rust/tests/ui/specialization/specialization-overlap-projection.rs

// Test that impls on projected self types can resolve overlap, even when the
// projections involve specialization, so long as the associated type is
// provided by the most specialized impl.
#![feature(specialization)]
//~^ WARN the feature `specialization` is incomplete and may not be safe to use and/or cause compiler crashes

trait Assoc {
    type Output;
}

impl<T> Assoc for T {
    default type Output = bool;
}

impl Assoc for u8 { type Output = u8; }
impl Assoc for u16 { type Output = u16; }

trait Foo {}
impl Foo for u32 {}
impl Foo for <u8 as Assoc>::Output {}
//~^ ERROR conflicting implementations of trait `Foo` for type `u32`
impl Foo for <u16 as Assoc>::Output {}
//~^ ERROR conflicting implementations of trait `Foo` for type `u32`

fn main() {}