CommonFuncs: Replace ArraySize define with constexpr equivalent

Source/Core/Common/CommonFuncs.h

@@ -17,16 +17,14 @@
 
 #include <cstddef>
 #include <string>
-#include <type_traits>
 #include "Common/CommonTypes.h"
 
 // Will fail to compile on a non-array:
-// TODO: make this a function when constexpr is available
-template <typename T>
-struct ArraySizeImpl : public std::extent<T>
-{ static_assert(std::is_array<T>::value, "is array"); };
-
-#define ArraySize(x) ArraySizeImpl<decltype(x)>::value
+template <typename T, size_t N>
+constexpr size_t ArraySize(T (&arr)[N])
+{
+	return N;
+}
 
 #define b2(x)   (   (x) | (   (x) >> 1) )
 #define b4(x)   ( b2(x) | ( b2(x) >> 2) )

Source/Core/Core/HW/EXI_DeviceMemoryCard.cpp

@@ -132,7 +132,7 @@ CEXIMemoryCard::CEXIMemoryCard(const int index, bool gciFolder)
 
 	memory_card_size = memorycard->GetCardId() * SIZE_TO_Mb;
 	u8 header[20] = {0};
-	memorycard->Read(0, ArraySize(header), header);
+	memorycard->Read(0, static_cast<s32>(ArraySize(header)), header);
 	SetCardFlashID(header, card_index);
 }
 

Source/UnitTests/Common/CommonFuncsTest.cpp

@@ -6,7 +6,7 @@
 
 #include "Common/CommonFuncs.h"
 
-TEST(CommonFuncs, ArraySizeMacro)
+TEST(CommonFuncs, ArraySizeFunction)
 {
 	char test[4];
 	u32 test2[42];