rust/tests/ui/higher-ranked/trait-bounds/hrtb-fn-like-trait-object.rs

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// run-pass
// A basic test of using a higher-ranked trait bound.
trait FnLike<A,R> {
fn call(&self, arg: A) -> R;
}
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type FnObject<'b> = dyn for<'a> FnLike<&'a isize, &'a isize> + 'b;
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: &FnObject) {
let x = 3;
let y = f.call(&x);
assert_eq!(3, *y);
}
fn main() {
call_repeatedly(&Identity);
}