I also wonder to what extent enums can be used for algebraic data types.

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Ugh, looks like you can't recurse in enums.

    enum Tree {
        case Empty
        case Leaf(Int)
        case Node(Tree, Tree)
    }

kills the REPL with a `Bus error: 10`.

----
This works (as is but not sure if it would work once we start adding other things):

    protocol TreeLike {}
    enum Tree:TreeLike {
        case Empty
        case Leaf(Int)
        case Node(TreeLike, TreeLike)
    }


----
    Tree.Node(Tree.Node(Tree.Leaf(1), Tree.Leaf(2)), Tree.Leaf(3))

work with the above definition of `Tree`.

----
Of course that's fixed to being a Tree of Ints.

    enum Tree<T>:TreeLike {
        case Empty
        case Leaf(T)
        case Node(TreeLike, TreeLike)
    }

which kills the REPL with:

    LLVM ERROR: unimplemented IRGen feature! non-fixed multi-payload enum layout
    Assertion failed: (err == 0), function ~Mutex, file /SourceCache/lldb_KLONDIKE/lldb_KLONDIKE-320.3.100/source/Host/common/Mutex.cpp, line 246.
    Abort trap: 6

And TreeLike isn't even the suitable generic.

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The fact these things actually error gives me hope that they're just bugs not intentional limitations of the language.

----
brosner found this:

<blockquote class="twitter-tweet" lang="en"><p><a href="https://twitter.com/jopamer">@jopamer</a> Hey, Swift looks really nice - wondering if enums can have recursive defs: enum Tree&lt;T&gt;{case Leaf(T); case Node(Tree&lt;T&gt;, Tree&lt;T&gt;)}?</p>&mdash; Carlos Scheidegger (@scheidegger) <a href="https://twitter.com/scheidegger/statuses/473586585737654273">June 2, 2014</a></blockquote>

<blockquote class="twitter-tweet" lang="en"><p><a href="https://twitter.com/scheidegger">@scheidegger</a> Thanks, Carlos! Not quite yet, but only because of a bug. I&#39;m currently tracking it, and I&#39;ll look into addressing it soon</p>&mdash; Joe Pamer (@jopamer) <a href="https://twitter.com/jopamer/statuses/473590251168874496">June 2, 2014</a></blockquote>


----
Looks like Beta 3 still doesn't support recursive enums :-(

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Beta 4 still doesn't support recursive enums!

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Sorry to say, Beta 5 *still* doesn't support recursive enums!!

Unless

```
enum Tree {
    case Empty
    case Leaf(Int)
    case Node(Tree, Tree)
}
```

isn't the right way to do it.

But the above continues to crash the REPL.

----
Swift 1.1 still doesn't support

`enum Tree<T>{case Leaf(T); case Node(Tree<T>, Tree<T>)}`

despite claims it was just a "bug" preventing it.