Simplify "x == false" to "!x" in PushNegation.

ICSharpCode.Decompiler/Ast/Transforms/PushNegation.cs

@@ -3,7 +3,7 @@ using System.Collections.Generic;
 
 using ICSharpCode.NRefactory.CSharp;
 
-namespace Decompiler.Transforms.Ast
+namespace Decompiler.Transforms
 {
 	public class PushNegation: DepthFirstAstVisitor<object, object>
 	{
@@ -24,29 +24,48 @@ namespace Decompiler.Transforms.Ast
 			// !((a) op (b))
 			BinaryOperatorExpression binaryOp = unary.Expression as BinaryOperatorExpression;
 			if (unary.Operator == UnaryOperatorType.Not && binaryOp != null) {
-				bool sucessful = true;
+				bool successful = true;
 				switch (binaryOp.Operator) {
-					case BinaryOperatorType.Equality:           binaryOp.Operator = BinaryOperatorType.InEquality; break;
-					case BinaryOperatorType.InEquality:         binaryOp.Operator = BinaryOperatorType.Equality; break;
-					// TODO: these are invalid for floats (stupid NaN)
-					case BinaryOperatorType.GreaterThan:        binaryOp.Operator = BinaryOperatorType.LessThanOrEqual; break;
-					case BinaryOperatorType.GreaterThanOrEqual: binaryOp.Operator = BinaryOperatorType.LessThan; break;
-					case BinaryOperatorType.LessThanOrEqual:    binaryOp.Operator = BinaryOperatorType.GreaterThan; break;
-					case BinaryOperatorType.LessThan:           binaryOp.Operator = BinaryOperatorType.GreaterThanOrEqual; break;
-					default: sucessful = false; break;
-				}
-				if (sucessful) {
+					case BinaryOperatorType.Equality:
+						binaryOp.Operator = BinaryOperatorType.InEquality;
+						break;
+					case BinaryOperatorType.InEquality:
+						binaryOp.Operator = BinaryOperatorType.Equality;
+						break;
+					case BinaryOperatorType.GreaterThan: // TODO: these are invalid for floats (stupid NaN)
+						binaryOp.Operator = BinaryOperatorType.LessThanOrEqual;
+						break;
+					case BinaryOperatorType.GreaterThanOrEqual:
+						binaryOp.Operator = BinaryOperatorType.LessThan;
+						break;
+					case BinaryOperatorType.LessThanOrEqual:
+						binaryOp.Operator = BinaryOperatorType.GreaterThan;
+						break;
+					case BinaryOperatorType.LessThan:
+						binaryOp.Operator = BinaryOperatorType.GreaterThanOrEqual;
+						break;
+					default:
+						successful = false;
+						break;
+				}
+				if (successful) {
 					unary.ReplaceWith(binaryOp);
 					return binaryOp.AcceptVisitor(this, data);
 				}
 				
-				sucessful = true;
+				successful = true;
 				switch (binaryOp.Operator) {
-					case BinaryOperatorType.ConditionalAnd: binaryOp.Operator = BinaryOperatorType.ConditionalOr; break;
-					case BinaryOperatorType.ConditionalOr:  binaryOp.Operator = BinaryOperatorType.ConditionalAnd; break;
-					default: sucessful = false; break;
+					case BinaryOperatorType.ConditionalAnd:
+						binaryOp.Operator = BinaryOperatorType.ConditionalOr;
+						break;
+					case BinaryOperatorType.ConditionalOr:
+						binaryOp.Operator = BinaryOperatorType.ConditionalAnd;
+						break;
+					default:
+						successful = false;
+						break;
 				}
-				if (sucessful) {
+				if (successful) {
 					binaryOp.Left.ReplaceWith(e => new UnaryOperatorExpression(UnaryOperatorType.Not, e));
 					binaryOp.Right.ReplaceWith(e => new UnaryOperatorExpression(UnaryOperatorType.Not, e));
 					unary.ReplaceWith(binaryOp);
@@ -55,5 +74,28 @@ namespace Decompiler.Transforms.Ast
 			}
 			return base.VisitUnaryOperatorExpression(unary, data);
 		}
+		
+		public override object VisitBinaryOperatorExpression(BinaryOperatorExpression binaryOperatorExpression, object data)
+		{
+			BinaryOperatorType op = binaryOperatorExpression.Operator;
+			bool? rightOperand = null;
+			if (binaryOperatorExpression.Right is PrimitiveExpression)
+				rightOperand = ((PrimitiveExpression)binaryOperatorExpression.Right).Value as bool?;
+			if (op == BinaryOperatorType.Equality && rightOperand == true || op == BinaryOperatorType.InEquality && rightOperand == false) {
+				// 'b == true' or 'b != false' is useless
+				binaryOperatorExpression.AcceptVisitor(this, data);
+				binaryOperatorExpression.ReplaceWith(binaryOperatorExpression.Left);
+				return null;
+			} else if (op == BinaryOperatorType.Equality && rightOperand == false || op == BinaryOperatorType.InEquality && rightOperand == true) {
+				// 'b == false' or 'b != true' is a negation:
+				Expression left = binaryOperatorExpression.Left;
+				left.Remove();
+				UnaryOperatorExpression uoe = new UnaryOperatorExpression(UnaryOperatorType.Not, left);
+				binaryOperatorExpression.ReplaceWith(uoe);
+				return uoe.AcceptVisitor(this, data);
+			} else {
+				return base.VisitBinaryOperatorExpression(binaryOperatorExpression, data);
+			}
+		}
 	}
 }

ICSharpCode.Decompiler/Ast/Transforms/TransformationPipeline.cs

@@ -12,9 +12,10 @@ namespace Decompiler.Transforms
 		public static IAstVisitor<object, object>[] CreatePipeline(CancellationToken cancellationToken)
 		{
 			return new IAstVisitor<object, object>[] {
+				new PushNegation(),
 				new DelegateConstruction() { CancellationToken = cancellationToken },
 				new ConvertConstructorCallIntoInitializer(),
-				new ReplaceMethodCallsWithOperators()
+				new ReplaceMethodCallsWithOperators(),
 			};
 		}
 		
@@ -33,7 +34,6 @@ namespace Decompiler.Transforms
 				}
 				if (Options.ReduceAstOther) {
 					node.AcceptVisitor(new Transforms.Ast.RemoveEmptyElseBody(), null);
-					node.AcceptVisitor(new Transforms.Ast.PushNegation(), null);
 				}
 			}