1 files changed, 65 insertions, 0 deletions
diff --git a/tests/ui/closures/supertrait-hint-cycle.rs b/tests/ui/closures/supertrait-hint-cycle.rs
new file mode 100644
index 00000000000..dbb06b2ef7a
--- /dev/null
+++ b/tests/ui/closures/supertrait-hint-cycle.rs
@@ -0,0 +1,65 @@
+// edition:2021
+// check-pass
+
+#![feature(type_alias_impl_trait)]
+#![feature(closure_lifetime_binder)]
+
+use std::future::Future;
+
+trait AsyncFn<I, R>: FnMut(I) -> Self::Fut {
+    type Fut: Future<Output = R>;
+}
+
+impl<F, I, R, Fut> AsyncFn<I, R> for F
+where
+    Fut: Future<Output = R>,
+    F: FnMut(I) -> Fut,
+{
+    type Fut = Fut;
+}
+
+async fn call<C, R, F>(mut ctx: C, mut f: F) -> Result<R, ()>
+where
+    F: for<'a> AsyncFn<&'a mut C, Result<R, ()>>,
+{
+    loop {
+        match f(&mut ctx).await {
+            Ok(val) => return Ok(val),
+            Err(_) => continue,
+        }
+    }
+}
+
+trait Cap<'a> {}
+impl<T> Cap<'_> for T {}
+
+fn works(ctx: &mut usize) {
+    let mut inner = 0;
+
+    type Ret<'a, 'b: 'a> = impl Future<Output = Result<usize, ()>> + 'a + Cap<'b>;
+
+    let callback = for<'a, 'b> |c: &'a mut &'b mut usize| -> Ret<'a, 'b> {
+        inner += 1;
+        async move {
+            let _c = c;
+            Ok(1usize)
+        }
+    };
+    call(ctx, callback);
+}
+
+fn doesnt_work_but_should(ctx: &mut usize) {
+    let mut inner = 0;
+
+    type Ret<'a, 'b: 'a> = impl Future<Output = Result<usize, ()>> + 'a + Cap<'b>;
+
+    call(ctx, for<'a, 'b> |c: &'a mut &'b mut usize| -> Ret<'a, 'b> {
+        inner += 1;
+        async move {
+            let _c = c;
+            Ok(1usize)
+        }
+    });
+}
+
+fn main() {}