A tuple of the lower and upper bounds of the range.
Because this initializer does not perform any checks, it should be used as an optimization only when you are absolutely certain that lower is less than or equal to upper. Using the closed range operator (...) to form ClosedRange instances is preferred.
Call body(p), where p is a pointer to the collection’s contiguous storage. If no such storage exists, it is first created. If the collection does not support an internal representation in a form of contiguous storage, body is not called and nil is returned.
Available when Bound conforms to Strideable and Bound.Stride conforms to SignedInteger.