code: func builtinDate(args []types.Datum, ctx context.Context) (types.Datum, error) {
  	return convertToTime(ctx.GetSessionVars().StmtCtx, args[0], mysql.TypeDate)
  }
docs: // See https://dev.mysql.com/doc/refman/5.7/en/date-and-time-functions.html#function_date