Use equals.

ICSharpCode.NRefactory/CSharp/Resolver/MemberLookup.cs

@@ -99,7 +99,7 @@ namespace ICSharpCode.NRefactory.CSharp.Resolver
 		
 		bool IsProtectedAccessible(ITypeDefinition declaringType)
 		{
-			if (declaringType == currentTypeDefinition)
+			if (declaringType.Equals (currentTypeDefinition))
 				return true;
 			// PERF: this might hurt performance as this method is called several times (once for each member)
 			// make sure resolving base types is cheap (caches?) or cache within the MemberLookup instance