rust/tests/ui/diagnostic_namespace/on_unimplemented/on_unimplemented_simple.rs

#![feature(diagnostic_namespace)]

#[diagnostic::on_unimplemented(message = "Foo", label = "Bar", note = "Baz")]
trait Foo {}

fn takes_foo(_: impl Foo) {}

fn main() {
    takes_foo(());
    //~^ERROR Foo
}