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
33
34
35
36
|
#![deny(deref_into_dyn_supertrait)]
#![feature(trait_upcasting)] // remove this and the test compiles
use std::ops::Deref;
trait Bar<T> {}
impl<T, U> Bar<U> for T {}
trait Foo: Bar<i32> {
fn as_dyn_bar_u32<'a>(&self) -> &(dyn Bar<u32> + 'a);
}
impl Foo for () {
fn as_dyn_bar_u32<'a>(&self) -> &(dyn Bar<u32> + 'a) {
self
}
}
impl<'a> Deref for dyn Foo + 'a {
type Target = dyn Bar<u32> + 'a;
fn deref(&self) -> &Self::Target {
self.as_dyn_bar_u32()
}
}
fn take_dyn<T>(x: &dyn Bar<T>) -> T {
todo!()
}
fn main() {
let x: &dyn Foo = &();
let y = take_dyn(x);
let z: u32 = y;
//~^ ERROR mismatched types
}
|
