.arg(&format!("--lto-{opt_level}"));
     }
 }
 

compiler/rustc_codegen_ssa/src/lib.rs

@@ -216,6 +216,7 @@ impl CodegenResults {
         sess: &Session,
         rlink_file: &Path,
         codegen_results: &CodegenResults,
+        outputs: &OutputFilenames,
     ) -> Result<usize, io::Error> {
         let mut encoder = FileEncoder::new(rlink_file)?;
         encoder.emit_raw_bytes(RLINK_MAGIC);
@@ -224,10 +225,14 @@ impl CodegenResults {
         encoder.emit_raw_bytes(&RLINK_VERSION.to_be_bytes());
         encoder.emit_str(sess.cfg_version);
         Encodable::encode(codegen_results, &mut encoder);
+        Encodable::encode(outputs, &mut encoder);
         encoder.finish().map_err(|(_path, err)| err)
     }
 
-    pub fn deserialize_rlink(sess: &Session, data: Vec<u8>) -> Result<Self, CodegenErrors> {
+    pub fn deserialize_rlink(
+        sess: &Session,
+        data: Vec<u8>,
+    ) -> Result<(Self, OutputFilenames), CodegenErrors> {
         // The Decodable machinery is not used here because it panics if the input data is invalid
         // and because its internal representation may change.
         if !data.starts_with(RLINK_MAGIC) {
@@ -256,6 +261,7 @@ impl CodegenResults {
         }
 
         let codegen_results = CodegenResults::decode(&mut decoder);
-        Ok(codegen_results)
+        let outputs = OutputFilenames::decode(&mut decoder);
+        Ok((codegen_results, outputs))
     }
 }

compiler/rustc_const_eval/src/interpret/place.rs

@@ -7,12 +7,11 @@ use std::assert_matches::assert_matches;
 use either::{Either, Left, Right};
 
 use rustc_ast::Mutability;
-use rustc_index::IndexSlice;
 use rustc_middle::mir;
 use rustc_middle::ty;
 use rustc_middle::ty::layout::{LayoutOf, TyAndLayout};
 use rustc_middle::ty::Ty;
-use rustc_target::abi::{Abi, Align, FieldIdx, HasDataLayout, Size, FIRST_VARIANT};
+use rustc_target::abi::{Abi, Align, HasDataLayout, Size};
 
 use super::{
     alloc_range, mir_assign_valid_types, AllocId, AllocRef, AllocRefMut, CheckAlignMsg, ImmTy,
@@ -977,34 +976,6 @@ where
         Ok(self.ptr_with_meta_to_mplace(ptr.into(), MemPlaceMeta::Meta(meta), layout))
     }
 
-    /// Writes the aggregate to the destination.
-    #[instrument(skip(self), level = "trace")]
-    pub fn write_aggregate(
-        &mut self,
-        kind: &mir::AggregateKind<'tcx>,
-        operands: &IndexSlice<FieldIdx, mir::Operand<'tcx>>,
-        dest: &PlaceTy<'tcx, M::Provenance>,
-    ) -> InterpResult<'tcx> {
-        self.write_uninit(dest)?;
-        let (variant_index, variant_dest, active_field_index) = match *kind {
-            mir::AggregateKind::Adt(_, variant_index, _, _, active_field_index) => {
-                let variant_dest = self.project_downcast(dest, variant_index)?;
-                (variant_index, variant_dest, active_field_index)
-            }
-            _ => (FIRST_VARIANT, dest.clone(), None),
-        };
-        if active_field_index.is_some() {
-            assert_eq!(operands.len(), 1);
-        }
-        for (field_index, operand) in operands.iter_enumerated() {
-            let field_index = active_field_index.unwrap_or(field_index);
-            let field_dest = self.project_field(&variant_dest, field_index.as_usize())?;
-            let op = self.eval_operand(operand, Some(field_dest.layout))?;
-            self.copy_op(&op, &field_dest, /*allow_transmute*/ false)?;
-        }
-        self.write_discriminant(variant_index, dest)
-    }
-
     pub fn raw_const_to_mplace(
         &self,
         raw: mir::ConstAlloc<'tcx>,

compiler/rustc_const_eval/src/interpret/step.rs

@@ -4,11 +4,12 @@
 
 use either::Either;
 
+use rustc_index::IndexSlice;
 use rustc_middle::mir;
-use rustc_middle::mir::interpret::{InterpResult, Scalar};
 use rustc_middle::ty::layout::LayoutOf;
+use rustc_target::abi::{FieldIdx, FIRST_VARIANT};
 
-use super::{ImmTy, InterpCx, Machine, Projectable};
+use super::{ImmTy, InterpCx, InterpResult, Machine, PlaceTy, Projectable, Scalar};
 use crate::util;
 
 impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
@@ -187,34 +188,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
             }
 
             Repeat(ref operand, _) => {
-                let src = self.eval_operand(operand, None)?;
+                self.write_repeat(operand, &dest)?;
-                assert!(src.layout.is_sized());
-                let dest = self.force_allocation(&dest)?;
-                let length = dest.len(self)?;
-
-                if length == 0 {
-                    // Nothing to copy... but let's still make sure that `dest` as a place is valid.
-                    self.get_place_alloc_mut(&dest)?;
-                } else {
-                    // Write the src to the first element.
-                    let first = self.project_index(&dest, 0)?;
-                    self.copy_op(&src, &first, /*allow_transmute*/ false)?;
-
-                    // This is performance-sensitive code for big static/const arrays! So we
-                    // avoid writing each operand individually and instead just make many copies
-                    // of the first element.
-                    let elem_size = first.layout.size;
-                    let first_ptr = first.ptr();
-                    let rest_ptr = first_ptr.offset(elem_size, self)?;
-                    // No alignment requirement since `copy_op` above already checked it.
-                    self.mem_copy_repeatedly(
-                        first_ptr,
-                        rest_ptr,
-                        elem_size,
-                        length - 1,
-                        /*nonoverlapping:*/ true,
-                    )?;
-                }
             }
 
             Len(place) => {
@@ -307,6 +281,73 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         Ok(())
     }
 
+    /// Writes the aggregate to the destination.
+    #[instrument(skip(self), level = "trace")]
+    fn write_aggregate(
+        &mut self,
+        kind: &mir::AggregateKind<'tcx>,
+        operands: &IndexSlice<FieldIdx, mir::Operand<'tcx>>,
+        dest: &PlaceTy<'tcx, M::Provenance>,
+    ) -> InterpResult<'tcx> {
+        self.write_uninit(dest)?; // make sure all the padding ends up as uninit
+        let (variant_index, variant_dest, active_field_index) = match *kind {
+            mir::AggregateKind::Adt(_, variant_index, _, _, active_field_index) => {
+                let variant_dest = self.project_downcast(dest, variant_index)?;
+                (variant_index, variant_dest, active_field_index)
+            }
+            _ => (FIRST_VARIANT, dest.clone(), None),
+        };
+        if active_field_index.is_some() {
+            assert_eq!(operands.len(), 1);
+        }
+        for (field_index, operand) in operands.iter_enumerated() {
+            let field_index = active_field_index.unwrap_or(field_index);
+            let field_dest = self.project_field(&variant_dest, field_index.as_usize())?;
+            let op = self.eval_operand(operand, Some(field_dest.layout))?;
+            self.copy_op(&op, &field_dest, /*allow_transmute*/ false)?;
+        }
+        self.write_discriminant(variant_index, dest)
+    }
+
+    /// Repeats `operand` into the destination. `dest` must have array type, and that type
+    /// determines how often `operand` is repeated.
+    fn write_repeat(
+        &mut self,
+        operand: &mir::Operand<'tcx>,
+        dest: &PlaceTy<'tcx, M::Provenance>,
+    ) -> InterpResult<'tcx> {
+        let src = self.eval_operand(operand, None)?;
+        assert!(src.layout.is_sized());
+        let dest = self.force_allocation(&dest)?;
+        let length = dest.len(self)?;
+
+        if length == 0 {
+            // Nothing to copy... but let's still make sure that `dest` as a place is valid.
+            self.get_place_alloc_mut(&dest)?;
+        } else {
+            // Write the src to the first element.
+            let first = self.project_index(&dest, 0)?;
+            self.copy_op(&src, &first, /*allow_transmute*/ false)?;
+
+            // This is performance-sensitive code for big static/const arrays! So we
+            // avoid writing each operand individually and instead just make many copies
+            // of the first element.
+            let elem_size = first.layout.size;
+            let first_ptr = first.ptr();
+            let rest_ptr = first_ptr.offset(elem_size, self)?;
+            // No alignment requirement since `copy_op` above already checked it.
+            self.mem_copy_repeatedly(
+                first_ptr,
+                rest_ptr,
+                elem_size,
+                length - 1,
+                /*nonoverlapping:*/ true,
+            )?;
+        }
+
+        Ok(())
+    }
+
     /// Evaluate the given terminator. Will also adjust the stack frame and statement position accordingly.
     fn terminator(&mut self, terminator: &mir::Terminator<'tcx>) -> InterpResult<'tcx> {
         info!("{:?}", terminator.kind);

compiler/rustc_data_structures/src/graph/scc/mod.rs

@@ -492,7 +492,7 @@ where
             let returned_walk =
                 return_value.take().into_iter().map(|walk| (*successor_node, Some(walk)));
 
-            let successor_walk = successors.by_ref().map(|successor_node| {
+            let successor_walk = successors.map(|successor_node| {
                 debug!(?node, ?successor_node);
                 (successor_node, self.inspect_node(successor_node))
             });

compiler/rustc_driver_impl/src/lib.rs

@@ -401,9 +401,7 @@ fn run_compiler(
                         Ok(())
                     })?;
 
-                    // Make sure the `output_filenames` query is run for its side
+                    queries.write_dep_info()?;
-                    // effects of writing the dep-info and reporting errors.
-                    queries.global_ctxt()?.enter(|tcx| tcx.output_filenames(()));
                 } else {
                     let krate = queries.parse()?;
                     pretty::print(
@@ -431,9 +429,7 @@ fn run_compiler(
                 return early_exit();
             }
 
-            // Make sure the `output_filenames` query is run for its side
+            queries.write_dep_info()?;
-            // effects of writing the dep-info and reporting errors.
-            queries.global_ctxt()?.enter(|tcx| tcx.output_filenames(()));
 
             if sess.opts.output_types.contains_key(&OutputType::DepInfo)
                 && sess.opts.output_types.len() == 1
@@ -648,12 +644,11 @@ fn show_md_content_with_pager(content: &str, color: ColorConfig) {
 fn process_rlink(sess: &Session, compiler: &interface::Compiler) {
     assert!(sess.opts.unstable_opts.link_only);
     if let Input::File(file) = &sess.io.input {
-        let outputs = compiler.build_output_filenames(sess, &[]);
         let rlink_data = fs::read(file).unwrap_or_else(|err| {
             sess.emit_fatal(RlinkUnableToRead { err });
         });
-        let codegen_results = match CodegenResults::deserialize_rlink(sess, rlink_data) {
+        let (codegen_results, outputs) = match CodegenResults::deserialize_rlink(sess, rlink_data) {
-            Ok(codegen) => codegen,
+            Ok((codegen, outputs)) => (codegen, outputs),
             Err(err) => {
                 match err {
                     CodegenErrors::WrongFileType => sess.emit_fatal(RLinkWrongFileType),

compiler/rustc_error_codes/src/error_codes.rs

@@ -653,3 +653,4 @@ E0795: include_str!("./error_codes/E0795.md"),
 //  E0721, // `await` keyword
 //  E0723, // unstable feature in `const` context
 //  E0738, // Removed; errored on `#[track_caller] fn`s in `extern "Rust" { ... }`.
+//  E0744, // merged into E0728

compiler/rustc_error_codes/src/error_codes/E0744.md

@@ -1,8 +1,10 @@
+#### Note: this error code is no longer emitted by the compiler.
+
 An unsupported expression was used inside a const context.
 
 Erroneous code example:
 
-```compile_fail,edition2018,E0744
+```ignore (removed error code)
 const _: i32 = {
     async { 0 }.await
 };

compiler/rustc_feature/src/unstable.rs

@@ -50,6 +50,8 @@ macro_rules! declare_features {
             }),+
         ];
 
+        const NUM_FEATURES: usize = UNSTABLE_FEATURES.len();
+
         /// A set of features to be used by later passes.
         #[derive(Clone, Default, Debug)]
         pub struct Features {
@@ -82,8 +84,14 @@ macro_rules! declare_features {
                 self.declared_features.insert(symbol);
             }
 
-            pub fn walk_feature_fields(&self, mut f: impl FnMut(&str, bool)) {
+            /// This is intended for hashing the set of active features.
-                $(f(stringify!($feature), self.$feature);)+
+            ///
+            /// The expectation is that this produces much smaller code than other alternatives.
+            ///
+            /// Note that the total feature count is pretty small, so this is not a huge array.
+            #[inline]
+            pub fn all_features(&self) -> [u8; NUM_FEATURES] {
+                [$(self.$feature as u8),+]
             }
 
             /// Is the given feature explicitly declared, i.e. named in a
@@ -147,7 +155,7 @@ macro_rules! declare_features {
 // was set.
 //
 // Note that the features are grouped into internal/user-facing and then
-// sorted by version inside those groups. This is enforced with tidy.
+// sorted alphabetically inside those groups. This is enforced with tidy.
 //
 // N.B., `tools/tidy/src/features.rs` parses this information directly out of the
 // source, so take care when modifying it.
@@ -512,6 +520,8 @@ declare_features! (
     (unstable, native_link_modifiers_as_needed, "1.53.0", Some(81490), None),
     /// Allow negative trait implementations.
     (unstable, negative_impls, "1.44.0", Some(68318), None),
+    /// Allows the `!` pattern.
+    (incomplete, never_patterns, "CURRENT_RUSTC_VERSION", Some(118155), None),
     /// Allows the `!` type. Does not imply 'exhaustive_patterns' (below) any more.
     (unstable, never_type, "1.13.0", Some(35121), None),
     /// Allows diverging expressions to fall back to `!` rather than `()`.

compiler/rustc_hir/src/hir.rs

@@ -7,8 +7,8 @@ use crate::LangItem;
 use rustc_ast as ast;
 use rustc_ast::util::parser::ExprPrecedence;
 use rustc_ast::{Attribute, FloatTy, IntTy, Label, LitKind, TraitObjectSyntax, UintTy};
-pub use rustc_ast::{BindingAnnotation, BorrowKind, ByRef, ImplPolarity, IsAuto};
+pub use rustc_ast::{BinOp, BinOpKind, BindingAnnotation, BorrowKind, ByRef, CaptureBy};
-pub use rustc_ast::{CaptureBy, Movability, Mutability};
+pub use rustc_ast::{ImplPolarity, IsAuto, Movability, Mutability, UnOp};
 use rustc_ast::{InlineAsmOptions, InlineAsmTemplatePiece};
 use rustc_data_structures::fingerprint::Fingerprint;
 use rustc_data_structures::fx::FxHashMap;
@@ -1002,7 +1002,7 @@ impl<'hir> Pat<'hir> {
 
         use PatKind::*;
         match self.kind {
-            Wild | Lit(_) | Range(..) | Binding(.., None) | Path(_) => true,
+            Wild | Never | Lit(_) | Range(..) | Binding(.., None) | Path(_) => true,
             Box(s) | Ref(s, _) | Binding(.., Some(s)) => s.walk_short_(it),
             Struct(_, fields, _) => fields.iter().all(|field| field.pat.walk_short_(it)),
             TupleStruct(_, s, _) | Tuple(s, _) | Or(s) => s.iter().all(|p| p.walk_short_(it)),
@@ -1029,7 +1029,7 @@ impl<'hir> Pat<'hir> {
 
         use PatKind::*;
         match self.kind {
-            Wild | Lit(_) | Range(..) | Binding(.., None) | Path(_) => {}
+            Wild | Never | Lit(_) | Range(..) | Binding(.., None) | Path(_) => {}
             Box(s) | Ref(s, _) | Binding(.., Some(s)) => s.walk_(it),
             Struct(_, fields, _) => fields.iter().for_each(|field| field.pat.walk_(it)),
             TupleStruct(_, s, _) | Tuple(s, _) | Or(s) => s.iter().for_each(|p| p.walk_(it)),
@@ -1142,6 +1142,9 @@ pub enum PatKind<'hir> {
     /// Invariant: `pats.len() >= 2`.
     Or(&'hir [Pat<'hir>]),
 
+    /// A never pattern `!`.
+    Never,
+
     /// A path pattern for a unit struct/variant or a (maybe-associated) constant.
     Path(QPath<'hir>),
 
@@ -1174,155 +1177,6 @@ pub enum PatKind<'hir> {
     Slice(&'hir [Pat<'hir>], Option<&'hir Pat<'hir>>, &'hir [Pat<'hir>]),
 }
 
-#[derive(Copy, Clone, PartialEq, Debug, HashStable_Generic)]
-pub enum BinOpKind {
-    /// The `+` operator (addition).
-    Add,
-    /// The `-` operator (subtraction).
-    Sub,
-    /// The `*` operator (multiplication).
-    Mul,
-    /// The `/` operator (division).
-    Div,
-    /// The `%` operator (modulus).
-    Rem,
-    /// The `&&` operator (logical and).
-    And,
-    /// The `||` operator (logical or).
-    Or,
-    /// The `^` operator (bitwise xor).
-    BitXor,
-    /// The `&` operator (bitwise and).
-    BitAnd,
-    /// The `|` operator (bitwise or).
-    BitOr,
-    /// The `<<` operator (shift left).
-    Shl,
-    /// The `>>` operator (shift right).
-    Shr,
-    /// The `==` operator (equality).
-    Eq,
-    /// The `<` operator (less than).
-    Lt,
-    /// The `<=` operator (less than or equal to).
-    Le,
-    /// The `!=` operator (not equal to).
-    Ne,
-    /// The `>=` operator (greater than or equal to).
-    Ge,
-    /// The `>` operator (greater than).
-    Gt,
-}
-
-impl BinOpKind {
-    pub fn as_str(self) -> &'static str {
-        match self {
-            BinOpKind::Add => "+",
-            BinOpKind::Sub => "-",
-            BinOpKind::Mul => "*",
-            BinOpKind::Div => "/",
-            BinOpKind::Rem => "%",
-            BinOpKind::And => "&&",
-            BinOpKind::Or => "||",
-            BinOpKind::BitXor => "^",
-            BinOpKind::BitAnd => "&",
-            BinOpKind::BitOr => "|",
-            BinOpKind::Shl => "<<",
-            BinOpKind::Shr => ">>",
-            BinOpKind::Eq => "==",
-            BinOpKind::Lt => "<",
-            BinOpKind::Le => "<=",
-            BinOpKind::Ne => "!=",
-            BinOpKind::Ge => ">=",
-            BinOpKind::Gt => ">",
-        }
-    }
-
-    pub fn is_lazy(self) -> bool {
-        matches!(self, BinOpKind::And | BinOpKind::Or)
-    }
-
-    pub fn is_comparison(self) -> bool {
-        match self {
-            BinOpKind::Eq
-            | BinOpKind::Lt
-            | BinOpKind::Le
-            | BinOpKind::Ne
-            | BinOpKind::Gt
-            | BinOpKind::Ge => true,
-            BinOpKind::And
-            | BinOpKind::Or
-            | BinOpKind::Add
-            | BinOpKind::Sub
-            | BinOpKind::Mul
-            | BinOpKind::Div
-            | BinOpKind::Rem
-            | BinOpKind::BitXor
-            | BinOpKind::BitAnd
-            | BinOpKind::BitOr
-            | BinOpKind::Shl
-            | BinOpKind::Shr => false,
-        }
-    }
-
-    /// Returns `true` if the binary operator takes its arguments by value.
-    pub fn is_by_value(self) -> bool {
-        !self.is_comparison()
-    }
-}
-
-impl Into<ast::BinOpKind> for BinOpKind {
-    fn into(self) -> ast::BinOpKind {
-        match self {
-            BinOpKind::Add => ast::BinOpKind::Add,
-            BinOpKind::Sub => ast::BinOpKind::Sub,
-            BinOpKind::Mul => ast::BinOpKind::Mul,
-            BinOpKind::Div => ast::BinOpKind::Div,
-            BinOpKind::Rem => ast::BinOpKind::Rem,
-            BinOpKind::And => ast::BinOpKind::And,
-            BinOpKind::Or => ast::BinOpKind::Or,
-            BinOpKind::BitXor => ast::BinOpKind::BitXor,
-            BinOpKind::BitAnd => ast::BinOpKind::BitAnd,
-            BinOpKind::BitOr => ast::BinOpKind::BitOr,
-            BinOpKind::Shl => ast::BinOpKind::Shl,
-            BinOpKind::Shr => ast::BinOpKind::Shr,
-            BinOpKind::Eq => ast::BinOpKind::Eq,
-            BinOpKind::Lt => ast::BinOpKind::Lt,
-            BinOpKind::Le => ast::BinOpKind::Le,
-            BinOpKind::Ne => ast::BinOpKind::Ne,
-            BinOpKind::Ge => ast::BinOpKind::Ge,
-            BinOpKind::Gt => ast::BinOpKind::Gt,
-        }
-    }
-}
-
-pub type BinOp = Spanned<BinOpKind>;
-
-#[derive(Copy, Clone, PartialEq, Debug, HashStable_Generic)]
-pub enum UnOp {
-    /// The `*` operator (dereferencing).
-    Deref,
-    /// The `!` operator (logical negation).
-    Not,
-    /// The `-` operator (negation).
-    Neg,
-}
-
-impl UnOp {
-    pub fn as_str(self) -> &'static str {
-        match self {
-            Self::Deref => "*",
-            Self::Not => "!",
-            Self::Neg => "-",
-        }
-    }
-
-    /// Returns `true` if the unary operator takes its argument by value.
-    pub fn is_by_value(self) -> bool {
-        matches!(self, Self::Neg | Self::Not)
-    }
-}
-
 /// A statement.
 #[derive(Debug, Clone, Copy, HashStable_Generic)]
 pub struct Stmt<'hir> {

compiler/rustc_hir/src/intravisit.rs

@@ -660,7 +660,7 @@ pub fn walk_pat<'v, V: Visitor<'v>>(visitor: &mut V, pattern: &'v Pat<'v>) {
             walk_list!(visitor, visit_expr, lower_bound);
             walk_list!(visitor, visit_expr, upper_bound);
         }
-        PatKind::Wild => (),
+        PatKind::Never | PatKind::Wild => (),
         PatKind::Slice(prepatterns, ref slice_pattern, postpatterns) => {
             walk_list!(visitor, visit_pat, prepatterns);
             walk_list!(visitor, visit_pat, slice_pattern);

compiler/rustc_hir_analysis/src/astconv/mod.rs

@@ -26,12 +26,13 @@ use rustc_hir::def::{CtorOf, DefKind, Namespace, Res};
 use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_hir::intravisit::{walk_generics, Visitor as _};
 use rustc_hir::{GenericArg, GenericArgs, OpaqueTyOrigin};
-use rustc_infer::infer::{InferCtxt, InferOk, TyCtxtInferExt};
+use rustc_infer::infer::{InferCtxt, TyCtxtInferExt};
 use rustc_infer::traits::ObligationCause;
 use rustc_middle::middle::stability::AllowUnstable;
 use rustc_middle::ty::GenericParamDefKind;
 use rustc_middle::ty::{
-    self, Const, GenericArgKind, GenericArgsRef, IsSuggestable, Ty, TyCtxt, TypeVisitableExt,
+    self, Const, GenericArgKind, GenericArgsRef, IsSuggestable, ParamEnv, Ty, TyCtxt,
+    TypeVisitableExt,
 };
 use rustc_session::lint::builtin::AMBIGUOUS_ASSOCIATED_ITEMS;
 use rustc_span::edit_distance::find_best_match_for_name;
@@ -39,8 +40,7 @@ use rustc_span::symbol::{kw, Ident, Symbol};
 use rustc_span::{sym, BytePos, Span, DUMMY_SP};
 use rustc_target::spec::abi;
 use rustc_trait_selection::traits::wf::object_region_bounds;
-use rustc_trait_selection::traits::{self, NormalizeExt, ObligationCtxt};
+use rustc_trait_selection::traits::{self, ObligationCtxt};
-use rustc_type_ir::fold::{TypeFoldable, TypeFolder, TypeSuperFoldable};
 
 use std::fmt::Display;
 use std::slice;
@@ -1606,133 +1606,110 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
         // FIXME(inherent_associated_types): Acquiring the ParamEnv this early leads to cycle errors
         // when inside of an ADT (#108491) or where clause.
         let param_env = tcx.param_env(block.owner);
-        let cause = ObligationCause::misc(span, block.owner.def_id);
 
+        let mut universes = if self_ty.has_escaping_bound_vars() {
+            vec![None; self_ty.outer_exclusive_binder().as_usize()]
+        } else {
+            vec![]
+        };
+
+        let (impl_, (assoc_item, def_scope)) =
+            crate::traits::project::with_replaced_escaping_bound_vars(
+                infcx,
+                &mut universes,
+                self_ty,
+                |self_ty| {
+                    self.select_inherent_assoc_type_candidates(
+                        infcx, name, span, self_ty, param_env, candidates,
+                    )
+                },
+            )?;
+
+        self.check_assoc_ty(assoc_item, name, def_scope, block, span);
+
+        // FIXME(fmease): Currently creating throwaway `parent_args` to please
+        // `create_args_for_associated_item`. Modify the latter instead (or sth. similar) to
+        // not require the parent args logic.
+        let parent_args = ty::GenericArgs::identity_for_item(tcx, impl_);
+        let args = self.create_args_for_associated_item(span, assoc_item, segment, parent_args);
+        let args = tcx.mk_args_from_iter(
+            std::iter::once(ty::GenericArg::from(self_ty))
+                .chain(args.into_iter().skip(parent_args.len())),
+        );
+
+        let ty = Ty::new_alias(tcx, ty::Inherent, ty::AliasTy::new(tcx, assoc_item, args));
+
+        Ok(Some((ty, assoc_item)))
+    }
+
+    fn select_inherent_assoc_type_candidates(
+        &self,
+        infcx: &InferCtxt<'tcx>,
+        name: Ident,
+        span: Span,
+        self_ty: Ty<'tcx>,
+        param_env: ParamEnv<'tcx>,
+        candidates: Vec<(DefId, (DefId, DefId))>,
+    ) -> Result<(DefId, (DefId, DefId)), ErrorGuaranteed> {
+        let tcx = self.tcx();
         let mut fulfillment_errors = Vec::new();
-        let mut applicable_candidates: Vec<_> = infcx.probe(|_| {
-            // Regions are not considered during selection.
-            let self_ty = self_ty
-                .fold_with(&mut BoundVarEraser { tcx, universe: infcx.create_next_universe() });
 
-            struct BoundVarEraser<'tcx> {
+        let applicable_candidates: Vec<_> = candidates
-                tcx: TyCtxt<'tcx>,
+            .iter()
-                universe: ty::UniverseIndex,
+            .copied()
-            }
+            .filter(|&(impl_, _)| {
+                infcx.probe(|_| {
+                    let ocx = ObligationCtxt::new(infcx);
+                    let self_ty = ocx.normalize(&ObligationCause::dummy(), param_env, self_ty);
 
-            // FIXME(non_lifetime_binders): Don't assign the same universe to each placeholder.
+                    let impl_args = infcx.fresh_args_for_item(span, impl_);
-            impl<'tcx> TypeFolder<TyCtxt<'tcx>> for BoundVarEraser<'tcx> {
+                    let impl_ty = tcx.type_of(impl_).instantiate(tcx, impl_args);
-                fn interner(&self) -> TyCtxt<'tcx> {
+                    let impl_ty = ocx.normalize(&ObligationCause::dummy(), param_env, impl_ty);
-                    self.tcx
-                }
 
-                fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> {
+                    // Check that the self types can be related.
-                    // FIXME(@lcnr): This is broken, erasing bound regions
+                    if ocx.eq(&ObligationCause::dummy(), param_env, impl_ty, self_ty).is_err() {
-                    // impacts selection as it results in different types.
+                        return false;
-                    if r.is_bound() { self.tcx.lifetimes.re_erased } else { r }
-                }
-
-                fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
-                    match *ty.kind() {
-                        ty::Bound(_, bv) => Ty::new_placeholder(
-                            self.tcx,
-                            ty::PlaceholderType { universe: self.universe, bound: bv },
-                        ),
-                        _ => ty.super_fold_with(self),
                     }
-                }
 
-                fn fold_const(
+                    // Check whether the impl imposes obligations we have to worry about.
-                    &mut self,
+                    let impl_bounds = tcx.predicates_of(impl_).instantiate(tcx, impl_args);
-                    ct: ty::Const<'tcx>,
+                    let impl_bounds =
-                ) -> <TyCtxt<'tcx> as rustc_type_ir::Interner>::Const {
+                        ocx.normalize(&ObligationCause::dummy(), param_env, impl_bounds);
-                    assert!(!ct.ty().has_escaping_bound_vars());
+                    let impl_obligations = traits::predicates_for_generics(
+                        |_, _| ObligationCause::dummy(),
+                        param_env,
+                        impl_bounds,
+                    );
+                    ocx.register_obligations(impl_obligations);
 
-                    match ct.kind() {
+                    let mut errors = ocx.select_where_possible();
-                        ty::ConstKind::Bound(_, bv) => ty::Const::new_placeholder(
+                    if !errors.is_empty() {
-                            self.tcx,
+                        fulfillment_errors.append(&mut errors);
-                            ty::PlaceholderConst { universe: self.universe, bound: bv },
+                        return false;
-                            ct.ty(),
-                        ),
-                        _ => ct.super_fold_with(self),
                     }
-                }
-            }
 
-            let InferOk { value: self_ty, obligations } =
+                    true
-                infcx.at(&cause, param_env).normalize(self_ty);
-
-            candidates
-                .iter()
-                .copied()
-                .filter(|&(impl_, _)| {
-                    infcx.probe(|_| {
-                        let ocx = ObligationCtxt::new(infcx);
-                        ocx.register_obligations(obligations.clone());
-
-                        let impl_args = infcx.fresh_args_for_item(span, impl_);
-                        let impl_ty = tcx.type_of(impl_).instantiate(tcx, impl_args);
-                        let impl_ty = ocx.normalize(&cause, param_env, impl_ty);
-
-                        // Check that the self types can be related.
-                        if ocx.eq(&ObligationCause::dummy(), param_env, impl_ty, self_ty).is_err() {
-                            return false;
-                        }
-
-                        // Check whether the impl imposes obligations we have to worry about.
-                        let impl_bounds = tcx.predicates_of(impl_).instantiate(tcx, impl_args);
-                        let impl_bounds = ocx.normalize(&cause, param_env, impl_bounds);
-                        let impl_obligations = traits::predicates_for_generics(
-                            |_, _| cause.clone(),
-                            param_env,
-                            impl_bounds,
-                        );
-                        ocx.register_obligations(impl_obligations);
-
-                        let mut errors = ocx.select_where_possible();
-                        if !errors.is_empty() {
-                            fulfillment_errors.append(&mut errors);
-                            return false;
-                        }
-
-                        true
-                    })
                 })
-                .collect()
+            })
-        });
+            .collect();
 
-        if applicable_candidates.len() > 1 {
+        match &applicable_candidates[..] {
-            return Err(self.complain_about_ambiguous_inherent_assoc_type(
+            &[] => Err(self.complain_about_inherent_assoc_type_not_found(
+                name,
+                self_ty,
+                candidates,
+                fulfillment_errors,
+                span,
+            )),
+
+            &[applicable_candidate] => Ok(applicable_candidate),
+
+            &[_, ..] => Err(self.complain_about_ambiguous_inherent_assoc_type(
                 name,
                 applicable_candidates.into_iter().map(|(_, (candidate, _))| candidate).collect(),
                 span,
-            ));
+            )),
         }
-
-        if let Some((impl_, (assoc_item, def_scope))) = applicable_candidates.pop() {
-            self.check_assoc_ty(assoc_item, name, def_scope, block, span);
-
-            // FIXME(fmease): Currently creating throwaway `parent_args` to please
-            // `create_args_for_associated_item`. Modify the latter instead (or sth. similar) to
-            // not require the parent args logic.
-            let parent_args = ty::GenericArgs::identity_for_item(tcx, impl_);
-            let args = self.create_args_for_associated_item(span, assoc_item, segment, parent_args);
-            let args = tcx.mk_args_from_iter(
-                std::iter::once(ty::GenericArg::from(self_ty))
-                    .chain(args.into_iter().skip(parent_args.len())),
-            );
-
-            let ty = Ty::new_alias(tcx, ty::Inherent, ty::AliasTy::new(tcx, assoc_item, args));
-
-            return Ok(Some((ty, assoc_item)));
-        }
-
-        Err(self.complain_about_inherent_assoc_type_not_found(
-            name,
-            self_ty,
-            candidates,
-            fulfillment_errors,
-            span,
-        ))
     }
 
     fn lookup_assoc_ty(

compiler/rustc_hir_analysis/src/check/region.rs

@@ -662,6 +662,7 @@ fn resolve_local<'tcx>(
             PatKind::Ref(_, _)
             | PatKind::Binding(hir::BindingAnnotation(hir::ByRef::No, _), ..)
             | PatKind::Wild
+            | PatKind::Never
             | PatKind::Path(_)
             | PatKind::Lit(_)
             | PatKind::Range(_, _, _) => false,

compiler/rustc_hir_pretty/src/lib.rs

@@ -1724,6 +1724,7 @@ impl<'a> State<'a> {
         // is that it doesn't matter
         match pat.kind {
             PatKind::Wild => self.word("_"),
+            PatKind::Never => self.word("!"),
             PatKind::Binding(BindingAnnotation(by_ref, mutbl), _, ident, sub) => {
                 if by_ref == ByRef::Yes {
                     self.word_nbsp("ref");

compiler/rustc_hir_typeck/src/_match.rs

@@ -139,7 +139,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 &cause,
                 Some(arm.body),
                 arm_ty,
-                |err| self.suggest_removing_semicolon_for_coerce(err, expr, arm_ty, prior_arm),
+                |err| {
+                    self.explain_never_type_coerced_to_unit(err, arm, arm_ty, prior_arm, expr);
+                },
                 false,
             );
 
@@ -177,6 +179,38 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         coercion.complete(self)
     }
 
+    fn explain_never_type_coerced_to_unit(
+        &self,
+        err: &mut Diagnostic,
+        arm: &hir::Arm<'tcx>,
+        arm_ty: Ty<'tcx>,
+        prior_arm: Option<(Option<hir::HirId>, Ty<'tcx>, Span)>,
+        expr: &hir::Expr<'tcx>,
+    ) {
+        if let hir::ExprKind::Block(block, _) = arm.body.kind
+            && let Some(expr) = block.expr
+            && let arm_tail_ty = self.node_ty(expr.hir_id)
+            && arm_tail_ty.is_never()
+            && !arm_ty.is_never()
+        {
+            err.span_label(
+                expr.span,
+                format!(
+                    "this expression is of type `!`, but it is coerced to `{arm_ty}` due to its \
+                     surrounding expression",
+                ),
+            );
+            self.suggest_mismatched_types_on_tail(
+                err,
+                expr,
+                arm_ty,
+                prior_arm.map_or(arm_tail_ty, |(_, ty, _)| ty),
+                expr.hir_id,
+            );
+        }
+        self.suggest_removing_semicolon_for_coerce(err, expr, arm_ty, prior_arm)
+    }
+
     fn suggest_removing_semicolon_for_coerce(
         &self,
         diag: &mut Diagnostic,

compiler/rustc_hir_typeck/src/callee.rs

@@ -6,9 +6,8 @@ use crate::errors;
 use rustc_ast::util::parser::PREC_POSTFIX;
 use rustc_errors::{Applicability, Diagnostic, ErrorGuaranteed, StashKey};
 use rustc_hir as hir;
-use rustc_hir::def::{self, CtorKind, DefKind, Namespace, Res};
+use rustc_hir::def::{self, CtorKind, Namespace, Res};
 use rustc_hir::def_id::DefId;
-use rustc_hir::HirId;
 use rustc_hir_analysis::autoderef::Autoderef;
 use rustc_infer::{
     infer,
@@ -373,7 +372,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     ) -> Ty<'tcx> {
         let (fn_sig, def_id) = match *callee_ty.kind() {
             ty::FnDef(def_id, args) => {
-                self.enforce_context_effects(call_expr.hir_id, call_expr.span, def_id, args);
+                self.enforce_context_effects(call_expr.span, def_id, args);
                 let fn_sig = self.tcx.fn_sig(def_id).instantiate(self.tcx, args);
 
                 // Unit testing: function items annotated with
@@ -770,7 +769,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     #[tracing::instrument(level = "debug", skip(self, span))]
     pub(super) fn enforce_context_effects(
         &self,
-        call_expr_hir: HirId,
         span: Span,
         callee_did: DefId,
         callee_args: GenericArgsRef<'tcx>,
@@ -781,38 +779,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let generics = tcx.generics_of(callee_did);
         let Some(host_effect_index) = generics.host_effect_index else { return };
 
-        // if the callee does have the param, we need to equate the param to some const
+        let effect = tcx.expected_const_effect_param_for_body(self.body_id);
-        // value no matter whether the effects feature is enabled in the local crate,
-        // because inference will fail if we don't.
-        let mut host_always_on =
-            !tcx.features().effects || tcx.sess.opts.unstable_opts.unleash_the_miri_inside_of_you;
-
-        // Compute the constness required by the context.
-        let context = tcx.hir().enclosing_body_owner(call_expr_hir);
-        let const_context = tcx.hir().body_const_context(context);
-
-        let kind = tcx.def_kind(context.to_def_id());
-        debug_assert_ne!(kind, DefKind::ConstParam);
-
-        if tcx.has_attr(context.to_def_id(), sym::rustc_do_not_const_check) {
-            trace!("do not const check this context");
-            host_always_on = true;
-        }
-
-        let effect = match const_context {
-            _ if host_always_on => tcx.consts.true_,
-            Some(hir::ConstContext::Static(_) | hir::ConstContext::Const { .. }) => {
-                tcx.consts.false_
-            }
-            Some(hir::ConstContext::ConstFn) => {
-                let host_idx = tcx
-                    .generics_of(context)
-                    .host_effect_index
-                    .expect("ConstContext::Maybe must have host effect param");
-                ty::GenericArgs::identity_for_item(tcx, context).const_at(host_idx)
-            }
-            None => tcx.consts.true_,
-        };
 
         trace!(?effect, ?generics, ?callee_args);
 
@@ -845,7 +812,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             expected,
         );
 
-        self.write_method_call(call_expr.hir_id, method_callee);
+        self.write_method_call_and_enforce_effects(call_expr.hir_id, call_expr.span, method_callee);
         output_type
     }
 }
@@ -895,7 +862,11 @@ impl<'a, 'tcx> DeferredCallResolution<'tcx> {
                 adjustments.extend(autoref);
                 fcx.apply_adjustments(self.callee_expr, adjustments);
 
-                fcx.write_method_call(self.call_expr.hir_id, method_callee);
+                fcx.write_method_call_and_enforce_effects(
+                    self.call_expr.hir_id,
+                    self.call_expr.span,
+                    method_callee,
+                );
             }
             None => {
                 // This can happen if `#![no_core]` is used and the `fn/fn_mut/fn_once`

compiler/rustc_hir_typeck/src/coercion.rs

@@ -1715,6 +1715,7 @@ impl<'tcx, 'exprs, E: AsCoercionSite> CoerceMany<'tcx, 'exprs, E> {
         // label pointing out the cause for the type coercion will be wrong
         // as prior return coercions would not be relevant (#57664).
         let fn_decl = if let (Some(expr), Some(blk_id)) = (expression, blk_id) {
+            fcx.suggest_missing_semicolon(&mut err, expr, expected, false);
             let pointing_at_return_type =
                 fcx.suggest_mismatched_types_on_tail(&mut err, expr, expected, found, blk_id);
             if let (Some(cond_expr), true, false) = (

compiler/rustc_hir_typeck/src/errors.rs

@@ -626,7 +626,7 @@ pub struct SuggestConvertViaMethod<'tcx> {
     pub span: Span,
     #[suggestion_part(code = "")]
     pub borrow_removal_span: Option<Span>,
-    pub sugg: &'static str,
+    pub sugg: String,
     pub expected: Ty<'tcx>,
     pub found: Ty<'tcx>,
 }

compiler/rustc_hir_typeck/src/expr.rs

@@ -663,8 +663,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     coerce.coerce_forced_unit(
                         self,
                         &cause,
-                        |err| {
+                        |mut err| {
-                            self.suggest_mismatched_types_on_tail(err, expr, ty, e_ty, target_id);
+                            self.suggest_missing_semicolon(&mut err, expr, e_ty, false);
+                            self.suggest_mismatched_types_on_tail(
+                                &mut err, expr, ty, e_ty, target_id,
+                            );
                             let error = Some(Sorts(ExpectedFound { expected: ty, found: e_ty }));
                             self.annotate_loop_expected_due_to_inference(err, expr, error);
                             if let Some(val) = ty_kind_suggestion(ty) {
@@ -1312,9 +1315,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             Ok(method) => {
                 // We could add a "consider `foo::<params>`" suggestion here, but I wasn't able to
                 // trigger this codepath causing `structurally_resolve_type` to emit an error.
-
+                self.write_method_call_and_enforce_effects(expr.hir_id, expr.span, method);
-                self.enforce_context_effects(expr.hir_id, expr.span, method.def_id, method.args);
-                self.write_method_call(expr.hir_id, method);
                 Ok(method)
             }
             Err(error) => {

compiler/rustc_hir_typeck/src/expr_use_visitor.rs

@@ -401,12 +401,17 @@ impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx> {
             mc.cat_pattern(discr_place.clone(), pat, |place, pat| {
                 match &pat.kind {
                     PatKind::Binding(.., opt_sub_pat) => {
-                        // If the opt_sub_pat is None, than the binding does not count as
+                        // If the opt_sub_pat is None, then the binding does not count as
                         // a wildcard for the purpose of borrowing discr.
                         if opt_sub_pat.is_none() {
                             needs_to_be_read = true;
                         }
                     }
+                    PatKind::Never => {
+                        // A never pattern reads the value.
+                        // FIXME(never_patterns): does this do what I expect?
+                        needs_to_be_read = true;
+                    }
                     PatKind::Path(qpath) => {
                         // A `Path` pattern is just a name like `Foo`. This is either a
                         // named constant or else it refers to an ADT variant

compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs

@@ -159,7 +159,13 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     }
 
     #[instrument(level = "debug", skip(self))]
-    pub fn write_method_call(&self, hir_id: hir::HirId, method: MethodCallee<'tcx>) {
+    pub fn write_method_call_and_enforce_effects(
+        &self,
+        hir_id: hir::HirId,
+        span: Span,
+        method: MethodCallee<'tcx>,
+    ) {
+        self.enforce_context_effects(span, method.def_id, method.args);
         self.write_resolution(hir_id, Ok((DefKind::AssocFn, method.def_id)));
         self.write_args(hir_id, method.args);
     }

compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs

@@ -282,12 +282,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                                 span: provided_arg.span,
                             });
                         } else {
-                            self.enforce_context_effects(
+                            self.enforce_context_effects(provided_arg.span, def_id, args)
-                                provided_arg.hir_id,
-                                provided_arg.span,
-                                def_id,
-                                args,
-                            )
                         }
                     }
                 } else {

compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs

@@ -72,7 +72,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         blk_id: hir::HirId,
     ) -> bool {
         let expr = expr.peel_drop_temps();
-        self.suggest_missing_semicolon(err, expr, expected, false);
         let mut pointing_at_return_type = false;
         if let hir::ExprKind::Break(..) = expr.kind {
             // `break` type mismatches provide better context for tail `loop` expressions.
@@ -443,12 +442,22 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     expected,
                 )
             });
+
+            let prefix_wrap = |sugg: &str| {
+                if let Some(name) = self.tcx.hir().maybe_get_struct_pattern_shorthand_field(expr) {
+                    format!(": {}{}", name, sugg)
+                } else {
+                    sugg.to_string()
+                }
+            };
+
             // FIXME: This could/should be extended to suggest `as_mut` and `as_deref_mut`,
             // but those checks need to be a bit more delicate and the benefit is diminishing.
             if self.can_eq(self.param_env, found_ty_inner, peeled) && error_tys_equate_as_ref {
+                let sugg = prefix_wrap(".as_ref()");
                 err.subdiagnostic(errors::SuggestConvertViaMethod {
                     span: expr.span.shrink_to_hi(),
-                    sugg: ".as_ref()",
+                    sugg,
                     expected,
                     found,
                     borrow_removal_span,
@@ -459,9 +468,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 && self.can_eq(self.param_env, deref_ty, peeled)
                 && error_tys_equate_as_ref
             {
+                let sugg = prefix_wrap(".as_deref()");
                 err.subdiagnostic(errors::SuggestConvertViaMethod {
                     span: expr.span.shrink_to_hi(),
-                    sugg: ".as_deref()",
+                    sugg,
                     expected,
                     found,
                     borrow_removal_span,
@@ -475,10 +485,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     self.can_eq(self.param_env, found, expected)
                 })
             {
+                let sugg = prefix_wrap(".map(|x| x.as_str())");
                 err.span_suggestion_verbose(
                     expr.span.shrink_to_hi(),
                     fluent::hir_typeck_convert_to_str,
-                    ".map(|x| x.as_str())",
+                    sugg,
                     Applicability::MachineApplicable,
                 );
                 return true;
@@ -629,12 +640,20 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                             err.help("use `Box::pin`");
                         }
                         _ => {
+                            let prefix = if let Some(name) =
+                                self.tcx.hir().maybe_get_struct_pattern_shorthand_field(expr)
+                            {
+                                format!("{}: ", name)
+                            } else {
+                                String::new()
+                            };
+                            let suggestion = vec![
+                                (expr.span.shrink_to_lo(), format!("{prefix}Box::pin(")),
+                                (expr.span.shrink_to_hi(), ")".to_string()),
+                            ];
                             err.multipart_suggestion(
                                 "you need to pin and box this expression",
-                                vec![
+                                suggestion,
-                                    (expr.span.shrink_to_lo(), "Box::pin(".to_string()),
-                                    (expr.span.shrink_to_hi(), ")".to_string()),
-                                ],
                                 Applicability::MaybeIncorrect,
                             );
                         }
@@ -1215,7 +1234,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 span = parent_callsite;
             }
 
-            let sugg = if expr.precedence().order() >= PREC_POSTFIX {
+            let mut sugg = if expr.precedence().order() >= PREC_POSTFIX {
                 vec![(span.shrink_to_hi(), ".into()".to_owned())]
             } else {
                 vec![
@@ -1223,6 +1242,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     (span.shrink_to_hi(), ").into()".to_owned()),
                 ]
             };
+            if let Some(name) = self.tcx.hir().maybe_get_struct_pattern_shorthand_field(expr) {
+                sugg.insert(0, (expr.span.shrink_to_lo(), format!("{}: ", name)));
+            }
             diag.multipart_suggestion(
                 format!("call `Into::into` on this expression to convert `{expr_ty}` into `{expected_ty}`"),
                 sugg,
@@ -1812,6 +1834,12 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 ".expect(\"REASON\")",
             )
         };
+
+        let sugg = match self.tcx.hir().maybe_get_struct_pattern_shorthand_field(expr) {
+            Some(ident) => format!(": {ident}{sugg}"),
+            None => sugg.to_string(),
+        };
+
         err.span_suggestion_verbose(
             expr.span.shrink_to_hi(),
             msg,

compiler/rustc_hir_typeck/src/lib.rs

@@ -438,9 +438,13 @@ fn fatally_break_rust(tcx: TyCtxt<'_>) {
     }
 }
 
+/// `expected` here is the expected number of explicit generic arguments on the trait.
 fn has_expected_num_generic_args(tcx: TyCtxt<'_>, trait_did: DefId, expected: usize) -> bool {
     let generics = tcx.generics_of(trait_did);
-    generics.count() == expected + if generics.has_self { 1 } else { 0 }
+    generics.count()
+        == expected
+            + if generics.has_self { 1 } else { 0 }
+            + if generics.host_effect_index.is_some() { 1 } else { 0 }
 }
 
 pub fn provide(providers: &mut Providers) {

compiler/rustc_hir_typeck/src/mem_categorization.rs

@@ -766,6 +766,7 @@ impl<'a, 'tcx> MemCategorizationContext<'a, 'tcx> {
             | PatKind::Binding(.., None)
             | PatKind::Lit(..)
             | PatKind::Range(..)
+            | PatKind::Never
             | PatKind::Wild => {
                 // always ok
             }

compiler/rustc_hir_typeck/src/op.rs

@@ -291,7 +291,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                             .push(autoref);
                     }
                 }
-                self.write_method_call(expr.hir_id, method);
+                self.write_method_call_and_enforce_effects(expr.hir_id, expr.span, method);
 
                 method.sig.output()
             }
@@ -781,7 +781,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         assert!(op.is_by_value());
         match self.lookup_op_method(operand_ty, None, Op::Unary(op, ex.span), expected) {
             Ok(method) => {
-                self.write_method_call(ex.hir_id, method);
+                self.write_method_call_and_enforce_effects(ex.hir_id, ex.span, method);
                 method.sig.output()
             }
             Err(errors) => {

compiler/rustc_hir_typeck/src/pat.rs

@@ -178,6 +178,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
         let ty = match pat.kind {
             PatKind::Wild => expected,
+            // FIXME(never_patterns): check the type is uninhabited. If that is not possible within
+            // typeck, do that in a later phase.
+            PatKind::Never => expected,
             PatKind::Lit(lt) => self.check_pat_lit(pat.span, lt, expected, ti),
             PatKind::Range(lhs, rhs, _) => self.check_pat_range(pat.span, lhs, rhs, expected, ti),
             PatKind::Binding(ba, var_id, _, sub) => {
@@ -287,9 +290,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             | PatKind::Box(_)
             | PatKind::Range(..)
             | PatKind::Slice(..) => AdjustMode::Peel,
+            // A never pattern behaves somewhat like a literal or unit variant.
+            PatKind::Never => AdjustMode::Peel,
             // String and byte-string literals result in types `&str` and `&[u8]` respectively.
             // All other literals result in non-reference types.
-            // As a result, we allow `if let 0 = &&0 {}` but not `if let "foo" = &&"foo {}`.
+            // As a result, we allow `if let 0 = &&0 {}` but not `if let "foo" = &&"foo" {}`.
             //
             // Call `resolve_vars_if_possible` here for inline const blocks.
             PatKind::Lit(lt) => match self.resolve_vars_if_possible(self.check_expr(lt)).kind() {
@@ -743,6 +748,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         | PatKind::Slice(..) => "binding",
 
                         PatKind::Wild
+                        | PatKind::Never
                         | PatKind::Binding(..)
                         | PatKind::Path(..)
                         | PatKind::Box(..)

compiler/rustc_hir_typeck/src/place_op.rs

@@ -38,7 +38,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             span_bug!(expr.span, "input to deref is not a ref?");
         }
         let ty = self.make_overloaded_place_return_type(method).ty;
-        self.write_method_call(expr.hir_id, method);
+        self.write_method_call_and_enforce_effects(expr.hir_id, expr.span, method);
         Some(ty)
     }
 
@@ -179,7 +179,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 }
                 self.apply_adjustments(base_expr, adjustments);
 
-                self.write_method_call(expr.hir_id, method);
+                self.write_method_call_and_enforce_effects(expr.hir_id, expr.span, method);
 
                 return Some((input_ty, self.make_overloaded_place_return_type(method).ty));
             }
@@ -404,7 +404,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             None => return,
         };
         debug!("convert_place_op_to_mutable: method={:?}", method);
-        self.write_method_call(expr.hir_id, method);
+        self.write_method_call_and_enforce_effects(expr.hir_id, expr.span, method);
 
         let ty::Ref(region, _, hir::Mutability::Mut) = method.sig.inputs()[0].kind() else {
             span_bug!(expr.span, "input to mutable place op is not a mut ref?");

compiler/rustc_index_macros/src/lib.rs

@@ -23,14 +23,14 @@ mod newtype;
 /// The impls provided by default are Clone, Copy, PartialEq, Eq, and Hash.
 ///
 /// Accepted attributes for customization:
-/// - #[derive(HashStable_Generic)]/#[derive(HashStable)]: derives
+/// - `#[derive(HashStable_Generic)]`/`#[derive(HashStable)]`: derives
 ///   `HashStable`, as normal.
-/// - #[encodable]: derives `Encodable`/`Decodable`.
+/// - `#[encodable]`: derives `Encodable`/`Decodable`.
-/// - #[orderable]: derives `PartialOrd`/`Ord`, plus step-related methods.
+/// - `#[orderable]`: derives `PartialOrd`/`Ord`, plus step-related methods.
-/// - #[debug_format = "Foo({})"]: derives `Debug` with particular output.
+/// - `#[debug_format = "Foo({})"]`: derives `Debug` with particular output.
-/// - #[max = 0xFFFF_FFFD]: specifies the max value, which allows niche
+/// - `#[max = 0xFFFF_FFFD]`: specifies the max value, which allows niche
 ///   optimizations. The default max value is 0xFFFF_FF00.
-/// - #[gate_rustc_only]: makes parts of the generated code nightly-only.
+/// - `#[gate_rustc_only]`: makes parts of the generated code nightly-only.
 #[proc_macro]
 #[cfg_attr(
     feature = "nightly",

compiler/rustc_infer/src/infer/at.rs

@@ -448,7 +448,11 @@ impl<'tcx> ToTrace<'tcx> for ty::TraitRef<'tcx> {
     ) -> TypeTrace<'tcx> {
         TypeTrace {
             cause: cause.clone(),
-            values: TraitRefs(ExpectedFound::new(a_is_expected, a, b)),
+            values: PolyTraitRefs(ExpectedFound::new(
+                a_is_expected,
+                ty::Binder::dummy(a),
+                ty::Binder::dummy(b),
+            )),
         }
     }
 }

compiler/rustc_infer/src/infer/error_reporting/mod.rs

@@ -1667,9 +1667,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                             .report(diag);
                         (false, Mismatch::Fixed("signature"))
                     }
-                    ValuePairs::TraitRefs(_) | ValuePairs::PolyTraitRefs(_) => {
+                    ValuePairs::PolyTraitRefs(_) => (false, Mismatch::Fixed("trait")),
-                        (false, Mismatch::Fixed("trait"))
-                    }
                     ValuePairs::Aliases(infer::ExpectedFound { expected, .. }) => {
                         (false, Mismatch::Fixed(self.tcx.def_descr(expected.def_id)))
                     }
@@ -2219,18 +2217,6 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
             infer::Aliases(exp_found) => self.expected_found_str(exp_found),
             infer::ExistentialTraitRef(exp_found) => self.expected_found_str(exp_found),
             infer::ExistentialProjection(exp_found) => self.expected_found_str(exp_found),
-            infer::TraitRefs(exp_found) => {
-                let pretty_exp_found = ty::error::ExpectedFound {
-                    expected: exp_found.expected.print_only_trait_path(),
-                    found: exp_found.found.print_only_trait_path(),
-                };
-                match self.expected_found_str(pretty_exp_found) {
-                    Some((expected, found, _, _)) if expected == found => {
-                        self.expected_found_str(exp_found)
-                    }
-                    ret => ret,
-                }
-            }
             infer::PolyTraitRefs(exp_found) => {
                 let pretty_exp_found = ty::error::ExpectedFound {
                     expected: exp_found.expected.print_only_trait_path(),

compiler/rustc_infer/src/infer/error_reporting/nice_region_error/placeholder_error.rs

@@ -197,11 +197,6 @@ impl<'tcx> NiceRegionError<'_, 'tcx> {
         value_pairs: &ValuePairs<'tcx>,
     ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
         let (expected_args, found_args, trait_def_id) = match value_pairs {
-            ValuePairs::TraitRefs(ExpectedFound { expected, found })
-                if expected.def_id == found.def_id =>
-            {
-                (expected.args, found.args, expected.def_id)
-            }
             ValuePairs::PolyTraitRefs(ExpectedFound { expected, found })
                 if expected.def_id() == found.def_id() =>
             {

compiler/rustc_infer/src/infer/mod.rs

@@ -384,7 +384,6 @@ pub enum ValuePairs<'tcx> {
     Regions(ExpectedFound<ty::Region<'tcx>>),
     Terms(ExpectedFound<ty::Term<'tcx>>),
     Aliases(ExpectedFound<ty::AliasTy<'tcx>>),
-    TraitRefs(ExpectedFound<ty::TraitRef<'tcx>>),
     PolyTraitRefs(ExpectedFound<ty::PolyTraitRef<'tcx>>),
     PolySigs(ExpectedFound<ty::PolyFnSig<'tcx>>),
     ExistentialTraitRef(ExpectedFound<ty::PolyExistentialTraitRef<'tcx>>),

compiler/rustc_infer/src/traits/error_reporting/mod.rs

@@ -101,12 +101,19 @@ pub fn report_object_safety_error<'tcx>(
          to be resolvable dynamically; for more information visit \
          <https://doc.rust-lang.org/reference/items/traits.html#object-safety>",
     );
+
+    // Only provide the help if its a local trait, otherwise it's not actionable.
     if trait_span.is_some() {
         let mut reported_violations: Vec<_> = reported_violations.into_iter().collect();
         reported_violations.sort();
-        for violation in reported_violations {
+
-            // Only provide the help if its a local trait, otherwise it's not actionable.
+        let mut potential_solutions: Vec<_> =
-            violation.solution(&mut err);
+            reported_violations.into_iter().map(|violation| violation.solution()).collect();
+        potential_solutions.sort();
+        // Allows us to skip suggesting that the same item should be moved to another trait multiple times.
+        potential_solutions.dedup();
+        for solution in potential_solutions {
+            solution.add_to(&mut err);
         }
     }
 

compiler/rustc_interface/src/interface.rs

@@ -1,7 +1,7 @@
 use crate::util;
 
 use rustc_ast::token;
-use rustc_ast::{self as ast, LitKind, MetaItemKind};
+use rustc_ast::{LitKind, MetaItemKind};
 use rustc_codegen_ssa::traits::CodegenBackend;
 use rustc_data_structures::defer;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
@@ -15,9 +15,7 @@ use rustc_middle::{bug, ty};
 use rustc_parse::maybe_new_parser_from_source_str;
 use rustc_query_impl::QueryCtxt;
 use rustc_query_system::query::print_query_stack;
-use rustc_session::config::{
+use rustc_session::config::{self, Cfg, CheckCfg, ExpectedValues, Input, OutFileName};
-    self, Cfg, CheckCfg, ExpectedValues, Input, OutFileName, OutputFilenames,
-};
 use rustc_session::filesearch::sysroot_candidates;
 use rustc_session::parse::ParseSess;
 use rustc_session::{lint, CompilerIO, EarlyErrorHandler, Session};
@@ -43,16 +41,6 @@ pub struct Compiler {
     pub(crate) override_queries: Option<fn(&Session, &mut Providers)>,
 }
 
-impl Compiler {
-    pub fn build_output_filenames(
-        &self,
-        sess: &Session,
-        attrs: &[ast::Attribute],
-    ) -> OutputFilenames {
-        util::build_output_filenames(attrs, sess)
-    }
-}
-
 /// Converts strings provided as `--cfg [cfgspec]` into a `Cfg`.
 pub(crate) fn parse_cfg(handler: &EarlyErrorHandler, cfgs: Vec<String>) -> Cfg {
     cfgs.into_iter()

compiler/rustc_interface/src/passes.rs

@@ -39,7 +39,7 @@ use std::any::Any;
 use std::ffi::OsString;
 use std::io::{self, BufWriter, Write};
 use std::path::{Path, PathBuf};
-use std::sync::{Arc, LazyLock};
+use std::sync::LazyLock;
 use std::{env, fs, iter};
 
 pub fn parse<'a>(sess: &'a Session) -> PResult<'a, ast::Crate> {
@@ -553,13 +553,17 @@ fn resolver_for_lowering<'tcx>(
     tcx.arena.alloc(Steal::new((untracked_resolver_for_lowering, Lrc::new(krate))))
 }
 
-fn output_filenames(tcx: TyCtxt<'_>, (): ()) -> Arc<OutputFilenames> {
+pub(crate) fn write_dep_info(tcx: TyCtxt<'_>) {
+    // Make sure name resolution and macro expansion is run for
+    // the side-effect of providing a complete set of all
+    // accessed files and env vars.
+    let _ = tcx.resolver_for_lowering(());
+
     let sess = tcx.sess;
-    let _timer = sess.timer("prepare_outputs");
+    let _timer = sess.timer("write_dep_info");
-    let (_, krate) = &*tcx.resolver_for_lowering(()).borrow();
     let crate_name = tcx.crate_name(LOCAL_CRATE);
 
-    let outputs = util::build_output_filenames(&krate.attrs, sess);
+    let outputs = tcx.output_filenames(());
     let output_paths =
         generated_output_paths(tcx, &outputs, sess.io.output_file.is_some(), crate_name);
 
@@ -596,15 +600,12 @@ fn output_filenames(tcx: TyCtxt<'_>, (): ()) -> Arc<OutputFilenames> {
             }
         }
     }
-
-    outputs.into()
 }
 
 pub static DEFAULT_QUERY_PROVIDERS: LazyLock<Providers> = LazyLock::new(|| {
     let providers = &mut Providers::default();
     providers.analysis = analysis;
     providers.hir_crate = rustc_ast_lowering::lower_to_hir;
-    providers.output_filenames = output_filenames;
     providers.resolver_for_lowering = resolver_for_lowering;
     providers.early_lint_checks = early_lint_checks;
     proc_macro_decls::provide(providers);

compiler/rustc_interface/src/queries.rs

@@ -8,6 +8,7 @@ use rustc_codegen_ssa::CodegenResults;
 use rustc_data_structures::steal::Steal;
 use rustc_data_structures::svh::Svh;
 use rustc_data_structures::sync::{AppendOnlyIndexVec, FreezeLock, OnceLock, WorkerLocal};
+use rustc_hir::def::DefKind;
 use rustc_hir::def_id::{StableCrateId, CRATE_DEF_ID, LOCAL_CRATE};
 use rustc_hir::definitions::Definitions;
 use rustc_incremental::setup_dep_graph;
@@ -85,7 +86,6 @@ pub struct Queries<'tcx> {
     hir_arena: WorkerLocal<rustc_hir::Arena<'tcx>>,
 
     parse: Query<ast::Crate>,
-    pre_configure: Query<(ast::Crate, ast::AttrVec)>,
     // This just points to what's in `gcx_cell`.
     gcx: Query<&'tcx GlobalCtxt<'tcx>>,
 }
@@ -98,7 +98,6 @@ impl<'tcx> Queries<'tcx> {
             arena: WorkerLocal::new(|_| Arena::default()),
             hir_arena: WorkerLocal::new(|_| rustc_hir::Arena::default()),
             parse: Default::default(),
-            pre_configure: Default::default(),
             gcx: Default::default(),
         }
     }
@@ -113,12 +112,12 @@ impl<'tcx> Queries<'tcx> {
         })
     }
 
-    #[deprecated = "pre_configure may be made private in the future. If you need it please open an issue with your use case."]
+    pub fn global_ctxt(&'tcx self) -> Result<QueryResult<'_, &'tcx GlobalCtxt<'tcx>>> {
-    pub fn pre_configure(&self) -> Result<QueryResult<'_, (ast::Crate, ast::AttrVec)>> {
+        self.gcx.compute(|| {
-        self.pre_configure.compute(|| {
+            let sess = &self.compiler.sess;
+
             let mut krate = self.parse()?.steal();
 
-            let sess = &self.compiler.sess;
             rustc_builtin_macros::cmdline_attrs::inject(
                 &mut krate,
                 &sess.parse_sess,
@@ -127,15 +126,6 @@ impl<'tcx> Queries<'tcx> {
 
             let pre_configured_attrs =
                 rustc_expand::config::pre_configure_attrs(sess, &krate.attrs);
-            Ok((krate, pre_configured_attrs))
-        })
-    }
-
-    pub fn global_ctxt(&'tcx self) -> Result<QueryResult<'_, &'tcx GlobalCtxt<'tcx>>> {
-        self.gcx.compute(|| {
-            let sess = &self.compiler.sess;
-            #[allow(deprecated)]
-            let (krate, pre_configured_attrs) = self.pre_configure()?.steal();
 
             // parse `#[crate_name]` even if `--crate-name` was passed, to make sure it matches.
             let crate_name = find_crate_name(sess, &pre_configured_attrs);
@@ -146,6 +136,7 @@ impl<'tcx> Queries<'tcx> {
                 sess.opts.cg.metadata.clone(),
                 sess.cfg_version,
             );
+            let outputs = util::build_output_filenames(&pre_configured_attrs, sess);
             let dep_graph = setup_dep_graph(sess, crate_name, stable_crate_id)?;
 
             let cstore = FreezeLock::new(Box::new(CStore::new(
@@ -180,11 +171,22 @@ impl<'tcx> Queries<'tcx> {
                     crate_name,
                 )));
                 feed.crate_for_resolver(tcx.arena.alloc(Steal::new((krate, pre_configured_attrs))));
+                feed.output_filenames(Arc::new(outputs));
+
+                let feed = tcx.feed_local_def_id(CRATE_DEF_ID);
+                feed.def_kind(DefKind::Mod);
             });
             Ok(qcx)
         })
     }
 
+    pub fn write_dep_info(&'tcx self) -> Result<()> {
+        self.global_ctxt()?.enter(|tcx| {
+            passes::write_dep_info(tcx);
+        });
+        Ok(())
+    }
+
     /// Check for the `#[rustc_error]` annotation, which forces an error in codegen. This is used
     /// to write UI tests that actually test that compilation succeeds without reporting
     /// an error.
@@ -284,8 +286,13 @@ impl Linker {
 
         if sess.opts.unstable_opts.no_link {
             let rlink_file = self.output_filenames.with_extension(config::RLINK_EXT);
-            CodegenResults::serialize_rlink(sess, &rlink_file, &codegen_results)
+            CodegenResults::serialize_rlink(
-                .map_err(|error| sess.emit_fatal(FailedWritingFile { path: &rlink_file, error }))?;
+                sess,
+                &rlink_file,
+                &codegen_results,
+                &*self.output_filenames,
+            )
+            .map_err(|error| sess.emit_fatal(FailedWritingFile { path: &rlink_file, error }))?;
             return Ok(());
         }
 

compiler/rustc_interface/src/tests.rs

@@ -5,10 +5,11 @@ use rustc_errors::{emitter::HumanReadableErrorType, registry, ColorConfig};
 use rustc_session::config::{
     build_configuration, build_session_options, rustc_optgroups, BranchProtection, CFGuard, Cfg,
     DebugInfo, DumpMonoStatsFormat, ErrorOutputType, ExternEntry, ExternLocation, Externs,
-    InliningThreshold, Input, InstrumentCoverage, InstrumentXRay, LinkSelfContained,
+    FunctionReturn, InliningThreshold, Input, InstrumentCoverage, InstrumentXRay,
-    LinkerPluginLto, LocationDetail, LtoCli, MirSpanview, OomStrategy, Options, OutFileName,
+    LinkSelfContained, LinkerPluginLto, LocationDetail, LtoCli, MirSpanview, OomStrategy, Options,
-    OutputType, OutputTypes, PAuthKey, PacRet, Passes, Polonius, ProcMacroExecutionStrategy, Strip,
+    OutFileName, OutputType, OutputTypes, PAuthKey, PacRet, Passes, Polonius,
-    SwitchWithOptPath, SymbolManglingVersion, TraitSolver, WasiExecModel,
+    ProcMacroExecutionStrategy, Strip, SwitchWithOptPath, SymbolManglingVersion, TraitSolver,
+    WasiExecModel,
 };
 use rustc_session::lint::Level;
 use rustc_session::search_paths::SearchPath;
@@ -758,6 +759,7 @@ fn test_unstable_options_tracking_hash() {
     tracked!(flatten_format_args, false);
     tracked!(force_unstable_if_unmarked, true);
     tracked!(fuel, Some(("abc".to_string(), 99)));
+    tracked!(function_return, FunctionReturn::ThunkExtern);
     tracked!(function_sections, Some(false));
     tracked!(human_readable_cgu_names, true);
     tracked!(incremental_ignore_spans, true);

compiler/rustc_interface/src/util.rs

@@ -126,11 +126,8 @@ pub(crate) fn run_in_thread_pool_with_globals<F: FnOnce() -> R + Send, R: Send>(
         .deadlock_handler(|| {
             // On deadlock, creates a new thread and forwards information in thread
             // locals to it. The new thread runs the deadlock handler.
-            let query_map = FromDyn::from(tls::with(|tcx| {
+            let query_map =
-                QueryCtxt::new(tcx)
+                FromDyn::from(tls::with(|tcx| QueryCtxt::new(tcx).collect_active_jobs()));
-                    .try_collect_active_jobs()
-                    .expect("active jobs shouldn't be locked in deadlock handler")
-            }));
             let registry = rayon_core::Registry::current();
             thread::spawn(move || deadlock(query_map.into_inner(), &registry));
         });

compiler/rustc_lint/src/unused.rs

@@ -656,7 +656,7 @@ trait UnusedDelimLint {
     ) -> bool {
         if followed_by_else {
             match inner.kind {
-                ast::ExprKind::Binary(op, ..) if op.node.lazy() => return true,
+                ast::ExprKind::Binary(op, ..) if op.node.is_lazy() => return true,
                 _ if classify::expr_trailing_brace(inner).is_some() => return true,
                 _ => {}
             }
@@ -1016,7 +1016,7 @@ impl UnusedDelimLint for UnusedParens {
                                 rustc_span::source_map::Spanned { node, .. },
                                 _,
                                 _,
-                            ) if node.lazy()))
+                            ) if node.is_lazy()))
                 {
                     self.emit_unused_delims_expr(cx, value, ctx, left_pos, right_pos, is_kw)
                 }
@@ -1154,7 +1154,7 @@ impl EarlyLintPass for UnusedParens {
             // Do not lint on `(..)` as that will result in the other arms being useless.
             Paren(_)
             // The other cases do not contain sub-patterns.
-            | Wild | Rest | Lit(..) | MacCall(..) | Range(..) | Ident(.., None) | Path(..) => {},
+            | Wild | Never | Rest | Lit(..) | MacCall(..) | Range(..) | Ident(.., None) | Path(..) => {},
             // These are list-like patterns; parens can always be removed.
             TupleStruct(_, _, ps) | Tuple(ps) | Slice(ps) | Or(ps) => for p in ps {
                 self.check_unused_parens_pat(cx, p, false, false, keep_space);

compiler/rustc_llvm/llvm-wrapper/LLVMWrapper.h

@@ -42,11 +42,7 @@
 #include "llvm/IR/IRPrintingPasses.h"
 #include "llvm/Linker/Linker.h"
 
-#if LLVM_VERSION_GE(16, 0)
 #include "llvm/TargetParser/Triple.h"
-#else
-#include "llvm/ADT/Triple.h"
-#endif
 
 extern "C" void LLVMRustSetLastError(const char *);
 
@@ -93,6 +89,7 @@ enum LLVMRustAttribute {
   AllocatedPointer = 38,
   AllocAlign = 39,
   SanitizeSafeStack = 40,
+  FnRetThunkExtern = 41,
 };
 
 typedef struct OpaqueRustString *RustStringRef;

compiler/rustc_llvm/llvm-wrapper/PassWrapper.cpp

@@ -204,11 +204,7 @@ enum class LLVMRustCodeModel {
   None,
 };
 
-#if LLVM_VERSION_LT(16, 0)
-static Optional<CodeModel::Model>
-#else
 static std::optional<CodeModel::Model>
-#endif
 fromRust(LLVMRustCodeModel Model) {
   switch (Model) {
   case LLVMRustCodeModel::Tiny:
@@ -222,11 +218,7 @@ fromRust(LLVMRustCodeModel Model) {
   case LLVMRustCodeModel::Large:
     return CodeModel::Large;
   case LLVMRustCodeModel::None:
-#if LLVM_VERSION_LT(16, 0)
-    return None;
-#else
     return std::nullopt;
-#endif
   default:
     report_fatal_error("Bad CodeModel.");
   }
@@ -452,7 +444,6 @@ extern "C" LLVMTargetMachineRef LLVMRustCreateTargetMachine(
   if (OutputObjFile) {
       Options.ObjectFilenameForDebug = OutputObjFile;
   }
-#if LLVM_VERSION_GE(16, 0)
   if (!strcmp("zlib", DebugInfoCompression) && llvm::compression::zlib::isAvailable()) {
     Options.CompressDebugSections = DebugCompressionType::Zlib;
   } else if (!strcmp("zstd", DebugInfoCompression) && llvm::compression::zstd::isAvailable()) {
@@ -460,7 +451,6 @@ extern "C" LLVMTargetMachineRef LLVMRustCreateTargetMachine(
   } else if (!strcmp("none", DebugInfoCompression)) {
     Options.CompressDebugSections = DebugCompressionType::None;
   }
-#endif
 
   Options.RelaxELFRelocations = RelaxELFRelocations;
   Options.UseInitArray = UseInitArray;
@@ -734,22 +724,14 @@ LLVMRustOptimize(
   bool DebugPassManager = false;
 
   PassInstrumentationCallbacks PIC;
-#if LLVM_VERSION_LT(16, 0)
-  StandardInstrumentations SI(DebugPassManager);
-#else
   StandardInstrumentations SI(TheModule->getContext(), DebugPassManager);
-#endif
   SI.registerCallbacks(PIC);
 
   if (LlvmSelfProfiler){
     LLVMSelfProfileInitializeCallbacks(PIC,LlvmSelfProfiler,BeforePassCallback,AfterPassCallback);
   }
 
-#if LLVM_VERSION_LT(16, 0)
-  Optional<PGOOptions> PGOOpt;
-#else
   std::optional<PGOOptions> PGOOpt;
-#endif
 #if LLVM_VERSION_GE(17, 0)
   auto FS = vfs::getRealFileSystem();
 #endif
@@ -882,12 +864,7 @@ LLVMRustOptimize(
           /*EagerChecks=*/true);
       OptimizerLastEPCallbacks.push_back(
         [Options](ModulePassManager &MPM, OptimizationLevel Level) {
-#if LLVM_VERSION_LT(16, 0)
-          MPM.addPass(ModuleMemorySanitizerPass(Options));
-          MPM.addPass(createModuleToFunctionPassAdaptor(MemorySanitizerPass(Options)));
-#else
           MPM.addPass(MemorySanitizerPass(Options));
-#endif
         }
       );
     }
@@ -912,11 +889,7 @@ LLVMRustOptimize(
             /*UseAfterScope=*/true,
             AsanDetectStackUseAfterReturnMode::Runtime,
           };
-#if LLVM_VERSION_LT(16, 0)
-          MPM.addPass(ModuleAddressSanitizerPass(opts));
-#else
           MPM.addPass(AddressSanitizerPass(opts));
-#endif
         }
       );
     }

compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp

@@ -14,18 +14,13 @@
 #include "llvm/Remarks/RemarkSerializer.h"
 #include "llvm/Remarks/RemarkFormat.h"
 #include "llvm/Support/ToolOutputFile.h"
-#if LLVM_VERSION_GE(16, 0)
 #include "llvm/Support/ModRef.h"
-#endif
 #include "llvm/Object/Archive.h"
 #include "llvm/Object/COFFImportFile.h"
 #include "llvm/Object/ObjectFile.h"
 #include "llvm/Pass.h"
 #include "llvm/Bitcode/BitcodeWriter.h"
 #include "llvm/Support/Signals.h"
-#if LLVM_VERSION_LT(16, 0)
-#include "llvm/ADT/Optional.h"
-#endif
 
 #include <iostream>
 
@@ -283,6 +278,8 @@ static Attribute::AttrKind fromRust(LLVMRustAttribute Kind) {
     return Attribute::AllocAlign;
   case SanitizeSafeStack:
     return Attribute::SafeStack;
+  case FnRetThunkExtern:
+    return Attribute::FnRetThunkExtern;
   }
   report_fatal_error("bad AttributeKind");
 }
@@ -347,13 +344,7 @@ extern "C" LLVMAttributeRef LLVMRustCreateUWTableAttr(LLVMContextRef C, bool Asy
 }
 
 extern "C" LLVMAttributeRef LLVMRustCreateAllocSizeAttr(LLVMContextRef C, uint32_t ElementSizeArg) {
-  return wrap(Attribute::getWithAllocSizeArgs(*unwrap(C), ElementSizeArg,
+  return wrap(Attribute::getWithAllocSizeArgs(*unwrap(C), ElementSizeArg, std::nullopt));
-#if LLVM_VERSION_LT(16, 0)
-                                              None
-#else
-                                              std::nullopt
-#endif
-                                              ));
 }
 
 // These values **must** match ffi::AllocKindFlags.
@@ -416,7 +407,6 @@ enum class LLVMRustMemoryEffects {
 
 extern "C" LLVMAttributeRef LLVMRustCreateMemoryEffectsAttr(LLVMContextRef C,
                                                             LLVMRustMemoryEffects Effects) {
-#if LLVM_VERSION_GE(16, 0)
   switch (Effects) {
     case LLVMRustMemoryEffects::None:
       return wrap(Attribute::getWithMemoryEffects(*unwrap(C), MemoryEffects::none()));
@@ -428,18 +418,6 @@ extern "C" LLVMAttributeRef LLVMRustCreateMemoryEffectsAttr(LLVMContextRef C,
     default:
       report_fatal_error("bad MemoryEffects.");
   }
-#else
-  switch (Effects) {
-    case LLVMRustMemoryEffects::None:
-      return wrap(Attribute::get(*unwrap(C), Attribute::ReadNone));
-    case LLVMRustMemoryEffects::ReadOnly:
-      return wrap(Attribute::get(*unwrap(C), Attribute::ReadOnly));
-    case LLVMRustMemoryEffects::InaccessibleMemOnly:
-      return wrap(Attribute::get(*unwrap(C), Attribute::InaccessibleMemOnly));
-    default:
-      report_fatal_error("bad MemoryEffects.");
-  }
-#endif
 }
 
 // Enable a fast-math flag
@@ -726,18 +704,10 @@ enum class LLVMRustChecksumKind {
   SHA256,
 };
 
-#if LLVM_VERSION_LT(16, 0)
-static Optional<DIFile::ChecksumKind> fromRust(LLVMRustChecksumKind Kind) {
-#else
 static std::optional<DIFile::ChecksumKind> fromRust(LLVMRustChecksumKind Kind) {
-#endif
   switch (Kind) {
   case LLVMRustChecksumKind::None:
-#if LLVM_VERSION_LT(16, 0)
-    return None;
-#else
     return std::nullopt;
-#endif
   case LLVMRustChecksumKind::MD5:
     return DIFile::ChecksumKind::CSK_MD5;
   case LLVMRustChecksumKind::SHA1:
@@ -810,17 +780,8 @@ extern "C" LLVMMetadataRef LLVMRustDIBuilderCreateFile(
     const char *Directory, size_t DirectoryLen, LLVMRustChecksumKind CSKind,
     const char *Checksum, size_t ChecksumLen) {
 
-#if LLVM_VERSION_LT(16, 0)
-  Optional<DIFile::ChecksumKind> llvmCSKind = fromRust(CSKind);
-#else
   std::optional<DIFile::ChecksumKind> llvmCSKind = fromRust(CSKind);
-#endif
-
-#if LLVM_VERSION_LT(16, 0)
-  Optional<DIFile::ChecksumInfo<StringRef>> CSInfo{};
-#else
   std::optional<DIFile::ChecksumInfo<StringRef>> CSInfo{};
-#endif
   if (llvmCSKind)
     CSInfo.emplace(*llvmCSKind, StringRef{Checksum, ChecksumLen});
   return wrap(Builder->createFile(StringRef(Filename, FilenameLen),
@@ -2053,17 +2014,9 @@ extern "C" bool LLVMRustIsNonGVFunctionPointerTy(LLVMValueRef V) {
 }
 
 extern "C" bool LLVMRustLLVMHasZlibCompressionForDebugSymbols() {
-#if LLVM_VERSION_GE(16, 0)
   return llvm::compression::zlib::isAvailable();
-#else
-  return false;
-#endif
 }
 
 extern "C" bool LLVMRustLLVMHasZstdCompressionForDebugSymbols() {
-#if LLVM_VERSION_GE(16, 0)
   return llvm::compression::zstd::isAvailable();
-#else
-  return false;
-#endif
 }

compiler/rustc_middle/src/hir/map/mod.rs

@@ -9,7 +9,7 @@ use rustc_data_structures::svh::Svh;
 use rustc_data_structures::sync::{par_for_each_in, try_par_for_each_in, DynSend, DynSync};
 use rustc_hir::def::{DefKind, Res};
 use rustc_hir::def_id::{DefId, LocalDefId, LocalModDefId, LOCAL_CRATE};
-use rustc_hir::definitions::{DefKey, DefPath, DefPathData, DefPathHash};
+use rustc_hir::definitions::{DefKey, DefPath, DefPathHash};
 use rustc_hir::intravisit::{self, Visitor};
 use rustc_hir::*;
 use rustc_index::Idx;
@@ -168,98 +168,6 @@ impl<'hir> Map<'hir> {
         self.tcx.definitions_untracked().def_path_hash(def_id)
     }
 
-    /// Do not call this function directly. The query should be called.
-    pub(super) fn def_kind(self, local_def_id: LocalDefId) -> DefKind {
-        let hir_id = self.tcx.local_def_id_to_hir_id(local_def_id);
-        let node = match self.find(hir_id) {
-            Some(node) => node,
-            None => match self.def_key(local_def_id).disambiguated_data.data {
-                // FIXME: Some anonymous constants produced by `#[rustc_legacy_const_generics]`
-                // do not have corresponding HIR nodes, but they are still anonymous constants.
-                DefPathData::AnonConst => return DefKind::AnonConst,
-                _ => bug!("no HIR node for def id {local_def_id:?}"),
-            },
-        };
-        match node {
-            Node::Item(item) => match item.kind {
-                ItemKind::Static(_, mt, _) => DefKind::Static(mt),
-                ItemKind::Const(..) => DefKind::Const,
-                ItemKind::Fn(..) => DefKind::Fn,
-                ItemKind::Macro(_, macro_kind) => DefKind::Macro(macro_kind),
-                ItemKind::Mod(..) => DefKind::Mod,
-                ItemKind::OpaqueTy(..) => DefKind::OpaqueTy,
-                ItemKind::TyAlias(..) => DefKind::TyAlias,
-                ItemKind::Enum(..) => DefKind::Enum,
-                ItemKind::Struct(..) => DefKind::Struct,
-                ItemKind::Union(..) => DefKind::Union,
-                ItemKind::Trait(..) => DefKind::Trait,
-                ItemKind::TraitAlias(..) => DefKind::TraitAlias,
-                ItemKind::ExternCrate(_) => DefKind::ExternCrate,
-                ItemKind::Use(..) => DefKind::Use,
-                ItemKind::ForeignMod { .. } => DefKind::ForeignMod,
-                ItemKind::GlobalAsm(..) => DefKind::GlobalAsm,
-                ItemKind::Impl(impl_) => DefKind::Impl { of_trait: impl_.of_trait.is_some() },
-            },
-            Node::ForeignItem(item) => match item.kind {
-                ForeignItemKind::Fn(..) => DefKind::Fn,
-                ForeignItemKind::Static(_, mt) => DefKind::Static(mt),
-                ForeignItemKind::Type => DefKind::ForeignTy,
-            },
-            Node::TraitItem(item) => match item.kind {
-                TraitItemKind::Const(..) => DefKind::AssocConst,
-                TraitItemKind::Fn(..) => DefKind::AssocFn,
-                TraitItemKind::Type(..) => DefKind::AssocTy,
-            },
-            Node::ImplItem(item) => match item.kind {
-                ImplItemKind::Const(..) => DefKind::AssocConst,
-                ImplItemKind::Fn(..) => DefKind::AssocFn,
-                ImplItemKind::Type(..) => DefKind::AssocTy,
-            },
-            Node::Variant(_) => DefKind::Variant,
-            Node::Ctor(variant_data) => {
-                let ctor_of = match self.find_parent(hir_id) {
-                    Some(Node::Item(..)) => def::CtorOf::Struct,
-                    Some(Node::Variant(..)) => def::CtorOf::Variant,
-                    _ => unreachable!(),
-                };
-                match variant_data.ctor_kind() {
-                    Some(kind) => DefKind::Ctor(ctor_of, kind),
-                    None => bug!("constructor node without a constructor"),
-                }
-            }
-            Node::AnonConst(_) => DefKind::AnonConst,
-            Node::ConstBlock(_) => DefKind::InlineConst,
-            Node::Field(_) => DefKind::Field,
-            Node::Expr(expr) => match expr.kind {
-                ExprKind::Closure(_) => DefKind::Closure,
-                _ => bug!("def_kind: unsupported node: {}", self.node_to_string(hir_id)),
-            },
-            Node::GenericParam(param) => match param.kind {
-                GenericParamKind::Lifetime { .. } => DefKind::LifetimeParam,
-                GenericParamKind::Type { .. } => DefKind::TyParam,
-                GenericParamKind::Const { .. } => DefKind::ConstParam,
-            },
-            Node::Crate(_) => DefKind::Mod,
-            Node::Stmt(_)
-            | Node::PathSegment(_)
-            | Node::Ty(_)
-            | Node::TypeBinding(_)
-            | Node::Infer(_)
-            | Node::TraitRef(_)
-            | Node::Pat(_)
-            | Node::PatField(_)
-            | Node::ExprField(_)
-            | Node::Local(_)
-            | Node::Param(_)
-            | Node::Arm(_)
-            | Node::Lifetime(_)
-            | Node::Block(_) => span_bug!(
-                self.span(hir_id),
-                "unexpected node with def id {local_def_id:?}: {node:?}"
-            ),
-        }
-    }
-
     /// Finds the id of the parent node to this one.
     ///
     /// If calling repeatedly and iterating over parents, prefer [`Map::parent_iter`].

compiler/rustc_middle/src/hir/mod.rs

@@ -202,7 +202,6 @@ pub fn provide(providers: &mut Providers) {
             span_bug!(hir.span(hir_id), "fn_arg_names: unexpected item {:?}", def_id);
         }
     };
-    providers.def_kind = |tcx, def_id| tcx.hir().def_kind(def_id);
     providers.all_local_trait_impls = |tcx, ()| &tcx.resolutions(()).trait_impls;
     providers.expn_that_defined =
         |tcx, id| tcx.resolutions(()).expn_that_defined.get(&id).copied().unwrap_or(ExpnId::root());

compiler/rustc_middle/src/mir/query.rs

@@ -27,7 +27,7 @@ pub enum UnsafetyViolationKind {
     UnsafeFn,
 }
 
-#[derive(Copy, Clone, PartialEq, TyEncodable, TyDecodable, HashStable, Debug)]
+#[derive(Clone, PartialEq, TyEncodable, TyDecodable, HashStable, Debug)]
 pub enum UnsafetyViolationDetails {
     CallToUnsafeFunction,
     UseOfInlineAssembly,
@@ -39,10 +39,17 @@ pub enum UnsafetyViolationDetails {
     AccessToUnionField,
     MutationOfLayoutConstrainedField,
     BorrowOfLayoutConstrainedField,
-    CallToFunctionWith,
+    CallToFunctionWith {
+        /// Target features enabled in callee's `#[target_feature]` but missing in
+        /// caller's `#[target_feature]`.
+        missing: Vec<Symbol>,
+        /// Target features in `missing` that are enabled at compile time
+        /// (e.g., with `-C target-feature`).
+        build_enabled: Vec<Symbol>,
+    },
 }
 
-#[derive(Copy, Clone, PartialEq, TyEncodable, TyDecodable, HashStable, Debug)]
+#[derive(Clone, PartialEq, TyEncodable, TyDecodable, HashStable, Debug)]
 pub struct UnsafetyViolation {
     pub source_info: SourceInfo,
     pub lint_root: hir::HirId,

compiler/rustc_middle/src/thir.rs

@@ -635,7 +635,12 @@ impl<'tcx> Pat<'tcx> {
 
         use PatKind::*;
         match &self.kind {
-            Wild | Range(..) | Binding { subpattern: None, .. } | Constant { .. } | Error(_) => {}
+            Wild
+            | Never
+            | Range(..)
+            | Binding { subpattern: None, .. }
+            | Constant { .. }
+            | Error(_) => {}
             AscribeUserType { subpattern, .. }
             | Binding { subpattern: Some(subpattern), .. }
             | Deref { subpattern }
@@ -809,6 +814,9 @@ pub enum PatKind<'tcx> {
         pats: Box<[Box<Pat<'tcx>>]>,
     },
 
+    /// A never pattern `!`.
+    Never,
+
     /// An error has been encountered during lowering. We probably shouldn't report more lints
     /// related to this pattern.
     Error(ErrorGuaranteed),
@@ -1069,6 +1077,7 @@ impl<'tcx> fmt::Display for Pat<'tcx> {
 
         match self.kind {
             PatKind::Wild => write!(f, "_"),
+            PatKind::Never => write!(f, "!"),
             PatKind::AscribeUserType { ref subpattern, .. } => write!(f, "{subpattern}: _"),
             PatKind::Binding { mutability, name, mode, ref subpattern, .. } => {
                 let is_mut = match mode {

compiler/rustc_middle/src/thir/visit.rs

@@ -227,7 +227,7 @@ pub fn walk_pat<'a, 'tcx: 'a, V: Visitor<'a, 'tcx>>(visitor: &mut V, pat: &Pat<'
             is_primary: _,
             name: _,
         } => visitor.visit_pat(subpattern),
-        Binding { .. } | Wild | Error(_) => {}
+        Binding { .. } | Wild | Never | Error(_) => {}
         Variant { subpatterns, adt_def: _, args: _, variant_index: _ } | Leaf { subpatterns } => {
             for subpattern in subpatterns {
                 visitor.visit_pat(&subpattern.pattern);

compiler/rustc_middle/src/traits/mod.rs

@@ -832,50 +832,31 @@ impl ObjectSafetyViolation {
         }
     }
 
-    pub fn solution(&self, err: &mut Diagnostic) {
+    pub fn solution(&self) -> ObjectSafetyViolationSolution {
         match self {
             ObjectSafetyViolation::SizedSelf(_)
             | ObjectSafetyViolation::SupertraitSelf(_)
-            | ObjectSafetyViolation::SupertraitNonLifetimeBinder(..) => {}
+            | ObjectSafetyViolation::SupertraitNonLifetimeBinder(..) => {
+                ObjectSafetyViolationSolution::None
+            }
             ObjectSafetyViolation::Method(
                 name,
                 MethodViolationCode::StaticMethod(Some((add_self_sugg, make_sized_sugg))),
                 _,
-            ) => {
+            ) => ObjectSafetyViolationSolution::AddSelfOrMakeSized {
-                err.span_suggestion(
+                name: *name,
-                    add_self_sugg.1,
+                add_self_sugg: add_self_sugg.clone(),
-                    format!(
+                make_sized_sugg: make_sized_sugg.clone(),
-                        "consider turning `{name}` into a method by giving it a `&self` argument"
+            },
-                    ),
-                    add_self_sugg.0.to_string(),
-                    Applicability::MaybeIncorrect,
-                );
-                err.span_suggestion(
-                    make_sized_sugg.1,
-                    format!(
-                        "alternatively, consider constraining `{name}` so it does not apply to \
-                             trait objects"
-                    ),
-                    make_sized_sugg.0.to_string(),
-                    Applicability::MaybeIncorrect,
-                );
-            }
             ObjectSafetyViolation::Method(
                 name,
                 MethodViolationCode::UndispatchableReceiver(Some(span)),
                 _,
-            ) => {
+            ) => ObjectSafetyViolationSolution::ChangeToRefSelf(*name, *span),
-                err.span_suggestion(
-                    *span,
-                    format!("consider changing method `{name}`'s `self` parameter to be `&self`"),
-                    "&Self",
-                    Applicability::MachineApplicable,
-                );
-            }
             ObjectSafetyViolation::AssocConst(name, _)
             | ObjectSafetyViolation::GAT(name, _)
             | ObjectSafetyViolation::Method(name, ..) => {
-                err.help(format!("consider moving `{name}` to another trait"));
+                ObjectSafetyViolationSolution::MoveToAnotherTrait(*name)
             }
         }
     }
@@ -899,6 +880,60 @@ impl ObjectSafetyViolation {
     }
 }
 
+#[derive(Clone, Debug, PartialEq, Eq, Hash, PartialOrd, Ord)]
+pub enum ObjectSafetyViolationSolution {
+    None,
+    AddSelfOrMakeSized {
+        name: Symbol,
+        add_self_sugg: (String, Span),
+        make_sized_sugg: (String, Span),
+    },
+    ChangeToRefSelf(Symbol, Span),
+    MoveToAnotherTrait(Symbol),
+}
+
+impl ObjectSafetyViolationSolution {
+    pub fn add_to(self, err: &mut Diagnostic) {
+        match self {
+            ObjectSafetyViolationSolution::None => {}
+            ObjectSafetyViolationSolution::AddSelfOrMakeSized {
+                name,
+                add_self_sugg,
+                make_sized_sugg,
+            } => {
+                err.span_suggestion(
+                    add_self_sugg.1,
+                    format!(
+                        "consider turning `{name}` into a method by giving it a `&self` argument"
+                    ),
+                    add_self_sugg.0,
+                    Applicability::MaybeIncorrect,
+                );
+                err.span_suggestion(
+                    make_sized_sugg.1,
+                    format!(
+                        "alternatively, consider constraining `{name}` so it does not apply to \
+                             trait objects"
+                    ),
+                    make_sized_sugg.0,
+                    Applicability::MaybeIncorrect,
+                );
+            }
+            ObjectSafetyViolationSolution::ChangeToRefSelf(name, span) => {
+                err.span_suggestion(
+                    span,
+                    format!("consider changing method `{name}`'s `self` parameter to be `&self`"),
+                    "&Self",
+                    Applicability::MachineApplicable,
+                );
+            }
+            ObjectSafetyViolationSolution::MoveToAnotherTrait(name) => {
+                err.help(format!("consider moving `{name}` to another trait"));
+            }
+        }
+    }
+}
+
 /// Reasons a method might not be object-safe.
 #[derive(Clone, Debug, PartialEq, Eq, Hash, HashStable, PartialOrd, Ord)]
 pub enum MethodViolationCode {

compiler/rustc_middle/src/ty/context.rs

@@ -501,6 +501,9 @@ impl<'tcx> TyCtxt<'tcx> {
     pub fn feed_local_crate(self) -> TyCtxtFeed<'tcx, CrateNum> {
         TyCtxtFeed { tcx: self, key: LOCAL_CRATE }
     }
+    pub fn feed_local_def_id(self, key: LocalDefId) -> TyCtxtFeed<'tcx, LocalDefId> {
+        TyCtxtFeed { tcx: self, key }
+    }
 
     /// In order to break cycles involving `AnonConst`, we need to set the expected type by side
     /// effect. However, we do not want this as a general capability, so this interface restricts
@@ -973,6 +976,7 @@ impl<'tcx> TyCtxtAt<'tcx> {
         self,
         parent: LocalDefId,
         data: hir::definitions::DefPathData,
+        def_kind: DefKind,
     ) -> TyCtxtFeed<'tcx, LocalDefId> {
         // This function modifies `self.definitions` using a side-effect.
         // We need to ensure that these side effects are re-run by the incr. comp. engine.
@@ -997,6 +1001,7 @@ impl<'tcx> TyCtxtAt<'tcx> {
         let key = self.untracked.definitions.write().create_def(parent, data);
 
         let feed = TyCtxtFeed { tcx: self.tcx, key };
+        feed.def_kind(def_kind);
         feed.def_span(self.span);
         feed
     }

compiler/rustc_middle/src/ty/mod.rs

@@ -202,9 +202,6 @@ pub struct ResolverAstLowering {
     pub def_id_to_node_id: IndexVec<LocalDefId, ast::NodeId>,
 
     pub trait_map: NodeMap<Vec<hir::TraitCandidate>>,
-    /// A small map keeping true kinds of built-in macros that appear to be fn-like on
-    /// the surface (`macro` items in libcore), but are actually attributes or derives.
-    pub builtin_macro_kinds: FxHashMap<LocalDefId, MacroKind>,
     /// List functions and methods for which lifetime elision was successful.
     pub lifetime_elision_allowed: FxHashSet<ast::NodeId>,
 

compiler/rustc_middle/src/ty/print/pretty.rs

@@ -283,7 +283,7 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
     /// from at least one local module, and returns `true`. If the crate defining `def_id` is
     /// declared with an `extern crate`, the path is guaranteed to use the `extern crate`.
     fn try_print_visible_def_path(&mut self, def_id: DefId) -> Result<bool, PrintError> {
-        if NO_VISIBLE_PATH.with(|flag| flag.get()) {
+        if with_no_visible_paths() {
             return Ok(false);
         }
 
@@ -367,7 +367,7 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
 
     /// Try to see if this path can be trimmed to a unique symbol name.
     fn try_print_trimmed_def_path(&mut self, def_id: DefId) -> Result<bool, PrintError> {
-        if FORCE_TRIMMED_PATH.with(|flag| flag.get()) {
+        if with_forced_trimmed_paths() {
             let trimmed = self.force_print_trimmed_def_path(def_id)?;
             if trimmed {
                 return Ok(true);
@@ -375,8 +375,8 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
         }
         if !self.tcx().sess.opts.unstable_opts.trim_diagnostic_paths
             || matches!(self.tcx().sess.opts.trimmed_def_paths, TrimmedDefPaths::Never)
-            || NO_TRIMMED_PATH.with(|flag| flag.get())
+            || with_no_trimmed_paths()
-            || SHOULD_PREFIX_WITH_CRATE.with(|flag| flag.get())
+            || with_crate_prefix()
         {
             return Ok(false);
         }
@@ -861,7 +861,7 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
                             p!("@", print_def_path(did.to_def_id(), args));
                         } else {
                             let span = self.tcx().def_span(did);
-                            let preference = if FORCE_TRIMMED_PATH.with(|flag| flag.get()) {
+                            let preference = if with_forced_trimmed_paths() {
                                 FileNameDisplayPreference::Short
                             } else {
                                 FileNameDisplayPreference::Remapped
@@ -1102,7 +1102,7 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
             write!(self, "Sized")?;
         }
 
-        if !FORCE_TRIMMED_PATH.with(|flag| flag.get()) {
+        if !with_forced_trimmed_paths() {
             for re in lifetimes {
                 write!(self, " + ")?;
                 self.print_region(re)?;
@@ -1886,7 +1886,7 @@ impl<'tcx> Printer<'tcx> for FmtPrinter<'_, 'tcx> {
             // available, and filename/line-number is mostly uninteresting.
             let use_types = !def_id.is_local() || {
                 // Otherwise, use filename/line-number if forced.
-                let force_no_types = FORCE_IMPL_FILENAME_LINE.with(|f| f.get());
+                let force_no_types = with_forced_impl_filename_line();
                 !force_no_types
             };
 
@@ -1951,7 +1951,7 @@ impl<'tcx> Printer<'tcx> for FmtPrinter<'_, 'tcx> {
         if cnum == LOCAL_CRATE {
             if self.tcx.sess.at_least_rust_2018() {
                 // We add the `crate::` keyword on Rust 2018, only when desired.
-                if SHOULD_PREFIX_WITH_CRATE.with(|flag| flag.get()) {
+                if with_crate_prefix() {
                     write!(self, "{}", kw::Crate)?;
                     self.empty_path = false;
                 }
@@ -2154,7 +2154,7 @@ impl<'tcx> PrettyPrinter<'tcx> for FmtPrinter<'_, 'tcx> {
             return true;
         }
 
-        if FORCE_TRIMMED_PATH.with(|flag| flag.get()) {
+        if with_forced_trimmed_paths() {
             return false;
         }
 
@@ -2437,7 +2437,7 @@ impl<'tcx> FmtPrinter<'_, 'tcx> {
         } else {
             let tcx = self.tcx;
 
-            let trim_path = FORCE_TRIMMED_PATH.with(|flag| flag.get());
+            let trim_path = with_forced_trimmed_paths();
             // Closure used in `RegionFolder` to create names for anonymous late-bound
             // regions. We use two `DebruijnIndex`es (one for the currently folded
             // late-bound region and the other for the binder level) to determine

compiler/rustc_middle/src/ty/util.rs

@@ -779,6 +779,57 @@ impl<'tcx> TyCtxt<'tcx> {
             // the language.
             || self.extern_crate(key.as_def_id()).is_some_and(|e| e.is_direct())
     }
+
+    pub fn expected_const_effect_param_for_body(self, def_id: LocalDefId) -> ty::Const<'tcx> {
+        // if the callee does have the param, we need to equate the param to some const
+        // value no matter whether the effects feature is enabled in the local crate,
+        // because inference will fail if we don't.
+        let mut host_always_on =
+            !self.features().effects || self.sess.opts.unstable_opts.unleash_the_miri_inside_of_you;
+
+        // Compute the constness required by the context.
+        let const_context = self.hir().body_const_context(def_id);
+
+        let kind = self.def_kind(def_id);
+        debug_assert_ne!(kind, DefKind::ConstParam);
+
+        if self.has_attr(def_id, sym::rustc_do_not_const_check) {
+            trace!("do not const check this context");
+            host_always_on = true;
+        }
+
+        match const_context {
+            _ if host_always_on => self.consts.true_,
+            Some(hir::ConstContext::Static(_) | hir::ConstContext::Const { .. }) => {
+                self.consts.false_
+            }
+            Some(hir::ConstContext::ConstFn) => {
+                let host_idx = self
+                    .generics_of(def_id)
+                    .host_effect_index
+                    .expect("ConstContext::Maybe must have host effect param");
+                ty::GenericArgs::identity_for_item(self, def_id).const_at(host_idx)
+            }
+            None => self.consts.true_,
+        }
+    }
+
+    /// Constructs generic args for an item, optionally appending a const effect param type
+    pub fn with_opt_const_effect_param(
+        self,
+        caller_def_id: LocalDefId,
+        callee_def_id: DefId,
+        args: impl IntoIterator<Item: Into<ty::GenericArg<'tcx>>>,
+    ) -> ty::GenericArgsRef<'tcx> {
+        let generics = self.generics_of(callee_def_id);
+        assert_eq!(generics.parent, None);
+
+        let opt_const_param = generics.host_effect_index.is_some().then(|| {
+            ty::GenericArg::from(self.expected_const_effect_param_for_body(caller_def_id))
+        });
+
+        self.mk_args_from_iter(args.into_iter().map(|arg| arg.into()).chain(opt_const_param))
+    }
 }
 
 struct OpaqueTypeExpander<'tcx> {

compiler/rustc_mir_build/messages.ftl

@@ -30,12 +30,32 @@ mir_build_borrow_of_moved_value = borrow of moved value
 
 mir_build_call_to_fn_with_requires_unsafe =
     call to function `{$function}` with `#[target_feature]` is unsafe and requires unsafe block
-    .note = can only be called if the required target features are available
+    .help = in order for the call to be safe, the context requires the following additional target {$missing_target_features_count ->
+        [1] feature
+        *[count] features
+        }: {$missing_target_features}
+    .note = the {$build_target_features} target {$build_target_features_count ->
+        [1] feature
+        *[count] features
+        } being enabled in the build configuration does not remove the requirement to list {$build_target_features_count ->
+        [1] it
+        *[count] them
+        } in `#[target_feature]`
     .label = call to function with `#[target_feature]`
 
 mir_build_call_to_fn_with_requires_unsafe_unsafe_op_in_unsafe_fn_allowed =
     call to function `{$function}` with `#[target_feature]` is unsafe and requires unsafe function or block
-    .note = can only be called if the required target features are available
+    .help = in order for the call to be safe, the context requires the following additional target {$missing_target_features_count ->
+        [1] feature
+        *[count] features
+        }: {$missing_target_features}
+    .note = the {$build_target_features} target {$build_target_features_count ->
+        [1] feature
+        *[count] features
+        } being enabled in the build configuration does not remove the requirement to list {$build_target_features_count ->
+        [1] it
+        *[count] them
+        } in `#[target_feature]`
     .label = call to function with `#[target_feature]`
 
 mir_build_call_to_unsafe_fn_requires_unsafe =
@@ -330,7 +350,17 @@ mir_build_unsafe_op_in_unsafe_fn_borrow_of_layout_constrained_field_requires_uns
 
 mir_build_unsafe_op_in_unsafe_fn_call_to_fn_with_requires_unsafe =
     call to function `{$function}` with `#[target_feature]` is unsafe and requires unsafe block (error E0133)
-    .note = can only be called if the required target features are available
+    .help = in order for the call to be safe, the context requires the following additional target {$missing_target_features_count ->
+        [1] feature
+        *[count] features
+        }: {$missing_target_features}
+    .note = the {$build_target_features} target {$build_target_features_count ->
+        [1] feature
+        *[count] features
+        } being enabled in the build configuration does not remove the requirement to list {$build_target_features_count ->
+        [1] it
+        *[count] them
+        } in `#[target_feature]`
     .label = call to function with `#[target_feature]`
 
 mir_build_unsafe_op_in_unsafe_fn_call_to_unsafe_fn_requires_unsafe =

compiler/rustc_mir_build/src/build/matches/mod.rs

@@ -827,6 +827,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
             PatKind::Constant { .. }
             | PatKind::Range { .. }
             | PatKind::Wild
+            | PatKind::Never
             | PatKind::Error(_) => {}
 
             PatKind::Deref { ref subpattern } => {

compiler/rustc_mir_build/src/build/matches/simplify.rs

@@ -194,6 +194,12 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 Ok(())
             }
 
+            PatKind::Never => {
+                // A never pattern acts like a load from the place.
+                // FIXME(never_patterns): load from the place
+                Ok(())
+            }
+
             PatKind::Constant { .. } => {
                 // FIXME normalize patterns when possible
                 Err(match_pair)

compiler/rustc_mir_build/src/build/matches/test.rs

@@ -75,6 +75,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
             | PatKind::Array { .. }
             | PatKind::Wild
             | PatKind::Binding { .. }
+            | PatKind::Never
             | PatKind::Leaf { .. }
             | PatKind::Deref { .. }
             | PatKind::Error(_) => self.error_simplifiable(match_pair),
@@ -107,6 +108,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
             PatKind::Slice { .. }
             | PatKind::Array { .. }
             | PatKind::Wild
+            | PatKind::Never
             | PatKind::Or { .. }
             | PatKind::Binding { .. }
             | PatKind::AscribeUserType { .. }
@@ -494,7 +496,12 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         }
 
         let eq_def_id = self.tcx.require_lang_item(LangItem::PartialEq, Some(source_info.span));
-        let method = trait_method(self.tcx, eq_def_id, sym::eq, [ty, ty]);
+        let method = trait_method(
+            self.tcx,
+            eq_def_id,
+            sym::eq,
+            self.tcx.with_opt_const_effect_param(self.def_id, eq_def_id, [ty, ty]),
+        );
 
         let bool_ty = self.tcx.types.bool;
         let eq_result = self.temp(bool_ty, source_info.span);

compiler/rustc_mir_build/src/check_unsafety.rs

@@ -1,7 +1,10 @@
+use std::borrow::Cow;
+
 use crate::build::ExprCategory;
 use crate::errors::*;
 use rustc_middle::thir::visit::{self, Visitor};
 
+use rustc_errors::DiagnosticArgValue;
 use rustc_hir as hir;
 use rustc_middle::mir::BorrowKind;
 use rustc_middle::thir::*;
@@ -247,8 +250,9 @@ impl<'a, 'tcx> Visitor<'a, 'tcx> for UnsafetyVisitor<'a, 'tcx> {
                     self.requires_unsafe(pat.span, AccessToUnionField);
                     return; // we can return here since this already requires unsafe
                 }
-                // wildcard doesn't take anything
+                // wildcard/never don't take anything
                 PatKind::Wild |
+                PatKind::Never |
                 // these just wrap other patterns
                 PatKind::Or { .. } |
                 PatKind::InlineConstant { .. } |
@@ -392,15 +396,29 @@ impl<'a, 'tcx> Visitor<'a, 'tcx> for UnsafetyVisitor<'a, 'tcx> {
                     // the call requires `unsafe`. Don't check this on wasm
                     // targets, though. For more information on wasm see the
                     // is_like_wasm check in hir_analysis/src/collect.rs
+                    let callee_features = &self.tcx.codegen_fn_attrs(func_did).target_features;
                     if !self.tcx.sess.target.options.is_like_wasm
-                        && !self
+                        && !callee_features
-                            .tcx
-                            .codegen_fn_attrs(func_did)
-                            .target_features
                             .iter()
                             .all(|feature| self.body_target_features.contains(feature))
                     {
-                        self.requires_unsafe(expr.span, CallToFunctionWith(func_did));
+                        let missing: Vec<_> = callee_features
+                            .iter()
+                            .copied()
+                            .filter(|feature| !self.body_target_features.contains(feature))
+                            .collect();
+                        let build_enabled = self
+                            .tcx
+                            .sess
+                            .target_features
+                            .iter()
+                            .copied()
+                            .filter(|feature| missing.contains(feature))
+                            .collect();
+                        self.requires_unsafe(
+                            expr.span,
+                            CallToFunctionWith { function: func_did, missing, build_enabled },
+                        );
                     }
                 }
             }
@@ -526,7 +544,7 @@ struct UnusedUnsafeWarning {
     enclosing_unsafe: Option<UnusedUnsafeEnclosing>,
 }
 
-#[derive(Clone, Copy, PartialEq)]
+#[derive(Clone, PartialEq)]
 enum UnsafeOpKind {
     CallToUnsafeFunction(Option<DefId>),
     UseOfInlineAssembly,
@@ -537,7 +555,15 @@ enum UnsafeOpKind {
     AccessToUnionField,
     MutationOfLayoutConstrainedField,
     BorrowOfLayoutConstrainedField,
-    CallToFunctionWith(DefId),
+    CallToFunctionWith {
+        function: DefId,
+        /// Target features enabled in callee's `#[target_feature]` but missing in
+        /// caller's `#[target_feature]`.
+        missing: Vec<Symbol>,
+        /// Target features in `missing` that are enabled at compile time
+        /// (e.g., with `-C target-feature`).
+        build_enabled: Vec<Symbol>,
+    },
 }
 
 use UnsafeOpKind::*;
@@ -658,13 +684,22 @@ impl UnsafeOpKind {
                     unsafe_not_inherited_note,
                 },
             ),
-            CallToFunctionWith(did) => tcx.emit_spanned_lint(
+            CallToFunctionWith { function, missing, build_enabled } => tcx.emit_spanned_lint(
                 UNSAFE_OP_IN_UNSAFE_FN,
                 hir_id,
                 span,
                 UnsafeOpInUnsafeFnCallToFunctionWithRequiresUnsafe {
                     span,
-                    function: &with_no_trimmed_paths!(tcx.def_path_str(*did)),
+                    function: &with_no_trimmed_paths!(tcx.def_path_str(*function)),
+                    missing_target_features: DiagnosticArgValue::StrListSepByAnd(
+                        missing.iter().map(|feature| Cow::from(feature.as_str())).collect(),
+                    ),
+                    missing_target_features_count: missing.len(),
+                    note: if build_enabled.is_empty() { None } else { Some(()) },
+                    build_target_features: DiagnosticArgValue::StrListSepByAnd(
+                        build_enabled.iter().map(|feature| Cow::from(feature.as_str())).collect(),
+                    ),
+                    build_target_features_count: build_enabled.len(),
                     unsafe_not_inherited_note,
                 },
             ),
@@ -821,18 +856,38 @@ impl UnsafeOpKind {
                     unsafe_not_inherited_note,
                 });
             }
-            CallToFunctionWith(did) if unsafe_op_in_unsafe_fn_allowed => {
+            CallToFunctionWith { function, missing, build_enabled }
+                if unsafe_op_in_unsafe_fn_allowed =>
+            {
                 tcx.sess.emit_err(CallToFunctionWithRequiresUnsafeUnsafeOpInUnsafeFnAllowed {
                     span,
+                    missing_target_features: DiagnosticArgValue::StrListSepByAnd(
+                        missing.iter().map(|feature| Cow::from(feature.as_str())).collect(),
+                    ),
+                    missing_target_features_count: missing.len(),
+                    note: if build_enabled.is_empty() { None } else { Some(()) },
+                    build_target_features: DiagnosticArgValue::StrListSepByAnd(
+                        build_enabled.iter().map(|feature| Cow::from(feature.as_str())).collect(),
+                    ),
+                    build_target_features_count: build_enabled.len(),
                     unsafe_not_inherited_note,
-                    function: &tcx.def_path_str(*did),
+                    function: &tcx.def_path_str(*function),
                 });
             }
-            CallToFunctionWith(did) => {
+            CallToFunctionWith { function, missing, build_enabled } => {
                 tcx.sess.emit_err(CallToFunctionWithRequiresUnsafe {
                     span,
+                    missing_target_features: DiagnosticArgValue::StrListSepByAnd(
+                        missing.iter().map(|feature| Cow::from(feature.as_str())).collect(),
+                    ),
+                    missing_target_features_count: missing.len(),
+                    note: if build_enabled.is_empty() { None } else { Some(()) },
+                    build_target_features: DiagnosticArgValue::StrListSepByAnd(
+                        build_enabled.iter().map(|feature| Cow::from(feature.as_str())).collect(),
+                    ),
+                    build_target_features_count: build_enabled.len(),
                     unsafe_not_inherited_note,
-                    function: &tcx.def_path_str(*did),
+                    function: &tcx.def_path_str(*function),
                 });
             }
         }

compiler/rustc_mir_build/src/errors.rs

@@ -2,6 +2,7 @@ use crate::{
     fluent_generated as fluent,
     thir::pattern::{deconstruct_pat::WitnessPat, MatchCheckCtxt},
 };
+use rustc_errors::DiagnosticArgValue;
 use rustc_errors::{
     error_code, AddToDiagnostic, Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed,
     Handler, IntoDiagnostic, MultiSpan, SubdiagnosticMessage,
@@ -124,11 +125,17 @@ pub struct UnsafeOpInUnsafeFnBorrowOfLayoutConstrainedFieldRequiresUnsafe {
 
 #[derive(LintDiagnostic)]
 #[diag(mir_build_unsafe_op_in_unsafe_fn_call_to_fn_with_requires_unsafe)]
-#[note]
+#[help]
 pub struct UnsafeOpInUnsafeFnCallToFunctionWithRequiresUnsafe<'a> {
     #[label]
     pub span: Span,
     pub function: &'a str,
+    pub missing_target_features: DiagnosticArgValue<'a>,
+    pub missing_target_features_count: usize,
+    #[note]
+    pub note: Option<()>,
+    pub build_target_features: DiagnosticArgValue<'a>,
+    pub build_target_features_count: usize,
     #[subdiagnostic]
     pub unsafe_not_inherited_note: Option<UnsafeNotInheritedLintNote>,
 }
@@ -369,24 +376,36 @@ pub struct BorrowOfLayoutConstrainedFieldRequiresUnsafeUnsafeOpInUnsafeFnAllowed
 
 #[derive(Diagnostic)]
 #[diag(mir_build_call_to_fn_with_requires_unsafe, code = "E0133")]
-#[note]
+#[help]
 pub struct CallToFunctionWithRequiresUnsafe<'a> {
     #[primary_span]
     #[label]
     pub span: Span,
     pub function: &'a str,
+    pub missing_target_features: DiagnosticArgValue<'a>,
+    pub missing_target_features_count: usize,
+    #[note]
+    pub note: Option<()>,
+    pub build_target_features: DiagnosticArgValue<'a>,
+    pub build_target_features_count: usize,
     #[subdiagnostic]
     pub unsafe_not_inherited_note: Option<UnsafeNotInheritedNote>,
 }
 
 #[derive(Diagnostic)]
 #[diag(mir_build_call_to_fn_with_requires_unsafe_unsafe_op_in_unsafe_fn_allowed, code = "E0133")]
-#[note]
+#[help]
 pub struct CallToFunctionWithRequiresUnsafeUnsafeOpInUnsafeFnAllowed<'a> {
     #[primary_span]
     #[label]
     pub span: Span,
     pub function: &'a str,
+    pub missing_target_features: DiagnosticArgValue<'a>,
+    pub missing_target_features_count: usize,
+    #[note]
+    pub note: Option<()>,
+    pub build_target_features: DiagnosticArgValue<'a>,
+    pub build_target_features_count: usize,
     #[subdiagnostic]
     pub unsafe_not_inherited_note: Option<UnsafeNotInheritedNote>,
 }

compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs

@@ -258,18 +258,26 @@ impl<'tcx> ConstToPat<'tcx> {
 
     #[instrument(level = "trace", skip(self), ret)]
     fn type_has_partial_eq_impl(&self, ty: Ty<'tcx>) -> bool {
+        let tcx = self.tcx();
         // double-check there even *is* a semantic `PartialEq` to dispatch to.
         //
         // (If there isn't, then we can safely issue a hard
         // error, because that's never worked, due to compiler
         // using `PartialEq::eq` in this scenario in the past.)
-        let partial_eq_trait_id =
+        let partial_eq_trait_id = tcx.require_lang_item(hir::LangItem::PartialEq, Some(self.span));
-            self.tcx().require_lang_item(hir::LangItem::PartialEq, Some(self.span));
         let partial_eq_obligation = Obligation::new(
-            self.tcx(),
+            tcx,
             ObligationCause::dummy(),
             self.param_env,
-            ty::TraitRef::new(self.tcx(), partial_eq_trait_id, [ty, ty]),
+            ty::TraitRef::new(
+                tcx,
+                partial_eq_trait_id,
+                tcx.with_opt_const_effect_param(
+                    tcx.hir().enclosing_body_owner(self.id),
+                    partial_eq_trait_id,
+                    [ty, ty],
+                ),
+            ),
         );
 
         // This *could* accept a type that isn't actually `PartialEq`, because region bounds get

compiler/rustc_mir_build/src/thir/pattern/deconstruct_pat.rs

@@ -1557,6 +1557,12 @@ impl<'p, 'tcx> DeconstructedPat<'p, 'tcx> {
                 let pats = expand_or_pat(pat);
                 fields = Fields::from_iter(cx, pats.into_iter().map(mkpat));
             }
+            PatKind::Never => {
+                // FIXME(never_patterns): handle `!` in exhaustiveness. This is a sane default
+                // in the meantime.
+                ctor = Wildcard;
+                fields = Fields::empty();
+            }
             PatKind::Error(_) => {
                 ctor = Opaque(OpaqueId::new());
                 fields = Fields::empty();

compiler/rustc_mir_build/src/thir/pattern/mod.rs

@@ -251,6 +251,8 @@ impl<'a, 'tcx> PatCtxt<'a, 'tcx> {
         let kind = match pat.kind {
             hir::PatKind::Wild => PatKind::Wild,
 
+            hir::PatKind::Never => PatKind::Never,
+
             hir::PatKind::Lit(value) => self.lower_lit(value),
 
             hir::PatKind::Range(ref lo_expr, ref hi_expr, end) => {

compiler/rustc_mir_build/src/thir/print.rs

@@ -31,8 +31,8 @@ const INDENT: &str = "    ";
 
 macro_rules! print_indented {
     ($writer:ident, $s:expr, $indent_lvl:expr) => {
-        let indent = (0..$indent_lvl).map(|_| INDENT).collect::<Vec<_>>().concat();
+        $writer.indent($indent_lvl);
-        writeln!($writer, "{}{}", indent, $s).expect("unable to write to ThirPrinter");
+        writeln!($writer, "{}", $s).expect("unable to write to ThirPrinter");
     };
 }
 
@@ -48,6 +48,12 @@ impl<'a, 'tcx> ThirPrinter<'a, 'tcx> {
         Self { thir, fmt: String::new() }
     }
 
+    fn indent(&mut self, level: usize) {
+        for _ in 0..level {
+            self.fmt.push_str(INDENT);
+        }
+    }
+
     fn print(&mut self) {
         print_indented!(self, "params: [", 0);
         for param in self.thir.params.iter() {
@@ -636,6 +642,9 @@ impl<'a, 'tcx> ThirPrinter<'a, 'tcx> {
             PatKind::Wild => {
                 print_indented!(self, "Wild", depth_lvl + 1);
             }
+            PatKind::Never => {
+                print_indented!(self, "Never", depth_lvl + 1);
+            }
             PatKind::AscribeUserType { ascription, subpattern } => {
                 print_indented!(self, "AscribeUserType: {", depth_lvl + 1);
                 print_indented!(self, format!("ascription: {:?}", ascription), depth_lvl + 2);

compiler/rustc_mir_transform/messages.ftl

@@ -42,8 +42,19 @@ mir_transform_requires_unsafe = {$details} is unsafe and requires unsafe {$op_in
     }
     .not_inherited = items do not inherit unsafety from separate enclosing items
 
+mir_transform_target_feature_call_help = in order for the call to be safe, the context requires the following additional target {$missing_target_features_count ->
+    [1] feature
+    *[count] features
+    }: {$missing_target_features}
+
 mir_transform_target_feature_call_label = call to function with `#[target_feature]`
-mir_transform_target_feature_call_note = can only be called if the required target features are available
+mir_transform_target_feature_call_note = the {$build_target_features} target {$build_target_features_count ->
+    [1] feature
+    *[count] features
+    } being enabled in the build configuration does not remove the requirement to list {$build_target_features_count ->
+    [1] it
+    *[count] them
+    } in `#[target_feature]`
 
 mir_transform_unaligned_packed_ref = reference to packed field is unaligned
     .note = packed structs are only aligned by one byte, and many modern architectures penalize unaligned field accesses

compiler/rustc_mir_transform/src/check_unsafety.rs

@@ -287,19 +287,20 @@ impl<'tcx> UnsafetyChecker<'_, 'tcx> {
             .safety;
         match safety {
             // `unsafe` blocks are required in safe code
-            Safety::Safe => violations.into_iter().for_each(|&violation| {
+            Safety::Safe => violations.into_iter().for_each(|violation| {
                 match violation.kind {
                     UnsafetyViolationKind::General => {}
                     UnsafetyViolationKind::UnsafeFn => {
                         bug!("`UnsafetyViolationKind::UnsafeFn` in an `Safe` context")
                     }
                 }
-                if !self.violations.contains(&violation) {
+                if !self.violations.contains(violation) {
-                    self.violations.push(violation)
+                    self.violations.push(violation.clone())
                 }
             }),
             // With the RFC 2585, no longer allow `unsafe` operations in `unsafe fn`s
-            Safety::FnUnsafe => violations.into_iter().for_each(|&(mut violation)| {
+            Safety::FnUnsafe => violations.into_iter().for_each(|violation| {
+                let mut violation = violation.clone();
                 violation.kind = UnsafetyViolationKind::UnsafeFn;
                 if !self.violations.contains(&violation) {
                     self.violations.push(violation)
@@ -367,9 +368,22 @@ impl<'tcx> UnsafetyChecker<'_, 'tcx> {
 
         // Is `callee_features` a subset of `calling_features`?
         if !callee_features.iter().all(|feature| self_features.contains(feature)) {
+            let missing: Vec<_> = callee_features
+                .iter()
+                .copied()
+                .filter(|feature| !self_features.contains(feature))
+                .collect();
+            let build_enabled = self
+                .tcx
+                .sess
+                .target_features
+                .iter()
+                .copied()
+                .filter(|feature| missing.contains(feature))
+                .collect();
             self.require_unsafe(
                 UnsafetyViolationKind::General,
-                UnsafetyViolationDetails::CallToFunctionWith,
+                UnsafetyViolationDetails::CallToFunctionWith { missing, build_enabled },
             )
         }
     }
@@ -385,7 +399,7 @@ pub(crate) fn provide(providers: &mut Providers) {
 enum Context {
     Safe,
     /// in an `unsafe fn`
-    UnsafeFn(HirId),
+    UnsafeFn,
     /// in a *used* `unsafe` block
     /// (i.e. a block without unused-unsafe warning)
     UnsafeBlock(HirId),
@@ -407,7 +421,7 @@ impl<'tcx> intravisit::Visitor<'tcx> for UnusedUnsafeVisitor<'_, 'tcx> {
             };
             let unused_unsafe = match (self.context, used) {
                 (_, false) => UnusedUnsafe::Unused,
-                (Context::Safe, true) | (Context::UnsafeFn(_), true) => {
+                (Context::Safe, true) | (Context::UnsafeFn, true) => {
                     let previous_context = self.context;
                     self.context = Context::UnsafeBlock(block.hir_id);
                     intravisit::walk_block(self, block);
@@ -454,7 +468,7 @@ fn check_unused_unsafe(
     let body = tcx.hir().body(body_id);
     let hir_id = tcx.local_def_id_to_hir_id(def_id);
     let context = match tcx.hir().fn_sig_by_hir_id(hir_id) {
-        Some(sig) if sig.header.unsafety == hir::Unsafety::Unsafe => Context::UnsafeFn(hir_id),
+        Some(sig) if sig.header.unsafety == hir::Unsafety::Unsafe => Context::UnsafeFn,
         _ => Context::Safe,
     };
 
@@ -528,8 +542,9 @@ pub fn check_unsafety(tcx: TyCtxt<'_>, def_id: LocalDefId) {
     // Only suggest wrapping the entire function body in an unsafe block once
     let mut suggest_unsafe_block = true;
 
-    for &UnsafetyViolation { source_info, lint_root, kind, details } in violations.iter() {
+    for &UnsafetyViolation { source_info, lint_root, kind, ref details } in violations.iter() {
-        let details = errors::RequiresUnsafeDetail { violation: details, span: source_info.span };
+        let details =
+            errors::RequiresUnsafeDetail { violation: details.clone(), span: source_info.span };
 
         match kind {
             UnsafetyViolationKind::General => {

compiler/rustc_mir_transform/src/const_prop.rs

@@ -439,6 +439,7 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
 
         // FIXME we need to revisit this for #67176
         if rvalue.has_param() {
+            trace!("skipping, has param");
             return None;
         }
         if !rvalue
@@ -707,7 +708,11 @@ impl<'tcx> Visitor<'tcx> for ConstPropagator<'_, 'tcx> {
     fn visit_assign(&mut self, place: &Place<'tcx>, rvalue: &Rvalue<'tcx>, location: Location) {
         self.super_assign(place, rvalue, location);
 
-        let Some(()) = self.check_rvalue(rvalue) else { return };
+        let Some(()) = self.check_rvalue(rvalue) else {
+            trace!("rvalue check failed, removing const");
+            Self::remove_const(&mut self.ecx, place.local);
+            return;
+        };
 
         match self.ecx.machine.can_const_prop[place.local] {
             // Do nothing if the place is indirect.

compiler/rustc_mir_transform/src/coroutine.rs

@@ -51,7 +51,6 @@
 //! Otherwise it drops all the values in scope at the last suspension point.
 
 use crate::abort_unwinding_calls;
-use crate::add_call_guards;
 use crate::deref_separator::deref_finder;
 use crate::errors;
 use crate::pass_manager as pm;
@@ -1168,18 +1167,9 @@ fn create_coroutine_drop_shim<'tcx>(
     simplify::remove_dead_blocks(&mut body);
 
     // Update the body's def to become the drop glue.
-    // This needs to be updated before the AbortUnwindingCalls pass.
     let coroutine_instance = body.source.instance;
     let drop_in_place = tcx.require_lang_item(LangItem::DropInPlace, None);
     let drop_instance = InstanceDef::DropGlue(drop_in_place, Some(coroutine_ty));
-    body.source.instance = drop_instance;
-
-    pm::run_passes_no_validate(
-        tcx,
-        &mut body,
-        &[&abort_unwinding_calls::AbortUnwindingCalls, &add_call_guards::CriticalCallEdges],
-        None,
-    );
 
     // Temporary change MirSource to coroutine's instance so that dump_mir produces more sensible
     // filename.

compiler/rustc_mir_transform/src/errors.rs

@@ -1,6 +1,8 @@
+use std::borrow::Cow;
+
 use rustc_errors::{
-    Applicability, DecorateLint, DiagnosticBuilder, DiagnosticMessage, EmissionGuarantee, Handler,
+    Applicability, DecorateLint, DiagnosticArgValue, DiagnosticBuilder, DiagnosticMessage,
-    IntoDiagnostic,
+    EmissionGuarantee, Handler, IntoDiagnostic,
 };
 use rustc_macros::{Diagnostic, LintDiagnostic, Subdiagnostic};
 use rustc_middle::mir::{AssertKind, UnsafetyViolationDetails};
@@ -9,6 +11,8 @@ use rustc_session::lint::{self, Lint};
 use rustc_span::def_id::DefId;
 use rustc_span::Span;
 
+use crate::fluent_generated as fluent;
+
 #[derive(LintDiagnostic)]
 pub(crate) enum ConstMutate {
     #[diag(mir_transform_const_modify)]
@@ -61,72 +65,105 @@ pub(crate) struct RequiresUnsafe {
 impl<'sess, G: EmissionGuarantee> IntoDiagnostic<'sess, G> for RequiresUnsafe {
     #[track_caller]
     fn into_diagnostic(self, handler: &'sess Handler) -> DiagnosticBuilder<'sess, G> {
-        let mut diag =
+        let mut diag = handler.struct_diagnostic(fluent::mir_transform_requires_unsafe);
-            handler.struct_diagnostic(crate::fluent_generated::mir_transform_requires_unsafe);
         diag.code(rustc_errors::DiagnosticId::Error("E0133".to_string()));
         diag.set_span(self.span);
         diag.span_label(self.span, self.details.label());
-        diag.note(self.details.note());
         let desc = handler.eagerly_translate_to_string(self.details.label(), [].into_iter());
         diag.set_arg("details", desc);
         diag.set_arg("op_in_unsafe_fn_allowed", self.op_in_unsafe_fn_allowed);
+        self.details.add_subdiagnostics(&mut diag);
         if let Some(sp) = self.enclosing {
-            diag.span_label(sp, crate::fluent_generated::mir_transform_not_inherited);
+            diag.span_label(sp, fluent::mir_transform_not_inherited);
         }
         diag
     }
 }
 
-#[derive(Copy, Clone)]
+#[derive(Clone)]
 pub(crate) struct RequiresUnsafeDetail {
     pub span: Span,
     pub violation: UnsafetyViolationDetails,
 }
 
 impl RequiresUnsafeDetail {
-    fn note(self) -> DiagnosticMessage {
+    fn add_subdiagnostics<G: EmissionGuarantee>(&self, diag: &mut DiagnosticBuilder<'_, G>) {
         use UnsafetyViolationDetails::*;
         match self.violation {
-            CallToUnsafeFunction => crate::fluent_generated::mir_transform_call_to_unsafe_note,
+            CallToUnsafeFunction => {
-            UseOfInlineAssembly => crate::fluent_generated::mir_transform_use_of_asm_note,
+                diag.note(fluent::mir_transform_call_to_unsafe_note);
-            InitializingTypeWith => {
+            }
-                crate::fluent_generated::mir_transform_initializing_valid_range_note
+            UseOfInlineAssembly => {
+                diag.note(fluent::mir_transform_use_of_asm_note);
+            }
+            InitializingTypeWith => {
+                diag.note(fluent::mir_transform_initializing_valid_range_note);
+            }
+            CastOfPointerToInt => {
+                diag.note(fluent::mir_transform_const_ptr2int_note);
+            }
+            UseOfMutableStatic => {
+                diag.note(fluent::mir_transform_use_of_static_mut_note);
+            }
+            UseOfExternStatic => {
+                diag.note(fluent::mir_transform_use_of_extern_static_note);
+            }
+            DerefOfRawPointer => {
+                diag.note(fluent::mir_transform_deref_ptr_note);
+            }
+            AccessToUnionField => {
+                diag.note(fluent::mir_transform_union_access_note);
             }
-            CastOfPointerToInt => crate::fluent_generated::mir_transform_const_ptr2int_note,
-            UseOfMutableStatic => crate::fluent_generated::mir_transform_use_of_static_mut_note,
-            UseOfExternStatic => crate::fluent_generated::mir_transform_use_of_extern_static_note,
-            DerefOfRawPointer => crate::fluent_generated::mir_transform_deref_ptr_note,
-            AccessToUnionField => crate::fluent_generated::mir_transform_union_access_note,
             MutationOfLayoutConstrainedField => {
-                crate::fluent_generated::mir_transform_mutation_layout_constrained_note
+                diag.note(fluent::mir_transform_mutation_layout_constrained_note);
             }
             BorrowOfLayoutConstrainedField => {
-                crate::fluent_generated::mir_transform_mutation_layout_constrained_borrow_note
+                diag.note(fluent::mir_transform_mutation_layout_constrained_borrow_note);
+            }
+            CallToFunctionWith { ref missing, ref build_enabled } => {
+                diag.help(fluent::mir_transform_target_feature_call_help);
+                diag.set_arg(
+                    "missing_target_features",
+                    DiagnosticArgValue::StrListSepByAnd(
+                        missing.iter().map(|feature| Cow::from(feature.as_str())).collect(),
+                    ),
+                );
+                diag.set_arg("missing_target_features_count", missing.len());
+                if !build_enabled.is_empty() {
+                    diag.note(fluent::mir_transform_target_feature_call_note);
+                    diag.set_arg(
+                        "build_target_features",
+                        DiagnosticArgValue::StrListSepByAnd(
+                            build_enabled
+                                .iter()
+                                .map(|feature| Cow::from(feature.as_str()))
+                                .collect(),
+                        ),
+                    );
+                    diag.set_arg("build_target_features_count", build_enabled.len());
+                }
             }
-            CallToFunctionWith => crate::fluent_generated::mir_transform_target_feature_call_note,
         }
     }
 
-    fn label(self) -> DiagnosticMessage {
+    fn label(&self) -> DiagnosticMessage {
         use UnsafetyViolationDetails::*;
         match self.violation {
-            CallToUnsafeFunction => crate::fluent_generated::mir_transform_call_to_unsafe_label,
+            CallToUnsafeFunction => fluent::mir_transform_call_to_unsafe_label,
-            UseOfInlineAssembly => crate::fluent_generated::mir_transform_use_of_asm_label,
+            UseOfInlineAssembly => fluent::mir_transform_use_of_asm_label,
-            InitializingTypeWith => {
+            InitializingTypeWith => fluent::mir_transform_initializing_valid_range_label,
-                crate::fluent_generated::mir_transform_initializing_valid_range_label
+            CastOfPointerToInt => fluent::mir_transform_const_ptr2int_label,
-            }
+            UseOfMutableStatic => fluent::mir_transform_use_of_static_mut_label,
-            CastOfPointerToInt => crate::fluent_generated::mir_transform_const_ptr2int_label,
+            UseOfExternStatic => fluent::mir_transform_use_of_extern_static_label,
-            UseOfMutableStatic => crate::fluent_generated::mir_transform_use_of_static_mut_label,
+            DerefOfRawPointer => fluent::mir_transform_deref_ptr_label,
-            UseOfExternStatic => crate::fluent_generated::mir_transform_use_of_extern_static_label,
+            AccessToUnionField => fluent::mir_transform_union_access_label,
-            DerefOfRawPointer => crate::fluent_generated::mir_transform_deref_ptr_label,
-            AccessToUnionField => crate::fluent_generated::mir_transform_union_access_label,
             MutationOfLayoutConstrainedField => {
-                crate::fluent_generated::mir_transform_mutation_layout_constrained_label
+                fluent::mir_transform_mutation_layout_constrained_label
             }
             BorrowOfLayoutConstrainedField => {
-                crate::fluent_generated::mir_transform_mutation_layout_constrained_borrow_label
+                fluent::mir_transform_mutation_layout_constrained_borrow_label
             }
-            CallToFunctionWith => crate::fluent_generated::mir_transform_target_feature_call_label,
+            CallToFunctionWith { .. } => fluent::mir_transform_target_feature_call_label,
         }
     }
 }
@@ -151,12 +188,12 @@ impl<'a> DecorateLint<'a, ()> for UnsafeOpInUnsafeFn {
         let desc = handler.eagerly_translate_to_string(self.details.label(), [].into_iter());
         diag.set_arg("details", desc);
         diag.span_label(self.details.span, self.details.label());
-        diag.note(self.details.note());
+        self.details.add_subdiagnostics(diag);
 
         if let Some((start, end, fn_sig)) = self.suggest_unsafe_block {
-            diag.span_note(fn_sig, crate::fluent_generated::mir_transform_note);
+            diag.span_note(fn_sig, fluent::mir_transform_note);
             diag.tool_only_multipart_suggestion(
-                crate::fluent_generated::mir_transform_suggestion,
+                fluent::mir_transform_suggestion,
                 vec![(start, " unsafe {".into()), (end, "}".into())],
                 Applicability::MaybeIncorrect,
             );
@@ -166,7 +203,7 @@ impl<'a> DecorateLint<'a, ()> for UnsafeOpInUnsafeFn {
     }
 
     fn msg(&self) -> DiagnosticMessage {
-        crate::fluent_generated::mir_transform_unsafe_op_in_unsafe_fn
+        fluent::mir_transform_unsafe_op_in_unsafe_fn
     }
 }
 
@@ -193,12 +230,8 @@ impl<'a, P: std::fmt::Debug> DecorateLint<'a, ()> for AssertLint<P> {
 
     fn msg(&self) -> DiagnosticMessage {
         match self {
-            AssertLint::ArithmeticOverflow(..) => {
+            AssertLint::ArithmeticOverflow(..) => fluent::mir_transform_arithmetic_overflow,
-                crate::fluent_generated::mir_transform_arithmetic_overflow
+            AssertLint::UnconditionalPanic(..) => fluent::mir_transform_operation_will_panic,
-            }
-            AssertLint::UnconditionalPanic(..) => {
-                crate::fluent_generated::mir_transform_operation_will_panic
-            }
         }
     }
 }
@@ -255,11 +288,11 @@ impl<'a> DecorateLint<'a, ()> for MustNotSupend<'_, '_> {
         self,
         diag: &'b mut rustc_errors::DiagnosticBuilder<'a, ()>,
     ) -> &'b mut rustc_errors::DiagnosticBuilder<'a, ()> {
-        diag.span_label(self.yield_sp, crate::fluent_generated::_subdiag::label);
+        diag.span_label(self.yield_sp, fluent::_subdiag::label);
         if let Some(reason) = self.reason {
             diag.subdiagnostic(reason);
         }
-        diag.span_help(self.src_sp, crate::fluent_generated::_subdiag::help);
+        diag.span_help(self.src_sp, fluent::_subdiag::help);
         diag.set_arg("pre", self.pre);
         diag.set_arg("def_path", self.tcx.def_path_str(self.def_id));
         diag.set_arg("post", self.post);
@@ -267,7 +300,7 @@ impl<'a> DecorateLint<'a, ()> for MustNotSupend<'_, '_> {
     }
 
     fn msg(&self) -> rustc_errors::DiagnosticMessage {
-        crate::fluent_generated::mir_transform_must_not_suspend
+        fluent::mir_transform_must_not_suspend
     }
 }
 

compiler/rustc_mir_transform/src/shim.rs

@@ -74,11 +74,13 @@ fn make_shim<'tcx>(tcx: TyCtxt<'tcx>, instance: ty::InstanceDef<'tcx>) -> Body<'
                 let mut body = EarlyBinder::bind(body.clone()).instantiate(tcx, args);
                 debug!("make_shim({:?}) = {:?}", instance, body);
 
-                // Run empty passes to mark phase change and perform validation.
                 pm::run_passes(
                     tcx,
                     &mut body,
-                    &[],
+                    &[
+                        &abort_unwinding_calls::AbortUnwindingCalls,
+                        &add_call_guards::CriticalCallEdges,
+                    ],
                     Some(MirPhase::Runtime(RuntimePhase::Optimized)),
                 );
 

compiler/rustc_parse/messages.ftl

@@ -492,9 +492,13 @@ parse_match_arm_body_without_braces = `match` arm body without braces
         } with a body
     .suggestion_use_comma_not_semicolon = replace `;` with `,` to end a `match` arm expression
 
+parse_maybe_comparison = you might have meant to compare for equality
+
 parse_maybe_fn_typo_with_impl = you might have meant to write `impl` instead of `fn`
     .suggestion = replace `fn` with `impl` here
 
+parse_maybe_missing_let = you might have meant to continue the let-chain
+
 parse_maybe_recover_from_bad_qpath_stage_2 =
     missing angle brackets in associated item path
     .suggestion = types that don't start with an identifier need to be surrounded with angle brackets in qualified paths
@@ -721,6 +725,9 @@ parse_sugg_wrap_pattern_in_parens = wrap the pattern in parentheses
 parse_switch_mut_let_order =
     switch the order of `mut` and `let`
 
+parse_switch_ref_box_order = switch the order of `ref` and `box`
+    .suggestion = swap them
+
 parse_ternary_operator = Rust has no ternary operator
     .help = use an `if-else` expression instead
 
@@ -770,6 +777,9 @@ parse_unexpected_lifetime_in_pattern = unexpected lifetime `{$symbol}` in patter
 parse_unexpected_parentheses_in_for_head = unexpected parentheses surrounding `for` loop head
     .suggestion = remove parentheses in `for` loop
 
+parse_unexpected_parentheses_in_match_arm_pattern = unexpected parentheses surrounding `match` arm pattern
+    .suggestion = remove parentheses surrounding the pattern
+
 parse_unexpected_self_in_generic_parameters = unexpected keyword `Self` in generic parameters
     .note = you cannot use `Self` as a generic parameter because it is reserved for associated items
 

compiler/rustc_parse/src/errors.rs

@@ -137,6 +137,14 @@ pub(crate) enum InvalidVariableDeclarationSub {
     UseLetNotVar(#[primary_span] Span),
 }
 
+#[derive(Diagnostic)]
+#[diag(parse_switch_ref_box_order)]
+pub(crate) struct SwitchRefBoxOrder {
+    #[primary_span]
+    #[suggestion(applicability = "machine-applicable", code = "box ref")]
+    pub span: Span,
+}
+
 #[derive(Diagnostic)]
 #[diag(parse_invalid_comparison_operator)]
 pub(crate) struct InvalidComparisonOperator {
@@ -407,6 +415,32 @@ pub(crate) struct ExpectedExpressionFoundLet {
     pub span: Span,
     #[subdiagnostic]
     pub reason: ForbiddenLetReason,
+    #[subdiagnostic]
+    pub missing_let: Option<MaybeMissingLet>,
+    #[subdiagnostic]
+    pub comparison: Option<MaybeComparison>,
+}
+
+#[derive(Subdiagnostic, Clone, Copy)]
+#[multipart_suggestion(
+    parse_maybe_missing_let,
+    applicability = "maybe-incorrect",
+    style = "verbose"
+)]
+pub(crate) struct MaybeMissingLet {
+    #[suggestion_part(code = "let ")]
+    pub span: Span,
+}
+
+#[derive(Subdiagnostic, Clone, Copy)]
+#[multipart_suggestion(
+    parse_maybe_comparison,
+    applicability = "maybe-incorrect",
+    style = "verbose"
+)]
+pub(crate) struct MaybeComparison {
+    #[suggestion_part(code = "=")]
+    pub span: Span,
 }
 
 #[derive(Diagnostic)]
@@ -1241,12 +1275,28 @@ pub(crate) struct ParenthesesInForHead {
 #[derive(Subdiagnostic)]
 #[multipart_suggestion(parse_suggestion, applicability = "machine-applicable")]
 pub(crate) struct ParenthesesInForHeadSugg {
-    #[suggestion_part(code = "{left_snippet}")]
+    #[suggestion_part(code = " ")]
     pub left: Span,
-    pub left_snippet: String,
+    #[suggestion_part(code = " ")]
-    #[suggestion_part(code = "{right_snippet}")]
+    pub right: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(parse_unexpected_parentheses_in_match_arm_pattern)]
+pub(crate) struct ParenthesesInMatchPat {
+    #[primary_span]
+    pub span: Vec<Span>,
+    #[subdiagnostic]
+    pub sugg: ParenthesesInMatchPatSugg,
+}
+
+#[derive(Subdiagnostic)]
+#[multipart_suggestion(parse_suggestion, applicability = "machine-applicable")]
+pub(crate) struct ParenthesesInMatchPatSugg {
+    #[suggestion_part(code = "")]
+    pub left: Span,
+    #[suggestion_part(code = "")]
     pub right: Span,
-    pub right_snippet: String,
 }
 
 #[derive(Diagnostic)]

compiler/rustc_parse/src/parser/diagnostics.rs

@@ -11,12 +11,12 @@ use crate::errors::{
     DoubleColonInBound, ExpectedIdentifier, ExpectedSemi, ExpectedSemiSugg,
     GenericParamsWithoutAngleBrackets, GenericParamsWithoutAngleBracketsSugg,
     HelpIdentifierStartsWithNumber, InInTypo, IncorrectAwait, IncorrectSemicolon,
-    IncorrectUseOfAwait, ParenthesesInForHead, ParenthesesInForHeadSugg,
+    IncorrectUseOfAwait, PatternMethodParamWithoutBody, QuestionMarkInType, QuestionMarkInTypeSugg,
-    PatternMethodParamWithoutBody, QuestionMarkInType, QuestionMarkInTypeSugg, SelfParamNotFirst,
+    SelfParamNotFirst, StructLiteralBodyWithoutPath, StructLiteralBodyWithoutPathSugg,
-    StructLiteralBodyWithoutPath, StructLiteralBodyWithoutPathSugg, StructLiteralNeedingParens,
+    StructLiteralNeedingParens, StructLiteralNeedingParensSugg, SuggAddMissingLetStmt,
-    StructLiteralNeedingParensSugg, SuggAddMissingLetStmt, SuggEscapeIdentifier, SuggRemoveComma,
+    SuggEscapeIdentifier, SuggRemoveComma, TernaryOperator, UnexpectedConstInGenericParam,
-    TernaryOperator, UnexpectedConstInGenericParam, UnexpectedConstParamDeclaration,
+    UnexpectedConstParamDeclaration, UnexpectedConstParamDeclarationSugg, UnmatchedAngleBrackets,
-    UnexpectedConstParamDeclarationSugg, UnmatchedAngleBrackets, UseEqInstead, WrapType,
+    UseEqInstead, WrapType,
 };
 
 use crate::fluent_generated as fluent;
@@ -1994,56 +1994,6 @@ impl<'a> Parser<'a> {
         }
     }
 
-    /// Recovers a situation like `for ( $pat in $expr )`
-    /// and suggest writing `for $pat in $expr` instead.
-    ///
-    /// This should be called before parsing the `$block`.
-    pub(super) fn recover_parens_around_for_head(
-        &mut self,
-        pat: P<Pat>,
-        begin_paren: Option<Span>,
-    ) -> P<Pat> {
-        match (&self.token.kind, begin_paren) {
-            (token::CloseDelim(Delimiter::Parenthesis), Some(begin_par_sp)) => {
-                self.bump();
-
-                let sm = self.sess.source_map();
-                let left = begin_par_sp;
-                let right = self.prev_token.span;
-                let left_snippet = if let Ok(snip) = sm.span_to_prev_source(left)
-                    && !snip.ends_with(' ')
-                {
-                    " ".to_string()
-                } else {
-                    "".to_string()
-                };
-
-                let right_snippet = if let Ok(snip) = sm.span_to_next_source(right)
-                    && !snip.starts_with(' ')
-                {
-                    " ".to_string()
-                } else {
-                    "".to_string()
-                };
-
-                self.sess.emit_err(ParenthesesInForHead {
-                    span: vec![left, right],
-                    // With e.g. `for (x) in y)` this would replace `(x) in y)`
-                    // with `x) in y)` which is syntactically invalid.
-                    // However, this is prevented before we get here.
-                    sugg: ParenthesesInForHeadSugg { left, right, left_snippet, right_snippet },
-                });
-
-                // Unwrap `(pat)` into `pat` to avoid the `unused_parens` lint.
-                pat.and_then(|pat| match pat.kind {
-                    PatKind::Paren(pat) => pat,
-                    _ => P(pat),
-                })
-            }
-            _ => pat,
-        }
-    }
-
     pub(super) fn recover_seq_parse_error(
         &mut self,
         delim: Delimiter,

compiler/rustc_parse/src/parser/expr.rs

@@ -1,3 +1,4 @@
+// ignore-tidy-filelength
 use super::diagnostics::SnapshotParser;
 use super::pat::{CommaRecoveryMode, Expected, RecoverColon, RecoverComma};
 use super::ty::{AllowPlus, RecoverQPath, RecoverReturnSign};
@@ -9,7 +10,7 @@ use super::{
 use crate::errors;
 use crate::maybe_recover_from_interpolated_ty_qpath;
 use ast::mut_visit::{noop_visit_expr, MutVisitor};
-use ast::{GenBlockKind, Path, PathSegment};
+use ast::{GenBlockKind, Pat, Path, PathSegment};
 use core::mem;
 use rustc_ast::ptr::P;
 use rustc_ast::token::{self, Delimiter, Token, TokenKind};
@@ -2477,7 +2478,7 @@ impl<'a> Parser<'a> {
         let mut cond =
             self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL | Restrictions::ALLOW_LET, None)?;
 
-        CondChecker { parser: self, forbid_let_reason: None }.visit_expr(&mut cond);
+        CondChecker::new(self).visit_expr(&mut cond);
 
         if let ExprKind::Let(_, _, _, None) = cond.kind {
             // Remove the last feature gating of a `let` expression since it's stable.
@@ -2493,6 +2494,8 @@ impl<'a> Parser<'a> {
             let err = errors::ExpectedExpressionFoundLet {
                 span: self.token.span,
                 reason: ForbiddenLetReason::OtherForbidden,
+                missing_let: None,
+                comparison: None,
             };
             if self.prev_token.kind == token::BinOp(token::Or) {
                 // This was part of a closure, the that part of the parser recover.
@@ -2606,30 +2609,72 @@ impl<'a> Parser<'a> {
         }
     }
 
-    /// Parses `for <src_pat> in <src_expr> <src_loop_block>` (`for` token already eaten).
+    fn parse_for_head(&mut self) -> PResult<'a, (P<Pat>, P<Expr>)> {
-    fn parse_expr_for(&mut self, opt_label: Option<Label>, lo: Span) -> PResult<'a, P<Expr>> {
+        let begin_paren = if self.token.kind == token::OpenDelim(Delimiter::Parenthesis) {
-        // Record whether we are about to parse `for (`.
+            // Record whether we are about to parse `for (`.
-        // This is used below for recovery in case of `for ( $stuff ) $block`
+            // This is used below for recovery in case of `for ( $stuff ) $block`
-        // in which case we will suggest `for $stuff $block`.
+            // in which case we will suggest `for $stuff $block`.
-        let begin_paren = match self.token.kind {
+            let start_span = self.token.span;
-            token::OpenDelim(Delimiter::Parenthesis) => Some(self.token.span),
+            let left = self.prev_token.span.between(self.look_ahead(1, |t| t.span));
-            _ => None,
+            Some((start_span, left))
+        } else {
+            None
+        };
+        // Try to parse the pattern `for ($PAT) in $EXPR`.
+        let pat = match (
+            self.parse_pat_allow_top_alt(
+                None,
+                RecoverComma::Yes,
+                RecoverColon::Yes,
+                CommaRecoveryMode::LikelyTuple,
+            ),
+            begin_paren,
+        ) {
+            (Ok(pat), _) => pat, // Happy path.
+            (Err(err), Some((start_span, left))) if self.eat_keyword(kw::In) => {
+                // We know for sure we have seen `for ($SOMETHING in`. In the happy path this would
+                // happen right before the return of this method.
+                let expr = match self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None) {
+                    Ok(expr) => expr,
+                    Err(expr_err) => {
+                        // We don't know what followed the `in`, so cancel and bubble up the
+                        // original error.
+                        expr_err.cancel();
+                        return Err(err);
+                    }
+                };
+                return if self.token.kind == token::CloseDelim(Delimiter::Parenthesis) {
+                    // We know for sure we have seen `for ($SOMETHING in $EXPR)`, so we recover the
+                    // parser state and emit a targetted suggestion.
+                    let span = vec![start_span, self.token.span];
+                    let right = self.prev_token.span.between(self.look_ahead(1, |t| t.span));
+                    self.bump(); // )
+                    err.cancel();
+                    self.sess.emit_err(errors::ParenthesesInForHead {
+                        span,
+                        // With e.g. `for (x) in y)` this would replace `(x) in y)`
+                        // with `x) in y)` which is syntactically invalid.
+                        // However, this is prevented before we get here.
+                        sugg: errors::ParenthesesInForHeadSugg { left, right },
+                    });
+                    Ok((self.mk_pat(start_span.to(right), ast::PatKind::Wild), expr))
+                } else {
+                    Err(err) // Some other error, bubble up.
+                };
+            }
+            (Err(err), _) => return Err(err), // Some other error, bubble up.
         };
-
-        let pat = self.parse_pat_allow_top_alt(
-            None,
-            RecoverComma::Yes,
-            RecoverColon::Yes,
-            CommaRecoveryMode::LikelyTuple,
-        )?;
         if !self.eat_keyword(kw::In) {
             self.error_missing_in_for_loop();
         }
         self.check_for_for_in_in_typo(self.prev_token.span);
         let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
+        Ok((pat, expr))
+    }
 
-        let pat = self.recover_parens_around_for_head(pat, begin_paren);
+    /// Parses `for <src_pat> in <src_expr> <src_loop_block>` (`for` token already eaten).
-
+    fn parse_expr_for(&mut self, opt_label: Option<Label>, lo: Span) -> PResult<'a, P<Expr>> {
+        let (pat, expr) = self.parse_for_head()?;
         // Recover from missing expression in `for` loop
         if matches!(expr.kind, ExprKind::Block(..))
             && !matches!(self.token.kind, token::OpenDelim(Delimiter::Brace))
@@ -2850,47 +2895,10 @@ impl<'a> Parser<'a> {
     }
 
     pub(super) fn parse_arm(&mut self) -> PResult<'a, Arm> {
-        // Used to check the `let_chains` and `if_let_guard` features mostly by scanning
-        // `&&` tokens.
-        fn check_let_expr(expr: &Expr) -> (bool, bool) {
-            match &expr.kind {
-                ExprKind::Binary(BinOp { node: BinOpKind::And, .. }, lhs, rhs) => {
-                    let lhs_rslt = check_let_expr(lhs);
-                    let rhs_rslt = check_let_expr(rhs);
-                    (lhs_rslt.0 || rhs_rslt.0, false)
-                }
-                ExprKind::Let(..) => (true, true),
-                _ => (false, true),
-            }
-        }
         let attrs = self.parse_outer_attributes()?;
         self.collect_tokens_trailing_token(attrs, ForceCollect::No, |this, attrs| {
             let lo = this.token.span;
-            let pat = this.parse_pat_allow_top_alt(
+            let (pat, guard) = this.parse_match_arm_pat_and_guard()?;
-                None,
-                RecoverComma::Yes,
-                RecoverColon::Yes,
-                CommaRecoveryMode::EitherTupleOrPipe,
-            )?;
-            let guard = if this.eat_keyword(kw::If) {
-                let if_span = this.prev_token.span;
-                let mut cond = this.parse_match_guard_condition()?;
-
-                CondChecker { parser: this, forbid_let_reason: None }.visit_expr(&mut cond);
-
-                let (has_let_expr, does_not_have_bin_op) = check_let_expr(&cond);
-                if has_let_expr {
-                    if does_not_have_bin_op {
-                        // Remove the last feature gating of a `let` expression since it's stable.
-                        this.sess.gated_spans.ungate_last(sym::let_chains, cond.span);
-                    }
-                    let span = if_span.to(cond.span);
-                    this.sess.gated_spans.gate(sym::if_let_guard, span);
-                }
-                Some(cond)
-            } else {
-                None
-            };
             let arrow_span = this.token.span;
             if let Err(mut err) = this.expect(&token::FatArrow) {
                 // We might have a `=>` -> `=` or `->` typo (issue #89396).
@@ -3020,6 +3028,90 @@ impl<'a> Parser<'a> {
         })
     }
 
+    fn parse_match_arm_guard(&mut self) -> PResult<'a, Option<P<Expr>>> {
+        // Used to check the `let_chains` and `if_let_guard` features mostly by scanning
+        // `&&` tokens.
+        fn check_let_expr(expr: &Expr) -> (bool, bool) {
+            match &expr.kind {
+                ExprKind::Binary(BinOp { node: BinOpKind::And, .. }, lhs, rhs) => {
+                    let lhs_rslt = check_let_expr(lhs);
+                    let rhs_rslt = check_let_expr(rhs);
+                    (lhs_rslt.0 || rhs_rslt.0, false)
+                }
+                ExprKind::Let(..) => (true, true),
+                _ => (false, true),
+            }
+        }
+        if !self.eat_keyword(kw::If) {
+            // No match arm guard present.
+            return Ok(None);
+        }
+
+        let if_span = self.prev_token.span;
+        let mut cond = self.parse_match_guard_condition()?;
+
+        CondChecker::new(self).visit_expr(&mut cond);
+
+        let (has_let_expr, does_not_have_bin_op) = check_let_expr(&cond);
+        if has_let_expr {
+            if does_not_have_bin_op {
+                // Remove the last feature gating of a `let` expression since it's stable.
+                self.sess.gated_spans.ungate_last(sym::let_chains, cond.span);
+            }
+            let span = if_span.to(cond.span);
+            self.sess.gated_spans.gate(sym::if_let_guard, span);
+        }
+        Ok(Some(cond))
+    }
+
+    fn parse_match_arm_pat_and_guard(&mut self) -> PResult<'a, (P<Pat>, Option<P<Expr>>)> {
+        if self.token.kind == token::OpenDelim(Delimiter::Parenthesis) {
+            // Detect and recover from `($pat if $cond) => $arm`.
+            let left = self.token.span;
+            match self.parse_pat_allow_top_alt(
+                None,
+                RecoverComma::Yes,
+                RecoverColon::Yes,
+                CommaRecoveryMode::EitherTupleOrPipe,
+            ) {
+                Ok(pat) => Ok((pat, self.parse_match_arm_guard()?)),
+                Err(err)
+                    if let prev_sp = self.prev_token.span
+                        && let true = self.eat_keyword(kw::If) =>
+                {
+                    // We know for certain we've found `($pat if` so far.
+                    let mut cond = match self.parse_match_guard_condition() {
+                        Ok(cond) => cond,
+                        Err(cond_err) => {
+                            cond_err.cancel();
+                            return Err(err);
+                        }
+                    };
+                    err.cancel();
+                    CondChecker::new(self).visit_expr(&mut cond);
+                    self.eat_to_tokens(&[&token::CloseDelim(Delimiter::Parenthesis)]);
+                    self.expect(&token::CloseDelim(Delimiter::Parenthesis))?;
+                    let right = self.prev_token.span;
+                    self.sess.emit_err(errors::ParenthesesInMatchPat {
+                        span: vec![left, right],
+                        sugg: errors::ParenthesesInMatchPatSugg { left, right },
+                    });
+                    Ok((self.mk_pat(left.to(prev_sp), ast::PatKind::Wild), Some(cond)))
+                }
+                Err(err) => Err(err),
+            }
+        } else {
+            // Regular parser flow:
+            let pat = self.parse_pat_allow_top_alt(
+                None,
+                RecoverComma::Yes,
+                RecoverColon::Yes,
+                CommaRecoveryMode::EitherTupleOrPipe,
+            )?;
+            Ok((pat, self.parse_match_arm_guard()?))
+        }
+    }
+
     fn parse_match_guard_condition(&mut self) -> PResult<'a, P<Expr>> {
         self.parse_expr_res(Restrictions::ALLOW_LET | Restrictions::IN_IF_GUARD, None).map_err(
             |mut err| {
@@ -3552,6 +3644,14 @@ pub(crate) enum ForbiddenLetReason {
 struct CondChecker<'a> {
     parser: &'a Parser<'a>,
     forbid_let_reason: Option<ForbiddenLetReason>,
+    missing_let: Option<errors::MaybeMissingLet>,
+    comparison: Option<errors::MaybeComparison>,
+}
+
+impl<'a> CondChecker<'a> {
+    fn new(parser: &'a Parser<'a>) -> Self {
+        CondChecker { parser, forbid_let_reason: None, missing_let: None, comparison: None }
+    }
 }
 
 impl MutVisitor for CondChecker<'_> {
@@ -3562,11 +3662,13 @@ impl MutVisitor for CondChecker<'_> {
         match e.kind {
             ExprKind::Let(_, _, _, ref mut is_recovered @ None) => {
                 if let Some(reason) = self.forbid_let_reason {
-                    *is_recovered = Some(
+                    *is_recovered =
-                        self.parser
+                        Some(self.parser.sess.emit_err(errors::ExpectedExpressionFoundLet {
-                            .sess
+                            span,
-                            .emit_err(errors::ExpectedExpressionFoundLet { span, reason }),
+                            reason,
-                    );
+                            missing_let: self.missing_let,
+                            comparison: self.comparison,
+                        }));
                 } else {
                     self.parser.sess.gated_spans.gate(sym::let_chains, span);
                 }
@@ -3590,9 +3692,28 @@ impl MutVisitor for CondChecker<'_> {
                 noop_visit_expr(e, self);
                 self.forbid_let_reason = forbid_let_reason;
             }
+            ExprKind::Assign(ref lhs, _, span) => {
+                let forbid_let_reason = self.forbid_let_reason;
+                self.forbid_let_reason = Some(OtherForbidden);
+                let missing_let = self.missing_let;
+                if let ExprKind::Binary(_, _, rhs) = &lhs.kind
+                    && let ExprKind::Path(_, _)
+                    | ExprKind::Struct(_)
+                    | ExprKind::Call(_, _)
+                    | ExprKind::Array(_) = rhs.kind
+                {
+                    self.missing_let =
+                        Some(errors::MaybeMissingLet { span: rhs.span.shrink_to_lo() });
+                }
+                let comparison = self.comparison;
+                self.comparison = Some(errors::MaybeComparison { span: span.shrink_to_hi() });
+                noop_visit_expr(e, self);
+                self.forbid_let_reason = forbid_let_reason;
+                self.missing_let = missing_let;
+                self.comparison = comparison;
+            }
             ExprKind::Unary(_, _)
             | ExprKind::Await(_, _)
-            | ExprKind::Assign(_, _, _)
             | ExprKind::AssignOp(_, _, _)
             | ExprKind::Range(_, _, _)
             | ExprKind::Try(_)

compiler/rustc_parse/src/parser/item.rs

@@ -1415,8 +1415,8 @@ impl<'a> Parser<'a> {
             self.bump();
             (thin_vec![], false)
         } else {
-            self.parse_delim_comma_seq(Delimiter::Brace, |p| p.parse_enum_variant()).map_err(
+            self.parse_delim_comma_seq(Delimiter::Brace, |p| p.parse_enum_variant(id.span))
-                |mut err| {
+                .map_err(|mut err| {
                     err.span_label(id.span, "while parsing this enum");
                     if self.token == token::Colon {
                         let snapshot = self.create_snapshot_for_diagnostic();
@@ -1436,20 +1436,22 @@ impl<'a> Parser<'a> {
                         }
                         self.restore_snapshot(snapshot);
                     }
-                    self.recover_stmt();
+                    self.eat_to_tokens(&[&token::CloseDelim(Delimiter::Brace)]);
+                    self.bump(); // }
                     err
-                },
+                })?
-            )?
         };
 
         let enum_definition = EnumDef { variants: variants.into_iter().flatten().collect() };
         Ok((id, ItemKind::Enum(enum_definition, generics)))
     }
 
-    fn parse_enum_variant(&mut self) -> PResult<'a, Option<Variant>> {
+    fn parse_enum_variant(&mut self, span: Span) -> PResult<'a, Option<Variant>> {
         self.recover_diff_marker();
         let variant_attrs = self.parse_outer_attributes()?;
         self.recover_diff_marker();
+        let help = "enum variants can be `Variant`, `Variant = <integer>`, \
+                    `Variant(Type, ..., TypeN)` or `Variant { fields: Types }`";
         self.collect_tokens_trailing_token(
             variant_attrs,
             ForceCollect::No,
@@ -1476,10 +1478,39 @@ impl<'a> Parser<'a> {
                 let struct_def = if this.check(&token::OpenDelim(Delimiter::Brace)) {
                     // Parse a struct variant.
                     let (fields, recovered) =
-                        this.parse_record_struct_body("struct", ident.span, false)?;
+                        match this.parse_record_struct_body("struct", ident.span, false) {
+                            Ok((fields, recovered)) => (fields, recovered),
+                            Err(mut err) => {
+                                if this.token == token::Colon {
+                                    // We handle `enum` to `struct` suggestion in the caller.
+                                    return Err(err);
+                                }
+                                this.eat_to_tokens(&[&token::CloseDelim(Delimiter::Brace)]);
+                                this.bump(); // }
+                                err.span_label(span, "while parsing this enum");
+                                err.help(help);
+                                err.emit();
+                                (thin_vec![], true)
+                            }
+                        };
                     VariantData::Struct(fields, recovered)
                 } else if this.check(&token::OpenDelim(Delimiter::Parenthesis)) {
-                    VariantData::Tuple(this.parse_tuple_struct_body()?, DUMMY_NODE_ID)
+                    let body = match this.parse_tuple_struct_body() {
+                        Ok(body) => body,
+                        Err(mut err) => {
+                            if this.token == token::Colon {
+                                // We handle `enum` to `struct` suggestion in the caller.
+                                return Err(err);
+                            }
+                            this.eat_to_tokens(&[&token::CloseDelim(Delimiter::Parenthesis)]);
+                            this.bump(); // )
+                            err.span_label(span, "while parsing this enum");
+                            err.help(help);
+                            err.emit();
+                            thin_vec![]
+                        }
+                    };
+                    VariantData::Tuple(body, DUMMY_NODE_ID)
                 } else {
                     VariantData::Unit(DUMMY_NODE_ID)
                 };
@@ -1500,8 +1531,9 @@ impl<'a> Parser<'a> {
 
                 Ok((Some(vr), TrailingToken::MaybeComma))
             },
-        ).map_err(|mut err| {
+        )
-            err.help("enum variants can be `Variant`, `Variant = <integer>`, `Variant(Type, ..., TypeN)` or `Variant { fields: Types }`");
+        .map_err(|mut err| {
+            err.help(help);
             err
         })
     }

compiler/rustc_parse/src/parser/mod.rs

@@ -875,6 +875,9 @@ impl<'a> Parser<'a> {
                                     if self.token == token::Colon {
                                         // we will try to recover in `maybe_recover_struct_lit_bad_delims`
                                         return Err(expect_err);
+                                    } else if let [token::CloseDelim(Delimiter::Parenthesis)] = kets
+                                    {
+                                        return Err(expect_err);
                                     } else {
                                         expect_err.emit();
                                         break;