Tracking Issue for map_try_insert #82766

// alloc::collections::btree_map

impl<K: Ord, V> BTreeMap<K, V> {
    pub fn try_insert(&mut self, key: K, value: V) -> Result<&mut V, OccupiedError<'_, K, V>>;
}

pub struct OccupiedError<'a, K: 'a, V: 'a> {
    pub entry: OccupiedEntry<'a, K, V>,
    pub value: V,
}

impl<K: Debug + Ord, V: Debug> Debug for OccupiedError<'_, K, V>;
impl<'a, K: Debug + Ord, V: Debug> Display for OccupiedError<'a, K, V>;
impl<'a, K: Debug + Ord, V: Debug> Error for OccupiedError<'a, K, V>;

// std::collections::hash_map

impl<K: Eq + Hash, V, S: BuildHasher> HashMap<K, V, S> {
    pub fn try_insert(&mut self, key: K, value: V) -> Result<&mut V, OccupiedError<'_, K, V>>;
}

pub struct OccupiedError<'a, K: 'a, V: 'a> {
    pub entry: OccupiedEntry<'a, K, V>,
    pub value: V,
}

impl<K: Debug, V: Debug> Debug for OccupiedError<'_, K, V>;
impl<'a, K: Debug, V: Debug> fmt::Display for OccupiedError<'a, K, V>;
impl<'a, K: Debug, V: Debug> Error for OccupiedError<'a, K, V>;