[Bug c++/113153] New: suboptimal error message when using reserved identifier

[michael.kenzel at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113153

            Bug ID: 113153
           Summary: suboptimal error message when using reserved
                    identifier
           Product: gcc
           Version: 13.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: michael.kenzel at gmail dot com
  Target Milestone: ---

When using a keyword as the name of an enum, gcc will issue a diagnostic about
the enum being "unnamed". This can be very confusing:

    enum class register { rax, rcx, rdx, rbx };

compiled with -std=c++23 produces

error: unnamed scoped enum is not allowed
    1 | enum class register {};
      |            ^~~~~~~~
warning: elaborated-type-specifier for a scoped enum must not use the 'class'
keyword
    1 | enum class register {};
      | ~~~~ ^~~~~
      |      -----
error: expected identifier before 'register'
    1 | enum class register {};
      |            ^~~~~~~~
error: expected unqualified-id before '{' token
    1 | enum class register {};
      |                     ^

https://godbolt.org/z/s1ocevaWe