Making CompileType a Value object.

runtime/vm/intermediate_language.h

 // Copyright (c) 2013, 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.
 
 #ifndef VM_INTERMEDIATE_LANGUAGE_H_
 #define VM_INTERMEDIATE_LANGUAGE_H_
 
 #include "vm/allocation.h"
 #include "vm/ast.h"
 #include "vm/growable_array.h"
@@ skipping 95 matching lines @@
 //
 // It captures the following properties:
 //    - whether value can potentially be null or it is definitely not null;
 //    - concrete class id of the value or kDynamicCid if unknown statically;
 //    - abstract super type of the value, concrete type of the value in runtime
 //      is guaranteed to be sub type of this type.
 //
 // Values of CompileType form a lattice with a None type as a bottom and a
 // nullable Dynamic type as a top element. Method Union provides a join
 // operation for the lattice.
-class CompileType {
+class CompileType : public ValueObject {
  public:
   static const bool kNullable = true;
   static const bool kNonNullable = false;
 
+  CompileType(const CompileType& other)
+      : ValueObject(),
+        is_nullable_(other.is_nullable_),
+        cid_(other.cid_),
+        type_(other.type_) { }
+
+  CompileType& operator=(const CompileType& other) {
+    is_nullable_ = other.is_nullable_;
+    cid_ = other.cid_;
+    type_ =  other.type_;
+    return *this;
+  }
+

[Florian Schneider, 2013/02/25 11:18:20]

This introduces additional unnecessary dependencies, i.e. whenever adding a
field to CompileType, both have to be updated. Why duplicate the default
behavior of both the copy constructor and the assignment object?

[srdjan, 2013/02/25 17:30:36]

What do you suggest as alternative? Implicit copy constructors should not be
used (see Google style guide).

   // Return type such that concrete value's type in runtime is guaranteed to
   // be subtype of it.
   const AbstractType* ToAbstractType();
 
   // Return class id such that it is either kDynamicCid or in runtime
   // value is guaranteed to have an equal class id.
   intptr_t ToCid();
 
   // Return class id such that it is either kDynamicCid or in runtime
   // value is guaranteed to be either null or have an equal class id.
@@ skipping 4400 matching lines @@
   ForwardInstructionIterator* current_iterator_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(FlowGraphVisitor);
 };
 
 
 }  // namespace dart
 
 #endif  // VM_INTERMEDIATE_LANGUAGE_H_