}
	for _, tt := range tests {
		if got := IndexRune([]byte(tt.in), tt.rune); got != tt.want {
			t.Errorf("IndexRune(%q, %d) = %v; want %v", tt.in, tt.rune, got, tt.want)
		}
	}

	haystack := []byte("test世界")
	allocs := testing.AllocsPerRun(1000, func() {
		if i := IndexRune(haystack, 's'); i != 2 {
			t.Fatalf("'s' at %d; want 2", i)
		}
		if i := IndexRune(haystack, '世'); i != 4 {

	return bytealg.LastIndexByte(s, c)
}

// IndexRune interprets s as a sequence of UTF-8-encoded code points.
// It returns the byte index of the first occurrence in s of the given rune.
// It returns -1 if rune is not present in s.
// If r is [utf8.RuneError], it returns the first instance of any
// invalid UTF-8 byte sequence.
func IndexRune(s []byte, r rune) int {
	const haveFastIndex = bytealg.MaxBruteForce > 0

func predefine(defines flags.MultiFlag) map[string]*Macro {
	macros := make(map[string]*Macro)
	for _, name := range defines {
		value := "1"
		i := strings.IndexRune(name, '=')
		if i > 0 {
			name, value = name[:i], name[i+1:]
		}
		tokens := Tokenize(name)
		if len(tokens) != 1 || tokens[0].ScanToken != scanner.Ident {

result parameters, the function body's statement list must end in
a <a href="#Terminating_statements">terminating statement</a>.
</p>

<pre>
func IndexRune(s string, r rune) int {
	for i, c := range s {
		if c == r {
			return i
		}
	}
	// invalid: missing return statement
}
</pre>

<p>