The type of s/p there can't be guaranteed to be (S not nil) at compile time, which is a bizarre decision in an otherwise-statically-typed language where the typ

The type of s/p there can't be guaranteed to be (S not nil) at compile time, which is a bizarre decision in an otherwise-statically-typed language where the type system is designed to provide runtime type safety. You still have to do a null check at runtime if you want to be safe here While it's nicer that you can perform the check inside Test() instead of before the call, I don't understand why the type system doesn't just prohibit this and make you use a union type if you want (S or nil) given that a lot more situations call for (S not nil) than (S or nil).