update overflow handling for norm, add test

compiler/rustc_trait_selection/src/solve/assembly/mod.rs

@@ -352,7 +352,7 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
         let &ty::Alias(_, projection_ty) = goal.predicate.self_ty().kind() else { return };
 
         candidates.extend(self.probe(|_| ProbeKind::NormalizedSelfTyAssembly).enter(|ecx| {
-            if num_steps < ecx.local_overflow_limit() {
+            if tcx.recursion_limit().value_within_limit(num_steps) {
                 let normalized_ty = ecx.next_ty_infer();
                 let normalizes_to_goal = goal.with(
                     tcx,

compiler/rustc_trait_selection/src/solve/mod.rs

@@ -310,7 +310,7 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
         depth: usize,
         ty: Ty<'tcx>,
     ) -> Option<Ty<'tcx>> {
-        if depth >= self.local_overflow_limit() {
+        if !self.tcx().recursion_limit().value_within_limit(depth) {
             return None;
         }
 

tests/ui/traits/new-solver/alias-relate/deeply-nested-no-hang.rs

@@ -0,0 +1,22 @@
+// check-pass
+// compile-flags: -Ztrait-solver=next
+// regression test for trait-system-refactor-initiative#68
+trait Identity {
+    type Assoc: ?Sized;
+}
+
+impl<T: ?Sized> Identity for T {
+    type Assoc = T;
+}
+
+type Id<T> = <T as Identity>::Assoc;
+
+type Five<T> = Id<Id<Id<Id<Id<T>>>>>;
+type Ty<T> = Five<Five<Five<Five<Five<T>>>>>;
+
+trait Trait<T> {}
+
+impl<T> Trait<T> for Ty<T> {}
+impl Trait<u32> for Ty<i32> {}
+
+fn main() {}