Error code E0198

A negative implementation was marked as unsafe.

Erroneous code example:

#![allow(unused)] fn main() { 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:

#![feature(auto_traits)] struct Foo; auto trait Enterprise {} impl !Enterprise for Foo { }

Please note that negative impls are only allowed for auto traits.