Swift: Self.init called multiple times in initializer

Question

This one has me stumped. I can't figure out why Swift is complaining that self.init is called more than once in this code: ``` public init(body: String) { let parser = Gravl.Parser() if let node = parser.parse(body) { super.init(document: self, gravlNode: node) } else { // Swift complains with the mentioned error on this line (it doesn't matter what "whatever" is): super.init(document: self, gravlNode: whatever) } } ``` Unless I'm missing something, it's very obvious that it is only calling `init` once. Funnily enough if I comment out the second line Swift complains that Super.init isn't called on all paths, lol. What am I missing? Update: Ok so the problem was definitely trying to pass `self` in the call to super.init. I totally forgot I was doing that, ha. I think I had written that experimentally and gotten it to compile and thought that it might actually work, but looks like it's actually a bug that it compiled that way at all. Anyhow, since passing `self` to an initializer is kin…

Accepted Answer

I suspect this is a bad diagnostic (i.e the wrong error message). It would be very helpful if you had a full example we could experiment with, but this line doesn't make sense (and I suspect is the underlying problem):

```
    super.init(document: self, gravlNode: node)
```

You can't pass `self` to `super.init`. You're not initialized yet (you're not initialized until you've called `super.init`). For example, consider the following simplified code:

```
class S {
    init(document: AnyObject) {}
}

class C: S {
    public init() {
        super.init(document: self)
    }
}
```

This leads to `error: 'self' used before super.init call` which I believe is the correct error.

EDIT: I believe Hamish has definitely uncovered a compiler bug. You can exploit it this way in Xcode 8.3.1 (haven't tested on 8.3.2 yet):

```
class S {
    var x: Int
    init(document: S) {
        self.x = document.x
    }
}

class C: S {
    public init() {
        super.init(document: self)
    }
}

let c = C() // malloc: *** error for object 0x600000031244: Invalid pointer dequeued from free list
```

Swift: Self.init called multiple times in initializer

Solution

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