code: function parseSwitchType(lex) {
      var start = lex.accept('switchtype');
      if (!start) {
          return null;
      }
  
      var expr = parseExpression(lex);
      lex.assert('{');
  
      var cases = [];
      var end;
      do {
          let c = parseSwitchTypeCase(lex);
          cases.push(c);
      } while (!(end = lex.accept('}')));
  
      return new nodes.SwitchTypeNode(expr, cases, start.start, end.end);
  }
docs: Parses a `switchtype` statement
  @param  {Lexer} lex
  @return {SwitchType}