pkg unicode/utf16, func DecodeRune(int32, int32) int32
pkg unicode/utf16, func Encode([]int32) []uint16
pkg unicode/utf16, func EncodeRune(int32) (int32, int32)
pkg unicode/utf16, func IsSurrogate(int32) bool
pkg unicode/utf8, const MaxRune ideal-char
pkg unicode/utf8, const RuneError ideal-char
pkg unicode/utf8, const RuneSelf ideal-int
pkg unicode/utf8, const UTFMax ideal-int

		{"☻x\xe2\x98x", '�', len("☻x")},

		// Invalid rune values should never match.
		{"a☺b☻c☹d\xe2\x98�\xff�\xed\xa0\x80", -1, -1},
		{"a☺b☻c☹d\xe2\x98�\xff�\xed\xa0\x80", 0xD800, -1}, // Surrogate pair
		{"a☺b☻c☹d\xe2\x98�\xff�\xed\xa0\x80", utf8.MaxRune + 1, -1},

		// Test the cutover to bytealg.Index when it is triggered in
		// the middle of rune that contains consecutive runs of equal bytes.

by construction. The escapes <code>\u</code> and <code>\U</code>
represent Unicode code points so within them some values are illegal,
in particular those above <code>0x10FFFF</code> and surrogate halves.
</p>

<p>
After a backslash, certain single-character escapes represent special values:
</p>

<pre class="grammar">
\a   U+0007 alert or bell
\b   U+0008 backspace
\f   U+000C form feed

D7FC..D7FF    ; disallowed                             # NA   <reserved-D7FC>..<reserved-D7FF>
D800..DFFF    ; disallowed                             # 2.0  <surrogate-D800>..<surrogate-DFFF>
E000..F8FF    ; disallowed                             # 1.1  <private-use-E000>..<private-use-F8FF>
F900          ; mapped                 ; 8C48          # 1.1  CJK COMPATIBILITY IDEOGRAPH-F900