Add comparisons with 0 or null if necessary. Closes #8.

ICSharpCode.Decompiler/Ast/AstMethodBodyBuilder.cs

@@ -235,19 +235,42 @@ namespace Decompiler
 			List<Ast.Expression> args = TransformExpressionArguments(expr);
 			Ast.Expression arg1 = args.Count >= 1 ? args[0] : null;
 			Ast.Expression arg2 = args.Count >= 2 ? args[1] : null;
+			TypeReference arg1Type = args.Count >= 1 ? expr.Arguments[0].InferredType : null;
 			switch(expr.OpCode.Code) {
-					case Code.Brfalse: return new Ast.UnaryOperatorExpression(UnaryOperatorType.Not, arg1);
-					case Code.Brtrue:  return arg1;
-					case Code.Beq:     return new Ast.BinaryOperatorExpression(arg1, BinaryOperatorType.Equality, arg2);
-					case Code.Bge:     return new Ast.BinaryOperatorExpression(arg1, BinaryOperatorType.GreaterThanOrEqual, arg2);
-					case Code.Bge_Un:  return new Ast.BinaryOperatorExpression(arg1, BinaryOperatorType.GreaterThanOrEqual, arg2);
-					case Code.Bgt:     return new Ast.BinaryOperatorExpression(arg1, BinaryOperatorType.GreaterThan, arg2);
-					case Code.Bgt_Un:  return new Ast.BinaryOperatorExpression(arg1, BinaryOperatorType.GreaterThan, arg2);
-					case Code.Ble:     return new Ast.BinaryOperatorExpression(arg1, BinaryOperatorType.LessThanOrEqual, arg2);
-					case Code.Ble_Un:  return new Ast.BinaryOperatorExpression(arg1, BinaryOperatorType.LessThanOrEqual, arg2);
-					case Code.Blt:     return new Ast.BinaryOperatorExpression(arg1, BinaryOperatorType.LessThan, arg2);
-					case Code.Blt_Un:  return new Ast.BinaryOperatorExpression(arg1, BinaryOperatorType.LessThan, arg2);
-					case Code.Bne_Un:  return new Ast.BinaryOperatorExpression(arg1, BinaryOperatorType.InEquality, arg2);
+				case Code.Brfalse:
+					if (arg1Type == typeSystem.Boolean)
+						return new Ast.UnaryOperatorExpression(UnaryOperatorType.Not, arg1);
+					else if (TypeAnalysis.IsIntegerOrEnum(typeSystem, arg1Type))
+						return new Ast.BinaryOperatorExpression(arg1, BinaryOperatorType.Equality, new PrimitiveExpression(0));
+					else
+						return new Ast.BinaryOperatorExpression(arg1, BinaryOperatorType.Equality, new NullReferenceExpression());
+				case Code.Brtrue:
+					if (arg1Type == typeSystem.Boolean)
+						return arg1;
+					else if (TypeAnalysis.IsIntegerOrEnum(typeSystem, arg1Type))
+						return new Ast.BinaryOperatorExpression(arg1, BinaryOperatorType.InEquality, new PrimitiveExpression(0));
+					else
+						return new Ast.BinaryOperatorExpression(arg1, BinaryOperatorType.InEquality, new NullReferenceExpression());
+				case Code.Beq:
+					return new Ast.BinaryOperatorExpression(arg1, BinaryOperatorType.Equality, arg2);
+				case Code.Bge:
+					return new Ast.BinaryOperatorExpression(arg1, BinaryOperatorType.GreaterThanOrEqual, arg2);
+				case Code.Bge_Un:
+					return new Ast.BinaryOperatorExpression(arg1, BinaryOperatorType.GreaterThanOrEqual, arg2);
+				case Code.Bgt:
+					return new Ast.BinaryOperatorExpression(arg1, BinaryOperatorType.GreaterThan, arg2);
+				case Code.Bgt_Un:
+					return new Ast.BinaryOperatorExpression(arg1, BinaryOperatorType.GreaterThan, arg2);
+				case Code.Ble:
+					return new Ast.BinaryOperatorExpression(arg1, BinaryOperatorType.LessThanOrEqual, arg2);
+				case Code.Ble_Un:
+					return new Ast.BinaryOperatorExpression(arg1, BinaryOperatorType.LessThanOrEqual, arg2);
+				case Code.Blt:
+					return new Ast.BinaryOperatorExpression(arg1, BinaryOperatorType.LessThan, arg2);
+				case Code.Blt_Un:
+					return new Ast.BinaryOperatorExpression(arg1, BinaryOperatorType.LessThan, arg2);
+				case Code.Bne_Un:
+					return new Ast.BinaryOperatorExpression(arg1, BinaryOperatorType.InEquality, arg2);
 					default: throw new Exception("Bad opcode");
 			}
 			/*

ICSharpCode.Decompiler/ILAst/TypeAnalysis.cs

@@ -99,6 +99,10 @@ namespace Decompiler
 						}
 						return ctor.DeclaringType;
 					}
+				case Code.Ldfld:
+					return UnpackModifiers(((FieldReference)expr.Operand).FieldType);
+				case Code.Ldsfld:
+					return UnpackModifiers(((FieldReference)expr.Operand).FieldType);
 				case Code.Or:
 					return InferArgumentsInBinaryOperator(expr);
 				case Code.Shl:
@@ -107,9 +111,9 @@ namespace Decompiler
 						InferTypeForExpression(expr.Arguments[1], typeSystem.Int32);
 					return InferTypeForExpression(expr.Arguments[0], expectedType);
 				case Code.Ldc_I4:
-					return (IsSigned(expectedType) != null || expectedType == typeSystem.Boolean) ? expectedType : typeSystem.Int32;
+					return (IsIntegerOrEnum(expectedType) || expectedType == typeSystem.Boolean) ? expectedType : typeSystem.Int32;
 				case Code.Ldc_I8:
-					return (IsSigned(expectedType) != null) ? expectedType : typeSystem.Int64;
+					return (IsIntegerOrEnum(expectedType)) ? expectedType : typeSystem.Int64;
 				case Code.Conv_I8:
 					return (GetInformationAmount(expectedType) == 64 && IsSigned(expectedType) == true) ? expectedType : typeSystem.Int64;
 				case Code.Dup:
@@ -135,6 +139,13 @@ namespace Decompiler
 			}
 		}
 		
+		static TypeReference UnpackModifiers(TypeReference type)
+		{
+			while (type is OptionalModifierType || type is RequiredModifierType)
+				type = ((TypeSpecification)type).ElementType;
+			return type;
+		}
+		
 		TypeReference InferArgumentsInBinaryOperator(ILExpression expr)
 		{
 			ILExpression left = expr.Arguments[0];
@@ -194,6 +205,16 @@ namespace Decompiler
 			return 100; // we consider structs/objects to have more information than any primitives
 		}
 		
+		bool IsIntegerOrEnum(TypeReference type)
+		{
+			return IsIntegerOrEnum(typeSystem, type);
+		}
+		
+		public static bool IsIntegerOrEnum(TypeSystem typeSystem, TypeReference type)
+		{
+			return IsSigned(typeSystem, type) != null;
+		}
+		
 		bool? IsSigned(TypeReference type)
 		{
 			return IsSigned(typeSystem, type);