[parsing]: eval/arguments parameter names are ok in sloppy mode

src/parser.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/api.h"
 #include "src/ast.h"
 #include "src/bailout-reason.h"
 #include "src/base/platform/platform.h"
@@ skipping 3684 matching lines @@
       const AstRawString* param_name =
           ParseIdentifierOrStrictReservedWord(&is_strict_reserved, CHECK_OK);
 
       // Store locations for possible future error reports.
       if (!eval_args_error_loc.IsValid() && IsEvalOrArguments(param_name)) {
         eval_args_error_loc = scanner()->location();
       }
       if (!reserved_error_loc.IsValid() && is_strict_reserved) {
         reserved_error_loc = scanner()->location();
       }
-      if (!dupe_error_loc.IsValid() && scope_->IsDeclared(param_name)) {
+      if (!dupe_error_loc.IsValid() &&
+          scope_->IsDeclaredParameter(param_name)) {
         duplicate_parameters = FunctionLiteral::kHasDuplicateParameters;
         dupe_error_loc = scanner()->location();
       }
 
       Variable* var = scope_->DeclareParameter(param_name, VAR, is_rest);
       if (is_sloppy(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();
@@ skipping 1751 matching lines @@
     } else {
       const uc16* data = reinterpret_cast<const uc16*>(raw_string->raw_data());
       running_hash = StringHasher::ComputeRunningHash(running_hash, data,
                                                       raw_string->length());
     }
   }
 
   return running_hash;
 }
 } }  // namespace v8::internal