Rollup merge of #64656 - passcod:map-entry-insert, r=Amanieu

Implement (HashMap) Entry::insert as per #60142

Implementation of `Entry::insert` as per @SimonSapin's comment on #60142. This requires a patch to hashbrown:

```diff
diff --git a/src/rustc_entry.rs b/src/rustc_entry.rs
index fefa5c3..7de8300 100644
--- a/src/rustc_entry.rs
+++ b/src/rustc_entry.rs
@@ -546,6 +546,32 @@ impl<'a, K, V> RustcVacantEntry<'a, K, V> {
         let bucket = self.table.insert_no_grow(self.hash, (self.key, value));
         unsafe { &mut bucket.as_mut().1 }
     }
+
+    /// Sets the value of the entry with the RustcVacantEntry's key,
+    /// and returns a RustcOccupiedEntry.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use hashbrown::HashMap;
+    /// use hashbrown::hash_map::RustcEntry;
+    ///
+    /// let mut map: HashMap<&str, u32> = HashMap::new();
+    ///
+    /// if let RustcEntry::Vacant(v) = map.rustc_entry("poneyland") {
+    ///     let o = v.insert_and_return(37);
+    ///     assert_eq!(o.get(), &37);
+    /// }
+    /// ```
+     #[inline]
+    pub fn insert_and_return(self, value: V) -> RustcOccupiedEntry<'a, K, V> {
+        let bucket = self.table.insert_no_grow(self.hash, (self.key, value));
+        RustcOccupiedEntry {
+            key: None,
+            elem: bucket,
+            table: self.table
+        }
+    }
 }

 impl<K, V> IterMut<'_, K, V> {
```

This is also only an implementation for HashMap. I tried implementing for BTreeMap, but I don't really understand BTreeMap's internals and require more guidance on implementing the equivalent `VacantEntry::insert_and_return` such that it returns an `OccupiedEntry`. Notably, following the original PR's modifications I end up needing a `Handle<NodeRef<marker::Mut<'_>, _, _, marker::LeafOrInternal>, _>` while I only have a `Handle<NodeRef<marker::Mut<'_>, _, _, marker::Internal>, _>` and don't know how to proceed.

(To be clear, I'm not asking for guidance right now; I'd be happy getting only the HashMap implementation — the subject of this PR — reviewed and ready, and leave the BTreeMap implementation for a latter PR.)

Cargo.lock

@@ -107,6 +107,12 @@ dependencies = [
  "winapi 0.3.6",
 ]
 
+[[package]]
+name = "autocfg"
+version = "0.1.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b671c8fb71b457dd4ae18c4ba1e59aa81793daacc361d82fcd410cef0d491875"
+
 [[package]]
 name = "backtrace"
 version = "0.3.37"
@@ -1269,7 +1275,7 @@ version = "2.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "df044dd42cdb7e32f28557b661406fc0f2494be75199779998810dbc35030e0d"
 dependencies = [
- "hashbrown",
+ "hashbrown 0.5.0",
  "lazy_static 1.3.0",
  "log",
  "pest",
@@ -1286,10 +1292,19 @@ version = "0.5.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e1de41fb8dba9714efd92241565cdff73f78508c95697dd56787d3cba27e2353"
 dependencies = [
+ "serde",
+]
+
+[[package]]
+name = "hashbrown"
+version = "0.6.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6587d09be37fb98a11cb08b9000a3f592451c1b1b613ca69d949160e313a430a"
+dependencies = [
+ "autocfg",
  "compiler_builtins",
  "rustc-std-workspace-alloc",
  "rustc-std-workspace-core",
- "serde",
 ]
 
 [[package]]
@@ -4109,7 +4124,7 @@ dependencies = [
  "core",
  "dlmalloc",
  "fortanix-sgx-abi",
- "hashbrown",
+ "hashbrown 0.6.1",
  "libc",
  "panic_abort",
  "panic_unwind",

src/libstd/Cargo.toml

@@ -23,7 +23,7 @@ libc = { version = "0.2.51", default-features = false, features = ['rustc-dep-of
 compiler_builtins = { version = "0.1.16" }
 profiler_builtins = { path = "../libprofiler_builtins", optional = true }
 unwind = { path = "../libunwind" }
-hashbrown = { version = "0.5.0", features = ['rustc-dep-of-std'] }
+hashbrown = { version = "0.6.1", default-features = false, features = ['rustc-dep-of-std'] }
 
 [dependencies.backtrace_rs]
 package = "backtrace"

src/libstd/collections/hash/map.rs

@@ -2030,6 +2030,31 @@ impl<'a, K, V> Entry<'a, K, V> {
             Vacant(entry) => Vacant(entry),
         }
     }
+
+    /// Sets the value of the entry, and returns an OccupiedEntry.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(entry_insert)]
+    /// use std::collections::HashMap;
+    ///
+    /// let mut map: HashMap<&str, String> = HashMap::new();
+    /// let entry = map.entry("poneyland").insert("hoho".to_string());
+    ///
+    /// assert_eq!(entry.key(), &"poneyland");
+    /// ```
+    #[inline]
+    #[unstable(feature = "entry_insert", issue = "65225")]
+    pub fn insert(self, value: V) -> OccupiedEntry<'a, K, V> {
+        match self {
+            Occupied(mut entry) => {
+                entry.insert(value);
+                entry
+            },
+            Vacant(entry) => entry.insert_entry(value),
+        }
+    }
 }
 
 impl<'a, K, V: Default> Entry<'a, K, V> {
@@ -2347,6 +2372,28 @@ impl<'a, K: 'a, V: 'a> VacantEntry<'a, K, V> {
     pub fn insert(self, value: V) -> &'a mut V {
         self.base.insert(value)
     }
+
+    /// Sets the value of the entry with the VacantEntry's key,
+    /// and returns an OccupiedEntry.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::collections::HashMap;
+    /// use std::collections::hash_map::Entry;
+    ///
+    /// let mut map: HashMap<&str, u32> = HashMap::new();
+    ///
+    /// if let Entry::Vacant(o) = map.entry("poneyland") {
+    ///     o.insert(37);
+    /// }
+    /// assert_eq!(map["poneyland"], 37);
+    /// ```
+    #[inline]
+    fn insert_entry(self, value: V) -> OccupiedEntry<'a, K, V> {
+        let base = self.base.insert_entry(value);
+        OccupiedEntry { base }
+    }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]