Fix #304 Search for enum underlying type is incorrect

ICSharpCode.Decompiler/Ast/AstBuilder.cs

@@ -318,7 +318,7 @@ namespace ICSharpCode.Decompiler.Ast
 				long expectedEnumMemberValue = 0;
 				bool forcePrintingInitializers = IsFlagsEnum(typeDef);
 				foreach (FieldDefinition field in typeDef.Fields) {
-					if (field.IsRuntimeSpecialName) {
+					if (!field.IsStatic) {
 						// the value__ field
 						if (field.FieldType != typeDef.Module.TypeSystem.Int32) {
 							astType.AddChild(ConvertType(field.FieldType), TypeDeclaration.BaseTypeRole);
@@ -1518,7 +1518,7 @@ namespace ICSharpCode.Decompiler.Ast
 					foreach (FieldDefinition field in enumDefinition.Fields) {
 						if (field.IsStatic && object.Equals(CSharpPrimitiveCast.Cast(TypeCode.Int64, field.Constant, false), val))
 							return ConvertType(type).Member(field.Name).WithAnnotation(field);
-						else if (!field.IsStatic && field.IsRuntimeSpecialName)
+						else if (!field.IsStatic)
 							enumBaseTypeCode = TypeAnalysis.GetTypeCode(field.FieldType); // use primitive type of the enum
 					}
 					if (IsFlagsEnum(enumDefinition)) {

ICSharpCode.Decompiler/ILAst/TypeAnalysis.cs

@@ -1046,18 +1046,28 @@ namespace ICSharpCode.Decompiler.ILAst
 		/// </summary>
 		public const int NativeInt = 33; // treat native int as between int32 and int64
 		
-		public static int GetInformationAmount(TypeReference type)
+		/// <summary>
+		/// Gets the underlying type, if the specified type is an enum.
+		/// Otherwise, returns null.
+		/// </summary>
+		public static TypeReference GetEnumUnderlyingType(TypeReference enumType)
 		{
-			if (type == null)
-				return 0;
-			if (type.IsValueType && !IsArrayPointerOrReference(type)) {
+			// unfortunately we cannot rely on enumType.IsValueType here - it's not set when the instruction operand is a typeref (as opposed to a typespec)
+			if (enumType != null && !IsArrayPointerOrReference(enumType)) {
 				// value type might be an enum
-				TypeDefinition typeDef = type.Resolve() as TypeDefinition;
+				TypeDefinition typeDef = enumType.Resolve() as TypeDefinition;
 				if (typeDef != null && typeDef.IsEnum) {
-					TypeReference underlyingType = typeDef.Fields.Single(f => f.IsRuntimeSpecialName && !f.IsStatic).FieldType;
-					return GetInformationAmount(underlyingType);
+					return typeDef.Fields.Single(f => !f.IsStatic).FieldType;
 				}
 			}
+			return null;
+		}
+		
+		public static int GetInformationAmount(TypeReference type)
+		{
+			type = GetEnumUnderlyingType(type) ?? type;
+			if (type == null)
+				return 0;
 			switch (type.MetadataType) {
 				case MetadataType.Void:
 					return 0;
@@ -1109,14 +1119,9 @@ namespace ICSharpCode.Decompiler.ILAst
 		
 		static bool? IsSigned(TypeReference type)
 		{
-			if (type == null || IsArrayPointerOrReference(type))
+			type = GetEnumUnderlyingType(type) ?? type;
+			if (type == null)
 				return null;
-			// unfortunately we cannot rely on type.IsValueType here - it's not set when the instruction operand is a typeref (as opposed to a typespec)
-			TypeDefinition typeDef = type.Resolve() as TypeDefinition;
-			if (typeDef != null && typeDef.IsEnum) {
-				TypeReference underlyingType = typeDef.Fields.Single(f => f.IsRuntimeSpecialName && !f.IsStatic).FieldType;
-				return IsSigned(underlyingType);
-			}
 			switch (type.MetadataType) {
 				case MetadataType.SByte:
 				case MetadataType.Int16:
@@ -1138,10 +1143,7 @@ namespace ICSharpCode.Decompiler.ILAst
 		
 		static bool OperandFitsInType(TypeReference type, int num)
 		{
-			TypeDefinition typeDef = type.Resolve() as TypeDefinition;
-			if (typeDef != null && typeDef.IsEnum) {
-				type = typeDef.Fields.Single(f => f.IsRuntimeSpecialName && !f.IsStatic).FieldType;
-			}
+			type = GetEnumUnderlyingType(type) ?? type;
 			switch (type.MetadataType) {
 				case MetadataType.SByte:
 					return sbyte.MinValue <= num && num <= sbyte.MaxValue;