Add test for futures with HRTB

Author: dswij

tests/ui/higher-ranked/trait-bounds/future.rs

@@ -0,0 +1,30 @@
+// edition:2021
+// revisions: classic next
+//[next] compile-flags: -Ztrait-solver=next
+//[next] check-pass
+
+#![feature(unboxed_closures)]
+
+use std::future::Future;
+
+trait Trait {
+    fn func(&self, _: &str);
+}
+
+impl<T> Trait for T
+where
+    for<'a> T: Fn<(&'a str,)> + Send + Sync,
+    for<'a> <T as FnOnce<(&'a str,)>>::Output: Future<Output = usize> + Send,
+{
+    fn func(&self, _: &str) {
+        println!("hello!");
+    }
+}
+
+async fn strlen(x: &str) -> usize {
+    x.len()
+}
+
+fn main() {
+    strlen.func("hi");
+}