When a class overrides the equals() method it should also override the hashCode() method. All hash-based collections depend on objects meeting the equals-contract. Two equal objects must produce the same hashcode. When inheriting equals or hashcode, override the inherited and call the super method for clarification.

Noncompliant Code

class Foo {

    override fun equals(other: Any?): Boolean {
        return super.equals(other)
    }
}

Compliant Code

class Foo {

    override fun equals(other: Any?): Boolean {
        return super.equals(other)
    }

    override fun hashCode(): Int {
        return super.hashCode()
    }
}