add test for issue 97607

src/test/ui/closures/issue-97607.rs

@@ -0,0 +1,12 @@
+// check-pass
+#[allow(unused)]
+
+fn test<T, F, U>(f: F) -> Box<dyn Fn(T) -> U + 'static>
+where
+    F: 'static + Fn(T) -> U,
+    for<'a> U: 'a, // < This is the problematic line, see #97607
+{
+    Box::new(move |t| f(t))
+}
+
+fn main() {}