Actually, I figured it out, it was an iffy looking...

# compiler

[ross_a]

Actually, I figured it out, it was an iffy looking delegate:

class OtherOuterClass {
    data class Leg(
        val leg: PriceKey.Leg<*, *>,
        val resolvedTenor: Settlement.Tenor?,
        val resolvedSettlementDate: Settlement.Date,
    ) : IPriceKeyLeg<Settlement, ClientDealtDirection> by leg
}

Replacing this with the below compiles fine:

class OtherOuterClass {
    data class Leg(
        val leg: PriceKey.Leg<Settlement, ClientDealtDirection>,
        val resolvedTenor: Settlement.Tenor?,
        val resolvedSettlementDate: Settlement.Date,
    ) : IPriceKeyLeg<Settlement, ClientDealtDirection> by leg
}