error[E0751]: found both positive and negative implementation of trait `Send` for type `TestType<_>`: --> $DIR/issue-106755.rs:13:1 | LL | unsafe impl Send for TestType {} | ------------------------------------------------------ positive implementation here LL | LL | impl !Send for TestType {} | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ negative implementation here error[E0119]: conflicting implementations of trait `Send` for type `TestType<_>` --> $DIR/issue-106755.rs:15:1 | LL | unsafe impl Send for TestType {} | ------------------------------------------------------ first implementation here ... LL | unsafe impl Send for TestType {} | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `TestType<_>` warning: cross-crate traits with a default impl, like `Send`, should not be specialized --> $DIR/issue-106755.rs:17:1 | LL | impl !Send for TestType {} | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | = warning: this will change its meaning in a future release! = note: for more information, see issue #93367 = note: `i32` is not a generic parameter note: try using the same sequence of generic parameters as the struct definition --> $DIR/issue-106755.rs:9:1 | LL | struct TestType(::std::marker::PhantomData); | ^^^^^^^^^^^^^^^^^^ = note: `#[warn(suspicious_auto_trait_impls)]` on by default error: aborting due to 2 previous errors; 1 warning emitted Some errors have detailed explanations: E0119, E0751. For more information about an error, try `rustc --explain E0119`.