Protocol extension triggers segfault

Question

Created Aug ’15

Replies 3

Boosts 0

Participants 3

I haven't seen this specific pattern of protocol extension elsewhere, but it works in a playground and does what I need it to do — extending one protocol to provide an implementation of another protocol it inherits with typealias requirements. Simple example:

protocol TreeNode: SequenceType {
    var children: Array<Self> { get set }
}
extension SequenceType where Self: TreeNode, Generator == AnyGenerator<Self> {
    func generate() -> Generator {
        return anyGenerator(children.generate())
    }
}

Issue comes when it's dropped into a project. If it's the only thing in the project, it'll compile fine. However, I can drop seemingly innocuous code (not in any way interacting with the above) into another file and the project segfaults on compile.

Example of innocuous code for another file:

struct IntWrapper {
    let anInt: Int = 0
}

This compiles fine without the presence of the above.

Better way to accomplish the same? Suggestions for troubleshooting the segfault?

Boost

Answer 1

SevenTenEleven OP

Aug ’15

I think we just haven't implemented this properly yet—even if it compiles in one file, it may not work correctly at runtime. Please file a bug.

0

Answer 2

cmgiven OP

Aug ’15

rdar://22093958

Thanks.

0

Answer 3

ObjectHub OP

Aug ’15

I can't reproduce this with XCode 7 Beta 5.

What I would like to understand is why you're choosing to extend `SequenceType`. Wouldn't it be much simpler if the `generate` method was added via an extension of `TreeNode`?

extension TreeNode where Generator == AnyGenerator<Self> {
  func generate() -> Generator {
    return anyGenerator(children.generate())
  }
}

0