}

func bmIndexRuneASCII(index func([]byte, rune) int) func(b *testing.B, n int) {
	return func(b *testing.B, n int) {
		buf := bmbuf[0:n]
		buf[n-1] = 'x'
		for i := 0; i < b.N; i++ {
			j := index(buf, 'x')
			if j != n-1 {
				b.Fatal("bad index", j)
			}
		}
		buf[n-1] = '\x00'
	}
}

func bmIndexRune(index func([]byte, rune) int) func(b *testing.B, n int) {

	if !ok || u.Op != token.AND {
		return false
	}
	index, ok := u.X.(*ast.IndexExpr)
	if !ok {
		return false
	}

	addr := ""
	deref := ""
	if p.isVariable(index.X) {
		addr = "&"
		deref = "*"
	}

	fmt.Fprintf(sb, "_cgoIndex%d := %s%s; ", i, addr, gofmtPos(index.X, index.X.Pos()))
	origX := index.X
	index.X = ast.NewIdent(fmt.Sprintf("_cgoIndex%d", i))
	if deref == "*" {

func (r *negativeReader) Read([]byte) (int, error) { return -1, nil }

func TestNegativeRead(t *testing.T) {
	// should panic with a description pointing at the reader, not at itself.
	// (should NOT panic with slice index error, for example.)
	b := NewReader(new(negativeReader))
	defer func() {
		switch err := recover().(type) {
		case nil:
			t.Fatal("read did not panic")
		case error: