[es6] implement optional parameters via desugaring (with scoping)

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 83 matching lines @@
   // block scoped declarations. In that case it is removed from the scope
   // tree and its children are reparented.
   Scope* FinalizeBlockScope();
 
   Zone* zone() const { return zone_; }
 
   // ---------------------------------------------------------------------------
   // Declarations
 
   // Lookup a variable in this scope. Returns the variable or NULL if not found.
-  Variable* LookupLocal(const AstRawString* name);
+  Variable* LookupLocal(const AstRawString* name, bool parameters_only = false);
 
   // This lookup corresponds to a lookup in the "intermediate" scope sitting
   // between this scope and the outer scope. (ECMA-262, 3rd., requires that
   // the name of named function literal is kept in an intermediate scope
   // in between this scope and the next outer scope.)
   Variable* LookupFunctionVar(const AstRawString* name,
                               AstNodeFactory* factory);
 
   // Lookup a variable in this scope or outer scopes.
   // Returns the variable or NULL if not found.
@@ skipping 160 matching lines @@
   bool is_eval_scope() const { return scope_type_ == EVAL_SCOPE; }
   bool is_function_scope() const {
     return scope_type_ == FUNCTION_SCOPE || scope_type_ == ARROW_SCOPE;
   }
   bool is_module_scope() const { return scope_type_ == MODULE_SCOPE; }
   bool is_script_scope() const { return scope_type_ == SCRIPT_SCOPE; }
   bool is_catch_scope() const { return scope_type_ == CATCH_SCOPE; }
   bool is_block_scope() const { return scope_type_ == BLOCK_SCOPE; }
   bool is_with_scope() const { return scope_type_ == WITH_SCOPE; }
   bool is_arrow_scope() const { return scope_type_ == ARROW_SCOPE; }
+  bool is_parameter_scope() const { return scope_type_ == PARAMETER_SCOPE; }
   void tag_as_class_scope() {
     DCHECK(is_block_scope());
     block_scope_is_class_scope_ = true;
   }
   bool is_class_scope() const {
     return is_block_scope() && block_scope_is_class_scope_;
   }
   bool is_declaration_scope() const {
     return is_eval_scope() || is_function_scope() ||
         is_module_scope() || is_script_scope();
@@ skipping 375 matching lines @@
     // * The code is being executed as part of a call to 'eval' and the calling
     //   context chain contains either a variable binding for the name or it
     //   contains a 'with' context.
     DYNAMIC_LOOKUP
   };
 
   // Lookup a variable reference given by name recursively starting with this
   // scope. If the code is executed because of a call to 'eval', the context
   // parameter should be set to the calling context of 'eval'.
   Variable* LookupRecursive(VariableProxy* proxy, BindingKind* binding_kind,
-                            AstNodeFactory* factory);
+                            AstNodeFactory* factory,
+                            bool parameters_only = false);
   MUST_USE_RESULT
   bool ResolveVariable(ParseInfo* info, VariableProxy* proxy,
                        AstNodeFactory* factory);
   MUST_USE_RESULT
   bool ResolveVariablesRecursively(ParseInfo* info, AstNodeFactory* factory);
 
   bool CheckStrongModeDeclaration(VariableProxy* proxy, Variable* var);
 
   // If this scope is a method scope of a class, return the corresponding
   // class variable, otherwise nullptr.
@@ skipping 54 matching lines @@
   PendingCompilationErrorHandler pending_error_handler_;
 
   // For tracking which classes are declared consecutively. Needed for strong
   // mode.
   int class_declaration_group_start_;
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_SCOPES_H_