> On Jun 2, 2016, at 9:52 AM, Sean Heber via swift-evolution > <[email protected]> wrote: > > In terms of naming, I almost feel like “None” would be a better name for it > as then it reads somewhat as the opposite of “Any” and that has a nice > symmetry to me.
+ 1. Although the inverse of “None” is really “All” (as in “all or none”). I’m not necessarily suggesting we use “All”, just pointing out the linguistic relationship. That said, I do believe we should *consider* alternatives names for “Any” as part of the discussion of the name for a bottom type. It would be nice symmetry if we found names for the top and bottom types that are inverses of each other. > > l8r > Sean > > >> On Jun 2, 2016, at 4:04 AM, Brent Royal-Gordon via swift-evolution >> <[email protected]> wrote: >> >>> 1) For noreturn, the core team prefers to explore a solution where a >>> function can be declared as returning an non-constructable “bottom” type >>> (e.g. an enum with zero cases). This would lead to something like: >>> >>> func abort() -> NoReturn { … } >>> >>> This will require some new support in the compiler, but should flow better >>> through the type system than @noreturn in function composition and other >>> applications. Joe Groff offered to write a proposal for this. >> >> Are you thinking in terms of a *real* bottom type—that is, a type which is >> the subtype of all types—or a fake bottom type which is simply an empty enum? >> >> If you're thinking about a real bottom type, I wouldn't want to call it >> `NoReturn`, because the bottom type may end up playing a larger role in the >> language. Given our use of `Any`, the natural names for a bottom type are >> probably `All` (as the subtype of all types) or `None` (as a type with no >> instances). I do worry that those names are a little too short and >> attractive, though. `None` might be mistaken for `Void`; `All` might be >> mistaken for `Any`, and wouldn't make much sense when read as the return >> value of a function. >> >> My best suggestion is `Never`. A function with a `Never` return type would >> read as "never returns": >> >> func abort() -> Never { … } >> >> If it appeared in, say, a generic type, it would mean "never occurs": >> >> let result: Result<String, Never> >> >> Flowing from that, we can end up with functions taking a `Never` parameter, >> which are never called: >> >> result.flatMapError { (_: Never) in fatalError("can't happen") } >> >> Or `Never?` values, which are never `some`: >> >> let _: Never? = Result<String, Never>.error >> >> (By the way, the return type of the force unwrap operator on a `Never?` is >> `Never`, which is just right: if you force unwrap a `Never?`, it will always >> trap, never return.) >> >> The main issue I see with `Never` is that it's an adverb, not a noun. But >> the nouns all seem to have problems. And besides, the bottom type isn't so >> much a thing as a lack of a thing, isn't it? That's bound to have a slightly >> funky name. >> >> -- >> Brent Royal-Gordon >> Architechies >> >> _______________________________________________ >> swift-evolution mailing list >> [email protected] >> https://lists.swift.org/mailman/listinfo/swift-evolution > > _______________________________________________ > swift-evolution mailing list > [email protected] > https://lists.swift.org/mailman/listinfo/swift-evolution _______________________________________________ swift-evolution mailing list [email protected] https://lists.swift.org/mailman/listinfo/swift-evolution
