[CodeActions] ConvertCastToAsAction: insert parentheses when necessary

ICSharpCode.NRefactory.CSharp/Refactoring/CodeActions/ConvertCastToAsAction.cs

@@ -34,7 +34,7 @@ namespace ICSharpCode.NRefactory.CSharp.Refactoring
 	[ContextAction ("Convert cast to 'as'.", Description = "Convert cast to 'as'.")]
 	public class ConvertCastToAsAction : SpecializedCodeAction<CastExpression>
 	{
-
+		static InsertParenthesesVisitor insertParentheses = new InsertParenthesesVisitor ();
 		protected override CodeAction GetAction (RefactoringContext context, CastExpression node)
 		{
 			if (node.Expression.Contains (context.Location))
@@ -42,10 +42,23 @@ namespace ICSharpCode.NRefactory.CSharp.Refactoring
 			// only works on reference and nullable types
 			var type = context.ResolveType (node.Type);
 			var typeDef = type.GetDefinition ();
-			if (type.IsReferenceType == true || (typeDef != null && typeDef.KnownTypeCode == KnownTypeCode.NullableOfT))
-				return new CodeAction (context.TranslateString ("Convert cast to 'as'"), script =>
-					script.Replace (node, new AsExpression (node.Expression.Clone (), node.Type.Clone ())));
-
+			var isNullable = typeDef != null && typeDef.KnownTypeCode == KnownTypeCode.NullableOfT;
+			if (type.IsReferenceType == true || isNullable) {
+				return new CodeAction (context.TranslateString ("Convert cast to 'as'"), script => {
+					var asExpr = new AsExpression (node.Expression.Clone (), node.Type.Clone ());
+					// if parent is an expression, clone parent and replace the case expression with asExpr,
+					// so that we can inset parentheses
+					var parentExpr = node.Parent.Clone () as Expression;
+					if (parentExpr != null) {
+						var castExpr = parentExpr.GetNodeContaining (node.StartLocation, node.EndLocation);
+						castExpr.ReplaceWith (asExpr);
+						parentExpr.AcceptVisitor (insertParentheses);
+						script.Replace (node.Parent, parentExpr);
+					} else {
+						script.Replace (node, asExpr);
+					}
+				});
+			}
 			return null;
 		}
 	}

ICSharpCode.NRefactory.Tests/CSharp/CodeActions/ConvertCastToAsTests.cs

@@ -32,7 +32,7 @@ namespace ICSharpCode.NRefactory.CSharp.CodeActions
 	[TestFixture]
 	public class ConvertCastToAsTests : ContextActionTestBase
 	{
-		void TestType(string type)
+		void TestType (string type)
 		{
 			string input = @"
 using System;
@@ -56,19 +56,19 @@ class TestClass
 		}
 
 		[Test]
-		public void Test()
+		public void Test ()
 		{
 			TestType ("Exception");
 		}
 
 		[Test]
-		public void TestNullable()
+		public void TestNullable ()
 		{
 			TestType ("int?");	
 		}
 
 		[Test]
-		public void TestNonReferenceType()
+		public void TestNonReferenceType ()
 		{
 			TestWrongContext<ConvertCastToAsAction> (@"
 using System;
@@ -76,9 +76,29 @@ class TestClass
 {
 	void Test (object a)
 	{
-		var b = (int)$a;
+		var b = ($int)a;
 	}
 }");
 		}
+
+		[Test]
+		public void TestInsertParentheses ()
+		{
+			string input = @"
+class TestClass {
+	void TestMethod (object o)
+	{
+		var b = 1 + ($TestClass)o;
+	}
+}";
+			string output = @"
+class TestClass {
+	void TestMethod (object o)
+	{
+		var b = 1 + (o as TestClass);
+	}
+}";
+			Test<ConvertCastToAsAction> (input, output);
+		}
 	}
 }