fix: Crash on lowering consts with associated types

crates/hir-ty/src/lower.rs

@@ -1948,6 +1948,7 @@ fn resolve_type_param_assoc_type_shorthand(
     let mut supertraits_resolution = None;
     for maybe_parent_generics in generics.iter_owners().rev() {
         ctx.store = maybe_parent_generics.store();
+        ctx.def = ExpressionStoreOwnerId::Signature(maybe_parent_generics.def());
         for pred in maybe_parent_generics.where_predicates() {
             let (WherePredicate::TypeBound { target, bound }
             | WherePredicate::ForLifetime { lifetimes: _, target, bound }) = pred
@@ -2366,6 +2367,7 @@ fn generic_predicates(
         ctx.diagnostics.clear();
 
         ctx.store = maybe_parent_generics.store();
+        ctx.def = ExpressionStoreOwnerId::Signature(maybe_parent_generics.def());
         for pred in maybe_parent_generics.where_predicates() {
             tracing::debug!(?pred);
             for (pred, source) in ctx.lower_where_predicate(pred, false) {
@@ -2568,13 +2570,15 @@ pub(crate) fn generic_defaults_with_diagnostics(
     let mut defaults = ThinVec::new();
     if let Some(parent) = generics.parent() {
         ctx.store = parent.store();
+        ctx.def = ExpressionStoreOwnerId::Signature(parent.def());
         defaults.extend(
             parent.iter_with_idx().map(|(idx, _id, p)| handle_generic_param(&mut ctx, idx, p)),
         );
     }
     ctx.diagnostics.clear(); // Don't include diagnostics from the parent.
     ctx.defined_anon_consts.clear();
     ctx.store = store_for_self;
+    ctx.def = ExpressionStoreOwnerId::Signature(def);
     defaults.extend(
         generics.iter_self_with_idx().map(|(idx, _id, p)| handle_generic_param(&mut ctx, idx, p)),
     );

crates/hir-ty/src/tests/regression.rs

@@ -43,6 +43,26 @@ fn no_panic_on_field_of_enum() {
     );
 }
 
+#[test]
+fn anon_const_projection_in_impl_predicate() {
+    check_no_mismatches(
+        r#"
+trait Trait {
+    type Assoc;
+}
+
+struct S<const N: usize>;
+
+impl<const N: usize> S<N>
+where
+    S<{ N }>: Trait,
+{
+    fn new(_: <S<N> as Trait>::Assoc) {}
+}
+        "#,
+    );
+}
+
 #[test]
 fn bug_585() {
     check_infer(