Properly track the depth when expanding free alias types

1 files changed, 20 insertions, 0 deletions

diff --git a/tests/ui/lazy-type-alias/deep-expansion.rs b/tests/ui/lazy-type-alias/deep-expansion.rs
new file mode 100644
index 00000000000..c4461abdb81
--- /dev/null
+++ b/tests/ui/lazy-type-alias/deep-expansion.rs
@@ -0,0 +1,20 @@
+// In several type analysis passes we employ a specialized expansion procedure.
+// This procedure used to incorrectly track expansion depth (growing much faster
+// than normalization depth) resulting in its internal assertion triggering.
+//
+// issue: <https://github.com/rust-lang/rust/issues/142419>
+//@ check-pass
+#![feature(lazy_type_alias)]
+#![expect(incomplete_features)]
+
+type T0 = (T1, T1, T1, T1);
+type T1 = (T2, T2, T2, T2);
+type T2 = (T3, T3, T3, T3);
+type T3 = (T4, T4, T4, T4);
+type T4 = (T5, T5, T5, T5);
+type T5 = (T6, T6, T6, T6);
+type T6 = (T7, T7, T7, T7);
+type T7 = ();
+
+fn accept(_: T0) {}
+fn main() {}