Auto merge of #121169 - GuillaumeGomez:rollup-oxk5d5j, r=GuillaumeGomez

Rollup of 10 pull requests

Successful merges:

 - #120777 (Bump Unicode to version 15.1.0, regenerate tables)
 - #120971 (Fix comment in core/src/str/validations.rs)
 - #121095 (Add extra indent spaces for rust-playground link)
 - #121109 (Add an ErrorGuaranteed to ast::TyKind::Err (attempt 2))
 - #121119 (Make `async Fn` trait kind errors better)
 - #121141 (Fix closure kind docs)
 - #121145 (Update aarch64 target feature docs to match LLVM)
 - #121146 (Only point out non-diverging arms for match suggestions)
 - #121147 (Avoid debug logging entire MIR body)
 - #121155 (doc: add note about panicking examples for strict_overflow_ops)

r? `@ghost`
`@rustbot` modify labels: rollup

23 files changed, 243 insertions, 115 deletions

diff --git a/compiler/rustc_ast/src/ast.rs b/compiler/rustc_ast/src/ast.rs
index b74938621b3..3fdb2a2225a 100644
--- a/compiler/rustc_ast/src/ast.rs
+++ b/compiler/rustc_ast/src/ast.rs
@@ -2136,10 +2136,12 @@ pub enum TyKind {
     ImplicitSelf,
     /// A macro in the type position.
     MacCall(P<MacCall>),
-    /// Placeholder for a kind that has failed to be defined.
-    Err,
     /// Placeholder for a `va_list`.
     CVarArgs,
+    /// Sometimes we need a dummy value when no error has occurred.
+    Dummy,
+    /// Placeholder for a kind that has failed to be defined.
+    Err(ErrorGuaranteed),
 }
 
 impl TyKind {
diff --git a/compiler/rustc_ast/src/mut_visit.rs b/compiler/rustc_ast/src/mut_visit.rs
index d482ada170e..c42c4199973 100644
--- a/compiler/rustc_ast/src/mut_visit.rs
+++ b/compiler/rustc_ast/src/mut_visit.rs
@@ -481,7 +481,12 @@ pub fn noop_visit_ty<T: MutVisitor>(ty: &mut P<Ty>, vis: &mut T) {
     let Ty { id, kind, span, tokens } = ty.deref_mut();
     vis.visit_id(id);
     match kind {
-        TyKind::Infer | TyKind::ImplicitSelf | TyKind::Err | TyKind::Never | TyKind::CVarArgs => {}
+        TyKind::Infer
+        | TyKind::ImplicitSelf
+        | TyKind::Err(_)
+        | TyKind::Dummy
+        | TyKind::Never
+        | TyKind::CVarArgs => {}
         TyKind::Slice(ty) => vis.visit_ty(ty),
         TyKind::Ptr(mt) => vis.visit_mt(mt),
         TyKind::Ref(lt, mt) => {
@@ -1649,7 +1654,7 @@ impl DummyAstNode for Ty {
     fn dummy() -> Self {
         Ty {
             id: DUMMY_NODE_ID,
-            kind: TyKind::Err,
+            kind: TyKind::Dummy,
             span: Default::default(),
             tokens: Default::default(),
         }
diff --git a/compiler/rustc_ast/src/visit.rs b/compiler/rustc_ast/src/visit.rs
index 4aaaa0ba424..83f6746bdeb 100644
--- a/compiler/rustc_ast/src/visit.rs
+++ b/compiler/rustc_ast/src/visit.rs
@@ -447,7 +447,7 @@ pub fn walk_ty<'a, V: Visitor<'a>>(visitor: &mut V, typ: &'a Ty) {
             walk_list!(visitor, visit_param_bound, bounds, BoundKind::Impl);
         }
         TyKind::Typeof(expression) => visitor.visit_anon_const(expression),
-        TyKind::Infer | TyKind::ImplicitSelf | TyKind::Err => {}
+        TyKind::Infer | TyKind::ImplicitSelf | TyKind::Dummy | TyKind::Err(_) => {}
         TyKind::MacCall(mac) => visitor.visit_mac_call(mac),
         TyKind::Never | TyKind::CVarArgs => {}
         TyKind::AnonStruct(_, ref fields) | TyKind::AnonUnion(_, ref fields) => {
diff --git a/compiler/rustc_ast_lowering/src/lib.rs b/compiler/rustc_ast_lowering/src/lib.rs
index eab1383b635..e9e1095a4ae 100644
--- a/compiler/rustc_ast_lowering/src/lib.rs
+++ b/compiler/rustc_ast_lowering/src/lib.rs
@@ -1286,7 +1286,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
     fn lower_ty_direct(&mut self, t: &Ty, itctx: ImplTraitContext) -> hir::Ty<'hir> {
         let kind = match &t.kind {
             TyKind::Infer => hir::TyKind::Infer,
-            TyKind::Err => hir::TyKind::Err(self.dcx().has_errors().unwrap()),
+            TyKind::Err(guar) => hir::TyKind::Err(*guar),
             // Lower the anonymous structs or unions in a nested lowering context.
             //
             // ```
@@ -1504,6 +1504,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                 );
                 hir::TyKind::Err(guar)
             }
+            TyKind::Dummy => panic!("`TyKind::Dummy` should never be lowered"),
         };
 
         hir::Ty { kind, span: self.lower_span(t.span), hir_id: self.lower_node_id(t.id) }
diff --git a/compiler/rustc_ast_passes/src/ast_validation.rs b/compiler/rustc_ast_passes/src/ast_validation.rs
index ebc5c17a4c4..fa0f5326196 100644
--- a/compiler/rustc_ast_passes/src/ast_validation.rs
+++ b/compiler/rustc_ast_passes/src/ast_validation.rs
@@ -881,7 +881,8 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
                         &item.vis,
                         errors::VisibilityNotPermittedNote::TraitImpl,
                     );
-                    if let TyKind::Err = self_ty.kind {
+                    // njn: use Dummy here
+                    if let TyKind::Err(_) = self_ty.kind {
                         this.dcx().emit_err(errors::ObsoleteAuto { span: item.span });
                     }
                     if let (&Unsafe::Yes(span), &ImplPolarity::Negative(sp)) = (unsafety, polarity)
diff --git a/compiler/rustc_ast_pretty/src/pprust/state.rs b/compiler/rustc_ast_pretty/src/pprust/state.rs
index 2765b235f99..7ea0078ea3b 100644
--- a/compiler/rustc_ast_pretty/src/pprust/state.rs
+++ b/compiler/rustc_ast_pretty/src/pprust/state.rs
@@ -1048,11 +1048,16 @@ impl<'a> State<'a> {
             ast::TyKind::Infer => {
                 self.word("_");
             }
-            ast::TyKind::Err => {
+            ast::TyKind::Err(_) => {
                 self.popen();
                 self.word("/*ERROR*/");
                 self.pclose();
             }
+            ast::TyKind::Dummy => {
+                self.popen();
+                self.word("/*DUMMY*/");
+                self.pclose();
+            }
             ast::TyKind::ImplicitSelf => {
                 self.word("Self");
             }
diff --git a/compiler/rustc_expand/src/base.rs b/compiler/rustc_expand/src/base.rs
index 09ab26421d6..09144523658 100644
--- a/compiler/rustc_expand/src/base.rs
+++ b/compiler/rustc_expand/src/base.rs
@@ -567,10 +567,13 @@ impl DummyResult {
     }
 
     /// A plain dummy type.
-    pub fn raw_ty(sp: Span, is_error: bool) -> P<ast::Ty> {
+    pub fn raw_ty(sp: Span) -> P<ast::Ty> {
+        // FIXME(nnethercote): you might expect `ast::TyKind::Dummy` to be used here, but some
+        // values produced here end up being lowered to HIR, which `ast::TyKind::Dummy` does not
+        // support, so we use an empty tuple instead.
         P(ast::Ty {
             id: ast::DUMMY_NODE_ID,
-            kind: if is_error { ast::TyKind::Err } else { ast::TyKind::Tup(ThinVec::new()) },
+            kind: ast::TyKind::Tup(ThinVec::new()),
             span: sp,
             tokens: None,
         })
@@ -611,7 +614,7 @@ impl MacResult for DummyResult {
     }
 
     fn make_ty(self: Box<DummyResult>) -> Option<P<ast::Ty>> {
-        Some(DummyResult::raw_ty(self.span, self.is_error))
+        Some(DummyResult::raw_ty(self.span))
     }
 
     fn make_arms(self: Box<DummyResult>) -> Option<SmallVec<[ast::Arm; 1]>> {
diff --git a/compiler/rustc_hir_typeck/src/_match.rs b/compiler/rustc_hir_typeck/src/_match.rs
index 0311aa94cd4..b0caf45b40a 100644
--- a/compiler/rustc_hir_typeck/src/_match.rs
+++ b/compiler/rustc_hir_typeck/src/_match.rs
@@ -79,7 +79,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             CoerceMany::with_coercion_sites(coerce_first, arms)
         };
 
-        let mut other_arms = vec![]; // Used only for diagnostics.
+        let mut prior_non_diverging_arms = vec![]; // Used only for diagnostics.
         let mut prior_arm = None;
         for arm in arms {
             if let Some(e) = &arm.guard {
@@ -118,9 +118,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         prior_arm_ty,
                         prior_arm_span,
                         scrut_span: scrut.span,
-                        scrut_hir_id: scrut.hir_id,
                         source: match_src,
-                        prior_arms: other_arms.clone(),
+                        prior_non_diverging_arms: prior_non_diverging_arms.clone(),
                         opt_suggest_box_span,
                     })),
                 ),
@@ -142,16 +141,16 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 false,
             );
 
-            other_arms.push(arm_span);
-            if other_arms.len() > 5 {
-                other_arms.remove(0);
-            }
-
             if !arm_ty.is_never() {
                 // When a match arm has type `!`, then it doesn't influence the expected type for
                 // the following arm. If all of the prior arms are `!`, then the influence comes
                 // from elsewhere and we shouldn't point to any previous arm.
                 prior_arm = Some((arm_block_id, arm_ty, arm_span));
+
+                prior_non_diverging_arms.push(arm_span);
+                if prior_non_diverging_arms.len() > 5 {
+                    prior_non_diverging_arms.remove(0);
+                }
             }
         }
 
diff --git a/compiler/rustc_infer/src/infer/error_reporting/mod.rs b/compiler/rustc_infer/src/infer/error_reporting/mod.rs
index b953b25d6c4..104bf4a5be8 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/mod.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/mod.rs
@@ -777,10 +777,9 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                 prior_arm_span,
                 prior_arm_ty,
                 source,
-                ref prior_arms,
+                ref prior_non_diverging_arms,
                 opt_suggest_box_span,
                 scrut_span,
-                scrut_hir_id,
                 ..
             }) => match source {
                 hir::MatchSource::TryDesugar(scrut_hir_id) => {
@@ -817,12 +816,12 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                     });
                     let source_map = self.tcx.sess.source_map();
                     let mut any_multiline_arm = source_map.is_multiline(arm_span);
-                    if prior_arms.len() <= 4 {
-                        for sp in prior_arms {
+                    if prior_non_diverging_arms.len() <= 4 {
+                        for sp in prior_non_diverging_arms {
                             any_multiline_arm |= source_map.is_multiline(*sp);
                             err.span_label(*sp, format!("this is found to be of type `{t}`"));
                         }
-                    } else if let Some(sp) = prior_arms.last() {
+                    } else if let Some(sp) = prior_non_diverging_arms.last() {
                         any_multiline_arm |= source_map.is_multiline(*sp);
                         err.span_label(
                             *sp,
@@ -848,24 +847,15 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                     ) {
                         err.subdiagnostic(subdiag);
                     }
-                    if let hir::Node::Expr(m) = self.tcx.parent_hir_node(scrut_hir_id)
-                        && let hir::Node::Stmt(stmt) = self.tcx.parent_hir_node(m.hir_id)
-                        && let hir::StmtKind::Expr(_) = stmt.kind
-                    {
-                        err.span_suggestion_verbose(
-                            stmt.span.shrink_to_hi(),
-                            "consider using a semicolon here, but this will discard any values \
-                             in the match arms",
-                            ";",
-                            Applicability::MaybeIncorrect,
-                        );
-                    }
                     if let Some(ret_sp) = opt_suggest_box_span {
                         // Get return type span and point to it.
                         self.suggest_boxing_for_return_impl_trait(
                             err,
                             ret_sp,
-                            prior_arms.iter().chain(std::iter::once(&arm_span)).copied(),
+                            prior_non_diverging_arms
+                                .iter()
+                                .chain(std::iter::once(&arm_span))
+                                .copied(),
                         );
                     }
                 }
diff --git a/compiler/rustc_infer/src/infer/error_reporting/suggest.rs b/compiler/rustc_infer/src/infer/error_reporting/suggest.rs
index 248e1c0fcc8..c6f6c32fe60 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/suggest.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/suggest.rs
@@ -203,10 +203,10 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                     })
                 }
                 ObligationCauseCode::MatchExpressionArm(box MatchExpressionArmCause {
-                    prior_arms,
+                    prior_non_diverging_arms,
                     ..
                 }) => {
-                    if let [.., arm_span] = &prior_arms[..] {
+                    if let [.., arm_span] = &prior_non_diverging_arms[..] {
                         Some(ConsiderAddingAwait::BothFuturesSugg {
                             first: arm_span.shrink_to_hi(),
                             second: exp_span.shrink_to_hi(),
@@ -234,11 +234,14 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                     Some(ConsiderAddingAwait::FutureSugg { span: then_span.shrink_to_hi() })
                 }
                 ObligationCauseCode::MatchExpressionArm(box MatchExpressionArmCause {
-                    ref prior_arms,
+                    ref prior_non_diverging_arms,
                     ..
                 }) => Some({
                     ConsiderAddingAwait::FutureSuggMultiple {
-                        spans: prior_arms.iter().map(|arm| arm.shrink_to_hi()).collect(),
+                        spans: prior_non_diverging_arms
+                            .iter()
+                            .map(|arm| arm.shrink_to_hi())
+                            .collect(),
                     }
                 }),
                 _ => None,
diff --git a/compiler/rustc_middle/src/traits/mod.rs b/compiler/rustc_middle/src/traits/mod.rs
index 8e5f026b4c2..119e0a49acf 100644
--- a/compiler/rustc_middle/src/traits/mod.rs
+++ b/compiler/rustc_middle/src/traits/mod.rs
@@ -569,9 +569,8 @@ pub struct MatchExpressionArmCause<'tcx> {
     pub prior_arm_ty: Ty<'tcx>,
     pub prior_arm_span: Span,
     pub scrut_span: Span,
-    pub scrut_hir_id: hir::HirId,
     pub source: hir::MatchSource,
-    pub prior_arms: Vec<Span>,
+    pub prior_non_diverging_arms: Vec<Span>,
     pub opt_suggest_box_span: Option<Span>,
 }
 
diff --git a/compiler/rustc_middle/src/ty/sty.rs b/compiler/rustc_middle/src/ty/sty.rs
index 66086ac87f1..a5817125267 100644
--- a/compiler/rustc_middle/src/ty/sty.rs
+++ b/compiler/rustc_middle/src/ty/sty.rs
@@ -2363,28 +2363,42 @@ impl<'tcx> Ty<'tcx> {
     }
 
     /// When we create a closure, we record its kind (i.e., what trait
-    /// it implements) into its `ClosureArgs` using a type
+    /// it implements, constrained by how it uses its borrows) into its
+    /// [`ty::ClosureArgs`] or [`ty::CoroutineClosureArgs`] using a type
     /// parameter. This is kind of a phantom type, except that the
     /// most convenient thing for us to are the integral types. This
     /// function converts such a special type into the closure
-    /// kind. To go the other way, use `closure_kind.to_ty(tcx)`.
+    /// kind. To go the other way, use [`Ty::from_closure_kind`].
     ///
     /// Note that during type checking, we use an inference variable
     /// to represent the closure kind, because it has not yet been
     /// inferred. Once upvar inference (in `rustc_hir_analysis/src/check/upvar.rs`)
-    /// is complete, that type variable will be unified.
+    /// is complete, that type variable will be unified with one of
+    /// the integral types.
     ///
-    /// To be noted that you can use [`ClosureArgs::kind()`] or [`CoroutineClosureArgs::kind()`]
-    /// to get the same information, which you can get by calling [`GenericArgs::as_closure()`]
-    /// or [`GenericArgs::as_coroutine_closure()`], depending on the type of the closure.
+    /// ```rust,ignore (snippet of compiler code)
+    /// if let TyKind::Closure(def_id, args) = closure_ty.kind()
+    ///     && let Some(closure_kind) = args.as_closure().kind_ty().to_opt_closure_kind()
+    /// {
+    ///     println!("{closure_kind:?}");
+    /// } else if let TyKind::CoroutineClosure(def_id, args) = closure_ty.kind()
+    ///     && let Some(closure_kind) = args.as_coroutine_closure().kind_ty().to_opt_closure_kind()
+    /// {
+    ///     println!("{closure_kind:?}");
+    /// }
+    /// ```
     ///
-    /// Otherwise, this method can be used as follows:
+    /// After upvar analysis, you should instead use [`ClosureArgs::kind()`]
+    /// or [`CoroutineClosureArgs::kind()`] to assert that the `ClosureKind`
+    /// has been constrained instead of manually calling this method.
     ///
     /// ```rust,ignore (snippet of compiler code)
-    /// let TyKind::Closure(def_id, [closure_fn_kind_ty, ..]) = closure_ty.kind()
-    ///     && let Some(closure_kind) = closure_fn_kind_ty.expect_ty().to_opt_closure_kind()
+    /// if let TyKind::Closure(def_id, args) = closure_ty.kind()
+    /// {
+    ///     println!("{:?}", args.as_closure().kind());
+    /// } else if let TyKind::CoroutineClosure(def_id, args) = closure_ty.kind()
     /// {
-    ///     // your code
+    ///     println!("{:?}", args.as_coroutine_closure().kind());
     /// }
     /// ```
     pub fn to_opt_closure_kind(self) -> Option<ty::ClosureKind> {
@@ -2406,7 +2420,8 @@ impl<'tcx> Ty<'tcx> {
         }
     }
 
-    /// Inverse of [`Ty::to_opt_closure_kind`].
+    /// Inverse of [`Ty::to_opt_closure_kind`]. See docs on that method
+    /// for explanation of the relationship between `Ty` and [`ty::ClosureKind`].
     pub fn from_closure_kind(tcx: TyCtxt<'tcx>, kind: ty::ClosureKind) -> Ty<'tcx> {
         match kind {
             ty::ClosureKind::Fn => tcx.types.i8,
diff --git a/compiler/rustc_mir_transform/src/lib.rs b/compiler/rustc_mir_transform/src/lib.rs
index b4fa7f3bea6..fb174192b84 100644
--- a/compiler/rustc_mir_transform/src/lib.rs
+++ b/compiler/rustc_mir_transform/src/lib.rs
@@ -653,7 +653,6 @@ fn inner_optimized_mir(tcx: TyCtxt<'_>, did: LocalDefId) -> Body<'_> {
     debug!("about to call mir_drops_elaborated...");
     let body = tcx.mir_drops_elaborated_and_const_checked(did).steal();
     let mut body = remap_mir_for_const_eval_select(tcx, body, hir::Constness::NotConst);
-    debug!("body: {:#?}", body);
 
     if body.tainted_by_errors.is_some() {
         return body;
diff --git a/compiler/rustc_mir_transform/src/remove_noop_landing_pads.rs b/compiler/rustc_mir_transform/src/remove_noop_landing_pads.rs
index 095119e2e3f..fb52bfa468a 100644
--- a/compiler/rustc_mir_transform/src/remove_noop_landing_pads.rs
+++ b/compiler/rustc_mir_transform/src/remove_noop_landing_pads.rs
@@ -15,7 +15,8 @@ impl<'tcx> MirPass<'tcx> for RemoveNoopLandingPads {
     }
 
     fn run_pass(&self, _tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
-        debug!("remove_noop_landing_pads({:?})", body);
+        let def_id = body.source.def_id();
+        debug!(?def_id);
         self.remove_nop_landing_pads(body)
     }
 }
@@ -81,8 +82,6 @@ impl RemoveNoopLandingPads {
     }
 
     fn remove_nop_landing_pads(&self, body: &mut Body<'_>) {
-        debug!("body: {:#?}", body);
-
         // Skip the pass if there are no blocks with a resume terminator.
         let has_resume = body
             .basic_blocks
diff --git a/compiler/rustc_parse/src/parser/diagnostics.rs b/compiler/rustc_parse/src/parser/diagnostics.rs
index 445d5b2ce79..69518287f38 100644
--- a/compiler/rustc_parse/src/parser/diagnostics.rs
+++ b/compiler/rustc_parse/src/parser/diagnostics.rs
@@ -46,14 +46,14 @@ use std::ops::{Deref, DerefMut};
 use thin_vec::{thin_vec, ThinVec};
 
 /// Creates a placeholder argument.
-pub(super) fn dummy_arg(ident: Ident) -> Param {
+pub(super) fn dummy_arg(ident: Ident, guar: ErrorGuaranteed) -> Param {
     let pat = P(Pat {
         id: ast::DUMMY_NODE_ID,
         kind: PatKind::Ident(BindingAnnotation::NONE, ident, None),
         span: ident.span,
         tokens: None,
     });
-    let ty = Ty { kind: TyKind::Err, span: ident.span, id: ast::DUMMY_NODE_ID, tokens: None };
+    let ty = Ty { kind: TyKind::Err(guar), span: ident.span, id: ast::DUMMY_NODE_ID, tokens: None };
     Param {
         attrs: AttrVec::default(),
         id: ast::DUMMY_NODE_ID,
@@ -1540,14 +1540,14 @@ impl<'a> Parser<'a> {
     pub(super) fn maybe_recover_from_question_mark(&mut self, ty: P<Ty>) -> P<Ty> {
         if self.token == token::Question {
             self.bump();
-            self.dcx().emit_err(QuestionMarkInType {
+            let guar = self.dcx().emit_err(QuestionMarkInType {
                 span: self.prev_token.span,
                 sugg: QuestionMarkInTypeSugg {
                     left: ty.span.shrink_to_lo(),
                     right: self.prev_token.span,
                 },
             });
-            self.mk_ty(ty.span.to(self.prev_token.span), TyKind::Err)
+            self.mk_ty(ty.span.to(self.prev_token.span), TyKind::Err(guar))
         } else {
             ty
         }
@@ -2304,8 +2304,8 @@ impl<'a> Parser<'a> {
 
     pub(super) fn recover_bad_self_param(&mut self, mut param: Param) -> PResult<'a, Param> {
         let span = param.pat.span;
-        param.ty.kind = TyKind::Err;
-        self.dcx().emit_err(SelfParamNotFirst { span });
+        let guar = self.dcx().emit_err(SelfParamNotFirst { span });
+        param.ty.kind = TyKind::Err(guar);
         Ok(param)
     }
 
@@ -2437,7 +2437,7 @@ impl<'a> Parser<'a> {
     pub(super) fn deduplicate_recovered_params_names(&self, fn_inputs: &mut ThinVec<Param>) {
         let mut seen_inputs = FxHashSet::default();
         for input in fn_inputs.iter_mut() {
-            let opt_ident = if let (PatKind::Ident(_, ident, _), TyKind::Err) =
+            let opt_ident = if let (PatKind::Ident(_, ident, _), TyKind::Err(_)) =
                 (&input.pat.kind, &input.ty.kind)
             {
                 Some(*ident)
@@ -2644,8 +2644,10 @@ impl<'a> Parser<'a> {
                         "::",
                         Applicability::MaybeIncorrect,
                     );
-                    err.emit();
-                    return Ok(GenericArg::Type(self.mk_ty(start.to(expr.span), TyKind::Err)));
+                    let guar = err.emit();
+                    return Ok(GenericArg::Type(
+                        self.mk_ty(start.to(expr.span), TyKind::Err(guar)),
+                    ));
                 } else if token::Comma == self.token.kind || self.token.kind.should_end_const_arg()
                 {
                     // Avoid the following output by checking that we consumed a full const arg:
diff --git a/compiler/rustc_parse/src/parser/item.rs b/compiler/rustc_parse/src/parser/item.rs
index 8050b34956c..a0605b8a44c 100644
--- a/compiler/rustc_parse/src/parser/item.rs
+++ b/compiler/rustc_parse/src/parser/item.rs
@@ -591,7 +591,23 @@ impl<'a> Parser<'a> {
         let ty_second = if self.token == token::DotDot {
             // We need to report this error after `cfg` expansion for compatibility reasons
             self.bump(); // `..`, do not add it to expected tokens
-            Some(self.mk_ty(self.prev_token.span, TyKind::Err))
+
+            // FIXME(nnethercote): AST validation later detects this
+            // `TyKind::Err` and emits an errors. So why the unchecked
+            // ErrorGuaranteed?
+            // - A `span_delayed_bug` doesn't work here, because rustfmt can
+            //   hit this path but then not hit the follow-up path in the AST
+            //   validator that issues the error, which results in ICEs.
+            // - `TyKind::Dummy` doesn't work, because it ends up reaching HIR
+            //   lowering, which results in ICEs. Changing `TyKind::Dummy` to
+            //   `TyKind::Err` during AST validation might fix that, but that's
+            //   not possible because AST validation doesn't allow mutability.
+            //
+            // #121072 will hopefully remove all this special handling of the
+            // obsolete `impl Trait for ..` and then this can go away.
+            #[allow(deprecated)]
+            let guar = rustc_errors::ErrorGuaranteed::unchecked_error_guaranteed();
+            Some(self.mk_ty(self.prev_token.span, TyKind::Err(guar)))
         } else if has_for || self.token.can_begin_type() {
             Some(self.parse_ty()?)
         } else {
@@ -2628,13 +2644,13 @@ impl<'a> Parser<'a> {
             p.recover_diff_marker();
             let snapshot = p.create_snapshot_for_diagnostic();
             let param = p.parse_param_general(req_name, first_param).or_else(|e| {
-                e.emit();
+                let guar = e.emit();
                 let lo = p.prev_token.span;
                 p.restore_snapshot(snapshot);
                 // Skip every token until next possible arg or end.
                 p.eat_to_tokens(&[&token::Comma, &token::CloseDelim(Delimiter::Parenthesis)]);
                 // Create a placeholder argument for proper arg count (issue #34264).
-                Ok(dummy_arg(Ident::new(kw::Empty, lo.to(p.prev_token.span))))
+                Ok(dummy_arg(Ident::new(kw::Empty, lo.to(p.prev_token.span)), guar))
             });
             // ...now that we've parsed the first argument, `self` is no longer allowed.
             first_param = false;
@@ -2671,8 +2687,8 @@ impl<'a> Parser<'a> {
                     return if let Some(ident) =
                         this.parameter_without_type(&mut err, pat, is_name_required, first_param)
                     {
-                        err.emit();
-                        Ok((dummy_arg(ident), TrailingToken::None))
+                        let guar = err.emit();
+                        Ok((dummy_arg(ident, guar), TrailingToken::None))
                     } else {
                         Err(err)
                     };
diff --git a/compiler/rustc_parse/src/parser/path.rs b/compiler/rustc_parse/src/parser/path.rs
index e7cad74b4dd..681039999a6 100644
--- a/compiler/rustc_parse/src/parser/path.rs
+++ b/compiler/rustc_parse/src/parser/path.rs
@@ -678,8 +678,9 @@ impl<'a> Parser<'a> {
                 c.into()
             }
             Some(GenericArg::Lifetime(lt)) => {
-                self.dcx().emit_err(errors::AssocLifetime { span, lifetime: lt.ident.span });
-                self.mk_ty(span, ast::TyKind::Err).into()
+                let guar =
+                    self.dcx().emit_err(errors::AssocLifetime { span, lifetime: lt.ident.span });
+                self.mk_ty(span, ast::TyKind::Err(guar)).into()
             }
             None => {
                 let after_eq = eq.shrink_to_hi();
@@ -779,7 +780,7 @@ impl<'a> Parser<'a> {
                     // type to determine if error recovery has occurred and if the input is not a
                     // syntactically valid type after all.
                     if let ast::TyKind::Slice(inner_ty) | ast::TyKind::Array(inner_ty, _) = &ty.kind
-                        && let ast::TyKind::Err = inner_ty.kind
+                        && let ast::TyKind::Err(_) = inner_ty.kind
                         && let Some(snapshot) = snapshot
                         && let Some(expr) =
                             self.recover_unbraced_const_arg_that_can_begin_ty(snapshot)
diff --git a/compiler/rustc_parse/src/parser/ty.rs b/compiler/rustc_parse/src/parser/ty.rs
index 157fb9e505a..f79f2a813b2 100644
--- a/compiler/rustc_parse/src/parser/ty.rs
+++ b/compiler/rustc_parse/src/parser/ty.rs
@@ -346,8 +346,10 @@ impl<'a> Parser<'a> {
                 AllowCVariadic::No => {
                     // FIXME(Centril): Should we just allow `...` syntactically
                     // anywhere in a type and use semantic restrictions instead?
-                    self.dcx().emit_err(NestedCVariadicType { span: lo.to(self.prev_token.span) });
-                    TyKind::Err
+                    let guar = self
+                        .dcx()
+                        .emit_err(NestedCVariadicType { span: lo.to(self.prev_token.span) });
+                    TyKind::Err(guar)
                 }
             }
         } else {
@@ -493,8 +495,8 @@ impl<'a> Parser<'a> {
             {
                 // Recover from `[LIT; EXPR]` and `[LIT]`
                 self.bump();
-                err.emit();
-                self.mk_ty(self.prev_token.span, TyKind::Err)
+                let guar = err.emit();
+                self.mk_ty(self.prev_token.span, TyKind::Err(guar))
             }
             Err(err) => return Err(err),
         };
diff --git a/compiler/rustc_passes/src/hir_stats.rs b/compiler/rustc_passes/src/hir_stats.rs
index d02e86dd456..96429bb7788 100644
--- a/compiler/rustc_passes/src/hir_stats.rs
+++ b/compiler/rustc_passes/src/hir_stats.rs
@@ -616,8 +616,9 @@ impl<'v> ast_visit::Visitor<'v> for StatCollector<'v> {
                 Infer,
                 ImplicitSelf,
                 MacCall,
-                Err,
-                CVarArgs
+                CVarArgs,
+                Dummy,
+                Err
             ]
         );
 
diff --git a/compiler/rustc_target/src/target_features.rs b/compiler/rustc_target/src/target_features.rs
index 04943fa3879..2b7ac68c21d 100644
--- a/compiler/rustc_target/src/target_features.rs
+++ b/compiler/rustc_target/src/target_features.rs
@@ -86,7 +86,7 @@ const ARM_ALLOWED_FEATURES: &[(&str, Stability)] = &[
 
 const AARCH64_ALLOWED_FEATURES: &[(&str, Stability)] = &[
     // tidy-alphabetical-start
-    // FEAT_AES
+    // FEAT_AES & FEAT_PMULL
     ("aes", Stable),
     // FEAT_BF16
     ("bf16", Stable),
@@ -124,7 +124,7 @@ const AARCH64_ALLOWED_FEATURES: &[(&str, Stability)] = &[
     ("lor", Stable),
     // FEAT_LSE
     ("lse", Stable),
-    // FEAT_MTE
+    // FEAT_MTE & FEAT_MTE2
     ("mte", Stable),
     // FEAT_AdvSimd & FEAT_FP
     ("neon", Stable),
@@ -138,7 +138,7 @@ const AARCH64_ALLOWED_FEATURES: &[(&str, Stability)] = &[
     ("pmuv3", Stable),
     // FEAT_RAND
     ("rand", Stable),
-    // FEAT_RAS
+    // FEAT_RAS & FEAT_RASv1p1
     ("ras", Stable),
     // FEAT_RCPC
     ("rcpc", Stable),
@@ -156,7 +156,7 @@ const AARCH64_ALLOWED_FEATURES: &[(&str, Stability)] = &[
     ("sm4", Stable),
     // FEAT_SPE
     ("spe", Stable),
-    // FEAT_SSBS
+    // FEAT_SSBS & FEAT_SSBS2
     ("ssbs", Stable),
     // FEAT_SVE
     ("sve", Stable),
diff --git a/compiler/rustc_trait_selection/messages.ftl b/compiler/rustc_trait_selection/messages.ftl
index 41db8059cbe..0dcba0e05f7 100644
--- a/compiler/rustc_trait_selection/messages.ftl
+++ b/compiler/rustc_trait_selection/messages.ftl
@@ -8,14 +8,16 @@ trait_selection_adjust_signature_remove_borrow = consider adjusting the signatur
         *[other] arguments
     }
 
-trait_selection_closure_fn_mut_label = closure is `FnMut` because it mutates the variable `{$place}` here
+trait_selection_async_closure_not_fn = async closure does not implement `{$kind}` because it captures state from its environment
 
-trait_selection_closure_fn_once_label = closure is `FnOnce` because it moves the variable `{$place}` out of its environment
+trait_selection_closure_fn_mut_label = closure is `{$trait_prefix}FnMut` because it mutates the variable `{$place}` here
 
-trait_selection_closure_kind_mismatch = expected a closure that implements the `{$expected}` trait, but this closure only implements `{$found}`
-    .label = this closure implements `{$found}`, not `{$expected}`
+trait_selection_closure_fn_once_label = closure is `{$trait_prefix}FnOnce` because it moves the variable `{$place}` out of its environment
 
-trait_selection_closure_kind_requirement = the requirement to implement `{$expected}` derives from here
+trait_selection_closure_kind_mismatch = expected a closure that implements the `{$trait_prefix}{$expected}` trait, but this closure only implements `{$trait_prefix}{$found}`
+    .label = this closure implements `{$trait_prefix}{$found}`, not `{$trait_prefix}{$expected}`
+
+trait_selection_closure_kind_requirement = the requirement to implement `{$trait_prefix}{$expected}` derives from here
 
 trait_selection_dump_vtable_entries = vtable entries for `{$trait_ref}`: {$entries}
 
diff --git a/compiler/rustc_trait_selection/src/errors.rs b/compiler/rustc_trait_selection/src/errors.rs
index 20cd573f46e..407fff03e15 100644
--- a/compiler/rustc_trait_selection/src/errors.rs
+++ b/compiler/rustc_trait_selection/src/errors.rs
@@ -135,6 +135,8 @@ pub struct ClosureKindMismatch {
     #[label(trait_selection_closure_kind_requirement)]
     pub cause_span: Span,
 
+    pub trait_prefix: &'static str,
+
     #[subdiagnostic]
     pub fn_once_label: Option<ClosureFnOnceLabel>,
 
@@ -157,3 +159,11 @@ pub struct ClosureFnMutLabel {
     pub span: Span,
     pub place: String,
 }
+
+#[derive(Diagnostic)]
+#[diag(trait_selection_async_closure_not_fn)]
+pub(crate) struct AsyncClosureNotFn {
+    #[primary_span]
+    pub span: Span,
+    pub kind: &'static str,
+}
diff --git a/compiler/rustc_trait_selection/src/traits/error_reporting/type_err_ctxt_ext.rs b/compiler/rustc_trait_selection/src/traits/error_reporting/type_err_ctxt_ext.rs
index 73effb33560..68b1a0d4e61 100644
--- a/compiler/rustc_trait_selection/src/traits/error_reporting/type_err_ctxt_ext.rs
+++ b/compiler/rustc_trait_selection/src/traits/error_reporting/type_err_ctxt_ext.rs
@@ -2,7 +2,9 @@
 
 use super::on_unimplemented::{AppendConstMessage, OnUnimplementedNote, TypeErrCtxtExt as _};
 use super::suggestions::{get_explanation_based_on_obligation, TypeErrCtxtExt as _};
-use crate::errors::{ClosureFnMutLabel, ClosureFnOnceLabel, ClosureKindMismatch};
+use crate::errors::{
+    AsyncClosureNotFn, ClosureFnMutLabel, ClosureFnOnceLabel, ClosureKindMismatch,
+};
 use crate::infer::error_reporting::{TyCategory, TypeAnnotationNeeded as ErrorCode};
 use crate::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
 use crate::infer::InferCtxtExt as _;
@@ -959,34 +961,102 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
     fn emit_specialized_closure_kind_error(
         &self,
         obligation: &PredicateObligation<'tcx>,
-        trait_ref: ty::PolyTraitRef<'tcx>,
+        mut trait_ref: ty::PolyTraitRef<'tcx>,
     ) -> Option<ErrorGuaranteed> {
-        let self_ty = trait_ref.self_ty().skip_binder();
-        if let ty::Closure(closure_def_id, closure_args) = *self_ty.kind()
-            && let Some(expected_kind) = self.tcx.fn_trait_kind_from_def_id(trait_ref.def_id())
-            && let Some(found_kind) = self.closure_kind(self_ty)
+        // If `AsyncFnKindHelper` is not implemented, that means that the closure kind
+        // doesn't extend the goal kind. This is worth reporting, but we can only do so
+        // if we actually know which closure this goal comes from, so look at the cause
+        // to see if we can extract that information.
+        if Some(trait_ref.def_id()) == self.tcx.lang_items().async_fn_kind_helper()
+            && let Some(found_kind) = trait_ref.skip_binder().args.type_at(0).to_opt_closure_kind()
+            && let Some(expected_kind) =
+                trait_ref.skip_binder().args.type_at(1).to_opt_closure_kind()
             && !found_kind.extends(expected_kind)
-            && let sig = closure_args.as_closure().sig()
-            && self.can_sub(
-                obligation.param_env,
-                trait_ref,
-                sig.map_bound(|sig| {
-                    ty::TraitRef::new(
-                        self.tcx,
-                        trait_ref.def_id(),
-                        [trait_ref.self_ty().skip_binder(), sig.inputs()[0]],
-                    )
-                }),
-            )
         {
-            let mut err =
-                self.report_closure_error(&obligation, closure_def_id, found_kind, expected_kind);
-            self.note_obligation_cause(&mut err, &obligation);
-            self.point_at_returns_when_relevant(&mut err, &obligation);
-            Some(err.emit())
-        } else {
-            None
+            if let Some((_, Some(parent))) = obligation.cause.code().parent() {
+                // If we have a derived obligation, then the parent will be a `AsyncFn*` goal.
+                trait_ref = parent.to_poly_trait_ref();
+            } else if let &ObligationCauseCode::FunctionArgumentObligation { arg_hir_id, .. } =
+                obligation.cause.code()
+                && let Some(typeck_results) = &self.typeck_results
+                && let ty::Closure(closure_def_id, _) | ty::CoroutineClosure(closure_def_id, _) =
+                    *typeck_results.node_type(arg_hir_id).kind()
+            {
+                // Otherwise, extract the closure kind from the obligation.
+                let mut err = self.report_closure_error(
+                    &obligation,
+                    closure_def_id,
+                    found_kind,
+                    expected_kind,
+                    "async ",
+                );
+                self.note_obligation_cause(&mut err, &obligation);
+                self.point_at_returns_when_relevant(&mut err, &obligation);
+                return Some(err.emit());
+            }
+        }
+
+        let self_ty = trait_ref.self_ty().skip_binder();
+
+        if let Some(expected_kind) = self.tcx.fn_trait_kind_from_def_id(trait_ref.def_id()) {
+            let (closure_def_id, found_args, by_ref_captures) = match *self_ty.kind() {
+                ty::Closure(def_id, args) => {
+                    (def_id, args.as_closure().sig().map_bound(|sig| sig.inputs()[0]), None)
+                }
+                ty::CoroutineClosure(def_id, args) => (
+                    def_id,
+                    args.as_coroutine_closure()
+                        .coroutine_closure_sig()
+                        .map_bound(|sig| sig.tupled_inputs_ty),
+                    Some(args.as_coroutine_closure().coroutine_captures_by_ref_ty()),
+                ),
+                _ => return None,
+            };
+
+            let expected_args = trait_ref.map_bound(|trait_ref| trait_ref.args.type_at(1));
+
+            // Verify that the arguments are compatible. If the signature is
+            // mismatched, then we have a totally different error to report.
+            if self.enter_forall(found_args, |found_args| {
+                self.enter_forall(expected_args, |expected_args| {
+                    !self.can_sub(obligation.param_env, expected_args, found_args)
+                })
+            }) {
+                return None;
+            }
+
+            if let Some(found_kind) = self.closure_kind(self_ty)
+                && !found_kind.extends(expected_kind)
+            {
+                let mut err = self.report_closure_error(
+                    &obligation,
+                    closure_def_id,
+                    found_kind,
+                    expected_kind,
+                    "",
+                );
+                self.note_obligation_cause(&mut err, &obligation);
+                self.point_at_returns_when_relevant(&mut err, &obligation);
+                return Some(err.emit());
+            }
+
+            // If the closure has captures, then perhaps the reason that the trait
+            // is unimplemented is because async closures don't implement `Fn`/`FnMut`
+            // if they have captures.
+            if let Some(by_ref_captures) = by_ref_captures
+                && let ty::FnPtr(sig) = by_ref_captures.kind()
+                && !sig.skip_binder().output().is_unit()
+            {
+                let mut err = self.tcx.dcx().create_err(AsyncClosureNotFn {
+                    span: self.tcx.def_span(closure_def_id),
+                    kind: expected_kind.as_str(),
+                });
+                self.note_obligation_cause(&mut err, &obligation);
+                self.point_at_returns_when_relevant(&mut err, &obligation);
+                return Some(err.emit());
+            }
         }
+        None
     }
 
     fn fn_arg_obligation(
@@ -1493,6 +1563,7 @@ pub(super) trait InferCtxtPrivExt<'tcx> {
         closure_def_id: DefId,
         found_kind: ty::ClosureKind,
         kind: ty::ClosureKind,
+        trait_prefix: &'static str,
     ) -> DiagnosticBuilder<'tcx>;
 
     fn report_cyclic_signature_error(
@@ -3376,6 +3447,7 @@ impl<'tcx> InferCtxtPrivExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
         closure_def_id: DefId,
         found_kind: ty::ClosureKind,
         kind: ty::ClosureKind,
+        trait_prefix: &'static str,
     ) -> DiagnosticBuilder<'tcx> {
         let closure_span = self.tcx.def_span(closure_def_id);
 
@@ -3384,6 +3456,7 @@ impl<'tcx> InferCtxtPrivExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
             expected: kind,
             found: found_kind,
             cause_span: obligation.cause.span,
+            trait_prefix,
             fn_once_label: None,
             fn_mut_label: None,
         };