@optics generates bad code for sealed hierarchies with changing property nullability

[sindrenm]

The Arrow Optics KSP plugin generates bad code for sealed hierarchies that contains nullable properties in the parent, but that becomes non-nullable in a child class.

This is a new issue with arrow-optics 1.2.2 that was not present in 1.1.5.

Library: io.arrow-kt:arrow-optics-ksp-plugin 1.2.2

Reproduction

The following will generate code that does not compile in arrow-optics 1.2.2:

import arrow.optics.optics

@optics
sealed interface Base {
    val prop: String?

    companion object
}

@optics
data class Child(override val prop: String) : Base {
    companion object
}

The generated bad code:

inline val Base.Companion.nullableProp: Lens<Base, String?>
    inline get() = Lens(
        get = { base: Base -> base.`prop` },
        set = { base: Base, value: String? ->
            when (base) {
                is Child -> base.copy(`prop` = value) // value: String? cannot be passed to prop: String
            }
        },
    )