> On May 13, 2016, at 8:18 AM, Matthew Johnson <[email protected]> wrote: > > When I write a class Base with non-final methods that return instances of > Base I can choose whether to state the return type as Self (covariant) or > Base (invariant, under this proposal StaticSelf would also be an alternative > way to state this). If I choose to specify Base as the return type derived > classes *may* override the method but are not required to. Further, if they > *do* override the method they are allowed to choose whether their > implementation returns Base or Derived.
`StaticSelf` requirements by themselves don't even save you from covariance. If Base conforms to a protocol (with Self == Base), Derived inherits that conformance and also conforms (with Self == Derived). If `StaticSelf` always refers to the conforming type, then it must also be bindable to Base and Derived, so a base class must still use a covariant-returning method to satisfy the `StaticSelf` requirement. -Joe _______________________________________________ swift-evolution mailing list [email protected] https://lists.swift.org/mailman/listinfo/swift-evolution
