RXTuple should be an NSArray subclass

[robrix]

There’s little if any impedance mismatch, and it would be more intention-revealing.

This would obviate the need for -allObjects to return an array that can contain nil. (Indeed, it would obviate the need for -allObjects to exist at all.)

[robrix]

Counterpoint: -hash is implemented incompatibly by RXTuple, and the invariant is that -hash may not produce different values for equal objects.

We can say that a tuple will return NO for -isEqual: when passed an arbitrary non-RXTuple array as its parameter, which holds the invariant, but we cannot say that NSArray will return NO for -isEqual: when passed an arbitrary tuple as its parameter, if that tuple contains the same objects.