[Bug c/117629] New: Redefinition of bool type in C23 could have better diagnostic

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117629

            Bug ID: 117629
           Summary: Redefinition of bool type in C23 could have better
                    diagnostic
           Product: gcc
           Version: 15.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: sjames at gcc dot gnu.org
  Target Milestone: ---

With -std=gnu23 (the new default), a common issue in applications is:
```
typedef int bool;
```

With gnu23, this errors out as:
```
<source>:1:13: error: two or more data types in declaration specifiers
    1 | typedef int bool;
      |             ^~~~
<source>:1:1: warning: useless type name in empty declaration
    1 | typedef int bool;
      | ^~~~~~~
Compiler returned: 1
```

It'd be nice if we could diagnose what's happening here (bool is a type, please
don't redeclare it, ...).