1 files changed, 20 insertions, 0 deletions
diff --git a/tests/ui/traits/next-solver/object-soundness-requires-generalization.rs b/tests/ui/traits/next-solver/object-soundness-requires-generalization.rs
new file mode 100644
index 000000000..6e709d9ae
--- /dev/null
+++ b/tests/ui/traits/next-solver/object-soundness-requires-generalization.rs
@@ -0,0 +1,20 @@
+// compile-flags: -Znext-solver
+// ignore-test
+
+trait Trait {
+    type Gat<'lt>;
+}
+impl Trait for u8 {
+    type Gat<'lt> = u8;
+}
+
+fn test<T: Trait, F: FnOnce(<T as Trait>::Gat<'_>) -> S + ?Sized, S>() {}
+
+fn main() {
+    // Proving `dyn FnOnce: FnOnce` requires making sure that all of the supertraits
+    // of the trait and associated type bounds hold. We check this in
+    // `predicates_for_object_candidate`, and eagerly replace projections using equality
+    // which may generalize a type and emit a nested AliasRelate goal. Make sure that
+    // we don't ICE in that case, and bubble that goal up to the caller.
+    test::<u8, dyn FnOnce(<u8 as Trait>::Gat<'_>) + 'static, _>();
+}