error[E0117]: only traits defined in the current crate can be implemented for arbitrary types --> $DIR/coherence-impls-send.rs:20:1 | LL | unsafe impl Send for (MyType, MyType) {} | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ impl doesn't use types inside crate | = note: the impl does not reference only types defined in this crate = note: define and implement a trait or new type instead error[E0321]: cross-crate traits with a default impl, like `std::marker::Send`, can only be implemented for a struct/enum type, not `&'static NotSync` --> $DIR/coherence-impls-send.rs:24:1 | LL | unsafe impl Send for &'static NotSync {} | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ can't implement cross-crate trait with a default impl for non-struct/enum type error[E0117]: only traits defined in the current crate can be implemented for arbitrary types --> $DIR/coherence-impls-send.rs:28:1 | LL | unsafe impl Send for [MyType] {} | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ impl doesn't use types inside crate | = note: the impl does not reference only types defined in this crate = note: define and implement a trait or new type instead error[E0117]: only traits defined in the current crate can be implemented for arbitrary types --> $DIR/coherence-impls-send.rs:32:1 | LL | unsafe impl Send for &'static [NotSync] {} | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ impl doesn't use types inside crate | = note: the impl does not reference only types defined in this crate = note: define and implement a trait or new type instead error: aborting due to 4 previous errors Some errors have detailed explanations: E0117, E0321. For more information about an error, try `rustc --explain E0117`.