[es6] implement default/optional parameters (WIP / comments)

src/parser.cc

Index: src/parser.cc
diff --git a/src/parser.cc b/src/parser.cc
index fc4138d18621260079dc4a5b7263e68155b1982a..e8a0180e67043a3ee3c8b83a2c02090f56f40c26 100644
--- a/src/parser.cc
+++ b/src/parser.cc
@@ -373,10 +373,12 @@ FunctionLiteral* Parser::DefaultConstructor(bool call_super, Scope* scope,
     handler_count = function_state.handler_count();
   }
 
+  ZoneList<Expression*>* default_values =
+      new (zone()) ZoneList<Expression*>(0, zone());
   FunctionLiteral* function_literal = factory()->NewFunctionLiteral(
       name, ast_value_factory(), function_scope, body,
       materialized_literal_count, expected_property_count, handler_count,
-      parameter_count, FunctionLiteral::kNoDuplicateParameters,
+      parameter_count, default_values, FunctionLiteral::kNoDuplicateParameters,
       FunctionLiteral::ANONYMOUS_EXPRESSION, FunctionLiteral::kIsFunction,
       FunctionLiteral::kNotParenthesized, kind, pos);
 
@@ -1036,11 +1038,13 @@ FunctionLiteral* Parser::DoParseProgram(ParseInfo* info, Scope** scope,
     }
 
     if (ok) {
+      ZoneList<Expression*>* default_values =
+          new (zone()) ZoneList<Expression*>(0, zone());
       result = factory()->NewFunctionLiteral(
           ast_value_factory()->empty_string(), ast_value_factory(), scope_,
           body, function_state.materialized_literal_count(),
           function_state.expected_property_count(),
-          function_state.handler_count(), 0,
+          function_state.handler_count(), 0, default_values,
           FunctionLiteral::kNoDuplicateParameters,
           FunctionLiteral::ANONYMOUS_EXPRESSION, FunctionLiteral::kGlobalOrEval,
           FunctionLiteral::kNotParenthesized, FunctionKind::kNormalFunction, 0);
@@ -3840,6 +3844,9 @@ FunctionLiteral* Parser::ParseFunctionLiteral(
   FunctionLiteral::IsParenthesizedFlag parenthesized = parenthesized_function_
       ? FunctionLiteral::kIsParenthesized
       : FunctionLiteral::kNotParenthesized;
+
+  ZoneList<Expression*>* default_params = new (zone()) ZoneList<Expression*>(0, zone());
+
   // Parse function body.
   {
     AstNodeFactory function_factory(ast_value_factory());
@@ -3879,9 +3886,14 @@ FunctionLiteral* Parser::ParseFunctionLiteral(
          arity_restriction != FunctionLiteral::SETTER_ARITY);
     while (!done) {
       bool is_strict_reserved = false;
-      is_rest = peek() == Token::ELLIPSIS && allow_harmony_rest_params();
-      if (is_rest) {
+      int rest_pos;
+
+      ParameterKind kind = ParameterKind::Normal;
+
+      if (peek() == Token::ELLIPSIS && allow_harmony_rest_params()) {
         Consume(Token::ELLIPSIS);
+        rest_pos = position();
+        kind = ParameterKind::Rest;
       }
 
       const AstRawString* param_name =
@@ -3900,7 +3912,27 @@ FunctionLiteral* Parser::ParseFunctionLiteral(
         dupe_error_loc = scanner()->location();
       }
 
-      Variable* var = scope_->DeclareParameter(param_name, VAR, is_rest);
+
+
+      if (peek() == Token::ASSIGN) {
+        // Default parameters:
+        Consume(Token::ASSIGN);
+        static const bool accept_IN = true;
+        Expression* defaultValue =
+            ParseAssignmentExpression(accept_IN, CHECK_OK);
+        if (kind.isRestParameter()) {
+          ReportMessageAt(
+              Scanner::Location(rest_pos, scanner()->location().end_pos),
+              "rest_param_default");
+          *ok = false;
+          return nullptr;
+        }
+        kind = ParameterKind::Optional;
+        default_params->Add(defaultValue, zone());
+      }
+
+      Variable* var = scope_->DeclareParameter(param_name, VAR, kind);
+
       if (is_sloppy(scope->language_mode())) {
         // TODO(sigurds) Mark every parameter as maybe assigned. This is a
         // conservative approximation necessary to account for parameters
@@ -4032,7 +4064,7 @@ FunctionLiteral* Parser::ParseFunctionLiteral(
   FunctionLiteral* function_literal = factory()->NewFunctionLiteral(
       function_name, ast_value_factory(), scope, body,
       materialized_literal_count, expected_property_count, handler_count,
-      num_parameters, duplicate_parameters, function_type,
+      num_parameters, default_params, duplicate_parameters, function_type,
       FunctionLiteral::kIsFunction, parenthesized, kind, pos);
   function_literal->set_function_token_position(function_token_pos);