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Rollup merge of #78083 - ChaiTRex:master, r=m-ou-se

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Stabilize or_insert_with_key

Stabilizes the `or_insert_with_key` feature from https://github.com/rust-lang/rust/issues/71024. This allows inserting key-derived values when a `HashMap`/`BTreeMap` entry is vacant.

The difference between this and  `.or_insert_with(|| ... )` is that this provides a reference to the key to the closure after it is moved with `.entry(key_being_moved)`, avoiding the need to copy or clone the key.
This commit is contained in:
Yuki Okushi 2020-12-19 15:15:57 +09:00 committed by GitHub
commit 0765536c0b
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3 changed files with 15 additions and 11 deletions
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2
compiler/rustc_data_structures/src/sso/map.rs
View File

@ -40,7 +40,7 @@ const SSO_ARRAY_SIZE: usize = 8;
// into_keys/into_values (unstable)
// all raw_entry-related
// PartialEq/Eq (requires sorting the array)
// Entry::or_insert_with_key (unstable)
// Entry::or_insert_with_key
// Vacant/Occupied entries and related
//
// FIXME: In HashMap most methods accepting key reference

12
library/alloc/src/collections/btree/map/entry.rs
View File

@ -116,15 +116,16 @@ impl<'a, K: Ord, V> Entry<'a, K, V> {
}
}
#[unstable(feature = "or_insert_with_key", issue = "71024")]
/// Ensures a value is in the entry by inserting, if empty, the result of the default function,
/// which takes the key as its argument, and returns a mutable reference to the value in the
/// entry.
/// Ensures a value is in the entry by inserting, if empty, the result of the default function.
/// This method allows for generating key-derived values for insertion by providing the default
/// function a reference to the key that was moved during the `.entry(key)` method call.
///
/// The reference to the moved key is provided so that cloning or copying the key is
/// unnecessary, unlike with `.or_insert_with(|| ... )`.
///
/// # Examples
///
/// ```
/// #![feature(or_insert_with_key)]
/// use std::collections::BTreeMap;
///
/// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
@ -134,6 +135,7 @@ impl<'a, K: Ord, V> Entry<'a, K, V> {
/// assert_eq!(map["poneyland"], 9);
/// ```
#[inline]
#[stable(feature = "or_insert_with_key", since = "1.50.0")]
pub fn or_insert_with_key<F: FnOnce(&K) -> V>(self, default: F) -> &'a mut V {
match self {
Occupied(entry) => entry.into_mut(),

12
library/std/src/collections/hash/map.rs
View File

@ -2219,14 +2219,16 @@ impl<'a, K, V> Entry<'a, K, V> {
}
}
/// Ensures a value is in the entry by inserting, if empty, the result of the default function,
/// which takes the key as its argument, and returns a mutable reference to the value in the
/// entry.
/// Ensures a value is in the entry by inserting, if empty, the result of the default function.
/// This method allows for generating key-derived values for insertion by providing the default
/// function a reference to the key that was moved during the `.entry(key)` method call.
///
/// The reference to the moved key is provided so that cloning or copying the key is
/// unnecessary, unlike with `.or_insert_with(|| ... )`.
///
/// # Examples
///
/// ```
/// #![feature(or_insert_with_key)]
/// use std::collections::HashMap;
///
/// let mut map: HashMap<&str, usize> = HashMap::new();
@ -2236,7 +2238,7 @@ impl<'a, K, V> Entry<'a, K, V> {
/// assert_eq!(map["poneyland"], 9);
/// ```
#[inline]
#[unstable(feature = "or_insert_with_key", issue = "71024")]
#[stable(feature = "or_insert_with_key", since = "1.50.0")]
pub fn or_insert_with_key<F: FnOnce(&K) -> V>(self, default: F) -> &'a mut V {
match self {
Occupied(entry) => entry.into_mut(),