[Bug c++/56065] New: Constant expression incorrectly recognized not as such

[lucdanton at free dot fr]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56065



             Bug #: 56065

           Summary: Constant expression incorrectly recognized not as such

    Classification: Unclassified

           Product: gcc

           Version: 4.8.0

            Status: UNCONFIRMED

          Severity: normal

          Priority: P3

         Component: c++

        AssignedTo: unassig...@gcc.gnu.org

        ReportedBy: lucdan...@free.fr





$ gcc-snapshot --version

gcc-snapshot (Debian 20130113-1) 4.8.0 20130113 (experimental) [trunk revision

195136]



$ cat main.cpp 

#include <type_traits>



template<typename T>

constexpr T id(T t) { return t; }



template<int I>

using Alias = std::integral_constant<int, I>;



template<int I>

std::integral_constant<int, id(I)> f()

{ return {}; }



template<int I>

Alias<id(I)> g()

{ return {}; }



int main()

{

    // Fine

    constexpr auto I = id(5);

    (void)I;



    // Also fine

    f<0>();



    // error: integral expression 'id<int>(0)' is not constant

    g<0>();

}