Open Radar

 
Summary:
The following code produces an infinite loop, but shouldn't:

Steps to Reproduce:

protocol ModelProtocol {
    var property: String { get }
}

class ConcreteModel: ModelProtocol {
    let property = "I'm a ConcreteModel"
}

class Base {
    var model: ModelProtocol? {
        willSet {
            print("Base.model.willset")
        }
        didSet {
            print("Base.model.didset")
        }
    }
}

class Derived: Base {
    
    override var model: ModelProtocol? {
        willSet {
            print("Derived.model.willset")
        }
        didSet {
            print("entering Derived.model.didset")
            _ = model?.property  // causes an infinite loop in Xcode 7.1
            print("finished Derived.model.didset")
        }
    }
}


let d = Derived()
d.model = ConcreteModel()



Expected Results:
No loop.

Actual Results:
Infinite loop.

WORKAROUND:

            let m = model   // breaks the cycle; no more infinite loop
            _ = m?.property


Version:
10.10.5 (14F1021)

Notes:


Configuration:
Xcode 7.1