Want better error for impl<some generics> impl Trait for Type {...}

[ijackson]

Code

use std::panic::UnwindSafe;

struct S<T>(T);

impl<T: UnwindSafe> impl UnwindSafe for T {}

// We're using UnwindSafe as an example trait

Current output

error: expected a trait, found type
 --> src/lib.rs:5:21
  |
5 | impl<T: UnwindSafe> impl UnwindSafe for T {}
  |                     ^^^^^^^^^^^^^^^

Desired output

error: expected a trait, found type
 --> src/lib.rs:5:21
  |
5 | impl<T: UnwindSafe> impl UnwindSafe for T {}
  |                     ^^^^^^^^^^^^^^^

 --> src/lib.rs:5:21
  |
5 | impl<T: UnwindSafe> impl UnwindSafe for T {}
  | ^^^^                ^^^^
note: second occurrence of keyword `impl` is probably a mistake

Rationale and extra context

I made this mistake and didn't spot that the ^^^^ were pointing at the whole of impl Trait rather than just Trait and spent several minutes thinking "but Trait is a trait!".

Probably my "desired output" could be improved. Maybe replacing rather than supplementing the "expected trait, not type" would be better.

Other cases

No response

Anything else?

No response