> On Nov 20, 2017, at 5:43 PM, Chris Lattner via swift-evolution > <swift-evolution@swift.org> wrote: > > >> On Nov 20, 2017, at 5:39 PM, Kelvin Ma via swift-evolution >> <swift-evolution@swift.org <mailto:swift-evolution@swift.org>> wrote: >> >> when SE-185 >> <https://github.com/apple/swift-evolution/blob/master/proposals/0185-synthesize-equatable-hashable.md> >> went through swift evolution, it was agreed that the next logical step >> <https://www.mail-archive.com/swift-evolution@swift.org/msg26162.html> is >> synthesizing these conformances for tuple types, though it was left out of >> the original proposal to avoid mission creep. I think now is the time to >> start thinking about this. i’m also tacking on Comparable to the other two >> protocols because there is precedent in the language from SE-15 >> <https://github.com/apple/swift-evolution/blob/master/proposals/0015-tuple-comparison-operators.md> >> that tuple comparison is something that makes sense to write. >> >> EHC conformance is even more important for tuples than it is for structs >> because tuples effectively have no workaround whereas in structs, you could >> just manually implement the conformance. > > In my opinion, you’re approaching this from the wrong direction. The > fundamental problem here is that tuples can’t conform to a protocol. If they > could, synthesizing these conformances would be straight-forward.
It would be a tractable intermediate problem to introduce built-in conformances for tuples (and perhaps metatypes) to Equatable/Hashable/Comparable without breaching the more general topic of allowing these types to have general protocol conformances. I think that would cover the highest-value use cases. -Joe
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