rust/src/test/ui/run-pass/unboxed-closures/unboxed-closures-extern-fn-hr.rs

// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

// Checks that higher-ranked extern fn pointers implement the full range of Fn traits.

fn square(x: &isize) -> isize { (*x) * (*x) }

fn call_it<F:Fn(&isize)->isize>(f: &F, x: isize) -> isize {
    (*f)(&x)
}

fn call_it_boxed(f: &Fn(&isize) -> isize, x: isize) -> isize {
    f(&x)
}

fn call_it_mut<F:FnMut(&isize)->isize>(f: &mut F, x: isize) -> isize {
    (*f)(&x)
}

fn call_it_once<F:FnOnce(&isize)->isize>(f: F, x: isize) -> isize {
    f(&x)
}

fn main() {
    let x = call_it(&square, 22);
    let x1 = call_it_boxed(&square, 22);
    let y = call_it_mut(&mut square, 22);
    let z = call_it_once(square, 22);
    assert_eq!(x, square(&22));
    assert_eq!(x1, square(&22));
    assert_eq!(y, square(&22));
    assert_eq!(z, square(&22));
}