static short toShort(O o) {
  if (o == null) ret (short) 0;
  if (o instanceof Number)
    ret ((Number) o).shortValue();
  if (o instanceof S)
    ret toShort(parseLong((S) o));
  throw fail("not convertible to short: " + getClassName(o));
}

static short toShort(long l) {
  if (l != (short) l) fail("Too large for short: " + l);
  ret (short) l;
}

Began life as a copy of #1002621