Is there a way to implement `ZipSequence.Iterator`'s `next()` method from SE-0398

[xAlien95 (Stefano De Carolis)]

From [Pitch] Parameter Packs - #93 by Slava_Pestov

@Slava_Pestov

Unfortunately we don’t support pack expansion expressions in lvalue context (on the left hand side of assignment, or as an argument to an inout parameter) yet.

This means that you can’t actually write a ZipIterator today. Parameter packs will support lvalues, for loops and other features in the fullness of time, which will make them more useful for these kinds of algorithms.