#![feature(negative_impls)] #![feature(marker_trait_attr)] #[marker] trait MyTrait {} struct TestType(::std::marker::PhantomData); unsafe impl Send for TestType {} impl !Send for TestType {} //~^ ERROR found both positive and negative implementation //~| ERROR `!Send` impl requires `T: MyTrait` but the struct it is implemented for does not unsafe impl Send for TestType {} //~^ ERROR conflicting implementations impl !Send for TestType {} //~^ ERROR `!Send` impls cannot be specialized fn main() {}