tests/ui/higher-rank-trait-bounds/hrtb-trait-object-paren-notation.rs

   1 // run-pass
   2 // A basic test of using a higher-ranked trait bound.
   3
   4 trait FnLike<A,R> {
   5     fn call(&self, arg: A) -> R;
   6 }
   7
   8 type FnObject<'b> = dyn for<'a> FnLike<(&'a i32,), &'a i32> + 'b;
   9
  10 struct Identity;
  11
  12 impl<'a, T> FnLike<(&'a T,), &'a T> for Identity {
  13     fn call(&self, (arg,): (&'a T,)) -> &'a T {
  14         arg
  15     }
  16 }
  17
  18 fn call_repeatedly(f: &FnObject) {
  19     let x = 3;
  20     let y = f.call((&x,));
  21     assert_eq!(3, *y);
  22 }
  23
  24 fn main() {
  25     call_repeatedly(&Identity);
  26 }