compiler/rustc_error_codes/src/error_codes/E0800.md

A type or const parameter of the given name is not in scope.

Erroneous code examples:

```compile_fail,E0800
fn missing() -> impl Sized + use<T> {}
```

To fix this error, please verify you didn't misspell the type or const
parameter, or double-check if you forgot to declare the parameter in
the list of generics.