On 17/08/2017 12:45, Vladimir Batov wrote:
Thanks, Gavin. Is it how it is done these days? Nice. Incorporated. Many thanks... clang still fails... now I am starting to look suspiciously in clang's direction.
FYI, the complete program: #include <type_traits> template <typename T> class has_impl_ptr_type { template <typename T1> static typename T1::impl_ptr_type test(int); template <typename> static void test(...); public: enum { value = !std::is_void<decltype(test<T>(0))>::value }; }; struct A { }; struct B { typedef int impl_ptr_type; }; static_assert(!has_impl_ptr_type<A>::value, ""); static_assert( has_impl_ptr_type<B>::value, ""); static_assert( has_impl_ptr_type<B const>::value, ""); int main() { return 0; } Compiles successfully for me with -std=c++11 on gcc 5.4.0 and clang 3.8.0, as well as VS2015. So unless this is some kind of regression in clang-4, your problem probably lies elsewhere.