45 lines
789 B
Rust
45 lines
789 B
Rust
//@ check-pass
|
|
//@ known-bug: #74629
|
|
|
|
// Should fail. The `0` and `1` impls overlap, violating coherence. Eg, with
|
|
// `T = Test, F = ()`, all bounds are true, making both impls applicable.
|
|
// `Test: Fold<Nil>`, `Test: Fold<()>` are true because of `2`.
|
|
// `Is<Test>: NotNil` is true because of `auto trait` and lack of negative impl.
|
|
|
|
#![feature(negative_impls)]
|
|
#![feature(auto_traits)]
|
|
|
|
struct Nil;
|
|
struct Cons<H>(H);
|
|
struct Test;
|
|
|
|
trait Fold<F> {}
|
|
|
|
impl<T, F> Fold<F> for Cons<T>
|
|
// 0
|
|
where
|
|
T: Fold<Nil>,
|
|
{
|
|
}
|
|
|
|
impl<T, F> Fold<F> for Cons<T>
|
|
// 1
|
|
where
|
|
T: Fold<F>,
|
|
private::Is<T>: private::NotNil,
|
|
{
|
|
}
|
|
|
|
impl<F> Fold<F> for Test {} // 2
|
|
|
|
mod private {
|
|
use crate::Nil;
|
|
|
|
pub struct Is<T>(T);
|
|
pub auto trait NotNil {}
|
|
|
|
impl !NotNil for Is<Nil> {}
|
|
}
|
|
|
|
fn main() {}
|