pub fn highlighting_region(&mut self, region: ty::Region<'_>, number: usize) {
let num_slots = self.highlight_regions.len();
let first_avail_slot =
- self.highlight_regions.iter_mut().filter(|s| s.is_none()).next().unwrap_or_else(|| {
+ self.highlight_regions.iter_mut().find(|s| s.is_none()).unwrap_or_else(|| {
bug!("can only highlight {} placeholders at a time", num_slots,)
});
*first_avail_slot = Some((*region, number));