Open Radar

 
Summary:
In general, Swift can infer the types of parameters in closures when the function type is known. However, when the parameters are inout, it is necessary to explicitly specify those types.

Swift should be able to infer the types of these parameters.

Steps to Reproduce:
Enter this into a playground:

    let mySwap: (inout Int, inout Int) -> () = { a, b in
        (a, b) = (b, a)
    }
    
    var x = 1
    var y = 2

    mySwap(&x, &y)

    print("x = \(x), y = \(y)")

Expected Results:
Swift should be able to infer that the types of a and b in the closure are "inout Int".

Actual Results:
Compiler reports: error: '(_, _) -> ()' is not convertible to '(inout Int, inout Int) -> ()'
    (a, b) = (b, a)

To get it to compile, one must provide full explicit type annotations for the closure arguments, like this:

    let mySwap: (inout Int, inout Int) -> () = { (inout a: Int, inout b: Int) in
        (a, b) = (b, a)
    }


Version:
Xcode Version 7.0 beta (7A121l)