Converting a Decimal with absolute value less than 1 and significant bits larger than the number of mantissa bits of the target type causes the function 'n_signif_bits' to be called with parameter 0, which leads to the 'subtract with overflow ' panic.
Converting a Decimal with absolute value less than 1 and significant bits larger than the number of mantissa bits of the target type causes the function 'n_signif_bits' to be called with parameter 0, which leads to the 'subtract with overflow ' panic.