Avoid temporary Vectors for arrow function parameter lists

src/preparser.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_PREPARSER_H
 #define V8_PREPARSER_H
 
 #include "src/v8.h"
 
 #include "src/func-name-inferrer.h"
@@ skipping 1231 matching lines @@
                                       int* expected_property_count, bool* ok) {
     UNREACHABLE();
   }
 
   V8_INLINE PreParserStatementList
       ParseEagerFunctionBody(PreParserIdentifier function_name, int pos,
                              Variable* fvar, Token::Value fvar_init_op,
                              bool is_generator, bool* ok);
 
   // Utility functions
-  Vector<PreParserIdentifier> ParameterListFromExpression(
-      PreParserExpression expression, bool* ok) {
+  unsigned DeclareArrowParametersFromExpression(PreParserExpression expression,
+                                                PreParserScope* scope,
+                                                Scanner::Location* dupe_loc,
+                                                bool* ok) {
     // TODO(aperez): Detect duplicated identifiers in paramlists.
     *ok = expression.IsValidArrowParamList();
-    return Vector<PreParserIdentifier>::empty();
+    return 0;
   }
 
   static AstValueFactory* ast_value_factory() { return NULL; }
 
   void CheckConflictingVarDeclarations(PreParserScope scope, bool* ok) {}
 
   // Temporary glue; these functions will move to ParserBase.
   PreParserExpression ParseV8Intrinsic(bool* ok);
   PreParserExpression ParseFunctionLiteral(
       PreParserIdentifier name,
@@ skipping 1162 matching lines @@
   }
   ASSERT(false);
   return this->EmptyExpression();
 }
 
 
 template <class Traits>
 typename ParserBase<Traits>::ExpressionT ParserBase<
     Traits>::ParseArrowFunctionLiteral(int start_pos, ExpressionT params_ast,
                                        bool* ok) {
-  typename Traits::Type::ParameterIdentifierVector params =
-      Traits::ParameterListFromExpression(params_ast, ok);
-
-  if (!*ok) {
-    ReportMessageAt(Scanner::Location(start_pos, scanner()->location().beg_pos),
-                    "malformed_arrow_function_parameter_list");
-    params.Dispose();
-    return this->EmptyExpression();
-  }
-
   // TODO(aperez): Change this to use ARROW_SCOPE
   typename Traits::Type::ScopePtr scope =
       this->NewScope(scope_, FUNCTION_SCOPE);
 
   FunctionState function_state(&function_state_, &scope_, &scope, zone(),
                                this->ast_value_factory());
   Scanner::Location dupe_error_loc = Scanner::Location::invalid();
+  unsigned num_params = Traits::DeclareArrowParametersFromExpression(
+      params_ast, scope_, &dupe_error_loc, ok);
+  if (!*ok) {
+    ReportMessageAt(Scanner::Location(start_pos, scanner()->location().beg_pos),
+                    "malformed_arrow_function_parameter_list");
+    return this->EmptyExpression();
+  }
 
-  if (params.length() > Code::kMaxArguments) {
+  if (num_params > Code::kMaxArguments) {
     ReportMessageAt(Scanner::Location(params_ast->position(), position()),
                     "too_many_parameters");
     *ok = false;
-    params.Dispose();
     return this->EmptyExpression();
   }
 
-  for (int i = 0; i < params.length(); ++i) {
-    const IdentifierT param_name = params.at(i)->raw_name();
-    if (!dupe_error_loc.IsValid() && scope_->IsDeclared(param_name)) {
-      int param_pos = params.at(i)->position();
-      dupe_error_loc =
-          Scanner::Location(param_pos, param_pos + param_name->length());
-    }
-    scope_->DeclareParameter(param_name, VAR);
-  }
-
   ExpressionT expression = ParseArrowFunctionLiteralBody(
-      &function_state, scope, params.length(), Scanner::Location::invalid(),
+      &function_state, scope, num_params, Scanner::Location::invalid(),
       dupe_error_loc, Scanner::Location::invalid(),
       FunctionLiteral::kNotParenthesized, start_pos, CHECK_OK);
-  params.Dispose();
   return expression;
 }
 
 
 template <class Traits>
 typename ParserBase<Traits>::ExpressionT
 ParserBase<Traits>::ParseArrowFunctionLiteralBody(
     FunctionState* function_state, typename Traits::Type::ScopePtr scope,
     int num_parameters, const Scanner::Location& eval_args_error_loc,
     const Scanner::Location& dupe_error_loc,
@@ skipping 112 matching lines @@
       parser()->ReportMessage("accessor_get_set");
     }
     *ok = false;
   }
 }
 
 
 } }  // v8::internal
 
 #endif  // V8_PREPARSER_H