toInt method
Only safe if the top three limbs are zero and the low limb is
double-safe — delegates to Uint64.toInt()'s own guard, throwing
IntegerError otherwise (use toBigInt for the general case).
Implementation
int toInt() {
if (!_d3.isZero || !_d2.isZero || !_d1.isZero) {
throw IntegerError.toIntConvertionError;
}
return _d0.toInt();
}