error[E0200]: the trait `UnsafeTrait` requires an `unsafe impl` declaration --> $DIR/safety-trait-impl.rs:14:1 | LL | impl UnsafeTrait for u16 { } | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | = note: the trait `UnsafeTrait` enforces invariants that the compiler can't check. Review the trait documentation and make sure this implementation upholds those invariants before adding the `unsafe` keyword help: add `unsafe` to this trait implementation | LL | unsafe impl UnsafeTrait for u16 { } | ++++++ error[E0199]: implementing the trait `SafeTrait` is not unsafe --> $DIR/safety-trait-impl.rs:16:1 | LL | unsafe impl SafeTrait for u32 { } | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | help: remove `unsafe` from this trait implementation | LL - unsafe impl SafeTrait for u32 { } LL + impl SafeTrait for u32 { } | error: aborting due to 2 previous errors Some errors have detailed explanations: E0199, E0200. For more information about an error, try `rustc --explain E0199`.