[swift-evolution] [Proposal draff] abstract classes and methods

[Brent Royal-Gordon]

> Not if you can’t figure out how to write the protocol such that it doesn’t refer to Self, have typealiases, or do something else that means you can only use it as a generic constraint rather than an actual type.

As abstract classes also cannot use Self the way protocols can or have associated types, I'm not certain what an abstract class could express that an existential protocol couldn't.

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Brent Royal-Gordon
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