Fix icsharpcode/NRefactory#19: OperatorResolveResult.IsLiftedOperator is false for lifted built-in operators.

ICSharpCode.NRefactory.CSharp/Resolver/CSharpResolver.cs

@@ -804,6 +804,11 @@ namespace ICSharpCode.NRefactory.CSharp.Resolver
 			} else {
 				lhs = Convert(lhs, m.Parameters[0].Type, builtinOperatorOR.ArgumentConversions[0]);
 				rhs = Convert(rhs, m.Parameters[1].Type, builtinOperatorOR.ArgumentConversions[1]);
+				if (builtinOperatorOR.BestCandidate is OverloadResolution.ILiftedOperator) {
+					return new OperatorResolveResult(
+						resultType, BinaryOperatorExpression.GetLinqNodeType(op, this.CheckForOverflow),
+						null, true, new[] { lhs, rhs });
+				}
 				return BinaryOperatorResolveResult(resultType, lhs, op, rhs);
 			}
 		}

ICSharpCode.NRefactory.Tests/CSharp/Resolver/BinaryOperatorTests.cs

@@ -671,5 +671,35 @@ class Test {
 			Assert.IsFalse(irr.IsError);
 			Assert.AreEqual(compilation.FindType(KnownTypeCode.Boolean), irr.Type);
 		}
+		
+		[Test]
+		public void IsLiftedProperty()
+		{
+			string program = @"
+class Test {
+    static void Inc() {
+        int? a = 0, b = 0;
+        int? c = $a + b$;
+    }
+}";
+			var irr = Resolve<OperatorResolveResult>(program);
+			Assert.IsFalse(irr.IsError);
+			Assert.IsTrue(irr.IsLiftedOperator);
+		}
+
+		[Test]
+		public void IsLiftedProperty2()
+		{
+			string program = @"
+class Test {
+    static void Inc() {
+        int? a = 0, b = 0;
+        $b += a$;
+    }
+}";
+			var irr = Resolve<OperatorResolveResult>(program);
+			Assert.IsFalse(irr.IsError);
+			Assert.IsTrue(irr.IsLiftedOperator);
+		}
 	}
 }

ICSharpCode.NRefactory.Tests/ICSharpCode.NRefactory.Tests.csproj

@@ -72,7 +72,8 @@
     <Reference Include="System.Xml" />
     <Reference Include="System.Xml.Linq" />
     <Reference Include="nunit.framework, Version=2.6.0.0, Culture=neutral, PublicKeyToken=96d09a1eb7f44a77">
-      <Private>False</Private>
+      <HintPath>..\..\Mono.Cecil\Test\libs\nunit-2.5.10\nunit.framework.dll</HintPath>
+      <Private>True</Private>
       <SpecificVersion>False</SpecificVersion>
     </Reference>
   </ItemGroup>