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

src/scopes.h

Index: src/scopes.h
diff --git a/src/scopes.h b/src/scopes.h
index 5e3dc1f0654bf65c3ee738665fcb7bf2107be63b..1613b283e5cb3f6e8e25332de33708edb767534a 100644
--- a/src/scopes.h
+++ b/src/scopes.h
@@ -87,7 +87,7 @@ class Scope: public ZoneObject {
   void SetScopeName(const AstRawString* scope_name) {
     scope_name_ = scope_name;
   }
-
+  const AstRawString* scope_name() const { return scope_name_; }
   void Initialize();
 
   // Checks if the block scope is redundant, i.e. it does not contain any
@@ -126,7 +126,7 @@ class Scope: public ZoneObject {
   // 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, bool* is_duplicate);
+                             int pos, 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.
@@ -134,7 +134,10 @@ class Scope: public ZoneObject {
                          InitializationFlag init_flag, Variable::Kind kind,
                          MaybeAssignedFlag maybe_assigned_flag = kNotAssigned,
                          int declaration_group_start = -1);
-
+  Variable* RedeclareLocal(const AstRawString* name, VariableMode mode,
+                           InitializationFlag init_flag, Variable::Kind kind,
+                           MaybeAssignedFlag maybe_assigned_flag = kNotAssigned,
+                           int declaration_group_start = -1);
   // 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
@@ -276,10 +279,15 @@ class Scope: public ZoneObject {
   bool is_function_scope() const {
     return scope_type_ == FUNCTION_SCOPE || scope_type_ == ARROW_SCOPE;
   }
+  bool is_function_body_scope() const {
+    return scope_type_ == FUNCTION_BODY_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_block_scope() const {
+    return scope_type_ == BLOCK_SCOPE || scope_type_ == FUNCTION_BODY_SCOPE;
+  }
   bool is_with_scope() const { return scope_type_ == WITH_SCOPE; }
   bool is_arrow_scope() const { return scope_type_ == ARROW_SCOPE; }
   void tag_as_class_scope() {
@@ -290,8 +298,8 @@ class Scope: public ZoneObject {
     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();
+    return is_eval_scope() || is_function_scope() || is_module_scope() ||
+           is_script_scope() || is_function_body_scope();
   }
   bool is_strict_eval_scope() const {
     return is_eval_scope() && is_strict(language_mode_);
@@ -364,6 +372,10 @@ class Scope: public ZoneObject {
     DCHECK(is_function_scope());
     return params_[index];
   }
+  int parameter_position(int index) const {
+    DCHECK(is_function_scope());
+    return param_positions_[index];
+  }
 
   // Returns the default function arity --- does not include rest parameters.
   int default_function_length() const {
@@ -410,6 +422,9 @@ class Scope: public ZoneObject {
   // The scope immediately surrounding this scope, or NULL.
   Scope* outer_scope() const { return outer_scope_; }
 
+  // The inner scope which contains the main "body" of a function (may be null)
+  Scope* function_body() const { return function_body_; }
+
   // The ModuleDescriptor for this scope; only for module scopes.
   ModuleDescriptor* module() const { return module_descriptor_; }
 
@@ -438,7 +453,6 @@ class Scope: public ZoneObject {
   // Result of variable allocation.
   int num_stack_slots() const { return num_stack_slots_; }
   int num_heap_slots() const { return num_heap_slots_; }
-
   int StackLocalCount() const;
   int ContextLocalCount() const;
 
@@ -521,6 +535,7 @@ class Scope: public ZoneObject {
   // Scope tree.
   Scope* outer_scope_;  // the immediately enclosing outer scope, or NULL
   ZoneList<Scope*> inner_scopes_;  // the immediately enclosed inner scopes
+  Scope* function_body_;           // The scope for a function body
 
   // The scope type.
   ScopeType scope_type_;
@@ -544,6 +559,8 @@ class Scope: public ZoneObject {
   ZoneList<Variable*> temps_;
   // Parameter list in source order.
   ZoneList<Variable*> params_;
+  // List of positions, in source order.
+  ZoneList<int> param_positions_;
   // Variables that must be looked up dynamically.
   DynamicScopePart* dynamics_;
   // Unresolved variables referred to from this scope.