rustc/tests/ui/associated-consts/infer-placeholder-in-non-suggestable-pos.rs

trait Trait {
    const ASSOC: i32;
}

impl Trait for () {
    const ASSOC: &dyn Fn(_) = 1i32;
    //~^ ERROR the placeholder `_` is not allowed within types on item signatures for associated constants
}

fn main() {}