[Bug c++/107104] New: semantics of __builtin_constant_p within static_assert and return value

[me at inclyc dot cn]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107104

            Bug ID: 107104
           Summary: semantics of __builtin_constant_p within static_assert
                    and return value
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: me at inclyc dot cn
  Target Milestone: ---

https://godbolt.org/z/oz4e7bobT
https://godbolt.org/z/hE6x9G49q

illustrate different occasions about this issue. 

Consider passing the same operand __builtin_constant_p in static assertions and
return value, expression with in static assertion passed, but the same
expression evaluates to 0 as the return value.

Are there some different scopes / contexts that causes different result?

Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91158
Link: https://github.com/llvm/llvm-project/issues/58078