[ast/parsing] Pessimistically assume all top-level variables will be assigned.

src/ast/ast.cc

 // 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.
 
 #include "src/ast/ast.h"
 
 #include <cmath>  // For isfinite.
 
 #include "src/ast/compile-time-value.h"
 #include "src/ast/prettyprinter.h"
@@ skipping 184 matching lines @@
   bit_field_ = copy_from->bit_field_;
   DCHECK(!copy_from->is_resolved());
   raw_name_ = copy_from->raw_name_;
 }
 
 void VariableProxy::BindTo(Variable* var) {
   DCHECK((is_this() && var->is_this()) || raw_name() == var->raw_name());
   set_var(var);
   set_is_resolved();
   var->set_is_used();
+  if (is_assigned()) var->set_maybe_assigned();
 }
 
 void VariableProxy::AssignFeedbackVectorSlots(FeedbackVectorSpec* spec,
                                               FeedbackVectorSlotCache* cache) {
   if (UsesVariableFeedbackSlot()) {
     // VariableProxies that point to the same Variable within a function can
     // make their loads from the same IC slot.
     if (var()->IsUnallocated() || var()->mode() == DYNAMIC_GLOBAL) {
       ZoneHashMap::Entry* entry = cache->Get(var());
       if (entry != NULL) {
@@ skipping 844 matching lines @@
 // static
 bool Literal::Match(void* literal1, void* literal2) {
   const AstValue* x = static_cast<Literal*>(literal1)->raw_value();
   const AstValue* y = static_cast<Literal*>(literal2)->raw_value();
   return (x->IsString() && y->IsString() && x->AsString() == y->AsString()) ||
          (x->IsNumber() && y->IsNumber() && x->AsNumber() == y->AsNumber());
 }
 
 }  // namespace internal
 }  // namespace v8