> One initial bit of feedback - I believe if you have existential types, I
> believe you can define Sequence Element directly, rather than with a type
> alias. e.g.
>
> protocol Sequence {
> associatedtype Element
> associatedtype Iterator: any<IteratorProtocol where
> IteratorProtocol.Element==Element>
> associatedtype SubSequence: any<Sequence where Sequence.Element == Element>
> …
> }
That's not really the same thing. Any<IteratorProtocol> is an existential, not
a protocol. It's basically an automatically-generated version of our current
`AnyIterator<T>` type (though with some additional flexibility). It can't
appear on the right side of a `:`, any more than AnyIterator could.
What *would* work is allowing `where` clauses on associated types:
> protocol Sequence {
> associatedtype Element
> associatedtype Iterator: IteratorProtocol where Iterator.Element==Element
> associatedtype SubSequence: Sequence where SubSequence.Element == Element
> …
> }
I believe this is part of the generics manifesto.
--
Brent Royal-Gordon
Architechies
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