src/test/ui/issues/issue-19098.rs

// build-pass (FIXME(62277): could be check-pass?)
pub trait Handler {
    fn handle(&self, _: &mut String);
}

impl<F> Handler for F where F: for<'a, 'b> Fn(&'a mut String) {
    fn handle(&self, st: &mut String) {
        self(st)
    }
}

fn main() {}