tests/ui/extern/issue-18819.rs

trait Foo {
    type Item;
}

struct X;

impl Foo for X {
    type Item = bool;
}

fn print_x(_: &dyn Foo<Item=bool>, extra: &str) {
    println!("{}", extra);
}

fn main() {
    print_x(X);
    //~^ ERROR E0061
}