40 lines
751 B
Rust
40 lines
751 B
Rust
// Tests that a non-const default impl can be specialized by a const trait impl,
|
|
// but that the default impl cannot be used in a const context.
|
|
// known-bug: #110395
|
|
// FIXME run-pass
|
|
|
|
#![feature(const_trait_impl, effects)]
|
|
#![feature(min_specialization)]
|
|
|
|
#[const_trait]
|
|
trait Value {
|
|
fn value() -> u32;
|
|
}
|
|
|
|
const fn get_value<T: ~const Value>() -> u32 {
|
|
T::value()
|
|
}
|
|
|
|
impl<T> Value for T {
|
|
default fn value() -> u32 {
|
|
println!("You can't do that (constly)");
|
|
0
|
|
}
|
|
}
|
|
|
|
struct FortyTwo;
|
|
|
|
impl const Value for FortyTwo {
|
|
fn value() -> u32 {
|
|
42
|
|
}
|
|
}
|
|
|
|
fn main() {
|
|
let zero = get_value::<()>();
|
|
assert_eq!(zero, 0);
|
|
|
|
const FORTY_TWO: u32 = get_value::<FortyTwo>();
|
|
assert_eq!(FORTY_TWO, 42);
|
|
}
|