add test for ice future has no bound vars.

Fixes #112347

Author: matthiaskrgr

tests/ui/impl-trait/future-no-bound-vars-ice-112347.rs

@@ -0,0 +1,29 @@
+// issue: rust-lang/rust#112347
+// ICE future has no bound vars
+//@ edition:2021
+//@ check-pass
+
+#![feature(type_alias_impl_trait)]
+
+use std::future::Future;
+
+type Fut<'a> = impl Future<Output = ()> + 'a;
+
+fn foo<'a>(_: &()) -> Fut<'_> {
+    async {}
+}
+
+trait Test {
+    fn hello();
+}
+
+impl Test for ()
+where
+    for<'a> Fut<'a>: Future<Output = ()>,
+{
+    fn hello() {}
+}
+
+fn main() {
+    <()>::hello();
+}