fix mp_replace_at with msvc-12

Author: jonathanpoelen

include/boost/mp11/algorithm.hpp

@@ -1047,6 +1047,8 @@ template<class L, class Q> using mp_any_of_q = mp_any_of<L, Q::template fn>;
 namespace detail
 {
 
+#if ! BOOST_MP11_WORKAROUND( BOOST_MP11_MSVC, < 1900 )
+
 template<class I> struct mp_replace_at_impl_p
 {
     template<class T1, class T2> using _p = std::is_same<T2, I>;
@@ -1057,12 +1059,24 @@ template<class W> struct mp_replace_at_impl_f
     template<class T1, class T2> using _f = W;
 };
 
+#endif
+
 template<class L, class I, class W> struct mp_replace_at_impl
 {
     static_assert( I::value >= 0, "mp_replace_at<L, I, W>: I must not be negative" );
 
+#if ! BOOST_MP11_WORKAROUND( BOOST_MP11_MSVC, < 1900 )
+
+    template<class T1, class T2> using _p = std::is_same<T2, mp_size_t<I::value>>;
+    template<class T1, class T2> using _f = W;
+
+    using type = mp_transform_if<_p, _f, L, mp_iota<mp_size<L> > >;
+
+#else
 
     using type = mp_transform_if<mp_replace_at_impl_p<mp_size_t<I::value>>::template _p, mp_replace_at_impl_f<W>::template _f, L, mp_iota<mp_size<L> > >;
+
+#endif
 };
 
 } // namespace detail