pub const Error = union(enum) {
    /// The number has leading zeroes.
    leading_zero,
    /// Expected a digit after base prefix.
    digit_after_base,
    /// The base prefix is in uppercase.
    upper_case_base: usize,
    /// Float literal has an invalid base prefix.
    invalid_float_base: usize,
    /// Repeated '_' digit separator.
    repeated_underscore: usize,
    /// '_' digit separator after special character (+-.)
    invalid_underscore_after_special: usize,
    /// Invalid digit for the specified base.
    invalid_digit: struct { i: usize, base: Base },
    /// Invalid digit for an exponent.
    invalid_digit_exponent: usize,
    /// Float literal has multiple periods.
    duplicate_period,
    /// Float literal has multiple exponents.
    duplicate_exponent: usize,
    /// Exponent comes directly after '_' digit separator.
    exponent_after_underscore: usize,
    /// Special character (+-.) comes directly after exponent.
    special_after_underscore: usize,
    /// Number ends in special character (+-.)
    trailing_special: usize,
    /// Number ends in '_' digit separator.
    trailing_underscore: usize,
    /// Character not in [0-9a-zA-Z.+-_]
    invalid_character: usize,
    /// [+-] not immediately after [pPeE]
    invalid_exponent_sign: usize,
    /// Period comes directly after exponent.
    period_after_exponent: usize,
}