Rollup merge of #103383 - compiler-errors:tait-scope, r=oli-obk

Note scope of TAIT more accurately

This maybe explains why the person was confused in #101897, since we say "same module" but really should've said "same impl".

r? ``@oli-obk``

compiler/rustc_error_messages/locales/en-US/hir_analysis.ftl

@@ -93,7 +93,7 @@ hir_analysis_expected_default_return_type = expected `()` because of default ret
 hir_analysis_expected_return_type = expected `{$expected}` because of return type
 
 hir_analysis_unconstrained_opaque_type = unconstrained opaque type
-    .note = `{$name}` must be used in combination with a concrete type within the same module
+    .note = `{$name}` must be used in combination with a concrete type within the same {$what}
 
 hir_analysis_missing_type_params =
     the type {$parameterCount ->

compiler/rustc_hir_analysis/src/collect/type_of.rs

@@ -701,6 +701,12 @@ fn visit_trait_item(&mut self, it: &'tcx TraitItem<'tcx>) {
         tcx.sess.emit_err(UnconstrainedOpaqueType {
             span: tcx.def_span(def_id),
             name: tcx.item_name(tcx.local_parent(def_id).to_def_id()),
+            what: match tcx.hir().get(scope) {
+                _ if scope == hir::CRATE_HIR_ID => "module",
+                Node::Item(hir::Item { kind: hir::ItemKind::Mod(_), .. }) => "module",
+                Node::Item(hir::Item { kind: hir::ItemKind::Impl(_), .. }) => "impl",
+                _ => "item",
+            },
         });
         return tcx.ty_error();
     };

compiler/rustc_hir_analysis/src/errors.rs

@@ -143,6 +143,7 @@ pub struct UnconstrainedOpaqueType {
     #[primary_span]
     pub span: Span,
     pub name: Symbol,
+    pub what: &'static str,
 }
 
 pub struct MissingTypeParams {

src/test/ui/generic-associated-types/issue-87258_a.stderr

@@ -4,7 +4,7 @@ error: unconstrained opaque type
 LL |     type FooFuture<'a> = impl Trait1;
    |                          ^^^^^^^^^^^
    |
-   = note: `FooFuture` must be used in combination with a concrete type within the same module
+   = note: `FooFuture` must be used in combination with a concrete type within the same impl
 
 error: aborting due to previous error
 

src/test/ui/lint/inline-trait-and-foreign-items.stderr

@@ -67,7 +67,7 @@ error: unconstrained opaque type
 LL |     type U = impl Trait;
    |              ^^^^^^^^^^
    |
-   = note: `U` must be used in combination with a concrete type within the same module
+   = note: `U` must be used in combination with a concrete type within the same impl
 
 error: aborting due to 6 previous errors; 2 warnings emitted
 

src/test/ui/lint/no-coverage.stderr

@@ -94,7 +94,7 @@ error: unconstrained opaque type
 LL |     type U = impl Trait;
    |              ^^^^^^^^^^
    |
-   = note: `U` must be used in combination with a concrete type within the same module
+   = note: `U` must be used in combination with a concrete type within the same impl
 
 error: aborting due to 7 previous errors; 6 warnings emitted
 

src/test/ui/save-analysis/issue-68621.stderr

@@ -4,7 +4,7 @@ error: unconstrained opaque type
 LL |     type Future = impl Trait;
    |                   ^^^^^^^^^^
    |
-   = note: `Future` must be used in combination with a concrete type within the same module
+   = note: `Future` must be used in combination with a concrete type within the same impl
 
 error: aborting due to previous error