Allowing non-binding pattern matching as a Bool expression?

Evolution Discussion
2

I've wanted similar too. Although it may be better, instead of Bool, to
have it as an optional tuple, the reason I suggest this is so that you can
get the associated type. For example:

case let .Link(value,link) = self

So your example could be written:

func isEmpty() -> Bool {
    return (case .Empty = self) != nil
}

However I'm not sure about this syntax, perhaps something like this:

func isEmpty() -> Bool {
    return self is case .Empty
}

Alternatively if you want the value you could do:

let (value, link) = self as? case .Link

···

On Tue, Dec 8, 2015 at 3:05 PM, Alex Lew via swift-evolution < swift-evolution@swift.org> wrote:

Hi all,

Curious to hear thoughts on allowing non-binding pattern matches to be
used as boolean values outside of an if, guard, for...in, while, switch,
etc. Something like:

enum List<T> {
     case Empty
     indirect case Link(T, List<T>)

     func isEmpty() -> Bool {
          return case .Empty = self
     }
}

It gets rid of some boilerplate (explicit return true and return false),
and seems intuitive that it would work given that you can already do

if case .Empty = self {
     return true
} else {
     return false
}

I haven't really thought through all the implications here, so there's
probably something I'm missing. It also may be useful only in such limited
situations that it's not worth the trouble to add.

-Alex

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