Fix typo in --verify_implements functionality (issue 1291).

runtime/vm/class_finalizer.cc

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/class_finalizer.h"
 
 #include "vm/flags.h"
 #include "vm/heap.h"
 #include "vm/isolate.h"
 #include "vm/longjump.h"
@@ skipping 150 matching lines @@
       while (class_function.IsNull()) {
         test_class = test_class.SuperClass();
         if (test_class.IsNull()) break;
         class_function = test_class.LookupDynamicFunction(function_name);
       }
       if (class_function.IsNull()) {
         OS::Print("%s implements '%s' missing: '%s'\n",
             class_name.ToCString(),
             interface_name.ToCString(),
             function_name.ToCString());
-      } else if (class_function.IsSubtypeOf(TypeArguments::Handle(),
-                                            interface_function,
-                                            TypeArguments::Handle())) {
+      } else if (!class_function.IsSubtypeOf(TypeArguments::Handle(),
+                                             interface_function,
+                                             TypeArguments::Handle())) {
         OS::Print("The type of instance method '%s' in class '%s' is not a "
                   "subtype of the type of '%s' in interface '%s'\n",
                   function_name.ToCString(),
                   class_name.ToCString(),
                   function_name.ToCString(),
                   interface_name.ToCString());
       }
     }
   }
 }
@@ skipping 993 matching lines @@
   va_end(args);
   if (FLAG_warning_as_error) {
     Isolate::Current()->long_jump_base()->Jump(1, error);
     UNREACHABLE();
   } else {
     OS::Print("%s", error.ToErrorCString());
   }
 }
 
 }  // namespace dart