First commit for private source control. Older commits available on Github.

Assets/Plugins/SerializedCollections/Editor/Scripts/Utility/SCEnumUtility.cs

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+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Linq;
+using System.Reflection;
+using UnityEditor;
+using UnityEngine;
+
+namespace AYellowpaper.SerializedCollections.Editor
+{
+    internal static class SCEnumUtility
+    {
+        private static Dictionary<Type, EnumCache> _cache = new Dictionary<Type, EnumCache>();
+
+        internal static EnumCache GetEnumCache(Type enumType)
+        {
+            if (_cache.TryGetValue(enumType, out var val))
+                return val;
+
+            try
+            {
+                var classType = typeof(EditorGUI).Assembly.GetType("UnityEditor.EnumDataUtility");
+                var methodInfo = classType.GetMethod("GetCachedEnumData", BindingFlags.Static | BindingFlags.NonPublic);
+                var parameters = new object[] { enumType, true };
+                var result = methodInfo.Invoke(null, parameters);
+                var flagValues = (int[])result.GetType().GetField("flagValues").GetValue(result);
+                var names = (string[])result.GetType().GetField("names").GetValue(result);
+                var cache = new EnumCache(enumType, flagValues, names);
+                _cache.Add(enumType, cache);
+                return cache;
+            }
+            catch
+            {
+                throw;
+            }
+        }
+    }
+
+    internal record EnumCache
+    {
+        public readonly Type Type;
+        public readonly bool IsFlag;
+        public readonly int Length;
+        public readonly int[] FlagValues;
+        public readonly string[] Names;
+
+        private readonly Dictionary<int, string[]> _namesByValue = new Dictionary<int, string[]>();
+
+        public EnumCache(Type type, int[] flagValues, string[] displayNames)
+        {
+            Type = type;
+            FlagValues = flagValues;
+            Names = displayNames;
+            Length = flagValues.Length;
+            IsFlag = Type.IsDefined(typeof(FlagsAttribute));
+        }
+
+        internal string[] GetNamesForValue(int value)
+        {
+            if (_namesByValue.TryGetValue(value, out var list))
+                return list;
+
+            string[] array = IsFlag ? GetFlagValues(value).ToArray() : new[] { GetEnumValue(value) };
+
+            _namesByValue.Add(value, array);
+            return array;
+        }
+
+        private string GetEnumValue(int value)
+        {
+            for (int i = 0; i < Length; i++)
+            {
+                if (FlagValues[i] == value)
+                    return Names[i];
+            }
+            return null;
+        }
+
+        private IEnumerable<string> GetFlagValues(int flagValue)
+        {
+            if (flagValue == 0)
+            {
+                yield return FlagValues[0] == 0 ? Names[0] : "Nothing";
+                yield break;
+            }
+
+            for (int i = 0; i < Length; i++)
+            {
+                int fv = FlagValues[i];
+                if ((fv & flagValue) == fv && fv != 0)
+                    yield return Names[i];
+            }
+
+            if (FlagValues[Length - 1] != -1 && flagValue == -1)
+                yield return "Everything";
+        }
+    }
+}