I suggest that `object` types automatically satisf...

# language-proposals

[Marc Knaup]

I suggest that object types automatically satisfy equals and hashCode requirements of an interface/superclass.
object types are typically equal to themselves and have a hash code based on their instance automatically which is sufficient.
I can only think of very very few exceptions where you would want an object to not be equal to itself or have some custom implementation 🤔

interface Foo {
    override fun equals(other: Any?): Boolean
    override fun hashCode(): Int
}

data class Bar1(val bar: Int) : Foo // fine
object Bar2 : Foo // error because equals() and hashCode() are missing

I’m often using explicit abstract equals and hashCode to not forget to provide an implementation in implementing types. Typically I use data class or object but it’s too easy to forget the data.

[georg]

Would be great if not everything would inherit from Object implicitly anyway. Like in Swift where you need to explicitly conform to the Equatable and Hashable protocols. But I guess that’s inevitable if you live on the JVM

[Marc Knaup]

Yeah and you’d probably need support for Self types.

[louiscad]

Well, the default toString for object is already correct…

[MiSikora]

What is a correct implementation of hashCode for an object?

[Marc Knaup]

The default one of java.lang.Object is sufficient.
Or literally any static one 🙂