Open Radar

 
The Swift compiler is easily confused into thinking that a property is not set in an initializer by the time that the initializer returns. For instance:

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import Foundation

struct Row {
    let a: String = "example"
    let b: String
    let c: String?
}

extension Row {
    init(csv string: String) {
        var didSetB = false
        for (idx, part) in enumerate(string.componentsSeparatedByString(",")) {
            switch idx {
            case 0: self.a = part
            case 1: self.b = part; didSetB = true
            case 2: self.c = part
            default: break
            }
        }
        if !didSetB {
            self.b = "(unknown)"
        }
    }
}

println(Row(csv: "wind,sea,kite"))

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The Swift compiler reports an error "Variable self.b used before being initialized" at the end of the init(). But clearly there is no possible control flow where `self.b` will not have a value.