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

src/scopes.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_SCOPES_H_
 #define V8_SCOPES_H_
 
 #include "src/ast.h"
 #include "src/pending-compilation-error-handler.h"
 #include "src/zone.h"
@@ skipping 127 matching lines @@
   // Declare an implicit global variable in this scope which must be a
   // script scope.  The variable was introduced (possibly from an inner
   // scope) by a reference to an unresolved variable with no intervening
   // with statements or eval calls.
   Variable* DeclareDynamicGlobal(const AstRawString* name);
 
   // Create a new unresolved variable.
   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;
   }
 
   // Remove a unresolved variable. During parsing, an unresolved variable
   // may have been added optimistically, but then only the variable name
   // was used (typically for labels). If the variable was not declared, the
   // addition introduced a new unresolved variable which may end up being
   // allocated globally as a "ghost" variable. RemoveUnresolved removes
   // such a variable again if it was added; otherwise this is a no-op.
@@ skipping 174 matching lines @@
 
   // The type of this scope.
   ScopeType scope_type() const { return scope_type_; }
 
   FunctionKind function_kind() const { return function_kind_; }
 
   // The language mode of this scope.
   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_; }
 
   // The variable holding the function literal for named function
   // literals, or NULL.  Only valid for function scopes.
   VariableDeclaration* function() const {
     DCHECK(is_function_scope());
     return function_;
   }
@@ skipping 339 matching lines @@
   bool MustAllocateInContext(Variable* var);
   bool HasArgumentsParameter(Isolate* isolate);
 
   // Variable allocation.
   void AllocateStackSlot(Variable* var);
   void AllocateHeapSlot(Variable* var);
   void AllocateParameterLocals(Isolate* isolate);
   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
   // in this scopes. Must be called *after* all scopes have been
   // processed (parsed) to ensure that unresolved variables can be
   // resolved properly.
   //
   // In the case of code compiled and run using 'eval', the context
   // parameter is the context in which eval was called.  In all other
   // cases the context parameter is an empty handle.
@@ skipping 26 matching lines @@
   PendingCompilationErrorHandler pending_error_handler_;
 
   // For tracking which classes are declared consecutively. Needed for strong
   // mode.
   int class_declaration_group_start_;
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_SCOPES_H_