Assigning members of ICollection types with collection initializers can provably cause NullReferenceExceptions

[Will-Boulton]

Assigning members of ICollection types with collection initializers can provably cause NullReferenceExceptions

[CyrusNajmabadi]

In this scenario CS8670 as a warning is insufficient as it is provable* that the member is not just possibly null, but rather it has to be null

There is no such concept in the language or compiler. All we have is "believed to be not null" and "believed to be possibly null", there is no "has to be null". As such, we just warn. This was an explicit decision at the language level as analysis to be certain something is certainly null is too expensive and costly (both in terms of design and impl) to be felt to be worthwhile.

[CyrusNajmabadi]

Note: this is clearly evident even when doing simple things like X x = null; /*nothing intervening*/ x.. Even in these trivial cases, we warn instead of error.

Closing out as by design. @jaredpar let me know if you disagree with that assessment.

[Will-Boulton]

Thanks @CyrusNajmabadi, I thought that may be the case!

[CyrusNajmabadi]

yw :)