Fix calling default constructor by uniform init. (AcademySoftwareFoun…

…dation#340)

I fixed calling default constructor in ImathTypeTraits.h by using
uniform initialization.

Signed-off-by: Yuya Asano <64895419+sukeya@users.noreply.github.com>

src/Imath/ImathTypeTraits.h

@@ -85,8 +85,8 @@ template <typename T, typename Base> struct has_xy
     // Valid only if .x, .y exist and are the right type: return a Yes.
     template <
         typename C,
-        IMATH_ENABLE_IF (std::is_same<decltype (C ().x), Base>::value),
-        IMATH_ENABLE_IF (std::is_same<decltype (C ().y), Base>::value)>
+        IMATH_ENABLE_IF (std::is_same<decltype (C {}.x), Base>::value),
+        IMATH_ENABLE_IF (std::is_same<decltype (C {}.y), Base>::value)>
     static Yes& test (int);
 
     // Fallback, default to returning a No.
@@ -113,9 +113,9 @@ template <typename T, typename Base> struct has_xyz
     // Valid only if .x, .y, .z exist and are the right type: return a Yes.
     template <
         typename C,
-        IMATH_ENABLE_IF (std::is_same<decltype (C ().x), Base>::value),
-        IMATH_ENABLE_IF (std::is_same<decltype (C ().y), Base>::value),
-        IMATH_ENABLE_IF (std::is_same<decltype (C ().z), Base>::value)>
+        IMATH_ENABLE_IF (std::is_same<decltype (C {}.x), Base>::value),
+        IMATH_ENABLE_IF (std::is_same<decltype (C {}.y), Base>::value),
+        IMATH_ENABLE_IF (std::is_same<decltype (C {}.z), Base>::value)>
     static Yes& test (int);
 
     // Fallback, default to returning a No.
@@ -142,10 +142,10 @@ template <typename T, typename Base> struct has_xyzw
     // Valid only if .x, .y, .z, .w exist and are the right type: return a Yes.
     template <
         typename C,
-        IMATH_ENABLE_IF (std::is_same<decltype (C ().x), Base>::value),
-        IMATH_ENABLE_IF (std::is_same<decltype (C ().y), Base>::value),
-        IMATH_ENABLE_IF (std::is_same<decltype (C ().z), Base>::value),
-        IMATH_ENABLE_IF (std::is_same<decltype (C ().w), Base>::value)>
+        IMATH_ENABLE_IF (std::is_same<decltype (C {}.x), Base>::value),
+        IMATH_ENABLE_IF (std::is_same<decltype (C {}.y), Base>::value),
+        IMATH_ENABLE_IF (std::is_same<decltype (C {}.z), Base>::value),
+        IMATH_ENABLE_IF (std::is_same<decltype (C {}.w), Base>::value)>
     static Yes& test (int);
 
     // Fallback, default to returning a No.
@@ -173,7 +173,7 @@ template <typename T, typename Base, int Nelem> struct has_subscript
     template <
         typename C,
         IMATH_ENABLE_IF (std::is_same<
-                         typename std::decay<decltype (C ()[0])>::type,
+                         typename std::decay<decltype (C {}[0])>::type,
                          Base>::value)>
     static Yes& test (int);
 
@@ -208,7 +208,7 @@ struct has_double_subscript
     template <
         typename C,
         IMATH_ENABLE_IF (std::is_same<
-                         typename std::decay<decltype (C ()[0][0])>::type,
+                         typename std::decay<decltype (C {}[0][0])>::type,
                          Base>::value)>
     static Yes& test (int);