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Constrained existential types

Available from Swift 5.7

Paul Hudson      @twostraws

SE-0353 provides the ability to compose SE-0309 (“Unlock existentials for all protocols”) and SE-0346 (“Lightweight same-type requirements for primary associated types”) to write code such as any Sequence<String>.

It’s a huge feature in its own right, but once you understand the component parts hopefully you can see how it all fits together!

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