error[E0119]: conflicting implementations of trait `std::marker::Send` for type `TestType<_>`: --> $DIR/specialization-overlap-negative.rs:9:1 | LL | unsafe impl Send for TestType {} | ------------------------------------------ first implementation here LL | impl !Send for TestType {} //~ ERROR E0119 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `TestType<_>` error: aborting due to previous error For more information about this error, try `rustc --explain E0119`.