Fix #1111: Only hide "enum value initializers" when all of them can be hidden or only the first needs to be specified.

ICSharpCode.Decompiler.Tests/TestCases/Pretty/CompoundAssignmentTest.cs

@@ -34,9 +34,9 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty
 
 		public enum ShortEnum : short
 		{
-			None,
-			One,
-			Two,
+			None = 0,
+			One = 1,
+			Two = 2,
 			Four = 4
 		}
 

ICSharpCode.Decompiler/CSharp/CSharpDecompiler.cs

@@ -1031,9 +1031,56 @@ namespace ICSharpCode.Decompiler.CSharp
 					}
 				}
 			}
+			if (typeDecl.ClassType == ClassType.Enum) {
+				switch (DetectBestEnumValueDisplayMode(typeDef)) {
+					case EnumValueDisplayMode.FirstOnly:
+						foreach (var enumMember in typeDecl.Members.OfType<EnumMemberDeclaration>().Skip(1)) {
+							enumMember.Initializer = null;
+						}
+						break;
+					case EnumValueDisplayMode.None:
+						foreach (var enumMember in typeDecl.Members.OfType<EnumMemberDeclaration>()) {
+							enumMember.Initializer = null;
+						}
+						break;
+					case EnumValueDisplayMode.All:
+						// nothing needs to be changed.
+						break;
+					default:
+						throw new ArgumentOutOfRangeException();
+				}
+			}
 			return typeDecl;
 		}
 
+		enum EnumValueDisplayMode
+		{
+			None,
+			All,
+			FirstOnly
+		}
+
+		EnumValueDisplayMode DetectBestEnumValueDisplayMode(ITypeDefinition typeDef)
+		{
+			if (typeDef.GetAttribute(new TopLevelTypeName("System", "FlagsAttribute")) != null)
+				return EnumValueDisplayMode.All;
+			bool first = true;
+			long firstValue = 0, previousValue = 0;
+			foreach (var field in typeDef.Fields) {
+				var fieldDef = typeSystem.GetCecil(field) as FieldDefinition;
+				if (!(fieldDef != null && !MemberIsHidden(fieldDef, settings))) continue;
+				long currentValue = (long)CSharpPrimitiveCast.Cast(TypeCode.Int64, field.ConstantValue, false);
+				if (first) {
+					firstValue = currentValue;
+					first = false;
+				} else if (previousValue + 1 != currentValue) {
+					return EnumValueDisplayMode.All;
+				}
+				previousValue = currentValue;
+			}
+			return firstValue == 0 ? EnumValueDisplayMode.None : EnumValueDisplayMode.FirstOnly;
+		}
+
 		static readonly Syntax.Attribute obsoleteAttributePattern = new Syntax.Attribute() {
 			Type = new TypePattern(typeof(ObsoleteAttribute)),
 			Arguments = {
@@ -1217,26 +1264,17 @@ namespace ICSharpCode.Decompiler.CSharp
 			Debug.Assert(decompilationContext.CurrentMember == field);
 			var typeSystemAstBuilder = CreateAstBuilder(decompilationContext);
 			if (decompilationContext.CurrentTypeDefinition.Kind == TypeKind.Enum && field.ConstantValue != null) {
-				var index = decompilationContext.CurrentTypeDefinition.Members.IndexOf(field);
-				long previousValue = -1;
-				if (index > 0) {
-					var previousMember = (IField)decompilationContext.CurrentTypeDefinition.Members[index - 1];
-					previousValue = (long)CSharpPrimitiveCast.Cast(TypeCode.Int64, previousMember.ConstantValue, false);
-				}
 				var enumDec = new EnumMemberDeclaration { Name = field.Name };
 				long initValue = (long)CSharpPrimitiveCast.Cast(TypeCode.Int64, field.ConstantValue, false);
-				if (decompilationContext.CurrentTypeDefinition.Attributes.Any(a => a.AttributeType.FullName == "System.FlagsAttribute")) {
-					enumDec.Initializer = typeSystemAstBuilder.ConvertConstantValue(decompilationContext.CurrentTypeDefinition.EnumUnderlyingType, field.ConstantValue);
-					if (enumDec.Initializer is PrimitiveExpression primitive)
-						primitive.SetValue(initValue, $"0x{initValue:X}");
-				} else if (previousValue + 1 != initValue) {
-					enumDec.Initializer = typeSystemAstBuilder.ConvertConstantValue(decompilationContext.CurrentTypeDefinition.EnumUnderlyingType, field.ConstantValue);
-					if (enumDec.Initializer is PrimitiveExpression primitive && initValue > 9 && ((initValue & (initValue - 1)) == 0 || (initValue & (initValue + 1)) == 0)) {
-						primitive.SetValue(initValue, $"0x{initValue:X}");
-					}
+				enumDec.Initializer = typeSystemAstBuilder.ConvertConstantValue(decompilationContext.CurrentTypeDefinition.EnumUnderlyingType, field.ConstantValue);
+				if (enumDec.Initializer is PrimitiveExpression primitive
+					&& (decompilationContext.CurrentTypeDefinition.Attributes.Any(a => a.AttributeType.FullName == "System.FlagsAttribute")
+						|| (initValue > 9 && ((initValue & (initValue - 1)) == 0 || (initValue & (initValue + 1)) == 0))))
+				{
+					primitive.SetValue(initValue, $"0x{initValue:X}");
 				}
 				enumDec.Attributes.AddRange(field.Attributes.Select(a => new AttributeSection(typeSystemAstBuilder.ConvertAttribute(a))));
-				enumDec.AddAnnotation(new Semantics.MemberResolveResult(null, field));
+				enumDec.AddAnnotation(new MemberResolveResult(null, field));
 				return enumDec;
 			}
 			typeSystemAstBuilder.UseSpecialConstants = !field.DeclaringType.Equals(field.ReturnType);