Auto merge of #133393 - compiler-errors:dyn-tweaks, r=lcnr,spastorino

Some minor dyn-related tweaks

Each commit should be self-explanatory, but I'm happy to explain what's going on if not. These are tweaks I pulled out of #133388, but they can be reviewed sooner than that.

r? types

4 files changed, 11 insertions, 74 deletions

diff --git a/compiler/rustc_hir_analysis/src/hir_ty_lowering/dyn_compatibility.rs b/compiler/rustc_hir_analysis/src/hir_ty_lowering/dyn_compatibility.rs
index f6e227377b9..cab04ee0987 100644
--- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/dyn_compatibility.rs
+++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/dyn_compatibility.rs
@@ -136,7 +136,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
 
         for (base_trait_ref, original_span) in regular_traits_refs_spans {
             let base_pred: ty::Predicate<'tcx> = base_trait_ref.upcast(tcx);
-            for ClauseWithSupertraitSpan { pred, original_span, supertrait_span } in
+            for ClauseWithSupertraitSpan { pred, supertrait_span } in
                 traits::elaborate(tcx, [ClauseWithSupertraitSpan::new(base_pred, original_span)])
                     .filter_only_self()
             {
@@ -204,7 +204,6 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         for def_ids in associated_types.values_mut() {
             for (projection_bound, span) in &projection_bounds {
                 let def_id = projection_bound.projection_def_id();
-                // FIXME(#120456) - is `swap_remove` correct?
                 def_ids.swap_remove(&def_id);
                 if tcx.generics_require_sized_self(def_id) {
                     tcx.emit_node_span_lint(
diff --git a/compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs b/compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs
index 4e5a8271e9e..0b58b807090 100644
--- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs
+++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs
@@ -727,7 +727,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         let tcx = self.tcx();
         // FIXME: Marked `mut` so that we can replace the spans further below with a more
         // appropriate one, but this should be handled earlier in the span assignment.
-        let mut associated_types: FxIndexMap<Span, Vec<_>> = associated_types
+        let associated_types: FxIndexMap<Span, Vec<_>> = associated_types
             .into_iter()
             .map(|(span, def_ids)| {
                 (span, def_ids.into_iter().map(|did| tcx.associated_item(did)).collect())
@@ -769,39 +769,6 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                 hir::Node::Expr(_) | hir::Node::Pat(_) => true,
                 _ => false,
             };
-            match bound.trait_ref.path.segments {
-                // FIXME: `trait_ref.path.span` can point to a full path with multiple
-                // segments, even though `trait_ref.path.segments` is of length `1`. Work
-                // around that bug here, even though it should be fixed elsewhere.
-                // This would otherwise cause an invalid suggestion. For an example, look at
-                // `tests/ui/issues/issue-28344.rs` where instead of the following:
-                //
-                //   error[E0191]: the value of the associated type `Output`
-                //                 (from trait `std::ops::BitXor`) must be specified
-                //   --> $DIR/issue-28344.rs:4:17
-                //    |
-                // LL |     let x: u8 = BitXor::bitor(0 as u8, 0 as u8);
-                //    |                 ^^^^^^ help: specify the associated type:
-                //    |                              `BitXor<Output = Type>`
-                //
-                // we would output:
-                //
-                //   error[E0191]: the value of the associated type `Output`
-                //                 (from trait `std::ops::BitXor`) must be specified
-                //   --> $DIR/issue-28344.rs:4:17
-                //    |
-                // LL |     let x: u8 = BitXor::bitor(0 as u8, 0 as u8);
-                //    |                 ^^^^^^^^^^^^^ help: specify the associated type:
-                //    |                                     `BitXor::bitor<Output = Type>`
-                [segment] if segment.args.is_none() => {
-                    trait_bound_spans = vec![segment.ident.span];
-                    associated_types = associated_types
-                        .into_values()
-                        .map(|items| (segment.ident.span, items))
-                        .collect();
-                }
-                _ => {}
-            }
         }
 
         // We get all the associated items that _are_ set,
diff --git a/compiler/rustc_trait_selection/src/traits/wf.rs b/compiler/rustc_trait_selection/src/traits/wf.rs
index 437343b569c..c95b1641d1f 100644
--- a/compiler/rustc_trait_selection/src/traits/wf.rs
+++ b/compiler/rustc_trait_selection/src/traits/wf.rs
@@ -963,30 +963,7 @@ impl<'a, 'tcx> TypeVisitor<TyCtxt<'tcx>> for WfPredicates<'a, 'tcx> {
 /// bounds that must hold on the elided self type. These are derived
 /// from the declarations of `SomeTrait`, `Send`, and friends -- if
 /// they declare `trait SomeTrait : 'static`, for example, then
-/// `'static` would appear in the list. The hard work is done by
-/// `infer::required_region_bounds`, see that for more information.
-pub fn object_region_bounds<'tcx>(
-    tcx: TyCtxt<'tcx>,
-    existential_predicates: &'tcx ty::List<ty::PolyExistentialPredicate<'tcx>>,
-) -> Vec<ty::Region<'tcx>> {
-    let predicates = existential_predicates.iter().filter_map(|predicate| {
-        if let ty::ExistentialPredicate::Projection(_) = predicate.skip_binder() {
-            None
-        } else {
-            Some(predicate.with_self_ty(tcx, tcx.types.trait_object_dummy_self))
-        }
-    });
-
-    required_region_bounds(tcx, tcx.types.trait_object_dummy_self, predicates)
-}
-
-/// Given a set of predicates that apply to an object type, returns
-/// the region bounds that the (erased) `Self` type must
-/// outlive. Precisely *because* the `Self` type is erased, the
-/// parameter `erased_self_ty` must be supplied to indicate what type
-/// has been used to represent `Self` in the predicates
-/// themselves. This should really be a unique type; `FreshTy(0)` is a
-/// popular choice.
+/// `'static` would appear in the list.
 ///
 /// N.B., in some cases, particularly around higher-ranked bounds,
 /// this function returns a kind of conservative approximation.
@@ -996,13 +973,14 @@ pub fn object_region_bounds<'tcx>(
 ///
 /// Requires that trait definitions have been processed so that we can
 /// elaborate predicates and walk supertraits.
-#[instrument(skip(tcx, predicates), level = "debug", ret)]
-pub(crate) fn required_region_bounds<'tcx>(
+pub fn object_region_bounds<'tcx>(
     tcx: TyCtxt<'tcx>,
-    erased_self_ty: Ty<'tcx>,
-    predicates: impl Iterator<Item = ty::Clause<'tcx>>,
+    existential_predicates: &'tcx ty::List<ty::PolyExistentialPredicate<'tcx>>,
 ) -> Vec<ty::Region<'tcx>> {
-    assert!(!erased_self_ty.has_escaping_bound_vars());
+    let erased_self_ty = tcx.types.trait_object_dummy_self;
+
+    let predicates =
+        existential_predicates.iter().map(|predicate| predicate.with_self_ty(tcx, erased_self_ty));
 
     traits::elaborate(tcx, predicates)
         .filter_map(|pred| {
diff --git a/compiler/rustc_type_ir/src/elaborate.rs b/compiler/rustc_type_ir/src/elaborate.rs
index 2c1ad9de9aa..0d574445df8 100644
--- a/compiler/rustc_type_ir/src/elaborate.rs
+++ b/compiler/rustc_type_ir/src/elaborate.rs
@@ -45,14 +45,12 @@ pub trait Elaboratable<I: Interner> {
 
 pub struct ClauseWithSupertraitSpan<I: Interner> {
     pub pred: I::Predicate,
-    // Span of the original elaborated predicate.
-    pub original_span: I::Span,
     // Span of the supertrait predicatae that lead to this clause.
     pub supertrait_span: I::Span,
 }
 impl<I: Interner> ClauseWithSupertraitSpan<I> {
     pub fn new(pred: I::Predicate, span: I::Span) -> Self {
-        ClauseWithSupertraitSpan { pred, original_span: span, supertrait_span: span }
+        ClauseWithSupertraitSpan { pred, supertrait_span: span }
     }
 }
 impl<I: Interner> Elaboratable<I> for ClauseWithSupertraitSpan<I> {
@@ -63,7 +61,6 @@ impl<I: Interner> Elaboratable<I> for ClauseWithSupertraitSpan<I> {
     fn child(&self, clause: <I as Interner>::Clause) -> Self {
         ClauseWithSupertraitSpan {
             pred: clause.as_predicate(),
-            original_span: self.original_span,
             supertrait_span: self.supertrait_span,
         }
     }
@@ -75,11 +72,7 @@ impl<I: Interner> Elaboratable<I> for ClauseWithSupertraitSpan<I> {
         _parent_trait_pred: crate::Binder<I, crate::TraitPredicate<I>>,
         _index: usize,
     ) -> Self {
-        ClauseWithSupertraitSpan {
-            pred: clause.as_predicate(),
-            original_span: self.original_span,
-            supertrait_span: supertrait_span,
-        }
+        ClauseWithSupertraitSpan { pred: clause.as_predicate(), supertrait_span: supertrait_span }
     }
 }