find the generic container rather than simply looking up for the assoc with const arg

Author: bvanjoi

compiler/rustc_hir_analysis/src/collect/type_of.rs

@@ -175,19 +175,31 @@ fn const_arg_anon_type_of<'tcx>(tcx: TyCtxt<'tcx>, arg_hir_id: HirId, span: Span
         // arm would handle this.
         //
         // I believe this match arm is only needed for GAT but I am not 100% sure - BoxyUwU
-        Node::Ty(hir_ty @ hir::Ty { kind: TyKind::Path(QPath::TypeRelative(_, segment)), .. }) => {
+        Node::Ty(hir_ty @ hir::Ty { kind: TyKind::Path(QPath::TypeRelative(ty, segment)), .. }) => {
             // Find the Item containing the associated type so we can create an ItemCtxt.
             // Using the ItemCtxt lower the HIR for the unresolved assoc type into a
             // ty which is a fully resolved projection.
             // For the code example above, this would mean lowering `Self::Assoc<3>`
             // to a ty::Alias(ty::Projection, `<Self as Foo>::Assoc<3>`).
-            let item_def_id = tcx
-                .hir()
-                .parent_owner_iter(arg_hir_id)
-                .find(|(_, node)| matches!(node, OwnerNode::Item(_)))
-                .unwrap()
-                .0
-                .def_id;
+            let node = if let TyKind::Path(QPath::Resolved(_, path)) = ty.kind
+                && let def::Res::Def(def::DefKind::TyParam, did) = path.res
+            {
+                tcx.hir()
+                    .parent_owner_iter(arg_hir_id)
+                    .find(|(_, node)| {
+                        tcx.generics_of(node.def_id())
+                            .own_params
+                            .iter()
+                            .any(|param| param.def_id == did)
+                    })
+                    .unwrap()
+            } else {
+                tcx.hir()
+                    .parent_owner_iter(arg_hir_id)
+                    .find(|(_, node)| matches!(node, OwnerNode::Item(_)))
+                    .unwrap()
+            };
+            let item_def_id = node.0.def_id;
             let ty = ItemCtxt::new(tcx, item_def_id).lower_ty(hir_ty);
 
             // Iterate through the generics of the projection to find the one that corresponds to

tests/ui/traits/bound/unknown-assoc-with-const-arg.rs

@@ -0,0 +1,9 @@
+// issue#132534
+
+trait X {
+    fn a<T>() -> T::unknown<{}> {}
+    //~^ ERROR: associated type `unknown` not found for `T`
+    //~| ERROR: associated type `unknown` not found for `T`
+}
+
+fn main() {}

tests/ui/traits/bound/unknown-assoc-with-const-arg.stderr

@@ -0,0 +1,17 @@
+error[E0220]: associated type `unknown` not found for `T`
+  --> $DIR/unknown-assoc-with-const-arg.rs:4:21
+   |
+LL |     fn a<T>() -> T::unknown<{}> {}
+   |                     ^^^^^^^ associated type `unknown` not found
+
+error[E0220]: associated type `unknown` not found for `T`
+  --> $DIR/unknown-assoc-with-const-arg.rs:4:21
+   |
+LL |     fn a<T>() -> T::unknown<{}> {}
+   |                     ^^^^^^^ associated type `unknown` not found
+   |
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0220`.