}
		// su == nil || match(su, u) != nil
		su = u
		return true
	}) {
		return su
	}
	return nil
}

// coreString is like coreType but also considers []byte
// and strings as identical. In this case, if successful and we saw
// a string, the result is of type (possibly untyped) string.
func coreString(t Type) Type {
	t = Unalias(t)
	tpar, _ := t.(*TypeParam)
	if tpar == nil {
		return under(t) // string or untyped string

		}
		// su == nil || match(su, u) != nil
		su = u
		return true
	}) {
		return su
	}
	return nil
}

// coreString is like coreType but also considers []byte
// and strings as identical. In this case, if successful and we saw
// a string, the result is of type (possibly untyped) string.
func coreString(t Type) Type {
	t = Unalias(t)
	tpar, _ := t.(*TypeParam)
	if tpar == nil {
		return under(t) // string or untyped string

		// This form appends the bytes of the string.
		if nargs == 2 && hasDots(call) {
			if ok, _ := x.assignableTo(check, NewSlice(universeByte), nil); ok {
				y := args[1]
				if t := coreString(y.typ); t != nil && isString(t) {
					if check.recordTypes() {
						sig := makeSig(S, S, y.typ)
						sig.variadic = true
						check.recordBuiltinType(call.Fun, sig)
					}
					x.mode = value

	check.expr(nil, x, e.X)
	if x.mode == invalid {
		check.use(e.Index[:]...)
		return
	}

	valid := false
	length := int64(-1) // valid if >= 0
	switch u := coreString(x.typ).(type) {
	case nil:
		check.errorf(x, NonSliceableOperand, invalidOp+"cannot slice %s: %s has no core type", x, x.typ)
		x.mode = invalid
		return

	case *Basic:
		if isString(u) {
			if e.Full {

	check.expr(nil, x, e.X)
	if x.mode == invalid {
		check.use(e.Low, e.High, e.Max)
		return
	}

	valid := false
	length := int64(-1) // valid if >= 0
	switch u := coreString(x.typ).(type) {
	case nil:
		check.errorf(x, NonSliceableOperand, invalidOp+"cannot slice %s: %s has no core type", x, x.typ)
		x.mode = invalid
		return

	case *Basic:
		if isString(u) {

	if variadic {
		n := params.Len()
		if n == 0 {
			panic("variadic function must have at least one parameter")
		}
		core := coreString(params.At(n - 1).typ)
		if _, ok := core.(*Slice); !ok && !isString(core) {
			panic(fmt.Sprintf("got %s, want variadic parameter with unnamed slice type or string as core type", core.String()))
		}
	}

		// This form appends the bytes of the string.
		if nargs == 2 && hasDots(call) {
			if ok, _ := x.assignableTo(check, NewSlice(universeByte), nil); ok {
				y := args[1]
				if t := coreString(y.typ); t != nil && isString(t) {
					if check.recordTypes() {
						sig := makeSig(S, S, y.typ)
						sig.variadic = true
						check.recordBuiltinType(call.Fun, sig)
					}
					x.mode = value

	if variadic {
		n := params.Len()
		if n == 0 {
			panic("variadic function must have at least one parameter")
		}
		core := coreString(params.At(n - 1).typ)
		if _, ok := core.(*Slice); !ok && !isString(core) {
			panic(fmt.Sprintf("got %s, want variadic parameter with unnamed slice type or string as core type", core.String()))
		}
	}

		codestrings = strconv.Itoa(http.StatusOK) + ":1"
	}

	aCodestrings := strings.Split(codestrings, ",")
	codes := make([]codeAndSlices, len(aCodestrings))

	for i, codestring := range aCodestrings {
		codeAndSlice, err := validateCodeAndSlices(codestring)
		if err != nil {
			return []codeAndSlices{{http.StatusBadRequest, 1}}, err
		}
		codes[i] = codeAndSlice
	}

	return codes, nil
}

			continue
		}
		response = cResponse
		if rcode == dns.RcodeSuccess {
			break
		}
		codeString := dns.RcodeToString[rcode]
		log.Debugf("upstream dns error: %v: %v: %v", upstream, getReqNames(req), codeString)
	}
	if response == nil {
		response = new(dns.Msg)
		response.SetReply(req)
		response.Rcode = dns.RcodeServerFailure
	}
	return response