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> On Sep 9, 2017, at 7:33 AM, Brent Royal-Gordon <br...@architechies.com> wrote: > >> On Sep 8, 2017, at 5:14 PM, Xiaodi Wu via swift-evolution >> <swift-evolution@swift.org> wrote: >> >> Here, people just want an array of all cases. Give them an array of all >> cases. When it's not possible (i.e., in the case of cases with associated >> values), don't do it. > > > I agree it should be Int-indexed; that seems to be what people want from this. > > I seem to recall that there is information about the available enum cases in > the module metadata. If so, and if we're willing to lock that in as part of > the ABI design, I think we should write—or at least allow for—a custom > Int-indexed collection, because this may allow us to recurse into associated > value types. If we aren't going to have suitable metadata, though, I agree we > should just use an Array. There are pathological cases where instantiating a > large Array might be burdensome, but sometimes you just have to ignore the > pathological cases. > > (The "infinite recursion" problem with associated values is actually > relatively easy to solve, by the way: Don't allow, or at least don't > generate, `ValuesEnumerable` conformance on enums with `indirect` cases.) This is the direction I think makes the most sense in terms of how we should approach synthesis. The open question in my mind is what the exact requirement of the protocol should be. Should it exactly match what we synthesize (`[Self]` or an associated `Collection where Iterator.Element == Self, Index == Int`) or whether the protocol should have a more relaxed requirement of `Sequence where Iterator.Element == Self` like Tony proposed. > > -- > Brent Royal-Gordon > Architechies >
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