Exhausting when statement with sealed interface and generics

Hello, first post here! I’m having trouble working with sealed classes and generics.

I have a sealed interface with 2 enums that implement it:

sealed interface Nucleotide
enum class DNANucleotide : Nucleotide { Adenine, Cytosine, Guanine, Thymine }
enum class RNANucleotide : Nucleotide { Adenine, Cytosine, Guanine, Uracil }

Then I defined one function for each enum :

fun complement(nucleotide: DNANucleotide): DNANucleotide = when (nucleotide) {
    DNANucleotide.Adenine -> DNANucleotide.Thymine
    DNANucleotide.Cytosine -> DNANucleotide.Guanine
    DNANucleotide.Guanine -> DNANucleotide.Cytosine
    DNANucleotide.Thymine -> DNANucleotide.Adenine
fun complement(nucleotide: RNANucleotide): RNANucleotide = when (nucleotide) {     
    RNANucleotide.Adenine -> RNANucleotide.Uracil 
    RNANucleotide.Cytosine -> RNANucleotide.Guanine 
    RNANucleotide.Guanine -> RNANucleotide.Cytosine 
    RNANucleotide.Uracil -> RNANucleotide.Adenine 

At last I want to add a generic function that includes the last two:

fun <N : Nucleotide> complement(nucleotide: N): N = when (nucleotide) {
    is DNANucleotide -> complement(nucleotide)
    is RNANucleotide -> complement(nucleotide)

This last function doesn’t compile because the when clause isn’t exhausted and the return type is wrong. Any help or tips to solve this? Thanks!

It’s probably related to my own ticket I posted a while ago: KT-19645. Right now using exhaustive when on generic type simply seems to be impossible.

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Yes, unfortunately It seems that exhaustive when on generics is not possible for the moment.