Why must constructing an object of class type 'someClass' with a metatype value use a 'required' initializer?

Question

class Animal {
    class func generate() -> Animal {
        return self()
    }
}

The compiler complains constructing an object of class ty

Answer 1

Consider the case where we also have a subclass:

class SomeClass {

}

class SomeSubclass : SomeClass {

}

If you store the class type in a variable:

var anotherClass = SomeClass.self

The variable anotherClass is of type SomeClass.Type.

You can later assign this variable to a subclass:

anotherClass = SomeSubclass.self

This is valid because SomeSubclass.Type is a SomeClass.Type. At this point, anotherClass() would fail if the initializer is not implemented in the subclass. This is what the compiler is protecting against.

In your sample code, this is impossible: you used let instead of var so changing the type is impossible. It may be that the safety checks just aren't nuanced enough to notice this.