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 c58d124939676e876a848d5741c94552bab76fa8..15ee267a8771fd84a471ddecefa42c410177d668 100644
--- a/src/scopes.h
+++ b/src/scopes.h
@@ -22,8 +22,7 @@ class VariableMap: public ZoneHashMap {
   virtual ~VariableMap();
 
   Variable* Declare(Scope* scope, const AstRawString* name, VariableMode mode,
-                    bool is_valid_lhs, Variable::Kind kind,
-                    InitializationFlag initialization_flag,
+                    Variable::Kind kind, InitializationFlag initialization_flag,
                     MaybeAssignedFlag maybe_assigned_flag = kNotAssigned);
 
   Variable* Lookup(const AstRawString* name);
@@ -142,12 +141,14 @@ class Scope: public ZoneObject {
   // Create a new unresolved variable.
   VariableProxy* NewUnresolved(AstNodeFactory* factory,
                                const AstRawString* name,
+                               Variable::Kind variable_kind,
                                int position = RelocInfo::kNoPosition) {
     // 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, false, position);
+    VariableProxy* proxy =
+        factory->NewVariableProxy(name, variable_kind, position);
     unresolved_.Add(proxy, zone_);
     return proxy;
   }
@@ -327,7 +328,15 @@ 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_;
+  }
+
+  bool has_this_declaration() const {
+    return !is_arrow_scope() && is_declaration_scope();
+  }
 
   // The variable corresponding to the 'new.target' value.
   Variable* new_target_var() { return new_target_; }
@@ -662,6 +671,8 @@ class Scope: public ZoneObject {
   void AllocateNonParameterLocals(Isolate* isolate);
   void AllocateVariablesRecursively(Isolate* isolate);
   void AllocateModulesRecursively(Scope* host_scope);
+  void AllocateParameter(Variable* var, int index);
+  void AllocateReceiver();
 
   // Resolve and fill in the allocation information for all variables
   // in this scopes. Must be called *after* all scopes have been