Rollup of 11 pull requests

compiler/rustc_ast_lowering/src/expr.rs

@@ -16,7 +16,7 @@ use rustc_hir::def::Res;
 use rustc_hir::definitions::DefPathData;
 use rustc_session::errors::report_lit_error;
 use rustc_span::source_map::{respan, DesugaringKind, Span, Spanned};
-use rustc_span::symbol::{sym, Ident};
+use rustc_span::symbol::{kw, sym, Ident};
 use rustc_span::DUMMY_SP;
 use thin_vec::thin_vec;
 
@@ -592,14 +592,38 @@ impl<'hir> LoweringContext<'_, 'hir> {
     ) -> hir::ExprKind<'hir> {
         let output = ret_ty.unwrap_or_else(|| hir::FnRetTy::DefaultReturn(self.lower_span(span)));
 
-        // Resume argument type: `ResumeTy`
-        let unstable_span =
-            self.mark_span_with_reason(DesugaringKind::Async, span, self.allow_gen_future.clone());
-        let resume_ty = hir::QPath::LangItem(hir::LangItem::ResumeTy, unstable_span, None);
+        // Resume argument type, which should be `&mut Context<'_>`.
+        // NOTE: Using the `'static` lifetime here is technically cheating.
+        // The `Future::poll` argument really is `&'a mut Context<'b>`, but we cannot
+        // express the fact that we are not storing it across yield-points yet,
+        // and we would thus run into lifetime errors.
+        // See <https://github.com/rust-lang/rust/issues/68923>.
+        // Our lowering makes sure we are not mis-using the `_task_context` input type
+        // in the sense that we are indeed not using it across yield points. We
+        // get a fresh `&mut Context` for each resume / call of `Future::poll`.
+        // This "cheating" was previously done with a `ResumeTy` that contained a raw
+        // pointer, and a `get_context` accessor that pulled the `Context` lifetimes
+        // out of thin air.
+        let context_lifetime_ident = Ident::with_dummy_span(kw::StaticLifetime);
+        let context_lifetime = self.arena.alloc(hir::Lifetime {
+            hir_id: self.next_id(),
+            ident: context_lifetime_ident,
+            res: hir::LifetimeName::Static,
+        });
+        let context_path =
+            hir::QPath::LangItem(hir::LangItem::Context, self.lower_span(span), None);
+        let context_ty = hir::MutTy {
+            ty: self.arena.alloc(hir::Ty {
+                hir_id: self.next_id(),
+                kind: hir::TyKind::Path(context_path),
+                span: self.lower_span(span),
+            }),
+            mutbl: hir::Mutability::Mut,
+        };
         let input_ty = hir::Ty {
             hir_id: self.next_id(),
-            kind: hir::TyKind::Path(resume_ty),
-            span: unstable_span,
+            kind: hir::TyKind::Rptr(context_lifetime, context_ty),
+            span: self.lower_span(span),
         };
 
         // The closure/generator `FnDecl` takes a single (resume) argument of type `input_ty`.
@@ -710,7 +734,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
     ///     mut __awaitee => loop {
     ///         match unsafe { ::std::future::Future::poll(
     ///             <::std::pin::Pin>::new_unchecked(&mut __awaitee),
-    ///             ::std::future::get_context(task_context),
+    ///             task_context,
     ///         ) } {
     ///             ::std::task::Poll::Ready(result) => break result,
     ///             ::std::task::Poll::Pending => {}
@@ -751,7 +775,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
         // unsafe {
         //     ::std::future::Future::poll(
         //         ::std::pin::Pin::new_unchecked(&mut __awaitee),
-        //         ::std::future::get_context(task_context),
+        //         task_context,
         //     )
         // }
         let poll_expr = {
@@ -769,16 +793,10 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 arena_vec![self; ref_mut_awaitee],
                 Some(expr_hir_id),
             );
-            let get_context = self.expr_call_lang_item_fn_mut(
-                gen_future_span,
-                hir::LangItem::GetContext,
-                arena_vec![self; task_context],
-                Some(expr_hir_id),
-            );
             let call = self.expr_call_lang_item_fn(
                 span,
                 hir::LangItem::FuturePoll,
-                arena_vec![self; new_unchecked, get_context],
+                arena_vec![self; new_unchecked, task_context],
                 Some(expr_hir_id),
             );
             self.arena.alloc(self.expr_unsafe(call))

compiler/rustc_borrowck/src/invalidation.rs

@@ -106,7 +106,7 @@ impl<'cx, 'tcx> Visitor<'tcx> for InvalidationGenerator<'cx, 'tcx> {
         self.check_activations(location);
 
         match &terminator.kind {
-            TerminatorKind::SwitchInt { ref discr, switch_ty: _, targets: _ } => {
+            TerminatorKind::SwitchInt { ref discr, targets: _ } => {
                 self.consume_operand(location, discr);
             }
             TerminatorKind::Drop { place: drop_place, target: _, unwind: _ } => {

compiler/rustc_borrowck/src/lib.rs

@@ -644,7 +644,7 @@ impl<'cx, 'tcx> rustc_mir_dataflow::ResultsVisitor<'cx, 'tcx> for MirBorrowckCtx
         self.check_activations(loc, span, flow_state);
 
         match term.kind {
-            TerminatorKind::SwitchInt { ref discr, switch_ty: _, targets: _ } => {
+            TerminatorKind::SwitchInt { ref discr, targets: _ } => {
                 self.consume_operand(loc, (discr, span), flow_state);
             }
             TerminatorKind::Drop { place, target: _, unwind: _ } => {

compiler/rustc_borrowck/src/type_check/mod.rs

@@ -1360,25 +1360,10 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                     );
                 }
             }
-            TerminatorKind::SwitchInt { ref discr, switch_ty, .. } => {
+            TerminatorKind::SwitchInt { ref discr, .. } => {
                 self.check_operand(discr, term_location);
 
-                let discr_ty = discr.ty(body, tcx);
-                if let Err(terr) = self.sub_types(
-                    discr_ty,
-                    switch_ty,
-                    term_location.to_locations(),
-                    ConstraintCategory::Assignment,
-                ) {
-                    span_mirbug!(
-                        self,
-                        term,
-                        "bad SwitchInt ({:?} on {:?}): {:?}",
-                        switch_ty,
-                        discr_ty,
-                        terr
-                    );
-                }
+                let switch_ty = discr.ty(body, tcx);
                 if !switch_ty.is_integral() && !switch_ty.is_char() && !switch_ty.is_bool() {
                     span_mirbug!(self, term, "bad SwitchInt discr ty {:?}", switch_ty);
                 }

compiler/rustc_codegen_cranelift/src/base.rs

@@ -372,8 +372,10 @@ fn codegen_fn_body(fx: &mut FunctionCx<'_, '_, '_>, start_block: Block) {
                 }
             }
 
-            TerminatorKind::SwitchInt { discr, switch_ty, targets } => {
-                let discr = codegen_operand(fx, discr).load_scalar(fx);
+            TerminatorKind::SwitchInt { discr, targets } => {
+                let discr = codegen_operand(fx, discr);
+                let switch_ty = discr.layout().ty;
+                let discr = discr.load_scalar(fx);
 
                 let use_bool_opt = switch_ty.kind() == fx.tcx.types.bool.kind()
                     || (targets.iter().count() == 1 && targets.iter().next().unwrap().0 == 0);

compiler/rustc_codegen_ssa/src/mir/block.rs

@@ -307,12 +307,10 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         helper: TerminatorCodegenHelper<'tcx>,
         bx: &mut Bx,
         discr: &mir::Operand<'tcx>,
-        switch_ty: Ty<'tcx>,
         targets: &SwitchTargets,
     ) {
         let discr = self.codegen_operand(bx, &discr);
-        // `switch_ty` is redundant, sanity-check that.
-        assert_eq!(discr.layout.ty, switch_ty);
+        let switch_ty = discr.layout.ty;
         let mut target_iter = targets.iter();
         if target_iter.len() == 1 {
             // If there are two targets (one conditional, one fallback), emit `br` instead of
@@ -1293,8 +1291,8 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 helper.funclet_br(self, bx, target, mergeable_succ())
             }
 
-            mir::TerminatorKind::SwitchInt { ref discr, switch_ty, ref targets } => {
-                self.codegen_switchint_terminator(helper, bx, discr, switch_ty, targets);
+            mir::TerminatorKind::SwitchInt { ref discr, ref targets } => {
+                self.codegen_switchint_terminator(helper, bx, discr, targets);
                 MergingSucc::False
             }
 

compiler/rustc_const_eval/src/const_eval/machine.rs

@@ -240,7 +240,7 @@ impl<'mir, 'tcx: 'mir> CompileTimeEvalContext<'mir, 'tcx> {
                     let align = ImmTy::from_uint(target_align, args[1].layout).into();
                     let fn_abi = self.fn_abi_of_instance(instance, ty::List::empty())?;
 
-                    // We replace the entire entire function call with a "tail call".
+                    // We replace the entire function call with a "tail call".
                     // Note that this happens before the frame of the original function
                     // is pushed on the stack.
                     self.eval_fn_call(

compiler/rustc_const_eval/src/interpret/eval_context.rs

@@ -676,6 +676,10 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         return_to_block: StackPopCleanup,
     ) -> InterpResult<'tcx> {
         trace!("body: {:#?}", body);
+        // Clobber previous return place contents, nobody is supposed to be able to see them any more
+        // This also checks dereferenceable, but not align. We rely on all constructed places being
+        // sufficiently aligned (in particular we rely on `deref_operand` checking alignment).
+        self.write_uninit(return_place)?;
         // first push a stack frame so we have access to the local substs
         let pre_frame = Frame {
             body,

compiler/rustc_const_eval/src/interpret/terminator.rs

@@ -29,10 +29,9 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
 
             Goto { target } => self.go_to_block(target),
 
-            SwitchInt { ref discr, ref targets, switch_ty } => {
+            SwitchInt { ref discr, ref targets } => {
                 let discr = self.read_immediate(&self.eval_operand(discr, None)?)?;
                 trace!("SwitchInt({:?})", *discr);
-                assert_eq!(discr.layout.ty, switch_ty);
 
                 // Branch to the `otherwise` case by default, if no match is found.
                 let mut target_block = targets.otherwise();

compiler/rustc_const_eval/src/transform/validate.rs

@@ -682,17 +682,8 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
             TerminatorKind::Goto { target } => {
                 self.check_edge(location, *target, EdgeKind::Normal);
             }
-            TerminatorKind::SwitchInt { targets, switch_ty, discr } => {
-                let ty = discr.ty(&self.body.local_decls, self.tcx);
-                if ty != *switch_ty {
-                    self.fail(
-                        location,
-                        format!(
-                            "encountered `SwitchInt` terminator with type mismatch: {:?} != {:?}",
-                            ty, switch_ty,
-                        ),
-                    );
-                }
+            TerminatorKind::SwitchInt { targets, discr } => {
+                let switch_ty = discr.ty(&self.body.local_decls, self.tcx);
 
                 let target_width = self.tcx.sess.target.pointer_width;
 

compiler/rustc_hir/src/lang_items.rs

@@ -286,10 +286,9 @@ language_item_table! {
 
     // FIXME(swatinem): the following lang items are used for async lowering and
     // should become obsolete eventually.
-    ResumeTy,                sym::ResumeTy,            resume_ty,                  Target::Struct,         GenericRequirement::None;
     IdentityFuture,          sym::identity_future,     identity_future_fn,         Target::Fn,             GenericRequirement::None;
-    GetContext,              sym::get_context,         get_context_fn,             Target::Fn,             GenericRequirement::None;
 
+    Context,                 sym::Context,             context,                    Target::Struct,         GenericRequirement::None;
     FuturePoll,              sym::poll,                future_poll_fn,             Target::Method(MethodKind::Trait { body: false }), GenericRequirement::None;
 
     FromFrom,                sym::from,                from_fn,                    Target::Method(MethodKind::Trait { body: false }), GenericRequirement::None;

compiler/rustc_hir_analysis/src/astconv/mod.rs

@@ -1930,6 +1930,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                     adt_substs,
                 );
                 let ty = tcx.bound_type_of(assoc_ty_did).subst(tcx, item_substs);
+                let ty = self.normalize_ty(span, ty);
                 return Ok((ty, DefKind::AssocTy, assoc_ty_did));
             }
         }

compiler/rustc_hir_analysis/src/variance/mod.rs

@@ -7,7 +7,8 @@ use rustc_arena::DroplessArena;
 use rustc_hir::def::DefKind;
 use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_middle::ty::query::Providers;
-use rustc_middle::ty::{self, CrateVariancesMap, TyCtxt, TypeSuperVisitable, TypeVisitable};
+use rustc_middle::ty::{self, CrateVariancesMap, SubstsRef, Ty, TyCtxt};
+use rustc_middle::ty::{DefIdTree, TypeSuperVisitable, TypeVisitable};
 use std::ops::ControlFlow;
 
 /// Defines the `TermsContext` basically houses an arena where we can
@@ -75,18 +76,50 @@ fn variance_of_opaque(tcx: TyCtxt<'_>, item_def_id: LocalDefId) -> &[ty::Varianc
     // type Foo<'a, 'b, 'c> = impl Trait<'a> + 'b;
     // ```
     // we may not use `'c` in the hidden type.
-    struct OpaqueTypeLifetimeCollector {
+    struct OpaqueTypeLifetimeCollector<'tcx> {
+        tcx: TyCtxt<'tcx>,
+        root_def_id: DefId,
         variances: Vec<ty::Variance>,
     }
 
-    impl<'tcx> ty::TypeVisitor<'tcx> for OpaqueTypeLifetimeCollector {
+    impl<'tcx> OpaqueTypeLifetimeCollector<'tcx> {
+        #[instrument(level = "trace", skip(self), ret)]
+        fn visit_opaque(&mut self, def_id: DefId, substs: SubstsRef<'tcx>) -> ControlFlow<!> {
+            if def_id != self.root_def_id && self.tcx.is_descendant_of(def_id, self.root_def_id) {
+                let child_variances = self.tcx.variances_of(def_id);
+                for (a, v) in substs.iter().zip(child_variances) {
+                    if *v != ty::Bivariant {
+                        a.visit_with(self)?;
+                    }
+                }
+                ControlFlow::CONTINUE
+            } else {
+                substs.visit_with(self)
+            }
+        }
+    }
+
+    impl<'tcx> ty::TypeVisitor<'tcx> for OpaqueTypeLifetimeCollector<'tcx> {
         #[instrument(level = "trace", skip(self), ret)]
         fn visit_region(&mut self, r: ty::Region<'tcx>) -> ControlFlow<Self::BreakTy> {
             if let ty::RegionKind::ReEarlyBound(ebr) = r.kind() {
                 self.variances[ebr.index as usize] = ty::Invariant;
             }
             r.super_visit_with(self)
         }
+
+        #[instrument(level = "trace", skip(self), ret)]
+        fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
+            match t.kind() {
+                ty::Opaque(def_id, substs) => self.visit_opaque(*def_id, substs),
+                ty::Projection(proj)
+                    if self.tcx.def_kind(proj.item_def_id) == DefKind::ImplTraitPlaceholder =>
+                {
+                    self.visit_opaque(proj.item_def_id, proj.substs)
+                }
+                _ => t.super_visit_with(self),
+            }
+        }
     }
 
     // By default, RPIT are invariant wrt type and const generics, but they are bivariant wrt
@@ -111,7 +144,8 @@ fn variance_of_opaque(tcx: TyCtxt<'_>, item_def_id: LocalDefId) -> &[ty::Varianc
         }
     }
 
-    let mut collector = OpaqueTypeLifetimeCollector { variances };
+    let mut collector =
+        OpaqueTypeLifetimeCollector { tcx, root_def_id: item_def_id.to_def_id(), variances };
     let id_substs = ty::InternalSubsts::identity_for_item(tcx, item_def_id.to_def_id());
     for pred in tcx.bound_explicit_item_bounds(item_def_id.to_def_id()).transpose_iter() {
         let pred = pred.map_bound(|(pred, _)| *pred).subst(tcx, id_substs);

compiler/rustc_middle/src/mir/syntax.rs

@@ -518,12 +518,6 @@ pub enum TerminatorKind<'tcx> {
     SwitchInt {
         /// The discriminant value being tested.
         discr: Operand<'tcx>,
-
-        /// The type of value being tested.
-        /// This is always the same as the type of `discr`.
-        /// FIXME: remove this redundant information. Currently, it is relied on by pretty-printing.
-        switch_ty: Ty<'tcx>,
-
         targets: SwitchTargets,
     },