scala 类型系统 - 了解具有下限/上限的协变

Question

I am new to scala and have questions on scala generics

Question is how animalContainer.add method is accepting new Cat. From my understanding B>:A - A is Animal and B is Cat. Cat is NOT super typs of animal . How it is working..

Answer 1

B is not Cat, B is Animal. The inferred type of add is then effectively:

def add(element: Animal)

You are able to pass Cat here because Cat extends Animal.