Extraneous `$` in macro by example matcher produces suggestion for nonsensica, syntactically invalid fix

[LunarLambda]

Code

macro_rules! repro {
    ($($e:$expr),*) => {}
}

(note the extraneous `$` in `$e:$expr`)

Current output

error: missing fragment specifier
 --> src/lib.rs:2:11
  |
2 |     ($($e:$expr),*) => {}
  |           ^
  |
  = note: fragment specifiers must be provided
  = help: valid fragment specifiers are `ident`, `block`, `stmt`, `expr`, `pat`, `ty`, `lifetime`, `literal`, `path`, `meta`, `tt`, `item` and `vis`, along with `expr_2021` and `pat_param` for edition compatibility
help: try adding a specifier here
  |
2 |     ($($e:$:specexpr),*) => {}
  |            +++++

Desired output

Rationale and extra context

Ideally I would like the diagnostic to point out the $ as extraneous and simply suggest its removal. Or at the very least, produce something that is syntactically correct Rust. even if it's not the code the user "meant" to write.

Other cases

Rust Version

play.rust-lang.org, stable (1.96.0)

Anything else?

No response

[ChronoCoders]

@rustbot claim

[ChronoCoders]

This looks already resolved on current nightly: the suggestion now points at the extraneous $ with "fragment specifiers should not be prefixed with $" and produces $($e:expr),*, which is valid. Appears fixed by a recent change (around 9e2abe0). Releasing in case someone wants to close it.

@rustbot release-assignment

[chenyukang]

it's better to add this as regression test.

[asuto15]

@rustbot claim