code: func (z *Dec) Scan(s fmt.ScanState, ch rune) error {
  	if ch != 'd' && ch != 'f' && ch != 's' && ch != 'v' {
  		return fmt.Errorf("Dec.Scan: invalid verb '%c'", ch)
  	}
  	s.SkipSpace()
  	_, err := z.scan(s)
  	return err
  }
docs: // Scan is a support routine for fmt.Scanner; it sets z to the value of
  // the scanned number. It accepts the decimal formats 'd' and 'f', and
  // handles both equivalently. Bases 2, 8, 16 are not supported.
  // The scale of z is the number of digits after the decimal point
  // (including any trailing 0s), or 0 if there is no decimal point.