[swift-users] Using ... as a concrete type conforming to protocol ... is not supported

[Hooman Mehr]

You can also get a heterogenous dictionary, but it needs a type erasing helper box. With the following declarations:

public func ==<T: Equatable>(lhs: T, rhs: Any) -> Bool {
    
    if let rhs = rhs as? T { return lhs == rhs } else { return false }
}

public struct AnyKey : Hashable {
    
    public let hashValue: Int
    public let key: Any
    public let equals: (AnyKey) -> Bool
    
    init<T: Hashable>(_ key: T) {
        
        self.hashValue = key.hashValue
        self.key = key
        self.equals = { self.key as! T == $0.key }
    }
}

public func == (lhs: AnyKey, rhs: AnyKey) -> Bool { lhs.equals(rhs) }

You can now create a heterogenous [AnyKey: Any] dictionary. Note that `AnyKey` is not very memory efficient.

> On Mar 25, 2016, at 5:27 PM, Hooman Mehr <hooman at mac.com> wrote:
> 
> 
>> On Mar 25, 2016, at 2:51 PM, Jason Sadler via swift-users <swift-users at swift.org <mailto:swift-users at swift.org>> wrote:
>> 
>> (My particular use case can be seen here: https://gist.github.com/sadlerjw/2cc16b4375b02fe7f400 <https://gist.github.com/sadlerjw/2cc16b4375b02fe7f400> … and the best information I’ve been able to find on this so far is here: http://stackoverflow.com/questions/33112559/protocol-doesnt-conform-to-itself/33524927#33524927 <http://stackoverflow.com/questions/33112559/protocol-doesnt-conform-to-itself/33524927#33524927>)
> 
> Here is the best you can do for your particular use case:
> 
> protocol AnyEquatable { func equals(other: Any) -> Bool }
> 
> func ==<T: Equatable>(lhs: T, rhs: Any) -> Bool {
>     
>     if let rhs = rhs as? T { return lhs == rhs } else { return false }
> }
> 
> extension Bool:   AnyEquatable { func equals(other: Any) -> Bool { return self == other } }
> 
> extension Int:    AnyEquatable { func equals(other: Any) -> Bool { return self == other } }
> 
> extension Double: AnyEquatable { func equals(other: Any) -> Bool { return self == other } }
> 
> extension String: AnyEquatable { func equals(other: Any) -> Bool { return self == other } }
> 
> extension Array {
>     
>     func indexOfAny(element : AnyEquatable) -> Index? { return indexOf { element.equals($0) } }
> }
> 
> var array: [Any] = [false, 1, 2.0, "three"]
> 
> array.indexOfAny(2.0)
> 

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