use core::ops;
#[track_caller]
#[must_use]
pub fn range<R>(range: R, bounds: ops::RangeTo<usize>) -> ops::Range<usize>
where
R: ops::RangeBounds<usize>,
{
let len = bounds.end;
let start: ops::Bound<&usize> = range.start_bound();
let start = match start {
ops::Bound::Included(&start) => start,
ops::Bound::Excluded(start) => start
.checked_add(1)
.unwrap_or_else(|| panic!("attempted to index slice from after maximum usize")),
ops::Bound::Unbounded => 0,
};
let end: ops::Bound<&usize> = range.end_bound();
let end = match end {
ops::Bound::Included(end) => end
.checked_add(1)
.unwrap_or_else(|| panic!("attempted to index slice up to maximum usize")),
ops::Bound::Excluded(&end) => end,
ops::Bound::Unbounded => len,
};
if start > end {
panic!("slice index starts at {start} but ends at {end}");
}
if end > len {
panic!("range end index {end} out of range for slice of length {len}");
}
ops::Range { start, end }
}