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_hir_analysis/src/collect/type_of.rs

@@ -701,6 +701,12 @@ fn find_opaque_ty_constraints_for_tait(tcx: TyCtxt<'_>, def_id: LocalDefId) -> T
         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 {