Workaround build failure on MSVC

It seems that MSVC doesn't expand `__VA_ARGS__` in a macro call, so the
introspection of `P11X_ENUM_TYPE` doesn't work. Instead, just pass the
type we want manually.

Author: QuLogic

src/_enums.h

@@ -20,11 +20,6 @@
 //
 //   Place this in PYBIND11_MODULE to register the enums declared by P11X_DECLARE_ENUM.
 
-// a1 includes the opening brace and a2 the closing brace.
-// This definition is compatible with older compiler versions compared to
-// #define P11X_ENUM_TYPE(...) decltype(std::map{std::pair __VA_ARGS__})::mapped_type
-#define P11X_ENUM_TYPE(a1, a2, ...) decltype(std::pair a1, a2)::second_type
-
 #define P11X_CAT2(a, b) a##b
 #define P11X_CAT(a, b) P11X_CAT2(a, b)
 
@@ -51,7 +46,7 @@ namespace p11x {
 
 // Immediately converting the args to a vector outside of the lambda avoids
 // name collisions.
-#define P11X_DECLARE_ENUM(py_name, py_base_cls, ...) \
+#define P11X_DECLARE_ENUM(py_name, py_base_cls, cpp_type, ...) \
   namespace p11x { \
     namespace { \
       [[maybe_unused]] auto const P11X_CAT(enum_placeholder_, __COUNTER__) = \
@@ -68,10 +63,9 @@ namespace p11x {
     } \
   } \
   namespace pybind11::detail { \
-    template<> struct type_caster<P11X_ENUM_TYPE(__VA_ARGS__)> { \
-      using type = P11X_ENUM_TYPE(__VA_ARGS__); \
-      static_assert(std::is_enum_v<type>, "Not an enum"); \
-      PYBIND11_TYPE_CASTER(type, _(py_name)); \
+    template<> struct type_caster<cpp_type> { \
+      static_assert(std::is_enum_v<cpp_type>, "Not an enum"); \
+      PYBIND11_TYPE_CASTER(cpp_type, _(py_name)); \
       bool load(handle src, bool) { \
         auto cls = p11x::enums.at(py_name); \
         PyObject* tmp = nullptr; \
@@ -87,7 +81,7 @@ namespace p11x {
       } \
       static handle cast(decltype(value) obj, return_value_policy, handle) { \
         auto cls = p11x::enums.at(py_name); \
-        return cls(std::underlying_type_t<type>(obj)).inc_ref(); \
+        return cls(std::underlying_type_t<cpp_type>(obj)).inc_ref(); \
       } \
     }; \
   }

src/ft2font_wrapper.cpp

@@ -28,7 +28,7 @@ const char *Kerning__doc__ = R"""(
 )""";
 
 P11X_DECLARE_ENUM(
-    "Kerning", "Enum",
+    "Kerning", "Enum", FT_Kerning_Mode,
     {"DEFAULT", FT_KERNING_DEFAULT},
     {"UNFITTED", FT_KERNING_UNFITTED},
     {"UNSCALED", FT_KERNING_UNSCALED},
@@ -76,7 +76,7 @@ enum class FaceFlags : FT_Long {
 };
 
 P11X_DECLARE_ENUM(
-    "FaceFlags", "Flag",
+    "FaceFlags", "Flag", FaceFlags,
     {"SCALABLE", FaceFlags::SCALABLE},
     {"FIXED_SIZES", FaceFlags::FIXED_SIZES},
     {"FIXED_WIDTH", FaceFlags::FIXED_WIDTH},
@@ -147,7 +147,7 @@ enum class LoadFlags : FT_Int32 {
 };
 
 P11X_DECLARE_ENUM(
-    "LoadFlags", "Flag",
+    "LoadFlags", "Flag", LoadFlags,
     {"DEFAULT", LoadFlags::DEFAULT},
     {"NO_SCALE", LoadFlags::NO_SCALE},
     {"NO_HINTING", LoadFlags::NO_HINTING},
@@ -197,7 +197,7 @@ enum class StyleFlags : FT_Long {
 };
 
 P11X_DECLARE_ENUM(
-    "StyleFlags", "Flag",
+    "StyleFlags", "Flag", StyleFlags,
     {"NORMAL", StyleFlags::NORMAL},
     {"ITALIC", StyleFlags::ITALIC},
     {"BOLD", StyleFlags::BOLD},