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
|
//@ check-pass
//@ known-bug: #40582
// Should fail. Should not be possible to implement `make_static`.
#![feature(specialization)]
#![allow(incomplete_features)]
trait FromRef<'a, T: ?Sized> {
fn from_ref(r: &'a T) -> Self;
}
impl<'a, T: ?Sized> FromRef<'a, T> for &'a T {
fn from_ref(r: &'a T) -> Self {
r
}
}
impl<'a, T: ?Sized, R> FromRef<'a, T> for R {
default fn from_ref(_: &'a T) -> Self {
unimplemented!()
}
}
fn make_static<T: ?Sized>(data: &T) -> &'static T {
fn helper<T: ?Sized, R>(data: &T) -> R {
R::from_ref(data)
}
helper(data)
}
fn main() {
let s = "specialization".to_owned();
println!("{:?}", make_static(s.as_str()));
}
|
