}
	})
	if n > 0 {
		t.Errorf("allocations occurred while appending")
	}
}

func TestRuneIO(t *testing.T) {
	const NRune = 1000
	// Built a test slice while we write the data
	b := make([]byte, utf8.UTFMax*NRune)
	var buf Buffer
	n := 0
	for r := rune(0); r < NRune; r++ {
		size := utf8.EncodeRune(b[n:], r)
		nbytes, err := buf.WriteRune(r)
		if err != nil {
			t.Fatalf("WriteRune(%U) error: %s", r, err)

	} else if err != io.EOF {
		t.Error("expected EOF; got", err)
	}
}

func TestReadWriteRune(t *testing.T) {
	const NRune = 1000
	byteBuf := new(bytes.Buffer)
	w := NewWriter(byteBuf)
	// Write the runes out using WriteRune
	buf := make([]byte, utf8.UTFMax)
	for r := rune(0); r < NRune; r++ {
		size := utf8.EncodeRune(buf, r)
		nbytes, err := w.WriteRune(r)
		if err != nil {

var m map[string]int

var chanVar chan int

var ifaceVar any = 5

var assertVar = ifaceVar.(int)

var indexVar = m["foo"]

var Byte byte
var ByteFunc func(byte) rune

type ByteStruct struct {
	B byte
	R rune

</pre>
</li>

<li>
Converting a slice of runes to a string type yields
a string that is the concatenation of the individual rune values
converted to strings.

<pre>
string([]rune{0x767d, 0x9d6c, 0x7fd4})   // "\u767d\u9d6c\u7fd4" == "白鵬翔"
string([]rune{})                         // ""
string([]rune(nil))                      // ""

type MyRunes []rune

		File: []ZipTestFile{
			{
				Name:    "世界",
				Content: []byte{},
				Mode:    0644,
				// Name is valid UTF-8, but format does not have UTF-8 flag set.
				// We don't do UTF-8 detection for multi-byte runes due to
				// false-positives with other encodings (e.g., Shift-JIS).
				// Format says encoding is not UTF-8, so we trust it.
				NonUTF8:  true,
				Modified: time.Date(2017, 11, 6, 13, 9, 27, 0, timeZone(-8*time.Hour)),

// included to match [bufio.Writer]'s WriteRune. The buffer is grown as needed;
// if it becomes too large, WriteRune will panic with [ErrTooLarge].
func (b *Buffer) WriteRune(r rune) (n int, err error) {
	// Compare as uint32 to correctly handle negative runes.
	if uint32(r) < utf8.RuneSelf {
		b.WriteByte(byte(r))
		return 1, nil
	}
	b.lastRead = opInvalid
	m, ok := b.tryGrowByReslice(utf8.UTFMax)
	if !ok {

// UTF-8-encoded rune as a token. The sequence of runes returned is
// equivalent to that from a range loop over the input as a string, which
// means that erroneous UTF-8 encodings translate to U+FFFD = "\xef\xbf\xbd".
// Because of the Scan interface, this makes it impossible for the client to
// distinguish correctly encoded replacement runes from encoding errors.

			t.Errorf("%s(%q) = %q; want %q", funcName, tc.in, actual, tc.out)
		}
	}
}

func tenRunes(r rune) string {
	runes := make([]rune, 10)
	for i := range runes {
		runes[i] = r
	}
	return string(runes)
}

// User-defined self-inverse mapping function
func rot13(r rune) rune {
	const step = 13
	if r >= 'a' && r <= 'z' {
		return ((r - 'a' + step) % 26) + 'a'
	}

	fmt.Println(bytes.LastIndexFunc([]byte("go gopher!"), unicode.IsNumber))
	// Output:
	// 8
	// 9
	// -1
}

func ExampleMap() {
	rot13 := func(r rune) rune {
		switch {
		case r >= 'A' && r <= 'Z':
			return 'A' + (r-'A'+13)%26
		case r >= 'a' && r <= 'z':
			return 'a' + (r-'a'+13)%26
		}
		return r
	}

		line: 1,
		file: file,
	}
}

// We want center dot (·) and division slash (∕) to work as identifier characters.
func isIdentRune(ch rune, i int) bool {
	if unicode.IsLetter(ch) {
		return true
	}
	switch ch {
	case '_': // Underscore; traditional.
		return true
	case '\u00B7': // Represents the period in runtime.exit. U+00B7 '·' middle dot