Generic Enum implementation

src/System.Private.CoreLib/src/System/Collections/Generic/ComparerHelpers.cs

@@ -50,7 +50,7 @@ internal static object CreateDefaultComparer(Type type)
             // The comparer for enums is specialized to avoid boxing.
             else if (type.IsEnum)
             {
-                result = TryCreateEnumComparer(runtimeType);
+                result = CreateInstanceForAnotherGenericParameter((RuntimeType)typeof(EnumComparer<DayOfWeek>), runtimeType);
             }
 
             return result ?? CreateInstanceForAnotherGenericParameter((RuntimeType)typeof(ObjectComparer<object>), runtimeType);
@@ -75,38 +75,6 @@ private static object TryCreateNullableComparer(RuntimeType nullableType)
             return null;
         }
 
-        /// <summary>
-        /// Creates the default <see cref="Comparer{T}"/> for an enum type.
-        /// </summary>
-        /// <param name="enumType">The enum type to create the default comparer for.</param>
-        private static object TryCreateEnumComparer(RuntimeType enumType)
-        {
-            Debug.Assert(enumType != null);
-            Debug.Assert(enumType.IsEnum);
-
-            // Explicitly call Enum.GetUnderlyingType here. Although GetTypeCode
-            // ends up doing this anyway, we end up avoiding an unnecessary P/Invoke
-            // and virtual method call.
-            TypeCode underlyingTypeCode = Type.GetTypeCode(Enum.GetUnderlyingType(enumType));
-
-            // Depending on the enum type, we need to special case the comparers so that we avoid boxing.
-            // Specialize differently for signed/unsigned types so we avoid problems with large numbers.
-            switch (underlyingTypeCode)
-            {
-                case TypeCode.SByte:
-                case TypeCode.Int16:
-                case TypeCode.Int32:
-                case TypeCode.Byte:
-                case TypeCode.UInt16:
-                case TypeCode.UInt32:
-                case TypeCode.Int64:
-                case TypeCode.UInt64:
-                    return RuntimeTypeHandle.CreateInstanceForAnotherGenericParameter((RuntimeType)typeof(EnumComparer<>), enumType);
-            }
-
-            return null;
-        }
-
         /// <summary>
         /// Creates the default <see cref="EqualityComparer{T}"/>.
         /// </summary>
@@ -143,7 +111,7 @@ internal static object CreateDefaultEqualityComparer(Type type)
             // The equality comparer for enums is specialized to avoid boxing.
             else if (type.IsEnum)
             {
-                result = TryCreateEnumEqualityComparer(runtimeType);
+                result = CreateInstanceForAnotherGenericParameter((RuntimeType)typeof(EnumEqualityComparer<DayOfWeek>), runtimeType);
             }
 
             return result ?? CreateInstanceForAnotherGenericParameter((RuntimeType)typeof(ObjectEqualityComparer<object>), runtimeType);
@@ -167,36 +135,5 @@ private static object TryCreateNullableEqualityComparer(RuntimeType nullableType
 
             return null;
         }
-
-        /// <summary>
-        /// Creates the default <see cref="EqualityComparer{T}"/> for an enum type.
-        /// </summary>
-        /// <param name="enumType">The enum type to create the default equality comparer for.</param>
-        private static object TryCreateEnumEqualityComparer(RuntimeType enumType)
-        {
-            Debug.Assert(enumType != null);
-            Debug.Assert(enumType.IsEnum);
-
-            // See the METHOD__JIT_HELPERS__UNSAFE_ENUM_CAST and METHOD__JIT_HELPERS__UNSAFE_ENUM_CAST_LONG cases in getILIntrinsicImplementation
-            // for how we cast the enum types to integral values in the comparer without boxing.
-
-            TypeCode underlyingTypeCode = Type.GetTypeCode(Enum.GetUnderlyingType(enumType));
-
-            // Depending on the enum type, we need to special case the comparers so that we avoid boxing.
-            switch (underlyingTypeCode)
-            {
-                case TypeCode.Int32:
-                case TypeCode.UInt32:
-                case TypeCode.SByte:
-                case TypeCode.Byte:
-                case TypeCode.Int16:
-                case TypeCode.Int64:
-                case TypeCode.UInt64:
-                case TypeCode.UInt16:
-                    return RuntimeTypeHandle.CreateInstanceForAnotherGenericParameter((RuntimeType)typeof(EnumEqualityComparer<>), enumType);
-            }
-
-            return null;
-        }
     }
 }