[destructuring] Implement parameter pattern matching.

src/scopes.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/v8.h"
 
 #include "src/accessors.h"
 #include "src/bootstrapper.h"
 #include "src/messages.h"
 #include "src/parser.h"
@@ skipping 448 matching lines @@
     if (var != NULL) return var;
   }
   return NULL;
 }
 
 
 Variable* Scope::DeclareParameter(const AstRawString* name, VariableMode mode,
                                   bool is_rest, bool* is_duplicate) {
   DCHECK(!already_resolved());
   DCHECK(is_function_scope());
-  Variable* var = variables_.Declare(this, name, mode, Variable::NORMAL,
-                                     kCreatedInitialized);
+
+  Variable* var;
+  if (!name->IsEmpty()) {
+    var = variables_.Declare(this, name, mode, Variable::NORMAL,
+                             kCreatedInitialized);
+    // TODO(wingo): Avoid O(n^2) check.
+    *is_duplicate = IsDeclaredParameter(name);
+  } else {
+    var = new (zone())
+        Variable(this, name, TEMPORARY, Variable::NORMAL, kCreatedInitialized);
+  }
   if (is_rest) {
     DCHECK_NULL(rest_parameter_);
     rest_parameter_ = var;
     rest_index_ = num_parameters();
   }
-  // TODO(wingo): Avoid O(n^2) check.
-  *is_duplicate = IsDeclaredParameter(name);
   params_.Add(var, zone());
   return var;
 }
 
 
 Variable* Scope::DeclareLocal(const AstRawString* name, VariableMode mode,
                               InitializationFlag init_flag, Variable::Kind kind,
                               MaybeAssignedFlag maybe_assigned_flag,
                               int declaration_group_start) {
   DCHECK(!already_resolved());
@@ skipping 1079 matching lines @@
 }
 
 
 int Scope::ContextLocalCount() const {
   if (num_heap_slots() == 0) return 0;
   return num_heap_slots() - Context::MIN_CONTEXT_SLOTS -
       (function_ != NULL && function_->proxy()->var()->IsContextSlot() ? 1 : 0);
 }
 }  // namespace internal
 }  // namespace v8