I think you're after "associated types". developer.apple.com/library/ios/do Gist: gist.github.com/kongtomorrow/7
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That requires making a 1-to-1 relationship between each `Smashable`-adopter and each `Value`-adopter
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Does that permit Brent’s use case, where it accepts one Value but returns a different one?
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I’m looking at your original one. How can valueBySmashing… take a Foo and return a Bar?
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It couldn’t without the <T, U> formulation from my comment. Didn’t see that he needed that. Updated.
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This doesn't work — but I'm not sure why it doesn't work.
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in this, U is determined by the caller and can be anything. But impl always returns Bar.
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Yep. Okay. No way to fix this without making Value hetero-equatable, as said. :(
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In other words, falling back to guard let x = x as Value else { abort }?
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No, adding isEqual(Value) to Value instead of “: Equatable".
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Yeah, really want protocol *type* to be Equatable, but can't do that yet.
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What if Value was an enum with associated values, not protocol?
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