Revert "Rewrite Enum and add {ISpanFormattable}.TryFormat (#78580)"

This reverts commit 62f3eb2.

src/coreclr/System.Private.CoreLib/src/System/Enum.CoreCLR.cs

@@ -2,7 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System.Diagnostics;
-using System.Numerics;
+using System.Diagnostics.CodeAnalysis;
 using System.Reflection;
 using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
@@ -20,15 +20,6 @@ public abstract partial class Enum
         [MethodImpl(MethodImplOptions.InternalCall)]
         private static extern unsafe CorElementType InternalGetCorElementType(MethodTable* pMT);
 
-        [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        private static unsafe CorElementType InternalGetCorElementType(RuntimeType rt)
-        {
-            Debug.Assert(rt.IsActualEnum);
-            CorElementType elementType = InternalGetCorElementType((MethodTable*)rt.GetUnderlyingNativeHandle());
-            GC.KeepAlive(rt);
-            return elementType;
-        }
-
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         private unsafe CorElementType InternalGetCorElementType()
         {
@@ -82,31 +73,26 @@ internal static unsafe RuntimeType InternalGetUnderlyingType(RuntimeType enumTyp
         }
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        private static EnumInfo<TUnderlyingValue> GetEnumInfo<TUnderlyingValue>(RuntimeType enumType, bool getNames = true)
-            where TUnderlyingValue : struct, INumber<TUnderlyingValue>
+        private static EnumInfo GetEnumInfo(RuntimeType enumType, bool getNames = true)
         {
-            return enumType.GenericCache is EnumInfo<TUnderlyingValue> info && (!getNames || info.Names is not null) ?
+            return enumType.GenericCache is EnumInfo info && (!getNames || info.Names is not null) ?
                 info :
                 InitializeEnumInfo(enumType, getNames);
 
             [MethodImpl(MethodImplOptions.NoInlining)]
-            static EnumInfo<TUnderlyingValue> InitializeEnumInfo(RuntimeType enumType, bool getNames)
+            static EnumInfo InitializeEnumInfo(RuntimeType enumType, bool getNames)
             {
-                TUnderlyingValue[]? values = null;
+                ulong[]? values = null;
                 string[]? names = null;
-
+                RuntimeTypeHandle enumTypeHandle = enumType.TypeHandle;
                 GetEnumValuesAndNames(
-                    new QCallTypeHandle(ref enumType),
+                    new QCallTypeHandle(ref enumTypeHandle),
                     ObjectHandleOnStack.Create(ref values),
                     ObjectHandleOnStack.Create(ref names),
                     getNames ? Interop.BOOL.TRUE : Interop.BOOL.FALSE);
-
-                Debug.Assert(values!.GetType() == typeof(TUnderlyingValue[]));
-                Debug.Assert(!getNames || names!.GetType() == typeof(string[]));
-
                 bool hasFlagsAttribute = enumType.IsDefined(typeof(FlagsAttribute), inherit: false);
 
-                var entry = new EnumInfo<TUnderlyingValue>(hasFlagsAttribute, values, names!);
+                var entry = new EnumInfo(hasFlagsAttribute, values!, names!);
                 enumType.GenericCache = entry;
                 return entry;
             }

src/coreclr/nativeaot/System.Private.CoreLib/src/CompatibilitySuppressions.xml

@@ -824,10 +824,6 @@
     <DiagnosticId>CP0001</DiagnosticId>
     <Target>T:System.Reflection.EnumInfo</Target>
   </Suppression>
-  <Suppression>
-    <DiagnosticId>CP0001</DiagnosticId>
-    <Target>T:System.Reflection.EnumInfo`1</Target>
-  </Suppression>
   <Suppression>
     <DiagnosticId>CP0001</DiagnosticId>
     <Target>T:System.Reflection.Runtime.General.MetadataReaderExtensions</Target>
@@ -976,4 +972,4 @@
     <DiagnosticId>CP0016</DiagnosticId>
     <Target>M:System.Runtime.InteropServices.Marshal.GetObjectForNativeVariant``1(System.IntPtr)-&gt;T?:[T:System.Diagnostics.CodeAnalysis.MaybeNullAttribute]</Target>
   </Suppression>
-</Suppressions>
+</Suppressions>

src/coreclr/nativeaot/System.Private.CoreLib/src/Internal/Reflection/Augments/ReflectionAugments.cs

@@ -21,7 +21,6 @@
 using System.Diagnostics;
 using System.Diagnostics.CodeAnalysis;
 using System.Globalization;
-using System.Numerics;
 
 using EETypeElementType = Internal.Runtime.EETypeElementType;
 
@@ -165,8 +164,7 @@ public abstract object ActivatorCreateInstance(
 
         public abstract Assembly[] GetLoadedAssemblies();
 
-        public abstract EnumInfo<TUnderlyingValue> GetEnumInfo<TUnderlyingValue>(Type type)
-            where TUnderlyingValue : struct, INumber<TUnderlyingValue>;
+        public abstract EnumInfo GetEnumInfo(Type type);
 
         public abstract DynamicInvokeInfo GetDelegateDynamicInvokeInfo(Type type);
     }

src/coreclr/nativeaot/System.Private.CoreLib/src/Internal/Reflection/Core/Execution/ExecutionEnvironment.cs

@@ -6,7 +6,6 @@
 using System.Reflection;
 using System.Collections.Generic;
 using System.Diagnostics.CodeAnalysis;
-using System.Numerics;
 using System.Reflection.Runtime.General;
 using System.Reflection.Runtime.TypeInfos;
 using System.Runtime.CompilerServices;
@@ -98,9 +97,7 @@ public abstract class ExecutionEnvironment
         // Other
         //==============================================================================================
         public abstract FieldAccessor CreateLiteralFieldAccessor(object value, RuntimeTypeHandle fieldTypeHandle);
-        public abstract EnumInfo<TUnderlyingValue> GetEnumInfo<TUnderlyingValue>(RuntimeTypeHandle typeHandle)
-            where TUnderlyingValue : struct, INumber<TUnderlyingValue>;
-
+        public abstract EnumInfo GetEnumInfo(RuntimeTypeHandle typeHandle);
         public abstract IntPtr GetDynamicInvokeThunk(MethodInvoker invoker);
 
         //==============================================================================================

src/coreclr/nativeaot/System.Private.CoreLib/src/System/Enum.NativeAot.cs

@@ -3,11 +3,9 @@
 
 using System.Diagnostics;
 using System.Diagnostics.CodeAnalysis;
-using System.Numerics;
 using System.Reflection;
 using System.Runtime;
 using System.Runtime.CompilerServices;
-using Internal.Runtime.Augments;
 using Internal.Runtime.CompilerServices;
 using Internal.Reflection.Augments;
 
@@ -25,29 +23,7 @@ internal static EnumInfo GetEnumInfo(Type enumType, bool getNames = true)
             Debug.Assert(enumType is RuntimeType);
             Debug.Assert(enumType.IsEnum);
 
-            RuntimeType rt = (RuntimeType)enumType;
-            return Type.GetTypeCode(RuntimeAugments.GetEnumUnderlyingType(rt.TypeHandle)) switch
-            {
-                TypeCode.SByte => GetEnumInfo<sbyte>(rt),
-                TypeCode.Byte => GetEnumInfo<byte>(rt),
-                TypeCode.Int16 => GetEnumInfo<short>(rt),
-                TypeCode.UInt16 => GetEnumInfo<ushort>(rt),
-                TypeCode.Int32 => GetEnumInfo<int>(rt),
-                TypeCode.UInt32 => GetEnumInfo<uint>(rt),
-                TypeCode.Int64 => GetEnumInfo<long>(rt),
-                TypeCode.UInt64 => GetEnumInfo<ulong>(rt),
-                _ => throw new NotSupportedException(),
-            };
-        }
-
-        internal static EnumInfo<TUnderlyingValue> GetEnumInfo<TUnderlyingValue>(Type enumType, bool getNames = true)
-            where TUnderlyingValue : struct, INumber<TUnderlyingValue>
-        {
-            Debug.Assert(enumType != null);
-            Debug.Assert(enumType is RuntimeType);
-            Debug.Assert(enumType.IsEnum);
-
-            return ReflectionAugments.ReflectionCoreCallbacks.GetEnumInfo<TUnderlyingValue>(enumType);
+            return ReflectionAugments.ReflectionCoreCallbacks.GetEnumInfo(enumType);
         }
 #pragma warning restore
 
@@ -56,12 +32,6 @@ private static object InternalBoxEnum(Type enumType, long value)
             return ToObject(enumType.TypeHandle.ToEETypePtr(), value);
         }
 
-        private static CorElementType InternalGetCorElementType(RuntimeType rt)
-        {
-            Debug.Assert(rt.IsActualEnum);
-            return rt.TypeHandle.ToEETypePtr().CorElementType;
-        }
-
         private CorElementType InternalGetCorElementType()
         {
             return this.GetEETypePtr().CorElementType;
@@ -145,6 +115,14 @@ internal static Type InternalGetUnderlyingType(RuntimeType enumType)
             return GetEnumInfo(enumType).UnderlyingType;
         }
 
+        public static TEnum[] GetValues<TEnum>() where TEnum : struct, Enum
+        {
+            Array values = GetEnumInfo(typeof(TEnum)).ValuesAsUnderlyingType;
+            TEnum[] result = new TEnum[values.Length];
+            Array.Copy(values, result, values.Length);
+            return result;
+        }
+
         //
         // Checks if value.GetType() matches enumType exactly.
         //

src/coreclr/nativeaot/System.Private.CoreLib/src/System/Reflection/EnumInfo.cs

@@ -4,46 +4,84 @@
 using System;
 using System.Collections.Generic;
 using System.Diagnostics;
-using System.Numerics;
 using System.Runtime;
 using System.Runtime.CompilerServices;
 
 namespace System.Reflection
 {
     [ReflectionBlocked]
-    public abstract class EnumInfo
+    public sealed class EnumInfo
     {
-        private protected EnumInfo(Type underlyingType, string[] names, bool isFlags)
+        public EnumInfo(Type underlyingType, object[] rawValues, string[] names, bool isFlags)
         {
+            Debug.Assert(rawValues.Length == names.Length);
+
             UnderlyingType = underlyingType;
-            Names = names;
-            HasFlagsAttribute = isFlags;
-        }
 
-        internal Type UnderlyingType { get; }
-        internal string[] Names { get; }
-        internal bool HasFlagsAttribute { get; }
-    }
+            int numValues = rawValues.Length;
+            ulong[] values = new ulong[numValues];
+            for (int i = 0; i < numValues; i++)
+            {
+                object rawValue = rawValues[i];
 
-    [ReflectionBlocked]
-    public sealed class EnumInfo<TUnderlyingValue> : EnumInfo
-        where TUnderlyingValue : struct, INumber<TUnderlyingValue>
-    {
-        public EnumInfo(Type underlyingType, TUnderlyingValue[] values, string[] names, bool isFlags) :
-            base(underlyingType, names, isFlags)
-        {
-            Debug.Assert(values.Length == names.Length);
+                ulong rawUnboxedValue;
+                if (rawValue is ulong)
+                {
+                    rawUnboxedValue = (ulong)rawValue;
+                }
+                else
+                {
+                    // This conversion is this way for compatibility: do a value-preseving cast to long - then store (and compare) as ulong. This affects
+                    // the order in which the Enum apis return names and values.
+                    rawUnboxedValue = (ulong)(((IConvertible)rawValue).ToInt64(null));
+                }
+                values[i] = rawUnboxedValue;
+            }
 
-            Array.Sort(keys: values, items: names);
+            // Need to sort the `names` and `rawValues` arrays according to the `values` array
+            ulong[] valuesCopy = (ulong[])values.Clone();
+            Array.Sort(keys: valuesCopy, items: rawValues, comparer: Comparer<ulong>.Default);
+            Array.Sort(keys: values, items: names, comparer: Comparer<ulong>.Default);
 
+            Names = names;
             Values = values;
-            ValuesAreSequentialFromZero = Enum.AreSequentialFromZero(values);
+
+            // Create the unboxed version of values for the Values property to return. (We didn't do this earlier because
+            // declaring "rawValues" as "Array" would prevent us from using the generic overload of Array.Sort()).
+            //
+            // The array element type is the underlying type, not the enum type. (The enum type could be an open generic.)
+            ValuesAsUnderlyingType = Type.GetTypeCode(UnderlyingType) switch
+            {
+                TypeCode.Byte => new byte[numValues],
+                TypeCode.SByte => new sbyte[numValues],
+                TypeCode.UInt16 => new ushort[numValues],
+                TypeCode.Int16 => new short[numValues],
+                TypeCode.UInt32 => new uint[numValues],
+                TypeCode.Int32 => new int[numValues],
+                TypeCode.UInt64 => new ulong[numValues],
+                TypeCode.Int64 => new long[numValues],
+                _ => throw new NotSupportedException(),
+            };
+            Array.Copy(rawValues, ValuesAsUnderlyingType, numValues);
+
+            HasFlagsAttribute = isFlags;
+
+            ValuesAreSequentialFromZero = true;
+            for (int i = 0; i < values.Length; i++)
+            {
+                if (values[i] != (ulong)i)
+                {
+                    ValuesAreSequentialFromZero = false;
+                    break;
+                }
+            }
         }
 
-        internal TUnderlyingValue[] Values { get; }
+        internal Type UnderlyingType { get; }
+        internal string[] Names { get; }
+        internal ulong[] Values { get; }
+        internal Array ValuesAsUnderlyingType { get; }
+        internal bool HasFlagsAttribute { get; }
         internal bool ValuesAreSequentialFromZero { get; }
-
-        public TUnderlyingValue[] CloneValues() =>
-            new ReadOnlySpan<TUnderlyingValue>(Values).ToArray();
     }
 }

src/coreclr/nativeaot/System.Private.CoreLib/src/System/Reflection/Runtime/General/ReflectionCoreCallbacksImplementation.cs

@@ -404,15 +404,15 @@ public sealed override void MakeTypedReference(object target, FieldInfo[] flds,
 
         public sealed override Assembly[] GetLoadedAssemblies() => RuntimeAssemblyInfo.GetLoadedAssemblies();
 
-        public sealed override EnumInfo<TUnderlyingValue> GetEnumInfo<TUnderlyingValue>(Type type)
+        public sealed override EnumInfo GetEnumInfo(Type type)
         {
             RuntimeTypeInfo runtimeType = type.CastToRuntimeTypeInfo();
 
-            EnumInfo<TUnderlyingValue>? info = runtimeType.GenericCache as EnumInfo<TUnderlyingValue>;
+            EnumInfo? info = runtimeType.GenericCache as EnumInfo;
             if (info != null)
                 return info;
 
-            info = ReflectionCoreExecution.ExecutionDomain.ExecutionEnvironment.GetEnumInfo<TUnderlyingValue>(runtimeType.TypeHandle);
+            info = ReflectionCoreExecution.ExecutionDomain.ExecutionEnvironment.GetEnumInfo(runtimeType.TypeHandle);
             runtimeType.GenericCache = info;
             return info;
         }

src/coreclr/nativeaot/System.Private.CoreLib/src/System/RuntimeType.cs

@@ -22,17 +22,17 @@ public abstract class RuntimeType : TypeInfo
             // Do a value-preserving cast of both it and the enum values and do a 64-bit compare.
 
             if (!IsActualEnum)
-                throw new ArgumentException(SR.Arg_MustBeEnum, "enumType");
+                throw new ArgumentException(SR.Arg_MustBeEnum);
 
-            return Enum.GetName(this, rawValue);
+            return Enum.GetEnumName(this, rawValue);
         }
 
         public sealed override string[] GetEnumNames()
         {
             if (!IsActualEnum)
                 throw new ArgumentException(SR.Arg_MustBeEnum, "enumType");
 
-            string[] ret = Enum.GetNamesNoCopy(this);
+            string[] ret = Enum.InternalGetNames(this);
 
             // Make a copy since we can't hand out the same array since users can modify them
             return new ReadOnlySpan<string>(ret).ToArray();
@@ -87,7 +87,7 @@ public sealed override bool IsEnumDefined(object value)
                         throw new ArgumentException(SR.Format(SR.Arg_EnumUnderlyingTypeAndObjectMustBeSameType, value.GetType(), underlyingType));
                 }
 
-                return Enum.GetName(this, rawValue) != null;
+                return Enum.GetEnumName(this, rawValue) != null;
             }
         }
 
@@ -97,16 +97,16 @@ public sealed override Array GetEnumValues()
             if (!IsActualEnum)
                 throw new ArgumentException(SR.Arg_MustBeEnum, "enumType");
 
-            Array values = Enum.GetValuesAsUnderlyingTypeNoCopy(this);
+            Array values = Enum.GetEnumInfo(this).ValuesAsUnderlyingType;
             int count = values.Length;
-
             // Without universal shared generics, chances are slim that we'll have the appropriate
             // array type available. Offer an escape hatch that avoids a missing metadata exception
             // at the cost of a small appcompat risk.
-            Array result = AppContext.TryGetSwitch("Switch.System.Enum.RelaxedGetValues", out bool isRelaxed) && isRelaxed ?
-                Array.CreateInstance(Enum.InternalGetUnderlyingType(this), count) :
-                Array.CreateInstance(this, count);
-
+            Array result;
+            if (AppContext.TryGetSwitch("Switch.System.Enum.RelaxedGetValues", out bool isRelaxed) && isRelaxed)
+                result = Array.CreateInstance(Enum.InternalGetUnderlyingType(this), count);
+            else
+                result = Array.CreateInstance(this, count);
             Array.Copy(values, result, values.Length);
             return result;
         }
@@ -116,7 +116,7 @@ public sealed override Array GetEnumValuesAsUnderlyingType()
             if (!IsActualEnum)
                 throw new ArgumentException(SR.Arg_MustBeEnum, "enumType");
 
-            return (Array)Enum.GetValuesAsUnderlyingTypeNoCopy(this).Clone();
+            return (Array)Enum.GetEnumInfo(this).ValuesAsUnderlyingType.Clone();
         }
 
         internal bool IsActualEnum

src/coreclr/nativeaot/System.Private.DisabledReflection/src/Internal/Reflection/ReflectionCoreCallbacksImplementation.cs

@@ -12,12 +12,14 @@ namespace Internal.Reflection
 {
     internal class ReflectionCoreCallbacksImplementation : ReflectionCoreCallbacks
     {
-        public override EnumInfo<TUnderlyingValue> GetEnumInfo<TUnderlyingValue>(Type type) =>
-            new EnumInfo<TUnderlyingValue>(
+        public override EnumInfo GetEnumInfo(Type type)
+        {
+            return new EnumInfo(
                 RuntimeAugments.GetEnumUnderlyingType(type.TypeHandle),
-                values: Array.Empty<TUnderlyingValue>(),
+                rawValues: Array.Empty<object>(),
                 names: Array.Empty<string>(),
                 isFlags: false);
+        }
 
         public override DynamicInvokeInfo GetDelegateDynamicInvokeInfo(Type type)
             => throw new NotSupportedException(SR.Reflection_Disabled);