3 #![feature(specialization)] //~ WARN the feature `specialization` is incomplete
5 trait Foo: std::fmt::Debug + Eq {}
7 impl<T: std::fmt::Debug + Eq> Foo for T {}
9 fn hide<T: Foo>(x: T) -> impl Foo {
13 trait Leak<T>: Sized {
16 impl<T, U> Leak<T> for U {
17 default fn leak(self) -> T { panic!("type mismatch") }
19 impl<T> Leak<T> for T {
20 fn leak(self) -> T { self }
23 trait CheckIfSend: Sized {
25 fn check(self) -> Self::T { Default::default() }
27 impl<T> CheckIfSend for T {
30 impl<T: Send> CheckIfSend for T {
34 fn lucky_seven() -> impl Fn(usize) -> u8 {
35 let a = [1, 2, 3, 4, 5, 6, 7];
40 assert_eq!(hide(42), hide(42));
42 assert_eq!(std::mem::size_of_val(&hide([0_u8; 5])), 5);
43 assert_eq!(std::mem::size_of_val(&lucky_seven()), 7);
45 assert_eq!(Leak::<i32>::leak(hide(5_i32)), 5_i32);
47 assert_eq!(CheckIfSend::check(hide(0_i32)), false);