Open Radar

 
Summary:
The compiler does not allow me to use a generic function of the form:
func myFunction<T>() -> Void {}

Steps to Reproduce:
1. Write a function of above form:
  func myFunction<T>() -> Void {}
2. Call it:
  myFunction<MyObject>()
3. Compile it

OR

Just execute the attached code in a playground :)

Expected Results:
It compiles without issues

Actual Results:
Error: Cannot explicitly specialize a generic function

Version:
Xcode 6.3
swift 1.2

Notes:
Same error on swift1.1
- Not only me:

http://stackoverflow.com/questions/27965439/cannot-explicitly-specialize-a-generic-function

http://stackoverflow.com/questions/28726937/how-do-i-call-a-generic-swift-function-when-none-of-the-arguments-provides-the-g

https://twitter.com/dangerdave/status/490385202170982401


Attached code:



import Foundation

protocol Registrable: NSObjectProtocol {
    static func registerIfNeeded()
    static func unregister()
    init()
}

class Something: NSObject, Registrable {
    static func registerIfNeeded() {
    }
    static func unregister() {
    }
    override required init() {
    }
}

func doMyThing<T: Registrable>(whatever: Int) {
    // Before doing my stuff I make sure the class is registered
    T.registerIfNeeded()
    // Now I can do my thing
    var t = T()
}

//: No way the compiler can know about `Something` unless it is passed explicitly. However it does not work explicitly too: **ERROR** ***Cannot explicitly specialize a generic function***

doMyThing<Something>(123)

func doMyThing2<T: Registrable>(index: Int) -> T {
    T.registerIfNeeded()
    var t = T()
    return t
}

doMyThing2(123) as Something // This works because the compiler got a hint