Rollup merge of #81927 - vandenheuvel:issue_32498, r=Mark-Simulacrum

Add a regression test for #32498

[This](https://github.com/rust-lang/rust/issues/32498#issuecomment-613626968) test mentioned at issue #32498 now passes. This PR adds this regression test.

src/test/ui/generics/issue-32498.rs

@@ -0,0 +1,16 @@
+// run-pass
+#![allow(dead_code)]
+
+// Making sure that no overflow occurs.
+
+struct L<T> {
+    n: Option<T>,
+}
+type L8<T> = L<L<L<L<L<L<L<L<T>>>>>>>>;
+type L64<T> = L8<L8<L8<L8<T>>>>;
+
+fn main() {
+    use std::mem::size_of;
+    assert_eq!(size_of::<L64<L64<()>>>(), 1);
+    assert_eq!(size_of::<L<L64<L64<()>>>>(), 1);
+}