Fix icsharpcode/NRefactory#17: Resolving "is" and "as" expressions loses the semantics

ICSharpCode.NRefactory.CSharp/Resolver/ResolveVisitor.cs

@@ -1117,8 +1117,9 @@ namespace ICSharpCode.NRefactory.CSharp.Resolver
 		ResolveResult IAstVisitor<ResolveResult>.VisitAsExpression(AsExpression asExpression)
 		{
 			if (resolverEnabled) {
-				Scan(asExpression.Expression);
-				return new ResolveResult(ResolveType(asExpression.Type));
+				ResolveResult input = Resolve(asExpression.Expression);
+				var targetType = ResolveType(asExpression.Type);
+				return new ConversionResolveResult(targetType, input, Conversion.TryCast);
 			} else {
 				ScanChildren(asExpression);
 				return null;
@@ -1267,8 +1268,15 @@ namespace ICSharpCode.NRefactory.CSharp.Resolver
 		
 		ResolveResult IAstVisitor<ResolveResult>.VisitIsExpression(IsExpression isExpression)
 		{
-			ScanChildren(isExpression);
-			return new ResolveResult(resolver.Compilation.FindType(KnownTypeCode.Boolean));
+			if (resolverEnabled) {
+				ResolveResult input = Resolve(isExpression.Expression);
+				IType targetType = ResolveType(isExpression.Type);
+				IType booleanType = resolver.Compilation.FindType(KnownTypeCode.Boolean);
+				return new TypeIsResolveResult(input, targetType, booleanType);
+			} else {
+				ScanChildren(isExpression);
+				return null;
+			}
 		}
 		
 		// NamedArgumentExpression is "identifier: Expression"

ICSharpCode.NRefactory/ICSharpCode.NRefactory.csproj

@@ -98,6 +98,7 @@
     <Compile Include="Semantics\OperatorResolveResult.cs" />
     <Compile Include="Semantics\ResolveResult.cs" />
     <Compile Include="Semantics\ThisResolveResult.cs" />
+    <Compile Include="Semantics\TypeIsResolveResult.cs" />
     <Compile Include="Semantics\TypeOfResolveResult.cs" />
     <Compile Include="Semantics\TypeResolveResult.cs" />
     <Compile Include="Semantics\UnknownMemberResolveResult.cs" />

ICSharpCode.NRefactory/Semantics/Conversion.cs

@@ -69,6 +69,11 @@ namespace ICSharpCode.NRefactory.Semantics
 		public static readonly Conversion BoxingConversion = new BuiltinConversion(true, 7);
 		public static readonly Conversion UnboxingConversion = new BuiltinConversion(false, 8);
 		
+		/// <summary>
+		/// C# 'as' cast.
+		/// </summary>
+		public static readonly Conversion TryCast = new BuiltinConversion(false, 9);
+		
 		public static Conversion UserDefinedImplicitConversion(IMethod operatorMethod, bool isLifted)
 		{
 			if (operatorMethod == null)
@@ -204,6 +209,10 @@ namespace ICSharpCode.NRefactory.Semantics
 				get { return type == 8; }
 			}
 			
+			public override bool IsTryCast {
+				get { return type == 9; }
+			}
+			
 			public override string ToString()
 			{
 				string name = null;
@@ -231,6 +240,8 @@ namespace ICSharpCode.NRefactory.Semantics
 						return "boxing conversion";
 					case 8:
 						return "unboxing conversion";
+					case 9:
+						return "try cast";
 				}
 				return (isImplicit ? "implicit " : "explicit ") + name + " conversion";
 			}
@@ -337,6 +348,13 @@ namespace ICSharpCode.NRefactory.Semantics
 			get { return false; }
 		}
 		
+		/// <summary>
+		/// Gets whether the conversion is an '<c>as</c>' cast.
+		/// </summary>
+		public virtual bool IsTryCast {
+			get { return false; }
+		}
+		
 		public virtual bool IsIdentityConversion {
 			get { return false; }
 		}

ICSharpCode.NRefactory/Semantics/TypeIsResolveResult.cs

@@ -0,0 +1,47 @@
+// Copyright (c) AlphaSierraPapa for the SharpDevelop Team
+// 
+// Permission is hereby granted, free of charge, to any person obtaining a copy of this
+// software and associated documentation files (the "Software"), to deal in the Software
+// without restriction, including without limitation the rights to use, copy, modify, merge,
+// publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
+// to whom the Software is furnished to do so, subject to the following conditions:
+// 
+// The above copyright notice and this permission notice shall be included in all copies or
+// substantial portions of the Software.
+// 
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
+// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
+// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
+// FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+
+using System;
+using ICSharpCode.NRefactory.TypeSystem;
+
+namespace ICSharpCode.NRefactory.Semantics
+{
+	/// <summary>
+	/// Resolve result for a C# 'is' expression.
+	/// "Input is TargetType".
+	/// </summary>
+	public class TypeIsResolveResult : ResolveResult
+	{
+		public readonly ResolveResult Input;
+		/// <summary>
+		/// Type that is being compared with.
+		/// </summary>
+		public readonly IType TargetType;
+		
+		public TypeIsResolveResult(ResolveResult input, IType targetType, IType booleanType)
+			: base(booleanType)
+		{
+			if (input == null)
+				throw new ArgumentNullException("input");
+			if (targetType == null)
+				throw new ArgumentNullException("targetType");
+			this.Input = input;
+			this.TargetType = targetType;
+		}
+	}
+}