[Bug c++/67371] New: Never executed "throw" in constexpr function fails to compile

[ldionne.2 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67371

            Bug ID: 67371
           Summary: Never executed "throw" in constexpr function fails to
                    compile
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: ldionne.2 at gmail dot com
  Target Milestone: ---

The following code fails to compile on GCC trunk:

    constexpr void f() {
        if (false)
            throw;
    }


The error is:

    [snip]: In function 'constexpr void f()':
    [snip]: error: expression '<throw-expression>' is not a constant-expression
     }
     ^


The code should compile because the throw expression is never executed inside a
constexpr context. Clang indeed compiles this just fine.

Live example: http://melpon.org/wandbox/permlink/V0g96xpWdO2eWGNx