if zipErr != nil && errors.Is(zipErr, fs.ErrNotExist) &&
			dirErr != nil && errors.Is(dirErr, fs.ErrNotExist) {
			// Nothing downloaded yet. Nothing to verify.
			return nil
		}
		errs = append(errs, fmt.Errorf("%s %s: missing ziphash: %v", mod.Path, mod.Version, err))
		return errs
	}
	h := string(bytes.TrimSpace(data))

	if zipErr != nil && errors.Is(zipErr, fs.ErrNotExist) {
		// ok
	} else {

// report that a file or directory does not exist. It is satisfied by
// [ErrNotExist] as well as some syscall errors.
//
// This function predates [errors.Is]. It only supports errors returned by
// the os package. New code should use errors.Is(err, fs.ErrNotExist).
func IsNotExist(err error) bool {
	return underlyingErrorIs(err, ErrNotExist)
}

// IsPermission returns a boolean indicating whether the error is known to

	// Any error returned aborts the dial and is returned unwrapped.
	StartDial func(network, address string) error

	Question func(dnsmessage.Header, dnsmessage.Question)

	// err may be ErrNotExist or ErrRefused; others map to SERVFAIL (RCode2).
	// A nil error means success.
	HandleA    func(w AWriter, name string) error
	HandleAAAA func(w AAAAWriter, name string) error

// license that can be found in the LICENSE file.

package fs_test

import (
	"errors"
	. "io/fs"
	"testing"
)

type subOnly struct{ SubFS }

func (subOnly) Open(name string) (File, error) { return nil, ErrNotExist }

func TestSub(t *testing.T) {
	check := func(desc string, sub FS, err error) {
		t.Helper()
		if err != nil {
			t.Errorf("Sub(sub): %v", err)
			return
		}
		data, err := ReadFile(sub, "goodbye.txt")

}

// represents a dnsConfig returned by parsing a nonexistent resolv.conf
var defaultResolvConf = &dnsConfig{
	servers:  defaultNS,
	ndots:    1,
	timeout:  5,
	attempts: 2,
	err:      fs.ErrNotExist,
}

func TestConfHostLookupOrder(t *testing.T) {
	// These tests are written for a system with cgo available,
	// without using the netgo tag.
	if netGoBuildTag {

	if err != path.ErrBadPattern {
		t.Fatalf("Glob returned err=%v, want %v", err, path.ErrBadPattern)
	}
}

type globOnly struct{ GlobFS }

func (globOnly) Open(name string) (File, error) { return nil, ErrNotExist }

func TestGlobMethod(t *testing.T) {
	check := func(desc string, names []string, err error) {
		t.Helper()
		if err != nil || len(names) != 1 || names[0] != "hello.txt" {

	// than fallbackOrder to use the Go resolver with that order.

	dnsConf = getSystemDNSConfig()

	if canUseCgo && dnsConf.err != nil && !errors.Is(dnsConf.err, fs.ErrNotExist) && !errors.Is(dnsConf.err, fs.ErrPermission) {
		// We can't read the resolv.conf file, so use cgo if we can.
		return hostLookupCgo, dnsConf
	}

	if canUseCgo && dnsConf.unknownOpt {

// UnknownRevisionError is an error equivalent to fs.ErrNotExist, but for a
// revision rather than a file.
type UnknownRevisionError struct {
	Rev string
}

func (e *UnknownRevisionError) Error() string {
	return "unknown revision " + e.Rev
}
func (UnknownRevisionError) Is(err error) bool {
	return err == fs.ErrNotExist
}

// ErrNoCommits is an error equivalent to fs.ErrNotExist indicating that a given

			store.Del(key)
		}
	}(store)

	raw, err = os.ReadFile(filepath.Join(store.directory, key+store.fileExt))
	if err != nil {
		return
	}

	if len(raw) == 0 {
		return raw, os.ErrNotExist
	}

	return
}

// Get - gets an item from the store.
func (store *QueueStore[I]) Get(key string) (item I, err error) {
	store.RLock()

	defer func(store *QueueStore[I]) {
		store.RUnlock()

//	err = nil
//	if errno != 0 {
//		err = errno
//	}
//
// Errno values can be tested against error values using [errors.Is].
// For example:
//
//	_, _, err := syscall.Syscall(...)
//	if errors.Is(err, fs.ErrNotExist) ...
type Errno uintptr

func (e Errno) Error() string {
	if 0 <= int(e) && int(e) < len(errorstr) {
		s := errorstr[e]
		if s != "" {
			return s
		}
	}
	return "errno " + itoa.Itoa(int(e))
}