Wrong diagnosis for `extern "C" pub fn name() {}`

[aDotInTheVoid]

Code

#[no_mangle]
extern "C" pub fn id(x: i32) -> i32 { x }

Current output

error: expected `{`, found keyword `pub`
 --> error.rs:2:12
  |
2 | extern "C" pub fn id(x: i32) -> i32 { x }
  |            ^^^ expected `{`

error: aborting due to previous error

Desired output

error: expected `{` or `fn`, found keyword `pub`
 --> error.rs:2:12
  |
2 | extern "C" pub fn id(x: i32) -> i32 { x }
  |            ^^^ expected `{`

error: aborting due to previous error

Rationale and extra context

The correct code here is

 extern "C" fn id(x: i32) -> i32 { x }

but the error doesn't suggest that fn keyword would be allowed here.

Ideally we'd recover from this, and say "visibility isn't allowed for extern functions", but if that's not feasible, then we should accurately report the tokens allowed.

Other cases

No response

Anything else?

No response