bug.swift

protocol SomeProtocol {
    var a: Int { get }
}

struct SomeStruct: SomeProtocol {
    var a = 0
}

class SomeClass {
    var value: SomeProtocol = SomeStruct() {
        didSet { print("Setter called.") }
    }

    func doSomething() {
        print("About to do something")
        _ = self.value.a
        print("Did something")
    }
}

SomeClass().doSomething()

// Output:
//
// About to do something
// Setter called.
// Did something