Factor formal argument parsing into ParserBase

src/scopes.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_SCOPES_H_
 #define V8_SCOPES_H_
 
 #include "src/ast.h"
 #include "src/pending-compilation-error-handler.h"
 #include "src/zone.h"
@@ skipping 107 matching lines @@
   // outer scope. Only possible for function scopes; at most one variable.
   void DeclareFunctionVar(VariableDeclaration* declaration) {
     DCHECK(is_function_scope());
     function_ = declaration;
   }
 
   // Declare a parameter in this scope.  When there are duplicated
   // parameters the rightmost one 'wins'.  However, the implementation
   // expects all parameters to be declared and from left to right.
   Variable* DeclareParameter(const AstRawString* name, VariableMode mode,
-                             bool is_rest = false);
+                             bool is_rest, bool* is_duplicate);
 
   // Declare a local variable in this scope. If the variable has been
   // declared before, the previously declared variable is returned.
   Variable* DeclareLocal(const AstRawString* name, VariableMode mode,
                          InitializationFlag init_flag, Variable::Kind kind,
                          MaybeAssignedFlag maybe_assigned_flag = kNotAssigned);
 
   // Declare an implicit global variable in this scope which must be a
   // script scope.  The variable was introduced (possibly from an inner
   // scope) by a reference to an unresolved variable with no intervening
@@ skipping 591 matching lines @@
 
   AstValueFactory* ast_value_factory_;
   Zone* zone_;
 
   PendingCompilationErrorHandler pending_error_handler_;
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_SCOPES_H_