See the comment at updateSubstitutedMemberIfReceiverContainsTypeVariable
It became necessary after delegate inference is rewritten, since before
that happened, stub types were being left there and FIR2IR handled
them accidentally properly because stub types are equal to anything.
But that wasn't really correct even there because stub types are not
intended to leak out of the FIR
^KT-61060
Denis.Zharkov