V3211. Unity Engine. The operators '?.', '??' and '??=' do not correctly handle destroyed objects derived from 'UnityEngine.Object'.

The analyzer has detected a potential error related to the object derived from UnityEngine.Object. This object was used with the null-conditional (?.) or null-coalescing (?? and ??= ) operator.

According to the Unity documentation, it is not recommended to use the ?., ??, and ??= operators. They cannot be overloaded, so they do not consider that objects derived from UnityEngine.Object may be destroyed. Therefore, the check may have an incorrect result.

Look at the example:

class CustomComponent: MonoBehaviour
{
  public bool HitConfirm(....)
  {  
    Projectile bullet;
    ....
    if(....)
      Destroy(bullet);
    ....
    if(bullet?.isJammed())
    {....}
  }
}

When addressing bullet, the check with a null-conditional operator (?. ) will not consider that the object may be destroyed, since this operator cannot be overloaded.

To fix this, it is recommended to use a check with the == or != operator.

The fixed code:

class CustomComponent: MonoBehaviour
{
  public bool HitConfirm(....)
  {  
    Projectile bullet;
    ....
    if(....)
      Destroy(bullet);
    ....
    if(bullet != null ? bullet.isJammed() : null)
    {....}
  }
}

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