Just throwing this out there, does anyone think it would be a good idea to include such a function in std-lib:

inline infix fun Any?.hash(other: Any?): Int = hashCode() * 31 + other.hashCode()

It would simplify writing

hashCode

functions:

class ABC<A, B, C>(val a: A, val b: B, val c: C) {
    override fun hashCode() = a hash b hash c
}

I like the idea, but I’m not sure if this will be used. In my experience 95% of

hashCode

functions I use are from data classes. Also with a good IDE you will just auto generate the

hashCode

function in any case.

That's fair (I disagree about the 95%, but that's probably pretty domain specific)

Any particular reason you dont use

Objects.hash

?

Overhead, it creates a temporary array.

I would be surprised if varargs arent heavily optimised on both the jvm and js

Yes, thus my first comment

Ah sorry. It was collapsed here.

One more argument for doing this is that data classes are effectively useless for library APIs: https://jakewharton.com/public-api-challenges-in-kotlin/

You can work around the problem with the

copy

function by providing a custom copy function that calls the generated one, you just need to annotate it with

@Deprecated("", level = DeprecationLevel.HIDDEN)

. I don’t know a workaround for

componentN

except for only adding new properties to the end. That said, I don’t like the fact that kotlin adds

componentN

functions to all data classes automatically. Since they aren’t named, they just pose to much of a risk IMO. Especially when the data class is provided by a library.