Enable Nullable ref types

[hazzik]

I think you need to approve the API difference.

I'm just wondering how did you determine where the types be nullable and where not?

[SimonCropp]

fixed the api

I'm just wondering how did you determine where the types be nullable and where not?

There are a few techniques

• good tests can inform it. since where nulls are passed those parameters must be nullable. where argumentnull exceptions are asserted those parameters are not null
• Optional parameters (where parameter =null) help a lot
• any method that returns a null. then the return value is nullable
• an understanding of the expectations public api can inform u where return values should not be null

Then usually that is enough for the compiler to help you flow those nullables through the rest of the code