src/test/ui/type-alias-impl-trait/issue-57611-trait-alias.rs

// Regression test for issue #57611
// Ensures that we don't ICE
// FIXME: This should compile, but it currently doesn't

#![feature(trait_alias)]
// revisions: min_tait full_tait
#![feature(min_type_alias_impl_trait)]
#![cfg_attr(full_tait, feature(type_alias_impl_trait))]
//[full_tait]~^ WARN incomplete

trait Foo {
    type Bar: Baz<Self, Self>;

    fn bar(&self) -> Self::Bar;
}

struct X;

impl Foo for X {
    type Bar = impl Baz<Self, Self>;
    //~^ ERROR implementation of `FnOnce` is not general enough
    //~| ERROR implementation of `FnOnce` is not general enough
    //~| ERROR implementation of `FnOnce` is not general enough
    //~| ERROR mismatched types
    //~| ERROR mismatched types

    fn bar(&self) -> Self::Bar {
        |x| x
    }
}

trait Baz<A: ?Sized, B: ?Sized> = Fn(&A) -> &B;

fn main() {}