[Bug c/108578] New: typedef inside a struct error message should be improved

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108578

            Bug ID: 108578
           Summary: typedef inside a struct error message should be
                    improved
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Keywords: diagnostic
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pinskia at gcc dot gnu.org
  Target Milestone: ---

Take:
```
struct f {
  typedef int t;
};
```
Currently the C front-end (it is valid C++) gives:
```
<source>:2:3: error: expected specifier-qualifier-list before 'typedef'
    2 |   typedef int t;
      |   ^~~~~~~
```

This error message is correct but the C front-end could mention that something
like typedefs inside the struct scope is not allowed.

clang gives slightly better error message:
```
<source>:2:3: error: type name does not allow storage class to be specified
  typedef int t;
  ^
```

replacing typedef with static gives the same bad error mesage.