Add regression test

src/test/ui/type-alias-impl-trait/issue-93411.rs

@@ -0,0 +1,19 @@
+#![feature(type_alias_impl_trait)]
+
+// this test used to stack overflow due to infinite recursion.
+// check-pass
+// compile-flags: --edition=2018
+
+use std::future::Future;
+
+fn main() {
+    let _ = move || async move {
+        let value = 0u8;
+        blah(&value).await;
+    };
+}
+
+type BlahFut<'a> = impl Future<Output = ()> + Send + 'a;
+fn blah<'a>(_value: &'a u8) -> BlahFut<'a> {
+    async {}
+}