Macro "missing fragment specifier" when accidentally prefixed with $

[DanielEScherzer]

Code

#[allow(unused)]
macro_rules! demo {
    ( $test:$tt ) => {
        
    }
}

Current output

Compiling playground v0.0.1 (/playground)
error: missing fragment specifier
 --> src/lib.rs:3:13
  |
3 |     ( $test:$tt ) => {
  |             ^
  |
  = 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
  |
3 |     ( $test:$:spectt ) => {
  |              +++++

error: could not compile `playground` (lib) due to 1 previous error

Desired output

Compiling playground v0.0.1 (/playground)
error: missing fragment specifier
 --> src/lib.rs:3:13
  |
3 |     ( $test:$tt ) => {
  |             ^
  |
  = 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: fragment specifiers should not be prefixed with $
  |
3 |     ( $test:tt ) => {
  |             -

error: could not compile `playground` (lib) due to 1 previous error

Rationale and extra context

I accidentally wrote $test:$tt instead of $test:tt and the suggestion was to add :spec in the wrong place, but even if the place was fixed given that I was trying to add the fragment specifier the error message should adjust for that

Other cases

Rust Version

Stable 1.95.0 via playground

Anything else?

No response

[DanielEScherzer]

@rustbot label +A-macros

[qaijuang]

Interesting, i'll look into this one