I'm not sure memberless composition is the correct term for this but it is when you compose a new type by composition and the new gets all new members without any new scope. The goal is that the new type should appear to have the same functionality as the you are composing from. Example of this is for example UnsafePointer where you have to use the pointee member to get to the actual instance. How about you could make UnsafePointer behaving like the actual type T without the pointee dereference.
This currently possible by inheritance in Swift but limited to classes and only one class. In C++ it also possible but there you have multiple inheritance and no difference between classes and structs. Also another common solution is to override the -> operator, which you often is in iterators. Not really composition but you get similar functionality. D offers two ways of doing this and that is with "alias this" alternatively with template mixins.
Is there a way to do this in Swift? Keep in mind that I want to avoid involving protocols because of the extra baggage.