diff options
Diffstat (limited to 'src/libstd')
| -rw-r--r-- | src/libstd/collections/hash/set.rs | 32 |
1 files changed, 32 insertions, 0 deletions
diff --git a/src/libstd/collections/hash/set.rs b/src/libstd/collections/hash/set.rs index 566e5146cf8..b48700fb944 100644 --- a/src/libstd/collections/hash/set.rs +++ b/src/libstd/collections/hash/set.rs @@ -631,6 +631,38 @@ where self.map.raw_entry_mut().from_key(&value).or_insert(value, ()).0 } + /// Inserts an owned copy of the given `value` into the set if it is not + /// present, then returns a reference to the value in the set. + /// + /// # Examples + /// + /// ``` + /// #![feature(hash_set_entry)] + /// + /// use std::collections::HashSet; + /// + /// let mut set: HashSet<String> = ["cat", "dog", "horse"] + /// .iter().map(|&pet| pet.to_owned()).collect(); + /// + /// assert_eq!(set.len(), 3); + /// for &pet in &["cat", "dog", "fish"] { + /// let value = set.get_or_insert_owned(pet); + /// assert_eq!(value, pet); + /// } + /// assert_eq!(set.len(), 4); // a new "fish" was inserted + /// ``` + #[inline] + #[unstable(feature = "hash_set_entry", issue = "60896")] + pub fn get_or_insert_owned<Q: ?Sized>(&mut self, value: &Q) -> &T + where + T: Borrow<Q>, + Q: Hash + Eq + ToOwned<Owned = T>, + { + // Although the raw entry gives us `&mut T`, we only return `&T` to be consistent with + // `get`. Key mutation is "raw" because you're not supposed to affect `Eq` or `Hash`. + self.map.raw_entry_mut().from_key(value).or_insert_with(|| (value.to_owned(), ())).0 + } + /// Inserts a value computed from `f` into the set if the given `value` is /// not present, then returns a reference to the value in the set. /// |