Add enable_if_t to workaround.

Author: rwgk

include/pybind11/operators.h

@@ -84,6 +84,13 @@ struct op_impl {};
 /// Operator implementation generator
 template <op_id id, op_type ot, typename L, typename R>
 struct op_ {
+#if defined(__CUDACC__) && (__CUDACC_VER_MAJOR__ == 11) && (__CUDACC_VER_MINOR__ >= 4)            \
+    && (__CUDACC_VER_MINOR__ <= 8)
+// Nvidia's NVCC is broken between 11.4.0 and 11.8.0
+//   https://github.com/pybind/pybind11/issues/4193
+#    define PYBIND11_USING_WORKAROUND_FOR_CUDA_11_4_THROUGH_8
+    static constexpr bool op_enable_if_hook = true;
+#endif
     template <typename Class, typename... Extra>
     void execute(Class &cl, const Extra &...extra) const {
         using Base = typename Class::type;

include/pybind11/pybind11.h

@@ -1578,17 +1578,14 @@ class class_ : public detail::generic_type {
         return *this;
     }
 
-// Nvidia's NVCC is broken between 11.4.0 and 11.8.0
-//   https://github.com/pybind/pybind11/issues/4193
-#if defined(__CUDACC__) && (__CUDACC_VER_MAJOR__ == 11) && (__CUDACC_VER_MINOR__ >= 4)            \
-    && (__CUDACC_VER_MINOR__ <= 8)
-    template <typename T, typename... Extra>
+#if defined(PYBIND11_USING_WORKAROUND_FOR_CUDA_11_4_THROUGH_8)
+    template <typename T, typename... Extra, detail::enable_if_t<T::op_enable_if_hook, int> = 0>
     class_ &def(const T &op, const Extra &...extra) {
         op.execute(*this, extra...);
         return *this;
     }
 
-    template <typename T, typename... Extra>
+    template <typename T, typename... Extra, detail::enable_if_t<T::op_enable_if_hook, int> = 0>
     class_ &def_cast(const T &op, const Extra &...extra) {
         op.execute_cast(*this, extra...);
         return *this;