func (x *Xs) Scan(state ScanState, verb int) os.Error {
	var tok string
	var c int
	var err os.Error
	wid, present := state.Width()
	if !present {
		tok, err = state.Token()
	} else {
		for i := 0; i < wid; i++ {
			c, err = state.GetRune()
			if err != nil {
				break
			}
			tok += string(c)
		}
	}
	if err != nil {
		return err
	}
	if !testing.MustCompile("^" + string(verb) + "+$").MatchString(tok) {
		return os.ErrorString("syntax error for xs")
	}
	*x = Xs(tok)
	return nil
}
func TestScanOverflow(t *testing.T) {
	// different machines and different types report errors with different strings.
	re := testing.MustCompile("overflow|too large|out of range|not representable")
	for _, test := range overflowTests {
		_, err := Sscan(test.text, test.in)
		if err == nil {
			t.Errorf("expected overflow scanning %q", test.text)
			continue
		}
		if !re.MatchString(err.String()) {
			t.Errorf("expected overflow error scanning %q: %s", test.text, err)
		}
	}
}