require(type is KtFirType)
        val coneType = type.coneType
        val substitutor = EnhancedForWarningConeSubstitutor(typeContext)
        val enhancedConeType = substitutor.substituteType(coneType)

        return enhancedConeType?.asKtType()
    }

    override fun buildSelfClassType(symbol: KtNamedClassOrObjectSymbol): KtType {
        require(symbol is KtFirNamedClassOrObjectSymbol)

        require(type is KtFe10Type)
        return typeApproximator.approximateToSuperType(type.fe10Type, PublicApproximatorConfiguration(approximateLocalTypes))
            ?.toKtType(analysisContext)
    }

    override fun approximateToSubPublicDenotableType(type: KtType, approximateLocalTypes: Boolean): KtType? {
        require(type is KtFe10Type)

      apply {
        require(tls) { "no cipher suites for cleartext connections" }
        require(cipherSuites.isNotEmpty()) { "At least one cipher suite is required" }

        this.cipherSuites = cipherSuites.copyOf() as Array<String> // Defensive copy.
      }

    fun allEnabledTlsVersions() =
      apply {
        require(tls) { "no TLS versions for cleartext connections" }

      require(Protocol.H2_PRIOR_KNOWLEDGE !in protocolList || protocolList.size == 1) {
        "protocols containing h2_prior_knowledge cannot use other protocols: $protocolList"
      }
      require(Protocol.HTTP_1_1 in protocolList || Protocol.H2_PRIOR_KNOWLEDGE in protocolList) {
        "protocols doesn't contain http/1.1: $protocolList"
      }

                // Stubbed top-level function IR symbols (from other source files in the module) require a parent facade class to be
                // generated, which requires a container source to be provided. Without a facade class, function IR symbols will have
                // an `IrExternalPackageFragment` parent, which trips up code generation during IR lowering.

      apply {
        val maxAgeSeconds = maxAge.inWholeSeconds
        require(maxAgeSeconds >= 0) { "maxAge < 0: $maxAgeSeconds" }
        this.maxAgeSeconds = maxAgeSeconds.commonClampToInt()
      }

    fun maxStale(maxStale: Duration) =
      apply {
        val maxStaleSeconds = maxStale.inWholeSeconds
        require(maxStaleSeconds >= 0) { "maxStale < 0: $maxStaleSeconds" }

      // seconds are not supported by this syntax.
      require(year >= 1601)
      require(month != -1)
      require(dayOfMonth in 1..31)
      require(hour in 0..23)
      require(minute in 0..59)
      require(second in 0..59)

      GregorianCalendar(UTC).apply {
        isLenient = false
        set(Calendar.YEAR, year)

    require(keepAliveDuration > 0L) { "keepAliveDuration <= 0: $keepAliveDuration" }
  }

  fun idleConnectionCount(): Int {
    return connections.count {
      it.withLock { it.calls.isEmpty() }
    }
  }

  fun connectionCount(): Int {
    return connections.size
  }

  /**

    flags: Int,
  ) {
    if (type != TYPE_WINDOW_UPDATE && logger.isLoggable(FINE)) {
      logger.fine(frameLog(false, streamId, length, type, flags))
    }
    require(length <= maxFrameSize) { "FRAME_SIZE_ERROR length > $maxFrameSize: $length" }
    require(streamId and 0x80000000.toInt() == 0) { "reserved bit set: $streamId" }
    sink.writeMedium(length)
    sink.writeByte(type and 0xff)
    sink.writeByte(flags and 0xff)

  ) : SerialTask {
    override fun start() {
      taskRunner.assertThreadHoldsLock()
      require(currentTask == this)
      activeThreads++

      tasksExecutor.execute {
        taskRunner.assertThreadDoesntHoldLock()
        require(currentTask == this)
        try {
          runnable.run()
          require(currentTask == this) { "unexpected current task: $currentTask" }
        } finally {