[swift-evolution] [Accepted] SE-0115: Rename Literal Syntax Protocols

David Sweeris davesweeris at mac.com
Mon Jul 11 21:22:10 CDT 2016

> On Jul 11, 2016, at 7:34 PM, Jacob Bandes-Storch <jtbandes at gmail.com> wrote:
> I'd call it an antipattern: it pretty much defeats the purpose of having the ExpressibleBy*Literal protocols.
> If you just want a type to be constructible from a value of some other type (literal or not), that's what regular initializers are for. For example, in addition to its ArrayLiteralConvertible conformance, Set provides init<S: Sequence where S.Iterator.Element == Element>(_ seq: S), so you can write Set([1, 2, 3]). The literal protocols are different because they're invoked *implicitly*: doSomethingWithASet([1, 2, 3]).
> They're also awkward, because the argument labels (integerLiteral:, arrayLiteral:, nilLiteral:) provide only type information, and not "role" information — and if you're invoking one of these inits explicitly, there's no way the compiler can enforce that you're actually passing a *literal* in for those parameters (in fact, you *can't* pass an array literal to init(arrayLiteral:), because it's a variadic parameter rather than an array parameter).

Agreed... I don’t see the harm in letting someone use them if they want to.

To be clear, I’m only pointing out that, IMHO, there’s not really a need to do the work of specifically disallowing this “antipattern”. If others think it’s important enough to bother with, I won’t complain. If we weren’t in the Swift 3 crunch, I might not have raised it at all.

- Dave Sweeris

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