I am trying to create a generic structure in my project and I am facing an issue where I get the error "Type 'any B' cannot conform to 'A'", where protocol B is derived from protocol A. I don't understand why such a structure is problematic and I would really appreciate any insight or alternative solution for this issue I am having. Issue: I have a general base protocol-class pair like the following. protocol A { } class AClass<T: A> { } To give an example of my use case, protocol A can be PresenterLogic where AClass is BaseInteractor. I have a second protocol-class pair which I want to specialize according to its use case. protocol B: A { } class BClass: AClass<B> { } // Here, I get "Type 'any B' cannot conform to 'A'" For example, protocol B being MyPresenterLogic and class BClass being MyInteractor. Specific Use-Case: To give a more specific use case, I am trying to build a VIP structure such as the following. // Base VIP (Ex: Interactor) protocol PresenterLogic { } class Interactor<PL: PresenterLogic>, BusinessLogic { var presenter: PL? } // VIP for Specific Screen (Ex: Interactor) protocol MyPresenterLogic: PresenterLogic { } class MyInteractor: Interactor<MyPresenterLogic> { // I don't want to declare a second `myPresenter: MyPresenterLogic` here } I don't want to declare another presenter instance in MyInteractor, (such as myPresenter: MyPresenterLogic. I want to be able to use the same presenter instance to be inferred to have the sub-protocol type. That is why I want to use generic classes, but I am stuck. I am searching if this is supported. Any insight is appreciated. Thank you.