src/test/run-pass/block-fn-coerce.rs

fn force<F>(f: F) -> isize where F: FnOnce() -> isize { return f(); }

pub fn main() {
    fn f() -> isize { return 7; }
    assert_eq!(force(f), 7);
    let g = {||force(f)};
    assert_eq!(g(), 7);
}