Correct handling of temporaries as parameters.

src/parser.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_PARSER_H_
 #define V8_PARSER_H_
 
 #include "src/allocation.h"
 #include "src/ast.h"
 #include "src/compiler.h"  // TODO(titzer): remove this include dependency
@@ skipping 1300 matching lines @@
 void ParserTraits::DeclareFormalParameter(
     ParserFormalParameters* parameters, Expression* pattern, bool is_rest,
     ExpressionClassifier* classifier) {
   bool is_duplicate = false;
   bool is_simple = pattern->IsVariableProxy();
   DCHECK(parser_->allow_harmony_destructuring() || is_simple);
 
   const AstRawString* name = is_simple
                                  ? pattern->AsVariableProxy()->raw_name()
                                  : parser_->ast_value_factory()->empty_string();
+  VariableMode mode = is_simple ? VAR : TEMPORARY;
   Variable* var =
-      parameters->scope->DeclareParameter(name, VAR, is_rest, &is_duplicate);
+      parameters->scope->DeclareParameter(name, mode, is_rest, &is_duplicate);
   parameters->AddParameter(var, is_simple ? nullptr : pattern);
   if (is_duplicate) {
     classifier->RecordDuplicateFormalParameterError(
         parser_->scanner()->location());
   }
   if (is_sloppy(parameters->scope->language_mode())) {
     // TODO(sigurds) Mark every parameter as maybe assigned. This is a
     // conservative approximation necessary to account for parameters
     // that are assigned via the arguments array.
     var->set_maybe_assigned();
   }
 }
 
 
 void ParserTraits::AddParameterInitializationBlock(
     const ParserFormalParameters& parameters,
     ZoneList<v8::internal::Statement*>* body, bool* ok) {
   if (!parameters.is_simple) {
     auto* init_block =
         parser_->BuildParameterInitializationBlock(parameters, ok);
     if (!*ok) return;
     if (init_block != nullptr) {
       body->Add(init_block, parser_->zone());
     }
   }
 }
 } }  // namespace v8::internal
 
 #endif  // V8_PARSER_H_