diff -r e1a6deaa6ebe -r b8f650a441a5 src/compiler/HIR.h
--- a/src/compiler/HIR.h	Sun Nov 18 15:00:08 2012 -0800
+++ b/src/compiler/HIR.h	Sun Nov 18 15:24:30 2012 -0800
@@ -150,6 +150,9 @@
 
     // Pushes a reference to the LValue on the stack.
     virtual void bind(HIRVisitor *visitor, BytecodeEmitter &emitter_) = 0;
+    
+    // Duplicates a stack reference.
+    virtual void hold(BytecodeEmitter &emitter_) = 0;
 
     // Given a stack layout of the form:
     //  [-1]    value
@@ -177,6 +180,7 @@
 
     // Pushes a reference to the LValue on the stack.
     void bind(HIRVisitor *visitor, BytecodeEmitter &emitter_);
+    void hold(BytecodeEmitter &emitter_);
     void store(BytecodeEmitter &emitter_);
     void load(BytecodeEmitter &emitter_);
 
@@ -197,6 +201,7 @@
     DEFINE_HIR(Index);
 
     void bind(HIRVisitor *visitor, BytecodeEmitter &emitter_);
+    void hold(BytecodeEmitter &emitter_);
     void store(BytecodeEmitter &emitter_);
     void load(BytecodeEmitter &emitter_);
 
@@ -217,6 +222,7 @@
     DEFINE_HIR(Global);
 
     void bind(HIRVisitor *visitor, BytecodeEmitter &emitter_);
+    void hold(BytecodeEmitter &emitter_);
     void store(BytecodeEmitter &emitter_);
     void load(BytecodeEmitter &emitter_);
 
@@ -279,6 +285,15 @@
   public:
     HStore(HLValue *lval, HIR *rval)
       : HIR(lval->type()),
+        kind_(TOK_ASSIGN),
+        lval_(lval),
+        rval_(rval)
+    {
+    }
+
+    HStore(TokenKind kind, HLValue *lval, HIR *rval)
+      : HIR(lval->type()),
+        kind_(kind),
         lval_(lval),
         rval_(rval)
     {
@@ -292,10 +307,14 @@
     HIR *rval() const {
         return rval_;
     }
+    TokenKind kind() const {
+        return kind_;
+    }
 
   private:
     HLValue *lval_;
     HIR *rval_;
+    TokenKind kind_;
 };
 
 class HCall : public HIR