Resolve references to "this" the same way as normal variables

src/scopes.h

Index: src/scopes.h
diff --git a/src/scopes.h b/src/scopes.h
index 5e3dc1f0654bf65c3ee738665fcb7bf2107be63b..7d326cf33135b68eb9dbf6ad11225b12b0f6239a 100644
--- a/src/scopes.h
+++ b/src/scopes.h
@@ -145,13 +145,14 @@ class Scope: public ZoneObject {
   VariableProxy* NewUnresolved(AstNodeFactory* factory,
                                const AstRawString* name,
                                int start_position = RelocInfo::kNoPosition,
-                               int end_position = RelocInfo::kNoPosition) {
+                               int end_position = RelocInfo::kNoPosition,
+                               Variable::Kind kind = Variable::NORMAL) {

[arv (Not doing code reviews), 2015/04/28 14:26:18]

Can we keep the position last for consistency.

[wingo, 2015/04/28 15:07:42]

Acknowledged.

     // Note that we must not share the unresolved variables with
     // the same name because they may be removed selectively via
     // RemoveUnresolved().
     DCHECK(!already_resolved());
-    VariableProxy* proxy = factory->NewVariableProxy(
-        name, Variable::NORMAL, start_position, end_position);
+    VariableProxy* proxy =
+        factory->NewVariableProxy(name, kind, start_position, end_position);
     unresolved_.Add(proxy, zone_);
     return proxy;
   }
@@ -346,7 +347,18 @@ class Scope: public ZoneObject {
   LanguageMode language_mode() const { return language_mode_; }
 
   // The variable corresponding to the 'this' value.
-  Variable* receiver() { return receiver_; }
+  Variable* receiver() {
+    DCHECK(has_this_declaration());
+    DCHECK_NOT_NULL(receiver_);
+    return receiver_;
+  }
+
+  Variable* LookupThis() { return Lookup(ast_value_factory_->this_string()); }
+
+  bool has_this_declaration() const {
+    return (is_function_scope() && !is_arrow_scope()) || is_module_scope() ||
+           is_script_scope();

[arv (Not doing code reviews), 2015/04/28 14:26:18]

What about eval scope?

[wingo, 2015/04/28 15:07:42]

Doesn't declare a "this" :)  Grep the spec for GetThisBinding.  The only reason
eval scopes used to have a "this" binding was because it was copied from its
value in the outer scope to the eval code.

Given that functions don't have this gnarly this-aliasing bug I mentioned about
script contexts, this means that super calls in arrow functions should be able
to BindThisValue correctly.  But, I haven't fully grokked super calls yet.

+  }
 
   // The variable corresponding to the 'new.target' value.
   Variable* new_target_var() { return new_target_; }
@@ -706,6 +718,8 @@ class Scope: public ZoneObject {
   void AllocateNonParameterLocal(Isolate* isolate, Variable* var);
   void AllocateNonParameterLocals(Isolate* isolate);
   void AllocateVariablesRecursively(Isolate* isolate);
+  void AllocateParameter(Variable* var, int index);
+  void AllocateReceiver();
   void AllocateModules();
 
   // Resolve and fill in the allocation information for all variables