[Bug c++/125492] New: [reflection] Misleading error message when `std::meta::size_of` is applied to a reflected function type

[ensadc at mailnesia dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=125492

            Bug ID: 125492
           Summary: [reflection] Misleading error message when
                    `std::meta::size_of` is applied to a reflected
                    function type
           Product: gcc
           Version: 17.0
            Status: UNCONFIRMED
          Keywords: diagnostic
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: ensadc at mailnesia dot com
  Target Milestone: ---

https://gcc.godbolt.org/z/7Y1ePaM1h
====
#include <meta>

constexpr auto a = std::meta::size_of(^^void());

====
<source>:3:47: error: uncaught exception of type 'std::meta::exception';
'what()': 'reflection with incomplete type in size_of'
    3 | constexpr auto a = std::meta::size_of(^^void());
      |                                               ^

====
The error message does not make sense: `void()` is not an incomplete type; it's
a function type.