impl Duration {
    /// Returns the number of milliseconds contained by this `Duration` as `f64`.
    ///
    /// The returned value does include the fractional (nanosecond) part of the duration.
    ///
    /// # Examples
    /// ```
    /// use std::time::Duration;
    ///
    /// let dur = Duration::new(2, 67_890_000);
    /// assert_eq!(dur.as_millis_f64(), 2678.9);
    /// ```
    pub const fn as_millis_f64(self);

    /// Returns the number of milliseconds contained by this `Duration` as `f32`.
    ///
    /// The returned value does include the fractional (nanosecond) part of the duration.
    ///
    /// # Examples
    /// ```
    /// use std::time::Duration;
    ///
    /// let dur = Duration::new(2, 67_890_000);
    /// assert_eq!(dur.as_millis_f32(), 2678.9);
    /// ```
    pub const fn as_millis_f32(self);
}