Auto merge of #106025 - matthiaskrgr:rollup-vz5rqah, r=matthiaskrgr

Rollup of 6 pull requests

Successful merges:

 - #105837 (Don't ICE in `check_must_not_suspend_ty` for mismatched tuple arity)
 - #105932 (Correct branch-protection ModFlagBehavior for Aarch64 on LLVM-15)
 - #105960 (Various cleanups)
 - #105985 (Method chain nitpicks)
 - #105996 (Test that async blocks are `UnwindSafe`)
 - #106012 (Clarify that raw retags are not permitted in Mir)

Failed merges:

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

compiler/rustc_codegen_llvm/src/context.rs

@@ -280,29 +280,35 @@ pub unsafe fn create_module<'ll>(
     }
 
     if let Some(BranchProtection { bti, pac_ret }) = sess.opts.unstable_opts.branch_protection {
+        let behavior = if llvm_version >= (15, 0, 0) {
+            llvm::LLVMModFlagBehavior::Min
+        } else {
+            llvm::LLVMModFlagBehavior::Error
+        };
+
         if sess.target.arch == "aarch64" {
             llvm::LLVMRustAddModuleFlag(
                 llmod,
-                llvm::LLVMModFlagBehavior::Error,
+                behavior,
                 "branch-target-enforcement\0".as_ptr().cast(),
                 bti.into(),
             );
             llvm::LLVMRustAddModuleFlag(
                 llmod,
-                llvm::LLVMModFlagBehavior::Error,
+                behavior,
                 "sign-return-address\0".as_ptr().cast(),
                 pac_ret.is_some().into(),
             );
             let pac_opts = pac_ret.unwrap_or(PacRet { leaf: false, key: PAuthKey::A });
             llvm::LLVMRustAddModuleFlag(
                 llmod,
-                llvm::LLVMModFlagBehavior::Error,
+                behavior,
                 "sign-return-address-all\0".as_ptr().cast(),
                 pac_opts.leaf.into(),
             );
             llvm::LLVMRustAddModuleFlag(
                 llmod,
-                llvm::LLVMModFlagBehavior::Error,
+                behavior,
                 "sign-return-address-with-bkey\0".as_ptr().cast(),
                 u32::from(pac_opts.key == PAuthKey::B),
             );

compiler/rustc_codegen_llvm/src/llvm/ffi.rs

@@ -79,6 +79,7 @@ pub enum LLVMModFlagBehavior {
     Append = 5,
     AppendUnique = 6,
     Max = 7,
+    Min = 8,
 }
 
 // Consts for the LLVM CallConv type, pre-cast to usize.

compiler/rustc_const_eval/src/transform/validate.rs

@@ -9,8 +9,8 @@ use rustc_middle::mir::visit::{PlaceContext, Visitor};
 use rustc_middle::mir::{
     traversal, AggregateKind, BasicBlock, BinOp, Body, BorrowKind, CastKind, CopyNonOverlapping,
     Local, Location, MirPass, MirPhase, NonDivergingIntrinsic, Operand, Place, PlaceElem, PlaceRef,
-    ProjectionElem, RuntimePhase, Rvalue, SourceScope, Statement, StatementKind, Terminator,
+    ProjectionElem, RetagKind, RuntimePhase, Rvalue, SourceScope, Statement, StatementKind,
-    TerminatorKind, UnOp, START_BLOCK,
+    Terminator, TerminatorKind, UnOp, START_BLOCK,
 };
 use rustc_middle::ty::{self, InstanceDef, ParamEnv, Ty, TyCtxt, TypeVisitable};
 use rustc_mir_dataflow::impls::MaybeStorageLive;
@@ -667,10 +667,13 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
                     self.fail(location, "`Deinit`is not allowed until deaggregation");
                 }
             }
-            StatementKind::Retag(_, _) => {
+            StatementKind::Retag(kind, _) => {
                 // FIXME(JakobDegen) The validator should check that `self.mir_phase <
                 // DropsLowered`. However, this causes ICEs with generation of drop shims, which
                 // seem to fail to set their `MirPhase` correctly.
+                if *kind == RetagKind::Raw || *kind == RetagKind::TwoPhase {
+                    self.fail(location, format!("explicit `{:?}` is forbidden", kind));
+                }
             }
             StatementKind::StorageLive(..)
             | StatementKind::StorageDead(..)

compiler/rustc_hir_typeck/src/generator_interior/mod.rs

@@ -607,10 +607,7 @@ fn check_must_not_suspend_ty<'tcx>(
         ty::Tuple(fields) => {
             let mut has_emitted = false;
             let comps = match data.expr.map(|e| &e.kind) {
-                Some(hir::ExprKind::Tup(comps)) => {
+                Some(hir::ExprKind::Tup(comps)) if comps.len() == fields.len() => Some(comps),
-                    debug_assert_eq!(comps.len(), fields.len());
-                    Some(comps)
-                }
                 _ => None,
             };
             for (i, ty) in fields.iter().enumerate() {

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

@@ -170,6 +170,7 @@ impl<'hir> Map<'hir> {
     }
 
     #[inline]
+    #[track_caller]
     pub fn local_def_id(self, hir_id: HirId) -> LocalDefId {
         self.opt_local_def_id(hir_id).unwrap_or_else(|| {
             bug!(
@@ -310,6 +311,7 @@ impl<'hir> Map<'hir> {
         }
     }
 
+    #[track_caller]
     pub fn get_parent_node(self, hir_id: HirId) -> HirId {
         self.find_parent_node(hir_id)
             .unwrap_or_else(|| bug!("No parent for node {:?}", self.node_to_string(hir_id)))
@@ -334,12 +336,14 @@ impl<'hir> Map<'hir> {
     }
 
     /// Retrieves the `Node` corresponding to `id`, panicking if it cannot be found.
+    #[track_caller]
     pub fn get(self, id: HirId) -> Node<'hir> {
         self.find(id).unwrap_or_else(|| bug!("couldn't find hir id {} in the HIR map", id))
     }
 
     /// Retrieves the `Node` corresponding to `id`, panicking if it cannot be found.
     #[inline]
+    #[track_caller]
     pub fn get_by_def_id(self, id: LocalDefId) -> Node<'hir> {
         self.find_by_def_id(id).unwrap_or_else(|| bug!("couldn't find {:?} in the HIR map", id))
     }
@@ -377,6 +381,7 @@ impl<'hir> Map<'hir> {
         self.tcx.hir_owner_nodes(id.hir_id.owner).unwrap().bodies[&id.hir_id.local_id]
     }
 
+    #[track_caller]
     pub fn fn_decl_by_hir_id(self, hir_id: HirId) -> Option<&'hir FnDecl<'hir>> {
         if let Some(node) = self.find(hir_id) {
             node.fn_decl()
@@ -385,6 +390,7 @@ impl<'hir> Map<'hir> {
         }
     }
 
+    #[track_caller]
     pub fn fn_sig_by_hir_id(self, hir_id: HirId) -> Option<&'hir FnSig<'hir>> {
         if let Some(node) = self.find(hir_id) {
             node.fn_sig()
@@ -393,6 +399,7 @@ impl<'hir> Map<'hir> {
         }
     }
 
+    #[track_caller]
     pub fn enclosing_body_owner(self, hir_id: HirId) -> LocalDefId {
         for (_, node) in self.parent_iter(hir_id) {
             if let Some(body) = associated_body(node) {
@@ -408,7 +415,7 @@ impl<'hir> Map<'hir> {
     /// item (possibly associated), a closure, or a `hir::AnonConst`.
     pub fn body_owner(self, BodyId { hir_id }: BodyId) -> HirId {
         let parent = self.get_parent_node(hir_id);
-        assert!(self.find(parent).map_or(false, |n| is_body_owner(n, hir_id)));
+        assert!(self.find(parent).map_or(false, |n| is_body_owner(n, hir_id)), "{hir_id:?}");
         parent
     }
 
@@ -419,10 +426,11 @@ impl<'hir> Map<'hir> {
     /// Given a `LocalDefId`, returns the `BodyId` associated with it,
     /// if the node is a body owner, otherwise returns `None`.
     pub fn maybe_body_owned_by(self, id: LocalDefId) -> Option<BodyId> {
-        self.get_if_local(id.to_def_id()).map(associated_body).flatten()
+        self.find_by_def_id(id).and_then(associated_body)
     }
 
     /// Given a body owner's id, returns the `BodyId` associated with it.
+    #[track_caller]
     pub fn body_owned_by(self, id: LocalDefId) -> BodyId {
         self.maybe_body_owned_by(id).unwrap_or_else(|| {
             let hir_id = self.local_def_id_to_hir_id(id);

compiler/rustc_middle/src/mir/syntax.rs

@@ -320,8 +320,10 @@ pub enum StatementKind<'tcx> {
     /// <https://internals.rust-lang.org/t/stacked-borrows-an-aliasing-model-for-rust/8153/> for
     /// more details.
     ///
-    /// For code that is not specific to stacked borrows, you should consider retags to read
+    /// For code that is not specific to stacked borrows, you should consider retags to read and
-    /// and modify the place in an opaque way.
+    /// modify the place in an opaque way.
+    ///
+    /// Only `RetagKind::Default` and `RetagKind::FnEntry` are permitted.
     Retag(RetagKind, Box<Place<'tcx>>),
 
     /// Encodes a user's type ascription. These need to be preserved

compiler/rustc_middle/src/ty/generics.rs

@@ -70,14 +70,6 @@ impl GenericParamDef {
         }
     }
 
-    pub fn has_default(&self) -> bool {
-        match self.kind {
-            GenericParamDefKind::Type { has_default, .. }
-            | GenericParamDefKind::Const { has_default } => has_default,
-            GenericParamDefKind::Lifetime => false,
-        }
-    }
-
     pub fn is_anonymous_lifetime(&self) -> bool {
         match self.kind {
             GenericParamDefKind::Lifetime => {

compiler/rustc_middle/src/ty/subst.rs

@@ -348,7 +348,7 @@ impl<'tcx> InternalSubsts<'tcx> {
         substs.reserve(defs.params.len());
         for param in &defs.params {
             let kind = mk_kind(param, substs);
-            assert_eq!(param.index as usize, substs.len());
+            assert_eq!(param.index as usize, substs.len(), "{substs:#?}, {defs:#?}");
             substs.push(kind);
         }
     }

compiler/rustc_middle/src/ty/visit.rs

@@ -88,9 +88,11 @@ pub trait TypeVisitable<'tcx>: fmt::Debug + Clone {
         self.has_vars_bound_at_or_above(ty::INNERMOST)
     }
 
-    #[instrument(level = "trace", ret)]
     fn has_type_flags(&self, flags: TypeFlags) -> bool {
-        self.visit_with(&mut HasTypeFlagsVisitor { flags }).break_value() == Some(FoundFlags)
+        let res =
+            self.visit_with(&mut HasTypeFlagsVisitor { flags }).break_value() == Some(FoundFlags);
+        trace!(?self, ?flags, ?res, "has_type_flags");
+        res
     }
     fn has_projections(&self) -> bool {
         self.has_type_flags(TypeFlags::HAS_PROJECTION)
@@ -560,10 +562,8 @@ impl<'tcx> TypeVisitor<'tcx> for HasTypeFlagsVisitor {
     type BreakTy = FoundFlags;
 
     #[inline]
-    #[instrument(skip(self), level = "trace", ret)]
     fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
         let flags = t.flags();
-        trace!(t.flags=?t.flags());
         if flags.intersects(self.flags) {
             ControlFlow::Break(FoundFlags)
         } else {
@@ -572,10 +572,8 @@ impl<'tcx> TypeVisitor<'tcx> for HasTypeFlagsVisitor {
     }
 
     #[inline]
-    #[instrument(skip(self), level = "trace", ret)]
     fn visit_region(&mut self, r: ty::Region<'tcx>) -> ControlFlow<Self::BreakTy> {
         let flags = r.type_flags();
-        trace!(r.flags=?flags);
         if flags.intersects(self.flags) {
             ControlFlow::Break(FoundFlags)
         } else {
@@ -584,7 +582,6 @@ impl<'tcx> TypeVisitor<'tcx> for HasTypeFlagsVisitor {
     }
 
     #[inline]
-    #[instrument(level = "trace", ret)]
     fn visit_const(&mut self, c: ty::Const<'tcx>) -> ControlFlow<Self::BreakTy> {
         let flags = FlagComputation::for_const(c);
         trace!(r.flags=?flags);
@@ -596,14 +593,7 @@ impl<'tcx> TypeVisitor<'tcx> for HasTypeFlagsVisitor {
     }
 
     #[inline]
-    #[instrument(level = "trace", ret)]
     fn visit_predicate(&mut self, predicate: ty::Predicate<'tcx>) -> ControlFlow<Self::BreakTy> {
-        debug!(
-            "HasTypeFlagsVisitor: predicate={:?} predicate.flags={:?} self.flags={:?}",
-            predicate,
-            predicate.flags(),
-            self.flags
-        );
         if predicate.flags().intersects(self.flags) {
             ControlFlow::Break(FoundFlags)
         } else {

compiler/rustc_mir_build/src/build/custom/parse/instruction.rs

@@ -15,9 +15,6 @@ impl<'tcx, 'body> ParseCtxt<'tcx, 'body> {
             @call("mir_retag", args) => {
                 Ok(StatementKind::Retag(RetagKind::Default, Box::new(self.parse_place(args[0])?)))
             },
-            @call("mir_retag_raw", args) => {
-                Ok(StatementKind::Retag(RetagKind::Raw, Box::new(self.parse_place(args[0])?)))
-            },
             @call("mir_set_discriminant", args) => {
                 let place = self.parse_place(args[0])?;
                 let var = self.parse_integer_literal(args[1])? as u32;

compiler/rustc_trait_selection/src/traits/error_reporting/method_chain.rs

@@ -14,21 +14,27 @@ impl<'a, 'tcx> TypeRelation<'tcx> for CollectAllMismatches<'a, 'tcx> {
     fn tag(&self) -> &'static str {
         "CollectAllMismatches"
     }
+
     fn tcx(&self) -> TyCtxt<'tcx> {
         self.infcx.tcx
     }
+
     fn intercrate(&self) -> bool {
         false
     }
+
     fn param_env(&self) -> ty::ParamEnv<'tcx> {
         self.param_env
     }
+
     fn a_is_expected(&self) -> bool {
         true
-    } // irrelevant
+    }
+
     fn mark_ambiguous(&mut self) {
         bug!()
     }
+
     fn relate_with_variance<T: Relate<'tcx>>(
         &mut self,
         _: ty::Variance,
@@ -38,6 +44,7 @@ impl<'a, 'tcx> TypeRelation<'tcx> for CollectAllMismatches<'a, 'tcx> {
     ) -> RelateResult<'tcx, T> {
         self.relate(a, b)
     }
+
     fn regions(
         &mut self,
         a: ty::Region<'tcx>,
@@ -45,15 +52,20 @@ impl<'a, 'tcx> TypeRelation<'tcx> for CollectAllMismatches<'a, 'tcx> {
     ) -> RelateResult<'tcx, ty::Region<'tcx>> {
         Ok(a)
     }
+
     fn tys(&mut self, a: Ty<'tcx>, b: Ty<'tcx>) -> RelateResult<'tcx, Ty<'tcx>> {
-        if a == b || matches!(a.kind(), ty::Infer(_)) || matches!(b.kind(), ty::Infer(_)) {
+        self.infcx.probe(|_| {
-            return Ok(a);
+            if a.is_ty_infer() || b.is_ty_infer() {
-        }
+                Ok(a)
-        relate::super_relate_tys(self, a, b).or_else(|e| {
+            } else {
+                self.infcx.super_combine_tys(self, a, b).or_else(|e| {
                     self.errors.push(e);
                     Ok(a)
                 })
             }
+        })
+    }
+
     fn consts(
         &mut self,
         a: ty::Const<'tcx>,
@@ -64,6 +76,7 @@ impl<'a, 'tcx> TypeRelation<'tcx> for CollectAllMismatches<'a, 'tcx> {
         }
         relate::super_relate_consts(self, a, b) // could do something similar here for constants!
     }
+
     fn binders<T: Relate<'tcx>>(
         &mut self,
         a: ty::Binder<'tcx, T>,

compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs

@@ -335,7 +335,7 @@ pub trait TypeErrCtxtExt<'tcx> {
         err: &mut Diagnostic,
         trait_pred: ty::PolyTraitPredicate<'tcx>,
     );
-    fn function_argument_obligation(
+    fn note_function_argument_obligation(
         &self,
         arg_hir_id: HirId,
         err: &mut Diagnostic,
@@ -2909,7 +2909,7 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                 ref parent_code,
                 ..
             } => {
-                self.function_argument_obligation(
+                self.note_function_argument_obligation(
                     arg_hir_id,
                     err,
                     parent_code,
@@ -3141,23 +3141,20 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
             );
         }
     }
-    fn function_argument_obligation(
+    fn note_function_argument_obligation(
         &self,
         arg_hir_id: HirId,
         err: &mut Diagnostic,
         parent_code: &ObligationCauseCode<'tcx>,
         param_env: ty::ParamEnv<'tcx>,
-        predicate: ty::Predicate<'tcx>,
+        failed_pred: ty::Predicate<'tcx>,
         call_hir_id: HirId,
     ) {
         let tcx = self.tcx;
         let hir = tcx.hir();
-        if let Some(Node::Expr(expr)) = hir.find(arg_hir_id) {
+        if let Some(Node::Expr(expr)) = hir.find(arg_hir_id)
-            let parent_id = hir.get_parent_item(arg_hir_id);
+            && let Some(typeck_results) = &self.typeck_results
-            let typeck_results: &TypeckResults<'tcx> = match &self.typeck_results {
+        {
-                Some(t) if t.hir_owner == parent_id => t,
-                _ => self.tcx.typeck(parent_id.def_id),
-            };
             if let hir::Expr { kind: hir::ExprKind::Block(..), .. } = expr {
                 let expr = expr.peel_blocks();
                 let ty = typeck_results.expr_ty_adjusted_opt(expr).unwrap_or(tcx.ty_error());
@@ -3182,37 +3179,29 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
             let mut type_diffs = vec![];
 
             if let ObligationCauseCode::ExprBindingObligation(def_id, _, _, idx) = parent_code.deref()
-                && let predicates = self.tcx.predicates_of(def_id).instantiate_identity(self.tcx)
+                && let Some(node_substs) = typeck_results.node_substs_opt(call_hir_id)
-                && let Some(pred) = predicates.predicates.get(*idx)
+                && let where_clauses = self.tcx.predicates_of(def_id).instantiate(self.tcx, node_substs)
+                && let Some(where_pred) = where_clauses.predicates.get(*idx)
             {
-                if let Ok(trait_pred) = pred.kind().try_map_bound(|pred| match pred {
+                if let Some(where_pred) = where_pred.to_opt_poly_trait_pred()
-                    ty::PredicateKind::Clause(ty::Clause::Trait(trait_pred)) => Ok(trait_pred),
+                    && let Some(failed_pred) = failed_pred.to_opt_poly_trait_pred()
-                    _ => Err(()),
-                })
-                    && let Ok(trait_predicate) = predicate.kind().try_map_bound(|pred| match pred {
-                        ty::PredicateKind::Clause(ty::Clause::Trait(trait_pred)) => Ok(trait_pred),
-                        _ => Err(()),
-                    })
                 {
                     let mut c = CollectAllMismatches {
                         infcx: self.infcx,
                         param_env,
                         errors: vec![],
                     };
-                    if let Ok(_) = c.relate(trait_pred, trait_predicate) {
+                    if let Ok(_) = c.relate(where_pred, failed_pred) {
                         type_diffs = c.errors;
                     }
-                } else if let ty::PredicateKind::Clause(
+                } else if let Some(where_pred) = where_pred.to_opt_poly_projection_pred()
-                    ty::Clause::Projection(proj)
+                    && let Some(failed_pred) = failed_pred.to_opt_poly_projection_pred()
-                ) = pred.kind().skip_binder()
+                    && let Some(found) = failed_pred.skip_binder().term.ty()
-                    && let ty::PredicateKind::Clause(
-                        ty::Clause::Projection(projection)
-                    ) = predicate.kind().skip_binder()
                 {
                     type_diffs = vec![
                         Sorts(ty::error::ExpectedFound {
-                            expected: self.tcx.mk_ty(ty::Alias(ty::Projection, proj.projection_ty)),
+                            expected: self.tcx.mk_ty(ty::Alias(ty::Projection, where_pred.skip_binder().projection_ty)),
-                            found: projection.term.ty().unwrap(),
+                            found,
                         }),
                     ];
                 }
@@ -3227,9 +3216,9 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                 // If the expression we're calling on is a binding, we want to point at the
                 // `let` when talking about the type. Otherwise we'll point at every part
                 // of the method chain with the type.
-                self.point_at_chain(binding_expr, typeck_results, type_diffs, param_env, err);
+                self.point_at_chain(binding_expr, &typeck_results, type_diffs, param_env, err);
             } else {
-                self.point_at_chain(expr, typeck_results, type_diffs, param_env, err);
+                self.point_at_chain(expr, &typeck_results, type_diffs, param_env, err);
             }
         }
         let call_node = hir.find(call_hir_id);

library/core/src/const_closure.rs

@@ -51,7 +51,7 @@ macro_rules! impl_fn_mut_tuple {
         impl<'a, $($var,)* ClosureArguments, Function, ClosureReturnValue> const
             FnOnce<ClosureArguments> for ConstFnMutClosure<($(&'a mut $var),*), Function>
         where
-            Function: ~const Fn(($(&mut $var),*), ClosureArguments) -> ClosureReturnValue+ ~const Destruct,
+            Function: ~const Fn(($(&mut $var),*), ClosureArguments) -> ClosureReturnValue + ~const Destruct,
         {
             type Output = ClosureReturnValue;
 
@@ -64,7 +64,7 @@ macro_rules! impl_fn_mut_tuple {
         impl<'a, $($var,)* ClosureArguments, Function, ClosureReturnValue> const
             FnMut<ClosureArguments> for ConstFnMutClosure<($(&'a mut $var),*), Function>
         where
-            Function: ~const Fn(($(&mut $var),*), ClosureArguments)-> ClosureReturnValue,
+            Function: ~const Fn(($(&mut $var),*), ClosureArguments)-> ClosureReturnValue + ~const Destruct,
         {
             extern "rust-call" fn call_mut(&mut self, args: ClosureArguments) -> Self::Output {
                 #[allow(non_snake_case)]

library/core/src/hash/mod.rs

@@ -199,7 +199,7 @@ pub trait Hash {
     /// println!("Hash is {:x}!", hasher.finish());
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
-    fn hash<H: Hasher>(&self, state: &mut H);
+    fn hash<H: ~const Hasher>(&self, state: &mut H);
 
     /// Feeds a slice of this type into the given [`Hasher`].
     ///
@@ -980,7 +980,7 @@ mod impls {
     #[rustc_const_unstable(feature = "const_hash", issue = "104061")]
     impl<T: ?Sized + ~const Hash> const Hash for &mut T {
         #[inline]
-        fn hash<H: Hasher>(&self, state: &mut H) {
+        fn hash<H: ~const Hasher>(&self, state: &mut H) {
             (**self).hash(state);
         }
     }

library/core/src/intrinsics/mir.rs

@@ -259,7 +259,6 @@ define!("mir_drop", fn Drop<T>(place: T, goto: BasicBlock));
 define!("mir_drop_and_replace", fn DropAndReplace<T>(place: T, value: T, goto: BasicBlock));
 define!("mir_call", fn Call<T>(place: T, goto: BasicBlock, call: T));
 define!("mir_retag", fn Retag<T>(place: T));
-define!("mir_retag_raw", fn RetagRaw<T>(place: T));
 define!("mir_move", fn Move<T>(place: T) -> T);
 define!("mir_static", fn Static<T>(s: T) -> &'static T);
 define!("mir_static_mut", fn StaticMut<T>(s: T) -> *mut T);

library/core/src/ops/index.rs

@@ -165,7 +165,7 @@ see chapter in The Book <https://doc.rust-lang.org/book/ch08-02-strings.html#ind
 #[doc(alias = "]")]
 #[doc(alias = "[]")]
 #[const_trait]
-pub trait IndexMut<Idx: ?Sized>: Index<Idx> {
+pub trait IndexMut<Idx: ?Sized>: ~const Index<Idx> {
     /// Performs the mutable indexing (`container[index]`) operation.
     ///
     /// # Panics

src/test/mir-opt/building/custom/references.immut_ref.built.after.mir

@@ -6,9 +6,8 @@ fn immut_ref(_1: &i32) -> &i32 {
 
     bb0: {
         _2 = &raw const (*_1);           // scope 0 at $DIR/references.rs:+5:13: +5:29
-        Retag([raw] _2);                 // scope 0 at $DIR/references.rs:+6:13: +6:24
+        _0 = &(*_2);                     // scope 0 at $DIR/references.rs:+6:13: +6:23
-        _0 = &(*_2);                     // scope 0 at $DIR/references.rs:+7:13: +7:23
+        Retag(_0);                       // scope 0 at $DIR/references.rs:+7:13: +7:23
-        Retag(_0);                       // scope 0 at $DIR/references.rs:+8:13: +8:23
+        return;                          // scope 0 at $DIR/references.rs:+8:13: +8:21
-        return;                          // scope 0 at $DIR/references.rs:+9:13: +9:21
     }
 }

src/test/mir-opt/building/custom/references.mut_ref.built.after.mir

@@ -6,9 +6,8 @@ fn mut_ref(_1: &mut i32) -> &mut i32 {
 
     bb0: {
         _2 = &raw mut (*_1);             // scope 0 at $DIR/references.rs:+5:13: +5:33
-        Retag([raw] _2);                 // scope 0 at $DIR/references.rs:+6:13: +6:24
+        _0 = &mut (*_2);                 // scope 0 at $DIR/references.rs:+6:13: +6:26
-        _0 = &mut (*_2);                 // scope 0 at $DIR/references.rs:+7:13: +7:26
+        Retag(_0);                       // scope 0 at $DIR/references.rs:+7:13: +7:23
-        Retag(_0);                       // scope 0 at $DIR/references.rs:+8:13: +8:23
+        return;                          // scope 0 at $DIR/references.rs:+8:13: +8:21
-        return;                          // scope 0 at $DIR/references.rs:+9:13: +9:21
     }
 }

src/test/mir-opt/building/custom/references.rs

@@ -12,7 +12,6 @@ pub fn mut_ref(x: &mut i32) -> &mut i32 {
 
         {
             t = addr_of_mut!(*x);
-            RetagRaw(t);
             RET = &mut *t;
             Retag(RET);
             Return()
@@ -28,7 +27,6 @@ pub fn immut_ref(x: &i32) -> &i32 {
 
         {
             t = addr_of!(*x);
-            RetagRaw(t);
             RET = & *t;
             Retag(RET);
             Return()

src/test/ui/async-await/async-is-unwindsafe.rs

@@ -0,0 +1,30 @@
+// edition:2018
+
+fn is_unwindsafe(_: impl std::panic::UnwindSafe) {}
+
+fn main() {
+    // A normal future created by an async block takes a `&mut Context<'_>` argument.
+    // That should not leak through to the whole async block.
+    is_unwindsafe(async {
+        async {}.await; // this needs an inner await point
+    });
+
+    is_unwindsafe(async {
+        //~^ ERROR the type `&mut Context<'_>` may not be safely transferred across an unwind boundary
+        use std::ptr::null;
+        use std::task::{Context, RawWaker, RawWakerVTable, Waker};
+        let waker = unsafe {
+            Waker::from_raw(RawWaker::new(
+                null(),
+                &RawWakerVTable::new(|_| todo!(), |_| todo!(), |_| todo!(), |_| todo!()),
+            ))
+        };
+        let mut cx = Context::from_waker(&waker);
+        let cx_ref = &mut cx;
+
+        async {}.await; // this needs an inner await point
+
+        // in this case, `&mut Context<'_>` is *truly* alive across an await point
+        drop(cx_ref);
+    });
+}

src/test/ui/async-await/async-is-unwindsafe.stderr

@@ -0,0 +1,38 @@
+error[E0277]: the type `&mut Context<'_>` may not be safely transferred across an unwind boundary
+  --> $DIR/async-is-unwindsafe.rs:12:19
+   |
+LL |       is_unwindsafe(async {
+   |  ___________________^
+LL | |
+LL | |         use std::ptr::null;
+LL | |         use std::task::{Context, RawWaker, RawWakerVTable, Waker};
+...  |
+LL | |         drop(cx_ref);
+LL | |     });
+   | |     ^
+   | |     |
+   | |_____`&mut Context<'_>` may not be safely transferred across an unwind boundary
+   |       within this `[async block@$DIR/async-is-unwindsafe.rs:12:19: 29:6]`
+   |
+   = help: within `[async block@$DIR/async-is-unwindsafe.rs:12:19: 29:6]`, the trait `UnwindSafe` is not implemented for `&mut Context<'_>`
+   = note: `UnwindSafe` is implemented for `&std::task::Context<'_>`, but not for `&mut std::task::Context<'_>`
+note: future does not implement `UnwindSafe` as this value is used across an await
+  --> $DIR/async-is-unwindsafe.rs:25:17
+   |
+LL |         let cx_ref = &mut cx;
+   |             ------ has type `&mut Context<'_>` which does not implement `UnwindSafe`
+LL |
+LL |         async {}.await; // this needs an inner await point
+   |                 ^^^^^^ await occurs here, with `cx_ref` maybe used later
+...
+LL |     });
+   |     - `cx_ref` is later dropped here
+note: required by a bound in `is_unwindsafe`
+  --> $DIR/async-is-unwindsafe.rs:3:26
+   |
+LL | fn is_unwindsafe(_: impl std::panic::UnwindSafe) {}
+   |                          ^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `is_unwindsafe`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0277`.

src/test/ui/iterators/invalid-iterator-chain.stderr

@@ -52,14 +52,14 @@ LL |             .sum::<i32>(),
              <i32 as Sum<&'a i32>>
              <i32 as Sum>
 note: the method call chain might not have had the expected associated types
-  --> $DIR/invalid-iterator-chain.rs:20:14
+  --> $DIR/invalid-iterator-chain.rs:25:14
    |
 LL |         vec![0, 1]
    |         ---------- this expression has type `Vec<{integer}>`
 LL |             .iter()
    |              ------ `Iterator::Item` is `&{integer}` here
 LL |             .map(|x| x * 2)
-   |              ^^^^^^^^^^^^^^ `Iterator::Item` changed to `{integer}` here
+   |              -------------- `Iterator::Item` changed to `{integer}` here
 LL |             .map(|x| x as f64)
    |              ----------------- `Iterator::Item` changed to `f64` here
 LL |             .map(|x| x as i64)
@@ -84,14 +84,14 @@ LL |             .sum::<i32>(),
              <i32 as Sum<&'a i32>>
              <i32 as Sum>
 note: the method call chain might not have had the expected associated types
-  --> $DIR/invalid-iterator-chain.rs:32:14
+  --> $DIR/invalid-iterator-chain.rs:33:14
    |
 LL |         vec![0, 1]
    |         ---------- this expression has type `Vec<{integer}>`
 LL |             .iter()
    |              ------ `Iterator::Item` is `&{integer}` here
 LL |             .map(|x| x * 2)
-   |              ^^^^^^^^^^^^^^ `Iterator::Item` changed to `{integer}` here
+   |              -------------- `Iterator::Item` changed to `{integer}` here
 LL |             .map(|x| x as f64)
    |              ^^^^^^^^^^^^^^^^^ `Iterator::Item` changed to `f64` here
 LL |             .filter(|x| *x > 0.0)

src/test/ui/lint/must_not_suspend/tuple-mismatch.rs

@@ -0,0 +1,9 @@
+#![feature(generators)]
+
+fn main() {
+    let _generator = || {
+        yield ((), ((), ()));
+        yield ((), ());
+        //~^ ERROR mismatched types
+    };
+}

src/test/ui/lint/must_not_suspend/tuple-mismatch.stderr

@@ -0,0 +1,12 @@
+error[E0308]: mismatched types
+  --> $DIR/tuple-mismatch.rs:6:20
+   |
+LL |         yield ((), ());
+   |                    ^^ expected tuple, found `()`
+   |
+   = note:  expected tuple `((), ())`
+           found unit type `()`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0308`.