Revert "Void is not required to be `null` anymore."

runtime/vm/object.cc

 // Copyright (c) 2012, 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/object.h"
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "vm/assembler.h"
 #include "vm/become.h"
@@ skipping 15807 matching lines @@
     const AbstractType& other,
     const TypeArguments& other_instantiator_type_arguments,
     const TypeArguments& other_function_type_arguments,
     Error* bound_error) const {
   ASSERT(other.IsFinalized());
   ASSERT(!other.IsDynamicType());
   ASSERT(!other.IsTypeRef());  // Must be dereferenced at compile time.
   ASSERT(!other.IsMalformed());
   ASSERT(!other.IsMalbounded());
   if (other.IsVoidType()) {
-    return true;
+    return false;
   }
   Zone* zone = Thread::Current()->zone();
   const Class& cls = Class::Handle(zone, clazz());
   if (cls.IsClosureClass()) {
     if (other.IsObjectType() || other.IsDartFunctionType() ||
         other.IsDartClosureType()) {
       return true;
     }
     AbstractType& instantiated_other = AbstractType::Handle(zone, other.raw());
     // Note that we may encounter a bound error in checked mode.
@@ skipping 7481 matching lines @@
   return UserTag::null();
 }
 
 
 const char* UserTag::ToCString() const {
   const String& tag_label = String::Handle(label());
   return tag_label.ToCString();
 }
 
 }  // namespace dart