Rollup merge of #48166 - hedgehog1024:hedgehog1024-stabilize-entry_and_modify, r=alexcrichton

Stabilize 'entry_and_modify' feature

Stabilize `entry_and_modify` feature introduced by #44734.

Closes #44733

src/doc/unstable-book/src/library-features/entry-and-modify.md

@@ -1,77 +0,0 @@
-# `entry_and_modify`
-
-The tracking issue for this feature is: [#44733]
-
-[#44733]: https://github.com/rust-lang/rust/issues/44733
-
-------------------------
-
-This introduces a new method for the Entry API of maps
-(`std::collections::HashMap` and `std::collections::BTreeMap`), so that
-occupied entries can be modified before any potential inserts into the
-map.
-
-For example:
-
-```rust
-#![feature(entry_and_modify)]
-# fn main() {
-use std::collections::HashMap;
-
-struct Foo {
-    new: bool,
-}
-
-let mut map: HashMap<&str, Foo> = HashMap::new();
-
-map.entry("quux")
-   .and_modify(|e| e.new = false)
-   .or_insert(Foo { new: true });
-# }
-```
-
-This is not possible with the stable API alone since inserting a default
-_before_ modifying the `new` field would mean we would lose the default state:
-
-```rust
-# fn main() {
-use std::collections::HashMap;
-
-struct Foo {
-    new: bool,
-}
-
-let mut map: HashMap<&str, Foo> = HashMap::new();
-
-map.entry("quux").or_insert(Foo { new: true }).new = false;
-# }
-```
-
-In the above code the `new` field will never be `true`, even though we only
-intended to update that field to `false` for previously extant entries.
-
-To achieve the same effect as `and_modify` we would have to manually match
-against the `Occupied` and `Vacant` variants of the `Entry` enum, which is
-a little less user-friendly, and much more verbose:
-
-```rust
-# fn main() {
-use std::collections::HashMap;
-use std::collections::hash_map::Entry;
-
-struct Foo {
-    new: bool,
-}
-
-let mut map: HashMap<&str, Foo> = HashMap::new();
-
-match map.entry("quux") {
-    Entry::Occupied(entry) => {
-        entry.into_mut().new = false;
-    },
-    Entry::Vacant(entry) => {
-        entry.insert(Foo { new: true });
-    },
-};
-# }
-```

src/liballoc/btree/map.rs

@@ -2114,7 +2114,6 @@ impl<'a, K: Ord, V> Entry<'a, K, V> {
     /// # Examples
     ///
     /// ```
-    /// #![feature(entry_and_modify)]
     /// use std::collections::BTreeMap;
     ///
     /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
@@ -2129,7 +2128,7 @@ impl<'a, K: Ord, V> Entry<'a, K, V> {
     ///    .or_insert(42);
     /// assert_eq!(map["poneyland"], 43);
     /// ```
-    #[unstable(feature = "entry_and_modify", issue = "44733")]
+    #[stable(feature = "entry_and_modify", since = "1.26.0")]
     pub fn and_modify<F>(self, mut f: F) -> Self
         where F: FnMut(&mut V)
     {

src/libstd/collections/hash/map.rs

@@ -2082,7 +2082,6 @@ impl<'a, K, V> Entry<'a, K, V> {
     /// # Examples
     ///
     /// ```
-    /// #![feature(entry_and_modify)]
     /// use std::collections::HashMap;
     ///
     /// let mut map: HashMap<&str, u32> = HashMap::new();
@@ -2097,7 +2096,7 @@ impl<'a, K, V> Entry<'a, K, V> {
     ///    .or_insert(42);
     /// assert_eq!(map["poneyland"], 43);
     /// ```
-    #[unstable(feature = "entry_and_modify", issue = "44733")]
+    #[stable(feature = "entry_and_modify", since = "1.26.0")]
     pub fn and_modify<F>(self, mut f: F) -> Self
         where F: FnMut(&mut V)
     {