Add support for 'Dynamic' type in the VM.

runtime/vm/object.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/object.h"
 
 #include "vm/assembler.h"
 #include "vm/assert.h"
 #include "vm/bigint_operations.h"
 #include "vm/bootstrap.h"
@@ skipping 240 matching lines @@
     Instance& sentinel = Instance::Handle();
     sentinel ^= Object::Allocate(cls, Instance::InstanceSize(), Heap::kOld);
     sentinel_ = sentinel.raw();
 
     Instance& transition_sentinel = Instance::Handle();
     transition_sentinel ^=
         Object::Allocate(cls, Instance::InstanceSize(), Heap::kOld);
     transition_sentinel_ = transition_sentinel.raw();
   }
 
+  // The interface "Dynamic" is not a VM internal class. It is the type class of
+  // the "unknown type". For efficiency, we allocate it in the VM isolate.
+  // Therefore, it cannot have a heap allocated name (the name is hard coded,
+  // see GetSingletonClassIndex) and its array fields cannot be set to the empty
+  // array, but remain null.
+  cls = Class::New<Instance>();
+  cls.set_is_interface();
+  dynamic_class_ = cls.raw();
+
   // Allocate the remaining VM internal classes.
   cls = Class::New<UnresolvedClass>();
   unresolved_class_class_ = cls.raw();
 
   cls = Class::New<Instance>();
-  dynamic_class_ = cls.raw();
-
-  cls = Class::New<Instance>();
   void_class_ = cls.raw();
 
   cls = Class::New<ParameterizedType>();
   parameterized_type_class_ = cls.raw();
 
   cls = Class::New<TypeParameter>();
   type_parameter_class_ = cls.raw();
 
   cls = Class::New<InstantiatedType>();
   instantiated_type_class_ = cls.raw();
@@ skipping 271 matching lines @@
   core_lib.AddClass(cls);
   type = Type::NewNonParameterizedType(cls);
   object_store->set_string_interface(type);
 
   name = String::NewSymbol("bool");
   cls = Class::NewInterface(name, script);
   core_lib.AddClass(cls);
   type = Type::NewNonParameterizedType(cls);
   object_store->set_bool_interface(type);
 
-  // The classes 'Null', 'Dynamic', and 'void' are not registered in the class
-  // dictionary and are not named, but corresponding types are stored in the
-  // object store.
+  // The classes 'Null' and 'void' are not registered in the class dictionary,
+  // because their names are reserved keywords. Their names are not heap
+  // allocated, because the classes reside in the VM isolate.
+  // The corresponding types are stored in the object store.
   cls = null_class_;
   type = Type::NewNonParameterizedType(cls);
   object_store->set_null_type(type);
 
-  cls = dynamic_class_;
-  type = Type::NewNonParameterizedType(cls);
-  object_store->set_dynamic_type(type);
-
   cls = void_class_;
   type = Type::NewNonParameterizedType(cls);
   object_store->set_void_type(type);
 
+  // The class 'Dynamic' is registered in the class dictionary because its name
+  // is a built-in identifier, rather than a reserved keyword. Its name is not
+  // heap allocated, because the class resides in the VM isolate.
+  // The corresponding type, the "unknown type", is stored in the object store.
+  cls = dynamic_class_;
+  type = Type::NewNonParameterizedType(cls);
+  object_store->set_dynamic_type(type);
+  core_lib.AddClass(cls);
+
   // Finish the initialization by compiling the bootstrap script containing the
   // implementation of the internal classes.
   Bootstrap::Compile(Library::Handle(Library::CoreLibrary()), script);
   Bootstrap::Compile(Library::Handle(Library::CoreImplLibrary()), impl_script);
 
   Bootstrap::SetupNativeResolver();
 
   // Remove the Object superclass cycle by setting the super type to null (not
   // to the type of null).
   cls = object_store->object_class();
@@ skipping 6202 matching lines @@
   const String& str = String::Handle(pattern());
   const char* format = "JSRegExp: pattern=%s flags=%s";
   intptr_t len = OS::SNPrint(NULL, 0, format, str.ToCString(), Flags());
   char* chars = reinterpret_cast<char*>(
       Isolate::Current()->current_zone()->Allocate(len + 1));
   OS::SNPrint(chars, (len + 1), format, str.ToCString(), Flags());
   return chars;
 }
 
 }  // namespace dart