functioning of covariant in flutter

Question

I was going through dart documentation and there I came across this code and this term covariant. I went through some documentation but I didn't get what is its function there. A detailed explained answer is always appreciated.

class Animal {
  void chase(Animal x) { ... }
}

class Mouse extends Animal { ... }

class Cat extends Animal {
  @override
  void chase(covariant Mouse x) { ... }
}

Answer 1

By using the covariant keyword, you disable the type-check and take responsibility for ensuring that you do not violate the contract in practice.

As you can see in the example, if you are overriding a method, its params should also be the same. But if you are using covariant, it will allow you to use Mouse instead of Animal.