+ /// Tries to reserve capacity for at least `additional` more elements to be inserted
+ /// in the given `HashSet<K,V>`. The collection may reserve more space to avoid
+ /// frequent reallocations.
+ ///
+ /// # Errors
+ ///
+ /// If the capacity overflows, or the allocator reports a failure, then an error
+ /// is returned.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(try_reserve)]
+ /// use std::collections::HashSet;
+ /// let mut set: HashSet<i32> = HashSet::new();
+ /// set.try_reserve(10).expect("why is the test harness OOMing on 10 bytes?");
+ /// ```
+ #[inline]
+ #[unstable(feature = "try_reserve", reason = "new API", issue="48043")]
+ pub fn try_reserve(&mut self, additional: usize) -> Result<(), CollectionAllocErr> {
+ self.map.try_reserve(additional)
+ }
+