static function checkArgOrNull($argName, $argValue)
    {
        if ($argValue === null) return;
        if (!($argValue instanceof self)) Checker::throwError($argName, $argValue, __CLASS__);
    }
static function checkArgOrNull($argName, $argValue)
    {
        if ($argValue === null) return;
        if (!($argValue instanceof self)) Checker::throwError($argName, $argValue, __CLASS__);
    }
static function checkArgOrNull ( $ argName , $ argValue ) { if ( $ argValue === null ) return ; if ( ! ( $ argValue instanceof self ) ) Checker :: throwError ( $ argName , $ argValue , __CLASS__ ) ; }
Use this to check that a function argument is either `null` or of type
`AppInfo`.

@internal
Use this to check that a function argument is either null or of type AppInfo .