28 lines
445 B
Rust
28 lines
445 B
Rust
//@ run-pass
|
|
// A basic test of using a higher-ranked trait bound.
|
|
|
|
|
|
trait FnLike<A,R> {
|
|
fn call(&self, arg: A) -> R;
|
|
}
|
|
|
|
struct Identity;
|
|
|
|
impl<'a, T> FnLike<&'a T, &'a T> for Identity {
|
|
fn call(&self, arg: &'a T) -> &'a T {
|
|
arg
|
|
}
|
|
}
|
|
|
|
fn call_repeatedly<F>(f: F)
|
|
where F : for<'a> FnLike<&'a isize, &'a isize>
|
|
{
|
|
let x = 3;
|
|
let y = f.call(&x);
|
|
assert_eq!(3, *y);
|
|
}
|
|
|
|
fn main() {
|
|
call_repeatedly(Identity);
|
|
}
|