1 A negative impl was added on a trait implementation.
3 Erroneous code example:
12 impl !Trait for Foo { } //~ ERROR E0192
17 Negative impls are only allowed for auto traits. For more
18 information see the [opt-in builtin traits RFC][RFC 19].
20 [RFC 19]: https://github.com/rust-lang/rfcs/blob/master/text/0019-opt-in-builtin-traits.md