From c70d22c85bf86dc2eaa118dd8b98606267eecaef Mon Sep 17 00:00:00 2001
From: _Redstone_c_ <myredstone1024@gmail.com>
Date: Thu, 3 Feb 2022 21:18:19 +0800
Subject: [PATCH] fix(typetraits): fix compile errors caused by TCommonType and
 TCommonReference when there is no matching type

---
 .../Private/Testing/TypeTraitsTesting.cpp     | 18 +++++++-----
 .../Source/Public/TypeTraits/Common.h         | 29 +++++++++++++++++++
 .../Source/Public/TypeTraits/Miscellaneous.h  |  2 --
 .../Source/Public/TypeTraits/TypeTraits.h     |  1 +
 4 files changed, 40 insertions(+), 10 deletions(-)
 create mode 100644 Redcraft.Utility/Source/Public/TypeTraits/Common.h

diff --git a/Redcraft.Utility/Source/Private/Testing/TypeTraitsTesting.cpp b/Redcraft.Utility/Source/Private/Testing/TypeTraitsTesting.cpp
index 30c846a..5cd928b 100644
--- a/Redcraft.Utility/Source/Private/Testing/TypeTraitsTesting.cpp
+++ b/Redcraft.Utility/Source/Private/Testing/TypeTraitsTesting.cpp
@@ -413,14 +413,6 @@ void TestTypeTraits()
 	always_check((TIsSame<int32, TConditional<true, int32, int64>::Type>::Value));
 	always_check((TIsSame<int64, TConditional<false, int32, int64>::Type>::Value));
 
-	always_check((TIsSame<int32, TCommonType<int8, int32>::Type>::Value));
-	always_check((TIsSame<int64, TCommonType<int8, int32, int64>::Type>::Value));
-	always_check((TIsSame<double, TCommonType<float, double>::Type>::Value));
-
-	always_check((TIsSame<int32, TCommonReference<int8, int32>::Type>::Value));
-	always_check((TIsSame<int64, TCommonReference<int8, int32, int64>::Type>::Value));
-	always_check((TIsSame<double, TCommonReference<float, double>::Type>::Value));
-
 	always_check((TIsSame<int, TUnderlyingType<ETestEnumClass>::Type>::Value));
 	always_check((TIsSame<uint8, TUnderlyingType<ETestEnumClass8>::Type>::Value));
 	always_check((TIsSame<uint32, TUnderlyingType<ETestEnumClass32>::Type>::Value));
@@ -433,6 +425,16 @@ void TestTypeTraits()
 	always_check((TIsSame<void, TVoid<int32>::Type>::Value));
 	always_check((TIsSame<void, TVoid<int32, int64>::Type>::Value));
 
+	// Common.h
+
+	always_check((TIsSame<int32, TCommonType<int8, int32>::Type>::Value));
+	always_check((TIsSame<int64, TCommonType<int8, int32, int64>::Type>::Value));
+	always_check((TIsSame<double, TCommonType<float, double>::Type>::Value));
+
+	always_check((TIsSame<int32, TCommonReference<int8, int32>::Type>::Value));
+	always_check((TIsSame<int64, TCommonReference<int8, int32, int64>::Type>::Value));
+	always_check((TIsSame<double, TCommonReference<float, double>::Type>::Value));
+
 }
 
 NAMESPACE_MODULE_END(Utility)
diff --git a/Redcraft.Utility/Source/Public/TypeTraits/Common.h b/Redcraft.Utility/Source/Public/TypeTraits/Common.h
new file mode 100644
index 0000000..80778a6
--- /dev/null
+++ b/Redcraft.Utility/Source/Public/TypeTraits/Common.h
@@ -0,0 +1,29 @@
+#pragma once
+
+#include "CoreTypes.h"
+#include "TypeTraits/HelperClasses.h"
+
+#include <type_traits>
+
+NAMESPACE_REDCRAFT_BEGIN
+NAMESPACE_MODULE_BEGIN(Redcraft)
+NAMESPACE_MODULE_BEGIN(Utility)
+
+NAMESPACE_PRIVATE_BEGIN
+
+struct FNoopStruct { };
+
+template <typename... Types> concept CCommonType      = requires { typename NAMESPACE_STD::common_type_t<Types...>;      };
+template <typename... Types> concept CCommonReference = requires { typename NAMESPACE_STD::common_reference_t<Types...>; };
+
+template <typename... Types> struct TCommonType      { using Type = NAMESPACE_STD::common_type_t<Types...>;      };
+template <typename... Types> struct TCommonReference { using Type = NAMESPACE_STD::common_reference_t<Types...>; };
+
+NAMESPACE_PRIVATE_END
+
+template <typename... Types> struct TCommonType      : TConditional<NAMESPACE_PRIVATE::CCommonType<Types...>,      NAMESPACE_PRIVATE::TCommonType<Types...>,      NAMESPACE_PRIVATE::FNoopStruct>::Type { };
+template <typename... Types> struct TCommonReference : TConditional<NAMESPACE_PRIVATE::CCommonReference<Types...>, NAMESPACE_PRIVATE::TCommonReference<Types...>, NAMESPACE_PRIVATE::FNoopStruct>::Type { };
+
+NAMESPACE_MODULE_END(Utility)
+NAMESPACE_MODULE_END(Redcraft)
+NAMESPACE_REDCRAFT_END
diff --git a/Redcraft.Utility/Source/Public/TypeTraits/Miscellaneous.h b/Redcraft.Utility/Source/Public/TypeTraits/Miscellaneous.h
index a51a471..32b64b8 100644
--- a/Redcraft.Utility/Source/Public/TypeTraits/Miscellaneous.h
+++ b/Redcraft.Utility/Source/Public/TypeTraits/Miscellaneous.h
@@ -50,8 +50,6 @@ template <size_t Size, typename... Types> struct TAlignedUnion    { using Type =
 template <typename T>                     struct TDecay           { using Type = NAMESPACE_STD::decay_t<T>;                      };
 template <bool B, typename T = void>      struct TEnableIf        { using Type = NAMESPACE_STD::enable_if_t<B, T>;               };
 template <bool B, typename T, typename F> struct TConditional     { using Type = NAMESPACE_STD::conditional_t<B, T, F>;          };
-template <typename... Types>              struct TCommonType      { using Type = NAMESPACE_STD::common_type_t<Types...>;         };
-template <typename... Types>              struct TCommonReference { using Type = NAMESPACE_STD::common_reference_t<Types...>;    };
 template <typename T>                     struct TUnderlyingType  { using Type = NAMESPACE_STD::underlying_type_t<T>;            };
 template <typename F, typename... Args>   struct TInvokeResult    { using Type = NAMESPACE_STD::invoke_result_t<F, Args...>;     }; // FIXME: The result for char(&())[2] is wrong on MSVC
 template <typename... Types>              struct TVoid            { using Type = void;                                           };
diff --git a/Redcraft.Utility/Source/Public/TypeTraits/TypeTraits.h b/Redcraft.Utility/Source/Public/TypeTraits/TypeTraits.h
index c925295..7831cde 100644
--- a/Redcraft.Utility/Source/Public/TypeTraits/TypeTraits.h
+++ b/Redcraft.Utility/Source/Public/TypeTraits/TypeTraits.h
@@ -7,3 +7,4 @@
 #include "TypeTraits/TypeProperties.h"
 #include "TypeTraits/SupportedOperations.h"
 #include "TypeTraits/Miscellaneous.h"
+#include "TypeTraits/Common.h"