Implement proper scoping for "this" in arrow functions

src/scopes.h

Index: src/scopes.h
diff --git a/src/scopes.h b/src/scopes.h
index 2e418be219b08844bd94f3f7cc9643aea23ec606..66dfeb46a4d7af23f5289842a95f7bca83557bd9 100644
--- a/src/scopes.h
+++ b/src/scopes.h
@@ -22,7 +22,7 @@ class VariableMap: public ZoneHashMap {
   virtual ~VariableMap();
 
   Variable* Declare(Scope* scope, const AstRawString* name, VariableMode mode,
-                    bool is_valid_lhs, Variable::Kind kind,
+                    Variable::Kind kind,
                     InitializationFlag initialization_flag,
                     MaybeAssignedFlag maybe_assigned_flag = kNotAssigned,
                     Interface* interface = Interface::NewValue());
@@ -152,7 +152,7 @@ class Scope: public ZoneObject {
     // RemoveUnresolved().
     DCHECK(!already_resolved());
     VariableProxy* proxy =
-        factory->NewVariableProxy(name, false, interface, position);
+        factory->NewVariableProxy(name, interface, position);

[wingo, 2015/02/06 17:31:19]

Please make this function take an additional Variable::Kind parameter, and pass
that parameter through to NewVariableProxy

     unresolved_.Add(proxy, zone_);
     return proxy;
   }
@@ -223,9 +223,6 @@ class Scope: public ZoneObject {
     scope_uses_super_constructor_call_ = true;
   }
 
-  // Inform the scope that the corresponding code uses "this".
-  void RecordThisUsage() { scope_uses_this_ = true; }
-
   // Set the strict mode flag (unless disabled by a global flag).
   void SetStrictMode(StrictMode strict_mode) { strict_mode_ = strict_mode; }
 
@@ -328,10 +325,6 @@ class Scope: public ZoneObject {
   bool inner_uses_super_constructor_call() const {
     return inner_scope_uses_super_constructor_call_;
   }
-  // Does this scope access "this".
-  bool uses_this() const { return scope_uses_this_; }
-  // Does any inner scope access "this".
-  bool inner_uses_this() const { return inner_scope_uses_this_; }
 
   // ---------------------------------------------------------------------------
   // Accessors.
@@ -343,7 +336,15 @@ class Scope: public ZoneObject {
   StrictMode strict_mode() const { return strict_mode_; }
 
   // The variable corresponding the 'this' value.
-  Variable* receiver() { return receiver_; }
+  Variable* receiver() {
+    DCHECK(has_this_declaration());
+    DCHECK_NOT_NULL(receiver_);
+    return receiver_;
+  }
+
+  bool has_this_declaration() const {
+    return !is_arrow_scope() && is_declaration_scope();
+  }
 
   // The variable holding the function literal for named function
   // literals, or NULL.  Only valid for function scopes.
@@ -541,8 +542,6 @@ class Scope: public ZoneObject {
   bool scope_uses_super_property_;
   // This scope uses "super" constructor ('super(..)').
   bool scope_uses_super_constructor_call_;
-  // This scope uses "this".
-  bool scope_uses_this_;
   // This scope contains an "use asm" annotation.
   bool asm_module_;
   // This scope's outer context is an asm module.
@@ -559,7 +558,6 @@ class Scope: public ZoneObject {
   bool inner_scope_uses_arguments_;
   bool inner_scope_uses_super_property_;
   bool inner_scope_uses_super_constructor_call_;
-  bool inner_scope_uses_this_;
   bool force_eager_compilation_;
   bool force_context_allocation_;
 
@@ -663,6 +661,8 @@ class Scope: public ZoneObject {
   void AllocateStackSlot(Variable* var);
   void AllocateHeapSlot(Variable* var);
   void AllocateParameterLocals();
+  void AllocateParameter(Variable* var, int index);
+  void AllocateReceiver();
   void AllocateNonParameterLocal(Variable* var);
   void AllocateNonParameterLocals();
   void AllocateVariablesRecursively();