Instantiate closure-like bounds with placeholders to deal with binders correctly

1 files changed, 51 insertions, 0 deletions

diff --git a/tests/ui/higher-ranked/builtin-closure-like-bounds.rs b/tests/ui/higher-ranked/builtin-closure-like-bounds.rs
new file mode 100644
index 00000000000..c7dfaefbc74
--- /dev/null
+++ b/tests/ui/higher-ranked/builtin-closure-like-bounds.rs
@@ -0,0 +1,51 @@
+//@ edition:2024
+//@ compile-flags: -Zunstable-options
+//@ revisions: current next
+//@[next] compile-flags: -Znext-solver
+
+#![feature(unboxed_closures, gen_blocks)]
+
+trait Dispatch {
+    fn dispatch(self);
+}
+
+struct Fut<T>(T);
+impl<T: for<'a> Fn<(&'a (),)>> Dispatch for Fut<T>
+where
+    for<'a> <T as FnOnce<(&'a (),)>>::Output: Future,
+{
+    fn dispatch(self) {
+        (self.0)(&());
+    }
+}
+
+struct Gen<T>(T);
+impl<T: for<'a> Fn<(&'a (),)>> Dispatch for Gen<T>
+where
+    for<'a> <T as FnOnce<(&'a (),)>>::Output: Iterator,
+{
+    fn dispatch(self) {
+        (self.0)(&());
+    }
+}
+
+struct Closure<T>(T);
+impl<T: for<'a> Fn<(&'a (),)>> Dispatch for Closure<T>
+where
+    for<'a> <T as FnOnce<(&'a (),)>>::Output: Fn<(&'a (),)>,
+{
+    fn dispatch(self) {
+        (self.0)(&())(&());
+    }
+}
+
+fn main() {
+    async fn foo(_: &()) {}
+    Fut(foo).dispatch();
+
+    gen fn bar(_: &()) {}
+    Gen(bar).dispatch();
+
+    fn uwu<'a>(x: &'a ()) -> impl Fn(&'a ()) { |_| {} }
+    Closure(uwu).dispatch();
+}
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