Implement const expressions for local variables

runtime/vm/scopes.h

 // 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.
 
 #ifndef VM_SCOPES_H_
 #define VM_SCOPES_H_
 
 #include "vm/allocation.h"
 #include "vm/assembler.h"
 #include "vm/growable_array.h"
@@ skipping 10 matching lines @@
 
 class LocalVariable : public ZoneAllocated {
  public:
   LocalVariable(intptr_t token_pos,
                 const String& name,
                 const AbstractType& type)
     : token_pos_(token_pos),
       name_(name),
       owner_(NULL),
       type_(type),
+      const_value_(NULL),
       is_final_(false),
       is_captured_(false),
       is_invisible_(false),
       index_(LocalVariable::kUnitializedIndex) {
     ASSERT(type.IsZoneHandle());
     ASSERT(type.IsFinalized());
   }
 
   intptr_t token_pos() const { return token_pos_; }
   const String& name() const { return name_; }
@@ skipping 23 matching lines @@
   void set_index(int index) {
     ASSERT(!HasIndex());
     ASSERT(index != kUnitializedIndex);
     index_ = index;
   }
 
   void set_invisible(bool value) {
     is_invisible_ = value;
   }
 
+  bool IsConst() const {
+    return const_value_ != NULL;
+  }
+
+  void SetConstValue(const Instance& value) {
+    ASSERT(value.IsZoneHandle());
+    const_value_ = &value;
+  }
+
+  const Instance* ConstValue() const {
+    ASSERT(IsConst());
+    return const_value_;
+  }
+
   bool Equals(const LocalVariable& other) const;
 
   // Map the frame index to a bit-vector index.  Assumes the variable is
   // allocated to the frame.
   // var_count is the total number of stack-allocated variables including
   // all parameters.
   int BitIndexIn(intptr_t var_count) const;
 
  private:
   static const int kUnitializedIndex = INT_MIN;
 
   const intptr_t token_pos_;
   const String& name_;
   LocalScope* owner_;  // Local scope declaring this variable.
 
   const AbstractType& type_;  // Declaration type of local variable.
 
+  const Instance* const_value_;   // NULL or compile-time const value.
+
   bool is_final_;  // If true, this variable is readonly.
   bool is_captured_;  // If true, this variable lives in the context, otherwise
                       // in the stack frame.
   bool is_invisible_;
   int index_;  // Allocation index in words relative to frame pointer (if not
                // captured), or relative to the context pointer (if captured).
 
   friend class LocalScope;
   DISALLOW_COPY_AND_ASSIGN(LocalVariable);
 };
@@ skipping 243 matching lines @@
   intptr_t end_token_pos_;    // Token index of end of scope.
   GrowableArray<LocalVariable*> variables_;
   GrowableArray<SourceLabel*> labels_;
 
   DISALLOW_COPY_AND_ASSIGN(LocalScope);
 };
 
 }  // namespace dart
 
 #endif  // VM_SCOPES_H_