Why can't Swift automatically generate a memberwise initializer for classes?

Unlike structures, classes support inheritance. A class can have a superclass with its own properties and initializers. An automatic memberwise initializer for a class would need to account for the properties of all superclasses in the inheritance hierarchy, which significantly complicates things and can lead to ambiguities.

Additionally, classes have the ability to define deinitializers (deinit) and can include more complex initialization logic, such as setting up object lifecycle, resource management, or handling side effects, which is not reflected in simple property value passing through a memberwise initializer. Developers must explicitly define how class instances are initialized, including calls to superclass initializers and executing necessary logic.

class BaseClass {
    var baseValue: Int

    init(baseValue: Int) {
        self.baseValue = baseValue
    }
}

class DerivedClass: BaseClass {
    var derivedValue: String

    // Explicit initializer definition is required
    init(baseValue: Int, derivedValue: String) {
        self.derivedValue = derivedValue
        // Call to superclass initializer
        super.init(baseValue: baseValue)
    }
}