Merge from rustc

Author: RalfJung

compiler/rustc_ast_lowering/src/item.rs

@@ -305,7 +305,10 @@ impl<'hir> LoweringContext<'_, 'hir> {
                             );
                             this.arena.alloc(this.ty(span, hir::TyKind::Err(guar)))
                         }
-                        Some(ty) => this.lower_ty(ty, &ImplTraitContext::TypeAliasesOpaqueTy),
+                        Some(ty) => this.lower_ty(
+                            ty,
+                            &ImplTraitContext::TypeAliasesOpaqueTy { in_assoc_ty: false },
+                        ),
                     },
                 );
                 hir::ItemKind::TyAlias(ty, generics)
@@ -852,7 +855,10 @@ impl<'hir> LoweringContext<'_, 'hir> {
                             hir::ImplItemKind::Type(ty)
                         }
                         Some(ty) => {
-                            let ty = this.lower_ty(ty, &ImplTraitContext::TypeAliasesOpaqueTy);
+                            let ty = this.lower_ty(
+                                ty,
+                                &ImplTraitContext::TypeAliasesOpaqueTy { in_assoc_ty: true },
+                            );
                             hir::ImplItemKind::Type(ty)
                         }
                     },

compiler/rustc_ast_lowering/src/lib.rs

@@ -247,7 +247,7 @@ enum ImplTraitContext {
         in_trait: bool,
     },
     /// Impl trait in type aliases.
-    TypeAliasesOpaqueTy,
+    TypeAliasesOpaqueTy { in_assoc_ty: bool },
     /// `impl Trait` is unstably accepted in this position.
     FeatureGated(ImplTraitPosition, Symbol),
     /// `impl Trait` is not accepted in this position.
@@ -1407,14 +1407,15 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                             *in_trait,
                             itctx,
                         ),
-                    ImplTraitContext::TypeAliasesOpaqueTy => self.lower_opaque_impl_trait(
-                        span,
-                        hir::OpaqueTyOrigin::TyAlias,
-                        *def_node_id,
-                        bounds,
-                        false,
-                        itctx,
-                    ),
+                    &ImplTraitContext::TypeAliasesOpaqueTy { in_assoc_ty } => self
+                        .lower_opaque_impl_trait(
+                            span,
+                            hir::OpaqueTyOrigin::TyAlias { in_assoc_ty },
+                            *def_node_id,
+                            bounds,
+                            false,
+                            itctx,
+                        ),
                     ImplTraitContext::Universal => {
                         let span = t.span;
                         self.create_def(
@@ -1534,13 +1535,16 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         // If this came from a TAIT (as opposed to a function that returns an RPIT), we only want
         // to capture the lifetimes that appear in the bounds. So visit the bounds to find out
         // exactly which ones those are.
-        let lifetimes_to_remap = if origin == hir::OpaqueTyOrigin::TyAlias {
-            // in a TAIT like `type Foo<'a> = impl Foo<'a>`, we don't keep all the lifetime parameters
-            Vec::new()
-        } else {
-            // in fn return position, like the `fn test<'a>() -> impl Debug + 'a` example,
-            // we only keep the lifetimes that appear in the `impl Debug` itself:
-            lifetime_collector::lifetimes_in_bounds(&self.resolver, bounds)
+        let lifetimes_to_remap = match origin {
+            hir::OpaqueTyOrigin::TyAlias { .. } => {
+                // in a TAIT like `type Foo<'a> = impl Foo<'a>`, we don't keep all the lifetime parameters
+                Vec::new()
+            }
+            hir::OpaqueTyOrigin::AsyncFn(..) | hir::OpaqueTyOrigin::FnReturn(..) => {
+                // in fn return position, like the `fn test<'a>() -> impl Debug + 'a` example,
+                // we only keep the lifetimes that appear in the `impl Debug` itself:
+                lifetime_collector::lifetimes_in_bounds(&self.resolver, bounds)
+            }
         };
         debug!(?lifetimes_to_remap);
 

compiler/rustc_borrowck/src/dataflow.rs

@@ -328,7 +328,7 @@ impl<'tcx> rustc_mir_dataflow::AnalysisDomain<'tcx> for Borrows<'_, 'tcx> {
 
     fn bottom_value(&self, _: &mir::Body<'tcx>) -> Self::Domain {
         // bottom = nothing is reserved or activated yet;
-        BitSet::new_empty(self.borrow_set.len() * 2)
+        BitSet::new_empty(self.borrow_set.len())
     }
 
     fn initialize_start_block(&self, _: &mir::Body<'tcx>, _: &mut Self::Domain) {

compiler/rustc_borrowck/src/region_infer/opaque_types.rs

@@ -265,7 +265,7 @@ impl<'tcx> InferCtxtExt<'tcx> for InferCtxt<'tcx> {
 
         // Only check this for TAIT. RPIT already supports `tests/ui/impl-trait/nested-return-type2.rs`
         // on stable and we'd break that.
-        let OpaqueTyOrigin::TyAlias = origin else {
+        let OpaqueTyOrigin::TyAlias { .. } = origin else {
             return definition_ty;
         };
         let def_id = opaque_type_key.def_id;
@@ -360,7 +360,7 @@ fn check_opaque_type_parameter_valid(
         // which would error here on all of the `'static` args.
         OpaqueTyOrigin::FnReturn(..) | OpaqueTyOrigin::AsyncFn(..) => return Ok(()),
         // Check these
-        OpaqueTyOrigin::TyAlias => {}
+        OpaqueTyOrigin::TyAlias { .. } => {}
     }
     let opaque_generics = tcx.generics_of(opaque_type_key.def_id);
     let mut seen_params: FxIndexMap<_, Vec<_>> = FxIndexMap::default();

compiler/rustc_builtin_macros/src/format_foreign.rs

@@ -562,15 +562,13 @@ pub(crate) mod printf {
         }
 
         if let Type = state {
-            drop(c);
             type_ = at.slice_between(next).unwrap();
 
             // Don't use `move_to!` here, as we *can* be at the end of the input.
             at = next;
         }
 
-        drop(c);
-        drop(next);
+        let _ = c; // to avoid never used value
 
         end = at;
         let position = InnerSpan::new(start.at, end.at);

compiler/rustc_feature/src/active.rs

@@ -321,6 +321,8 @@ declare_features! (
     (active, c_unwind, "1.52.0", Some(74990), None),
     /// Allows using C-variadics.
     (active, c_variadic, "1.34.0", Some(44930), None),
+    /// Allows the use of `#[cfg(overflow_checks)` to check if integer overflow behaviour.
+    (active, cfg_overflow_checks, "CURRENT_RUSTC_VERSION", Some(111466), None),
     /// Allows the use of `#[cfg(sanitize = "option")]`; set when -Zsanitizer is used.
     (active, cfg_sanitize, "1.41.0", Some(39699), None),
     /// Allows `cfg(target_abi = "...")`.

compiler/rustc_feature/src/builtin_attrs.rs

@@ -24,6 +24,7 @@ pub type GatedCfg = (Symbol, Symbol, GateFn);
 /// `cfg(...)`'s that are feature gated.
 const GATED_CFGS: &[GatedCfg] = &[
     // (name in cfg, feature, function to check if the feature is enabled)
+    (sym::overflow_checks, sym::cfg_overflow_checks, cfg_fn!(cfg_overflow_checks)),
     (sym::target_abi, sym::cfg_target_abi, cfg_fn!(cfg_target_abi)),
     (sym::target_thread_local, sym::cfg_target_thread_local, cfg_fn!(cfg_target_thread_local)),
     (

compiler/rustc_hir/src/hir.rs

@@ -2662,7 +2662,10 @@ pub enum OpaqueTyOrigin {
     /// `async fn`
     AsyncFn(LocalDefId),
     /// type aliases: `type Foo = impl Trait;`
-    TyAlias,
+    TyAlias {
+        /// associated types in impl blocks for traits.
+        in_assoc_ty: bool,
+    },
 }
 
 /// The various kinds of types recognized by the compiler.

compiler/rustc_hir_analysis/src/check/check.rs

@@ -397,7 +397,7 @@ fn check_opaque_meets_bounds<'tcx>(
 ) {
     let defining_use_anchor = match *origin {
         hir::OpaqueTyOrigin::FnReturn(did) | hir::OpaqueTyOrigin::AsyncFn(did) => did,
-        hir::OpaqueTyOrigin::TyAlias => def_id,
+        hir::OpaqueTyOrigin::TyAlias { .. } => tcx.impl_trait_parent(def_id),
     };
     let param_env = tcx.param_env(defining_use_anchor);
 
@@ -455,10 +455,10 @@ fn check_opaque_meets_bounds<'tcx>(
         // They can only be referenced as `<Opaque<T> as Trait<&'static T>>::AssocTy`.
         // We don't have to check them here because their well-formedness follows from the WF of
         // the projection input types in the defining- and use-sites.
-        hir::OpaqueTyOrigin::TyAlias
+        hir::OpaqueTyOrigin::TyAlias { .. }
             if tcx.def_kind(tcx.parent(def_id.to_def_id())) == DefKind::OpaqueTy => {}
         // Can have different predicates to their defining use
-        hir::OpaqueTyOrigin::TyAlias => {
+        hir::OpaqueTyOrigin::TyAlias { .. } => {
             let wf_tys = ocx.assumed_wf_types(param_env, span, def_id);
             let implied_bounds = infcx.implied_bounds_tys(param_env, def_id, wf_tys);
             let outlives_env = OutlivesEnvironment::with_bounds(param_env, implied_bounds);

compiler/rustc_hir_analysis/src/check/dropck.rs

@@ -6,7 +6,7 @@ use rustc_errors::{struct_span_err, ErrorGuaranteed};
 use rustc_infer::infer::outlives::env::OutlivesEnvironment;
 use rustc_infer::infer::{RegionResolutionError, TyCtxtInferExt};
 use rustc_middle::ty::subst::SubstsRef;
-use rustc_middle::ty::util::IgnoreRegions;
+use rustc_middle::ty::util::CheckRegions;
 use rustc_middle::ty::{self, TyCtxt};
 use rustc_trait_selection::traits::{self, ObligationCtxt};
 
@@ -81,7 +81,7 @@ fn ensure_drop_params_and_item_params_correspond<'tcx>(
     self_type_did: DefId,
     adt_to_impl_substs: SubstsRef<'tcx>,
 ) -> Result<(), ErrorGuaranteed> {
-    let Err(arg) = tcx.uses_unique_generic_params(adt_to_impl_substs, IgnoreRegions::No) else {
+    let Err(arg) = tcx.uses_unique_generic_params(adt_to_impl_substs, CheckRegions::OnlyEarlyBound) else {
         return Ok(())
     };