Using type check instead of equality check for objects inside `when` expression

Support
1

We can can make an equality check instead of a type check for objects inside when expressions, e.g.:

sealed interface Test {
    object A : Test
    class B(f: Int) : Test
}
...
...
when (x) {
        Test.A -> ...
        is Test.B -> ...
    }

But it would really look better if all branches inside when would use type check (if one of them is a class):

when (x) {
        is Test.A -> ...
        is Test.B -> ...
    }

As I can see in bytecode, the equality check leads us to Intrinsics.areEqual → and it leads us to the object’s generated equals() → and it makes instanceOf (among other generated operations).
Type check also invokes same instanceOf operation.

My question is: is it a good practice to use type checks on all branches inside when? Are there any disadvantages?

2

Feel free to focus on readability, IMHO.

3

I think the disadvantage would probably be a performance hit. I imagine the is check has to do some kind of reflective comparison or something? Where as the first check would be an equality operation, which is just “do these two pointers point to the same place in memory?” The real question is, how much of a performance hit is it to do is, and do you care? I would guess you probably don’t care about the performance hit; most JVM applications are not CPU-bound, but IO-bound.