1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
|
#![feature(generic_const_exprs)]
#![allow(incomplete_features)]
use std::marker::PhantomData;
trait SadBee {
const ASSOC: usize;
}
// `fn(&'static ())` is a supertype of `for<'a> fn(&'a ())` while
// we allow two different impls for these types, leading
// to different const eval results.
impl SadBee for for<'a> fn(&'a ()) {
const ASSOC: usize = 0;
}
impl SadBee for fn(&'static ()) {
//~^ WARN conflicting implementations of trait
//~| WARN the behavior may change in a future release
const ASSOC: usize = 100;
}
struct Foo<T: SadBee>([u8; <T as SadBee>::ASSOC], PhantomData<T>)
where
[(); <T as SadBee>::ASSOC]:;
fn covariant(v: &'static Foo<for<'a> fn(&'a ())>) -> &'static Foo<fn(&'static ())> {
v
//~^ ERROR mismatched types
}
fn main() {
let y = covariant(&Foo([], PhantomData));
println!("{:?}", y.0);
}
|
