FractionDigits constructor
Creates a FractionDigits instance with optional minimum and maximum fraction digits.
Both minimum and maximum must be between 0 and 20, inclusive.
If both are provided, minimum must be less than or equal to maximum.
Implementation
const FractionDigits({this.minimum, this.maximum})
: assert(minimum != null ? 0 <= minimum && minimum <= 20 : true),
assert(minimum != null && maximum != null ? minimum <= maximum : true);