[swift-evolution] [Pitch] Introducing the "Unwrap or Die" operator to the standard library

[Adrian Zubarev]

How about?

public func ?? <T>(optional: T?, noreturnOrError: @autoclosure () throws -> Never) rethrows -> T {
    switch optional {
    case .some(let value):
        return value
    case .none:
        try noreturnOrError()
    }
}


-- 
Adrian Zubarev
Sent with Airmail

Am 27. Juni 2017 um 21:54:57, Max Moiseev via swift-evolution (swift-evolution at swift.org) schrieb:


On Jun 27, 2017, at 10:38 AM, Xiaodi Wu via swift-evolution <swift-evolution at swift.org> wrote:

As you write, this operator becomes sugar for “?? fatalError()” once Never becomes a true bottom type.

In the meantime, can’t the same thing be accomplished by overloading fatalError so it’s a generic function that returns a discardable result of type T, which in turn calls the Never-returning overload?

I like this idea more than adding an extra operator, but overloading fatalError won’t work now because of https://github.com/apple/swift/blob/master/stdlib/public/core/Optional.swift#L668




On Tue, Jun 27, 2017 at 12:25 Erica Sadun via swift-evolution <swift-evolution at swift.org> wrote:
Using an operator to provide feedback on the context of a failed unwrap has become a commonly implemented approach in the Swift developer Community. What are your thoughts about adopting this widely-used operator into the standard library?

guard !lastItem.isEmpty else { return }
let lastItem = array.last !! "Array must be non-empty"

Details here:  https://gist.github.com/erica/423e4b1c63b95c4c90338cdff4939a9b

Thank you for your thoughtful feedback, -- E

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