Rollup merge of #121991 - oli-obk:merge_opaque_types_defined_by_queries, r=compiler-errors

Merge impl_trait_in_assoc_types_defined_by query back into `opaque_types_defined_by`

Instead, when we're collecting opaques for associated items, we choose the right collection mode depending on whether we're collecting for an associated item of a trait impl or not.

r? ```@compiler-errors```

follow up to https://github.com/rust-lang/rust/pull/121838

compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs

@@ -46,9 +46,7 @@ pub(super) fn find_opaque_ty_constraints_for_impl_trait_in_assoc_type(
     for &assoc_id in tcx.associated_item_def_ids(impl_def_id) {
         let assoc = tcx.associated_item(assoc_id);
         match assoc.kind {
-            ty::AssocKind::Const | ty::AssocKind::Fn => {
-                locator.check(assoc_id.expect_local(), ImplTraitSource::AssocTy)
-            }
+            ty::AssocKind::Const | ty::AssocKind::Fn => locator.check(assoc_id.expect_local()),
             // Associated types don't have bodies, so they can't constrain hidden types
             ty::AssocKind::Type => {}
         }
@@ -182,15 +180,9 @@ struct TaitConstraintLocator<'tcx> {
     typeck_types: Vec<ty::OpaqueHiddenType<'tcx>>,
 }
 
-#[derive(Debug)]
-enum ImplTraitSource {
-    AssocTy,
-    TyAlias,
-}
-
 impl TaitConstraintLocator<'_> {
     #[instrument(skip(self), level = "debug")]
-    fn check(&mut self, item_def_id: LocalDefId, source: ImplTraitSource) {
+    fn check(&mut self, item_def_id: LocalDefId) {
         // Don't try to check items that cannot possibly constrain the type.
         if !self.tcx.has_typeck_results(item_def_id) {
             debug!("no constraint: no typeck results");
@@ -242,12 +234,8 @@ fn check(&mut self, item_def_id: LocalDefId, source: ImplTraitSource) {
                 continue;
             }
             constrained = true;
-            let opaque_types_defined_by = match source {
-                ImplTraitSource::AssocTy => {
-                    self.tcx.impl_trait_in_assoc_types_defined_by(item_def_id)
-                }
-                ImplTraitSource::TyAlias => self.tcx.opaque_types_defined_by(item_def_id),
-            };
+            let opaque_types_defined_by = self.tcx.opaque_types_defined_by(item_def_id);
+
             if !opaque_types_defined_by.contains(&self.def_id) {
                 self.tcx.dcx().emit_err(TaitForwardCompat {
                     span: hidden_type.span,
@@ -308,7 +296,7 @@ fn nested_visit_map(&mut self) -> Self::Map {
     }
     fn visit_expr(&mut self, ex: &'tcx Expr<'tcx>) {
         if let hir::ExprKind::Closure(closure) = ex.kind {
-            self.check(closure.def_id, ImplTraitSource::TyAlias);
+            self.check(closure.def_id);
         }
         intravisit::walk_expr(self, ex);
     }
@@ -316,7 +304,7 @@ fn visit_item(&mut self, it: &'tcx Item<'tcx>) {
         trace!(?it.owner_id);
         // The opaque type itself or its children are not within its reveal scope.
         if it.owner_id.def_id != self.def_id {
-            self.check(it.owner_id.def_id, ImplTraitSource::TyAlias);
+            self.check(it.owner_id.def_id);
             intravisit::walk_item(self, it);
         }
     }
@@ -324,13 +312,13 @@ fn visit_impl_item(&mut self, it: &'tcx ImplItem<'tcx>) {
         trace!(?it.owner_id);
         // The opaque type itself or its children are not within its reveal scope.
         if it.owner_id.def_id != self.def_id {
-            self.check(it.owner_id.def_id, ImplTraitSource::TyAlias);
+            self.check(it.owner_id.def_id);
             intravisit::walk_impl_item(self, it);
         }
     }
     fn visit_trait_item(&mut self, it: &'tcx TraitItem<'tcx>) {
         trace!(?it.owner_id);
-        self.check(it.owner_id.def_id, ImplTraitSource::TyAlias);
+        self.check(it.owner_id.def_id);
         intravisit::walk_trait_item(self, it);
     }
     fn visit_foreign_item(&mut self, it: &'tcx hir::ForeignItem<'tcx>) {

compiler/rustc_middle/src/query/mod.rs

@@ -344,15 +344,6 @@
         }
     }
 
-    query impl_trait_in_assoc_types_defined_by(
-        key: LocalDefId
-    ) -> &'tcx ty::List<LocalDefId> {
-        desc {
-            |tcx| "computing the opaque types defined by `{}`",
-            tcx.def_path_str(key.to_def_id())
-        }
-    }
-
     /// Returns the list of bounds that can be used for
     /// `SelectionCandidate::ProjectionCandidate(_)` and
     /// `ProjectionTyCandidate::TraitDef`.

compiler/rustc_ty_utils/src/opaque_types.rs

@@ -34,7 +34,11 @@ enum CollectionMode {
 }
 
 impl<'tcx> OpaqueTypeCollector<'tcx> {
-    fn new(tcx: TyCtxt<'tcx>, item: LocalDefId, mode: CollectionMode) -> Self {
+    fn new(tcx: TyCtxt<'tcx>, item: LocalDefId) -> Self {
+        let mode = match tcx.def_kind(tcx.local_parent(item)) {
+            DefKind::Impl { of_trait: true } => CollectionMode::ImplTraitInAssocTypes,
+            _ => CollectionMode::TypeAliasImplTraitTransition,
+        };
         Self { tcx, opaques: Vec::new(), item, seen: Default::default(), span: None, mode }
     }
 
@@ -287,23 +291,13 @@ fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<!> {
     }
 }
 
-fn impl_trait_in_assoc_types_defined_by<'tcx>(
-    tcx: TyCtxt<'tcx>,
-    item: LocalDefId,
-) -> &'tcx ty::List<LocalDefId> {
-    let mut collector = OpaqueTypeCollector::new(tcx, item, CollectionMode::ImplTraitInAssocTypes);
-    super::sig_types::walk_types(tcx, item, &mut collector);
-    tcx.mk_local_def_ids(&collector.opaques)
-}
-
 fn opaque_types_defined_by<'tcx>(
     tcx: TyCtxt<'tcx>,
     item: LocalDefId,
 ) -> &'tcx ty::List<LocalDefId> {
     let kind = tcx.def_kind(item);
     trace!(?kind);
-    let mut collector =
-        OpaqueTypeCollector::new(tcx, item, CollectionMode::TypeAliasImplTraitTransition);
+    let mut collector = OpaqueTypeCollector::new(tcx, item);
     super::sig_types::walk_types(tcx, item, &mut collector);
     match kind {
         DefKind::AssocFn
@@ -346,6 +340,5 @@ fn opaque_types_defined_by<'tcx>(
 }
 
 pub(super) fn provide(providers: &mut Providers) {
-    *providers =
-        Providers { opaque_types_defined_by, impl_trait_in_assoc_types_defined_by, ..*providers };
+    *providers = Providers { opaque_types_defined_by, ..*providers };
 }

tests/ui/type-alias-impl-trait/hidden_behind_struct_field2.rs

@@ -15,7 +15,7 @@ impl Trait for Bar {
     type Assoc = impl std::fmt::Debug;
     fn foo() -> Foo {
         Foo { field: () }
-        //~^ ERROR: item constrains opaque type that is not in its signature
+        //~^ ERROR: mismatched types
     }
 }
 

tests/ui/type-alias-impl-trait/hidden_behind_struct_field2.stderr

@@ -1,11 +1,15 @@
-error: item constrains opaque type that is not in its signature
+error[E0308]: mismatched types
   --> $DIR/hidden_behind_struct_field2.rs:17:22
    |
+LL |     type Assoc = impl std::fmt::Debug;
+   |                  -------------------- the expected opaque type
+LL |     fn foo() -> Foo {
 LL |         Foo { field: () }
-   |                      ^^
+   |                      ^^ expected opaque type, found `()`
    |
-   = note: this item must mention the opaque type in its signature in order to be able to register hidden types
-note: this item must mention the opaque type in its signature in order to be able to register hidden types
+   = note: expected opaque type `<Bar as Trait>::Assoc`
+                found unit type `()`
+note: this item must have the opaque type in its signature in order to be able to register hidden types
   --> $DIR/hidden_behind_struct_field2.rs:16:8
    |
 LL |     fn foo() -> Foo {
@@ -13,3 +17,4 @@ LL |     fn foo() -> Foo {
 
 error: aborting due to 1 previous error
 
+For more information about this error, try `rustc --explain E0308`.

tests/ui/type-alias-impl-trait/hidden_behind_struct_field3.rs

@@ -17,7 +17,7 @@ impl Trait for Bar {
     type Assoc = impl Iterator<Item = Foo>;
     fn foo() -> Self::Assoc {
         vec![Foo { field: () }].into_iter()
-        //~^ ERROR item constrains opaque type that is not in its signature
+        //~^ ERROR mismatched types
     }
 }
 

tests/ui/type-alias-impl-trait/hidden_behind_struct_field3.stderr

@@ -1,11 +1,15 @@
-error: item constrains opaque type that is not in its signature
+error[E0308]: mismatched types
   --> $DIR/hidden_behind_struct_field3.rs:19:27
    |
+LL |     type Assoc2 = impl std::fmt::Debug;
+   |                   -------------------- the expected opaque type
+...
 LL |         vec![Foo { field: () }].into_iter()
-   |                           ^^
+   |                           ^^ expected opaque type, found `()`
    |
-   = note: this item must mention the opaque type in its signature in order to be able to register hidden types
-note: this item must mention the opaque type in its signature in order to be able to register hidden types
+   = note: expected opaque type `<Bar as Trait>::Assoc2`
+                found unit type `()`
+note: this item must have the opaque type in its signature in order to be able to register hidden types
   --> $DIR/hidden_behind_struct_field3.rs:18:8
    |
 LL |     fn foo() -> Self::Assoc {
@@ -13,3 +17,4 @@ LL |     fn foo() -> Self::Assoc {
 
 error: aborting due to 1 previous error
 
+For more information about this error, try `rustc --explain E0308`.