/**
         * Not all expressions appear in the [ControlFlowGraph].
         * Still, if we find at least some of them, it's very unlikely that we will ever find a better graph.
         */
        val firCandidates = buildSet {
            fun addCandidate(firCandidate: FirElement) {
                add(firCandidate)

                if (firCandidate is FirBlock) {