Fix MSVC compilation error.

The order of the conditions in enable_if_t matters since,
in some cases, the compiler uses short circuit evaluation
of the compile-time constant expressions to simplify
the enable_if condition so that it no longer depends on
the inputs and only depends on the template parameters
of the class being constructed, which, then, causes
an error since that isn't allowed.

Author: insertinterestingnamehere

dynd/include/utility_functions.hpp

@@ -144,7 +144,7 @@ class py_ref_tmpl {
    * Then:
    *    Require that conversions from the other py_ref_tmpl type to this type be explcit.
    */
-  template <bool other_owns, bool other_not_null, typename std::enable_if_t<not_null && !other_not_null> * = nullptr>
+  template <bool other_owns, bool other_not_null, typename std::enable_if_t<!other_not_null && not_null> * = nullptr>
   explicit py_ref_tmpl(const py_ref_tmpl<other_owns, other_not_null> &other) noexcept
   {
     o = other.o;
@@ -161,7 +161,7 @@ class py_ref_tmpl {
    * Then:
    *    a move operation can be implicitly performed.
    */
-  template <bool other_not_null, typename std::enable_if_t<owns_ref && (other_not_null || !not_null)> * = nullptr>
+  template <bool other_not_null, typename std::enable_if_t<(other_not_null || !not_null) && owns_ref> * = nullptr>
   py_ref_tmpl(py_ref_tmpl<true, other_not_null> &&other) noexcept
   {
     o = other.o;
@@ -173,7 +173,7 @@ class py_ref_tmpl {
    * Then:
    *    only an explicit move operation can be performed.
    */
-  template <bool other_not_null, typename std::enable_if_t<owns_ref && !other_not_null && not_null> * = nullptr>
+  template <bool other_not_null, typename std::enable_if_t<!other_not_null && not_null && owns_ref> * = nullptr>
   explicit py_ref_tmpl(py_ref_tmpl<true, other_not_null> &&other) noexcept
   {
     o = other.o;
@@ -216,7 +216,7 @@ class py_ref_tmpl {
    *    Allow assignment from the other py_ref_tmpl type to this type.
    */
   template <bool other_owns, bool other_not_null,
-            typename std::enable_if_t<!not_null || (not_null && other_not_null)> * = nullptr>
+            typename std::enable_if_t<(other_not_null && not_null) || !not_null> * = nullptr>
   py_ref_tmpl<owns_ref, not_null> operator=(const py_ref_tmpl<other_owns, other_not_null> &other) noexcept
   {
     decref_if_owned<owns_ref, not_null>(o);