Swift2: unable to infer closure type in the current context

Question

Created Jun ’15

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In Swift 2 this code generates error:

    private lazy var _keyGenerationController = KeyGeneration(nibName: "KeyGeneration", bundle: nil)

Removing lazy or explicitly annotating the type suppresses this error:

    private var _keyGenerationController = KeyGeneration(nibName: "KeyGeneration", bundle: nil)

or:

    private lazy var _keyGenerationController: KeyGeneration = KeyGeneration(nibName: "KeyGeneration", bundle: nil)

What's happening?

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Answer 1

marchyman OP

Jun ’15

A parsing bug, I think. I ran into it with this code...

final class AppDelegate: NSObject, NSApplicationDelegate, NSWindowDelegate {
   ...
   lazy var preferences: Preferences = Preferences(windowNibName: Preferences.nibName)
   ...
}

If I remove the ": Preferences" thinking that the type will be inferred an error is generated about an unexpected trailing closure.

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Answer 2

QuinceyMorris OP

Jun ’15

I just ran into (apparently) the same problem. This compiled OK:

static var speechSynthesizer = NSSpeechSynthesizer (voice: nil)!

but this gave me the error about inferring the type:

static var speechSynthesizer = {
let result = NSSpeechSynthesizer (voice: nil)!
result.delegate = delegate
return result
} ()

and I had to add the type annotation explicitly.

0

Answer 3

ChrisLattner OP

Jul ’15

Yep, this is a known bug (and often reported) where type inference isn't working properly with lazy properties. Adding the explicit type annotation is the best way to work around this for now.

-Chris

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