code: private ParseTree parseForOfStatement(
        SourcePosition start, ParseTree initializer) {
      eatPredefinedString(PredefinedName.OF);
      ParseTree collection = parseExpression();
      eat(TokenType.CLOSE_PAREN);
      ParseTree body = parseStatement();
      return new ForOfStatementTree(
          getTreeLocation(start), initializer, collection, body);
    }
docs: for  (  { let | var }?  identifier  of  expression  )  statement