error[E0751]: found both positive and negative implementation of trait `std::marker::Send` for type `TestType<_>`: --> $DIR/specialization-overlap-negative.rs:9:1 | LL | unsafe impl Send for TestType {} | ------------------------------------------ positive implementation here LL | impl !Send for TestType {} | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ negative implementation here error: aborting due to previous error For more information about this error, try `rustc --explain E0751`.