| A negative implementation was marked as unsafe. |
| |
| Erroneous code example: |
| |
| ```compile_fail,E0198 |
| struct Foo; |
| |
| unsafe impl !Clone for Foo { } // error! |
| ``` |
| |
| A negative implementation is one that excludes a type from implementing a |
| particular trait. Not being able to use a trait is always a safe operation, |
| so negative implementations are always safe and never need to be marked as |
| unsafe. |
| |
| This will compile: |
| |
| ```ignore (ignore auto_trait future compatibility warning) |
| #![feature(auto_traits)] |
| |
| struct Foo; |
| |
| auto trait Enterprise {} |
| |
| impl !Enterprise for Foo { } |
| ``` |
| |
| Please note that negative impls are only allowed for auto traits. |
