compiler/rustc_error_codes/src/error_codes/E0701.md

#### Note: this error code is no longer emitted by the compiler.

This error indicates that a `#[non_exhaustive]` attribute was incorrectly placed
on something other than a struct or enum.

Erroneous code example:

```ignore (no longer emitted)
#[non_exhaustive]
trait Foo { }
```