blob: e4e0f634ef76e571ae63b11ca3975e8a55ade24a (
plain)
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
37
38
39
|
// revisions: old next
//[next] compile-flags: -Ztrait-solver=next
// run-pass
// A test for https://github.com/rust-lang/trait-system-refactor-initiative/issues/45.
trait Trait {
type Assoc: Into<u32>;
}
impl<T: Into<u32>> Trait for T {
type Assoc = T;
}
fn prefer_alias_bound_projection<T: Trait>(x: T::Assoc) {
// There are two possible types for `x`:
// - `u32` by using the "alias bound" of `<T as Trait>::Assoc`
// - `<T as Trait>::Assoc`, i.e. `u16`, by using `impl<T> From<T> for T`
//
// We infer the type of `x` to be `u32` here as it is highly likely
// that this is expected by the user.
let x = x.into();
assert_eq!(std::mem::size_of_val(&x), 4);
}
fn impl_trait() -> impl Into<u32> {
0u16
}
fn main() {
// There are two possible types for `x`:
// - `u32` by using the "alias bound" of `impl Into<u32>`
// - `impl Into<u32>`, i.e. `u16`, by using `impl<T> From<T> for T`
//
// We infer the type of `x` to be `u32` here as it is highly likely
// that this is expected by the user.
let x = impl_trait().into();
assert_eq!(std::mem::size_of_val(&x), 4);
prefer_alias_bound_projection::<u16>(1);
}
|
