Auto merge of #3238 - rust-lang:rustup-2023-12-24, r=saethlin

Automatic Rustup

.github/workflows/ci.yml

@@ -289,8 +289,9 @@ jobs:
             os: ubuntu-20.04-4core-16gb
             env: {}
           - name: x86_64-gnu-integration
+            env:
+              CI_ONLY_WHEN_CHANNEL: nightly
             os: ubuntu-20.04-16core-64gb
-            env: {}
           - name: x86_64-gnu-debug
             os: ubuntu-20.04-8core-32gb
             env: {}

Cargo.lock

@@ -4340,6 +4340,7 @@ dependencies = [
 name = "rustc_pattern_analysis"
 version = "0.0.0"
 dependencies = [
+ "derivative",
  "rustc_apfloat",
  "rustc_arena",
  "rustc_data_structures",

compiler/rustc_ast/src/ast.rs

@@ -286,41 +286,16 @@ impl ParenthesizedArgs {
 
 pub use crate::node_id::{NodeId, CRATE_NODE_ID, DUMMY_NODE_ID};
 
-/// A modifier on a bound, e.g., `?Trait` or `~const Trait`.
-///
-/// Negative bounds should also be handled here.
+/// Modifiers on a trait bound like `~const`, `?` and `!`.
 #[derive(Copy, Clone, PartialEq, Eq, Encodable, Decodable, Debug)]
-pub enum TraitBoundModifier {
-    /// No modifiers
-    None,
-
-    /// `!Trait`
-    Negative,
-
-    /// `?Trait`
-    Maybe,
-
-    /// `~const Trait`
-    MaybeConst(Span),
-
-    /// `~const !Trait`
-    //
-    // This parses but will be rejected during AST validation.
-    MaybeConstNegative,
-
-    /// `~const ?Trait`
-    //
-    // This parses but will be rejected during AST validation.
-    MaybeConstMaybe,
+pub struct TraitBoundModifiers {
+    pub constness: BoundConstness,
+    pub polarity: BoundPolarity,
 }
 
-impl TraitBoundModifier {
-    pub fn to_constness(self) -> Const {
-        match self {
-            Self::MaybeConst(span) => Const::Yes(span),
-            _ => Const::No,
-        }
-    }
+impl TraitBoundModifiers {
+    pub const NONE: Self =
+        Self { constness: BoundConstness::Never, polarity: BoundPolarity::Positive };
 }
 
 /// The AST represents all type param bounds as types.
@@ -329,7 +304,7 @@ impl TraitBoundModifier {
 /// detects `Copy`, `Send` and `Sync`.
 #[derive(Clone, Encodable, Decodable, Debug)]
 pub enum GenericBound {
-    Trait(PolyTraitRef, TraitBoundModifier),
+    Trait(PolyTraitRef, TraitBoundModifiers),
     Outlives(Lifetime),
 }
 
@@ -779,8 +754,7 @@ pub enum PatKind {
     Ident(BindingAnnotation, Ident, Option<P<Pat>>),
 
     /// A struct or struct variant pattern (e.g., `Variant {x, y, ..}`).
-    /// The `bool` is `true` in the presence of a `..`.
-    Struct(Option<P<QSelf>>, Path, ThinVec<PatField>, /* recovered */ bool),
+    Struct(Option<P<QSelf>>, Path, ThinVec<PatField>, PatFieldsRest),
 
     /// A tuple struct/variant pattern (`Variant(x, y, .., z)`).
     TupleStruct(Option<P<QSelf>>, Path, ThinVec<P<Pat>>),
@@ -837,6 +811,15 @@ pub enum PatKind {
     MacCall(P<MacCall>),
 }
 
+/// Whether the `..` is present in a struct fields pattern.
+#[derive(Clone, Copy, Encodable, Decodable, Debug, PartialEq)]
+pub enum PatFieldsRest {
+    /// `module::StructName { field, ..}`
+    Rest,
+    /// `module::StructName { field }`
+    None,
+}
+
 /// The kind of borrow in an `AddrOf` expression,
 /// e.g., `&place` or `&raw const place`.
 #[derive(Clone, Copy, PartialEq, Eq, Debug)]
@@ -1193,7 +1176,7 @@ impl Expr {
         match &self.kind {
             ExprKind::Path(None, path) => Some(GenericBound::Trait(
                 PolyTraitRef::new(ThinVec::new(), path.clone(), self.span),
-                TraitBoundModifier::None,
+                TraitBoundModifiers::NONE,
             )),
             _ => None,
         }
@@ -1274,7 +1257,7 @@ impl Expr {
             ExprKind::Let(..) => ExprPrecedence::Let,
             ExprKind::If(..) => ExprPrecedence::If,
             ExprKind::While(..) => ExprPrecedence::While,
-            ExprKind::ForLoop(..) => ExprPrecedence::ForLoop,
+            ExprKind::ForLoop { .. } => ExprPrecedence::ForLoop,
             ExprKind::Loop(..) => ExprPrecedence::Loop,
             ExprKind::Match(..) => ExprPrecedence::Match,
             ExprKind::Closure(..) => ExprPrecedence::Closure,
@@ -1436,10 +1419,10 @@ pub enum ExprKind {
     While(P<Expr>, P<Block>, Option<Label>),
     /// A `for` loop, with an optional label.
     ///
-    /// `'label: for pat in expr { block }`
+    /// `'label: for await? pat in iter { block }`
     ///
     /// This is desugared to a combination of `loop` and `match` expressions.
-    ForLoop(P<Pat>, P<Expr>, P<Block>, Option<Label>),
+    ForLoop { pat: P<Pat>, iter: P<Expr>, body: P<Block>, label: Option<Label>, kind: ForLoopKind },
     /// Conditionless loop (can be exited with `break`, `continue`, or `return`).
     ///
     /// `'label: loop { block }`
@@ -1542,6 +1525,13 @@ pub enum ExprKind {
     Err,
 }
 
+/// Used to differentiate between `for` loops and `for await` loops.
+#[derive(Clone, Copy, Encodable, Decodable, Debug, PartialEq, Eq)]
+pub enum ForLoopKind {
+    For,
+    ForAwait,
+}
+
 /// Used to differentiate between `async {}` blocks and `gen {}` blocks.
 #[derive(Clone, Encodable, Decodable, Debug, PartialEq, Eq)]
 pub enum GenBlockKind {
@@ -2491,6 +2481,15 @@ pub enum Const {
     No,
 }
 
+impl From<BoundConstness> for Const {
+    fn from(constness: BoundConstness) -> Self {
+        match constness {
+            BoundConstness::Maybe(span) => Self::Yes(span),
+            BoundConstness::Never => Self::No,
+        }
+    }
+}
+
 /// Item defaultness.
 /// For details see the [RFC #2532](https://github.com/rust-lang/rfcs/pull/2532).
 #[derive(Copy, Clone, PartialEq, Encodable, Decodable, Debug, HashStable_Generic)]
@@ -2516,7 +2515,9 @@ impl fmt::Debug for ImplPolarity {
     }
 }
 
-#[derive(Copy, Clone, PartialEq, Encodable, Decodable, HashStable_Generic)]
+/// The polarity of a trait bound.
+#[derive(Copy, Clone, PartialEq, Eq, Encodable, Decodable, Debug)]
+#[derive(HashStable_Generic)]
 pub enum BoundPolarity {
     /// `Type: Trait`
     Positive,
@@ -2526,6 +2527,35 @@ pub enum BoundPolarity {
     Maybe(Span),
 }
 
+impl BoundPolarity {
+    pub fn as_str(self) -> &'static str {
+        match self {
+            Self::Positive => "",
+            Self::Negative(_) => "!",
+            Self::Maybe(_) => "?",
+        }
+    }
+}
+
+/// The constness of a trait bound.
+#[derive(Copy, Clone, PartialEq, Eq, Encodable, Decodable, Debug)]
+#[derive(HashStable_Generic)]
+pub enum BoundConstness {
+    /// `Type: Trait`
+    Never,
+    /// `Type: ~const Trait`
+    Maybe(Span),
+}
+
+impl BoundConstness {
+    pub fn as_str(self) -> &'static str {
+        match self {
+            Self::Never => "",
+            Self::Maybe(_) => "~const",
+        }
+    }
+}
+
 #[derive(Clone, Encodable, Decodable, Debug)]
 pub enum FnRetTy {
     /// Returns type is not specified.
@@ -3259,7 +3289,7 @@ mod size_asserts {
     static_assert_size!(ForeignItem, 96);
     static_assert_size!(ForeignItemKind, 24);
     static_assert_size!(GenericArg, 24);
-    static_assert_size!(GenericBound, 64);
+    static_assert_size!(GenericBound, 72);
     static_assert_size!(Generics, 40);
     static_assert_size!(Impl, 136);
     static_assert_size!(Item, 136);

compiler/rustc_ast/src/mut_visit.rs

@@ -1389,7 +1389,7 @@ pub fn noop_visit_expr<T: MutVisitor>(
             vis.visit_block(body);
             visit_opt(label, |label| vis.visit_label(label));
         }
-        ExprKind::ForLoop(pat, iter, body, label) => {
+        ExprKind::ForLoop { pat, iter, body, label, kind: _ } => {
             vis.visit_pat(pat);
             vis.visit_expr(iter);
             vis.visit_block(body);

compiler/rustc_ast/src/util/classify.rs

@@ -19,7 +19,7 @@ pub fn expr_requires_semi_to_be_stmt(e: &ast::Expr) -> bool {
             | ast::ExprKind::Block(..)
             | ast::ExprKind::While(..)
             | ast::ExprKind::Loop(..)
-            | ast::ExprKind::ForLoop(..)
+            | ast::ExprKind::ForLoop { .. }
             | ast::ExprKind::TryBlock(..)
             | ast::ExprKind::ConstBlock(..)
     )
@@ -48,8 +48,16 @@ pub fn expr_trailing_brace(mut expr: &ast::Expr) -> Option<&ast::Expr> {
             Closure(closure) => {
                 expr = &closure.body;
             }
-            Gen(..) | Block(..) | ForLoop(..) | If(..) | Loop(..) | Match(..) | Struct(..)
-            | TryBlock(..) | While(..) | ConstBlock(_) => break Some(expr),
+            Gen(..)
+            | Block(..)
+            | ForLoop { .. }
+            | If(..)
+            | Loop(..)
+            | Match(..)
+            | Struct(..)
+            | TryBlock(..)
+            | While(..)
+            | ConstBlock(_) => break Some(expr),
 
             // FIXME: These can end in `}`, but changing these would break stable code.
             InlineAsm(_) | OffsetOf(_, _) | MacCall(_) | IncludedBytes(_) | FormatArgs(_) => {

compiler/rustc_ast/src/visit.rs

@@ -844,11 +844,11 @@ pub fn walk_expr<'a, V: Visitor<'a>>(visitor: &mut V, expression: &'a Expr) {
             visitor.visit_expr(subexpression);
             visitor.visit_block(block);
         }
-        ExprKind::ForLoop(pattern, subexpression, block, opt_label) => {
-            walk_list!(visitor, visit_label, opt_label);
-            visitor.visit_pat(pattern);
-            visitor.visit_expr(subexpression);
-            visitor.visit_block(block);
+        ExprKind::ForLoop { pat, iter, body, label, kind: _ } => {
+            walk_list!(visitor, visit_label, label);
+            visitor.visit_pat(pat);
+            visitor.visit_expr(iter);
+            visitor.visit_block(body);
         }
         ExprKind::Loop(block, opt_label, _) => {
             walk_list!(visitor, visit_label, opt_label);

compiler/rustc_ast_lowering/src/expr.rs

@@ -56,12 +56,12 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     return ex;
                 }
                 // Desugar `ExprForLoop`
-                // from: `[opt_ident]: for <pat> in <head> <body>`
+                // from: `[opt_ident]: for await? <pat> in <iter> <body>`
                 //
                 // This also needs special handling because the HirId of the returned `hir::Expr` will not
                 // correspond to the `e.id`, so `lower_expr_for` handles attribute lowering itself.
-                ExprKind::ForLoop(pat, head, body, opt_label) => {
-                    return self.lower_expr_for(e, pat, head, body, *opt_label);
+                ExprKind::ForLoop { pat, iter, body, label, kind } => {
+                    return self.lower_expr_for(e, pat, iter, body, *label, *kind);
                 }
                 _ => (),
             }
@@ -337,7 +337,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 ),
                 ExprKind::Try(sub_expr) => self.lower_expr_try(e.span, sub_expr),
 
-                ExprKind::Paren(_) | ExprKind::ForLoop(..) => {
+                ExprKind::Paren(_) | ExprKind::ForLoop { .. } => {
                     unreachable!("already handled")
                 }
 
@@ -670,7 +670,10 @@ impl<'hir> LoweringContext<'_, 'hir> {
         let params = arena_vec![self; param];
 
         let body = self.lower_body(move |this| {
-            this.coroutine_kind = Some(hir::CoroutineKind::Async(async_coroutine_source));
+            this.coroutine_kind = Some(hir::CoroutineKind::Desugared(
+                hir::CoroutineDesugaring::Async,
+                async_coroutine_source,
+            ));
 
             let old_ctx = this.task_context;
             this.task_context = Some(task_context_hid);
@@ -724,7 +727,10 @@ impl<'hir> LoweringContext<'_, 'hir> {
         });
 
         let body = self.lower_body(move |this| {
-            this.coroutine_kind = Some(hir::CoroutineKind::Gen(coroutine_source));
+            this.coroutine_kind = Some(hir::CoroutineKind::Desugared(
+                hir::CoroutineDesugaring::Gen,
+                coroutine_source,
+            ));
 
             let res = body(this);
             (&[], res)
@@ -802,7 +808,10 @@ impl<'hir> LoweringContext<'_, 'hir> {
         let params = arena_vec![self; param];
 
         let body = self.lower_body(move |this| {
-            this.coroutine_kind = Some(hir::CoroutineKind::AsyncGen(async_coroutine_source));
+            this.coroutine_kind = Some(hir::CoroutineKind::Desugared(
+                hir::CoroutineDesugaring::AsyncGen,
+                async_coroutine_source,
+            ));
 
             let old_ctx = this.task_context;
             this.task_context = Some(task_context_hid);
@@ -874,12 +883,25 @@ impl<'hir> LoweringContext<'_, 'hir> {
     /// }
     /// ```
     fn lower_expr_await(&mut self, await_kw_span: Span, expr: &Expr) -> hir::ExprKind<'hir> {
+        let expr = self.arena.alloc(self.lower_expr_mut(expr));
+        self.make_lowered_await(await_kw_span, expr, FutureKind::Future)
+    }
+
+    /// Takes an expr that has already been lowered and generates a desugared await loop around it
+    fn make_lowered_await(
+        &mut self,
+        await_kw_span: Span,
+        expr: &'hir hir::Expr<'hir>,
+        await_kind: FutureKind,
+    ) -> hir::ExprKind<'hir> {
         let full_span = expr.span.to(await_kw_span);
 
         let is_async_gen = match self.coroutine_kind {
-            Some(hir::CoroutineKind::Async(_)) => false,
-            Some(hir::CoroutineKind::AsyncGen(_)) => true,
-            Some(hir::CoroutineKind::Coroutine) | Some(hir::CoroutineKind::Gen(_)) | None => {
+            Some(hir::CoroutineKind::Desugared(hir::CoroutineDesugaring::Async, _)) => false,
+            Some(hir::CoroutineKind::Desugared(hir::CoroutineDesugaring::AsyncGen, _)) => true,
+            Some(hir::CoroutineKind::Coroutine)
+            | Some(hir::CoroutineKind::Desugared(hir::CoroutineDesugaring::Gen, _))
+            | None => {
                 return hir::ExprKind::Err(self.tcx.sess.emit_err(AwaitOnlyInAsyncFnAndBlocks {
                     await_kw_span,
                     item_span: self.current_item,
@@ -887,13 +909,16 @@ impl<'hir> LoweringContext<'_, 'hir> {
             }
         };
 
-        let span = self.mark_span_with_reason(DesugaringKind::Await, await_kw_span, None);
+        let features = match await_kind {
+            FutureKind::Future => None,
+            FutureKind::AsyncIterator => Some(self.allow_for_await.clone()),
+        };
+        let span = self.mark_span_with_reason(DesugaringKind::Await, await_kw_span, features);
         let gen_future_span = self.mark_span_with_reason(
             DesugaringKind::Await,
             full_span,
             Some(self.allow_gen_future.clone()),
         );
-        let expr = self.lower_expr_mut(expr);
         let expr_hir_id = expr.hir_id;
 
         // Note that the name of this binding must not be changed to something else because
@@ -934,11 +959,18 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 hir::LangItem::GetContext,
                 arena_vec![self; task_context],
             );
-            let call = self.expr_call_lang_item_fn(
-                span,
-                hir::LangItem::FuturePoll,
-                arena_vec![self; new_unchecked, get_context],
-            );
+            let call = match await_kind {
+                FutureKind::Future => self.expr_call_lang_item_fn(
+                    span,
+                    hir::LangItem::FuturePoll,
+                    arena_vec![self; new_unchecked, get_context],
+                ),
+                FutureKind::AsyncIterator => self.expr_call_lang_item_fn(
+                    span,
+                    hir::LangItem::AsyncIteratorPollNext,
+                    arena_vec![self; new_unchecked, get_context],
+                ),
+            };
             self.arena.alloc(self.expr_unsafe(call))
         };
 
@@ -1020,11 +1052,16 @@ impl<'hir> LoweringContext<'_, 'hir> {
         let awaitee_arm = self.arm(awaitee_pat, loop_expr);
 
         // `match ::std::future::IntoFuture::into_future(<expr>) { ... }`
-        let into_future_expr = self.expr_call_lang_item_fn(
-            span,
-            hir::LangItem::IntoFutureIntoFuture,
-            arena_vec![self; expr],
-        );
+        let into_future_expr = match await_kind {
+            FutureKind::Future => self.expr_call_lang_item_fn(
+                span,
+                hir::LangItem::IntoFutureIntoFuture,
+                arena_vec![self; *expr],
+            ),
+            // Not needed for `for await` because we expect to have already called
+            // `IntoAsyncIterator::into_async_iter` on it.
+            FutureKind::AsyncIterator => expr,
+        };
 
         // match <into_future_expr> {
         //     mut __awaitee => loop { .. }
@@ -1097,9 +1134,9 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 Some(movability)
             }
             Some(
-                hir::CoroutineKind::Gen(_)
-                | hir::CoroutineKind::Async(_)
-                | hir::CoroutineKind::AsyncGen(_),
+                hir::CoroutineKind::Desugared(hir::CoroutineDesugaring::Gen, _)
+                | hir::CoroutineKind::Desugared(hir::CoroutineDesugaring::Async, _)
+                | hir::CoroutineKind::Desugared(hir::CoroutineDesugaring::AsyncGen, _),
             ) => {
                 panic!("non-`async`/`gen` closure body turned `async`/`gen` during lowering");
             }
@@ -1612,9 +1649,9 @@ impl<'hir> LoweringContext<'_, 'hir> {
 
     fn lower_expr_yield(&mut self, span: Span, opt_expr: Option<&Expr>) -> hir::ExprKind<'hir> {
         let is_async_gen = match self.coroutine_kind {
-            Some(hir::CoroutineKind::Gen(_)) => false,
-            Some(hir::CoroutineKind::AsyncGen(_)) => true,
-            Some(hir::CoroutineKind::Async(_)) => {
+            Some(hir::CoroutineKind::Desugared(hir::CoroutineDesugaring::Gen, _)) => false,
+            Some(hir::CoroutineKind::Desugared(hir::CoroutineDesugaring::AsyncGen, _)) => true,
+            Some(hir::CoroutineKind::Desugared(hir::CoroutineDesugaring::Async, _)) => {
                 return hir::ExprKind::Err(
                     self.tcx.sess.emit_err(AsyncCoroutinesNotSupported { span }),
                 );
@@ -1685,6 +1722,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
         head: &Expr,
         body: &Block,
         opt_label: Option<Label>,
+        loop_kind: ForLoopKind,
     ) -> hir::Expr<'hir> {
         let head = self.lower_expr_mut(head);
         let pat = self.lower_pat(pat);
@@ -1713,17 +1751,41 @@ impl<'hir> LoweringContext<'_, 'hir> {
         let (iter_pat, iter_pat_nid) =
             self.pat_ident_binding_mode(head_span, iter, hir::BindingAnnotation::MUT);
 
-        // `match Iterator::next(&mut iter) { ... }`
         let match_expr = {
             let iter = self.expr_ident(head_span, iter, iter_pat_nid);
-            let ref_mut_iter = self.expr_mut_addr_of(head_span, iter);
-            let next_expr = self.expr_call_lang_item_fn(
-                head_span,
-                hir::LangItem::IteratorNext,
-                arena_vec![self; ref_mut_iter],
-            );
+            let next_expr = match loop_kind {
+                ForLoopKind::For => {
+                    // `Iterator::next(&mut iter)`
+                    let ref_mut_iter = self.expr_mut_addr_of(head_span, iter);
+                    self.expr_call_lang_item_fn(
+                        head_span,
+                        hir::LangItem::IteratorNext,
+                        arena_vec![self; ref_mut_iter],
+                    )
+                }
+                ForLoopKind::ForAwait => {
+                    // we'll generate `unsafe { Pin::new_unchecked(&mut iter) })` and then pass this
+                    // to make_lowered_await with `FutureKind::AsyncIterator` which will generator
+                    // calls to `poll_next`. In user code, this would probably be a call to
+                    // `Pin::as_mut` but here it's easy enough to do `new_unchecked`.
+
+                    // `&mut iter`
+                    let iter = self.expr_mut_addr_of(head_span, iter);
+                    // `Pin::new_unchecked(...)`
+                    let iter = self.arena.alloc(self.expr_call_lang_item_fn_mut(
+                        head_span,
+                        hir::LangItem::PinNewUnchecked,
+                        arena_vec![self; iter],
+                    ));
+                    // `unsafe { ... }`
+                    let iter = self.arena.alloc(self.expr_unsafe(iter));
+                    let kind = self.make_lowered_await(head_span, iter, FutureKind::AsyncIterator);
+                    self.arena.alloc(hir::Expr { hir_id: self.next_id(), kind, span: head_span })
+                }
+            };
             let arms = arena_vec![self; none_arm, some_arm];
 
+            // `match $next_expr { ... }`
             self.expr_match(head_span, next_expr, arms, hir::MatchSource::ForLoopDesugar)
         };
         let match_stmt = self.stmt_expr(for_span, match_expr);
@@ -1743,13 +1805,34 @@ impl<'hir> LoweringContext<'_, 'hir> {
         // `mut iter => { ... }`
         let iter_arm = self.arm(iter_pat, loop_expr);
 
-        // `match ::std::iter::IntoIterator::into_iter(<head>) { ... }`
-        let into_iter_expr = {
-            self.expr_call_lang_item_fn(
-                head_span,
-                hir::LangItem::IntoIterIntoIter,
-                arena_vec![self; head],
-            )
+        let into_iter_expr = match loop_kind {
+            ForLoopKind::For => {
+                // `::std::iter::IntoIterator::into_iter(<head>)`
+                self.expr_call_lang_item_fn(
+                    head_span,
+                    hir::LangItem::IntoIterIntoIter,
+                    arena_vec![self; head],
+                )
+            }
+            // ` unsafe { Pin::new_unchecked(&mut into_async_iter(<head>)) }`
+            ForLoopKind::ForAwait => {
+                // `::core::async_iter::IntoAsyncIterator::into_async_iter(<head>)`
+                let iter = self.expr_call_lang_item_fn(
+                    head_span,
+                    hir::LangItem::IntoAsyncIterIntoIter,
+                    arena_vec![self; head],
+                );
+                let iter = self.expr_mut_addr_of(head_span, iter);
+                // `Pin::new_unchecked(...)`
+                let iter = self.arena.alloc(self.expr_call_lang_item_fn_mut(
+                    head_span,
+                    hir::LangItem::PinNewUnchecked,
+                    arena_vec![self; iter],
+                ));
+                // `unsafe { ... }`
+                let iter = self.arena.alloc(self.expr_unsafe(iter));
+                iter
+            }
         };
 
         let match_expr = self.arena.alloc(self.expr_match(
@@ -2152,3 +2235,14 @@ impl<'hir> LoweringContext<'_, 'hir> {
         }
     }
 }
+
+/// Used by [`LoweringContext::make_lowered_await`] to customize the desugaring based on what kind
+/// of future we are awaiting.
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+enum FutureKind {
+    /// We are awaiting a normal future
+    Future,
+    /// We are awaiting something that's known to be an AsyncIterator (i.e. we are in the header of
+    /// a `for await` loop)
+    AsyncIterator,
+}

compiler/rustc_ast_lowering/src/item.rs

@@ -1372,7 +1372,13 @@ impl<'hir> LoweringContext<'_, 'hir> {
             // need to compute this at all unless there is a Maybe bound.
             let mut is_param: Option<bool> = None;
             for bound in &bound_pred.bounds {
-                if !matches!(*bound, GenericBound::Trait(_, TraitBoundModifier::Maybe)) {
+                if !matches!(
+                    *bound,
+                    GenericBound::Trait(
+                        _,
+                        TraitBoundModifiers { polarity: BoundPolarity::Maybe(_), .. }
+                    )
+                ) {
                     continue;
                 }
                 let is_param = *is_param.get_or_insert_with(compute_is_param);

compiler/rustc_ast_lowering/src/lib.rs

@@ -130,6 +130,7 @@ struct LoweringContext<'a, 'hir> {
     allow_try_trait: Lrc<[Symbol]>,
     allow_gen_future: Lrc<[Symbol]>,
     allow_async_iterator: Lrc<[Symbol]>,
+    allow_for_await: 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
@@ -174,6 +175,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
             } else {
                 [sym::gen_future].into()
             },
+            allow_for_await: [sym::async_iterator].into(),
             // FIXME(gen_blocks): how does `closure_track_caller`/`async_fn_track_caller`
             // interact with `gen`/`async gen` blocks
             allow_async_iterator: [sym::gen_future, sym::async_iterator].into(),
@@ -1425,19 +1427,16 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                         this.arena.alloc_from_iter(bounds.iter().filter_map(|bound| match bound {
                             GenericBound::Trait(
                                 ty,
-                                modifier @ (TraitBoundModifier::None
-                                | TraitBoundModifier::MaybeConst(_)
-                                | TraitBoundModifier::Negative),
-                            ) => {
-                                Some(this.lower_poly_trait_ref(ty, itctx, modifier.to_constness()))
-                            }
-                            // `~const ?Bound` will cause an error during AST validation
-                            // anyways, so treat it like `?Bound` as compilation proceeds.
+                                TraitBoundModifiers {
+                                    polarity: BoundPolarity::Positive | BoundPolarity::Negative(_),
+                                    constness,
+                                },
+                            ) => Some(this.lower_poly_trait_ref(ty, itctx, (*constness).into())),
+                            // We can safely ignore constness here, since AST validation
+                            // will take care of invalid modifier combinations.
                             GenericBound::Trait(
                                 _,
-                                TraitBoundModifier::Maybe
-                                | TraitBoundModifier::MaybeConstMaybe
-                                | TraitBoundModifier::MaybeConstNegative,
+                                TraitBoundModifiers { polarity: BoundPolarity::Maybe(_), .. },
                             ) => None,
                             GenericBound::Outlives(lifetime) => {
                                 if lifetime_bound.is_none() {
@@ -2028,9 +2027,9 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         itctx: &ImplTraitContext,
     ) -> hir::GenericBound<'hir> {
         match tpb {
-            GenericBound::Trait(p, modifier) => hir::GenericBound::Trait(
-                self.lower_poly_trait_ref(p, itctx, modifier.to_constness()),
-                self.lower_trait_bound_modifier(*modifier),
+            GenericBound::Trait(p, modifiers) => hir::GenericBound::Trait(
+                self.lower_poly_trait_ref(p, itctx, modifiers.constness.into()),
+                self.lower_trait_bound_modifiers(*modifiers),
             ),
             GenericBound::Outlives(lifetime) => {
                 hir::GenericBound::Outlives(self.lower_lifetime(lifetime))
@@ -2316,25 +2315,29 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         }
     }
 
-    fn lower_trait_bound_modifier(&mut self, f: TraitBoundModifier) -> hir::TraitBoundModifier {
-        match f {
-            TraitBoundModifier::None => hir::TraitBoundModifier::None,
-            TraitBoundModifier::MaybeConst(_) => hir::TraitBoundModifier::MaybeConst,
-
-            TraitBoundModifier::Negative => {
+    fn lower_trait_bound_modifiers(
+        &mut self,
+        modifiers: TraitBoundModifiers,
+    ) -> hir::TraitBoundModifier {
+        match (modifiers.constness, modifiers.polarity) {
+            (BoundConstness::Never, BoundPolarity::Positive) => hir::TraitBoundModifier::None,
+            (BoundConstness::Never, BoundPolarity::Maybe(_)) => hir::TraitBoundModifier::Maybe,
+            (BoundConstness::Never, BoundPolarity::Negative(_)) => {
                 if self.tcx.features().negative_bounds {
                     hir::TraitBoundModifier::Negative
                 } else {
                     hir::TraitBoundModifier::None
                 }
             }
-
-            // `MaybeConstMaybe` will cause an error during AST validation, but we need to pick a
-            // placeholder for compilation to proceed.
-            TraitBoundModifier::MaybeConstMaybe | TraitBoundModifier::Maybe => {
-                hir::TraitBoundModifier::Maybe
+            (BoundConstness::Maybe(_), BoundPolarity::Positive) => {
+                hir::TraitBoundModifier::MaybeConst
+            }
+            // Invalid modifier combinations will cause an error during AST validation.
+            // Arbitrarily pick a placeholder for compilation to proceed.
+            (BoundConstness::Maybe(_), BoundPolarity::Maybe(_)) => hir::TraitBoundModifier::Maybe,
+            (BoundConstness::Maybe(_), BoundPolarity::Negative(_)) => {
+                hir::TraitBoundModifier::MaybeConst
             }
-            TraitBoundModifier::MaybeConstNegative => hir::TraitBoundModifier::MaybeConst,
         }
     }
 

compiler/rustc_ast_lowering/src/pat.rs

@@ -82,7 +82,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                                 span: self.lower_span(f.span),
                             }
                         }));
-                        break hir::PatKind::Struct(qpath, fs, *etc);
+                        break hir::PatKind::Struct(qpath, fs, *etc == ast::PatFieldsRest::Rest);
                     }
                     PatKind::Tuple(pats) => {
                         let (pats, ddpos) = self.lower_pat_tuple(pats, "tuple");

compiler/rustc_ast_passes/messages.ftl

@@ -152,6 +152,8 @@ ast_passes_impl_trait_path = `impl Trait` is not allowed in path parameters
 ast_passes_incompatible_features = `{$f1}` and `{$f2}` are incompatible, using them at the same time is not allowed
     .help = remove one of these features
 
+ast_passes_incompatible_trait_bound_modifiers = `{$left}` and `{$right}` are mutually exclusive
+
 ast_passes_inherent_cannot_be = inherent impls cannot be {$annotation}
     .because = {$annotation} because of this
     .type = inherent impl for this type
@@ -195,8 +197,6 @@ ast_passes_nomangle_ascii = `#[no_mangle]` requires ASCII identifier
 ast_passes_obsolete_auto = `impl Trait for .. {"{}"}` is an obsolete syntax
     .help = use `auto trait Trait {"{}"}` instead
 
-ast_passes_optional_const_exclusive = `~const` and `{$modifier}` are mutually exclusive
-
 ast_passes_optional_trait_object = `?Trait` is not permitted in trait object types
 
 ast_passes_optional_trait_supertrait = `?Trait` is not permitted in supertraits

compiler/rustc_ast_passes/src/ast_validation.rs

@@ -1196,18 +1196,18 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
     }
 
     fn visit_param_bound(&mut self, bound: &'a GenericBound, ctxt: BoundKind) {
-        if let GenericBound::Trait(poly, modify) = bound {
-            match (ctxt, modify) {
-                (BoundKind::SuperTraits, TraitBoundModifier::Maybe) => {
+        if let GenericBound::Trait(poly, modifiers) = bound {
+            match (ctxt, modifiers.constness, modifiers.polarity) {
+                (BoundKind::SuperTraits, BoundConstness::Never, BoundPolarity::Maybe(_)) => {
                     self.dcx().emit_err(errors::OptionalTraitSupertrait {
                         span: poly.span,
                         path_str: pprust::path_to_string(&poly.trait_ref.path),
                     });
                 }
-                (BoundKind::TraitObject, TraitBoundModifier::Maybe) => {
+                (BoundKind::TraitObject, BoundConstness::Never, BoundPolarity::Maybe(_)) => {
                     self.dcx().emit_err(errors::OptionalTraitObject { span: poly.span });
                 }
-                (_, &TraitBoundModifier::MaybeConst(span))
+                (_, BoundConstness::Maybe(span), BoundPolarity::Positive)
                     if let Some(reason) = &self.disallow_tilde_const =>
                 {
                     let reason = match reason {
@@ -1235,16 +1235,15 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
                     };
                     self.dcx().emit_err(errors::TildeConstDisallowed { span, reason });
                 }
-                (_, TraitBoundModifier::MaybeConstMaybe) => {
-                    self.dcx().emit_err(errors::OptionalConstExclusive {
+                (
+                    _,
+                    BoundConstness::Maybe(_),
+                    BoundPolarity::Maybe(_) | BoundPolarity::Negative(_),
+                ) => {
+                    self.dcx().emit_err(errors::IncompatibleTraitBoundModifiers {
                         span: bound.span(),
-                        modifier: "?",
-                    });
-                }
-                (_, TraitBoundModifier::MaybeConstNegative) => {
-                    self.dcx().emit_err(errors::OptionalConstExclusive {
-                        span: bound.span(),
-                        modifier: "!",
+                        left: modifiers.constness.as_str(),
+                        right: modifiers.polarity.as_str(),
                     });
                 }
                 _ => {}
@@ -1252,7 +1251,8 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
         }
 
         // Negative trait bounds are not allowed to have associated constraints
-        if let GenericBound::Trait(trait_ref, TraitBoundModifier::Negative) = bound
+        if let GenericBound::Trait(trait_ref, modifiers) = bound
+            && let BoundPolarity::Negative(_) = modifiers.polarity
             && let Some(segment) = trait_ref.trait_ref.path.segments.last()
             && let Some(ast::GenericArgs::AngleBracketed(args)) = segment.args.as_deref()
         {
@@ -1494,7 +1494,8 @@ fn deny_equality_constraints(
             for param in &generics.params {
                 if param.ident == potential_param.ident {
                     for bound in &param.bounds {
-                        if let ast::GenericBound::Trait(trait_ref, TraitBoundModifier::None) = bound
+                        if let ast::GenericBound::Trait(trait_ref, TraitBoundModifiers::NONE) =
+                            bound
                         {
                             if let [trait_segment] = &trait_ref.trait_ref.path.segments[..] {
                                 let assoc = pprust::path_to_string(&ast::Path::from_ident(

compiler/rustc_ast_passes/src/errors.rs

@@ -580,11 +580,12 @@ pub enum TildeConstReason {
 }
 
 #[derive(Diagnostic)]
-#[diag(ast_passes_optional_const_exclusive)]
-pub struct OptionalConstExclusive {
+#[diag(ast_passes_incompatible_trait_bound_modifiers)]
+pub struct IncompatibleTraitBoundModifiers {
     #[primary_span]
     pub span: Span,
-    pub modifier: &'static str,
+    pub left: &'static str,
+    pub right: &'static str,
 }
 
 #[derive(Diagnostic)]

compiler/rustc_ast_passes/src/feature_gate.rs

@@ -527,6 +527,7 @@ pub fn check_crate(krate: &ast::Crate, sess: &Session, features: &Features) {
         "async closures are unstable",
         "to use an async block, remove the `||`: `async {`"
     );
+    gate_all!(async_for_loop, "`for await` loops are experimental");
     gate_all!(
         closure_lifetime_binder,
         "`for<...>` binders for closures are experimental",

compiler/rustc_ast_pretty/src/lib.rs

@@ -4,6 +4,7 @@
 #![deny(rustc::untranslatable_diagnostic)]
 #![deny(rustc::diagnostic_outside_of_impl)]
 #![feature(box_patterns)]
+#![feature(let_chains)]
 #![recursion_limit = "256"]
 
 mod helpers;

compiler/rustc_ast_pretty/src/pprust/state.rs

@@ -17,7 +17,7 @@ use rustc_ast::util::comments::{gather_comments, Comment, CommentStyle};
 use rustc_ast::util::parser;
 use rustc_ast::{self as ast, AttrArgs, AttrArgsEq, BlockCheckMode, PatKind};
 use rustc_ast::{attr, BindingAnnotation, ByRef, DelimArgs, RangeEnd, RangeSyntax, Term};
-use rustc_ast::{GenericArg, GenericBound, SelfKind, TraitBoundModifier};
+use rustc_ast::{GenericArg, GenericBound, SelfKind};
 use rustc_ast::{InlineAsmOperand, InlineAsmRegOrRegClass};
 use rustc_ast::{InlineAsmOptions, InlineAsmTemplatePiece};
 use rustc_span::edition::Edition;
@@ -1427,7 +1427,7 @@ impl<'a> State<'a> {
                 }
                 self.nbsp();
                 self.word("{");
-                let empty = fields.is_empty() && !etc;
+                let empty = fields.is_empty() && *etc == ast::PatFieldsRest::None;
                 if !empty {
                     self.space();
                 }
@@ -1445,7 +1445,7 @@ impl<'a> State<'a> {
                     },
                     |f| f.pat.span,
                 );
-                if *etc {
+                if *etc == ast::PatFieldsRest::Rest {
                     if !fields.is_empty() {
                         self.word_space(",");
                     }
@@ -1559,26 +1559,20 @@ impl<'a> State<'a> {
 
             match bound {
                 GenericBound::Trait(tref, modifier) => {
-                    match modifier {
-                        TraitBoundModifier::None => {}
-                        TraitBoundModifier::Negative => {
-                            self.word("!");
-                        }
-                        TraitBoundModifier::Maybe => {
-                            self.word("?");
-                        }
-                        TraitBoundModifier::MaybeConst(_) => {
-                            self.word_space("~const");
-                        }
-                        TraitBoundModifier::MaybeConstNegative => {
-                            self.word_space("~const");
-                            self.word("!");
-                        }
-                        TraitBoundModifier::MaybeConstMaybe => {
-                            self.word_space("~const");
-                            self.word("?");
+                    match modifier.constness {
+                        ast::BoundConstness::Never => {}
+                        ast::BoundConstness::Maybe(_) => {
+                            self.word_space(modifier.constness.as_str());
                         }
                     }
+
+                    match modifier.polarity {
+                        ast::BoundPolarity::Positive => {}
+                        ast::BoundPolarity::Negative(_) | ast::BoundPolarity::Maybe(_) => {
+                            self.word(modifier.polarity.as_str());
+                        }
+                    }
+
                     self.print_poly_trait_ref(tref);
                 }
                 GenericBound::Outlives(lt) => self.print_lifetime(*lt),

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

@@ -1,5 +1,6 @@
 use crate::pp::Breaks::Inconsistent;
 use crate::pprust::state::{AnnNode, PrintState, State, INDENT_UNIT};
+use ast::ForLoopKind;
 use itertools::{Itertools, Position};
 use rustc_ast::ptr::P;
 use rustc_ast::token;
@@ -418,20 +419,23 @@ impl<'a> State<'a> {
                 self.space();
                 self.print_block_with_attrs(blk, attrs);
             }
-            ast::ExprKind::ForLoop(pat, iter, blk, opt_label) => {
-                if let Some(label) = opt_label {
+            ast::ExprKind::ForLoop { pat, iter, body, label, kind } => {
+                if let Some(label) = label {
                     self.print_ident(label.ident);
                     self.word_space(":");
                 }
                 self.cbox(0);
                 self.ibox(0);
                 self.word_nbsp("for");
+                if kind == &ForLoopKind::ForAwait {
+                    self.word_nbsp("await");
+                }
                 self.print_pat(pat);
                 self.space();
                 self.word_space("in");
                 self.print_expr_as_cond(iter);
                 self.space();
-                self.print_block_with_attrs(blk, attrs);
+                self.print_block_with_attrs(body, attrs);
             }
             ast::ExprKind::Loop(blk, opt_label, _) => {
                 if let Some(label) = opt_label {

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

@@ -5,7 +5,6 @@ use crate::pprust::state::{AnnNode, PrintState, State, INDENT_UNIT};
 use ast::StaticItem;
 use itertools::{Itertools, Position};
 use rustc_ast as ast;
-use rustc_ast::GenericBound;
 use rustc_ast::ModKind;
 use rustc_span::symbol::Ident;
 
@@ -338,19 +337,9 @@ impl<'a> State<'a> {
                 self.word_nbsp("trait");
                 self.print_ident(item.ident);
                 self.print_generic_params(&generics.params);
-                let mut real_bounds = Vec::with_capacity(bounds.len());
-                for b in bounds.iter() {
-                    if let GenericBound::Trait(ptr, ast::TraitBoundModifier::Maybe) = b {
-                        self.space();
-                        self.word_space("for ?");
-                        self.print_trait_ref(&ptr.trait_ref);
-                    } else {
-                        real_bounds.push(b.clone());
-                    }
-                }
-                if !real_bounds.is_empty() {
+                if !bounds.is_empty() {
                     self.word_nbsp(":");
-                    self.print_type_bounds(&real_bounds);
+                    self.print_type_bounds(bounds);
                 }
                 self.print_where_clause(&generics.where_clause);
                 self.word(" ");

compiler/rustc_attr/src/session_diagnostics.rs

@@ -2,7 +2,8 @@ use std::num::IntErrorKind;
 
 use rustc_ast as ast;
 use rustc_errors::{
-    error_code, Applicability, DiagCtxt, DiagnosticBuilder, ErrorGuaranteed, IntoDiagnostic,
+    error_code, Applicability, DiagCtxt, DiagnosticBuilder, EmissionGuarantee, IntoDiagnostic,
+    Level,
 };
 use rustc_macros::Diagnostic;
 use rustc_span::{Span, Symbol};
@@ -50,14 +51,12 @@ pub(crate) struct UnknownMetaItem<'a> {
 }
 
 // Manual implementation to be able to format `expected` items correctly.
-impl<'a> IntoDiagnostic<'a> for UnknownMetaItem<'_> {
-    fn into_diagnostic(self, dcx: &'a DiagCtxt) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
+impl<'a, G: EmissionGuarantee> IntoDiagnostic<'a, G> for UnknownMetaItem<'_> {
+    fn into_diagnostic(self, dcx: &'a DiagCtxt, level: Level) -> DiagnosticBuilder<'a, G> {
         let expected = self.expected.iter().map(|name| format!("`{name}`")).collect::<Vec<_>>();
-        let mut diag = dcx.struct_span_err_with_code(
-            self.span,
-            fluent::attr_unknown_meta_item,
-            error_code!(E0541),
-        );
+        let mut diag = DiagnosticBuilder::new(dcx, level, fluent::attr_unknown_meta_item);
+        diag.set_span(self.span);
+        diag.code(error_code!(E0541));
         diag.set_arg("item", self.item);
         diag.set_arg("expected", expected.join(", "));
         diag.span_label(self.span, fluent::attr_label);
@@ -200,10 +199,11 @@ pub(crate) struct UnsupportedLiteral {
     pub start_point_span: Span,
 }
 
-impl<'a> IntoDiagnostic<'a> for UnsupportedLiteral {
-    fn into_diagnostic(self, dcx: &'a DiagCtxt) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
-        let mut diag = dcx.struct_span_err_with_code(
-            self.span,
+impl<'a, G: EmissionGuarantee> IntoDiagnostic<'a, G> for UnsupportedLiteral {
+    fn into_diagnostic(self, dcx: &'a DiagCtxt, level: Level) -> DiagnosticBuilder<'a, G> {
+        let mut diag = DiagnosticBuilder::new(
+            dcx,
+            level,
             match self.reason {
                 UnsupportedLiteralReason::Generic => fluent::attr_unsupported_literal_generic,
                 UnsupportedLiteralReason::CfgString => fluent::attr_unsupported_literal_cfg_string,
@@ -214,8 +214,9 @@ impl<'a> IntoDiagnostic<'a> for UnsupportedLiteral {
                     fluent::attr_unsupported_literal_deprecated_kv_pair
                 }
             },
-            error_code!(E0565),
         );
+        diag.set_span(self.span);
+        diag.code(error_code!(E0565));
         if self.is_bytestr {
             diag.span_suggestion(
                 self.start_point_span,

compiler/rustc_borrowck/src/borrowck_errors.rs

@@ -1,5 +1,5 @@
 use rustc_errors::{
-    struct_span_err, DiagnosticBuilder, DiagnosticId, DiagnosticMessage, ErrorGuaranteed, MultiSpan,
+    struct_span_err, DiagnosticBuilder, DiagnosticId, DiagnosticMessage, MultiSpan,
 };
 use rustc_middle::ty::{self, Ty, TyCtxt};
 use rustc_span::Span;
@@ -12,7 +12,7 @@ impl<'cx, 'tcx> crate::MirBorrowckCtxt<'cx, 'tcx> {
         place: &str,
         borrow_place: &str,
         value_place: &str,
-    ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+    ) -> DiagnosticBuilder<'tcx> {
         self.infcx.tcx.sess.create_err(crate::session_diagnostics::MoveBorrow {
             place,
             span,
@@ -28,7 +28,7 @@ impl<'cx, 'tcx> crate::MirBorrowckCtxt<'cx, 'tcx> {
         desc: &str,
         borrow_span: Span,
         borrow_desc: &str,
-    ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+    ) -> DiagnosticBuilder<'tcx> {
         let mut err = struct_span_err!(
             self,
             span,
@@ -50,7 +50,7 @@ impl<'cx, 'tcx> crate::MirBorrowckCtxt<'cx, 'tcx> {
         old_loan_span: Span,
         old_opt_via: &str,
         old_load_end_span: Option<Span>,
-    ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+    ) -> DiagnosticBuilder<'tcx> {
         let via = |msg: &str| if msg.is_empty() { "".to_string() } else { format!(" (via {msg})") };
         let mut err = struct_span_err!(
             self,
@@ -97,7 +97,7 @@ impl<'cx, 'tcx> crate::MirBorrowckCtxt<'cx, 'tcx> {
         desc: &str,
         old_loan_span: Span,
         old_load_end_span: Option<Span>,
-    ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+    ) -> DiagnosticBuilder<'tcx> {
         let mut err = struct_span_err!(
             self,
             new_loan_span,
@@ -130,7 +130,7 @@ impl<'cx, 'tcx> crate::MirBorrowckCtxt<'cx, 'tcx> {
         noun_old: &str,
         old_opt_via: &str,
         previous_end_span: Option<Span>,
-    ) -> DiagnosticBuilder<'cx, ErrorGuaranteed> {
+    ) -> DiagnosticBuilder<'cx> {
         let mut err = struct_span_err!(
             self,
             new_loan_span,
@@ -162,7 +162,7 @@ impl<'cx, 'tcx> crate::MirBorrowckCtxt<'cx, 'tcx> {
         old_opt_via: &str,
         previous_end_span: Option<Span>,
         second_borrow_desc: &str,
-    ) -> DiagnosticBuilder<'cx, ErrorGuaranteed> {
+    ) -> DiagnosticBuilder<'cx> {
         let mut err = struct_span_err!(
             self,
             new_loan_span,
@@ -194,7 +194,7 @@ impl<'cx, 'tcx> crate::MirBorrowckCtxt<'cx, 'tcx> {
         kind_old: &str,
         msg_old: &str,
         old_load_end_span: Option<Span>,
-    ) -> DiagnosticBuilder<'cx, ErrorGuaranteed> {
+    ) -> DiagnosticBuilder<'cx> {
         let via = |msg: &str| if msg.is_empty() { "".to_string() } else { format!(" (via {msg})") };
         let mut err = struct_span_err!(
             self,
@@ -235,7 +235,7 @@ impl<'cx, 'tcx> crate::MirBorrowckCtxt<'cx, 'tcx> {
         span: Span,
         borrow_span: Span,
         desc: &str,
-    ) -> DiagnosticBuilder<'cx, ErrorGuaranteed> {
+    ) -> DiagnosticBuilder<'cx> {
         let mut err = struct_span_err!(
             self,
             span,
@@ -254,16 +254,12 @@ impl<'cx, 'tcx> crate::MirBorrowckCtxt<'cx, 'tcx> {
         span: Span,
         desc: &str,
         is_arg: bool,
-    ) -> DiagnosticBuilder<'cx, ErrorGuaranteed> {
+    ) -> DiagnosticBuilder<'cx> {
         let msg = if is_arg { "to immutable argument" } else { "twice to immutable variable" };
         struct_span_err!(self, span, E0384, "cannot assign {} {}", msg, desc)
     }
 
-    pub(crate) fn cannot_assign(
-        &self,
-        span: Span,
-        desc: &str,
-    ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+    pub(crate) fn cannot_assign(&self, span: Span, desc: &str) -> DiagnosticBuilder<'tcx> {
         struct_span_err!(self, span, E0594, "cannot assign to {}", desc)
     }
 
@@ -271,7 +267,7 @@ impl<'cx, 'tcx> crate::MirBorrowckCtxt<'cx, 'tcx> {
         &self,
         move_from_span: Span,
         move_from_desc: &str,
-    ) -> DiagnosticBuilder<'cx, ErrorGuaranteed> {
+    ) -> DiagnosticBuilder<'cx> {
         struct_span_err!(self, move_from_span, E0507, "cannot move out of {}", move_from_desc)
     }
 
@@ -283,7 +279,7 @@ impl<'cx, 'tcx> crate::MirBorrowckCtxt<'cx, 'tcx> {
         move_from_span: Span,
         ty: Ty<'_>,
         is_index: Option<bool>,
-    ) -> DiagnosticBuilder<'cx, ErrorGuaranteed> {
+    ) -> DiagnosticBuilder<'cx> {
         let type_name = match (&ty.kind(), is_index) {
             (&ty::Array(_, _), Some(true)) | (&ty::Array(_, _), None) => "array",
             (&ty::Slice(_), _) => "slice",
@@ -305,7 +301,7 @@ impl<'cx, 'tcx> crate::MirBorrowckCtxt<'cx, 'tcx> {
         &self,
         move_from_span: Span,
         container_ty: Ty<'_>,
-    ) -> DiagnosticBuilder<'cx, ErrorGuaranteed> {
+    ) -> DiagnosticBuilder<'cx> {
         let mut err = struct_span_err!(
             self,
             move_from_span,
@@ -323,7 +319,7 @@ impl<'cx, 'tcx> crate::MirBorrowckCtxt<'cx, 'tcx> {
         verb: &str,
         optional_adverb_for_moved: &str,
         moved_path: Option<String>,
-    ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+    ) -> DiagnosticBuilder<'tcx> {
         let moved_path = moved_path.map(|mp| format!(": `{mp}`")).unwrap_or_default();
 
         struct_span_err!(
@@ -342,7 +338,7 @@ impl<'cx, 'tcx> crate::MirBorrowckCtxt<'cx, 'tcx> {
         span: Span,
         path: &str,
         reason: &str,
-    ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+    ) -> DiagnosticBuilder<'tcx> {
         struct_span_err!(self, span, E0596, "cannot borrow {} as mutable{}", path, reason,)
     }
 
@@ -353,7 +349,7 @@ impl<'cx, 'tcx> crate::MirBorrowckCtxt<'cx, 'tcx> {
         immutable_place: &str,
         immutable_section: &str,
         action: &str,
-    ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+    ) -> DiagnosticBuilder<'tcx> {
         let mut err = struct_span_err!(
             self,
             mutate_span,
@@ -372,7 +368,7 @@ impl<'cx, 'tcx> crate::MirBorrowckCtxt<'cx, 'tcx> {
         &self,
         span: Span,
         yield_span: Span,
-    ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+    ) -> DiagnosticBuilder<'tcx> {
         let coroutine_kind = self.body.coroutine.as_ref().unwrap().coroutine_kind;
         let mut err = struct_span_err!(
             self,
@@ -387,7 +383,7 @@ impl<'cx, 'tcx> crate::MirBorrowckCtxt<'cx, 'tcx> {
     pub(crate) fn cannot_borrow_across_destructor(
         &self,
         borrow_span: Span,
-    ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+    ) -> DiagnosticBuilder<'tcx> {
         struct_span_err!(
             self,
             borrow_span,
@@ -400,7 +396,7 @@ impl<'cx, 'tcx> crate::MirBorrowckCtxt<'cx, 'tcx> {
         &self,
         span: Span,
         path: &str,
-    ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+    ) -> DiagnosticBuilder<'tcx> {
         struct_span_err!(self, span, E0597, "{} does not live long enough", path,)
     }
 
@@ -410,7 +406,7 @@ impl<'cx, 'tcx> crate::MirBorrowckCtxt<'cx, 'tcx> {
         return_kind: &str,
         reference_desc: &str,
         path_desc: &str,
-    ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+    ) -> DiagnosticBuilder<'tcx> {
         let mut err = struct_span_err!(
             self,
             span,
@@ -436,7 +432,7 @@ impl<'cx, 'tcx> crate::MirBorrowckCtxt<'cx, 'tcx> {
         borrowed_path: &str,
         capture_span: Span,
         scope: &str,
-    ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+    ) -> DiagnosticBuilder<'tcx> {
         let mut err = struct_span_err!(
             self,
             closure_span,
@@ -452,14 +448,14 @@ impl<'cx, 'tcx> crate::MirBorrowckCtxt<'cx, 'tcx> {
     pub(crate) fn thread_local_value_does_not_live_long_enough(
         &self,
         span: Span,
-    ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+    ) -> DiagnosticBuilder<'tcx> {
         struct_span_err!(self, span, E0712, "thread-local variable borrowed past end of function",)
     }
 
     pub(crate) fn temporary_value_borrowed_for_too_long(
         &self,
         span: Span,
-    ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+    ) -> DiagnosticBuilder<'tcx> {
         struct_span_err!(self, span, E0716, "temporary value dropped while borrowed",)
     }
 
@@ -470,7 +466,7 @@ impl<'cx, 'tcx> crate::MirBorrowckCtxt<'cx, 'tcx> {
         sp: S,
         msg: impl Into<DiagnosticMessage>,
         code: DiagnosticId,
-    ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+    ) -> DiagnosticBuilder<'tcx> {
         self.infcx.tcx.sess.struct_span_err_with_code(sp, msg, code)
     }
 }
@@ -479,7 +475,7 @@ pub(crate) fn borrowed_data_escapes_closure<'tcx>(
     tcx: TyCtxt<'tcx>,
     escape_span: Span,
     escapes_from: &str,
-) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+) -> DiagnosticBuilder<'tcx> {
     struct_span_err!(
         tcx.sess,
         escape_span,

compiler/rustc_borrowck/src/diagnostics/bound_region_errors.rs

@@ -1,7 +1,7 @@
 #![deny(rustc::untranslatable_diagnostic)]
 #![deny(rustc::diagnostic_outside_of_impl)]
 
-use rustc_errors::{DiagnosticBuilder, ErrorGuaranteed};
+use rustc_errors::DiagnosticBuilder;
 use rustc_infer::infer::canonical::Canonical;
 use rustc_infer::infer::error_reporting::nice_region_error::NiceRegionError;
 use rustc_infer::infer::region_constraints::Constraint;
@@ -147,11 +147,7 @@ impl<'tcx> ToUniverseInfo<'tcx> for ! {
 trait TypeOpInfo<'tcx> {
     /// Returns an error to be reported if rerunning the type op fails to
     /// recover the error's cause.
-    fn fallback_error(
-        &self,
-        tcx: TyCtxt<'tcx>,
-        span: Span,
-    ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed>;
+    fn fallback_error(&self, tcx: TyCtxt<'tcx>, span: Span) -> DiagnosticBuilder<'tcx>;
 
     fn base_universe(&self) -> ty::UniverseIndex;
 
@@ -161,7 +157,7 @@ trait TypeOpInfo<'tcx> {
         cause: ObligationCause<'tcx>,
         placeholder_region: ty::Region<'tcx>,
         error_region: Option<ty::Region<'tcx>>,
-    ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>>;
+    ) -> Option<DiagnosticBuilder<'tcx>>;
 
     #[instrument(level = "debug", skip(self, mbcx))]
     fn report_error(
@@ -224,11 +220,7 @@ struct PredicateQuery<'tcx> {
 }
 
 impl<'tcx> TypeOpInfo<'tcx> for PredicateQuery<'tcx> {
-    fn fallback_error(
-        &self,
-        tcx: TyCtxt<'tcx>,
-        span: Span,
-    ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+    fn fallback_error(&self, tcx: TyCtxt<'tcx>, span: Span) -> DiagnosticBuilder<'tcx> {
         tcx.sess.create_err(HigherRankedLifetimeError {
             cause: Some(HigherRankedErrorCause::CouldNotProve {
                 predicate: self.canonical_query.value.value.predicate.to_string(),
@@ -247,7 +239,7 @@ impl<'tcx> TypeOpInfo<'tcx> for PredicateQuery<'tcx> {
         cause: ObligationCause<'tcx>,
         placeholder_region: ty::Region<'tcx>,
         error_region: Option<ty::Region<'tcx>>,
-    ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
+    ) -> Option<DiagnosticBuilder<'tcx>> {
         let (infcx, key, _) =
             mbcx.infcx.tcx.infer_ctxt().build_with_canonical(cause.span, &self.canonical_query);
         let ocx = ObligationCtxt::new(&infcx);
@@ -265,11 +257,7 @@ impl<'tcx, T> TypeOpInfo<'tcx> for NormalizeQuery<'tcx, T>
 where
     T: Copy + fmt::Display + TypeFoldable<TyCtxt<'tcx>> + 'tcx,
 {
-    fn fallback_error(
-        &self,
-        tcx: TyCtxt<'tcx>,
-        span: Span,
-    ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+    fn fallback_error(&self, tcx: TyCtxt<'tcx>, span: Span) -> DiagnosticBuilder<'tcx> {
         tcx.sess.create_err(HigherRankedLifetimeError {
             cause: Some(HigherRankedErrorCause::CouldNotNormalize {
                 value: self.canonical_query.value.value.value.to_string(),
@@ -288,7 +276,7 @@ where
         cause: ObligationCause<'tcx>,
         placeholder_region: ty::Region<'tcx>,
         error_region: Option<ty::Region<'tcx>>,
-    ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
+    ) -> Option<DiagnosticBuilder<'tcx>> {
         let (infcx, key, _) =
             mbcx.infcx.tcx.infer_ctxt().build_with_canonical(cause.span, &self.canonical_query);
         let ocx = ObligationCtxt::new(&infcx);
@@ -312,11 +300,7 @@ struct AscribeUserTypeQuery<'tcx> {
 }
 
 impl<'tcx> TypeOpInfo<'tcx> for AscribeUserTypeQuery<'tcx> {
-    fn fallback_error(
-        &self,
-        tcx: TyCtxt<'tcx>,
-        span: Span,
-    ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+    fn fallback_error(&self, tcx: TyCtxt<'tcx>, span: Span) -> DiagnosticBuilder<'tcx> {
         // FIXME: This error message isn't great, but it doesn't show up in the existing UI tests,
         // and is only the fallback when the nice error fails. Consider improving this some more.
         tcx.sess.create_err(HigherRankedLifetimeError { cause: None, span })
@@ -332,7 +316,7 @@ impl<'tcx> TypeOpInfo<'tcx> for AscribeUserTypeQuery<'tcx> {
         cause: ObligationCause<'tcx>,
         placeholder_region: ty::Region<'tcx>,
         error_region: Option<ty::Region<'tcx>>,
-    ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
+    ) -> Option<DiagnosticBuilder<'tcx>> {
         let (infcx, key, _) =
             mbcx.infcx.tcx.infer_ctxt().build_with_canonical(cause.span, &self.canonical_query);
         let ocx = ObligationCtxt::new(&infcx);
@@ -342,11 +326,7 @@ impl<'tcx> TypeOpInfo<'tcx> for AscribeUserTypeQuery<'tcx> {
 }
 
 impl<'tcx> TypeOpInfo<'tcx> for crate::type_check::InstantiateOpaqueType<'tcx> {
-    fn fallback_error(
-        &self,
-        tcx: TyCtxt<'tcx>,
-        span: Span,
-    ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+    fn fallback_error(&self, tcx: TyCtxt<'tcx>, span: Span) -> DiagnosticBuilder<'tcx> {
         // FIXME: This error message isn't great, but it doesn't show up in the existing UI tests,
         // and is only the fallback when the nice error fails. Consider improving this some more.
         tcx.sess.create_err(HigherRankedLifetimeError { cause: None, span })
@@ -362,7 +342,7 @@ impl<'tcx> TypeOpInfo<'tcx> for crate::type_check::InstantiateOpaqueType<'tcx> {
         _cause: ObligationCause<'tcx>,
         placeholder_region: ty::Region<'tcx>,
         error_region: Option<ty::Region<'tcx>>,
-    ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
+    ) -> Option<DiagnosticBuilder<'tcx>> {
         try_extract_error_from_region_constraints(
             mbcx.infcx,
             placeholder_region,
@@ -383,7 +363,7 @@ fn try_extract_error_from_fulfill_cx<'tcx>(
     ocx: &ObligationCtxt<'_, 'tcx>,
     placeholder_region: ty::Region<'tcx>,
     error_region: Option<ty::Region<'tcx>>,
-) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
+) -> Option<DiagnosticBuilder<'tcx>> {
     // We generally shouldn't have errors here because the query was
     // already run, but there's no point using `span_delayed_bug`
     // when we're going to emit an error here anyway.
@@ -407,14 +387,19 @@ fn try_extract_error_from_region_constraints<'tcx>(
     region_constraints: &RegionConstraintData<'tcx>,
     mut region_var_origin: impl FnMut(RegionVid) -> RegionVariableOrigin,
     mut universe_of_region: impl FnMut(RegionVid) -> UniverseIndex,
-) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
+) -> Option<DiagnosticBuilder<'tcx>> {
+    let placeholder_universe = match placeholder_region.kind() {
+        ty::RePlaceholder(p) => p.universe,
+        ty::ReVar(vid) => universe_of_region(vid),
+        _ => ty::UniverseIndex::ROOT,
+    };
     let matches =
         |a_region: Region<'tcx>, b_region: Region<'tcx>| match (a_region.kind(), b_region.kind()) {
             (RePlaceholder(a_p), RePlaceholder(b_p)) => a_p.bound == b_p.bound,
             _ => a_region == b_region,
         };
-    let check = |constraint: &Constraint<'tcx>, cause: &SubregionOrigin<'tcx>, exact| {
-        match *constraint {
+    let mut check =
+        |constraint: &Constraint<'tcx>, cause: &SubregionOrigin<'tcx>, exact| match *constraint {
             Constraint::RegSubReg(sub, sup)
                 if ((exact && sup == placeholder_region)
                     || (!exact && matches(sup, placeholder_region)))
@@ -422,16 +407,16 @@ fn try_extract_error_from_region_constraints<'tcx>(
             {
                 Some((sub, cause.clone()))
             }
-            // FIXME: Should this check the universe of the var?
             Constraint::VarSubReg(vid, sup)
-                if ((exact && sup == placeholder_region)
-                    || (!exact && matches(sup, placeholder_region))) =>
+                if (exact
+                    && sup == placeholder_region
+                    && !universe_of_region(vid).can_name(placeholder_universe))
+                    || (!exact && matches(sup, placeholder_region)) =>
             {
                 Some((ty::Region::new_var(infcx.tcx, vid), cause.clone()))
             }
             _ => None,
-        }
-    };
+        };
     let mut info = region_constraints
         .constraints
         .iter()

compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs

@@ -1,13 +1,11 @@
 use either::Either;
-use hir::PatField;
 use rustc_data_structures::captures::Captures;
 use rustc_data_structures::fx::FxIndexSet;
-use rustc_errors::{
-    struct_span_err, Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed, MultiSpan,
-};
+use rustc_errors::{struct_span_err, Applicability, Diagnostic, DiagnosticBuilder, MultiSpan};
 use rustc_hir as hir;
 use rustc_hir::def::{DefKind, Res};
 use rustc_hir::intravisit::{walk_block, walk_expr, Visitor};
+use rustc_hir::{CoroutineDesugaring, PatField};
 use rustc_hir::{CoroutineKind, CoroutineSource, LangItem};
 use rustc_infer::traits::ObligationCause;
 use rustc_middle::hir::nested_filter::OnlyBodies;
@@ -324,7 +322,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         &mut self,
         mpi: MovePathIndex,
         move_span: Span,
-        err: &mut DiagnosticBuilder<'_, ErrorGuaranteed>,
+        err: &mut DiagnosticBuilder<'_>,
         in_pattern: &mut bool,
         move_spans: UseSpans<'_>,
     ) {
@@ -483,7 +481,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         desired_action: InitializationRequiringAction,
         span: Span,
         use_spans: UseSpans<'tcx>,
-    ) -> DiagnosticBuilder<'cx, ErrorGuaranteed> {
+    ) -> DiagnosticBuilder<'cx> {
         // We need all statements in the body where the binding was assigned to to later find all
         // the branching code paths where the binding *wasn't* assigned to.
         let inits = &self.move_data.init_path_map[mpi];
@@ -873,7 +871,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         location: Location,
         (place, _span): (Place<'tcx>, Span),
         borrow: &BorrowData<'tcx>,
-    ) -> DiagnosticBuilder<'cx, ErrorGuaranteed> {
+    ) -> DiagnosticBuilder<'cx> {
         let borrow_spans = self.retrieve_borrow_spans(borrow);
         let borrow_span = borrow_spans.args_or_use();
 
@@ -921,7 +919,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         (place, span): (Place<'tcx>, Span),
         gen_borrow_kind: BorrowKind,
         issued_borrow: &BorrowData<'tcx>,
-    ) -> DiagnosticBuilder<'cx, ErrorGuaranteed> {
+    ) -> DiagnosticBuilder<'cx> {
         let issued_spans = self.retrieve_borrow_spans(issued_borrow);
         let issued_span = issued_spans.args_or_use();
 
@@ -2025,7 +2023,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         drop_span: Span,
         borrow_spans: UseSpans<'tcx>,
         explanation: BorrowExplanation<'tcx>,
-    ) -> DiagnosticBuilder<'cx, ErrorGuaranteed> {
+    ) -> DiagnosticBuilder<'cx> {
         debug!(
             "report_local_value_does_not_live_long_enough(\
              {:?}, {:?}, {:?}, {:?}, {:?}\
@@ -2200,7 +2198,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         &mut self,
         drop_span: Span,
         borrow_span: Span,
-    ) -> DiagnosticBuilder<'cx, ErrorGuaranteed> {
+    ) -> DiagnosticBuilder<'cx> {
         debug!(
             "report_thread_local_value_does_not_live_long_enough(\
              {:?}, {:?}\
@@ -2228,7 +2226,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         borrow_spans: UseSpans<'tcx>,
         proper_span: Span,
         explanation: BorrowExplanation<'tcx>,
-    ) -> DiagnosticBuilder<'cx, ErrorGuaranteed> {
+    ) -> DiagnosticBuilder<'cx> {
         if let BorrowExplanation::MustBeValidFor { category, span, from_closure: false, .. } =
             explanation
         {
@@ -2395,7 +2393,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         return_span: Span,
         category: ConstraintCategory<'tcx>,
         opt_place_desc: Option<&String>,
-    ) -> Option<DiagnosticBuilder<'cx, ErrorGuaranteed>> {
+    ) -> Option<DiagnosticBuilder<'cx>> {
         let return_kind = match category {
             ConstraintCategory::Return(_) => "return",
             ConstraintCategory::Yield => "yield",
@@ -2490,7 +2488,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         constraint_span: Span,
         captured_var: &str,
         scope: &str,
-    ) -> DiagnosticBuilder<'cx, ErrorGuaranteed> {
+    ) -> DiagnosticBuilder<'cx> {
         let tcx = self.infcx.tcx;
         let args_span = use_span.args_or_use();
 
@@ -2516,27 +2514,29 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         };
         let kind = match use_span.coroutine_kind() {
             Some(coroutine_kind) => match coroutine_kind {
-                CoroutineKind::Gen(kind) => match kind {
+                CoroutineKind::Desugared(CoroutineDesugaring::Gen, kind) => match kind {
                     CoroutineSource::Block => "gen block",
                     CoroutineSource::Closure => "gen closure",
                     CoroutineSource::Fn => {
                         bug!("gen block/closure expected, but gen function found.")
                     }
                 },
-                CoroutineKind::AsyncGen(kind) => match kind {
+                CoroutineKind::Desugared(CoroutineDesugaring::AsyncGen, kind) => match kind {
                     CoroutineSource::Block => "async gen block",
                     CoroutineSource::Closure => "async gen closure",
                     CoroutineSource::Fn => {
                         bug!("gen block/closure expected, but gen function found.")
                     }
                 },
-                CoroutineKind::Async(async_kind) => match async_kind {
-                    CoroutineSource::Block => "async block",
-                    CoroutineSource::Closure => "async closure",
-                    CoroutineSource::Fn => {
-                        bug!("async block/closure expected, but async function found.")
+                CoroutineKind::Desugared(CoroutineDesugaring::Async, async_kind) => {
+                    match async_kind {
+                        CoroutineSource::Block => "async block",
+                        CoroutineSource::Closure => "async closure",
+                        CoroutineSource::Fn => {
+                            bug!("async block/closure expected, but async function found.")
+                        }
                     }
-                },
+                }
                 CoroutineKind::Coroutine => "coroutine",
             },
             None => "closure",
@@ -2566,7 +2566,10 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
             }
             ConstraintCategory::CallArgument(_) => {
                 fr_name.highlight_region_name(&mut err);
-                if matches!(use_span.coroutine_kind(), Some(CoroutineKind::Async(_))) {
+                if matches!(
+                    use_span.coroutine_kind(),
+                    Some(CoroutineKind::Desugared(CoroutineDesugaring::Async, _))
+                ) {
                     err.note(
                         "async blocks are not executed immediately and must either take a \
                          reference or ownership of outside variables they use",
@@ -2593,7 +2596,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         upvar_span: Span,
         upvar_name: Symbol,
         escape_span: Span,
-    ) -> DiagnosticBuilder<'cx, ErrorGuaranteed> {
+    ) -> DiagnosticBuilder<'cx> {
         let tcx = self.infcx.tcx;
 
         let escapes_from = tcx.def_descr(self.mir_def_id().to_def_id());

compiler/rustc_borrowck/src/diagnostics/move_errors.rs

@@ -1,4 +1,4 @@
-use rustc_errors::{Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed};
+use rustc_errors::{Applicability, Diagnostic, DiagnosticBuilder};
 use rustc_middle::mir::*;
 use rustc_middle::ty::{self, Ty};
 use rustc_mir_dataflow::move_paths::{LookupResult, MovePathIndex};
@@ -288,7 +288,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
         &mut self,
         place: Place<'tcx>,
         span: Span,
-    ) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
+    ) -> DiagnosticBuilder<'a> {
         let description = if place.projection.len() == 1 {
             format!("static item {}", self.describe_any_place(place.as_ref()))
         } else {
@@ -310,7 +310,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
         deref_target_place: Place<'tcx>,
         span: Span,
         use_spans: Option<UseSpans<'tcx>>,
-    ) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
+    ) -> DiagnosticBuilder<'a> {
         // Inspect the type of the content behind the
         // borrow to provide feedback about why this
         // was a move rather than a copy.

compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs

@@ -1,5 +1,5 @@
 use hir::ExprKind;
-use rustc_errors::{Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed};
+use rustc_errors::{Applicability, Diagnostic, DiagnosticBuilder};
 use rustc_hir as hir;
 use rustc_hir::intravisit::Visitor;
 use rustc_hir::Node;
@@ -711,7 +711,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
 
     fn construct_mut_suggestion_for_local_binding_patterns(
         &self,
-        err: &mut DiagnosticBuilder<'_, ErrorGuaranteed>,
+        err: &mut DiagnosticBuilder<'_>,
         local: Local,
     ) {
         let local_decl = &self.body.local_decls[local];
@@ -1025,7 +1025,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
         }
     }
 
-    fn suggest_using_iter_mut(&self, err: &mut DiagnosticBuilder<'_, ErrorGuaranteed>) {
+    fn suggest_using_iter_mut(&self, err: &mut DiagnosticBuilder<'_>) {
         let source = self.body.source;
         let hir = self.infcx.tcx.hir();
         if let InstanceDef::Item(def_id) = source.instance
@@ -1067,12 +1067,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
         }
     }
 
-    fn suggest_make_local_mut(
-        &self,
-        err: &mut DiagnosticBuilder<'_, ErrorGuaranteed>,
-        local: Local,
-        name: Symbol,
-    ) {
+    fn suggest_make_local_mut(&self, err: &mut DiagnosticBuilder<'_>, local: Local, name: Symbol) {
         let local_decl = &self.body.local_decls[local];
 
         let (pointer_sigil, pointer_desc) =

compiler/rustc_borrowck/src/diagnostics/region_errors.rs

@@ -3,7 +3,7 @@
 //! Error reporting machinery for lifetime errors.
 
 use rustc_data_structures::fx::FxIndexSet;
-use rustc_errors::{Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed, MultiSpan};
+use rustc_errors::{Applicability, Diagnostic, DiagnosticBuilder, MultiSpan};
 use rustc_hir as hir;
 use rustc_hir::def::Res::Def;
 use rustc_hir::def_id::DefId;
@@ -202,7 +202,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
     // and the span which bounded to the trait for adding 'static lifetime suggestion
     fn suggest_static_lifetime_for_gat_from_hrtb(
         &self,
-        diag: &mut DiagnosticBuilder<'_, ErrorGuaranteed>,
+        diag: &mut DiagnosticBuilder<'_>,
         lower_bound: RegionVid,
     ) {
         let mut suggestions = vec![];
@@ -573,7 +573,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
         &self,
         errci: &ErrorConstraintInfo<'tcx>,
         kind: ReturnConstraint,
-    ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+    ) -> DiagnosticBuilder<'tcx> {
         let ErrorConstraintInfo { outlived_fr, span, .. } = errci;
 
         let mut output_ty = self.regioncx.universal_regions().unnormalized_output_ty;
@@ -645,7 +645,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
     fn report_escaping_data_error(
         &self,
         errci: &ErrorConstraintInfo<'tcx>,
-    ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+    ) -> DiagnosticBuilder<'tcx> {
         let ErrorConstraintInfo { span, category, .. } = errci;
 
         let fr_name_and_span = self.regioncx.get_var_name_and_span_for_region(
@@ -744,10 +744,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
     ///    |     ^^^^^^^^^^^^^^ function was supposed to return data with lifetime `'a` but it
     ///    |                    is returning data with lifetime `'b`
     /// ```
-    fn report_general_error(
-        &self,
-        errci: &ErrorConstraintInfo<'tcx>,
-    ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+    fn report_general_error(&self, errci: &ErrorConstraintInfo<'tcx>) -> DiagnosticBuilder<'tcx> {
         let ErrorConstraintInfo {
             fr,
             fr_is_local,
@@ -1049,7 +1046,10 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                 ..
             }) => {
                 let body = map.body(*body);
-                if !matches!(body.coroutine_kind, Some(hir::CoroutineKind::Async(..))) {
+                if !matches!(
+                    body.coroutine_kind,
+                    Some(hir::CoroutineKind::Desugared(hir::CoroutineDesugaring::Async, _))
+                ) {
                     closure_span = Some(expr.span.shrink_to_lo());
                 }
             }

compiler/rustc_borrowck/src/diagnostics/region_name.rs

@@ -684,39 +684,46 @@ impl<'tcx> MirBorrowckCtxt<'_, 'tcx> {
                     hir::FnRetTy::Return(hir_ty) => (fn_decl.output.span(), Some(hir_ty)),
                 };
                 let mir_description = match hir.body(body).coroutine_kind {
-                    Some(hir::CoroutineKind::Async(src)) => match src {
-                        hir::CoroutineSource::Block => " of async block",
-                        hir::CoroutineSource::Closure => " of async closure",
-                        hir::CoroutineSource::Fn => {
-                            let parent_item =
-                                tcx.hir_node_by_def_id(hir.get_parent_item(mir_hir_id).def_id);
-                            let output = &parent_item
-                                .fn_decl()
-                                .expect("coroutine lowered from async fn should be in fn")
-                                .output;
-                            span = output.span();
-                            if let hir::FnRetTy::Return(ret) = output {
-                                hir_ty = Some(self.get_future_inner_return_ty(*ret));
+                    Some(hir::CoroutineKind::Desugared(hir::CoroutineDesugaring::Async, src)) => {
+                        match src {
+                            hir::CoroutineSource::Block => " of async block",
+                            hir::CoroutineSource::Closure => " of async closure",
+                            hir::CoroutineSource::Fn => {
+                                let parent_item =
+                                    tcx.hir_node_by_def_id(hir.get_parent_item(mir_hir_id).def_id);
+                                let output = &parent_item
+                                    .fn_decl()
+                                    .expect("coroutine lowered from async fn should be in fn")
+                                    .output;
+                                span = output.span();
+                                if let hir::FnRetTy::Return(ret) = output {
+                                    hir_ty = Some(self.get_future_inner_return_ty(*ret));
+                                }
+                                " of async function"
                             }
-                            " of async function"
                         }
-                    },
-                    Some(hir::CoroutineKind::Gen(src)) => match src {
-                        hir::CoroutineSource::Block => " of gen block",
-                        hir::CoroutineSource::Closure => " of gen closure",
-                        hir::CoroutineSource::Fn => {
-                            let parent_item =
-                                tcx.hir_node_by_def_id(hir.get_parent_item(mir_hir_id).def_id);
-                            let output = &parent_item
-                                .fn_decl()
-                                .expect("coroutine lowered from gen fn should be in fn")
-                                .output;
-                            span = output.span();
-                            " of gen function"
+                    }
+                    Some(hir::CoroutineKind::Desugared(hir::CoroutineDesugaring::Gen, src)) => {
+                        match src {
+                            hir::CoroutineSource::Block => " of gen block",
+                            hir::CoroutineSource::Closure => " of gen closure",
+                            hir::CoroutineSource::Fn => {
+                                let parent_item =
+                                    tcx.hir_node_by_def_id(hir.get_parent_item(mir_hir_id).def_id);
+                                let output = &parent_item
+                                    .fn_decl()
+                                    .expect("coroutine lowered from gen fn should be in fn")
+                                    .output;
+                                span = output.span();
+                                " of gen function"
+                            }
                         }
-                    },
+                    }
 
-                    Some(hir::CoroutineKind::AsyncGen(src)) => match src {
+                    Some(hir::CoroutineKind::Desugared(
+                        hir::CoroutineDesugaring::AsyncGen,
+                        src,
+                    )) => match src {
                         hir::CoroutineSource::Block => " of async gen block",
                         hir::CoroutineSource::Closure => " of async gen closure",
                         hir::CoroutineSource::Fn => {

compiler/rustc_borrowck/src/lib.rs

@@ -2407,8 +2407,8 @@ mod error {
         /// when errors in the map are being re-added to the error buffer so that errors with the
         /// same primary span come out in a consistent order.
         buffered_move_errors:
-            BTreeMap<Vec<MoveOutIndex>, (PlaceRef<'tcx>, DiagnosticBuilder<'tcx, ErrorGuaranteed>)>,
-        buffered_mut_errors: FxIndexMap<Span, (DiagnosticBuilder<'tcx, ErrorGuaranteed>, usize)>,
+            BTreeMap<Vec<MoveOutIndex>, (PlaceRef<'tcx>, DiagnosticBuilder<'tcx>)>,
+        buffered_mut_errors: FxIndexMap<Span, (DiagnosticBuilder<'tcx>, usize)>,
         /// Diagnostics to be reported buffer.
         buffered: Vec<Diagnostic>,
         /// Set to Some if we emit an error during borrowck
@@ -2426,7 +2426,7 @@ mod error {
             }
         }
 
-        pub fn buffer_error(&mut self, t: DiagnosticBuilder<'_, ErrorGuaranteed>) {
+        pub fn buffer_error(&mut self, t: DiagnosticBuilder<'_>) {
             if let None = self.tainted_by_errors {
                 self.tainted_by_errors = Some(self.tcx.sess.span_delayed_bug(
                     t.span.clone_ignoring_labels(),
@@ -2446,7 +2446,7 @@ mod error {
     }
 
     impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
-        pub fn buffer_error(&mut self, t: DiagnosticBuilder<'_, ErrorGuaranteed>) {
+        pub fn buffer_error(&mut self, t: DiagnosticBuilder<'_>) {
             self.errors.buffer_error(t);
         }
 
@@ -2457,7 +2457,7 @@ mod error {
         pub fn buffer_move_error(
             &mut self,
             move_out_indices: Vec<MoveOutIndex>,
-            place_and_err: (PlaceRef<'tcx>, DiagnosticBuilder<'tcx, ErrorGuaranteed>),
+            place_and_err: (PlaceRef<'tcx>, DiagnosticBuilder<'tcx>),
         ) -> bool {
             if let Some((_, diag)) =
                 self.errors.buffered_move_errors.insert(move_out_indices, place_and_err)
@@ -2473,16 +2473,11 @@ mod error {
         pub fn get_buffered_mut_error(
             &mut self,
             span: Span,
-        ) -> Option<(DiagnosticBuilder<'tcx, ErrorGuaranteed>, usize)> {
+        ) -> Option<(DiagnosticBuilder<'tcx>, usize)> {
             self.errors.buffered_mut_errors.remove(&span)
         }
 
-        pub fn buffer_mut_error(
-            &mut self,
-            span: Span,
-            t: DiagnosticBuilder<'tcx, ErrorGuaranteed>,
-            count: usize,
-        ) {
+        pub fn buffer_mut_error(&mut self, span: Span, t: DiagnosticBuilder<'tcx>, count: usize) {
             self.errors.buffered_mut_errors.insert(span, (t, count));
         }
 
@@ -2517,7 +2512,7 @@ mod error {
         pub fn has_move_error(
             &self,
             move_out_indices: &[MoveOutIndex],
-        ) -> Option<&(PlaceRef<'tcx>, DiagnosticBuilder<'cx, ErrorGuaranteed>)> {
+        ) -> Option<&(PlaceRef<'tcx>, DiagnosticBuilder<'cx>)> {
             self.errors.buffered_move_errors.get(move_out_indices)
         }
     }

compiler/rustc_builtin_macros/src/assert/context.rs

@@ -303,7 +303,7 @@ impl<'cx, 'a> Context<'cx, 'a> {
             | ExprKind::Continue(_)
             | ExprKind::Err
             | ExprKind::Field(_, _)
-            | ExprKind::ForLoop(_, _, _, _)
+            | ExprKind::ForLoop { .. }
             | ExprKind::FormatArgs(_)
             | ExprKind::IncludedBytes(..)
             | ExprKind::InlineAsm(_)

compiler/rustc_builtin_macros/src/errors.rs

@@ -1,6 +1,6 @@
 use rustc_errors::{
-    AddToDiagnostic, DiagCtxt, DiagnosticBuilder, ErrorGuaranteed, IntoDiagnostic, MultiSpan,
-    SingleLabelManySpans,
+    AddToDiagnostic, DiagCtxt, DiagnosticBuilder, EmissionGuarantee, IntoDiagnostic, Level,
+    MultiSpan, SingleLabelManySpans,
 };
 use rustc_macros::{Diagnostic, Subdiagnostic};
 use rustc_span::{symbol::Ident, Span, Symbol};
@@ -446,14 +446,14 @@ pub(crate) struct EnvNotDefinedWithUserMessage {
 }
 
 // Hand-written implementation to support custom user messages.
-impl<'a> IntoDiagnostic<'a> for EnvNotDefinedWithUserMessage {
+impl<'a, G: EmissionGuarantee> IntoDiagnostic<'a, G> for EnvNotDefinedWithUserMessage {
     #[track_caller]
-    fn into_diagnostic(self, dcx: &'a DiagCtxt) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
+    fn into_diagnostic(self, dcx: &'a DiagCtxt, level: Level) -> DiagnosticBuilder<'a, G> {
         #[expect(
             rustc::untranslatable_diagnostic,
             reason = "cannot translate user-provided messages"
         )]
-        let mut diag = dcx.struct_err(self.msg_from_user.to_string());
+        let mut diag = DiagnosticBuilder::new(dcx, level, self.msg_from_user.to_string());
         diag.set_span(self.span);
         diag
     }
@@ -801,9 +801,13 @@ pub(crate) struct AsmClobberNoReg {
     pub(crate) clobbers: Vec<Span>,
 }
 
-impl<'a> IntoDiagnostic<'a> for AsmClobberNoReg {
-    fn into_diagnostic(self, dcx: &'a DiagCtxt) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
-        let mut diag = dcx.struct_err(crate::fluent_generated::builtin_macros_asm_clobber_no_reg);
+impl<'a, G: EmissionGuarantee> IntoDiagnostic<'a, G> for AsmClobberNoReg {
+    fn into_diagnostic(self, dcx: &'a DiagCtxt, level: Level) -> DiagnosticBuilder<'a, G> {
+        let mut diag = DiagnosticBuilder::new(
+            dcx,
+            level,
+            crate::fluent_generated::builtin_macros_asm_clobber_no_reg,
+        );
         diag.set_span(self.spans.clone());
         // eager translation as `span_labels` takes `AsRef<str>`
         let lbl1 = dcx.eagerly_translate_to_string(

compiler/rustc_builtin_macros/src/format.rs

@@ -8,9 +8,7 @@ use rustc_ast::{
     FormatDebugHex, FormatOptions, FormatPlaceholder, FormatSign, FormatTrait,
 };
 use rustc_data_structures::fx::FxHashSet;
-use rustc_errors::{
-    Applicability, DiagnosticBuilder, ErrorGuaranteed, MultiSpan, PResult, SingleLabelManySpans,
-};
+use rustc_errors::{Applicability, DiagnosticBuilder, MultiSpan, PResult, SingleLabelManySpans};
 use rustc_expand::base::{self, *};
 use rustc_parse_format as parse;
 use rustc_span::symbol::{Ident, Symbol};
@@ -726,7 +724,7 @@ fn report_redundant_format_arguments<'a>(
     args: &FormatArguments,
     used: &[bool],
     placeholders: Vec<(Span, &str)>,
-) -> Option<DiagnosticBuilder<'a, ErrorGuaranteed>> {
+) -> Option<DiagnosticBuilder<'a>> {
     let mut fmt_arg_indices = vec![];
     let mut args_spans = vec![];
     let mut fmt_spans = vec![];
@@ -885,7 +883,6 @@ fn report_invalid_references(
             highlight: SingleLabelManySpans {
                 spans: args.explicit_args().iter().map(|arg| arg.expr.span).collect(),
                 label: "",
-                kind: rustc_errors::LabelKind::Label,
             },
         });
         // Point out `{:.*}` placeholders: those take an extra argument.

compiler/rustc_builtin_macros/src/test.rs

@@ -5,7 +5,7 @@ use crate::util::{check_builtin_macro_attribute, warn_on_duplicate_attribute};
 use rustc_ast::ptr::P;
 use rustc_ast::{self as ast, attr, GenericParamKind};
 use rustc_ast_pretty::pprust;
-use rustc_errors::Applicability;
+use rustc_errors::{Applicability, DiagnosticBuilder, Level};
 use rustc_expand::base::*;
 use rustc_span::symbol::{sym, Ident, Symbol};
 use rustc_span::{ErrorGuaranteed, FileNameDisplayPreference, Span};
@@ -391,15 +391,14 @@ pub fn expand_test_or_bench(
 fn not_testable_error(cx: &ExtCtxt<'_>, attr_sp: Span, item: Option<&ast::Item>) {
     let dcx = cx.sess.dcx();
     let msg = "the `#[test]` attribute may only be used on a non-associated function";
-    let mut err = match item.map(|i| &i.kind) {
+    let level = match item.map(|i| &i.kind) {
         // These were a warning before #92959 and need to continue being that to avoid breaking
         // stable user code (#94508).
-        Some(ast::ItemKind::MacCall(_)) => dcx.struct_span_warn(attr_sp, msg),
-        // `.forget_guarantee()` needed to get these two arms to match types. Because of how
-        // locally close the `.emit()` call is I'm comfortable with it, but if it can be
-        // reworked in the future to not need it, it'd be nice.
-        _ => dcx.struct_span_err(attr_sp, msg).forget_guarantee(),
+        Some(ast::ItemKind::MacCall(_)) => Level::Warning(None),
+        _ => Level::Error { lint: false },
     };
+    let mut err = DiagnosticBuilder::<()>::new(dcx, level, msg);
+    err.set_span(attr_sp);
     if let Some(item) = item {
         err.span_label(
             item.span,

compiler/rustc_codegen_cranelift/Cargo.lock

@@ -45,18 +45,18 @@ checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd"
 
 [[package]]
 name = "cranelift-bforest"
-version = "0.102.0"
+version = "0.103.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "76eb38f2af690b5a4411d9a8782b6d77dabff3ca939e0518453ab9f9a4392d41"
+checksum = "7c22542c0b95bd3302f7ed6839869c561f2324bac2fd5e7e99f5cfa65fdc8b92"
 dependencies = [
  "cranelift-entity",
 ]
 
 [[package]]
 name = "cranelift-codegen"
-version = "0.102.0"
+version = "0.103.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "39526c036b92912417e8931f52c1e235796688068d3efdbbd8b164f299d19156"
+checksum = "6b3db903ef2e9c8a4de2ea6db5db052c7857282952f9df604aa55d169e6000d8"
 dependencies = [
  "bumpalo",
  "cranelift-bforest",
@@ -75,39 +75,39 @@ dependencies = [
 
 [[package]]
 name = "cranelift-codegen-meta"
-version = "0.102.0"
+version = "0.103.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "fdb0deedc9fccf2db53a5a3c9c9d0163e44143b0d004dca9bf6ab6a0024cd79a"
+checksum = "6590feb5a1d6438f974bf6a5ac4dddf69fca14e1f07f3265d880f69e61a94463"
 dependencies = [
  "cranelift-codegen-shared",
 ]
 
 [[package]]
 name = "cranelift-codegen-shared"
-version = "0.102.0"
+version = "0.103.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "cea2d1b274e45aa8e61e9103efa1ba82d4b5a19d12bd1fd10744c3b7380ba3ff"
+checksum = "7239038c56fafe77fddc8788fc8533dd6c474dc5bdc5637216404f41ba807330"
 
 [[package]]
 name = "cranelift-control"
-version = "0.102.0"
+version = "0.103.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6ea5977559a71e63db79a263f0e81a89b996e8a38212c4281e37dd1dbaa8b65c"
+checksum = "f7dc9c595341404d381d27a3d950160856b35b402275f0c3990cd1ad683c8053"
 dependencies = [
  "arbitrary",
 ]
 
 [[package]]
 name = "cranelift-entity"
-version = "0.102.0"
+version = "0.103.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2f871ada808b58158d84dfc43a6a2e2d2756baaf4ed1c51fd969ca8330e6ca5c"
+checksum = "44e3ee532fc4776c69bcedf7e62f9632cbb3f35776fa9a525cdade3195baa3f7"
 
 [[package]]
 name = "cranelift-frontend"
-version = "0.102.0"
+version = "0.103.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e8e6890f587ef59824b3debe577e68fdf9b307b3808c54b8d93a18fd0b70941b"
+checksum = "a612c94d09e653662ec37681dc2d6fd2b9856e6df7147be0afc9aabb0abf19df"
 dependencies = [
  "cranelift-codegen",
  "log",
@@ -117,15 +117,15 @@ dependencies = [
 
 [[package]]
 name = "cranelift-isle"
-version = "0.102.0"
+version = "0.103.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a8d5fc6d5d3b52d1917002b17a8ecce448c2621b5bf394bb4e77e2f676893537"
+checksum = "85db9830abeb1170b7d29b536ffd55af1d4d26ac8a77570b5d1aca003bf225cc"
 
 [[package]]
 name = "cranelift-jit"
-version = "0.102.0"
+version = "0.103.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e8a2d7744f743f59d9646d7589ad22ea17ed0d71e04906eb77c31e99bc13bd8b"
+checksum = "4946271f1055e26544ef8c90fa24776f201566419dfac4b3962c39d5a804ff67"
 dependencies = [
  "anyhow",
  "cranelift-codegen",
@@ -143,9 +143,9 @@ dependencies = [
 
 [[package]]
 name = "cranelift-module"
-version = "0.102.0"
+version = "0.103.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b96cb196334698e612c197d7d0ae59af5e07667306ec20d7be414717db400873"
+checksum = "cb7e3bdae2597556e59edeb8ecb62eb32c7e054c4f042d393732902979db69c3"
 dependencies = [
  "anyhow",
  "cranelift-codegen",
@@ -154,9 +154,9 @@ dependencies = [
 
 [[package]]
 name = "cranelift-native"
-version = "0.102.0"
+version = "0.103.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "3e10c2e7faa65d4ae7de9a83b44f2c31aca7dc638e17d0a79572fdf8103d720b"
+checksum = "301ef0edafeaeda5771a5d2db64ac53e1818ae3111220a185677025fe91db4a1"
 dependencies = [
  "cranelift-codegen",
  "libc",
@@ -165,9 +165,9 @@ dependencies = [
 
 [[package]]
 name = "cranelift-object"
-version = "0.102.0"
+version = "0.103.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "83ce94e18756058af8a66e3c0ba1123ae15517c72162d8060d0cb0974642adf2"
+checksum = "59e0ee3d013728903e0c513c31afa389b559bfd4fe8a44f80335c799e3132a41"
 dependencies = [
  "anyhow",
  "cranelift-codegen",
@@ -374,9 +374,9 @@ checksum = "49874b5167b65d7193b8aba1567f5c7d93d001cafc34600cee003eda787e483f"
 
 [[package]]
 name = "wasmtime-jit-icache-coherence"
-version = "15.0.0"
+version = "16.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b73ad1395eda136baec5ece7e079e0536a82ef73488e345456cc9b89858ad0ec"
+checksum = "6b6d197fcc34ad32ed440e1f9552fd57d1f377d9699d31dee1b5b457322c1f8a"
 dependencies = [
  "cfg-if",
  "libc",

compiler/rustc_codegen_cranelift/Cargo.toml

@@ -8,12 +8,12 @@ crate-type = ["dylib"]
 
 [dependencies]
 # These have to be in sync with each other
-cranelift-codegen = { version = "0.102", default-features = false, features = ["std", "unwind", "all-arch"] }
-cranelift-frontend = { version = "0.102" }
-cranelift-module = { version = "0.102" }
-cranelift-native = { version = "0.102" }
-cranelift-jit = { version = "0.102", optional = true }
-cranelift-object = { version = "0.102" }
+cranelift-codegen = { version = "0.103", default-features = false, features = ["std", "unwind", "all-arch"] }
+cranelift-frontend = { version = "0.103" }
+cranelift-module = { version = "0.103" }
+cranelift-native = { version = "0.103" }
+cranelift-jit = { version = "0.103", optional = true }
+cranelift-object = { version = "0.103" }
 target-lexicon = "0.12.0"
 gimli = { version = "0.28", default-features = false, features = ["write"]}
 object = { version = "0.32", default-features = false, features = ["std", "read_core", "write", "archive", "coff", "elf", "macho", "pe"] }

compiler/rustc_codegen_cranelift/example/mini_core_hello_world.rs

@@ -538,261 +538,38 @@ pub enum E1 {
 pub enum E2<X> {
     V1 { f: bool },
 
-    /*_00*/ _01(X),
-    _02(X),
-    _03(X),
-    _04(X),
-    _05(X),
-    _06(X),
-    _07(X),
-    _08(X),
-    _09(X),
-    _0A(X),
-    _0B(X),
-    _0C(X),
-    _0D(X),
-    _0E(X),
-    _0F(X),
-    _10(X),
-    _11(X),
-    _12(X),
-    _13(X),
-    _14(X),
-    _15(X),
-    _16(X),
-    _17(X),
-    _18(X),
-    _19(X),
-    _1A(X),
-    _1B(X),
-    _1C(X),
-    _1D(X),
-    _1E(X),
-    _1F(X),
-    _20(X),
-    _21(X),
-    _22(X),
-    _23(X),
-    _24(X),
-    _25(X),
-    _26(X),
-    _27(X),
-    _28(X),
-    _29(X),
-    _2A(X),
-    _2B(X),
-    _2C(X),
-    _2D(X),
-    _2E(X),
-    _2F(X),
-    _30(X),
-    _31(X),
-    _32(X),
-    _33(X),
-    _34(X),
-    _35(X),
-    _36(X),
-    _37(X),
-    _38(X),
-    _39(X),
-    _3A(X),
-    _3B(X),
-    _3C(X),
-    _3D(X),
-    _3E(X),
-    _3F(X),
-    _40(X),
-    _41(X),
-    _42(X),
-    _43(X),
-    _44(X),
-    _45(X),
-    _46(X),
-    _47(X),
-    _48(X),
-    _49(X),
-    _4A(X),
-    _4B(X),
-    _4C(X),
-    _4D(X),
-    _4E(X),
-    _4F(X),
-    _50(X),
-    _51(X),
-    _52(X),
-    _53(X),
-    _54(X),
-    _55(X),
-    _56(X),
-    _57(X),
-    _58(X),
-    _59(X),
-    _5A(X),
-    _5B(X),
-    _5C(X),
-    _5D(X),
-    _5E(X),
-    _5F(X),
-    _60(X),
-    _61(X),
-    _62(X),
-    _63(X),
-    _64(X),
-    _65(X),
-    _66(X),
-    _67(X),
-    _68(X),
-    _69(X),
-    _6A(X),
-    _6B(X),
-    _6C(X),
-    _6D(X),
-    _6E(X),
-    _6F(X),
-    _70(X),
-    _71(X),
-    _72(X),
-    _73(X),
-    _74(X),
-    _75(X),
-    _76(X),
-    _77(X),
-    _78(X),
-    _79(X),
-    _7A(X),
-    _7B(X),
-    _7C(X),
-    _7D(X),
-    _7E(X),
-    _7F(X),
-    _80(X),
-    _81(X),
-    _82(X),
-    _83(X),
-    _84(X),
-    _85(X),
-    _86(X),
-    _87(X),
-    _88(X),
-    _89(X),
-    _8A(X),
-    _8B(X),
-    _8C(X),
-    _8D(X),
-    _8E(X),
-    _8F(X),
-    _90(X),
-    _91(X),
-    _92(X),
-    _93(X),
-    _94(X),
-    _95(X),
-    _96(X),
-    _97(X),
-    _98(X),
-    _99(X),
-    _9A(X),
-    _9B(X),
-    _9C(X),
-    _9D(X),
-    _9E(X),
-    _9F(X),
-    _A0(X),
-    _A1(X),
-    _A2(X),
-    _A3(X),
-    _A4(X),
-    _A5(X),
-    _A6(X),
-    _A7(X),
-    _A8(X),
-    _A9(X),
-    _AA(X),
-    _AB(X),
-    _AC(X),
-    _AD(X),
-    _AE(X),
-    _AF(X),
-    _B0(X),
-    _B1(X),
-    _B2(X),
-    _B3(X),
-    _B4(X),
-    _B5(X),
-    _B6(X),
-    _B7(X),
-    _B8(X),
-    _B9(X),
-    _BA(X),
-    _BB(X),
-    _BC(X),
-    _BD(X),
-    _BE(X),
-    _BF(X),
-    _C0(X),
-    _C1(X),
-    _C2(X),
-    _C3(X),
-    _C4(X),
-    _C5(X),
-    _C6(X),
-    _C7(X),
-    _C8(X),
-    _C9(X),
-    _CA(X),
-    _CB(X),
-    _CC(X),
-    _CD(X),
-    _CE(X),
-    _CF(X),
-    _D0(X),
-    _D1(X),
-    _D2(X),
-    _D3(X),
-    _D4(X),
-    _D5(X),
-    _D6(X),
-    _D7(X),
-    _D8(X),
-    _D9(X),
-    _DA(X),
-    _DB(X),
-    _DC(X),
-    _DD(X),
-    _DE(X),
-    _DF(X),
-    _E0(X),
-    _E1(X),
-    _E2(X),
-    _E3(X),
-    _E4(X),
-    _E5(X),
-    _E6(X),
-    _E7(X),
-    _E8(X),
-    _E9(X),
-    _EA(X),
-    _EB(X),
-    _EC(X),
-    _ED(X),
-    _EE(X),
-    _EF(X),
-    _F0(X),
-    _F1(X),
-    _F2(X),
-    _F3(X),
-    _F4(X),
-    _F5(X),
-    _F6(X),
-    _F7(X),
-    _F8(X),
-    _F9(X),
-    _FA(X),
-    _FB(X),
-    _FC(X),
-    _FD(X),
-    _FE(X),
-    _FF(X),
+    /*_00*/ _01(X), _02(X), _03(X), _04(X), _05(X), _06(X), _07(X),
+    _08(X), _09(X), _0A(X), _0B(X), _0C(X), _0D(X), _0E(X), _0F(X),
+    _10(X), _11(X), _12(X), _13(X), _14(X), _15(X), _16(X), _17(X),
+    _18(X), _19(X), _1A(X), _1B(X), _1C(X), _1D(X), _1E(X), _1F(X),
+    _20(X), _21(X), _22(X), _23(X), _24(X), _25(X), _26(X), _27(X),
+    _28(X), _29(X), _2A(X), _2B(X), _2C(X), _2D(X), _2E(X), _2F(X),
+    _30(X), _31(X), _32(X), _33(X), _34(X), _35(X), _36(X), _37(X),
+    _38(X), _39(X), _3A(X), _3B(X), _3C(X), _3D(X), _3E(X), _3F(X),
+    _40(X), _41(X), _42(X), _43(X), _44(X), _45(X), _46(X), _47(X),
+    _48(X), _49(X), _4A(X), _4B(X), _4C(X), _4D(X), _4E(X), _4F(X),
+    _50(X), _51(X), _52(X), _53(X), _54(X), _55(X), _56(X), _57(X),
+    _58(X), _59(X), _5A(X), _5B(X), _5C(X), _5D(X), _5E(X), _5F(X),
+    _60(X), _61(X), _62(X), _63(X), _64(X), _65(X), _66(X), _67(X),
+    _68(X), _69(X), _6A(X), _6B(X), _6C(X), _6D(X), _6E(X), _6F(X),
+    _70(X), _71(X), _72(X), _73(X), _74(X), _75(X), _76(X), _77(X),
+    _78(X), _79(X), _7A(X), _7B(X), _7C(X), _7D(X), _7E(X), _7F(X),
+    _80(X), _81(X), _82(X), _83(X), _84(X), _85(X), _86(X), _87(X),
+    _88(X), _89(X), _8A(X), _8B(X), _8C(X), _8D(X), _8E(X), _8F(X),
+    _90(X), _91(X), _92(X), _93(X), _94(X), _95(X), _96(X), _97(X),
+    _98(X), _99(X), _9A(X), _9B(X), _9C(X), _9D(X), _9E(X), _9F(X),
+    _A0(X), _A1(X), _A2(X), _A3(X), _A4(X), _A5(X), _A6(X), _A7(X),
+    _A8(X), _A9(X), _AA(X), _AB(X), _AC(X), _AD(X), _AE(X), _AF(X),
+    _B0(X), _B1(X), _B2(X), _B3(X), _B4(X), _B5(X), _B6(X), _B7(X),
+    _B8(X), _B9(X), _BA(X), _BB(X), _BC(X), _BD(X), _BE(X), _BF(X),
+    _C0(X), _C1(X), _C2(X), _C3(X), _C4(X), _C5(X), _C6(X), _C7(X),
+    _C8(X), _C9(X), _CA(X), _CB(X), _CC(X), _CD(X), _CE(X), _CF(X),
+    _D0(X), _D1(X), _D2(X), _D3(X), _D4(X), _D5(X), _D6(X), _D7(X),
+    _D8(X), _D9(X), _DA(X), _DB(X), _DC(X), _DD(X), _DE(X), _DF(X),
+    _E0(X), _E1(X), _E2(X), _E3(X), _E4(X), _E5(X), _E6(X), _E7(X),
+    _E8(X), _E9(X), _EA(X), _EB(X), _EC(X), _ED(X), _EE(X), _EF(X),
+    _F0(X), _F1(X), _F2(X), _F3(X), _F4(X), _F5(X), _F6(X), _F7(X),
+    _F8(X), _F9(X), _FA(X), _FB(X), _FC(X), _FD(X), _FE(X), _FF(X),
 
     V3,
     V4,

compiler/rustc_codegen_cranelift/rust-toolchain

@@ -1,3 +1,3 @@
 [toolchain]
-channel = "nightly-2023-12-19"
+channel = "nightly-2023-12-24"
 components = ["rust-src", "rustc-dev", "llvm-tools"]

compiler/rustc_codegen_cranelift/scripts/test_rustc_tests.sh

@@ -31,6 +31,7 @@ rm tests/ui/parser/unclosed-delimiter-in-dep.rs # submodule contains //~ERROR
 # FIXME add needs-unwind to these tests
 rm -r tests/run-make/libtest-junit
 rm tests/ui/asm/may_unwind.rs
+rm tests/ui/stable-mir-print/basic_function.rs
 
 # extra warning about -Cpanic=abort for proc macros
 rm tests/ui/proc-macro/crt-static.rs
@@ -44,7 +45,6 @@ rm tests/ui/proc-macro/no-mangle-in-proc-macro-issue-111888.rs
 # vendor intrinsics
 rm tests/ui/sse2.rs # CodegenBackend::target_features not yet implemented
 rm tests/ui/simd/array-type.rs # "Index argument for `simd_insert` is not a constant"
-rm tests/ui/simd/masked-load-store.rs
 
 # exotic linkages
 rm tests/ui/issues/issue-33992.rs # unsupported linkages
@@ -80,6 +80,7 @@ rm -r tests/run-make/codegen-options-parsing
 rm -r tests/run-make/lto-*
 rm -r tests/run-make/reproducible-build-2
 rm -r tests/run-make/issue-109934-lto-debuginfo
+rm -r tests/run-make/no-builtins-lto
 
 # optimization tests
 # ==================

compiler/rustc_codegen_cranelift/src/base.rs

@@ -179,7 +179,7 @@ pub(crate) fn compile_fn(
                 let early_dcx = rustc_session::EarlyDiagCtxt::new(
                     rustc_session::config::ErrorOutputType::default(),
                 );
-                early_dcx.early_error(format!(
+                early_dcx.early_fatal(format!(
                     "backend implementation limit exceeded while compiling {name}",
                     name = codegened_func.symbol_name
                 ));

compiler/rustc_codegen_cranelift/src/intrinsics/simd.rs

@@ -962,6 +962,37 @@ pub(super) fn codegen_simd_intrinsic_call<'tcx>(
             }
         }
 
+        sym::simd_masked_store => {
+            intrinsic_args!(fx, args => (mask, ptr, val); intrinsic);
+
+            let (val_lane_count, val_lane_ty) = val.layout().ty.simd_size_and_type(fx.tcx);
+            let (mask_lane_count, _mask_lane_ty) = mask.layout().ty.simd_size_and_type(fx.tcx);
+            assert_eq!(val_lane_count, mask_lane_count);
+            let lane_clif_ty = fx.clif_type(val_lane_ty).unwrap();
+            let ptr_val = ptr.load_scalar(fx);
+
+            for lane_idx in 0..val_lane_count {
+                let val_lane = val.value_lane(fx, lane_idx).load_scalar(fx);
+                let mask_lane = mask.value_lane(fx, lane_idx).load_scalar(fx);
+
+                let if_enabled = fx.bcx.create_block();
+                let next = fx.bcx.create_block();
+
+                fx.bcx.ins().brif(mask_lane, if_enabled, &[], next, &[]);
+                fx.bcx.seal_block(if_enabled);
+
+                fx.bcx.switch_to_block(if_enabled);
+                let offset = lane_idx as i32 * lane_clif_ty.bytes() as i32;
+                fx.bcx.ins().store(MemFlags::trusted(), val_lane, ptr_val, Offset32::new(offset));
+                fx.bcx.ins().jump(next, &[]);
+
+                fx.bcx.seal_block(next);
+                fx.bcx.switch_to_block(next);
+
+                fx.bcx.ins().nop();
+            }
+        }
+
         sym::simd_gather => {
             intrinsic_args!(fx, args => (val, ptr, mask); intrinsic);
 
@@ -1057,7 +1088,7 @@ pub(super) fn codegen_simd_intrinsic_call<'tcx>(
         }
 
         sym::simd_scatter => {
-            intrinsic_args!(fx, args => (mask, ptr, val); intrinsic);
+            intrinsic_args!(fx, args => (val, ptr, mask); intrinsic);
 
             let (val_lane_count, _val_lane_ty) = val.layout().ty.simd_size_and_type(fx.tcx);
             let (ptr_lane_count, _ptr_lane_ty) = ptr.layout().ty.simd_size_and_type(fx.tcx);

compiler/rustc_codegen_cranelift/src/lib.rs

@@ -1,6 +1,6 @@
-#![cfg_attr(all(doc, not(bootstrap)), allow(internal_features))]
-#![cfg_attr(all(doc, not(bootstrap)), feature(rustdoc_internals))]
-#![cfg_attr(all(doc, not(bootstrap)), doc(rust_logo))]
+#![cfg_attr(doc, allow(internal_features))]
+#![cfg_attr(doc, feature(rustdoc_internals))]
+#![cfg_attr(doc, doc(rust_logo))]
 #![feature(rustc_private)]
 // Note: please avoid adding other feature gates where possible
 #![warn(rust_2018_idioms)]

compiler/rustc_codegen_gcc/src/errors.rs

@@ -1,6 +1,6 @@
 use rustc_errors::{
-    DiagCtxt, DiagnosticArgValue, DiagnosticBuilder, ErrorGuaranteed, IntoDiagnostic,
-    IntoDiagnosticArg,
+    DiagCtxt, DiagnosticArgValue, DiagnosticBuilder, EmissionGuarantee, IntoDiagnostic,
+    IntoDiagnosticArg, Level,
 };
 use rustc_macros::{Diagnostic, Subdiagnostic};
 use rustc_span::Span;
@@ -111,9 +111,13 @@ pub(crate) struct TargetFeatureDisableOrEnable<'a> {
 #[help(codegen_gcc_missing_features)]
 pub(crate) struct MissingFeatures;
 
-impl IntoDiagnostic<'_, ErrorGuaranteed> for TargetFeatureDisableOrEnable<'_> {
-    fn into_diagnostic(self, dcx: &'_ DiagCtxt) -> DiagnosticBuilder<'_, ErrorGuaranteed> {
-        let mut diag = dcx.struct_err(fluent::codegen_gcc_target_feature_disable_or_enable);
+impl<G: EmissionGuarantee> IntoDiagnostic<'_, G> for TargetFeatureDisableOrEnable<'_> {
+    fn into_diagnostic(self, dcx: &'_ DiagCtxt, level: Level) -> DiagnosticBuilder<'_, G> {
+        let mut diag = DiagnosticBuilder::new(
+            dcx,
+            level,
+            fluent::codegen_gcc_target_feature_disable_or_enable
+        );
         if let Some(span) = self.span {
             diag.set_span(span);
         };

compiler/rustc_codegen_llvm/src/errors.rs

@@ -4,9 +4,7 @@ use std::path::Path;
 
 use crate::fluent_generated as fluent;
 use rustc_data_structures::small_c_str::SmallCStr;
-use rustc_errors::{
-    DiagCtxt, DiagnosticBuilder, EmissionGuarantee, ErrorGuaranteed, FatalError, IntoDiagnostic,
-};
+use rustc_errors::{DiagCtxt, DiagnosticBuilder, EmissionGuarantee, IntoDiagnostic, Level};
 use rustc_macros::{Diagnostic, Subdiagnostic};
 use rustc_span::Span;
 
@@ -101,13 +99,14 @@ pub(crate) struct DynamicLinkingWithLTO;
 
 pub(crate) struct ParseTargetMachineConfig<'a>(pub LlvmError<'a>);
 
-impl IntoDiagnostic<'_, FatalError> for ParseTargetMachineConfig<'_> {
-    fn into_diagnostic(self, dcx: &'_ DiagCtxt) -> DiagnosticBuilder<'_, FatalError> {
-        let diag: DiagnosticBuilder<'_, FatalError> = self.0.into_diagnostic(dcx);
-        let (message, _) = diag.styled_message().first().expect("`LlvmError` with no message");
+impl<G: EmissionGuarantee> IntoDiagnostic<'_, G> for ParseTargetMachineConfig<'_> {
+    fn into_diagnostic(self, dcx: &'_ DiagCtxt, level: Level) -> DiagnosticBuilder<'_, G> {
+        let diag: DiagnosticBuilder<'_, G> = self.0.into_diagnostic(dcx, level);
+        let (message, _) = diag.messages().first().expect("`LlvmError` with no message");
         let message = dcx.eagerly_translate_to_string(message.clone(), diag.args());
 
-        let mut diag = dcx.struct_almost_fatal(fluent::codegen_llvm_parse_target_machine_config);
+        let mut diag =
+            DiagnosticBuilder::new(dcx, level, fluent::codegen_llvm_parse_target_machine_config);
         diag.set_arg("error", message);
         diag
     }
@@ -123,9 +122,13 @@ pub(crate) struct TargetFeatureDisableOrEnable<'a> {
 #[help(codegen_llvm_missing_features)]
 pub(crate) struct MissingFeatures;
 
-impl IntoDiagnostic<'_, ErrorGuaranteed> for TargetFeatureDisableOrEnable<'_> {
-    fn into_diagnostic(self, dcx: &'_ DiagCtxt) -> DiagnosticBuilder<'_, ErrorGuaranteed> {
-        let mut diag = dcx.struct_err(fluent::codegen_llvm_target_feature_disable_or_enable);
+impl<G: EmissionGuarantee> IntoDiagnostic<'_, G> for TargetFeatureDisableOrEnable<'_> {
+    fn into_diagnostic(self, dcx: &'_ DiagCtxt, level: Level) -> DiagnosticBuilder<'_, G> {
+        let mut diag = DiagnosticBuilder::new(
+            dcx,
+            level,
+            fluent::codegen_llvm_target_feature_disable_or_enable,
+        );
         if let Some(span) = self.span {
             diag.set_span(span);
         };
@@ -184,7 +187,7 @@ pub enum LlvmError<'a> {
 pub(crate) struct WithLlvmError<'a>(pub LlvmError<'a>, pub String);
 
 impl<G: EmissionGuarantee> IntoDiagnostic<'_, G> for WithLlvmError<'_> {
-    fn into_diagnostic(self, dcx: &'_ DiagCtxt) -> DiagnosticBuilder<'_, G> {
+    fn into_diagnostic(self, dcx: &'_ DiagCtxt, level: Level) -> DiagnosticBuilder<'_, G> {
         use LlvmError::*;
         let msg_with_llvm_err = match &self.0 {
             WriteOutput { .. } => fluent::codegen_llvm_write_output_with_llvm_err,
@@ -201,7 +204,7 @@ impl<G: EmissionGuarantee> IntoDiagnostic<'_, G> for WithLlvmError<'_> {
             PrepareThinLtoModule => fluent::codegen_llvm_prepare_thin_lto_module_with_llvm_err,
             ParseBitcode => fluent::codegen_llvm_parse_bitcode_with_llvm_err,
         };
-        let mut diag = self.0.into_diagnostic(dcx);
+        let mut diag = self.0.into_diagnostic(dcx, level);
         diag.set_primary_message(msg_with_llvm_err);
         diag.set_arg("llvm_err", self.1);
         diag

compiler/rustc_codegen_llvm/src/lib.rs

@@ -8,7 +8,6 @@
 #![feature(rustdoc_internals)]
 #![doc(rust_logo)]
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/")]
-#![cfg_attr(bootstrap, feature(c_str_literals))]
 #![feature(exact_size_is_empty)]
 #![feature(extern_types)]
 #![feature(hash_raw_entry)]

compiler/rustc_codegen_ssa/src/back/write.rs

@@ -15,7 +15,7 @@ use rustc_data_structures::profiling::{SelfProfilerRef, VerboseTimingGuard};
 use rustc_data_structures::sync::Lrc;
 use rustc_errors::emitter::Emitter;
 use rustc_errors::{translation::Translate, DiagCtxt, DiagnosticId, FatalError, Level};
-use rustc_errors::{DiagnosticMessage, Style};
+use rustc_errors::{DiagnosticBuilder, DiagnosticMessage, Style};
 use rustc_fs_util::link_or_copy;
 use rustc_hir::def_id::{CrateNum, LOCAL_CRATE};
 use rustc_incremental::{
@@ -986,7 +986,7 @@ pub struct CguMessage;
 type DiagnosticArgName<'source> = Cow<'source, str>;
 
 struct Diagnostic {
-    msg: Vec<(DiagnosticMessage, Style)>,
+    msgs: Vec<(DiagnosticMessage, Style)>,
     args: FxHashMap<DiagnosticArgName<'static>, rustc_errors::DiagnosticArgValue<'static>>,
     code: Option<DiagnosticId>,
     lvl: Level,
@@ -1799,14 +1799,14 @@ impl Emitter for SharedEmitter {
         let args: FxHashMap<Cow<'_, str>, rustc_errors::DiagnosticArgValue<'_>> =
             diag.args().map(|(name, arg)| (name.clone(), arg.clone())).collect();
         drop(self.sender.send(SharedEmitterMessage::Diagnostic(Diagnostic {
-            msg: diag.message.clone(),
+            msgs: diag.messages.clone(),
             args: args.clone(),
             code: diag.code.clone(),
             lvl: diag.level(),
         })));
         for child in &diag.children {
             drop(self.sender.send(SharedEmitterMessage::Diagnostic(Diagnostic {
-                msg: child.message.clone(),
+                msgs: child.messages.clone(),
                 args: args.clone(),
                 code: None,
                 lvl: child.level,
@@ -1838,7 +1838,7 @@ impl SharedEmitterMain {
             match message {
                 Ok(SharedEmitterMessage::Diagnostic(diag)) => {
                     let dcx = sess.dcx();
-                    let mut d = rustc_errors::Diagnostic::new_with_messages(diag.lvl, diag.msg);
+                    let mut d = rustc_errors::Diagnostic::new_with_messages(diag.lvl, diag.msgs);
                     if let Some(code) = diag.code {
                         d.code(code);
                     }
@@ -1846,14 +1846,14 @@ impl SharedEmitterMain {
                     dcx.emit_diagnostic(d);
                 }
                 Ok(SharedEmitterMessage::InlineAsmError(cookie, msg, level, source)) => {
-                    let msg = msg.strip_prefix("error: ").unwrap_or(&msg).to_string();
-
-                    let mut err = match level {
-                        Level::Error { lint: false } => sess.struct_err(msg).forget_guarantee(),
-                        Level::Warning(_) => sess.struct_warn(msg),
-                        Level::Note => sess.struct_note(msg),
+                    let err_level = match level {
+                        Level::Error { lint: false } => rustc_errors::Level::Error { lint: false },
+                        Level::Warning(_) => rustc_errors::Level::Warning(None),
+                        Level::Note => rustc_errors::Level::Note,
                         _ => bug!("Invalid inline asm diagnostic level"),
                     };
+                    let msg = msg.strip_prefix("error: ").unwrap_or(&msg).to_string();
+                    let mut err = DiagnosticBuilder::<()>::new(sess.dcx(), err_level, msg);
 
                     // If the cookie is 0 then we don't have span information.
                     if cookie != 0 {

compiler/rustc_codegen_ssa/src/debuginfo/type_names.rs

@@ -15,7 +15,7 @@ use rustc_data_structures::fx::FxHashSet;
 use rustc_data_structures::stable_hasher::{Hash64, HashStable, StableHasher};
 use rustc_hir::def_id::DefId;
 use rustc_hir::definitions::{DefPathData, DefPathDataName, DisambiguatedDefPathData};
-use rustc_hir::{CoroutineKind, CoroutineSource, Mutability};
+use rustc_hir::{CoroutineDesugaring, CoroutineKind, CoroutineSource, Mutability};
 use rustc_middle::ty::layout::{IntegerExt, TyAndLayout};
 use rustc_middle::ty::{self, ExistentialProjection, ParamEnv, Ty, TyCtxt};
 use rustc_middle::ty::{GenericArgKind, GenericArgsRef};
@@ -560,15 +560,31 @@ pub fn push_item_name(tcx: TyCtxt<'_>, def_id: DefId, qualified: bool, output: &
 
 fn coroutine_kind_label(coroutine_kind: Option<CoroutineKind>) -> &'static str {
     match coroutine_kind {
-        Some(CoroutineKind::Gen(CoroutineSource::Block)) => "gen_block",
-        Some(CoroutineKind::Gen(CoroutineSource::Closure)) => "gen_closure",
-        Some(CoroutineKind::Gen(CoroutineSource::Fn)) => "gen_fn",
-        Some(CoroutineKind::Async(CoroutineSource::Block)) => "async_block",
-        Some(CoroutineKind::Async(CoroutineSource::Closure)) => "async_closure",
-        Some(CoroutineKind::Async(CoroutineSource::Fn)) => "async_fn",
-        Some(CoroutineKind::AsyncGen(CoroutineSource::Block)) => "async_gen_block",
-        Some(CoroutineKind::AsyncGen(CoroutineSource::Closure)) => "async_gen_closure",
-        Some(CoroutineKind::AsyncGen(CoroutineSource::Fn)) => "async_gen_fn",
+        Some(CoroutineKind::Desugared(CoroutineDesugaring::Gen, CoroutineSource::Block)) => {
+            "gen_block"
+        }
+        Some(CoroutineKind::Desugared(CoroutineDesugaring::Gen, CoroutineSource::Closure)) => {
+            "gen_closure"
+        }
+        Some(CoroutineKind::Desugared(CoroutineDesugaring::Gen, CoroutineSource::Fn)) => "gen_fn",
+        Some(CoroutineKind::Desugared(CoroutineDesugaring::Async, CoroutineSource::Block)) => {
+            "async_block"
+        }
+        Some(CoroutineKind::Desugared(CoroutineDesugaring::Async, CoroutineSource::Closure)) => {
+            "async_closure"
+        }
+        Some(CoroutineKind::Desugared(CoroutineDesugaring::Async, CoroutineSource::Fn)) => {
+            "async_fn"
+        }
+        Some(CoroutineKind::Desugared(CoroutineDesugaring::AsyncGen, CoroutineSource::Block)) => {
+            "async_gen_block"
+        }
+        Some(CoroutineKind::Desugared(CoroutineDesugaring::AsyncGen, CoroutineSource::Closure)) => {
+            "async_gen_closure"
+        }
+        Some(CoroutineKind::Desugared(CoroutineDesugaring::AsyncGen, CoroutineSource::Fn)) => {
+            "async_gen_fn"
+        }
         Some(CoroutineKind::Coroutine) => "coroutine",
         None => "closure",
     }

compiler/rustc_codegen_ssa/src/errors.rs

@@ -4,8 +4,8 @@ use crate::assert_module_sources::CguReuse;
 use crate::back::command::Command;
 use crate::fluent_generated as fluent;
 use rustc_errors::{
-    DiagCtxt, DiagnosticArgValue, DiagnosticBuilder, ErrorGuaranteed, IntoDiagnostic,
-    IntoDiagnosticArg,
+    DiagCtxt, DiagnosticArgValue, DiagnosticBuilder, EmissionGuarantee, IntoDiagnostic,
+    IntoDiagnosticArg, Level,
 };
 use rustc_macros::Diagnostic;
 use rustc_middle::ty::layout::LayoutError;
@@ -209,192 +209,193 @@ pub enum LinkRlibError {
 
 pub struct ThorinErrorWrapper(pub thorin::Error);
 
-impl IntoDiagnostic<'_> for ThorinErrorWrapper {
-    fn into_diagnostic(self, dcx: &DiagCtxt) -> DiagnosticBuilder<'_, ErrorGuaranteed> {
+impl<G: EmissionGuarantee> IntoDiagnostic<'_, G> for ThorinErrorWrapper {
+    fn into_diagnostic(self, dcx: &DiagCtxt, level: Level) -> DiagnosticBuilder<'_, G> {
+        let build = |msg| DiagnosticBuilder::new(dcx, level, msg);
         let mut diag;
         match self.0 {
             thorin::Error::ReadInput(_) => {
-                diag = dcx.struct_err(fluent::codegen_ssa_thorin_read_input_failure);
+                diag = build(fluent::codegen_ssa_thorin_read_input_failure);
                 diag
             }
             thorin::Error::ParseFileKind(_) => {
-                diag = dcx.struct_err(fluent::codegen_ssa_thorin_parse_input_file_kind);
+                diag = build(fluent::codegen_ssa_thorin_parse_input_file_kind);
                 diag
             }
             thorin::Error::ParseObjectFile(_) => {
-                diag = dcx.struct_err(fluent::codegen_ssa_thorin_parse_input_object_file);
+                diag = build(fluent::codegen_ssa_thorin_parse_input_object_file);
                 diag
             }
             thorin::Error::ParseArchiveFile(_) => {
-                diag = dcx.struct_err(fluent::codegen_ssa_thorin_parse_input_archive_file);
+                diag = build(fluent::codegen_ssa_thorin_parse_input_archive_file);
                 diag
             }
             thorin::Error::ParseArchiveMember(_) => {
-                diag = dcx.struct_err(fluent::codegen_ssa_thorin_parse_archive_member);
+                diag = build(fluent::codegen_ssa_thorin_parse_archive_member);
                 diag
             }
             thorin::Error::InvalidInputKind => {
-                diag = dcx.struct_err(fluent::codegen_ssa_thorin_invalid_input_kind);
+                diag = build(fluent::codegen_ssa_thorin_invalid_input_kind);
                 diag
             }
             thorin::Error::DecompressData(_) => {
-                diag = dcx.struct_err(fluent::codegen_ssa_thorin_decompress_data);
+                diag = build(fluent::codegen_ssa_thorin_decompress_data);
                 diag
             }
             thorin::Error::NamelessSection(_, offset) => {
-                diag = dcx.struct_err(fluent::codegen_ssa_thorin_section_without_name);
+                diag = build(fluent::codegen_ssa_thorin_section_without_name);
                 diag.set_arg("offset", format!("0x{offset:08x}"));
                 diag
             }
             thorin::Error::RelocationWithInvalidSymbol(section, offset) => {
-                diag = dcx.struct_err(fluent::codegen_ssa_thorin_relocation_with_invalid_symbol);
+                diag = build(fluent::codegen_ssa_thorin_relocation_with_invalid_symbol);
                 diag.set_arg("section", section);
                 diag.set_arg("offset", format!("0x{offset:08x}"));
                 diag
             }
             thorin::Error::MultipleRelocations(section, offset) => {
-                diag = dcx.struct_err(fluent::codegen_ssa_thorin_multiple_relocations);
+                diag = build(fluent::codegen_ssa_thorin_multiple_relocations);
                 diag.set_arg("section", section);
                 diag.set_arg("offset", format!("0x{offset:08x}"));
                 diag
             }
             thorin::Error::UnsupportedRelocation(section, offset) => {
-                diag = dcx.struct_err(fluent::codegen_ssa_thorin_unsupported_relocation);
+                diag = build(fluent::codegen_ssa_thorin_unsupported_relocation);
                 diag.set_arg("section", section);
                 diag.set_arg("offset", format!("0x{offset:08x}"));
                 diag
             }
             thorin::Error::MissingDwoName(id) => {
-                diag = dcx.struct_err(fluent::codegen_ssa_thorin_missing_dwo_name);
+                diag = build(fluent::codegen_ssa_thorin_missing_dwo_name);
                 diag.set_arg("id", format!("0x{id:08x}"));
                 diag
             }
             thorin::Error::NoCompilationUnits => {
-                diag = dcx.struct_err(fluent::codegen_ssa_thorin_no_compilation_units);
+                diag = build(fluent::codegen_ssa_thorin_no_compilation_units);
                 diag
             }
             thorin::Error::NoDie => {
-                diag = dcx.struct_err(fluent::codegen_ssa_thorin_no_die);
+                diag = build(fluent::codegen_ssa_thorin_no_die);
                 diag
             }
             thorin::Error::TopLevelDieNotUnit => {
-                diag = dcx.struct_err(fluent::codegen_ssa_thorin_top_level_die_not_unit);
+                diag = build(fluent::codegen_ssa_thorin_top_level_die_not_unit);
                 diag
             }
             thorin::Error::MissingRequiredSection(section) => {
-                diag = dcx.struct_err(fluent::codegen_ssa_thorin_missing_required_section);
+                diag = build(fluent::codegen_ssa_thorin_missing_required_section);
                 diag.set_arg("section", section);
                 diag
             }
             thorin::Error::ParseUnitAbbreviations(_) => {
-                diag = dcx.struct_err(fluent::codegen_ssa_thorin_parse_unit_abbreviations);
+                diag = build(fluent::codegen_ssa_thorin_parse_unit_abbreviations);
                 diag
             }
             thorin::Error::ParseUnitAttribute(_) => {
-                diag = dcx.struct_err(fluent::codegen_ssa_thorin_parse_unit_attribute);
+                diag = build(fluent::codegen_ssa_thorin_parse_unit_attribute);
                 diag
             }
             thorin::Error::ParseUnitHeader(_) => {
-                diag = dcx.struct_err(fluent::codegen_ssa_thorin_parse_unit_header);
+                diag = build(fluent::codegen_ssa_thorin_parse_unit_header);
                 diag
             }
             thorin::Error::ParseUnit(_) => {
-                diag = dcx.struct_err(fluent::codegen_ssa_thorin_parse_unit);
+                diag = build(fluent::codegen_ssa_thorin_parse_unit);
                 diag
             }
             thorin::Error::IncompatibleIndexVersion(section, format, actual) => {
-                diag = dcx.struct_err(fluent::codegen_ssa_thorin_incompatible_index_version);
+                diag = build(fluent::codegen_ssa_thorin_incompatible_index_version);
                 diag.set_arg("section", section);
                 diag.set_arg("actual", actual);
                 diag.set_arg("format", format);
                 diag
             }
             thorin::Error::OffsetAtIndex(_, index) => {
-                diag = dcx.struct_err(fluent::codegen_ssa_thorin_offset_at_index);
+                diag = build(fluent::codegen_ssa_thorin_offset_at_index);
                 diag.set_arg("index", index);
                 diag
             }
             thorin::Error::StrAtOffset(_, offset) => {
-                diag = dcx.struct_err(fluent::codegen_ssa_thorin_str_at_offset);
+                diag = build(fluent::codegen_ssa_thorin_str_at_offset);
                 diag.set_arg("offset", format!("0x{offset:08x}"));
                 diag
             }
             thorin::Error::ParseIndex(_, section) => {
-                diag = dcx.struct_err(fluent::codegen_ssa_thorin_parse_index);
+                diag = build(fluent::codegen_ssa_thorin_parse_index);
                 diag.set_arg("section", section);
                 diag
             }
             thorin::Error::UnitNotInIndex(unit) => {
-                diag = dcx.struct_err(fluent::codegen_ssa_thorin_unit_not_in_index);
+                diag = build(fluent::codegen_ssa_thorin_unit_not_in_index);
                 diag.set_arg("unit", format!("0x{unit:08x}"));
                 diag
             }
             thorin::Error::RowNotInIndex(_, row) => {
-                diag = dcx.struct_err(fluent::codegen_ssa_thorin_row_not_in_index);
+                diag = build(fluent::codegen_ssa_thorin_row_not_in_index);
                 diag.set_arg("row", row);
                 diag
             }
             thorin::Error::SectionNotInRow => {
-                diag = dcx.struct_err(fluent::codegen_ssa_thorin_section_not_in_row);
+                diag = build(fluent::codegen_ssa_thorin_section_not_in_row);
                 diag
             }
             thorin::Error::EmptyUnit(unit) => {
-                diag = dcx.struct_err(fluent::codegen_ssa_thorin_empty_unit);
+                diag = build(fluent::codegen_ssa_thorin_empty_unit);
                 diag.set_arg("unit", format!("0x{unit:08x}"));
                 diag
             }
             thorin::Error::MultipleDebugInfoSection => {
-                diag = dcx.struct_err(fluent::codegen_ssa_thorin_multiple_debug_info_section);
+                diag = build(fluent::codegen_ssa_thorin_multiple_debug_info_section);
                 diag
             }
             thorin::Error::MultipleDebugTypesSection => {
-                diag = dcx.struct_err(fluent::codegen_ssa_thorin_multiple_debug_types_section);
+                diag = build(fluent::codegen_ssa_thorin_multiple_debug_types_section);
                 diag
             }
             thorin::Error::NotSplitUnit => {
-                diag = dcx.struct_err(fluent::codegen_ssa_thorin_not_split_unit);
+                diag = build(fluent::codegen_ssa_thorin_not_split_unit);
                 diag
             }
             thorin::Error::DuplicateUnit(unit) => {
-                diag = dcx.struct_err(fluent::codegen_ssa_thorin_duplicate_unit);
+                diag = build(fluent::codegen_ssa_thorin_duplicate_unit);
                 diag.set_arg("unit", format!("0x{unit:08x}"));
                 diag
             }
             thorin::Error::MissingReferencedUnit(unit) => {
-                diag = dcx.struct_err(fluent::codegen_ssa_thorin_missing_referenced_unit);
+                diag = build(fluent::codegen_ssa_thorin_missing_referenced_unit);
                 diag.set_arg("unit", format!("0x{unit:08x}"));
                 diag
             }
             thorin::Error::NoOutputObjectCreated => {
-                diag = dcx.struct_err(fluent::codegen_ssa_thorin_not_output_object_created);
+                diag = build(fluent::codegen_ssa_thorin_not_output_object_created);
                 diag
             }
             thorin::Error::MixedInputEncodings => {
-                diag = dcx.struct_err(fluent::codegen_ssa_thorin_mixed_input_encodings);
+                diag = build(fluent::codegen_ssa_thorin_mixed_input_encodings);
                 diag
             }
             thorin::Error::Io(e) => {
-                diag = dcx.struct_err(fluent::codegen_ssa_thorin_io);
+                diag = build(fluent::codegen_ssa_thorin_io);
                 diag.set_arg("error", format!("{e}"));
                 diag
             }
             thorin::Error::ObjectRead(e) => {
-                diag = dcx.struct_err(fluent::codegen_ssa_thorin_object_read);
+                diag = build(fluent::codegen_ssa_thorin_object_read);
                 diag.set_arg("error", format!("{e}"));
                 diag
             }
             thorin::Error::ObjectWrite(e) => {
-                diag = dcx.struct_err(fluent::codegen_ssa_thorin_object_write);
+                diag = build(fluent::codegen_ssa_thorin_object_write);
                 diag.set_arg("error", format!("{e}"));
                 diag
             }
             thorin::Error::GimliRead(e) => {
-                diag = dcx.struct_err(fluent::codegen_ssa_thorin_gimli_read);
+                diag = build(fluent::codegen_ssa_thorin_gimli_read);
                 diag.set_arg("error", format!("{e}"));
                 diag
             }
             thorin::Error::GimliWrite(e) => {
-                diag = dcx.struct_err(fluent::codegen_ssa_thorin_gimli_write);
+                diag = build(fluent::codegen_ssa_thorin_gimli_write);
                 diag.set_arg("error", format!("{e}"));
                 diag
             }
@@ -410,9 +411,9 @@ pub struct LinkingFailed<'a> {
     pub escaped_output: String,
 }
 
-impl IntoDiagnostic<'_> for LinkingFailed<'_> {
-    fn into_diagnostic(self, dcx: &DiagCtxt) -> DiagnosticBuilder<'_, ErrorGuaranteed> {
-        let mut diag = dcx.struct_err(fluent::codegen_ssa_linking_failed);
+impl<G: EmissionGuarantee> IntoDiagnostic<'_, G> for LinkingFailed<'_> {
+    fn into_diagnostic(self, dcx: &DiagCtxt, level: Level) -> DiagnosticBuilder<'_, G> {
+        let mut diag = DiagnosticBuilder::new(dcx, level, fluent::codegen_ssa_linking_failed);
         diag.set_arg("linker_path", format!("{}", self.linker_path.display()));
         diag.set_arg("exit_status", format!("{}", self.exit_status));
 

compiler/rustc_const_eval/src/const_eval/error.rs

@@ -6,7 +6,7 @@ use rustc_middle::mir::AssertKind;
 use rustc_middle::query::TyCtxtAt;
 use rustc_middle::ty::TyCtxt;
 use rustc_middle::ty::{layout::LayoutError, ConstInt};
-use rustc_span::{ErrorGuaranteed, Span, Symbol, DUMMY_SP};
+use rustc_span::{Span, Symbol, DUMMY_SP};
 
 use super::{CompileTimeInterpreter, InterpCx};
 use crate::errors::{self, FrameNote, ReportErrorExt};
@@ -133,7 +133,7 @@ pub(super) fn report<'tcx, C, F, E>(
 where
     C: FnOnce() -> (Span, Vec<FrameNote>),
     F: FnOnce(Span, Vec<FrameNote>) -> E,
-    E: IntoDiagnostic<'tcx, ErrorGuaranteed>,
+    E: IntoDiagnostic<'tcx>,
 {
     // Special handling for certain errors
     match error {

compiler/rustc_const_eval/src/errors.rs

@@ -1,6 +1,6 @@
 use rustc_errors::{
     DiagCtxt, DiagnosticArgValue, DiagnosticBuilder, DiagnosticMessage, EmissionGuarantee,
-    IntoDiagnostic,
+    IntoDiagnostic, Level,
 };
 use rustc_hir::ConstContext;
 use rustc_macros::{Diagnostic, LintDiagnostic, Subdiagnostic};
@@ -875,7 +875,10 @@ impl<'tcx> ReportErrorExt for InvalidProgramInfo<'tcx> {
             | InvalidProgramInfo::AlreadyReported(_)
             | InvalidProgramInfo::ConstPropNonsense => {}
             InvalidProgramInfo::Layout(e) => {
-                let diag: DiagnosticBuilder<'_, ()> = e.into_diagnostic().into_diagnostic(dcx);
+                // The level doesn't matter, `diag` is consumed without it being used.
+                let dummy_level = Level::Bug;
+                let diag: DiagnosticBuilder<'_, ()> =
+                    e.into_diagnostic().into_diagnostic(dcx, dummy_level);
                 for (name, val) in diag.args() {
                     builder.set_arg(name.clone(), val.clone());
                 }

compiler/rustc_const_eval/src/interpret/memory.rs

@@ -165,6 +165,8 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         // We need to handle `extern static`.
         match self.tcx.try_get_global_alloc(alloc_id) {
             Some(GlobalAlloc::Static(def_id)) if self.tcx.is_thread_local_static(def_id) => {
+                // Thread-local statics do not have a constant address. They *must* be accessed via
+                // `ThreadLocalRef`; we can never have a pointer to them as a regular constant value.
                 bug!("global memory cannot point to thread-local static")
             }
             Some(GlobalAlloc::Static(def_id)) if self.tcx.is_foreign_item(def_id) => {
@@ -539,6 +541,8 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
             None => throw_ub!(PointerUseAfterFree(id, CheckInAllocMsg::MemoryAccessTest)),
             Some(GlobalAlloc::Static(def_id)) => {
                 assert!(self.tcx.is_static(def_id));
+                // Thread-local statics do not have a constant address. They *must* be accessed via
+                // `ThreadLocalRef`; we can never have a pointer to them as a regular constant value.
                 assert!(!self.tcx.is_thread_local_static(def_id));
                 // Notice that every static has two `AllocId` that will resolve to the same
                 // thing here: one maps to `GlobalAlloc::Static`, this is the "lazy" ID,
@@ -740,6 +744,8 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         match self.tcx.try_get_global_alloc(id) {
             Some(GlobalAlloc::Static(def_id)) => {
                 assert!(self.tcx.is_static(def_id));
+                // Thread-local statics do not have a constant address. They *must* be accessed via
+                // `ThreadLocalRef`; we can never have a pointer to them as a regular constant value.
                 assert!(!self.tcx.is_thread_local_static(def_id));
                 // Use size and align of the type.
                 let ty = self

compiler/rustc_const_eval/src/transform/check_consts/check.rs

@@ -5,17 +5,15 @@ use rustc_hir as hir;
 use rustc_hir::def_id::DefId;
 use rustc_index::bit_set::BitSet;
 use rustc_infer::infer::TyCtxtInferExt;
-use rustc_infer::traits::{ImplSource, Obligation, ObligationCause};
+use rustc_infer::traits::ObligationCause;
 use rustc_middle::mir::visit::{MutatingUseContext, NonMutatingUseContext, PlaceContext, Visitor};
 use rustc_middle::mir::*;
-use rustc_middle::traits::BuiltinImplSource;
-use rustc_middle::ty::GenericArgs;
-use rustc_middle::ty::{self, adjustment::PointerCoercion, Instance, InstanceDef, Ty, TyCtxt};
-use rustc_middle::ty::{TraitRef, TypeVisitableExt};
+use rustc_middle::ty::{self, adjustment::PointerCoercion, Ty, TyCtxt};
+use rustc_middle::ty::{Instance, InstanceDef, TypeVisitableExt};
 use rustc_mir_dataflow::Analysis;
 use rustc_span::{sym, Span, Symbol};
 use rustc_trait_selection::traits::error_reporting::TypeErrCtxtExt as _;
-use rustc_trait_selection::traits::{self, ObligationCauseCode, ObligationCtxt, SelectionContext};
+use rustc_trait_selection::traits::{self, ObligationCauseCode, ObligationCtxt};
 use rustc_type_ir::visit::{TypeSuperVisitable, TypeVisitor};
 
 use std::mem;
@@ -464,8 +462,12 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
 
             Rvalue::Aggregate(kind, ..) => {
                 if let AggregateKind::Coroutine(def_id, ..) = kind.as_ref()
-                    && let Some(coroutine_kind @ hir::CoroutineKind::Async(..)) =
-                        self.tcx.coroutine_kind(def_id)
+                    && let Some(
+                        coroutine_kind @ hir::CoroutineKind::Desugared(
+                            hir::CoroutineDesugaring::Async,
+                            _,
+                        ),
+                    ) = self.tcx.coroutine_kind(def_id)
                 {
                     self.check_op(ops::Coroutine(coroutine_kind));
                 }
@@ -752,143 +754,43 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
                     infcx.err_ctxt().report_fulfillment_errors(errors);
                 }
 
+                let mut is_trait = false;
                 // Attempting to call a trait method?
-                // FIXME(effects) do we need this?
-                if let Some(trait_id) = tcx.trait_of_item(callee) {
+                if tcx.trait_of_item(callee).is_some() {
                     trace!("attempting to call a trait method");
-                    if !self.tcx.features().const_trait_impl {
+                    // trait method calls are only permitted when `effects` is enabled.
+                    // we don't error, since that is handled by typeck. We try to resolve
+                    // the trait into the concrete method, and uses that for const stability
+                    // checks.
+                    // FIXME(effects) we might consider moving const stability checks to typeck as well.
+                    if tcx.features().effects {
+                        is_trait = true;
+
+                        if let Ok(Some(instance)) =
+                            Instance::resolve(tcx, param_env, callee, fn_args)
+                            && let InstanceDef::Item(def) = instance.def
+                        {
+                            // Resolve a trait method call to its concrete implementation, which may be in a
+                            // `const` trait impl. This is only used for the const stability check below, since
+                            // we want to look at the concrete impl's stability.
+                            fn_args = instance.args;
+                            callee = def;
+                        }
+                    } else {
                         self.check_op(ops::FnCallNonConst {
                             caller,
                             callee,
                             args: fn_args,
                             span: *fn_span,
                             call_source: *call_source,
-                            feature: Some(sym::const_trait_impl),
+                            feature: Some(if tcx.features().const_trait_impl {
+                                sym::effects
+                            } else {
+                                sym::const_trait_impl
+                            }),
                         });
                         return;
                     }
-
-                    let trait_ref = TraitRef::from_method(tcx, trait_id, fn_args);
-                    let obligation =
-                        Obligation::new(tcx, ObligationCause::dummy(), param_env, trait_ref);
-
-                    let implsrc = {
-                        let infcx = tcx.infer_ctxt().build();
-                        let mut selcx = SelectionContext::new(&infcx);
-                        selcx.select(&obligation)
-                    };
-
-                    match implsrc {
-                        Ok(Some(ImplSource::Param(_))) if tcx.features().effects => {
-                            debug!(
-                                "const_trait_impl: provided {:?} via where-clause in {:?}",
-                                trait_ref, param_env
-                            );
-                            return;
-                        }
-                        // Closure: Fn{Once|Mut}
-                        Ok(Some(ImplSource::Builtin(BuiltinImplSource::Misc, _)))
-                            if trait_ref.self_ty().is_closure()
-                                && tcx.fn_trait_kind_from_def_id(trait_id).is_some() =>
-                        {
-                            let ty::Closure(closure_def_id, fn_args) = *trait_ref.self_ty().kind()
-                            else {
-                                unreachable!()
-                            };
-                            if !tcx.is_const_fn_raw(closure_def_id) {
-                                self.check_op(ops::FnCallNonConst {
-                                    caller,
-                                    callee,
-                                    args: fn_args,
-                                    span: *fn_span,
-                                    call_source: *call_source,
-                                    feature: None,
-                                });
-
-                                return;
-                            }
-                        }
-                        Ok(Some(ImplSource::UserDefined(data))) => {
-                            let callee_name = tcx.item_name(callee);
-
-                            if let hir::Constness::NotConst = tcx.constness(data.impl_def_id) {
-                                self.check_op(ops::FnCallNonConst {
-                                    caller,
-                                    callee,
-                                    args: fn_args,
-                                    span: *fn_span,
-                                    call_source: *call_source,
-                                    feature: None,
-                                });
-                                return;
-                            }
-
-                            if let Some(&did) = tcx
-                                .associated_item_def_ids(data.impl_def_id)
-                                .iter()
-                                .find(|did| tcx.item_name(**did) == callee_name)
-                            {
-                                // using internal args is ok here, since this is only
-                                // used for the `resolve` call below
-                                fn_args = GenericArgs::identity_for_item(tcx, did);
-                                callee = did;
-                            }
-                        }
-                        _ if !tcx.is_const_fn_raw(callee) => {
-                            // At this point, it is only legal when the caller is in a trait
-                            // marked with #[const_trait], and the callee is in the same trait.
-                            let mut nonconst_call_permission = false;
-                            if let Some(callee_trait) = tcx.trait_of_item(callee)
-                                && tcx.has_attr(callee_trait, sym::const_trait)
-                                && Some(callee_trait) == tcx.trait_of_item(caller.to_def_id())
-                                // Can only call methods when it's `<Self as TheTrait>::f`.
-                                && tcx.types.self_param == fn_args.type_at(0)
-                            {
-                                nonconst_call_permission = true;
-                            }
-
-                            if !nonconst_call_permission {
-                                let obligation = Obligation::new(
-                                    tcx,
-                                    ObligationCause::dummy_with_span(*fn_span),
-                                    param_env,
-                                    trait_ref,
-                                );
-
-                                // improve diagnostics by showing what failed. Our requirements are stricter this time
-                                // as we are going to error again anyways.
-                                let infcx = tcx.infer_ctxt().build();
-                                if let Err(e) = implsrc {
-                                    infcx.err_ctxt().report_selection_error(
-                                        obligation.clone(),
-                                        &obligation,
-                                        &e,
-                                    );
-                                }
-
-                                self.check_op(ops::FnCallNonConst {
-                                    caller,
-                                    callee,
-                                    args: fn_args,
-                                    span: *fn_span,
-                                    call_source: *call_source,
-                                    feature: None,
-                                });
-                                return;
-                            }
-                        }
-                        _ => {}
-                    }
-
-                    // Resolve a trait method call to its concrete implementation, which may be in a
-                    // `const` trait impl.
-                    let instance = Instance::resolve(tcx, param_env, callee, fn_args);
-                    debug!("Resolving ({:?}) -> {:?}", callee, instance);
-                    if let Ok(Some(func)) = instance {
-                        if let InstanceDef::Item(def) = func.def {
-                            callee = def;
-                        }
-                    }
                 }
 
                 // At this point, we are calling a function, `callee`, whose `DefId` is known...
@@ -921,21 +823,16 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
                     return;
                 }
 
-                if !tcx.is_const_fn_raw(callee) {
-                    if !tcx.is_const_default_method(callee) {
-                        // To get to here we must have already found a const impl for the
-                        // trait, but for it to still be non-const can be that the impl is
-                        // using default method bodies.
-                        self.check_op(ops::FnCallNonConst {
-                            caller,
-                            callee,
-                            args: fn_args,
-                            span: *fn_span,
-                            call_source: *call_source,
-                            feature: None,
-                        });
-                        return;
-                    }
+                if !tcx.is_const_fn_raw(callee) && !is_trait {
+                    self.check_op(ops::FnCallNonConst {
+                        caller,
+                        callee,
+                        args: fn_args,
+                        span: *fn_span,
+                        call_source: *call_source,
+                        feature: None,
+                    });
+                    return;
                 }
 
                 // If the `const fn` we are trying to call is not const-stable, ensure that we have

compiler/rustc_const_eval/src/transform/check_consts/ops.rs

@@ -2,7 +2,7 @@
 
 use hir::def_id::LocalDefId;
 use hir::{ConstContext, LangItem};
-use rustc_errors::{error_code, DiagnosticBuilder, ErrorGuaranteed};
+use rustc_errors::{error_code, DiagnosticBuilder};
 use rustc_hir as hir;
 use rustc_hir::def_id::DefId;
 use rustc_infer::infer::TyCtxtInferExt;
@@ -48,11 +48,7 @@ pub trait NonConstOp<'tcx>: std::fmt::Debug {
         DiagnosticImportance::Primary
     }
 
-    fn build_error(
-        &self,
-        ccx: &ConstCx<'_, 'tcx>,
-        span: Span,
-    ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed>;
+    fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> DiagnosticBuilder<'tcx>;
 }
 
 #[derive(Debug)]
@@ -66,11 +62,7 @@ impl<'tcx> NonConstOp<'tcx> for FloatingPointOp {
         }
     }
 
-    fn build_error(
-        &self,
-        ccx: &ConstCx<'_, 'tcx>,
-        span: Span,
-    ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+    fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> DiagnosticBuilder<'tcx> {
         feature_err(
             &ccx.tcx.sess.parse_sess,
             sym::const_fn_floating_point_arithmetic,
@@ -84,11 +76,7 @@ impl<'tcx> NonConstOp<'tcx> for FloatingPointOp {
 #[derive(Debug)]
 pub struct FnCallIndirect;
 impl<'tcx> NonConstOp<'tcx> for FnCallIndirect {
-    fn build_error(
-        &self,
-        ccx: &ConstCx<'_, 'tcx>,
-        span: Span,
-    ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+    fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> DiagnosticBuilder<'tcx> {
         ccx.tcx.sess.create_err(errors::UnallowedFnPointerCall { span, kind: ccx.const_kind() })
     }
 }
@@ -105,11 +93,7 @@ pub struct FnCallNonConst<'tcx> {
 }
 
 impl<'tcx> NonConstOp<'tcx> for FnCallNonConst<'tcx> {
-    fn build_error(
-        &self,
-        ccx: &ConstCx<'_, 'tcx>,
-        _: Span,
-    ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+    fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, _: Span) -> DiagnosticBuilder<'tcx> {
         let FnCallNonConst { caller, callee, args, span, call_source, feature } = *self;
         let ConstCx { tcx, param_env, .. } = *ccx;
 
@@ -331,11 +315,7 @@ impl<'tcx> NonConstOp<'tcx> for FnCallNonConst<'tcx> {
 pub struct FnCallUnstable(pub DefId, pub Option<Symbol>);
 
 impl<'tcx> NonConstOp<'tcx> for FnCallUnstable {
-    fn build_error(
-        &self,
-        ccx: &ConstCx<'_, 'tcx>,
-        span: Span,
-    ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+    fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> DiagnosticBuilder<'tcx> {
         let FnCallUnstable(def_id, feature) = *self;
 
         let mut err = ccx
@@ -359,20 +339,24 @@ impl<'tcx> NonConstOp<'tcx> for FnCallUnstable {
 pub struct Coroutine(pub hir::CoroutineKind);
 impl<'tcx> NonConstOp<'tcx> for Coroutine {
     fn status_in_item(&self, _: &ConstCx<'_, 'tcx>) -> Status {
-        if let hir::CoroutineKind::Async(hir::CoroutineSource::Block) = self.0 {
+        if let hir::CoroutineKind::Desugared(
+            hir::CoroutineDesugaring::Async,
+            hir::CoroutineSource::Block,
+        ) = self.0
+        {
             Status::Unstable(sym::const_async_blocks)
         } else {
             Status::Forbidden
         }
     }
 
-    fn build_error(
-        &self,
-        ccx: &ConstCx<'_, 'tcx>,
-        span: Span,
-    ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+    fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> DiagnosticBuilder<'tcx> {
         let msg = format!("{:#}s are not allowed in {}s", self.0, ccx.const_kind());
-        if let hir::CoroutineKind::Async(hir::CoroutineSource::Block) = self.0 {
+        if let hir::CoroutineKind::Desugared(
+            hir::CoroutineDesugaring::Async,
+            hir::CoroutineSource::Block,
+        ) = self.0
+        {
             ccx.tcx.sess.create_feature_err(
                 errors::UnallowedOpInConstContext { span, msg },
                 sym::const_async_blocks,
@@ -386,11 +370,7 @@ impl<'tcx> NonConstOp<'tcx> for Coroutine {
 #[derive(Debug)]
 pub struct HeapAllocation;
 impl<'tcx> NonConstOp<'tcx> for HeapAllocation {
-    fn build_error(
-        &self,
-        ccx: &ConstCx<'_, 'tcx>,
-        span: Span,
-    ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+    fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> DiagnosticBuilder<'tcx> {
         ccx.tcx.sess.create_err(errors::UnallowedHeapAllocations {
             span,
             kind: ccx.const_kind(),
@@ -402,11 +382,7 @@ impl<'tcx> NonConstOp<'tcx> for HeapAllocation {
 #[derive(Debug)]
 pub struct InlineAsm;
 impl<'tcx> NonConstOp<'tcx> for InlineAsm {
-    fn build_error(
-        &self,
-        ccx: &ConstCx<'_, 'tcx>,
-        span: Span,
-    ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+    fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> DiagnosticBuilder<'tcx> {
         ccx.tcx.sess.create_err(errors::UnallowedInlineAsm { span, kind: ccx.const_kind() })
     }
 }
@@ -417,11 +393,7 @@ pub struct LiveDrop<'tcx> {
     pub dropped_ty: Ty<'tcx>,
 }
 impl<'tcx> NonConstOp<'tcx> for LiveDrop<'tcx> {
-    fn build_error(
-        &self,
-        ccx: &ConstCx<'_, 'tcx>,
-        span: Span,
-    ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+    fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> DiagnosticBuilder<'tcx> {
         ccx.tcx.sess.create_err(errors::LiveDrop {
             span,
             dropped_ty: self.dropped_ty,
@@ -444,11 +416,7 @@ impl<'tcx> NonConstOp<'tcx> for TransientCellBorrow {
         // not additionally emit a feature gate error if activating the feature gate won't work.
         DiagnosticImportance::Secondary
     }
-    fn build_error(
-        &self,
-        ccx: &ConstCx<'_, 'tcx>,
-        span: Span,
-    ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+    fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> DiagnosticBuilder<'tcx> {
         ccx.tcx
             .sess
             .create_feature_err(errors::InteriorMutabilityBorrow { span }, sym::const_refs_to_cell)
@@ -461,11 +429,7 @@ impl<'tcx> NonConstOp<'tcx> for TransientCellBorrow {
 /// it in the future for static items.
 pub struct CellBorrow;
 impl<'tcx> NonConstOp<'tcx> for CellBorrow {
-    fn build_error(
-        &self,
-        ccx: &ConstCx<'_, 'tcx>,
-        span: Span,
-    ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+    fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> DiagnosticBuilder<'tcx> {
         // FIXME: Maybe a more elegant solution to this if else case
         if let hir::ConstContext::Static(_) = ccx.const_kind() {
             ccx.tcx.sess.create_err(errors::InteriorMutableDataRefer {
@@ -502,11 +466,7 @@ impl<'tcx> NonConstOp<'tcx> for MutBorrow {
         DiagnosticImportance::Secondary
     }
 
-    fn build_error(
-        &self,
-        ccx: &ConstCx<'_, 'tcx>,
-        span: Span,
-    ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+    fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> DiagnosticBuilder<'tcx> {
         match self.0 {
             hir::BorrowKind::Raw => ccx.tcx.sess.create_err(errors::UnallowedMutableRefsRaw {
                 span,
@@ -530,11 +490,7 @@ impl<'tcx> NonConstOp<'tcx> for TransientMutBorrow {
         Status::Unstable(sym::const_mut_refs)
     }
 
-    fn build_error(
-        &self,
-        ccx: &ConstCx<'_, 'tcx>,
-        span: Span,
-    ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+    fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> DiagnosticBuilder<'tcx> {
         let kind = ccx.const_kind();
         match self.0 {
             hir::BorrowKind::Raw => ccx.tcx.sess.create_feature_err(
@@ -561,11 +517,7 @@ impl<'tcx> NonConstOp<'tcx> for MutDeref {
         DiagnosticImportance::Secondary
     }
 
-    fn build_error(
-        &self,
-        ccx: &ConstCx<'_, 'tcx>,
-        span: Span,
-    ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+    fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> DiagnosticBuilder<'tcx> {
         ccx.tcx.sess.create_feature_err(
             errors::MutDerefErr { span, kind: ccx.const_kind() },
             sym::const_mut_refs,
@@ -577,11 +529,7 @@ impl<'tcx> NonConstOp<'tcx> for MutDeref {
 #[derive(Debug)]
 pub struct PanicNonStr;
 impl<'tcx> NonConstOp<'tcx> for PanicNonStr {
-    fn build_error(
-        &self,
-        ccx: &ConstCx<'_, 'tcx>,
-        span: Span,
-    ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+    fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> DiagnosticBuilder<'tcx> {
         ccx.tcx.sess.create_err(errors::PanicNonStrErr { span })
     }
 }
@@ -592,11 +540,7 @@ impl<'tcx> NonConstOp<'tcx> for PanicNonStr {
 #[derive(Debug)]
 pub struct RawPtrComparison;
 impl<'tcx> NonConstOp<'tcx> for RawPtrComparison {
-    fn build_error(
-        &self,
-        ccx: &ConstCx<'_, 'tcx>,
-        span: Span,
-    ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+    fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> DiagnosticBuilder<'tcx> {
         // FIXME(const_trait_impl): revert to span_bug?
         ccx.tcx.sess.create_err(errors::RawPtrComparisonErr { span })
     }
@@ -609,11 +553,7 @@ impl<'tcx> NonConstOp<'tcx> for RawMutPtrDeref {
         Status::Unstable(sym::const_mut_refs)
     }
 
-    fn build_error(
-        &self,
-        ccx: &ConstCx<'_, 'tcx>,
-        span: Span,
-    ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+    fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> DiagnosticBuilder<'tcx> {
         feature_err(
             &ccx.tcx.sess.parse_sess,
             sym::const_mut_refs,
@@ -629,11 +569,7 @@ impl<'tcx> NonConstOp<'tcx> for RawMutPtrDeref {
 #[derive(Debug)]
 pub struct RawPtrToIntCast;
 impl<'tcx> NonConstOp<'tcx> for RawPtrToIntCast {
-    fn build_error(
-        &self,
-        ccx: &ConstCx<'_, 'tcx>,
-        span: Span,
-    ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+    fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> DiagnosticBuilder<'tcx> {
         ccx.tcx.sess.create_err(errors::RawPtrToIntErr { span })
     }
 }
@@ -650,11 +586,7 @@ impl<'tcx> NonConstOp<'tcx> for StaticAccess {
         }
     }
 
-    fn build_error(
-        &self,
-        ccx: &ConstCx<'_, 'tcx>,
-        span: Span,
-    ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+    fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> DiagnosticBuilder<'tcx> {
         ccx.tcx.sess.create_err(errors::StaticAccessErr {
             span,
             kind: ccx.const_kind(),
@@ -667,11 +599,7 @@ impl<'tcx> NonConstOp<'tcx> for StaticAccess {
 #[derive(Debug)]
 pub struct ThreadLocalAccess;
 impl<'tcx> NonConstOp<'tcx> for ThreadLocalAccess {
-    fn build_error(
-        &self,
-        ccx: &ConstCx<'_, 'tcx>,
-        span: Span,
-    ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+    fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> DiagnosticBuilder<'tcx> {
         ccx.tcx.sess.create_err(errors::NonConstOpErr { span })
     }
 }
@@ -696,11 +624,7 @@ pub mod ty {
             }
         }
 
-        fn build_error(
-            &self,
-            ccx: &ConstCx<'_, 'tcx>,
-            span: Span,
-        ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+        fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> DiagnosticBuilder<'tcx> {
             feature_err(
                 &ccx.tcx.sess.parse_sess,
                 sym::const_mut_refs,

compiler/rustc_const_eval/src/transform/validate.rs

@@ -8,9 +8,6 @@ use rustc_middle::mir::interpret::Scalar;
 use rustc_middle::mir::visit::{NonUseContext, PlaceContext, Visitor};
 use rustc_middle::mir::*;
 use rustc_middle::ty::{self, InstanceDef, ParamEnv, Ty, TyCtxt, TypeVisitableExt, Variance};
-use rustc_mir_dataflow::impls::MaybeStorageLive;
-use rustc_mir_dataflow::storage::always_storage_live_locals;
-use rustc_mir_dataflow::{Analysis, ResultsCursor};
 use rustc_target::abi::{Size, FIRST_VARIANT};
 use rustc_target::spec::abi::Abi;
 
@@ -51,12 +48,6 @@ impl<'tcx> MirPass<'tcx> for Validator {
             Reveal::All => tcx.param_env_reveal_all_normalized(def_id),
         };
 
-        let always_live_locals = always_storage_live_locals(body);
-        let storage_liveness = MaybeStorageLive::new(std::borrow::Cow::Owned(always_live_locals))
-            .into_engine(tcx, body)
-            .iterate_to_fixpoint()
-            .into_results_cursor(body);
-
         let can_unwind = if mir_phase <= MirPhase::Runtime(RuntimePhase::Initial) {
             // In this case `AbortUnwindingCalls` haven't yet been executed.
             true
@@ -83,7 +74,6 @@ impl<'tcx> MirPass<'tcx> for Validator {
             mir_phase,
             unwind_edge_count: 0,
             reachable_blocks: traversal::reachable_as_bitset(body),
-            storage_liveness,
             place_cache: FxHashSet::default(),
             value_cache: FxHashSet::default(),
             can_unwind,
@@ -116,7 +106,6 @@ struct CfgChecker<'a, 'tcx> {
     mir_phase: MirPhase,
     unwind_edge_count: usize,
     reachable_blocks: BitSet<BasicBlock>,
-    storage_liveness: ResultsCursor<'a, 'tcx, MaybeStorageLive<'static>>,
     place_cache: FxHashSet<PlaceRef<'tcx>>,
     value_cache: FxHashSet<u128>,
     // If `false`, then the MIR must not contain `UnwindAction::Continue` or
@@ -294,28 +283,13 @@ impl<'a, 'tcx> CfgChecker<'a, 'tcx> {
 }
 
 impl<'a, 'tcx> Visitor<'tcx> for CfgChecker<'a, 'tcx> {
-    fn visit_local(&mut self, local: Local, context: PlaceContext, location: Location) {
+    fn visit_local(&mut self, local: Local, _context: PlaceContext, location: Location) {
         if self.body.local_decls.get(local).is_none() {
             self.fail(
                 location,
                 format!("local {local:?} has no corresponding declaration in `body.local_decls`"),
             );
         }
-
-        if self.reachable_blocks.contains(location.block) && context.is_use() {
-            // We check that the local is live whenever it is used. Technically, violating this
-            // restriction is only UB and not actually indicative of not well-formed MIR. This means
-            // that an optimization which turns MIR that already has UB into MIR that fails this
-            // check is not necessarily wrong. However, we have no such optimizations at the moment,
-            // and so we include this check anyway to help us catch bugs. If you happen to write an
-            // optimization that might cause this to incorrectly fire, feel free to remove this
-            // check.
-            self.storage_liveness.seek_after_primary_effect(location);
-            let locals_with_storage = self.storage_liveness.get();
-            if !locals_with_storage.contains(local) {
-                self.fail(location, format!("use of local {local:?}, which has no storage here"));
-            }
-        }
     }
 
     fn visit_statement(&mut self, statement: &Statement<'tcx>, location: Location) {
@@ -367,26 +341,8 @@ impl<'a, 'tcx> Visitor<'tcx> for CfgChecker<'a, 'tcx> {
                     self.fail(location, format!("explicit `{kind:?}` is forbidden"));
                 }
             }
-            StatementKind::StorageLive(local) => {
-                // We check that the local is not live when entering a `StorageLive` for it.
-                // Technically, violating this restriction is only UB and not actually indicative
-                // of not well-formed MIR. This means that an optimization which turns MIR that
-                // already has UB into MIR that fails this check is not necessarily wrong. However,
-                // we have no such optimizations at the moment, and so we include this check anyway
-                // to help us catch bugs. If you happen to write an optimization that might cause
-                // this to incorrectly fire, feel free to remove this check.
-                if self.reachable_blocks.contains(location.block) {
-                    self.storage_liveness.seek_before_primary_effect(location);
-                    let locals_with_storage = self.storage_liveness.get();
-                    if locals_with_storage.contains(*local) {
-                        self.fail(
-                            location,
-                            format!("StorageLive({local:?}) which already has storage here"),
-                        );
-                    }
-                }
-            }
-            StatementKind::StorageDead(_)
+            StatementKind::StorageLive(_)
+            | StatementKind::StorageDead(_)
             | StatementKind::Intrinsic(_)
             | StatementKind::Coverage(_)
             | StatementKind::ConstEvalCounter

compiler/rustc_data_structures/src/tagged_ptr/impl_tag.rs

@@ -81,150 +81,6 @@
 ///     E::A,
 /// }
 /// ```
-#[cfg(bootstrap)]
-#[macro_export]
-macro_rules! impl_tag {
-    (
-        impl Tag for $Self:ty;
-        $(
-            $($path:ident)::* $( { $( $fields:tt )* })?,
-        )*
-    ) => {
-        // Safety:
-        // `bits_for_tags` is called on the same `${index()}`-es as
-        // `into_usize` returns, thus `BITS` constant is correct.
-        unsafe impl $crate::tagged_ptr::Tag for $Self {
-            const BITS: u32 = $crate::tagged_ptr::bits_for_tags(&[
-                $(
-                    ${index()},
-                    $( ${ignore(path)} )*
-                )*
-            ]);
-
-            #[inline]
-            fn into_usize(self) -> usize {
-                // This forbids use of repeating patterns (`Enum::V`&`Enum::V`, etc)
-                // (or at least it should, see <https://github.com/rust-lang/rust/issues/110613>)
-                #[forbid(unreachable_patterns)]
-                match self {
-                    // `match` is doing heavy lifting here, by requiring exhaustiveness
-                    $(
-                        $($path)::* $( { $( $fields )* } )? => ${index()},
-                    )*
-                }
-            }
-
-            #[inline]
-            unsafe fn from_usize(tag: usize) -> Self {
-                match tag {
-                    $(
-                        ${index()} => $($path)::* $( { $( $fields )* } )?,
-                    )*
-
-                    // Safety:
-                    // `into_usize` only returns `${index()}` of the same
-                    // repetition as we are filtering above, thus if this is
-                    // reached, the safety contract of this function was
-                    // already breached.
-                    _ => unsafe {
-                        debug_assert!(
-                            false,
-                            "invalid tag: {tag}\
-                             (this is a bug in the caller of `from_usize`)"
-                        );
-                        std::hint::unreachable_unchecked()
-                    },
-                }
-            }
-
-        }
-    };
-}
-
-/// Implements [`Tag`] for a given type.
-///
-/// You can use `impl_tag` on structs and enums.
-/// You need to specify the type and all its possible values,
-/// which can only be paths with optional fields.
-///
-/// [`Tag`]: crate::tagged_ptr::Tag
-///
-/// # Examples
-///
-/// Basic usage:
-///
-/// ```
-/// #![feature(macro_metavar_expr)]
-/// use rustc_data_structures::{impl_tag, tagged_ptr::Tag};
-///
-/// #[derive(Copy, Clone, PartialEq, Debug)]
-/// enum SomeTag {
-///     A,
-///     B,
-///     X { v: bool },
-///     Y(bool, bool),
-/// }
-///
-/// impl_tag! {
-///     // The type for which the `Tag` will be implemented
-///     impl Tag for SomeTag;
-///     // You need to specify all possible tag values:
-///     SomeTag::A, // 0
-///     SomeTag::B, // 1
-///     // For variants with fields, you need to specify the fields:
-///     SomeTag::X { v: true  }, // 2
-///     SomeTag::X { v: false }, // 3
-///     // For tuple variants use named syntax:
-///     SomeTag::Y { 0: true,  1: true  }, // 4
-///     SomeTag::Y { 0: false, 1: true  }, // 5
-///     SomeTag::Y { 0: true,  1: false }, // 6
-///     SomeTag::Y { 0: false, 1: false }, // 7
-/// }
-///
-/// // Tag values are assigned in order:
-/// assert_eq!(SomeTag::A.into_usize(), 0);
-/// assert_eq!(SomeTag::X { v: false }.into_usize(), 3);
-/// assert_eq!(SomeTag::Y(false, true).into_usize(), 5);
-///
-/// assert_eq!(unsafe { SomeTag::from_usize(1) }, SomeTag::B);
-/// assert_eq!(unsafe { SomeTag::from_usize(2) }, SomeTag::X { v: true });
-/// assert_eq!(unsafe { SomeTag::from_usize(7) }, SomeTag::Y(false, false));
-/// ```
-///
-/// Structs are supported:
-///
-/// ```
-/// #![feature(macro_metavar_expr)]
-/// # use rustc_data_structures::impl_tag;
-/// #[derive(Copy, Clone)]
-/// struct Flags { a: bool, b: bool }
-///
-/// impl_tag! {
-///     impl Tag for Flags;
-///     Flags { a: true,  b: true  },
-///     Flags { a: false, b: true  },
-///     Flags { a: true,  b: false },
-///     Flags { a: false, b: false },
-/// }
-/// ```
-///
-/// Not specifying all values results in a compile error:
-///
-/// ```compile_fail,E0004
-/// #![feature(macro_metavar_expr)]
-/// # use rustc_data_structures::impl_tag;
-/// #[derive(Copy, Clone)]
-/// enum E {
-///     A,
-///     B,
-/// }
-///
-/// impl_tag! {
-///     impl Tag for E;
-///     E::A,
-/// }
-/// ```
-#[cfg(not(bootstrap))]
 #[macro_export]
 macro_rules! impl_tag {
     (

compiler/rustc_driver_impl/src/args.rs

@@ -28,7 +28,7 @@ pub fn arg_expand_all(early_dcx: &EarlyDiagCtxt, at_args: &[String]) -> Vec<Stri
     for arg in at_args {
         match arg_expand(arg.clone()) {
             Ok(arg) => args.extend(arg),
-            Err(err) => early_dcx.early_error(format!("Failed to load argument file: {err}")),
+            Err(err) => early_dcx.early_fatal(format!("Failed to load argument file: {err}")),
         }
     }
     args

compiler/rustc_driver_impl/src/lib.rs

@@ -345,7 +345,7 @@ fn run_compiler(
         Ok(None) => match matches.free.len() {
             0 => false, // no input: we will exit early
             1 => panic!("make_input should have provided valid inputs"),
-            _ => default_early_dcx.early_error(format!(
+            _ => default_early_dcx.early_fatal(format!(
                 "multiple input filenames provided (first two filenames are `{}` and `{}`)",
                 matches.free[0], matches.free[1],
             )),
@@ -376,7 +376,7 @@ fn run_compiler(
         }
 
         if !has_input {
-            early_dcx.early_error("no input filename given"); // this is fatal
+            early_dcx.early_fatal("no input filename given"); // this is fatal
         }
 
         if !sess.opts.unstable_opts.ls.is_empty() {
@@ -505,9 +505,8 @@ fn make_input(
             if io::stdin().read_to_string(&mut src).is_err() {
                 // Immediately stop compilation if there was an issue reading
                 // the input (for example if the input stream is not UTF-8).
-                let reported = early_dcx.early_error_no_abort(
-                    "couldn't read from stdin, as it did not contain valid UTF-8",
-                );
+                let reported = early_dcx
+                    .early_err("couldn't read from stdin, as it did not contain valid UTF-8");
                 return Err(reported);
             }
             if let Ok(path) = env::var("UNSTABLE_RUSTDOC_TEST_PATH") {
@@ -567,7 +566,7 @@ fn handle_explain(early_dcx: &EarlyDiagCtxt, registry: Registry, code: &str, col
             }
         }
         Err(InvalidErrorCode) => {
-            early_dcx.early_error(format!("{code} is not a valid error code"));
+            early_dcx.early_fatal(format!("{code} is not a valid error code"));
         }
     }
 }
@@ -685,7 +684,7 @@ fn list_metadata(early_dcx: &EarlyDiagCtxt, sess: &Session, metadata_loader: &dy
             safe_println!("{}", String::from_utf8(v).unwrap());
         }
         Input::Str { .. } => {
-            early_dcx.early_error("cannot list metadata for stdin");
+            early_dcx.early_fatal("cannot list metadata for stdin");
         }
     }
 }
@@ -839,7 +838,7 @@ fn print_crate_info(
                     println_info!("deployment_target={}", format!("{major}.{minor}"))
                 } else {
                     early_dcx
-                        .early_error("only Apple targets currently support deployment version info")
+                        .early_fatal("only Apple targets currently support deployment version info")
                 }
             }
         }
@@ -1182,7 +1181,7 @@ pub fn handle_options(early_dcx: &EarlyDiagCtxt, args: &[String]) -> Option<geto
                 .map(|(flag, _)| format!("{e}. Did you mean `-{flag} {opt}`?")),
             _ => None,
         };
-        early_dcx.early_error(msg.unwrap_or_else(|| e.to_string()));
+        early_dcx.early_fatal(msg.unwrap_or_else(|| e.to_string()));
     });
 
     // For all options we just parsed, we check a few aspects:
@@ -1333,7 +1332,7 @@ pub fn install_ice_hook(
                 {
                     // the error code is already going to be reported when the panic unwinds up the stack
                     let early_dcx = EarlyDiagCtxt::new(ErrorOutputType::default());
-                    let _ = early_dcx.early_error_no_abort(msg.clone());
+                    let _ = early_dcx.early_err(msg.clone());
                     return;
                 }
             };
@@ -1481,7 +1480,7 @@ pub fn init_rustc_env_logger(early_dcx: &EarlyDiagCtxt) {
 /// the values directly rather than having to set an environment variable.
 pub fn init_logger(early_dcx: &EarlyDiagCtxt, cfg: rustc_log::LoggerConfig) {
     if let Err(error) = rustc_log::init_logger(cfg) {
-        early_dcx.early_error(error.to_string());
+        early_dcx.early_fatal(error.to_string());
     }
 }
 
@@ -1500,7 +1499,7 @@ pub fn main() -> ! {
             .enumerate()
             .map(|(i, arg)| {
                 arg.into_string().unwrap_or_else(|arg| {
-                    early_dcx.early_error(format!("argument {i} is not valid Unicode: {arg:?}"))
+                    early_dcx.early_fatal(format!("argument {i} is not valid Unicode: {arg:?}"))
                 })
             })
             .collect::<Vec<_>>();

compiler/rustc_error_codes/src/error_codes/E0640.md

@@ -1 +1,2 @@
 #### This error code is internal to the compiler and will not be emitted with normal Rust code.
+#### Note: this error code is no longer emitted by the compiler.

compiler/rustc_errors/src/annotate_snippet_emitter_writer.rs

@@ -60,7 +60,7 @@ impl Emitter for AnnotateSnippetEmitterWriter {
 
         self.emit_messages_default(
             &diag.level,
-            &diag.message,
+            &diag.messages,
             &fluent_args,
             &diag.code,
             &primary_span,

compiler/rustc_errors/src/diagnostic.rs

@@ -103,7 +103,7 @@ pub struct Diagnostic {
     // outside of what methods in this crate themselves allow.
     pub(crate) level: Level,
 
-    pub message: Vec<(DiagnosticMessage, Style)>,
+    pub messages: Vec<(DiagnosticMessage, Style)>,
     pub code: Option<DiagnosticId>,
     pub span: MultiSpan,
     pub children: Vec<SubDiagnostic>,
@@ -161,9 +161,8 @@ pub enum DiagnosticId {
 #[derive(Clone, Debug, PartialEq, Hash, Encodable, Decodable)]
 pub struct SubDiagnostic {
     pub level: Level,
-    pub message: Vec<(DiagnosticMessage, Style)>,
+    pub messages: Vec<(DiagnosticMessage, Style)>,
     pub span: MultiSpan,
-    pub render_span: Option<MultiSpan>,
 }
 
 #[derive(Debug, PartialEq, Eq)]
@@ -216,14 +215,14 @@ impl StringPart {
 impl Diagnostic {
     #[track_caller]
     pub fn new<M: Into<DiagnosticMessage>>(level: Level, message: M) -> Self {
-        Diagnostic::new_with_code(level, None, message)
+        Diagnostic::new_with_messages(level, vec![(message.into(), Style::NoStyle)])
     }
 
     #[track_caller]
     pub fn new_with_messages(level: Level, messages: Vec<(DiagnosticMessage, Style)>) -> Self {
         Diagnostic {
             level,
-            message: messages,
+            messages,
             code: None,
             span: MultiSpan::new(),
             children: vec![],
@@ -235,26 +234,6 @@ impl Diagnostic {
         }
     }
 
-    #[track_caller]
-    pub(crate) fn new_with_code<M: Into<DiagnosticMessage>>(
-        level: Level,
-        code: Option<DiagnosticId>,
-        message: M,
-    ) -> Self {
-        Diagnostic {
-            level,
-            message: vec![(message.into(), Style::NoStyle)],
-            code,
-            span: MultiSpan::new(),
-            children: vec![],
-            suggestions: Ok(vec![]),
-            args: Default::default(),
-            sort_span: DUMMY_SP,
-            is_lint: false,
-            emitted_at: DiagnosticLocation::caller(),
-        }
-    }
-
     #[inline(always)]
     pub fn level(&self) -> Level {
         self.level
@@ -445,7 +424,7 @@ impl Diagnostic {
     /// Add a note attached to this diagnostic.
     #[rustc_lint_diagnostics]
     pub fn note(&mut self, msg: impl Into<SubdiagnosticMessage>) -> &mut Self {
-        self.sub(Level::Note, msg, MultiSpan::new(), None);
+        self.sub(Level::Note, msg, MultiSpan::new());
         self
     }
 
@@ -453,14 +432,14 @@ impl Diagnostic {
         &mut self,
         msg: Vec<(M, Style)>,
     ) -> &mut Self {
-        self.sub_with_highlights(Level::Note, msg, MultiSpan::new(), None);
+        self.sub_with_highlights(Level::Note, msg, MultiSpan::new());
         self
     }
 
     /// Prints the span with a note above it.
     /// This is like [`Diagnostic::note()`], but it gets its own span.
     pub fn note_once(&mut self, msg: impl Into<SubdiagnosticMessage>) -> &mut Self {
-        self.sub(Level::OnceNote, msg, MultiSpan::new(), None);
+        self.sub(Level::OnceNote, msg, MultiSpan::new());
         self
     }
 
@@ -472,7 +451,7 @@ impl Diagnostic {
         sp: S,
         msg: impl Into<SubdiagnosticMessage>,
     ) -> &mut Self {
-        self.sub(Level::Note, msg, sp.into(), None);
+        self.sub(Level::Note, msg, sp.into());
         self
     }
 
@@ -483,14 +462,14 @@ impl Diagnostic {
         sp: S,
         msg: impl Into<SubdiagnosticMessage>,
     ) -> &mut Self {
-        self.sub(Level::OnceNote, msg, sp.into(), None);
+        self.sub(Level::OnceNote, msg, sp.into());
         self
     }
 
     /// Add a warning attached to this diagnostic.
     #[rustc_lint_diagnostics]
     pub fn warn(&mut self, msg: impl Into<SubdiagnosticMessage>) -> &mut Self {
-        self.sub(Level::Warning(None), msg, MultiSpan::new(), None);
+        self.sub(Level::Warning(None), msg, MultiSpan::new());
         self
     }
 
@@ -502,27 +481,27 @@ impl Diagnostic {
         sp: S,
         msg: impl Into<SubdiagnosticMessage>,
     ) -> &mut Self {
-        self.sub(Level::Warning(None), msg, sp.into(), None);
+        self.sub(Level::Warning(None), msg, sp.into());
         self
     }
 
     /// Add a help message attached to this diagnostic.
     #[rustc_lint_diagnostics]
     pub fn help(&mut self, msg: impl Into<SubdiagnosticMessage>) -> &mut Self {
-        self.sub(Level::Help, msg, MultiSpan::new(), None);
+        self.sub(Level::Help, msg, MultiSpan::new());
         self
     }
 
     /// Prints the span with a help above it.
     /// This is like [`Diagnostic::help()`], but it gets its own span.
     pub fn help_once(&mut self, msg: impl Into<SubdiagnosticMessage>) -> &mut Self {
-        self.sub(Level::OnceHelp, msg, MultiSpan::new(), None);
+        self.sub(Level::OnceHelp, msg, MultiSpan::new());
         self
     }
 
     /// Add a help message attached to this diagnostic with a customizable highlighted message.
     pub fn highlighted_help(&mut self, msg: Vec<(String, Style)>) -> &mut Self {
-        self.sub_with_highlights(Level::Help, msg, MultiSpan::new(), None);
+        self.sub_with_highlights(Level::Help, msg, MultiSpan::new());
         self
     }
 
@@ -534,7 +513,7 @@ impl Diagnostic {
         sp: S,
         msg: impl Into<SubdiagnosticMessage>,
     ) -> &mut Self {
-        self.sub(Level::Help, msg, sp.into(), None);
+        self.sub(Level::Help, msg, sp.into());
         self
     }
 
@@ -925,7 +904,7 @@ impl Diagnostic {
     }
 
     pub fn set_primary_message(&mut self, msg: impl Into<DiagnosticMessage>) -> &mut Self {
-        self.message[0] = (msg.into(), Style::NoStyle);
+        self.messages[0] = (msg.into(), Style::NoStyle);
         self
     }
 
@@ -952,8 +931,8 @@ impl Diagnostic {
         self.args = args;
     }
 
-    pub fn styled_message(&self) -> &[(DiagnosticMessage, Style)] {
-        &self.message
+    pub fn messages(&self) -> &[(DiagnosticMessage, Style)] {
+        &self.messages
     }
 
     /// Helper function that takes a `SubdiagnosticMessage` and returns a `DiagnosticMessage` by
@@ -964,7 +943,7 @@ impl Diagnostic {
         attr: impl Into<SubdiagnosticMessage>,
     ) -> DiagnosticMessage {
         let msg =
-            self.message.iter().map(|(msg, _)| msg).next().expect("diagnostic with no messages");
+            self.messages.iter().map(|(msg, _)| msg).next().expect("diagnostic with no messages");
         msg.with_subdiagnostic_message(attr.into())
     }
 
@@ -972,21 +951,14 @@ impl Diagnostic {
     /// public methods above.
     ///
     /// Used by `proc_macro_server` for implementing `server::Diagnostic`.
-    pub fn sub(
-        &mut self,
-        level: Level,
-        message: impl Into<SubdiagnosticMessage>,
-        span: MultiSpan,
-        render_span: Option<MultiSpan>,
-    ) {
+    pub fn sub(&mut self, level: Level, message: impl Into<SubdiagnosticMessage>, span: MultiSpan) {
         let sub = SubDiagnostic {
             level,
-            message: vec![(
+            messages: vec![(
                 self.subdiagnostic_message_to_diagnostic_message(message),
                 Style::NoStyle,
             )],
             span,
-            render_span,
         };
         self.children.push(sub);
     }
@@ -996,15 +968,14 @@ impl Diagnostic {
     fn sub_with_highlights<M: Into<SubdiagnosticMessage>>(
         &mut self,
         level: Level,
-        message: Vec<(M, Style)>,
+        messages: Vec<(M, Style)>,
         span: MultiSpan,
-        render_span: Option<MultiSpan>,
     ) {
-        let message = message
+        let messages = messages
             .into_iter()
             .map(|m| (self.subdiagnostic_message_to_diagnostic_message(m.0), m.1))
             .collect();
-        let sub = SubDiagnostic { level, message, span, render_span };
+        let sub = SubDiagnostic { level, messages, span };
         self.children.push(sub);
     }
 
@@ -1022,7 +993,7 @@ impl Diagnostic {
     ) {
         (
             &self.level,
-            &self.message,
+            &self.messages,
             self.args().collect(),
             &self.code,
             &self.span,

compiler/rustc_errors/src/diagnostic_builder.rs

@@ -15,13 +15,13 @@ use std::ops::{Deref, DerefMut};
 use std::panic;
 use std::thread::panicking;
 
-/// Trait implemented by error types. This should not be implemented manually. Instead, use
+/// Trait implemented by error types. This is rarely implemented manually. Instead, use
 /// `#[derive(Diagnostic)]` -- see [rustc_macros::Diagnostic].
 #[rustc_diagnostic_item = "IntoDiagnostic"]
 pub trait IntoDiagnostic<'a, G: EmissionGuarantee = ErrorGuaranteed> {
     /// Write out as a diagnostic out of `DiagCtxt`.
     #[must_use]
-    fn into_diagnostic(self, dcx: &'a DiagCtxt) -> DiagnosticBuilder<'a, G>;
+    fn into_diagnostic(self, dcx: &'a DiagCtxt, level: Level) -> DiagnosticBuilder<'a, G>;
 }
 
 impl<'a, T, G> IntoDiagnostic<'a, G> for Spanned<T>
@@ -29,8 +29,8 @@ where
     T: IntoDiagnostic<'a, G>,
     G: EmissionGuarantee,
 {
-    fn into_diagnostic(self, dcx: &'a DiagCtxt) -> DiagnosticBuilder<'a, G> {
-        let mut diag = self.node.into_diagnostic(dcx);
+    fn into_diagnostic(self, dcx: &'a DiagCtxt, level: Level) -> DiagnosticBuilder<'a, G> {
+        let mut diag = self.node.into_diagnostic(dcx, level);
         diag.set_span(self.span);
         diag
     }
@@ -43,24 +43,7 @@ where
 /// extending `DiagCtxtFlags`.
 #[must_use]
 #[derive(Clone)]
-pub struct DiagnosticBuilder<'a, G: EmissionGuarantee> {
-    inner: DiagnosticBuilderInner<'a>,
-    _marker: PhantomData<G>,
-}
-
-/// This type exists only for `DiagnosticBuilder::forget_guarantee`, because it:
-/// 1. lacks the `G` parameter and therefore `DiagnosticBuilder<G1>` can be
-///    converted into `DiagnosticBuilder<G2>` while reusing the `inner` field
-/// 2. can implement the `Drop` "bomb" instead of `DiagnosticBuilder`, as it
-///    contains all of the data (`state` + `diagnostic`) of `DiagnosticBuilder`
-///
-/// The `diagnostic` field is not `Copy` and can't be moved out of whichever
-/// type implements the `Drop` "bomb", but because of the above two facts, that
-/// never needs to happen - instead, the whole `inner: DiagnosticBuilderInner`
-/// can be moved out of a `DiagnosticBuilder` and into another.
-#[must_use]
-#[derive(Clone)]
-struct DiagnosticBuilderInner<'a> {
+pub struct DiagnosticBuilder<'a, G: EmissionGuarantee = ErrorGuaranteed> {
     state: DiagnosticBuilderState<'a>,
 
     /// `Diagnostic` is a large type, and `DiagnosticBuilder` is often used as a
@@ -68,6 +51,8 @@ struct DiagnosticBuilderInner<'a> {
     /// In theory, return value optimization (RVO) should avoid unnecessary
     /// copying. In practice, it does not (at the time of writing).
     diagnostic: Box<Diagnostic>,
+
+    _marker: PhantomData<G>,
 }
 
 #[derive(Clone)]
@@ -83,7 +68,7 @@ enum DiagnosticBuilderState<'a> {
     /// assumed that `.emit()` was previously called, to end up in this state.
     ///
     /// While this is also used by `.cancel()`, this state is only observed by
-    /// the `Drop` `impl` of `DiagnosticBuilderInner`, as `.cancel()` takes
+    /// the `Drop` `impl` of `DiagnosticBuilder`, because `.cancel()` takes
     /// `self` by-value specifically to prevent any attempts to `.emit()`.
     ///
     // FIXME(eddyb) currently this doesn't prevent extending the `Diagnostic`,
@@ -101,47 +86,50 @@ rustc_data_structures::static_assert_size!(
 /// Trait for types that `DiagnosticBuilder::emit` can return as a "guarantee"
 /// (or "proof") token that the emission happened.
 pub trait EmissionGuarantee: Sized {
+    /// This exists so that bugs and fatal errors can both result in `!` (an
+    /// abort) when emitted, but have different aborting behaviour.
+    type EmitResult = Self;
+
     /// Implementation of `DiagnosticBuilder::emit`, fully controlled by each
     /// `impl` of `EmissionGuarantee`, to make it impossible to create a value
-    /// of `Self` without actually performing the emission.
+    /// of `Self::EmitResult` without actually performing the emission.
     #[track_caller]
-    fn diagnostic_builder_emit_producing_guarantee(db: &mut DiagnosticBuilder<'_, Self>) -> Self;
-
-    /// Creates a new `DiagnosticBuilder` that will return this type of guarantee.
-    #[track_caller]
-    fn make_diagnostic_builder(
-        dcx: &DiagCtxt,
-        msg: impl Into<DiagnosticMessage>,
-    ) -> DiagnosticBuilder<'_, Self>;
+    fn emit_producing_guarantee(db: &mut DiagnosticBuilder<'_, Self>) -> Self::EmitResult;
 }
 
-impl<'a> DiagnosticBuilder<'a, ErrorGuaranteed> {
-    /// Discard the guarantee `.emit()` would return, in favor of having the
-    /// type `DiagnosticBuilder<'a, ()>`. This may be necessary whenever there
-    /// is a common codepath handling both errors and warnings.
-    pub fn forget_guarantee(self) -> DiagnosticBuilder<'a, ()> {
-        DiagnosticBuilder { inner: self.inner, _marker: PhantomData }
+impl<'a, G: EmissionGuarantee> DiagnosticBuilder<'a, G> {
+    /// Most `emit_producing_guarantee` functions use this as a starting point.
+    fn emit_producing_nothing(&mut self) {
+        match self.state {
+            // First `.emit()` call, the `&DiagCtxt` is still available.
+            DiagnosticBuilderState::Emittable(dcx) => {
+                self.state = DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation;
+                dcx.emit_diagnostic_without_consuming(&mut self.diagnostic);
+            }
+            // `.emit()` was previously called, disallowed from repeating it.
+            DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation => {}
+        }
     }
 }
 
 // FIXME(eddyb) make `ErrorGuaranteed` impossible to create outside `.emit()`.
 impl EmissionGuarantee for ErrorGuaranteed {
-    fn diagnostic_builder_emit_producing_guarantee(db: &mut DiagnosticBuilder<'_, Self>) -> Self {
-        match db.inner.state {
+    fn emit_producing_guarantee(db: &mut DiagnosticBuilder<'_, Self>) -> Self::EmitResult {
+        // Contrast this with `emit_producing_nothing`.
+        match db.state {
             // First `.emit()` call, the `&DiagCtxt` is still available.
             DiagnosticBuilderState::Emittable(dcx) => {
-                db.inner.state = DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation;
-
-                let guar = dcx.emit_diagnostic_without_consuming(&mut db.inner.diagnostic);
+                db.state = DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation;
+                let guar = dcx.emit_diagnostic_without_consuming(&mut db.diagnostic);
 
                 // Only allow a guarantee if the `level` wasn't switched to a
                 // non-error - the field isn't `pub`, but the whole `Diagnostic`
                 // can be overwritten with a new one, thanks to `DerefMut`.
                 assert!(
-                    db.inner.diagnostic.is_error(),
+                    db.diagnostic.is_error(),
                     "emitted non-error ({:?}) diagnostic \
                      from `DiagnosticBuilder<ErrorGuaranteed>`",
-                    db.inner.diagnostic.level,
+                    db.diagnostic.level,
                 );
                 guar.unwrap()
             }
@@ -153,152 +141,58 @@ impl EmissionGuarantee for ErrorGuaranteed {
                 // non-error - the field isn't `pub`, but the whole `Diagnostic`
                 // can be overwritten with a new one, thanks to `DerefMut`.
                 assert!(
-                    db.inner.diagnostic.is_error(),
+                    db.diagnostic.is_error(),
                     "`DiagnosticBuilder<ErrorGuaranteed>`'s diagnostic \
                      became non-error ({:?}), after original `.emit()`",
-                    db.inner.diagnostic.level,
+                    db.diagnostic.level,
                 );
                 #[allow(deprecated)]
                 ErrorGuaranteed::unchecked_claim_error_was_emitted()
             }
         }
     }
-
-    #[track_caller]
-    fn make_diagnostic_builder(
-        dcx: &DiagCtxt,
-        msg: impl Into<DiagnosticMessage>,
-    ) -> DiagnosticBuilder<'_, Self> {
-        DiagnosticBuilder::new(dcx, Level::Error { lint: false }, msg)
-    }
 }
 
 // FIXME(eddyb) should there be a `Option<ErrorGuaranteed>` impl as well?
 impl EmissionGuarantee for () {
-    fn diagnostic_builder_emit_producing_guarantee(db: &mut DiagnosticBuilder<'_, Self>) -> Self {
-        match db.inner.state {
-            // First `.emit()` call, the `&DiagCtxt` is still available.
-            DiagnosticBuilderState::Emittable(dcx) => {
-                db.inner.state = DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation;
-
-                dcx.emit_diagnostic_without_consuming(&mut db.inner.diagnostic);
-            }
-            // `.emit()` was previously called, disallowed from repeating it.
-            DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation => {}
-        }
-    }
-
-    fn make_diagnostic_builder(
-        dcx: &DiagCtxt,
-        msg: impl Into<DiagnosticMessage>,
-    ) -> DiagnosticBuilder<'_, Self> {
-        DiagnosticBuilder::new(dcx, Level::Warning(None), msg)
-    }
-}
-
-/// Marker type which enables implementation of `create_note` and `emit_note` functions for
-/// note-without-error struct diagnostics.
-#[derive(Copy, Clone)]
-pub struct Noted;
-
-impl EmissionGuarantee for Noted {
-    fn diagnostic_builder_emit_producing_guarantee(db: &mut DiagnosticBuilder<'_, Self>) -> Self {
-        match db.inner.state {
-            // First `.emit()` call, the `&DiagCtxt` is still available.
-            DiagnosticBuilderState::Emittable(dcx) => {
-                db.inner.state = DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation;
-                dcx.emit_diagnostic_without_consuming(&mut db.inner.diagnostic);
-            }
-            // `.emit()` was previously called, disallowed from repeating it.
-            DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation => {}
-        }
-
-        Noted
-    }
-
-    fn make_diagnostic_builder(
-        dcx: &DiagCtxt,
-        msg: impl Into<DiagnosticMessage>,
-    ) -> DiagnosticBuilder<'_, Self> {
-        DiagnosticBuilder::new(dcx, Level::Note, msg)
+    fn emit_producing_guarantee(db: &mut DiagnosticBuilder<'_, Self>) -> Self::EmitResult {
+        db.emit_producing_nothing();
     }
 }
 
 /// Marker type which enables implementation of `create_bug` and `emit_bug` functions for
-/// bug struct diagnostics.
+/// bug diagnostics.
 #[derive(Copy, Clone)]
-pub struct Bug;
+pub struct BugAbort;
 
-impl EmissionGuarantee for Bug {
-    fn diagnostic_builder_emit_producing_guarantee(db: &mut DiagnosticBuilder<'_, Self>) -> Self {
-        match db.inner.state {
-            // First `.emit()` call, the `&DiagCtxt` is still available.
-            DiagnosticBuilderState::Emittable(dcx) => {
-                db.inner.state = DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation;
+impl EmissionGuarantee for BugAbort {
+    type EmitResult = !;
 
-                dcx.emit_diagnostic_without_consuming(&mut db.inner.diagnostic);
-            }
-            // `.emit()` was previously called, disallowed from repeating it.
-            DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation => {}
-        }
-        // Then panic. No need to return the marker type.
+    fn emit_producing_guarantee(db: &mut DiagnosticBuilder<'_, Self>) -> Self::EmitResult {
+        db.emit_producing_nothing();
         panic::panic_any(ExplicitBug);
     }
-
-    fn make_diagnostic_builder(
-        dcx: &DiagCtxt,
-        msg: impl Into<DiagnosticMessage>,
-    ) -> DiagnosticBuilder<'_, Self> {
-        DiagnosticBuilder::new(dcx, Level::Bug, msg)
-    }
 }
 
-impl EmissionGuarantee for ! {
-    fn diagnostic_builder_emit_producing_guarantee(db: &mut DiagnosticBuilder<'_, Self>) -> Self {
-        match db.inner.state {
-            // First `.emit()` call, the `&DiagCtxt` is still available.
-            DiagnosticBuilderState::Emittable(dcx) => {
-                db.inner.state = DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation;
+/// Marker type which enables implementation of `create_fatal` and `emit_fatal` functions for
+/// fatal diagnostics.
+#[derive(Copy, Clone)]
+pub struct FatalAbort;
 
-                dcx.emit_diagnostic_without_consuming(&mut db.inner.diagnostic);
-            }
-            // `.emit()` was previously called, disallowed from repeating it.
-            DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation => {}
-        }
-        // Then fatally error, returning `!`
+impl EmissionGuarantee for FatalAbort {
+    type EmitResult = !;
+
+    fn emit_producing_guarantee(db: &mut DiagnosticBuilder<'_, Self>) -> Self::EmitResult {
+        db.emit_producing_nothing();
         crate::FatalError.raise()
     }
-
-    fn make_diagnostic_builder(
-        dcx: &DiagCtxt,
-        msg: impl Into<DiagnosticMessage>,
-    ) -> DiagnosticBuilder<'_, Self> {
-        DiagnosticBuilder::new(dcx, Level::Fatal, msg)
-    }
 }
 
 impl EmissionGuarantee for rustc_span::fatal_error::FatalError {
-    fn diagnostic_builder_emit_producing_guarantee(db: &mut DiagnosticBuilder<'_, Self>) -> Self {
-        match db.inner.state {
-            // First `.emit()` call, the `&DiagCtxt` is still available.
-            DiagnosticBuilderState::Emittable(dcx) => {
-                db.inner.state = DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation;
-
-                dcx.emit_diagnostic_without_consuming(&mut db.inner.diagnostic);
-            }
-            // `.emit()` was previously called, disallowed from repeating it.
-            DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation => {}
-        }
-        // Then fatally error..
+    fn emit_producing_guarantee(db: &mut DiagnosticBuilder<'_, Self>) -> Self::EmitResult {
+        db.emit_producing_nothing();
         rustc_span::fatal_error::FatalError
     }
-
-    fn make_diagnostic_builder(
-        dcx: &DiagCtxt,
-        msg: impl Into<DiagnosticMessage>,
-    ) -> DiagnosticBuilder<'_, Self> {
-        DiagnosticBuilder::new(dcx, Level::Fatal, msg)
-    }
 }
 
 /// In general, the `DiagnosticBuilder` uses deref to allow access to
@@ -318,7 +212,7 @@ macro_rules! forward {
         $(#[$attrs])*
         #[doc = concat!("See [`Diagnostic::", stringify!($n), "()`].")]
         pub fn $n(&mut self, $($name: $ty),*) -> &mut Self {
-            self.inner.diagnostic.$n($($name),*);
+            self.diagnostic.$n($($name),*);
             self
         }
     };
@@ -328,27 +222,21 @@ impl<G: EmissionGuarantee> Deref for DiagnosticBuilder<'_, G> {
     type Target = Diagnostic;
 
     fn deref(&self) -> &Diagnostic {
-        &self.inner.diagnostic
+        &self.diagnostic
     }
 }
 
 impl<G: EmissionGuarantee> DerefMut for DiagnosticBuilder<'_, G> {
     fn deref_mut(&mut self) -> &mut Diagnostic {
-        &mut self.inner.diagnostic
+        &mut self.diagnostic
     }
 }
 
 impl<'a, G: EmissionGuarantee> DiagnosticBuilder<'a, G> {
-    /// Convenience function for internal use, clients should use one of the
-    /// `struct_*` methods on [`DiagCtxt`].
+    #[rustc_lint_diagnostics]
     #[track_caller]
-    pub(crate) fn new<M: Into<DiagnosticMessage>>(
-        dcx: &'a DiagCtxt,
-        level: Level,
-        message: M,
-    ) -> Self {
-        let diagnostic = Diagnostic::new(level, message);
-        Self::new_diagnostic(dcx, diagnostic)
+    pub fn new<M: Into<DiagnosticMessage>>(dcx: &'a DiagCtxt, level: Level, message: M) -> Self {
+        Self::new_diagnostic(dcx, Diagnostic::new(level, message))
     }
 
     /// Creates a new `DiagnosticBuilder` with an already constructed
@@ -357,10 +245,8 @@ impl<'a, G: EmissionGuarantee> DiagnosticBuilder<'a, G> {
     pub(crate) fn new_diagnostic(dcx: &'a DiagCtxt, diagnostic: Diagnostic) -> Self {
         debug!("Created new diagnostic");
         Self {
-            inner: DiagnosticBuilderInner {
-                state: DiagnosticBuilderState::Emittable(dcx),
-                diagnostic: Box::new(diagnostic),
-            },
+            state: DiagnosticBuilderState::Emittable(dcx),
+            diagnostic: Box::new(diagnostic),
             _marker: PhantomData,
         }
     }
@@ -369,8 +255,8 @@ impl<'a, G: EmissionGuarantee> DiagnosticBuilder<'a, G> {
     /// but there are various places that rely on continuing to use `self`
     /// after calling `emit`.
     #[track_caller]
-    pub fn emit(&mut self) -> G {
-        G::diagnostic_builder_emit_producing_guarantee(self)
+    pub fn emit(&mut self) -> G::EmitResult {
+        G::emit_producing_guarantee(self)
     }
 
     /// Emit the diagnostic unless `delay` is true,
@@ -378,7 +264,7 @@ impl<'a, G: EmissionGuarantee> DiagnosticBuilder<'a, G> {
     ///
     /// See `emit` and `delay_as_bug` for details.
     #[track_caller]
-    pub fn emit_unless(&mut self, delay: bool) -> G {
+    pub fn emit_unless(&mut self, delay: bool) -> G::EmitResult {
         if delay {
             self.downgrade_to_delayed_bug();
         }
@@ -392,7 +278,7 @@ impl<'a, G: EmissionGuarantee> DiagnosticBuilder<'a, G> {
     /// which may be expected to *guarantee* the emission of an error, either
     /// at the time of the call, or through a prior `.emit()` call.
     pub fn cancel(mut self) {
-        self.inner.state = DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation;
+        self.state = DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation;
         drop(self);
     }
 
@@ -400,17 +286,17 @@ impl<'a, G: EmissionGuarantee> DiagnosticBuilder<'a, G> {
     /// later stage of the compiler. The diagnostic can be accessed with
     /// the provided `span` and `key` through [`DiagCtxt::steal_diagnostic()`].
     ///
-    /// As with `buffer`, this is unless the handler has disabled such buffering.
+    /// As with `buffer`, this is unless the dcx has disabled such buffering.
     pub fn stash(self, span: Span, key: StashKey) {
-        if let Some((diag, handler)) = self.into_diagnostic() {
-            handler.stash_diagnostic(span, key, diag);
+        if let Some((diag, dcx)) = self.into_diagnostic() {
+            dcx.stash_diagnostic(span, key, diag);
         }
     }
 
     /// Converts the builder to a `Diagnostic` for later emission,
-    /// unless handler has disabled such buffering, or `.emit()` was called.
+    /// unless dcx has disabled such buffering, or `.emit()` was called.
     pub fn into_diagnostic(mut self) -> Option<(Diagnostic, &'a DiagCtxt)> {
-        let dcx = match self.inner.state {
+        let dcx = match self.state {
             // No `.emit()` calls, the `&DiagCtxt` is still available.
             DiagnosticBuilderState::Emittable(dcx) => dcx,
             // `.emit()` was previously called, nothing we can do.
@@ -428,7 +314,7 @@ impl<'a, G: EmissionGuarantee> DiagnosticBuilder<'a, G> {
 
         // Take the `Diagnostic` by replacing it with a dummy.
         let dummy = Diagnostic::new(Level::Allow, DiagnosticMessage::from(""));
-        let diagnostic = std::mem::replace(&mut *self.inner.diagnostic, dummy);
+        let diagnostic = std::mem::replace(&mut *self.diagnostic, dummy);
 
         // Disable the ICE on `Drop`.
         self.cancel();
@@ -442,14 +328,14 @@ impl<'a, G: EmissionGuarantee> DiagnosticBuilder<'a, G> {
 
     /// Retrieves the [`DiagCtxt`] if available
     pub fn dcx(&self) -> Option<&DiagCtxt> {
-        match self.inner.state {
+        match self.state {
             DiagnosticBuilderState::Emittable(dcx) => Some(dcx),
             DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation => None,
         }
     }
 
     /// Buffers the diagnostic for later emission,
-    /// unless handler has disabled such buffering.
+    /// unless dcx has disabled such buffering.
     pub fn buffer(self, buffered_diagnostics: &mut Vec<Diagnostic>) {
         buffered_diagnostics.extend(self.into_diagnostic().map(|(diag, _)| diag));
     }
@@ -465,7 +351,7 @@ impl<'a, G: EmissionGuarantee> DiagnosticBuilder<'a, G> {
     /// In the meantime, though, callsites are required to deal with the "bug"
     /// locally in whichever way makes the most sense.
     #[track_caller]
-    pub fn delay_as_bug(&mut self) -> G {
+    pub fn delay_as_bug(&mut self) -> G::EmitResult {
         self.downgrade_to_delayed_bug();
         self.emit()
     }
@@ -630,13 +516,13 @@ impl<'a, G: EmissionGuarantee> DiagnosticBuilder<'a, G> {
 
 impl<G: EmissionGuarantee> Debug for DiagnosticBuilder<'_, G> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        self.inner.diagnostic.fmt(f)
+        self.diagnostic.fmt(f)
     }
 }
 
 /// Destructor bomb - a `DiagnosticBuilder` must be either emitted or cancelled
 /// or we emit a bug.
-impl Drop for DiagnosticBuilderInner<'_> {
+impl<G: EmissionGuarantee> Drop for DiagnosticBuilder<'_, G> {
     fn drop(&mut self) {
         match self.state {
             // No `.emit()` or `.cancel()` calls.

compiler/rustc_errors/src/diagnostic_impls.rs

@@ -1,10 +1,12 @@
 use crate::diagnostic::DiagnosticLocation;
 use crate::{fluent_generated as fluent, AddToDiagnostic};
-use crate::{DiagCtxt, DiagnosticArgValue, DiagnosticBuilder, IntoDiagnostic, IntoDiagnosticArg};
+use crate::{
+    DiagCtxt, DiagnosticArgValue, DiagnosticBuilder, EmissionGuarantee, IntoDiagnostic,
+    IntoDiagnosticArg, Level,
+};
 use rustc_ast as ast;
 use rustc_ast_pretty::pprust;
 use rustc_hir as hir;
-use rustc_lint_defs::Level;
 use rustc_span::edition::Edition;
 use rustc_span::symbol::{Ident, MacroRulesNormalizedIdent, Symbol};
 use rustc_span::Span;
@@ -216,7 +218,7 @@ impl IntoDiagnosticArg for ast::Visibility {
     }
 }
 
-impl IntoDiagnosticArg for Level {
+impl IntoDiagnosticArg for rustc_lint_defs::Level {
     fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
         DiagnosticArgValue::Str(Cow::Borrowed(self.to_cmd_flag()))
     }
@@ -245,19 +247,20 @@ impl<Id> IntoDiagnosticArg for hir::def::Res<Id> {
     }
 }
 
-impl IntoDiagnostic<'_, !> for TargetDataLayoutErrors<'_> {
-    fn into_diagnostic(self, dcx: &DiagCtxt) -> DiagnosticBuilder<'_, !> {
+impl<G: EmissionGuarantee> IntoDiagnostic<'_, G> for TargetDataLayoutErrors<'_> {
+    fn into_diagnostic(self, dcx: &DiagCtxt, level: Level) -> DiagnosticBuilder<'_, G> {
         let mut diag;
         match self {
             TargetDataLayoutErrors::InvalidAddressSpace { addr_space, err, cause } => {
-                diag = dcx.struct_fatal(fluent::errors_target_invalid_address_space);
+                diag =
+                    DiagnosticBuilder::new(dcx, level, fluent::errors_target_invalid_address_space);
                 diag.set_arg("addr_space", addr_space);
                 diag.set_arg("cause", cause);
                 diag.set_arg("err", err);
                 diag
             }
             TargetDataLayoutErrors::InvalidBits { kind, bit, cause, err } => {
-                diag = dcx.struct_fatal(fluent::errors_target_invalid_bits);
+                diag = DiagnosticBuilder::new(dcx, level, fluent::errors_target_invalid_bits);
                 diag.set_arg("kind", kind);
                 diag.set_arg("bit", bit);
                 diag.set_arg("cause", cause);
@@ -265,31 +268,39 @@ impl IntoDiagnostic<'_, !> for TargetDataLayoutErrors<'_> {
                 diag
             }
             TargetDataLayoutErrors::MissingAlignment { cause } => {
-                diag = dcx.struct_fatal(fluent::errors_target_missing_alignment);
+                diag = DiagnosticBuilder::new(dcx, level, fluent::errors_target_missing_alignment);
                 diag.set_arg("cause", cause);
                 diag
             }
             TargetDataLayoutErrors::InvalidAlignment { cause, err } => {
-                diag = dcx.struct_fatal(fluent::errors_target_invalid_alignment);
+                diag = DiagnosticBuilder::new(dcx, level, fluent::errors_target_invalid_alignment);
                 diag.set_arg("cause", cause);
                 diag.set_arg("err_kind", err.diag_ident());
                 diag.set_arg("align", err.align());
                 diag
             }
             TargetDataLayoutErrors::InconsistentTargetArchitecture { dl, target } => {
-                diag = dcx.struct_fatal(fluent::errors_target_inconsistent_architecture);
+                diag = DiagnosticBuilder::new(
+                    dcx,
+                    level,
+                    fluent::errors_target_inconsistent_architecture,
+                );
                 diag.set_arg("dl", dl);
                 diag.set_arg("target", target);
                 diag
             }
             TargetDataLayoutErrors::InconsistentTargetPointerWidth { pointer_size, target } => {
-                diag = dcx.struct_fatal(fluent::errors_target_inconsistent_pointer_width);
+                diag = DiagnosticBuilder::new(
+                    dcx,
+                    level,
+                    fluent::errors_target_inconsistent_pointer_width,
+                );
                 diag.set_arg("pointer_size", pointer_size);
                 diag.set_arg("target", target);
                 diag
             }
             TargetDataLayoutErrors::InvalidBitsSize { err } => {
-                diag = dcx.struct_fatal(fluent::errors_target_invalid_bits_size);
+                diag = DiagnosticBuilder::new(dcx, level, fluent::errors_target_invalid_bits_size);
                 diag.set_arg("err", err);
                 diag
             }
@@ -301,25 +312,13 @@ impl IntoDiagnostic<'_, !> for TargetDataLayoutErrors<'_> {
 pub struct SingleLabelManySpans {
     pub spans: Vec<Span>,
     pub label: &'static str,
-    pub kind: LabelKind,
 }
 impl AddToDiagnostic for SingleLabelManySpans {
     fn add_to_diagnostic_with<F>(self, diag: &mut crate::Diagnostic, _: F) {
-        match self.kind {
-            LabelKind::Note => diag.span_note(self.spans, self.label),
-            LabelKind::Label => diag.span_labels(self.spans, self.label),
-            LabelKind::Help => diag.span_help(self.spans, self.label),
-        };
+        diag.span_labels(self.spans, self.label);
     }
 }
 
-/// The kind of label to attach when using [`SingleLabelManySpans`]
-pub enum LabelKind {
-    Note,
-    Label,
-    Help,
-}
-
 #[derive(Subdiagnostic)]
 #[label(errors_expected_lifetime_parameter)]
 pub struct ExpectedLifetimeParameter {
@@ -362,9 +361,9 @@ impl IntoDiagnosticArg for Backtrace {
 pub struct InvalidFlushedDelayedDiagnosticLevel {
     #[primary_span]
     pub span: Span,
-    pub level: rustc_errors::Level,
+    pub level: Level,
 }
-impl IntoDiagnosticArg for rustc_errors::Level {
+impl IntoDiagnosticArg for Level {
     fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
         DiagnosticArgValue::Str(Cow::from(self.to_string()))
     }

compiler/rustc_errors/src/emitter.rs

@@ -350,9 +350,8 @@ pub trait Emitter: Translate {
 
                 children.push(SubDiagnostic {
                     level: Level::Note,
-                    message: vec![(DiagnosticMessage::from(msg), Style::NoStyle)],
+                    messages: vec![(DiagnosticMessage::from(msg), Style::NoStyle)],
                     span: MultiSpan::new(),
-                    render_span: None,
                 });
             }
         }
@@ -533,7 +532,7 @@ impl Emitter for EmitterWriter {
 
         self.emit_messages_default(
             &diag.level,
-            &diag.message,
+            &diag.messages,
             &fluent_args,
             &diag.code,
             &primary_span,
@@ -1228,10 +1227,10 @@ impl EmitterWriter {
 
     /// Adds a left margin to every line but the first, given a padding length and the label being
     /// displayed, keeping the provided highlighting.
-    fn msg_to_buffer(
+    fn msgs_to_buffer(
         &self,
         buffer: &mut StyledBuffer,
-        msg: &[(DiagnosticMessage, Style)],
+        msgs: &[(DiagnosticMessage, Style)],
         args: &FluentArgs<'_>,
         padding: usize,
         label: &str,
@@ -1267,7 +1266,7 @@ impl EmitterWriter {
 
         // Provided the following diagnostic message:
         //
-        //     let msg = vec![
+        //     let msgs = vec![
         //       ("
         //       ("highlighted multiline\nstring to\nsee how it ", Style::NoStyle),
         //       ("looks", Style::Highlight),
@@ -1284,7 +1283,7 @@ impl EmitterWriter {
         //                see how it *looks* with
         //                very *weird* formats
         //                see?
-        for (text, style) in msg.iter() {
+        for (text, style) in msgs.iter() {
             let text = self.translate_message(text, args).map_err(Report::new).unwrap();
             let text = &normalize_whitespace(&text);
             let lines = text.split('\n').collect::<Vec<_>>();
@@ -1303,10 +1302,10 @@ impl EmitterWriter {
     }
 
     #[instrument(level = "trace", skip(self, args), ret)]
-    fn emit_message_default(
+    fn emit_messages_default_inner(
         &mut self,
         msp: &MultiSpan,
-        msg: &[(DiagnosticMessage, Style)],
+        msgs: &[(DiagnosticMessage, Style)],
         args: &FluentArgs<'_>,
         code: &Option<DiagnosticId>,
         level: &Level,
@@ -1327,7 +1326,7 @@ impl EmitterWriter {
                 buffer.append(0, level.to_str(), Style::MainHeaderMsg);
                 buffer.append(0, ": ", Style::NoStyle);
             }
-            self.msg_to_buffer(&mut buffer, msg, args, max_line_num_len, "note", None);
+            self.msgs_to_buffer(&mut buffer, msgs, args, max_line_num_len, "note", None);
         } else {
             let mut label_width = 0;
             // The failure note level itself does not provide any useful diagnostic information
@@ -1360,7 +1359,7 @@ impl EmitterWriter {
                 buffer.append(0, ": ", header_style);
                 label_width += 2;
             }
-            for (text, _) in msg.iter() {
+            for (text, _) in msgs.iter() {
                 let text = self.translate_message(text, args).map_err(Report::new).unwrap();
                 // Account for newlines to align output to its label.
                 for (line, text) in normalize_whitespace(&text).lines().enumerate() {
@@ -1747,7 +1746,7 @@ impl EmitterWriter {
         buffer.append(0, level.to_str(), Style::Level(*level));
         buffer.append(0, ": ", Style::HeaderMsg);
 
-        self.msg_to_buffer(
+        self.msgs_to_buffer(
             &mut buffer,
             &[(suggestion.msg.to_owned(), Style::NoStyle)],
             args,
@@ -2074,7 +2073,7 @@ impl EmitterWriter {
     fn emit_messages_default(
         &mut self,
         level: &Level,
-        message: &[(DiagnosticMessage, Style)],
+        messages: &[(DiagnosticMessage, Style)],
         args: &FluentArgs<'_>,
         code: &Option<DiagnosticId>,
         span: &MultiSpan,
@@ -2089,9 +2088,9 @@ impl EmitterWriter {
             num_decimal_digits(n)
         };
 
-        match self.emit_message_default(
+        match self.emit_messages_default_inner(
             span,
-            message,
+            messages,
             args,
             code,
             level,
@@ -2118,10 +2117,10 @@ impl EmitterWriter {
                 }
                 if !self.short_message {
                     for child in children {
-                        let span = child.render_span.as_ref().unwrap_or(&child.span);
-                        if let Err(err) = self.emit_message_default(
+                        let span = &child.span;
+                        if let Err(err) = self.emit_messages_default_inner(
                             span,
-                            &child.message,
+                            &child.messages,
                             args,
                             &None,
                             &child.level,
@@ -2138,7 +2137,7 @@ impl EmitterWriter {
                                 // do not display this suggestion, it is meant only for tools
                             }
                             SuggestionStyle::HideCodeAlways => {
-                                if let Err(e) = self.emit_message_default(
+                                if let Err(e) = self.emit_messages_default_inner(
                                     &MultiSpan::new(),
                                     &[(sugg.msg.to_owned(), Style::HeaderMsg)],
                                     args,

compiler/rustc_errors/src/json.rs

@@ -398,7 +398,7 @@ impl Diagnostic {
         let output = Arc::try_unwrap(output.0).unwrap().into_inner().unwrap();
         let output = String::from_utf8(output).unwrap();
 
-        let translated_message = je.translate_messages(&diag.message, &args);
+        let translated_message = je.translate_messages(&diag.messages, &args);
         Diagnostic {
             message: translated_message.to_string(),
             code: DiagnosticCode::map_opt_string(diag.code.clone(), je),
@@ -419,16 +419,12 @@ impl Diagnostic {
         args: &FluentArgs<'_>,
         je: &JsonEmitter,
     ) -> Diagnostic {
-        let translated_message = je.translate_messages(&diag.message, args);
+        let translated_message = je.translate_messages(&diag.messages, args);
         Diagnostic {
             message: translated_message.to_string(),
             code: None,
             level: diag.level.to_str(),
-            spans: diag
-                .render_span
-                .as_ref()
-                .map(|sp| DiagnosticSpan::from_multispan(sp, args, je))
-                .unwrap_or_else(|| DiagnosticSpan::from_multispan(&diag.span, args, je)),
+            spans: DiagnosticSpan::from_multispan(&diag.span, args, je),
             children: vec![],
             rendered: None,
         }

compiler/rustc_errors/src/lib.rs

@@ -6,6 +6,7 @@
 #![doc(rust_logo)]
 #![feature(rustdoc_internals)]
 #![feature(array_windows)]
+#![feature(associated_type_defaults)]
 #![feature(extract_if)]
 #![feature(if_let_guard)]
 #![feature(let_chains)]
@@ -26,26 +27,42 @@ extern crate tracing;
 
 extern crate self as rustc_errors;
 
+pub use diagnostic::{
+    AddToDiagnostic, DecorateLint, Diagnostic, DiagnosticArg, DiagnosticArgValue, DiagnosticId,
+    DiagnosticStyledString, IntoDiagnosticArg, SubDiagnostic,
+};
+pub use diagnostic_builder::{
+    BugAbort, DiagnosticBuilder, EmissionGuarantee, FatalAbort, IntoDiagnostic,
+};
+pub use diagnostic_impls::{
+    DiagnosticArgFromDisplay, DiagnosticSymbolList, ExpectedLifetimeParameter,
+    IndicateAnonymousLifetime, InvalidFlushedDelayedDiagnosticLevel, SingleLabelManySpans,
+};
 pub use emitter::ColorConfig;
+pub use rustc_error_messages::{
+    fallback_fluent_bundle, fluent_bundle, DelayDm, DiagnosticMessage, FluentBundle,
+    LanguageIdentifier, LazyFallbackBundle, MultiSpan, SpanLabel, SubdiagnosticMessage,
+};
+pub use rustc_lint_defs::{pluralize, Applicability};
+pub use rustc_span::fatal_error::{FatalError, FatalErrorMarker};
+pub use rustc_span::ErrorGuaranteed;
+pub use snippet::Style;
 
-use rustc_lint_defs::LintExpectationId;
-use Level::*;
+// Used by external projects such as `rust-gpu`.
+// See https://github.com/rust-lang/rust/pull/115393.
+pub use termcolor::{Color, ColorSpec, WriteColor};
 
+use crate::diagnostic_impls::{DelayedAtWithNewline, DelayedAtWithoutNewline};
 use emitter::{is_case_difference, DynEmitter, Emitter, EmitterWriter};
 use registry::Registry;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexMap, FxIndexSet};
 use rustc_data_structures::stable_hasher::{Hash128, StableHasher};
 use rustc_data_structures::sync::{Lock, Lrc};
 use rustc_data_structures::AtomicRef;
-pub use rustc_error_messages::{
-    fallback_fluent_bundle, fluent_bundle, DelayDm, DiagnosticMessage, FluentBundle,
-    LanguageIdentifier, LazyFallbackBundle, MultiSpan, SpanLabel, SubdiagnosticMessage,
-};
-pub use rustc_lint_defs::{pluralize, Applicability};
+use rustc_lint_defs::LintExpectationId;
 use rustc_span::source_map::SourceMap;
-pub use rustc_span::ErrorGuaranteed;
 use rustc_span::{Loc, Span, DUMMY_SP};
-
+use std::backtrace::{Backtrace, BacktraceStatus};
 use std::borrow::Cow;
 use std::error::Report;
 use std::fmt;
@@ -55,9 +72,7 @@ use std::num::NonZeroUsize;
 use std::panic;
 use std::path::{Path, PathBuf};
 
-// Used by external projects such as `rust-gpu`.
-// See https://github.com/rust-lang/rust/pull/115393.
-pub use termcolor::{Color, ColorSpec, WriteColor};
+use Level::*;
 
 pub mod annotate_snippet_emitter_writer;
 mod diagnostic;
@@ -75,10 +90,7 @@ mod styled_buffer;
 mod tests;
 pub mod translation;
 
-pub use diagnostic_builder::IntoDiagnostic;
-pub use snippet::Style;
-
-pub type PErr<'a> = DiagnosticBuilder<'a, ErrorGuaranteed>;
+pub type PErr<'a> = DiagnosticBuilder<'a>;
 pub type PResult<'a, T> = Result<T, PErr<'a>>;
 
 rustc_fluent_macro::fluent_messages! { "../messages.ftl" }
@@ -162,7 +174,7 @@ pub struct SubstitutionPart {
 /// Used to translate between `Span`s and byte positions within a single output line in highlighted
 /// code of structured suggestions.
 #[derive(Debug, Clone, Copy)]
-pub struct SubstitutionHighlight {
+pub(crate) struct SubstitutionHighlight {
     start: usize,
     end: usize,
 }
@@ -189,7 +201,7 @@ impl SubstitutionPart {
 impl CodeSuggestion {
     /// Returns the assembled code suggestions, whether they should be shown with an underline
     /// and whether the substitution only differs in capitalization.
-    pub fn splice_lines(
+    pub(crate) fn splice_lines(
         &self,
         sm: &SourceMap,
     ) -> Vec<(String, Vec<SubstitutionPart>, Vec<Vec<SubstitutionHighlight>>, bool)> {
@@ -386,8 +398,6 @@ impl CodeSuggestion {
     }
 }
 
-pub use rustc_span::fatal_error::{FatalError, FatalErrorMarker};
-
 /// Signifies that the compiler died with an explicit call to `.bug`
 /// or `.span_bug` rather than a failed assertion, etc.
 pub struct ExplicitBug;
@@ -396,20 +406,7 @@ pub struct ExplicitBug;
 /// rather than a failed assertion, etc.
 pub struct DelayedBugPanic;
 
-use crate::diagnostic_impls::{DelayedAtWithNewline, DelayedAtWithoutNewline};
-pub use diagnostic::{
-    AddToDiagnostic, DecorateLint, Diagnostic, DiagnosticArg, DiagnosticArgValue, DiagnosticId,
-    DiagnosticStyledString, IntoDiagnosticArg, SubDiagnostic,
-};
-pub use diagnostic_builder::{DiagnosticBuilder, EmissionGuarantee, Noted};
-pub use diagnostic_impls::{
-    DiagnosticArgFromDisplay, DiagnosticSymbolList, ExpectedLifetimeParameter,
-    IndicateAnonymousLifetime, InvalidFlushedDelayedDiagnosticLevel, LabelKind,
-    SingleLabelManySpans,
-};
-use std::backtrace::{Backtrace, BacktraceStatus};
-
-/// A handler deals with errors and other compiler output.
+/// A `DiagCtxt` deals with errors and other compiler output.
 /// Certain errors (fatal, bug, unimpl) may cause immediate exit,
 /// others log errors for later reporting.
 pub struct DiagCtxt {
@@ -446,7 +443,7 @@ struct DiagCtxtInner {
     emitted_diagnostic_codes: FxIndexSet<DiagnosticId>,
 
     /// This set contains a hash of every diagnostic that has been emitted by
-    /// this handler. These hashes is used to avoid emitting the same error
+    /// this `DiagCtxt`. These hashes is used to avoid emitting the same error
     /// twice.
     emitted_diagnostics: FxHashSet<Hash128>,
 
@@ -676,7 +673,7 @@ impl DiagCtxt {
         let key = (span.with_parent(None), key);
 
         if diag.is_error() {
-            if matches!(diag.level, Level::Error { lint: true }) {
+            if matches!(diag.level, Error { lint: true }) {
                 inner.lint_err_count += 1;
             } else {
                 inner.err_count += 1;
@@ -700,7 +697,7 @@ impl DiagCtxt {
         let key = (span.with_parent(None), key);
         let diag = inner.stashed_diagnostics.remove(&key)?;
         if diag.is_error() {
-            if matches!(diag.level, Level::Error { lint: true }) {
+            if matches!(diag.level, Error { lint: true }) {
                 inner.lint_err_count -= 1;
             } else {
                 inner.err_count -= 1;
@@ -722,21 +719,6 @@ impl DiagCtxt {
         self.inner.borrow_mut().emit_stashed_diagnostics()
     }
 
-    /// Construct a builder with the `msg` at the level appropriate for the
-    /// specific `EmissionGuarantee`.
-    ///
-    /// Note: this is necessary for `derive(Diagnostic)`, but shouldn't be used
-    /// outside of that. Instead use `struct_err`, `struct_warn`, etc., which
-    /// make the diagnostic kind clearer.
-    #[rustc_lint_diagnostics]
-    #[track_caller]
-    pub fn struct_diagnostic<G: EmissionGuarantee>(
-        &self,
-        msg: impl Into<DiagnosticMessage>,
-    ) -> DiagnosticBuilder<'_, G> {
-        G::make_diagnostic_builder(self, msg)
-    }
-
     /// Construct a builder at the `Warning` level at the given `span` and with the `msg`.
     ///
     /// Attempting to `.emit()` the builder will only emit if either:
@@ -754,37 +736,6 @@ impl DiagCtxt {
         result
     }
 
-    /// Construct a builder at the `Warning` level at the given `span` and with the `msg`.
-    /// The `id` is used for lint emissions which should also fulfill a lint expectation.
-    ///
-    /// Attempting to `.emit()` the builder will only emit if either:
-    /// * `can_emit_warnings` is `true`
-    /// * `is_force_warn` was set in `DiagnosticId::Lint`
-    #[track_caller]
-    pub fn struct_span_warn_with_expectation(
-        &self,
-        span: impl Into<MultiSpan>,
-        msg: impl Into<DiagnosticMessage>,
-        id: LintExpectationId,
-    ) -> DiagnosticBuilder<'_, ()> {
-        let mut result = self.struct_warn_with_expectation(msg, id);
-        result.set_span(span);
-        result
-    }
-
-    /// Construct a builder at the `Allow` level at the given `span` and with the `msg`.
-    #[rustc_lint_diagnostics]
-    #[track_caller]
-    pub fn struct_span_allow(
-        &self,
-        span: impl Into<MultiSpan>,
-        msg: impl Into<DiagnosticMessage>,
-    ) -> DiagnosticBuilder<'_, ()> {
-        let mut result = self.struct_allow(msg);
-        result.set_span(span);
-        result
-    }
-
     /// Construct a builder at the `Warning` level at the given `span` and with the `msg`.
     /// Also include a code.
     #[rustc_lint_diagnostics]
@@ -808,29 +759,14 @@ impl DiagCtxt {
     #[rustc_lint_diagnostics]
     #[track_caller]
     pub fn struct_warn(&self, msg: impl Into<DiagnosticMessage>) -> DiagnosticBuilder<'_, ()> {
-        DiagnosticBuilder::new(self, Level::Warning(None), msg)
-    }
-
-    /// Construct a builder at the `Warning` level with the `msg`. The `id` is used for
-    /// lint emissions which should also fulfill a lint expectation.
-    ///
-    /// Attempting to `.emit()` the builder will only emit if either:
-    /// * `can_emit_warnings` is `true`
-    /// * `is_force_warn` was set in `DiagnosticId::Lint`
-    #[track_caller]
-    pub fn struct_warn_with_expectation(
-        &self,
-        msg: impl Into<DiagnosticMessage>,
-        id: LintExpectationId,
-    ) -> DiagnosticBuilder<'_, ()> {
-        DiagnosticBuilder::new(self, Level::Warning(Some(id)), msg)
+        DiagnosticBuilder::new(self, Warning(None), msg)
     }
 
     /// Construct a builder at the `Allow` level with the `msg`.
     #[rustc_lint_diagnostics]
     #[track_caller]
     pub fn struct_allow(&self, msg: impl Into<DiagnosticMessage>) -> DiagnosticBuilder<'_, ()> {
-        DiagnosticBuilder::new(self, Level::Allow, msg)
+        DiagnosticBuilder::new(self, Allow, msg)
     }
 
     /// Construct a builder at the `Expect` level with the `msg`.
@@ -841,7 +777,7 @@ impl DiagCtxt {
         msg: impl Into<DiagnosticMessage>,
         id: LintExpectationId,
     ) -> DiagnosticBuilder<'_, ()> {
-        DiagnosticBuilder::new(self, Level::Expect(id), msg)
+        DiagnosticBuilder::new(self, Expect(id), msg)
     }
 
     /// Construct a builder at the `Error` level at the given `span` and with the `msg`.
@@ -851,7 +787,7 @@ impl DiagCtxt {
         &self,
         span: impl Into<MultiSpan>,
         msg: impl Into<DiagnosticMessage>,
-    ) -> DiagnosticBuilder<'_, ErrorGuaranteed> {
+    ) -> DiagnosticBuilder<'_> {
         let mut result = self.struct_err(msg);
         result.set_span(span);
         result
@@ -865,7 +801,7 @@ impl DiagCtxt {
         span: impl Into<MultiSpan>,
         msg: impl Into<DiagnosticMessage>,
         code: DiagnosticId,
-    ) -> DiagnosticBuilder<'_, ErrorGuaranteed> {
+    ) -> DiagnosticBuilder<'_> {
         let mut result = self.struct_span_err(span, msg);
         result.code(code);
         result
@@ -875,18 +811,8 @@ impl DiagCtxt {
     // FIXME: This method should be removed (every error should have an associated error code).
     #[rustc_lint_diagnostics]
     #[track_caller]
-    pub fn struct_err(
-        &self,
-        msg: impl Into<DiagnosticMessage>,
-    ) -> DiagnosticBuilder<'_, ErrorGuaranteed> {
-        DiagnosticBuilder::new(self, Level::Error { lint: false }, msg)
-    }
-
-    /// This should only be used by `rustc_middle::lint::struct_lint_level`. Do not use it for hard errors.
-    #[doc(hidden)]
-    #[track_caller]
-    pub fn struct_err_lint(&self, msg: impl Into<DiagnosticMessage>) -> DiagnosticBuilder<'_, ()> {
-        DiagnosticBuilder::new(self, Level::Error { lint: true }, msg)
+    pub fn struct_err(&self, msg: impl Into<DiagnosticMessage>) -> DiagnosticBuilder<'_> {
+        DiagnosticBuilder::new(self, Error { lint: false }, msg)
     }
 
     /// Construct a builder at the `Error` level with the `msg` and the `code`.
@@ -896,7 +822,7 @@ impl DiagCtxt {
         &self,
         msg: impl Into<DiagnosticMessage>,
         code: DiagnosticId,
-    ) -> DiagnosticBuilder<'_, ErrorGuaranteed> {
+    ) -> DiagnosticBuilder<'_> {
         let mut result = self.struct_err(msg);
         result.code(code);
         result
@@ -922,7 +848,7 @@ impl DiagCtxt {
         &self,
         span: impl Into<MultiSpan>,
         msg: impl Into<DiagnosticMessage>,
-    ) -> DiagnosticBuilder<'_, !> {
+    ) -> DiagnosticBuilder<'_, FatalAbort> {
         let mut result = self.struct_fatal(msg);
         result.set_span(span);
         result
@@ -936,7 +862,7 @@ impl DiagCtxt {
         span: impl Into<MultiSpan>,
         msg: impl Into<DiagnosticMessage>,
         code: DiagnosticId,
-    ) -> DiagnosticBuilder<'_, !> {
+    ) -> DiagnosticBuilder<'_, FatalAbort> {
         let mut result = self.struct_span_fatal(span, msg);
         result.code(code);
         result
@@ -945,8 +871,11 @@ impl DiagCtxt {
     /// Construct a builder at the `Fatal` level with the `msg`.
     #[rustc_lint_diagnostics]
     #[track_caller]
-    pub fn struct_fatal(&self, msg: impl Into<DiagnosticMessage>) -> DiagnosticBuilder<'_, !> {
-        DiagnosticBuilder::new(self, Level::Fatal, msg)
+    pub fn struct_fatal(
+        &self,
+        msg: impl Into<DiagnosticMessage>,
+    ) -> DiagnosticBuilder<'_, FatalAbort> {
+        DiagnosticBuilder::new(self, Fatal, msg)
     }
 
     /// Construct a builder at the `Fatal` level with the `msg`, that doesn't abort.
@@ -956,20 +885,40 @@ impl DiagCtxt {
         &self,
         msg: impl Into<DiagnosticMessage>,
     ) -> DiagnosticBuilder<'_, FatalError> {
-        DiagnosticBuilder::new(self, Level::Fatal, msg)
+        DiagnosticBuilder::new(self, Fatal, msg)
     }
 
     /// Construct a builder at the `Help` level with the `msg`.
     #[rustc_lint_diagnostics]
     pub fn struct_help(&self, msg: impl Into<DiagnosticMessage>) -> DiagnosticBuilder<'_, ()> {
-        DiagnosticBuilder::new(self, Level::Help, msg)
+        DiagnosticBuilder::new(self, Help, msg)
     }
 
     /// Construct a builder at the `Note` level with the `msg`.
     #[rustc_lint_diagnostics]
     #[track_caller]
     pub fn struct_note(&self, msg: impl Into<DiagnosticMessage>) -> DiagnosticBuilder<'_, ()> {
-        DiagnosticBuilder::new(self, Level::Note, msg)
+        DiagnosticBuilder::new(self, Note, msg)
+    }
+
+    /// Construct a builder at the `Bug` level with the `msg`.
+    #[rustc_lint_diagnostics]
+    #[track_caller]
+    pub fn struct_bug(&self, msg: impl Into<DiagnosticMessage>) -> DiagnosticBuilder<'_, BugAbort> {
+        DiagnosticBuilder::new(self, Bug, msg)
+    }
+
+    /// Construct a builder at the `Bug` level at the given `span` with the `msg`.
+    #[rustc_lint_diagnostics]
+    #[track_caller]
+    pub fn struct_span_bug(
+        &self,
+        span: impl Into<MultiSpan>,
+        msg: impl Into<DiagnosticMessage>,
+    ) -> DiagnosticBuilder<'_, BugAbort> {
+        let mut result = self.struct_bug(msg);
+        result.set_span(span);
+        result
     }
 
     #[rustc_lint_diagnostics]
@@ -1028,7 +977,7 @@ impl DiagCtxt {
     }
 
     pub fn span_bug(&self, span: impl Into<MultiSpan>, msg: impl Into<DiagnosticMessage>) -> ! {
-        self.inner.borrow_mut().span_bug(span, msg)
+        self.struct_span_bug(span, msg).emit()
     }
 
     /// For documentation on this, see `Session::span_delayed_bug`.
@@ -1041,20 +990,14 @@ impl DiagCtxt {
         sp: impl Into<MultiSpan>,
         msg: impl Into<DiagnosticMessage>,
     ) -> ErrorGuaranteed {
-        let mut inner = self.inner.borrow_mut();
-
-        // This is technically `self.treat_err_as_bug()` but `span_delayed_bug` is called before
-        // incrementing `err_count` by one, so we need to +1 the comparing.
-        // FIXME: Would be nice to increment err_count in a more coherent way.
-        if inner.flags.treat_err_as_bug.is_some_and(|c| {
-            inner.err_count + inner.lint_err_count + inner.delayed_bug_count() + 1 >= c.get()
-        }) {
+        let treat_next_err_as_bug = self.inner.borrow().treat_next_err_as_bug();
+        if treat_next_err_as_bug {
             // FIXME: don't abort here if report_delayed_bugs is off
-            inner.span_bug(sp, msg);
+            self.span_bug(sp, msg);
         }
-        let mut diagnostic = Diagnostic::new(Level::DelayedBug, msg);
+        let mut diagnostic = Diagnostic::new(DelayedBug, msg);
         diagnostic.set_span(sp);
-        inner.emit_diagnostic(diagnostic).unwrap()
+        self.emit_diagnostic(diagnostic).unwrap()
     }
 
     // FIXME(eddyb) note the comment inside `impl Drop for DiagCtxtInner`, that's
@@ -1062,7 +1005,7 @@ impl DiagCtxt {
     pub fn good_path_delayed_bug(&self, msg: impl Into<DiagnosticMessage>) {
         let mut inner = self.inner.borrow_mut();
 
-        let mut diagnostic = Diagnostic::new(Level::DelayedBug, msg);
+        let mut diagnostic = Diagnostic::new(DelayedBug, msg);
         if inner.flags.report_delayed_bugs {
             inner.emit_diagnostic_without_consuming(&mut diagnostic);
         }
@@ -1070,13 +1013,6 @@ impl DiagCtxt {
         inner.good_path_delayed_bugs.push(DelayedDiagnostic::with_backtrace(diagnostic, backtrace));
     }
 
-    #[track_caller]
-    pub fn span_bug_no_panic(&self, span: impl Into<MultiSpan>, msg: impl Into<DiagnosticMessage>) {
-        let mut diag = Diagnostic::new(Bug, msg);
-        diag.set_span(span);
-        self.emit_diagnostic(diag);
-    }
-
     #[track_caller]
     #[rustc_lint_diagnostics]
     pub fn span_note(&self, span: impl Into<MultiSpan>, msg: impl Into<DiagnosticMessage>) {
@@ -1115,9 +1051,9 @@ impl DiagCtxt {
         self.struct_note(msg).emit()
     }
 
+    #[rustc_lint_diagnostics]
     pub fn bug(&self, msg: impl Into<DiagnosticMessage>) -> ! {
-        DiagnosticBuilder::<diagnostic_builder::Bug>::new(self, Bug, msg).emit();
-        panic::panic_any(ExplicitBug);
+        self.struct_bug(msg).emit()
     }
 
     #[inline]
@@ -1182,10 +1118,9 @@ impl DiagCtxt {
 
         match (errors.len(), warnings.len()) {
             (0, 0) => return,
-            (0, _) => inner.emitter.emit_diagnostic(&Diagnostic::new(
-                Level::Warning(None),
-                DiagnosticMessage::Str(warnings),
-            )),
+            (0, _) => inner
+                .emitter
+                .emit_diagnostic(&Diagnostic::new(Warning(None), DiagnosticMessage::Str(warnings))),
             (_, 0) => {
                 inner.emit_diagnostic(Diagnostic::new(Fatal, errors));
             }
@@ -1217,14 +1152,12 @@ impl DiagCtxt {
                         if error_codes.len() > 9 { "..." } else { "." }
                     ));
                     inner.failure_note(format!(
-                        "For more information about an error, try \
-                         `rustc --explain {}`.",
+                        "For more information about an error, try `rustc --explain {}`.",
                         &error_codes[0]
                     ));
                 } else {
                     inner.failure_note(format!(
-                        "For more information about this error, try \
-                         `rustc --explain {}`.",
+                        "For more information about this error, try `rustc --explain {}`.",
                         &error_codes[0]
                     ));
                 }
@@ -1274,18 +1207,16 @@ impl DiagCtxt {
         self.create_err(err).emit()
     }
 
-    pub fn create_err<'a>(
-        &'a self,
-        err: impl IntoDiagnostic<'a>,
-    ) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
-        err.into_diagnostic(self)
+    #[track_caller]
+    pub fn create_err<'a>(&'a self, err: impl IntoDiagnostic<'a>) -> DiagnosticBuilder<'a> {
+        err.into_diagnostic(self, Error { lint: false })
     }
 
     pub fn create_warning<'a>(
         &'a self,
         warning: impl IntoDiagnostic<'a, ()>,
     ) -> DiagnosticBuilder<'a, ()> {
-        warning.into_diagnostic(self)
+        warning.into_diagnostic(self, Warning(None))
     }
 
     pub fn emit_warning<'a>(&'a self, warning: impl IntoDiagnostic<'a, ()>) {
@@ -1296,7 +1227,7 @@ impl DiagCtxt {
         &'a self,
         fatal: impl IntoDiagnostic<'a, FatalError>,
     ) -> DiagnosticBuilder<'a, FatalError> {
-        fatal.into_diagnostic(self)
+        fatal.into_diagnostic(self, Fatal)
     }
 
     pub fn emit_almost_fatal<'a>(
@@ -1308,38 +1239,35 @@ impl DiagCtxt {
 
     pub fn create_fatal<'a>(
         &'a self,
-        fatal: impl IntoDiagnostic<'a, !>,
-    ) -> DiagnosticBuilder<'a, !> {
-        fatal.into_diagnostic(self)
+        fatal: impl IntoDiagnostic<'a, FatalAbort>,
+    ) -> DiagnosticBuilder<'a, FatalAbort> {
+        fatal.into_diagnostic(self, Fatal)
     }
 
-    pub fn emit_fatal<'a>(&'a self, fatal: impl IntoDiagnostic<'a, !>) -> ! {
+    pub fn emit_fatal<'a>(&'a self, fatal: impl IntoDiagnostic<'a, FatalAbort>) -> ! {
         self.create_fatal(fatal).emit()
     }
 
     pub fn create_bug<'a>(
         &'a self,
-        bug: impl IntoDiagnostic<'a, diagnostic_builder::Bug>,
-    ) -> DiagnosticBuilder<'a, diagnostic_builder::Bug> {
-        bug.into_diagnostic(self)
+        bug: impl IntoDiagnostic<'a, BugAbort>,
+    ) -> DiagnosticBuilder<'a, BugAbort> {
+        bug.into_diagnostic(self, Bug)
     }
 
-    pub fn emit_bug<'a>(
-        &'a self,
-        bug: impl IntoDiagnostic<'a, diagnostic_builder::Bug>,
-    ) -> diagnostic_builder::Bug {
+    pub fn emit_bug<'a>(&'a self, bug: impl IntoDiagnostic<'a, BugAbort>) -> ! {
         self.create_bug(bug).emit()
     }
 
-    pub fn emit_note<'a>(&'a self, note: impl IntoDiagnostic<'a, Noted>) -> Noted {
+    pub fn emit_note<'a>(&'a self, note: impl IntoDiagnostic<'a, ()>) {
         self.create_note(note).emit()
     }
 
     pub fn create_note<'a>(
         &'a self,
-        note: impl IntoDiagnostic<'a, Noted>,
-    ) -> DiagnosticBuilder<'a, Noted> {
-        note.into_diagnostic(self)
+        note: impl IntoDiagnostic<'a, ()>,
+    ) -> DiagnosticBuilder<'a, ()> {
+        note.into_diagnostic(self, Note)
     }
 
     pub fn emit_artifact_notification(&self, path: &Path, artifact_type: &str) {
@@ -1426,7 +1354,7 @@ impl DiagCtxtInner {
         for diag in diags {
             // Decrement the count tracking the stash; emitting will increment it.
             if diag.is_error() {
-                if matches!(diag.level, Level::Error { lint: true }) {
+                if matches!(diag.level, Error { lint: true }) {
                     self.lint_err_count -= 1;
                 } else {
                     self.err_count -= 1;
@@ -1457,9 +1385,8 @@ impl DiagCtxtInner {
         &mut self,
         diagnostic: &mut Diagnostic,
     ) -> Option<ErrorGuaranteed> {
-        if matches!(diagnostic.level, Level::Error { .. } | Level::Fatal) && self.treat_err_as_bug()
-        {
-            diagnostic.level = Level::Bug;
+        if matches!(diagnostic.level, Error { .. } | Fatal) && self.treat_err_as_bug() {
+            diagnostic.level = Bug;
         }
 
         // The `LintExpectationId` can be stable or unstable depending on when it was created.
@@ -1471,7 +1398,7 @@ impl DiagCtxtInner {
             return None;
         }
 
-        if diagnostic.level == Level::DelayedBug {
+        if diagnostic.level == DelayedBug {
             // FIXME(eddyb) this should check for `has_errors` and stop pushing
             // once *any* errors were emitted (and truncate `span_delayed_bugs`
             // when an error is first emitted, also), but maybe there's a case
@@ -1487,7 +1414,7 @@ impl DiagCtxtInner {
         }
 
         if diagnostic.has_future_breakage() {
-            // Future breakages aren't emitted if they're Level::Allowed,
+            // Future breakages aren't emitted if they're Level::Allow,
             // but they still need to be constructed and stashed below,
             // so they'll trigger the good-path bug check.
             self.suppressed_expected_diag = true;
@@ -1509,7 +1436,7 @@ impl DiagCtxtInner {
             return None;
         }
 
-        if matches!(diagnostic.level, Level::Expect(_) | Level::Allow) {
+        if matches!(diagnostic.level, Expect(_) | Allow) {
             (*TRACK_DIAGNOSTICS)(diagnostic, &mut |_| {});
             return None;
         }
@@ -1534,7 +1461,7 @@ impl DiagCtxtInner {
                 debug!(?self.emitted_diagnostics);
                 let already_emitted_sub = |sub: &mut SubDiagnostic| {
                     debug!(?sub);
-                    if sub.level != Level::OnceNote && sub.level != Level::OnceHelp {
+                    if sub.level != OnceNote && sub.level != OnceHelp {
                         return false;
                     }
                     let mut hasher = StableHasher::new();
@@ -1559,7 +1486,7 @@ impl DiagCtxtInner {
                 }
             }
             if diagnostic.is_error() {
-                if matches!(diagnostic.level, Level::Error { lint: true }) {
+                if matches!(diagnostic.level, Error { lint: true }) {
                     self.bump_lint_err_count();
                 } else {
                     self.bump_err_count();
@@ -1583,6 +1510,13 @@ impl DiagCtxtInner {
         })
     }
 
+    // Use this one before incrementing `err_count`.
+    fn treat_next_err_as_bug(&self) -> bool {
+        self.flags.treat_err_as_bug.is_some_and(|c| {
+            self.err_count + self.lint_err_count + self.delayed_bug_count() + 1 >= c.get()
+        })
+    }
+
     fn delayed_bug_count(&self) -> usize {
         self.span_delayed_bugs.len() + self.good_path_delayed_bugs.len()
     }
@@ -1591,27 +1525,22 @@ impl DiagCtxtInner {
         self.err_count > 0
     }
 
-    #[track_caller]
-    fn span_bug(&mut self, sp: impl Into<MultiSpan>, msg: impl Into<DiagnosticMessage>) -> ! {
-        let mut diag = Diagnostic::new(Bug, msg);
-        diag.set_span(sp);
-        self.emit_diagnostic(diag);
-        panic::panic_any(ExplicitBug);
-    }
-
     fn failure_note(&mut self, msg: impl Into<DiagnosticMessage>) {
         self.emit_diagnostic(Diagnostic::new(FailureNote, msg));
     }
 
     fn flush_delayed(
         &mut self,
-        bugs: impl IntoIterator<Item = DelayedDiagnostic>,
+        bugs: Vec<DelayedDiagnostic>,
         explanation: impl Into<DiagnosticMessage> + Copy,
     ) {
-        let mut no_bugs = true;
+        if bugs.is_empty() {
+            return;
+        }
+
         // If backtraces are enabled, also print the query stack
         let backtrace = std::env::var_os("RUST_BACKTRACE").map_or(true, |x| &x != "0");
-        for bug in bugs {
+        for (i, bug) in bugs.into_iter().enumerate() {
             if let Some(file) = self.ice_file.as_ref()
                 && let Ok(mut out) = std::fs::File::options().create(true).append(true).open(file)
             {
@@ -1619,25 +1548,25 @@ impl DiagCtxtInner {
                     &mut out,
                     "delayed span bug: {}\n{}\n",
                     bug.inner
-                        .styled_message()
+                        .messages()
                         .iter()
                         .filter_map(|(msg, _)| msg.as_str())
                         .collect::<String>(),
                     &bug.note
                 );
             }
-            let mut bug =
-                if backtrace || self.ice_file.is_none() { bug.decorate() } else { bug.inner };
 
-            if no_bugs {
+            if i == 0 {
                 // Put the overall explanation before the `DelayedBug`s, to
                 // frame them better (e.g. separate warnings from them).
                 self.emit_diagnostic(Diagnostic::new(Bug, explanation));
-                no_bugs = false;
             }
 
+            let mut bug =
+                if backtrace || self.ice_file.is_none() { bug.decorate() } else { bug.inner };
+
             // "Undelay" the `DelayedBug`s (into plain `Bug`s).
-            if bug.level != Level::DelayedBug {
+            if bug.level != DelayedBug {
                 // NOTE(eddyb) not panicking here because we're already producing
                 // an ICE, and the more information the merrier.
                 bug.subdiagnostic(InvalidFlushedDelayedDiagnosticLevel {
@@ -1645,15 +1574,13 @@ impl DiagCtxtInner {
                     level: bug.level,
                 });
             }
-            bug.level = Level::Bug;
+            bug.level = Bug;
 
             self.emit_diagnostic(bug);
         }
 
         // Panic with `DelayedBugPanic` to avoid "unexpected panic" messages.
-        if !no_bugs {
-            panic::panic_any(DelayedBugPanic);
-        }
+        panic::panic_any(DelayedBugPanic);
     }
 
     fn bump_lint_err_count(&mut self) {
@@ -1731,25 +1658,80 @@ impl DelayedDiagnostic {
 
 #[derive(Copy, PartialEq, Eq, Clone, Hash, Debug, Encodable, Decodable)]
 pub enum Level {
+    /// For bugs in the compiler. Manifests as an ICE (internal compiler error) panic.
+    ///
+    /// Its `EmissionGuarantee` is `BugAbort`.
     Bug,
+
+    /// This is a strange one: lets you register an error without emitting it. If compilation ends
+    /// without any other errors occurring, this will be emitted as a bug. Otherwise, it will be
+    /// silently dropped. I.e. "expect other errors are emitted" semantics. Useful on code paths
+    /// that should only be reached when compiling erroneous code.
+    ///
+    /// Its `EmissionGuarantee` is `ErrorGuaranteed`.
     DelayedBug,
+
+    /// An error that causes an immediate abort. Used for things like configuration errors,
+    /// internal overflows, some file operation errors.
+    ///
+    /// Its `EmissionGuarantee` is `FatalAbort`, except in the non-aborting "almost fatal" case
+    /// that is occasionaly used, where it is `FatalError`.
     Fatal,
+
+    /// An error in the code being compiled, which prevents compilation from finishing. This is the
+    /// most common case.
+    ///
+    /// Its `EmissionGuarantee` is `ErrorGuaranteed`.
     Error {
-        /// If this error comes from a lint, don't abort compilation even when abort_if_errors() is called.
+        /// If this error comes from a lint, don't abort compilation even when abort_if_errors() is
+        /// called.
         lint: bool,
     },
+
+    /// A warning about the code being compiled. Does not prevent compilation from finishing.
+    ///
     /// This [`LintExpectationId`] is used for expected lint diagnostics, which should
     /// also emit a warning due to the `force-warn` flag. In all other cases this should
     /// be `None`.
+    ///
+    /// Its `EmissionGuarantee` is `()`.
     Warning(Option<LintExpectationId>),
+
+    /// A message giving additional context. Rare, because notes are more commonly attached to other
+    /// diagnostics such as errors.
+    ///
+    /// Its `EmissionGuarantee` is `()`.
     Note,
-    /// A note that is only emitted once.
+
+    /// A note that is only emitted once. Rare, mostly used in circumstances relating to lints.
+    ///
+    /// Its `EmissionGuarantee` is `()`.
     OnceNote,
+
+    /// A message suggesting how to fix something. Rare, because help messages are more commonly
+    /// attached to other diagnostics such as errors.
+    ///
+    /// Its `EmissionGuarantee` is `()`.
     Help,
-    /// A help that is only emitted once.
+
+    /// A help that is only emitted once. Rare.
+    ///
+    /// Its `EmissionGuarantee` is `()`.
     OnceHelp,
+
+    /// Similar to `Note`, but used in cases where compilation has failed. Rare.
+    ///
+    /// Its `EmissionGuarantee` is `()`.
     FailureNote,
+
+    /// Only used for lints.
+    ///
+    /// Its `EmissionGuarantee` is `()`.
     Allow,
+
+    /// Only used for lints.
+    ///
+    /// Its `EmissionGuarantee` is `()`.
     Expect(LintExpectationId),
 }
 
@@ -1789,8 +1771,7 @@ impl Level {
             Note | OnceNote => "note",
             Help | OnceHelp => "help",
             FailureNote => "failure-note",
-            Allow => panic!("Shouldn't call on allowed error"),
-            Expect(_) => panic!("Shouldn't call on expected error"),
+            Allow | Expect(_) => unreachable!(),
         }
     }
 
@@ -1800,7 +1781,7 @@ impl Level {
 
     pub fn get_expectation_id(&self) -> Option<LintExpectationId> {
         match self {
-            Level::Expect(id) | Level::Warning(Some(id)) => Some(*id),
+            Expect(id) | Warning(Some(id)) => Some(*id),
             _ => None,
         }
     }

compiler/rustc_expand/src/base.rs

@@ -1118,15 +1118,12 @@ impl<'a> ExtCtxt<'a> {
         &self,
         sp: S,
         msg: impl Into<DiagnosticMessage>,
-    ) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
+    ) -> DiagnosticBuilder<'a> {
         self.sess.dcx().struct_span_err(sp, msg)
     }
 
     #[track_caller]
-    pub fn create_err(
-        &self,
-        err: impl IntoDiagnostic<'a>,
-    ) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
+    pub fn create_err(&self, err: impl IntoDiagnostic<'a>) -> DiagnosticBuilder<'a> {
         self.sess.create_err(err)
     }
 
@@ -1159,6 +1156,7 @@ impl<'a> ExtCtxt<'a> {
         // Fixme: does this result in errors?
         self.expansions.clear();
     }
+    #[rustc_lint_diagnostics]
     pub fn bug(&self, msg: &'static str) -> ! {
         self.sess.dcx().bug(msg);
     }
@@ -1204,11 +1202,10 @@ pub fn resolve_path(
                 .expect("attempting to resolve a file path in an external file"),
             FileName::DocTest(path, _) => path,
             other => {
-                return Err(errors::ResolveRelativePath {
+                return Err(parse_sess.dcx.create_err(errors::ResolveRelativePath {
                     span,
                     path: parse_sess.source_map().filename_for_diagnostics(&other).to_string(),
-                }
-                .into_diagnostic(&parse_sess.dcx));
+                }));
             }
         };
         result.pop();
@@ -1230,7 +1227,7 @@ pub fn expr_to_spanned_string<'a>(
     cx: &'a mut ExtCtxt<'_>,
     expr: P<ast::Expr>,
     err_msg: &'static str,
-) -> Result<(Symbol, ast::StrStyle, Span), Option<(DiagnosticBuilder<'a, ErrorGuaranteed>, bool)>> {
+) -> Result<(Symbol, ast::StrStyle, Span), Option<(DiagnosticBuilder<'a>, bool)>> {
     // Perform eager expansion on the expression.
     // We want to be able to handle e.g., `concat!("foo", "bar")`.
     let expr = cx.expander().fully_expand_fragment(AstFragment::Expr(expr)).make_expr();

compiler/rustc_expand/src/build.rs

@@ -134,10 +134,13 @@ impl<'a> ExtCtxt<'a> {
     pub fn trait_bound(&self, path: ast::Path, is_const: bool) -> ast::GenericBound {
         ast::GenericBound::Trait(
             self.poly_trait_ref(path.span, path),
-            if is_const {
-                ast::TraitBoundModifier::MaybeConst(DUMMY_SP)
-            } else {
-                ast::TraitBoundModifier::None
+            ast::TraitBoundModifiers {
+                polarity: ast::BoundPolarity::Positive,
+                constness: if is_const {
+                    ast::BoundConstness::Maybe(DUMMY_SP)
+                } else {
+                    ast::BoundConstness::Never
+                },
             },
         )
     }
@@ -488,7 +491,7 @@ impl<'a> ExtCtxt<'a> {
         path: ast::Path,
         field_pats: ThinVec<ast::PatField>,
     ) -> P<ast::Pat> {
-        self.pat(span, PatKind::Struct(None, path, field_pats, false))
+        self.pat(span, PatKind::Struct(None, path, field_pats, ast::PatFieldsRest::None))
     }
     pub fn pat_tuple(&self, span: Span, pats: ThinVec<P<ast::Pat>>) -> P<ast::Pat> {
         self.pat(span, PatKind::Tuple(pats))

compiler/rustc_expand/src/expand.rs

@@ -41,132 +41,6 @@ use std::path::PathBuf;
 use std::rc::Rc;
 use std::{iter, mem};
 
-#[cfg(bootstrap)]
-macro_rules! ast_fragments {
-    (
-        $($Kind:ident($AstTy:ty) {
-            $kind_name:expr;
-            $(one fn $mut_visit_ast:ident; fn $visit_ast:ident;)?
-            $(many fn $flat_map_ast_elt:ident; fn $visit_ast_elt:ident($($args:tt)*);)?
-            fn $make_ast:ident;
-        })*
-    ) => {
-        /// A fragment of AST that can be produced by a single macro expansion.
-        /// Can also serve as an input and intermediate result for macro expansion operations.
-        pub enum AstFragment {
-            OptExpr(Option<P<ast::Expr>>),
-            MethodReceiverExpr(P<ast::Expr>),
-            $($Kind($AstTy),)*
-        }
-
-        /// "Discriminant" of an AST fragment.
-        #[derive(Copy, Clone, PartialEq, Eq)]
-        pub enum AstFragmentKind {
-            OptExpr,
-            MethodReceiverExpr,
-            $($Kind,)*
-        }
-
-        impl AstFragmentKind {
-            pub fn name(self) -> &'static str {
-                match self {
-                    AstFragmentKind::OptExpr => "expression",
-                    AstFragmentKind::MethodReceiverExpr => "expression",
-                    $(AstFragmentKind::$Kind => $kind_name,)*
-                }
-            }
-
-            fn make_from<'a>(self, result: Box<dyn MacResult + 'a>) -> Option<AstFragment> {
-                match self {
-                    AstFragmentKind::OptExpr =>
-                        result.make_expr().map(Some).map(AstFragment::OptExpr),
-                    AstFragmentKind::MethodReceiverExpr =>
-                        result.make_expr().map(AstFragment::MethodReceiverExpr),
-                    $(AstFragmentKind::$Kind => result.$make_ast().map(AstFragment::$Kind),)*
-                }
-            }
-        }
-
-        impl AstFragment {
-            pub fn add_placeholders(&mut self, placeholders: &[NodeId]) {
-                if placeholders.is_empty() {
-                    return;
-                }
-                match self {
-                    $($(AstFragment::$Kind(ast) => ast.extend(placeholders.iter().flat_map(|id| {
-                        ${ignore(flat_map_ast_elt)}
-                        placeholder(AstFragmentKind::$Kind, *id, None).$make_ast()
-                    })),)?)*
-                    _ => panic!("unexpected AST fragment kind")
-                }
-            }
-
-            pub fn make_opt_expr(self) -> Option<P<ast::Expr>> {
-                match self {
-                    AstFragment::OptExpr(expr) => expr,
-                    _ => panic!("AstFragment::make_* called on the wrong kind of fragment"),
-                }
-            }
-
-            pub fn make_method_receiver_expr(self) -> P<ast::Expr> {
-                match self {
-                    AstFragment::MethodReceiverExpr(expr) => expr,
-                    _ => panic!("AstFragment::make_* called on the wrong kind of fragment"),
-                }
-            }
-
-            $(pub fn $make_ast(self) -> $AstTy {
-                match self {
-                    AstFragment::$Kind(ast) => ast,
-                    _ => panic!("AstFragment::make_* called on the wrong kind of fragment"),
-                }
-            })*
-
-            fn make_ast<T: InvocationCollectorNode>(self) -> T::OutputTy {
-                T::fragment_to_output(self)
-            }
-
-            pub fn mut_visit_with<F: MutVisitor>(&mut self, vis: &mut F) {
-                match self {
-                    AstFragment::OptExpr(opt_expr) => {
-                        visit_clobber(opt_expr, |opt_expr| {
-                            if let Some(expr) = opt_expr {
-                                vis.filter_map_expr(expr)
-                            } else {
-                                None
-                            }
-                        });
-                    }
-                    AstFragment::MethodReceiverExpr(expr) => vis.visit_method_receiver_expr(expr),
-                    $($(AstFragment::$Kind(ast) => vis.$mut_visit_ast(ast),)?)*
-                    $($(AstFragment::$Kind(ast) =>
-                        ast.flat_map_in_place(|ast| vis.$flat_map_ast_elt(ast)),)?)*
-                }
-            }
-
-            pub fn visit_with<'a, V: Visitor<'a>>(&'a self, visitor: &mut V) {
-                match self {
-                    AstFragment::OptExpr(Some(expr)) => visitor.visit_expr(expr),
-                    AstFragment::OptExpr(None) => {}
-                    AstFragment::MethodReceiverExpr(expr) => visitor.visit_method_receiver_expr(expr),
-                    $($(AstFragment::$Kind(ast) => visitor.$visit_ast(ast),)?)*
-                    $($(AstFragment::$Kind(ast) => for ast_elt in &ast[..] {
-                        visitor.$visit_ast_elt(ast_elt, $($args)*);
-                    })?)*
-                }
-            }
-        }
-
-        impl<'a> MacResult for crate::mbe::macro_rules::ParserAnyMacro<'a> {
-            $(fn $make_ast(self: Box<crate::mbe::macro_rules::ParserAnyMacro<'a>>)
-                           -> Option<$AstTy> {
-                Some(self.make(AstFragmentKind::$Kind).$make_ast())
-            })*
-        }
-    }
-}
-
-#[cfg(not(bootstrap))]
 macro_rules! ast_fragments {
     (
         $($Kind:ident($AstTy:ty) {

compiler/rustc_expand/src/mbe/diagnostics.rs

@@ -215,7 +215,7 @@ impl<'matcher> Tracker<'matcher> for FailureForwarder {
 }
 
 pub(super) fn emit_frag_parse_err(
-    mut e: DiagnosticBuilder<'_, rustc_errors::ErrorGuaranteed>,
+    mut e: DiagnosticBuilder<'_>,
     parser: &Parser<'_>,
     orig_parser: &mut Parser<'_>,
     site_span: Span,
@@ -224,11 +224,11 @@ pub(super) fn emit_frag_parse_err(
 ) {
     // FIXME(davidtwco): avoid depending on the error message text
     if parser.token == token::Eof
-        && let DiagnosticMessage::Str(message) = &e.message[0].0
+        && let DiagnosticMessage::Str(message) = &e.messages[0].0
         && message.ends_with(", found `<eof>`")
     {
-        let msg = &e.message[0];
-        e.message[0] = (
+        let msg = &e.messages[0];
+        e.messages[0] = (
             DiagnosticMessage::from(format!(
                 "macro expansion ends with an incomplete expression: {}",
                 message.replace(", found `<eof>`", ""),

compiler/rustc_expand/src/mbe/transcribe.rs

@@ -9,8 +9,8 @@ use rustc_ast::mut_visit::{self, MutVisitor};
 use rustc_ast::token::{self, Delimiter, Token, TokenKind};
 use rustc_ast::tokenstream::{DelimSpacing, DelimSpan, Spacing, TokenStream, TokenTree};
 use rustc_data_structures::fx::FxHashMap;
+use rustc_errors::DiagnosticBuilder;
 use rustc_errors::{pluralize, PResult};
-use rustc_errors::{DiagnosticBuilder, ErrorGuaranteed};
 use rustc_span::hygiene::{LocalExpnId, Transparency};
 use rustc_span::symbol::{sym, Ident, MacroRulesNormalizedIdent};
 use rustc_span::Span;
@@ -528,7 +528,7 @@ fn out_of_bounds_err<'a>(
     max: usize,
     span: Span,
     ty: &str,
-) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
+) -> DiagnosticBuilder<'a> {
     let msg = if max == 0 {
         format!(
             "meta-variable expression `{ty}` with depth parameter \

compiler/rustc_expand/src/module.rs

@@ -43,7 +43,7 @@ pub enum ModError<'a> {
     ModInBlock(Option<Ident>),
     FileNotFound(Ident, PathBuf, PathBuf),
     MultipleCandidates(Ident, PathBuf, PathBuf),
-    ParserError(DiagnosticBuilder<'a, ErrorGuaranteed>),
+    ParserError(DiagnosticBuilder<'a>),
 }
 
 pub(crate) fn parse_external_mod(

compiler/rustc_expand/src/proc_macro_server.rs

@@ -499,12 +499,7 @@ impl server::FreeFunctions for Rustc<'_, '_> {
             rustc_errors::Diagnostic::new(diagnostic.level.to_internal(), diagnostic.message);
         diag.set_span(MultiSpan::from_spans(diagnostic.spans));
         for child in diagnostic.children {
-            diag.sub(
-                child.level.to_internal(),
-                child.message,
-                MultiSpan::from_spans(child.spans),
-                None,
-            );
+            diag.sub(child.level.to_internal(), child.message, MultiSpan::from_spans(child.spans));
         }
         self.sess().dcx.emit_diagnostic(diag);
     }

compiler/rustc_feature/src/accepted.rs

@@ -77,7 +77,7 @@ declare_features! (
     /// Allows empty structs and enum variants with braces.
     (accepted, braced_empty_structs, "1.8.0", Some(29720)),
     /// Allows `c"foo"` literals.
-    (accepted, c_str_literals, "CURRENT_RUSTC_VERSION", Some(105723)),
+    (accepted, c_str_literals, "1.76.0", Some(105723)),
     /// Allows `#[cfg_attr(predicate, multiple, attributes, here)]`.
     (accepted, cfg_attr_multi, "1.33.0", Some(54881)),
     /// Allows the use of `#[cfg(doctest)]`, set when rustdoc is collecting doctests.
@@ -341,7 +341,7 @@ declare_features! (
     (accepted, track_caller, "1.46.0", Some(47809)),
     /// Allows dyn upcasting trait objects via supertraits.
     /// Dyn upcasting is casting, e.g., `dyn Foo -> dyn Bar` where `Foo: Bar`.
-    (accepted, trait_upcasting, "CURRENT_RUSTC_VERSION", Some(65991)),
+    (accepted, trait_upcasting, "1.76.0", Some(65991)),
     /// Allows #[repr(transparent)] on univariant enums (RFC 2645).
     (accepted, transparent_enums, "1.42.0", Some(60405)),
     /// Allows indexing tuples.

compiler/rustc_feature/src/removed.rs

@@ -177,7 +177,7 @@ declare_features! (
     /// Allows using the `#[register_attr]` attribute.
     (removed, register_attr, "1.65.0", Some(66080),
      Some("removed in favor of `#![register_tool]`")),
-    (removed, rust_2018_preview, "CURRENT_RUSTC_VERSION", None,
+    (removed, rust_2018_preview, "1.76.0", None,
      Some("2018 Edition preview is no longer relevant")),
     /// Allows using the macros:
     /// + `__diagnostic_used`

compiler/rustc_feature/src/unstable.rs

@@ -204,7 +204,7 @@ declare_features! (
     /// Allows using `#[lang = ".."]` attribute for linking items to special compiler logic.
     (internal, lang_items, "1.0.0", None),
     /// Changes `impl Trait` to capture all lifetimes in scope.
-    (unstable, lifetime_capture_rules_2024, "CURRENT_RUSTC_VERSION", None),
+    (unstable, lifetime_capture_rules_2024, "1.76.0", None),
     /// Allows `#[link(..., cfg(..))]`; perma-unstable per #37406
     (unstable, link_cfg, "1.14.0", None),
     /// Allows the `multiple_supertrait_upcastable` lint.
@@ -357,6 +357,8 @@ declare_features! (
     (unstable, async_closure, "1.37.0", Some(62290)),
     /// Allows `#[track_caller]` on async functions.
     (unstable, async_fn_track_caller, "1.73.0", Some(110011)),
+    /// Allows `for await` loops.
+    (unstable, async_for_loop, "CURRENT_RUSTC_VERSION", Some(118898)),
     /// Allows builtin # foo() syntax
     (unstable, builtin_syntax, "1.71.0", Some(110680)),
     /// Treat `extern "C"` function as nounwind.
@@ -468,7 +470,7 @@ declare_features! (
     /// Allows using `#[repr(align(...))]` on function items
     (unstable, fn_align, "1.53.0", Some(82232)),
     /// Support delegating implementation of functions to other already implemented functions.
-    (incomplete, fn_delegation, "CURRENT_RUSTC_VERSION", Some(118212)),
+    (incomplete, fn_delegation, "1.76.0", Some(118212)),
     /// Allows defining gen blocks and `gen fn`.
     (unstable, gen_blocks, "1.75.0", Some(117078)),
     /// Infer generic args for both consts and types.
@@ -505,7 +507,7 @@ declare_features! (
     (unstable, let_chains, "1.37.0", Some(53667)),
     /// Allows using `#[link(kind = "link-arg", name = "...")]`
     /// to pass custom arguments to the linker.
-    (unstable, link_arg_attribute, "CURRENT_RUSTC_VERSION", Some(99427)),
+    (unstable, link_arg_attribute, "1.76.0", Some(99427)),
     /// Allows using `reason` in lint attributes and the `#[expect(lint)]` lint check.
     (unstable, lint_reasons, "1.31.0", Some(54503)),
     /// Give access to additional metadata about declarative macro meta-variables.
@@ -527,7 +529,7 @@ declare_features! (
     /// Allow negative trait implementations.
     (unstable, negative_impls, "1.44.0", Some(68318)),
     /// Allows the `!` pattern.
-    (incomplete, never_patterns, "CURRENT_RUSTC_VERSION", Some(118155)),
+    (incomplete, never_patterns, "1.76.0", Some(118155)),
     /// Allows the `!` type. Does not imply 'exhaustive_patterns' (below) any more.
     (unstable, never_type, "1.13.0", Some(35121)),
     /// Allows diverging expressions to fall back to `!` rather than `()`.

compiler/rustc_hir/src/hir.rs

@@ -417,8 +417,7 @@ pub enum GenericArgsParentheses {
     ParenSugar,
 }
 
-/// A modifier on a bound, currently this is only used for `?Sized`, where the
-/// modifier is `Maybe`. Negative bounds should also be handled here.
+/// A modifier on a trait bound.
 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, HashStable_Generic)]
 pub enum TraitBoundModifier {
     None,
@@ -1352,15 +1351,8 @@ impl<'hir> Body<'hir> {
 /// The type of source expression that caused this coroutine to be created.
 #[derive(Clone, PartialEq, Eq, Debug, Copy, Hash, HashStable_Generic, Encodable, Decodable)]
 pub enum CoroutineKind {
-    /// An explicit `async` block or the body of an `async` function.
-    Async(CoroutineSource),
-
-    /// An explicit `gen` block or the body of a `gen` function.
-    Gen(CoroutineSource),
-
-    /// An explicit `async gen` block or the body of an `async gen` function,
-    /// which is able to both `yield` and `.await`.
-    AsyncGen(CoroutineSource),
+    /// A coroutine that comes from a desugaring.
+    Desugared(CoroutineDesugaring, CoroutineSource),
 
     /// A coroutine literal created via a `yield` inside a closure.
     Coroutine,
@@ -1369,31 +1361,11 @@ pub enum CoroutineKind {
 impl fmt::Display for CoroutineKind {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
-            CoroutineKind::Async(k) => {
-                if f.alternate() {
-                    f.write_str("`async` ")?;
-                } else {
-                    f.write_str("async ")?
-                }
+            CoroutineKind::Desugared(d, k) => {
+                d.fmt(f)?;
                 k.fmt(f)
             }
             CoroutineKind::Coroutine => f.write_str("coroutine"),
-            CoroutineKind::Gen(k) => {
-                if f.alternate() {
-                    f.write_str("`gen` ")?;
-                } else {
-                    f.write_str("gen ")?
-                }
-                k.fmt(f)
-            }
-            CoroutineKind::AsyncGen(k) => {
-                if f.alternate() {
-                    f.write_str("`async gen` ")?;
-                } else {
-                    f.write_str("async gen ")?
-                }
-                k.fmt(f)
-            }
         }
     }
 }
@@ -1426,6 +1398,49 @@ impl fmt::Display for CoroutineSource {
     }
 }
 
+#[derive(Clone, PartialEq, Eq, Debug, Copy, Hash, HashStable_Generic, Encodable, Decodable)]
+pub enum CoroutineDesugaring {
+    /// An explicit `async` block or the body of an `async` function.
+    Async,
+
+    /// An explicit `gen` block or the body of a `gen` function.
+    Gen,
+
+    /// An explicit `async gen` block or the body of an `async gen` function,
+    /// which is able to both `yield` and `.await`.
+    AsyncGen,
+}
+
+impl fmt::Display for CoroutineDesugaring {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            CoroutineDesugaring::Async => {
+                if f.alternate() {
+                    f.write_str("`async` ")?;
+                } else {
+                    f.write_str("async ")?
+                }
+            }
+            CoroutineDesugaring::Gen => {
+                if f.alternate() {
+                    f.write_str("`gen` ")?;
+                } else {
+                    f.write_str("gen ")?
+                }
+            }
+            CoroutineDesugaring::AsyncGen => {
+                if f.alternate() {
+                    f.write_str("`async gen` ")?;
+                } else {
+                    f.write_str("async gen ")?
+                }
+            }
+        }
+
+        Ok(())
+    }
+}
+
 #[derive(Copy, Clone, Debug)]
 pub enum BodyOwnerKind {
     /// Functions and methods.

compiler/rustc_hir/src/lang_items.rs

@@ -307,6 +307,9 @@ language_item_table! {
     Context,                 sym::Context,             context,                    Target::Struct,         GenericRequirement::None;
     FuturePoll,              sym::poll,                future_poll_fn,             Target::Method(MethodKind::Trait { body: false }), GenericRequirement::None;
 
+    AsyncIteratorPollNext,   sym::async_iterator_poll_next, async_iterator_poll_next, Target::Method(MethodKind::Trait { body: false }), GenericRequirement::Exact(0);
+    IntoAsyncIterIntoIter,   sym::into_async_iter_into_iter, into_async_iter_into_iter, Target::Method(MethodKind::Trait { body: false }), GenericRequirement::Exact(0);
+
     Option,                  sym::Option,              option_type,                Target::Enum,           GenericRequirement::None;
     OptionSome,              sym::Some,                option_some_variant,        Target::Variant,        GenericRequirement::None;
     OptionNone,              sym::None,                option_none_variant,        Target::Variant,        GenericRequirement::None;

compiler/rustc_hir_analysis/src/astconv/mod.rs

@@ -378,7 +378,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
             assert!(self_ty.is_none());
         }
 
-        let arg_count = check_generic_arg_count(
+        let mut arg_count = check_generic_arg_count(
             tcx,
             span,
             def_id,
@@ -560,6 +560,14 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
             inferred_params: vec![],
             infer_args,
         };
+        if let ty::BoundConstness::ConstIfConst = constness
+            && generics.has_self
+            && !tcx.has_attr(def_id, sym::const_trait)
+        {
+            let e = tcx.sess.emit_err(crate::errors::ConstBoundForNonConstTrait { span });
+            arg_count.correct =
+                Err(GenericArgCountMismatch { reported: Some(e), invalid_args: vec![] });
+        }
         let args = create_args_for_parent_generic_args(
             tcx,
             def_id,
@@ -570,13 +578,6 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
             &mut args_ctx,
         );
 
-        if let ty::BoundConstness::ConstIfConst = constness
-            && generics.has_self
-            && !tcx.has_attr(def_id, sym::const_trait)
-        {
-            tcx.sess.emit_err(crate::errors::ConstBoundForNonConstTrait { span });
-        }
-
         (args, arg_count)
     }
 
@@ -2686,7 +2687,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
         &self,
         constrained_regions: FxHashSet<ty::BoundRegionKind>,
         referenced_regions: FxHashSet<ty::BoundRegionKind>,
-        generate_err: impl Fn(&str) -> DiagnosticBuilder<'tcx, ErrorGuaranteed>,
+        generate_err: impl Fn(&str) -> DiagnosticBuilder<'tcx>,
     ) {
         for br in referenced_regions.difference(&constrained_regions) {
             let br_name = match *br {

compiler/rustc_hir_analysis/src/check/entry.rs

@@ -124,7 +124,10 @@ fn check_main_fn_ty(tcx: TyCtxt<'_>, main_def_id: DefId) {
     if let Some(term_did) = tcx.lang_items().termination() {
         let return_ty = main_fnsig.output();
         let return_ty_span = main_fn_return_type_span(tcx, main_def_id).unwrap_or(main_span);
-        let return_ty = return_ty.skip_binder();
+        let Some(return_ty) = return_ty.no_bound_vars() else {
+            tcx.sess.emit_err(errors::MainFunctionReturnTypeGeneric { span: return_ty_span });
+            return;
+        };
         let infcx = tcx.infer_ctxt().build();
         let cause = traits::ObligationCause::new(
             return_ty_span,

compiler/rustc_hir_analysis/src/check/wfcheck.rs

@@ -1912,11 +1912,7 @@ fn check_mod_type_wf(tcx: TyCtxt<'_>, module: LocalModDefId) -> Result<(), Error
     res.and(items.par_foreign_items(|item| tcx.ensure().check_well_formed(item.owner_id)))
 }
 
-fn error_392(
-    tcx: TyCtxt<'_>,
-    span: Span,
-    param_name: Symbol,
-) -> DiagnosticBuilder<'_, ErrorGuaranteed> {
+fn error_392(tcx: TyCtxt<'_>, span: Span, param_name: Symbol) -> DiagnosticBuilder<'_> {
     let mut err = struct_span_err!(tcx.sess, span, E0392, "parameter `{param_name}` is never used");
     err.span_label(span, "unused parameter");
     err

compiler/rustc_hir_analysis/src/collect.rs

@@ -181,7 +181,7 @@ pub(crate) fn placeholder_type_error_diag<'tcx>(
     suggest: bool,
     hir_ty: Option<&hir::Ty<'_>>,
     kind: &'static str,
-) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+) -> DiagnosticBuilder<'tcx> {
     if placeholder_types.is_empty() {
         return bad_placeholder(tcx, additional_spans, kind);
     }
@@ -333,7 +333,7 @@ fn bad_placeholder<'tcx>(
     tcx: TyCtxt<'tcx>,
     mut spans: Vec<Span>,
     kind: &'static str,
-) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+) -> DiagnosticBuilder<'tcx> {
     let kind = if kind.ends_with('s') { format!("{kind}es") } else { format!("{kind}s") };
 
     spans.sort();

compiler/rustc_hir_analysis/src/errors.rs

@@ -2,8 +2,8 @@
 
 use crate::fluent_generated as fluent;
 use rustc_errors::{
-    error_code, Applicability, DiagCtxt, DiagnosticBuilder, ErrorGuaranteed, IntoDiagnostic,
-    MultiSpan,
+    error_code, Applicability, DiagCtxt, DiagnosticBuilder, EmissionGuarantee, IntoDiagnostic,
+    Level, MultiSpan,
 };
 use rustc_macros::{Diagnostic, LintDiagnostic, Subdiagnostic};
 use rustc_middle::ty::Ty;
@@ -315,14 +315,12 @@ pub struct MissingTypeParams {
 }
 
 // Manual implementation of `IntoDiagnostic` to be able to call `span_to_snippet`.
-impl<'a> IntoDiagnostic<'a> for MissingTypeParams {
+impl<'a, G: EmissionGuarantee> IntoDiagnostic<'a, G> for MissingTypeParams {
     #[track_caller]
-    fn into_diagnostic(self, dcx: &'a DiagCtxt) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
-        let mut err = dcx.struct_span_err_with_code(
-            self.span,
-            fluent::hir_analysis_missing_type_params,
-            error_code!(E0393),
-        );
+    fn into_diagnostic(self, dcx: &'a DiagCtxt, level: Level) -> DiagnosticBuilder<'a, G> {
+        let mut err = DiagnosticBuilder::new(dcx, level, fluent::hir_analysis_missing_type_params);
+        err.set_span(self.span);
+        err.code(error_code!(E0393));
         err.set_arg("parameterCount", self.missing_type_params.len());
         err.set_arg(
             "parameters",

compiler/rustc_hir_analysis/src/outlives/mod.rs

@@ -4,7 +4,6 @@ use rustc_hir::def_id::LocalDefId;
 use rustc_middle::query::Providers;
 use rustc_middle::ty::GenericArgKind;
 use rustc_middle::ty::{self, CratePredicatesMap, ToPredicate, TyCtxt};
-use rustc_span::symbol::sym;
 use rustc_span::Span;
 
 mod explicit;
@@ -49,25 +48,6 @@ fn inferred_outlives_of(tcx: TyCtxt<'_>, item_def_id: LocalDefId) -> &[(ty::Clau
                 let predicates =
                     crate_map.predicates.get(&item_def_id.to_def_id()).copied().unwrap_or(&[]);
 
-                if tcx.has_attr(item_def_id, sym::rustc_outlives) {
-                    let mut pred: Vec<String> = predicates
-                        .iter()
-                        .map(|(out_pred, _)| match out_pred.kind().skip_binder() {
-                            ty::ClauseKind::RegionOutlives(p) => p.to_string(),
-                            ty::ClauseKind::TypeOutlives(p) => p.to_string(),
-                            err => bug!("unexpected clause {:?}", err),
-                        })
-                        .collect();
-                    pred.sort();
-
-                    let span = tcx.def_span(item_def_id);
-                    let mut err = tcx.sess.struct_span_err(span, "rustc_outlives");
-                    for p in pred {
-                        err.note(p);
-                    }
-                    err.emit();
-                }
-
                 debug!("inferred_outlives_of({:?}) = {:?}", item_def_id, predicates);
 
                 predicates

compiler/rustc_hir_analysis/src/outlives/test.rs

@@ -1,5 +1,4 @@
-use rustc_errors::struct_span_err;
-use rustc_middle::ty::TyCtxt;
+use rustc_middle::ty::{self, TyCtxt};
 use rustc_span::symbol::sym;
 
 pub fn test_inferred_outlives(tcx: TyCtxt<'_>) {
@@ -7,15 +6,23 @@ pub fn test_inferred_outlives(tcx: TyCtxt<'_>) {
         // For unit testing: check for a special "rustc_outlives"
         // attribute and report an error with various results if found.
         if tcx.has_attr(id.owner_id, sym::rustc_outlives) {
-            let inferred_outlives_of = tcx.inferred_outlives_of(id.owner_id);
-            struct_span_err!(
-                tcx.sess,
-                tcx.def_span(id.owner_id),
-                E0640,
-                "{:?}",
-                inferred_outlives_of
-            )
-            .emit();
+            let predicates = tcx.inferred_outlives_of(id.owner_id);
+            let mut pred: Vec<String> = predicates
+                .iter()
+                .map(|(out_pred, _)| match out_pred.kind().skip_binder() {
+                    ty::ClauseKind::RegionOutlives(p) => p.to_string(),
+                    ty::ClauseKind::TypeOutlives(p) => p.to_string(),
+                    err => bug!("unexpected clause {:?}", err),
+                })
+                .collect();
+            pred.sort();
+
+            let span = tcx.def_span(id.owner_id);
+            let mut err = tcx.sess.struct_span_err(span, "rustc_outlives");
+            for p in pred {
+                err.note(p);
+            }
+            err.emit();
         }
     }
 }

compiler/rustc_hir_analysis/src/structured_errors.rs

@@ -6,7 +6,7 @@ pub use self::{
     missing_cast_for_variadic_arg::*, sized_unsized_cast::*, wrong_number_of_generic_args::*,
 };
 
-use rustc_errors::{DiagnosticBuilder, DiagnosticId, ErrorGuaranteed};
+use rustc_errors::{DiagnosticBuilder, DiagnosticId};
 use rustc_session::Session;
 
 pub trait StructuredDiagnostic<'tcx> {
@@ -14,7 +14,7 @@ pub trait StructuredDiagnostic<'tcx> {
 
     fn code(&self) -> DiagnosticId;
 
-    fn diagnostic(&self) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+    fn diagnostic(&self) -> DiagnosticBuilder<'tcx> {
         let err = self.diagnostic_common();
 
         if self.session().teach(&self.code()) {
@@ -24,19 +24,13 @@ pub trait StructuredDiagnostic<'tcx> {
         }
     }
 
-    fn diagnostic_common(&self) -> DiagnosticBuilder<'tcx, ErrorGuaranteed>;
+    fn diagnostic_common(&self) -> DiagnosticBuilder<'tcx>;
 
-    fn diagnostic_regular(
-        &self,
-        err: DiagnosticBuilder<'tcx, ErrorGuaranteed>,
-    ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+    fn diagnostic_regular(&self, err: DiagnosticBuilder<'tcx>) -> DiagnosticBuilder<'tcx> {
         err
     }
 
-    fn diagnostic_extended(
-        &self,
-        err: DiagnosticBuilder<'tcx, ErrorGuaranteed>,
-    ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+    fn diagnostic_extended(&self, err: DiagnosticBuilder<'tcx>) -> DiagnosticBuilder<'tcx> {
         err
     }
 }

compiler/rustc_hir_analysis/src/structured_errors/missing_cast_for_variadic_arg.rs

@@ -1,5 +1,5 @@
 use crate::{errors, structured_errors::StructuredDiagnostic};
-use rustc_errors::{DiagnosticBuilder, DiagnosticId, ErrorGuaranteed};
+use rustc_errors::{DiagnosticBuilder, DiagnosticId};
 use rustc_middle::ty::{Ty, TypeVisitableExt};
 use rustc_session::Session;
 use rustc_span::Span;
@@ -20,7 +20,7 @@ impl<'tcx> StructuredDiagnostic<'tcx> for MissingCastForVariadicArg<'tcx, '_> {
         rustc_errors::error_code!(E0617)
     }
 
-    fn diagnostic_common(&self) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+    fn diagnostic_common(&self) -> DiagnosticBuilder<'tcx> {
         let (sugg_span, replace, help) =
             if let Ok(snippet) = self.sess.source_map().span_to_snippet(self.span) {
                 (Some(self.span), format!("{} as {}", snippet, self.cast_ty), None)
@@ -44,10 +44,7 @@ impl<'tcx> StructuredDiagnostic<'tcx> for MissingCastForVariadicArg<'tcx, '_> {
         err
     }
 
-    fn diagnostic_extended(
-        &self,
-        mut err: DiagnosticBuilder<'tcx, ErrorGuaranteed>,
-    ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+    fn diagnostic_extended(&self, mut err: DiagnosticBuilder<'tcx>) -> DiagnosticBuilder<'tcx> {
         err.note(format!(
             "certain types, like `{}`, must be casted before passing them to a \
                 variadic function, because of arcane ABI rules dictated by the C \

compiler/rustc_hir_analysis/src/structured_errors/sized_unsized_cast.rs

@@ -1,5 +1,5 @@
 use crate::{errors, structured_errors::StructuredDiagnostic};
-use rustc_errors::{DiagnosticBuilder, DiagnosticId, ErrorGuaranteed};
+use rustc_errors::{DiagnosticBuilder, DiagnosticId};
 use rustc_middle::ty::{Ty, TypeVisitableExt};
 use rustc_session::Session;
 use rustc_span::Span;
@@ -20,7 +20,7 @@ impl<'tcx> StructuredDiagnostic<'tcx> for SizedUnsizedCast<'tcx> {
         rustc_errors::error_code!(E0607)
     }
 
-    fn diagnostic_common(&self) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+    fn diagnostic_common(&self) -> DiagnosticBuilder<'tcx> {
         let mut err = self.sess.create_err(errors::CastThinPointerToFatPointer {
             span: self.span,
             expr_ty: self.expr_ty,
@@ -34,10 +34,7 @@ impl<'tcx> StructuredDiagnostic<'tcx> for SizedUnsizedCast<'tcx> {
         err
     }
 
-    fn diagnostic_extended(
-        &self,
-        mut err: DiagnosticBuilder<'tcx, ErrorGuaranteed>,
-    ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+    fn diagnostic_extended(&self, mut err: DiagnosticBuilder<'tcx>) -> DiagnosticBuilder<'tcx> {
         err.help(
             "Thin pointers are \"simple\" pointers: they are purely a reference to a
 memory address.

compiler/rustc_hir_analysis/src/structured_errors/wrong_number_of_generic_args.rs

@@ -1,7 +1,6 @@
 use crate::structured_errors::StructuredDiagnostic;
 use rustc_errors::{
-    pluralize, Applicability, Diagnostic, DiagnosticBuilder, DiagnosticId, ErrorGuaranteed,
-    MultiSpan,
+    pluralize, Applicability, Diagnostic, DiagnosticBuilder, DiagnosticId, MultiSpan,
 };
 use rustc_hir as hir;
 use rustc_middle::ty::{self as ty, AssocItems, AssocKind, TyCtxt};
@@ -521,7 +520,7 @@ impl<'a, 'tcx> WrongNumberOfGenericArgs<'a, 'tcx> {
         }
     }
 
-    fn start_diagnostics(&self) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+    fn start_diagnostics(&self) -> DiagnosticBuilder<'tcx> {
         let span = self.path_segment.ident.span;
         let msg = self.create_error_message();
 
@@ -1113,7 +1112,7 @@ impl<'tcx> StructuredDiagnostic<'tcx> for WrongNumberOfGenericArgs<'_, 'tcx> {
         rustc_errors::error_code!(E0107)
     }
 
-    fn diagnostic_common(&self) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+    fn diagnostic_common(&self) -> DiagnosticBuilder<'tcx> {
         let mut err = self.start_diagnostics();
 
         self.notify(&mut err);

compiler/rustc_hir_pretty/src/lib.rs

@@ -553,17 +553,7 @@ impl<'a> State<'a> {
             }
             hir::ItemKind::OpaqueTy(opaque_ty) => {
                 self.print_item_type(item, opaque_ty.generics, |state| {
-                    let mut real_bounds = Vec::with_capacity(opaque_ty.bounds.len());
-                    for b in opaque_ty.bounds {
-                        if let GenericBound::Trait(ptr, hir::TraitBoundModifier::Maybe) = b {
-                            state.space();
-                            state.word_space("for ?");
-                            state.print_trait_ref(&ptr.trait_ref);
-                        } else {
-                            real_bounds.push(b);
-                        }
-                    }
-                    state.print_bounds("= impl", real_bounds);
+                    state.print_bounds("= impl", opaque_ty.bounds)
                 });
             }
             hir::ItemKind::Enum(ref enum_definition, params) => {
@@ -625,17 +615,7 @@ impl<'a> State<'a> {
                 self.word_nbsp("trait");
                 self.print_ident(item.ident);
                 self.print_generic_params(generics.params);
-                let mut real_bounds = Vec::with_capacity(bounds.len());
-                for b in bounds {
-                    if let GenericBound::Trait(ptr, hir::TraitBoundModifier::Maybe) = b {
-                        self.space();
-                        self.word_space("for ?");
-                        self.print_trait_ref(&ptr.trait_ref);
-                    } else {
-                        real_bounds.push(b);
-                    }
-                }
-                self.print_bounds(":", real_bounds);
+                self.print_bounds(":", bounds);
                 self.print_where_clause(generics);
                 self.word(" ");
                 self.bopen();

compiler/rustc_hir_typeck/src/callee.rs

@@ -305,8 +305,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         ) = (parent_node, callee_node)
         {
             let fn_decl_span = if hir.body(body).coroutine_kind
-                == Some(hir::CoroutineKind::Async(hir::CoroutineSource::Closure))
-            {
+                == Some(hir::CoroutineKind::Desugared(
+                    hir::CoroutineDesugaring::Async,
+                    hir::CoroutineSource::Closure,
+                )) {
                 // Actually need to unwrap one more layer of HIR to get to
                 // the _real_ closure...
                 let async_closure = hir.parent_id(parent_hir_id);

compiler/rustc_hir_typeck/src/cast.rs

@@ -187,7 +187,7 @@ fn make_invalid_casting_error<'a, 'tcx>(
     expr_ty: Ty<'tcx>,
     cast_ty: Ty<'tcx>,
     fcx: &FnCtxt<'a, 'tcx>,
-) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
+) -> DiagnosticBuilder<'a> {
     type_error_struct!(
         sess,
         span,

compiler/rustc_hir_typeck/src/check.rs

@@ -59,7 +59,8 @@ pub(super) fn check_fn<'a, 'tcx>(
         && can_be_coroutine.is_some()
     {
         let yield_ty = match kind {
-            hir::CoroutineKind::Gen(..) | hir::CoroutineKind::Coroutine => {
+            hir::CoroutineKind::Desugared(hir::CoroutineDesugaring::Gen, _)
+            | hir::CoroutineKind::Coroutine => {
                 let yield_ty = fcx.next_ty_var(TypeVariableOrigin {
                     kind: TypeVariableOriginKind::TypeInference,
                     span,
@@ -71,7 +72,7 @@ pub(super) fn check_fn<'a, 'tcx>(
             // guide inference on the yield type so that we can handle `AsyncIterator`
             // in this block in projection correctly. In the new trait solver, it is
             // not a problem.
-            hir::CoroutineKind::AsyncGen(..) => {
+            hir::CoroutineKind::Desugared(hir::CoroutineDesugaring::AsyncGen, _) => {
                 let yield_ty = fcx.next_ty_var(TypeVariableOrigin {
                     kind: TypeVariableOriginKind::TypeInference,
                     span,
@@ -89,7 +90,7 @@ pub(super) fn check_fn<'a, 'tcx>(
                     .into()]),
                 )
             }
-            hir::CoroutineKind::Async(..) => Ty::new_unit(tcx),
+            hir::CoroutineKind::Desugared(hir::CoroutineDesugaring::Async, _) => Ty::new_unit(tcx),
         };
 
         // Resume type defaults to `()` if the coroutine has no argument.

compiler/rustc_hir_typeck/src/closure.rs

@@ -634,7 +634,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 // In the case of the async block that we create for a function body,
                 // we expect the return type of the block to match that of the enclosing
                 // function.
-                Some(hir::CoroutineKind::Async(hir::CoroutineSource::Fn)) => {
+                Some(hir::CoroutineKind::Desugared(
+                    hir::CoroutineDesugaring::Async,
+                    hir::CoroutineSource::Fn,
+                )) => {
                     debug!("closure is async fn body");
                     let def_id = self.tcx.hir().body_owner_def_id(body.id());
                     self.deduce_future_output_from_obligations(expr_def_id, def_id).unwrap_or_else(
@@ -651,9 +654,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     )
                 }
                 // All `gen {}` and `async gen {}` must return unit.
-                Some(hir::CoroutineKind::Gen(_) | hir::CoroutineKind::AsyncGen(_)) => {
-                    self.tcx.types.unit
-                }
+                Some(
+                    hir::CoroutineKind::Desugared(hir::CoroutineDesugaring::Gen, _)
+                    | hir::CoroutineKind::Desugared(hir::CoroutineDesugaring::AsyncGen, _),
+                ) => self.tcx.types.unit,
 
                 _ => astconv.ty_infer(None, decl.output.span()),
             },

compiler/rustc_hir_typeck/src/coercion.rs

@@ -36,9 +36,7 @@
 //! ```
 
 use crate::FnCtxt;
-use rustc_errors::{
-    struct_span_err, Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed, MultiSpan,
-};
+use rustc_errors::{struct_span_err, Applicability, Diagnostic, DiagnosticBuilder, MultiSpan};
 use rustc_hir as hir;
 use rustc_hir::def_id::DefId;
 use rustc_hir::intravisit::{self, Visitor};
@@ -1772,7 +1770,7 @@ impl<'tcx, 'exprs, E: AsCoercionSite> CoerceMany<'tcx, 'exprs, E> {
         id: hir::HirId,
         expression: Option<&'tcx hir::Expr<'tcx>>,
         blk_id: Option<hir::HirId>,
-    ) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
+    ) -> DiagnosticBuilder<'a> {
         let mut err = fcx.err_ctxt().report_mismatched_types(cause, expected, found, ty_err);
 
         let parent_id = fcx.tcx.hir().parent_id(id);

compiler/rustc_hir_typeck/src/demand.rs

@@ -1,6 +1,6 @@
 use crate::FnCtxt;
 use rustc_errors::MultiSpan;
-use rustc_errors::{Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed};
+use rustc_errors::{Applicability, Diagnostic, DiagnosticBuilder};
 use rustc_hir as hir;
 use rustc_hir::def::Res;
 use rustc_hir::intravisit::Visitor;
@@ -168,7 +168,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         sp: Span,
         expected: Ty<'tcx>,
         actual: Ty<'tcx>,
-    ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
+    ) -> Option<DiagnosticBuilder<'tcx>> {
         self.demand_suptype_with_origin(&self.misc(sp), expected, actual)
     }
 
@@ -178,7 +178,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         cause: &ObligationCause<'tcx>,
         expected: Ty<'tcx>,
         actual: Ty<'tcx>,
-    ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
+    ) -> Option<DiagnosticBuilder<'tcx>> {
         match self.at(cause, self.param_env).sup(DefineOpaqueTypes::Yes, expected, actual) {
             Ok(InferOk { obligations, value: () }) => {
                 self.register_predicates(obligations);
@@ -199,7 +199,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         sp: Span,
         expected: Ty<'tcx>,
         actual: Ty<'tcx>,
-    ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
+    ) -> Option<DiagnosticBuilder<'tcx>> {
         self.demand_eqtype_with_origin(&self.misc(sp), expected, actual)
     }
 
@@ -208,7 +208,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         cause: &ObligationCause<'tcx>,
         expected: Ty<'tcx>,
         actual: Ty<'tcx>,
-    ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
+    ) -> Option<DiagnosticBuilder<'tcx>> {
         match self.at(cause, self.param_env).eq(DefineOpaqueTypes::Yes, expected, actual) {
             Ok(InferOk { obligations, value: () }) => {
                 self.register_predicates(obligations);
@@ -246,7 +246,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         expected: Ty<'tcx>,
         mut expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>,
         allow_two_phase: AllowTwoPhase,
-    ) -> (Ty<'tcx>, Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>>) {
+    ) -> (Ty<'tcx>, Option<DiagnosticBuilder<'tcx>>) {
         let expected = self.resolve_vars_with_obligations(expected);
 
         let e = match self.coerce(expr, checked_ty, expected, allow_two_phase, None) {

compiler/rustc_hir_typeck/src/expr.rs

@@ -722,7 +722,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     if let [segment] = path.segments
                         && segment.ident.name == sym::rust
                     {
-                        fatally_break_rust(self.tcx);
+                        fatally_break_rust(self.tcx, expr.span);
                     }
                 }
             }
@@ -966,7 +966,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     pub fn check_for_missing_semi(
         &self,
         expr: &'tcx hir::Expr<'tcx>,
-        err: &mut DiagnosticBuilder<'_, ErrorGuaranteed>,
+        err: &mut DiagnosticBuilder<'_>,
     ) -> bool {
         if let hir::ExprKind::Binary(binop, lhs, rhs) = expr.kind
             && let hir::BinOpKind::Mul = binop.node
@@ -2738,7 +2738,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         field: Ident,
         expr_t: Ty<'tcx>,
         id: HirId,
-    ) -> DiagnosticBuilder<'_, ErrorGuaranteed> {
+    ) -> DiagnosticBuilder<'_> {
         let span = field.span;
         debug!("no_such_field_err(span: {:?}, field: {:?}, expr_t: {:?})", span, field, expr_t);
 
@@ -2821,11 +2821,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         err
     }
 
-    fn private_field_err(
-        &self,
-        field: Ident,
-        base_did: DefId,
-    ) -> DiagnosticBuilder<'_, ErrorGuaranteed> {
+    fn private_field_err(&self, field: Ident, base_did: DefId) -> DiagnosticBuilder<'_> {
         let struct_path = self.tcx().def_path_str(base_did);
         let kind_name = self.tcx().def_descr(base_did);
         let mut err = struct_span_err!(

compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs

@@ -1258,7 +1258,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         expected_ty: Ty<'tcx>,
         provided_ty: Ty<'tcx>,
         arg: &hir::Expr<'tcx>,
-        err: &mut rustc_errors::DiagnosticBuilder<'tcx, ErrorGuaranteed>,
+        err: &mut rustc_errors::DiagnosticBuilder<'tcx>,
     ) {
         if let ty::RawPtr(ty::TypeAndMut { mutbl: hir::Mutability::Mut, .. }) = expected_ty.kind()
             && let ty::RawPtr(ty::TypeAndMut { mutbl: hir::Mutability::Not, .. }) =

compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs

@@ -17,8 +17,8 @@ use rustc_hir::def::Res;
 use rustc_hir::def::{CtorKind, CtorOf, DefKind};
 use rustc_hir::lang_items::LangItem;
 use rustc_hir::{
-    CoroutineKind, CoroutineSource, Expr, ExprKind, GenericBound, HirId, Node, Path, QPath, Stmt,
-    StmtKind, TyKind, WherePredicate,
+    CoroutineDesugaring, CoroutineKind, CoroutineSource, Expr, ExprKind, GenericBound, HirId, Node,
+    Path, QPath, Stmt, StmtKind, TyKind, WherePredicate,
 };
 use rustc_hir_analysis::astconv::AstConv;
 use rustc_infer::traits::{self, StatementAsExpression};
@@ -549,7 +549,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 ty::Coroutine(def_id, ..)
                     if matches!(
                         self.tcx.coroutine_kind(def_id),
-                        Some(CoroutineKind::Async(CoroutineSource::Closure))
+                        Some(CoroutineKind::Desugared(
+                            CoroutineDesugaring::Async,
+                            CoroutineSource::Closure
+                        ))
                     ) =>
                 {
                     errors::SuggestBoxing::AsyncBody

compiler/rustc_hir_typeck/src/lib.rs

@@ -52,7 +52,7 @@ use crate::expectation::Expectation;
 use crate::fn_ctxt::RawTy;
 use crate::gather_locals::GatherLocalsVisitor;
 use rustc_data_structures::unord::UnordSet;
-use rustc_errors::{struct_span_err, DiagnosticId, ErrorGuaranteed, MultiSpan};
+use rustc_errors::{struct_span_err, DiagnosticId, ErrorGuaranteed};
 use rustc_hir as hir;
 use rustc_hir::def::{DefKind, Res};
 use rustc_hir::intravisit::Visitor;
@@ -412,24 +412,25 @@ enum TupleArgumentsFlag {
     TupleArguments,
 }
 
-fn fatally_break_rust(tcx: TyCtxt<'_>) {
+fn fatally_break_rust(tcx: TyCtxt<'_>, span: Span) -> ! {
     let dcx = tcx.sess.dcx();
-    dcx.span_bug_no_panic(
-        MultiSpan::new(),
+    let mut diag = dcx.struct_span_bug(
+        span,
         "It looks like you're trying to break rust; would you like some ICE?",
     );
-    dcx.note("the compiler expectedly panicked. this is a feature.");
-    dcx.note(
+    diag.note("the compiler expectedly panicked. this is a feature.");
+    diag.note(
         "we would appreciate a joke overview: \
          https://github.com/rust-lang/rust/issues/43162#issuecomment-320764675",
     );
-    dcx.note(format!("rustc {} running on {}", tcx.sess.cfg_version, config::host_triple(),));
+    diag.note(format!("rustc {} running on {}", tcx.sess.cfg_version, config::host_triple(),));
     if let Some((flags, excluded_cargo_defaults)) = rustc_session::utils::extra_compiler_flags() {
-        dcx.note(format!("compiler flags: {}", flags.join(" ")));
+        diag.note(format!("compiler flags: {}", flags.join(" ")));
         if excluded_cargo_defaults {
-            dcx.note("some of the compiler flags provided by cargo are hidden");
+            diag.note("some of the compiler flags provided by cargo are hidden");
         }
     }
+    diag.emit()
 }
 
 /// `expected` here is the expected number of explicit generic arguments on the trait.

compiler/rustc_hir_typeck/src/method/suggest.rs

@@ -13,8 +13,7 @@ use rustc_data_structures::fx::{FxIndexMap, FxIndexSet};
 use rustc_data_structures::unord::UnordSet;
 use rustc_errors::StashKey;
 use rustc_errors::{
-    pluralize, struct_span_err, Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed,
-    MultiSpan,
+    pluralize, struct_span_err, Applicability, Diagnostic, DiagnosticBuilder, MultiSpan,
 };
 use rustc_hir as hir;
 use rustc_hir::def::DefKind;
@@ -120,7 +119,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         args: Option<&'tcx [hir::Expr<'tcx>]>,
         expected: Expectation<'tcx>,
         trait_missing_method: bool,
-    ) -> Option<DiagnosticBuilder<'_, ErrorGuaranteed>> {
+    ) -> Option<DiagnosticBuilder<'_>> {
         // Avoid suggestions when we don't know what's going on.
         if rcvr_ty.references_error() {
             return None;
@@ -261,7 +260,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         &self,
         rcvr_ty: Ty<'tcx>,
         rcvr_expr: &hir::Expr<'tcx>,
-    ) -> DiagnosticBuilder<'_, ErrorGuaranteed> {
+    ) -> DiagnosticBuilder<'_> {
         let mut file = None;
         let ty_str = self.tcx.short_ty_string(rcvr_ty, &mut file);
         let mut err = struct_span_err!(
@@ -299,7 +298,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         no_match_data: &mut NoMatchData<'tcx>,
         expected: Expectation<'tcx>,
         trait_missing_method: bool,
-    ) -> Option<DiagnosticBuilder<'_, ErrorGuaranteed>> {
+    ) -> Option<DiagnosticBuilder<'_>> {
         let mode = no_match_data.mode;
         let tcx = self.tcx;
         let rcvr_ty = self.resolve_vars_if_possible(rcvr_ty);

compiler/rustc_hir_typeck/src/pat.rs

@@ -99,7 +99,7 @@ impl<'tcx> FnCtxt<'_, 'tcx> {
         expected: Ty<'tcx>,
         actual: Ty<'tcx>,
         ti: TopInfo<'tcx>,
-    ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
+    ) -> Option<DiagnosticBuilder<'tcx>> {
         let mut diag =
             self.demand_eqtype_with_origin(&self.pattern_cause(ti, cause_span), expected, actual)?;
         if let Some(expr) = ti.origin_expr {
@@ -967,7 +967,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
     fn emit_bad_pat_path(
         &self,
-        mut e: DiagnosticBuilder<'_, ErrorGuaranteed>,
+        mut e: DiagnosticBuilder<'_>,
         pat: &hir::Pat<'tcx>,
         res: Res,
         pat_res: Res,
@@ -1508,7 +1508,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         variant: &VariantDef,
         pat: &'_ Pat<'_>,
         fields: &[hir::PatField<'_>],
-    ) -> Option<DiagnosticBuilder<'_, ErrorGuaranteed>> {
+    ) -> Option<DiagnosticBuilder<'_>> {
         // if this is a tuple struct, then all field names will be numbers
         // so if any fields in a struct pattern use shorthand syntax, they will
         // be invalid identifiers (for example, Foo { 0, 1 }).
@@ -1584,7 +1584,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         pat: &'tcx Pat<'tcx>,
         variant: &ty::VariantDef,
         args: &'tcx ty::List<ty::GenericArg<'tcx>>,
-    ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+    ) -> DiagnosticBuilder<'tcx> {
         let tcx = self.tcx;
         let (field_names, t, plural) = if let [field] = inexistent_fields {
             (format!("a field named `{}`", field.ident), "this", "")
@@ -1689,7 +1689,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         pat: &Pat<'_>,
         fields: &'tcx [hir::PatField<'tcx>],
         variant: &ty::VariantDef,
-    ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
+    ) -> Option<DiagnosticBuilder<'tcx>> {
         if let (Some(CtorKind::Fn), PatKind::Struct(qpath, pattern_fields, ..)) =
             (variant.ctor_kind(), &pat.kind)
         {
@@ -1775,7 +1775,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         &self,
         pat: &Pat<'_>,
         fields: &'tcx [hir::PatField<'tcx>],
-    ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+    ) -> DiagnosticBuilder<'tcx> {
         let mut err = self
             .tcx
             .sess
@@ -1867,7 +1867,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         unmentioned_fields: &[(&ty::FieldDef, Ident)],
         have_inaccessible_fields: bool,
         fields: &'tcx [hir::PatField<'tcx>],
-    ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+    ) -> DiagnosticBuilder<'tcx> {
         let inaccessible = if have_inaccessible_fields { " and inaccessible fields" } else { "" };
         let field_names = if let [(_, field)] = unmentioned_fields {
             format!("field `{field}`{inaccessible}")

compiler/rustc_index/src/bit_set.rs

@@ -502,6 +502,7 @@ impl<T: Idx> ChunkedBitSet<T> {
                     };
                     #[cfg(not(feature = "nightly"))]
                     let mut words = {
+                        // FIXME: unconditionally use `Rc::new_zeroed` once it is stable (#63291).
                         let words = mem::MaybeUninit::<[Word; CHUNK_WORDS]>::zeroed();
                         // SAFETY: `words` can safely be all zeroes.
                         let words = unsafe { words.assume_init() };
@@ -567,6 +568,7 @@ impl<T: Idx> ChunkedBitSet<T> {
                     };
                     #[cfg(not(feature = "nightly"))]
                     let mut words = {
+                        // FIXME: unconditionally use `Rc::new_zeroed` once it is stable (#63291).
                         let words = mem::MaybeUninit::<[Word; CHUNK_WORDS]>::zeroed();
                         // SAFETY: `words` can safely be all zeroes.
                         let words = unsafe { words.assume_init() };