[Bug c++/58046] New: template operator= in SFINAE class

[suibaka at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58046

            Bug ID: 58046
           Summary: template operator= in SFINAE class
           Product: gcc
           Version: 4.7.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: suibaka at gmail dot com

I think the following code should be compile error,
but the result is ICE in gcc-4.7.2.

The error still exists in gcc HEAD.

$ gcc -v
Using built-in specs.
COLLECT_GCC=C:\MinGW\bin\gcc.exe
COLLECT_LTO_WRAPPER=c:/mingw/bin/../libexec/gcc/mingw32/4.7.2/lto-wrapper.exe
Target: mingw32
Configured with: ../gcc-4.7.2/configure
--enable-languages=c,c++,ada,fortran,obj
c,obj-c++ --disable-sjlj-exceptions --with-dwarf2 --enable-shared
--enable-libgo
mp --disable-win32-registry --enable-libstdcxx-debug
--disable-build-poststage1-
with-cxx --enable-version-specific-runtime-libs --build=mingw32 --prefix=/mingw
Thread model: win32
gcc version 4.7.2 (GCC)


The code:

#include <type_traits>

extern void* enabler; 

template <typename T, typename
std::enable_if<std::is_arithmetic<T>::value>::type*& = enabler>
class A
{
public:
    A()
    {}
    template <typename U>
    A& operator=( A<U>&& rhs )
    {
        return *this;
    }
};

int main()
{
    A<int> a_i;
    A<double> a_d;

    a_i = a_d;
}


The error(in 4.7.2):

$ g++ main.cc -Wall -std=c++11
main.cc: In function 'int main()':
main.cc:24:11: internal compiler error: in unify, at cp/pt.c:16956
Please submit a full bug report,
with preprocessed source if appropriate.
See <http://gcc.gnu.org/bugs.html> for instructions.


The error(in HEAD):

prog.cc: In substitution of 'template<class U> A<T, <anonymous> >& A<T,
<anonymous> >::operator=(A<U>&&) [with U = <missing>]':
prog.cc:24:9:   required from here
prog.cc:24:9: internal compiler error: in unify, at cp/pt.c:17384
     a_i = a_d;