error[E0119]: conflicting implementations of trait `AnotherTrait` for type `D` --> $DIR/negative-reasoning.rs:19:1 | LL | impl AnotherTrait for T {} | ------------------------------------------- first implementation here ... LL | impl AnotherTrait for D { | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `D` | = note: upstream crates may add a new impl of trait `std::fmt::Debug` for type `OpaqueType` in future versions error: aborting due to previous error For more information about this error, try `rustc --explain E0119`.