diff options
| -rw-r--r-- | library/alloc/src/collections/btree/map.rs | 36 | ||||
| -rw-r--r-- | library/alloc/src/collections/btree/map/entry.rs | 35 | ||||
| -rw-r--r-- | library/std/src/collections/hash/map.rs | 68 | ||||
| -rw-r--r-- | library/std/src/error.rs | 18 | ||||
| -rw-r--r-- | library/std/src/lib.rs | 1 |
5 files changed, 157 insertions, 1 deletions
diff --git a/library/alloc/src/collections/btree/map.rs b/library/alloc/src/collections/btree/map.rs index 783f88f026b..622983996aa 100644 --- a/library/alloc/src/collections/btree/map.rs +++ b/library/alloc/src/collections/btree/map.rs @@ -14,7 +14,7 @@ use super::node::{self, marker, ForceResult::*, Handle, NodeRef, Root}; use super::search::SearchResult::*; mod entry; -pub use entry::{Entry, OccupiedEntry, VacantEntry}; +pub use entry::{Entry, OccupiedEntry, OccupiedError, VacantEntry}; use Entry::*; /// Minimum number of elements in nodes that are not a root. @@ -836,6 +836,40 @@ impl<K, V> BTreeMap<K, V> { } } + /// Tries to insert a key-value pair into the map, and returns + /// a mutable reference to the value in the entry. + /// + /// If the map already had this key present, nothing is updated, and + /// an error containing the occupied entry and the value is returned. + /// + /// # Examples + /// + /// Basic usage: + /// + /// ``` + /// #![feature(map_try_insert)] + /// + /// use std::collections::BTreeMap; + /// + /// let mut map = BTreeMap::new(); + /// assert_eq!(map.try_insert(37, "a").unwrap(), &"a"); + /// + /// let err = map.try_insert(37, "b").unwrap_err(); + /// assert_eq!(err.entry.key(), &37); + /// assert_eq!(err.entry.get(), &"a"); + /// assert_eq!(err.value, "b"); + /// ``` + #[unstable(feature = "map_try_insert", issue = "82766")] + pub fn try_insert(&mut self, key: K, value: V) -> Result<&mut V, OccupiedError<'_, K, V>> + where + K: Ord, + { + match self.entry(key) { + Occupied(entry) => Err(OccupiedError { entry, value }), + Vacant(entry) => Ok(entry.insert(value)), + } + } + /// Removes a key from the map, returning the value at the key if the key /// was previously in the map. /// diff --git a/library/alloc/src/collections/btree/map/entry.rs b/library/alloc/src/collections/btree/map/entry.rs index 941f82a8070..6b30d959773 100644 --- a/library/alloc/src/collections/btree/map/entry.rs +++ b/library/alloc/src/collections/btree/map/entry.rs @@ -71,6 +71,41 @@ impl<K: Debug + Ord, V: Debug> Debug for OccupiedEntry<'_, K, V> { } } +/// The error returned by [`try_insert`](BTreeMap::try_insert) when the key already exists. +/// +/// Contains the occupied entry, and the value that was not inserted. +#[unstable(feature = "map_try_insert", issue = "82766")] +pub struct OccupiedError<'a, K: 'a, V: 'a> { + /// The entry in the map that was already occupied. + pub entry: OccupiedEntry<'a, K, V>, + /// The value which was not inserted, because the entry was already occupied. + pub value: V, +} + +#[unstable(feature = "map_try_insert", issue = "82766")] +impl<K: Debug + Ord, V: Debug> Debug for OccupiedError<'_, K, V> { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + f.debug_struct("OccupiedError") + .field("key", self.entry.key()) + .field("old_value", self.entry.get()) + .field("new_value", &self.value) + .finish() + } +} + +#[unstable(feature = "map_try_insert", issue = "82766")] +impl<'a, K: Debug + Ord, V: Debug> fmt::Display for OccupiedError<'a, K, V> { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + write!( + f, + "failed to insert {:?}, key {:?} already exists with value {:?}", + self.value, + self.entry.key(), + self.entry.get(), + ) + } +} + impl<'a, K: Ord, V> Entry<'a, K, V> { /// Ensures a value is in the entry by inserting the default if empty, and returns /// a mutable reference to the value in the entry. diff --git a/library/std/src/collections/hash/map.rs b/library/std/src/collections/hash/map.rs index 27f7191831d..233afa92389 100644 --- a/library/std/src/collections/hash/map.rs +++ b/library/std/src/collections/hash/map.rs @@ -1,3 +1,5 @@ +// ignore-tidy-filelength + #[cfg(test)] mod tests; @@ -842,6 +844,37 @@ where self.base.insert(k, v) } + /// Tries to insert a key-value pair into the map, and returns + /// a mutable reference to the value in the entry. + /// + /// If the map already had this key present, nothing is updated, and + /// an error containing the occupied entry and the value is returned. + /// + /// # Examples + /// + /// Basic usage: + /// + /// ``` + /// #![feature(map_try_insert)] + /// + /// use std::collections::HashMap; + /// + /// let mut map = HashMap::new(); + /// assert_eq!(map.try_insert(37, "a").unwrap(), &"a"); + /// + /// let err = map.try_insert(37, "b").unwrap_err(); + /// assert_eq!(err.entry.key(), &37); + /// assert_eq!(err.entry.get(), &"a"); + /// assert_eq!(err.value, "b"); + /// ``` + #[unstable(feature = "map_try_insert", issue = "82766")] + pub fn try_insert(&mut self, key: K, value: V) -> Result<&mut V, OccupiedError<'_, K, V>> { + match self.entry(key) { + Occupied(entry) => Err(OccupiedError { entry, value }), + Vacant(entry) => Ok(entry.insert(value)), + } + } + /// Removes a key from the map, returning the value at the key if the key /// was previously in the map. /// @@ -1851,6 +1884,41 @@ impl<K: Debug, V> Debug for VacantEntry<'_, K, V> { } } +/// The error returned by [`try_insert`](HashMap::try_insert) when the key already exists. +/// +/// Contains the occupied entry, and the value that was not inserted. +#[unstable(feature = "map_try_insert", issue = "82766")] +pub struct OccupiedError<'a, K: 'a, V: 'a> { + /// The entry in the map that was already occupied. + pub entry: OccupiedEntry<'a, K, V>, + /// The value which was not inserted, because the entry was already occupied. + pub value: V, +} + +#[unstable(feature = "map_try_insert", issue = "82766")] +impl<K: Debug, V: Debug> Debug for OccupiedError<'_, K, V> { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + f.debug_struct("OccupiedError") + .field("key", self.entry.key()) + .field("old_value", self.entry.get()) + .field("new_value", &self.value) + .finish() + } +} + +#[unstable(feature = "map_try_insert", issue = "82766")] +impl<'a, K: Debug, V: Debug> fmt::Display for OccupiedError<'a, K, V> { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + write!( + f, + "failed to insert {:?}, key {:?} already exists with value {:?}", + self.value, + self.entry.key(), + self.entry.get(), + ) + } +} + #[stable(feature = "rust1", since = "1.0.0")] impl<'a, K, V, S> IntoIterator for &'a HashMap<K, V, S> { type Item = (&'a K, &'a V); diff --git a/library/std/src/error.rs b/library/std/src/error.rs index 94338c7b04d..80c35307d52 100644 --- a/library/std/src/error.rs +++ b/library/std/src/error.rs @@ -470,6 +470,24 @@ impl Error for char::DecodeUtf16Error { } } +#[unstable(feature = "map_try_insert", issue = "82766")] +impl<'a, K: Debug + Ord, V: Debug> Error + for crate::collections::btree_map::OccupiedError<'a, K, V> +{ + #[allow(deprecated)] + fn description(&self) -> &str { + "key already exists" + } +} + +#[unstable(feature = "map_try_insert", issue = "82766")] +impl<'a, K: Debug, V: Debug> Error for crate::collections::hash_map::OccupiedError<'a, K, V> { + #[allow(deprecated)] + fn description(&self) -> &str { + "key already exists" + } +} + #[stable(feature = "box_error", since = "1.8.0")] impl<T: Error> Error for Box<T> { #[allow(deprecated, deprecated_in_future)] diff --git a/library/std/src/lib.rs b/library/std/src/lib.rs index f62fb83533c..99ab3888d96 100644 --- a/library/std/src/lib.rs +++ b/library/std/src/lib.rs @@ -281,6 +281,7 @@ #![feature(linkage)] #![feature(llvm_asm)] #![feature(log_syntax)] +#![feature(map_try_insert)] #![feature(maybe_uninit_extra)] #![feature(maybe_uninit_ref)] #![feature(maybe_uninit_slice)] |