tests/ui/traits/const-traits/conditionally-const-and-const-params.rs

#![feature(const_trait_impl)]
#![feature(generic_const_exprs)]
#![allow(incomplete_features)]

struct Foo<const N: usize>;

impl<const N: usize> Foo<N> {
    fn add<A: [const] Add42>(self) -> Foo<{ A::add(N) }> {
        //~^ ERROR `[const]` is not allowed here
        //~| ERROR the trait bound `A: const Add42` is not satisfied
        Foo
    }
}

#[const_trait]
trait Add42 {
    fn add(a: usize) -> usize;
}

impl const Add42 for () {
    fn add(a: usize) -> usize {
        a + 42
    }
}

fn bar<A: [const] Add42, const N: usize>(_: Foo<N>) -> Foo<{ A::add(N) }> {
    //~^ ERROR `[const]` is not allowed here
    //~| ERROR the trait bound `A: const Add42` is not satisfied
    Foo
}

fn main() {
    let foo = Foo::<0>;
    let foo = bar::<(), _>(foo);
    let _foo = bar::<(), _>(foo);
}