s/drain_filter/extract_if/ for Vec, Btree{Map,Set} and LinkedList

compiler/rustc_errors/src/lib.rs

@@ -4,7 +4,7 @@
 
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/")]
 #![feature(array_windows)]
-#![feature(drain_filter)]
+#![feature(extract_if)]
 #![feature(if_let_guard)]
 #![feature(let_chains)]
 #![feature(never_type)]
@@ -1399,7 +1399,7 @@ impl HandlerInner {
                     !self.emitted_diagnostics.insert(diagnostic_hash)
                 };
 
-                diagnostic.children.drain_filter(already_emitted_sub).for_each(|_| {});
+                diagnostic.children.extract_if(already_emitted_sub).for_each(|_| {});
 
                 self.emitter.emit_diagnostic(diagnostic);
                 if diagnostic.is_error() {

compiler/rustc_hir_analysis/src/lib.rs

@@ -59,7 +59,6 @@ This API is completely unstable and subject to change.
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/")]
 #![feature(box_patterns)]
 #![feature(control_flow_enum)]
-#![feature(drain_filter)]
 #![feature(hash_drain_filter)]
 #![feature(if_let_guard)]
 #![feature(is_sorted)]

compiler/rustc_hir_typeck/src/lib.rs

@@ -5,7 +5,6 @@
 #![feature(box_patterns)]
 #![feature(min_specialization)]
 #![feature(control_flow_enum)]
-#![feature(drain_filter)]
 #![feature(option_as_slice)]
 #![allow(rustc::potential_query_instability)]
 #![recursion_limit = "256"]

compiler/rustc_metadata/src/lib.rs

@@ -1,6 +1,6 @@
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/")]
 #![feature(decl_macro)]
-#![feature(drain_filter)]
+#![feature(extract_if)]
 #![feature(generators)]
 #![feature(iter_from_generator)]
 #![feature(let_chains)]

compiler/rustc_metadata/src/native_libs.rs

@@ -425,7 +425,7 @@ impl<'tcx> Collector<'tcx> {
             // can move them to the end of the list below.
             let mut existing = self
                 .libs
-                .drain_filter(|lib| {
+                .extract_if(|lib| {
                     if lib.name.as_str() == passed_lib.name {
                         // FIXME: This whole logic is questionable, whether modifiers are
                         // involved or not, library reordering and kind overriding without

compiler/rustc_middle/src/lib.rs

@@ -54,7 +54,7 @@
 #![feature(try_reserve_kind)]
 #![feature(nonzero_ops)]
 #![feature(decl_macro)]
-#![feature(drain_filter)]
+#![feature(extract_if)]
 #![feature(intra_doc_pointers)]
 #![feature(yeet_expr)]
 #![feature(result_option_inspect)]

compiler/rustc_middle/src/ty/diagnostics.rs

@@ -237,7 +237,7 @@ pub fn suggest_constraining_type_params<'a>(
 
         {
             let mut sized_constraints =
-                constraints.drain_filter(|(_, def_id)| *def_id == tcx.lang_items().sized_trait());
+                constraints.extract_if(|(_, def_id)| *def_id == tcx.lang_items().sized_trait());
             if let Some((constraint, def_id)) = sized_constraints.next() {
                 applicability = Applicability::MaybeIncorrect;
 

compiler/rustc_mir_transform/src/lib.rs

@@ -2,7 +2,6 @@
 #![deny(rustc::untranslatable_diagnostic)]
 #![deny(rustc::diagnostic_outside_of_impl)]
 #![feature(box_patterns)]
-#![feature(drain_filter)]
 #![feature(is_sorted)]
 #![feature(let_chains)]
 #![feature(map_try_insert)]

compiler/rustc_mir_transform/src/sroa.rs

@@ -436,13 +436,12 @@ impl<'tcx, 'll> MutVisitor<'tcx> for ReplacementVisitor<'tcx, 'll> {
             VarDebugInfoContents::Composite { ty: _, ref mut fragments } => {
                 let mut new_fragments = Vec::new();
                 debug!(?fragments);
-                fragments
+                fragments.retain_mut(|fragment| {
-                    .drain_filter(|fragment| {
                     if let Some(repl) =
                             self.replacements.replace_place(self.tcx, fragment.contents.as_ref())
                         {
                             fragment.contents = repl;
-                            false
+                            true
                         } else if let Some(local) = fragment.contents.as_local()
                             && let Some(frg) = self.gather_debug_info_fragments(local)
                         {
@@ -450,12 +449,11 @@ impl<'tcx, 'll> MutVisitor<'tcx> for ReplacementVisitor<'tcx, 'll> {
                                 f.projection.splice(0..0, fragment.projection.iter().copied());
                                 f
                             }));
-                            true
-                        } else {
                             false
+                        } else {
+                            true
                         }
-                    })
+                });
-                    .for_each(drop);
                 debug!(?fragments);
                 debug!(?new_fragments);
                 fragments.extend(new_fragments);

compiler/rustc_resolve/src/diagnostics.rs

@@ -2494,7 +2494,7 @@ fn show_candidates(
     for path_strings in [&mut accessible_path_strings, &mut inaccessible_path_strings] {
         path_strings.sort_by(|a, b| a.0.cmp(&b.0));
         let core_path_strings =
-            path_strings.drain_filter(|p| p.0.starts_with("core::")).collect::<Vec<_>>();
+            path_strings.extract_if(|p| p.0.starts_with("core::")).collect::<Vec<_>>();
         path_strings.extend(core_path_strings);
         path_strings.dedup_by(|a, b| a.0 == b.0);
     }

compiler/rustc_resolve/src/late/diagnostics.rs

@@ -496,7 +496,7 @@ impl<'a: 'ast, 'ast, 'tcx> LateResolutionVisitor<'a, '_, 'ast, 'tcx> {
         // Try to filter out intrinsics candidates, as long as we have
         // some other candidates to suggest.
         let intrinsic_candidates: Vec<_> = candidates
-            .drain_filter(|sugg| {
+            .extract_if(|sugg| {
                 let path = path_names_to_string(&sugg.path);
                 path.starts_with("core::intrinsics::") || path.starts_with("std::intrinsics::")
             })

compiler/rustc_resolve/src/lib.rs

@@ -9,7 +9,7 @@
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/")]
 #![feature(assert_matches)]
 #![feature(box_patterns)]
-#![feature(drain_filter)]
+#![feature(extract_if)]
 #![feature(if_let_guard)]
 #![feature(iter_intersperse)]
 #![feature(let_chains)]

compiler/rustc_trait_selection/src/lib.rs

@@ -14,7 +14,7 @@
 #![feature(associated_type_bounds)]
 #![feature(box_patterns)]
 #![feature(control_flow_enum)]
-#![feature(drain_filter)]
+#![feature(extract_if)]
 #![feature(hash_drain_filter)]
 #![feature(let_chains)]
 #![feature(if_let_guard)]

compiler/rustc_trait_selection/src/traits/mod.rs

@@ -354,7 +354,7 @@ pub fn normalize_param_env_or_error<'tcx>(
     // This works fairly well because trait matching does not actually care about param-env
     // TypeOutlives predicates - these are normally used by regionck.
     let outlives_predicates: Vec<_> = predicates
-        .drain_filter(|predicate| {
+        .extract_if(|predicate| {
             matches!(
                 predicate.kind().skip_binder(),
                 ty::PredicateKind::Clause(ty::Clause::TypeOutlives(..))

compiler/rustc_traits/src/lib.rs

@@ -4,7 +4,6 @@
 #![deny(rustc::untranslatable_diagnostic)]
 #![deny(rustc::diagnostic_outside_of_impl)]
 #![feature(let_chains)]
-#![feature(drain_filter)]
 #![recursion_limit = "256"]
 
 #[macro_use]

library/alloc/benches/btree/map.rs

@@ -385,7 +385,7 @@ pub fn clone_slim_100_and_clear(b: &mut Bencher) {
 #[bench]
 pub fn clone_slim_100_and_drain_all(b: &mut Bencher) {
     let src = slim_map(100);
-    b.iter(|| src.clone().drain_filter(|_, _| true).count())
+    b.iter(|| src.clone().extract_if(|_, _| true).count())
 }
 
 #[bench]
@@ -393,7 +393,7 @@ pub fn clone_slim_100_and_drain_half(b: &mut Bencher) {
     let src = slim_map(100);
     b.iter(|| {
         let mut map = src.clone();
-        assert_eq!(map.drain_filter(|i, _| i % 2 == 0).count(), 100 / 2);
+        assert_eq!(map.extract_if(|i, _| i % 2 == 0).count(), 100 / 2);
         assert_eq!(map.len(), 100 / 2);
     })
 }
@@ -456,7 +456,7 @@ pub fn clone_slim_10k_and_clear(b: &mut Bencher) {
 #[bench]
 pub fn clone_slim_10k_and_drain_all(b: &mut Bencher) {
     let src = slim_map(10_000);
-    b.iter(|| src.clone().drain_filter(|_, _| true).count())
+    b.iter(|| src.clone().extract_if(|_, _| true).count())
 }
 
 #[bench]
@@ -464,7 +464,7 @@ pub fn clone_slim_10k_and_drain_half(b: &mut Bencher) {
     let src = slim_map(10_000);
     b.iter(|| {
         let mut map = src.clone();
-        assert_eq!(map.drain_filter(|i, _| i % 2 == 0).count(), 10_000 / 2);
+        assert_eq!(map.extract_if(|i, _| i % 2 == 0).count(), 10_000 / 2);
         assert_eq!(map.len(), 10_000 / 2);
     })
 }
@@ -527,7 +527,7 @@ pub fn clone_fat_val_100_and_clear(b: &mut Bencher) {
 #[bench]
 pub fn clone_fat_val_100_and_drain_all(b: &mut Bencher) {
     let src = fat_val_map(100);
-    b.iter(|| src.clone().drain_filter(|_, _| true).count())
+    b.iter(|| src.clone().extract_if(|_, _| true).count())
 }
 
 #[bench]
@@ -535,7 +535,7 @@ pub fn clone_fat_val_100_and_drain_half(b: &mut Bencher) {
     let src = fat_val_map(100);
     b.iter(|| {
         let mut map = src.clone();
-        assert_eq!(map.drain_filter(|i, _| i % 2 == 0).count(), 100 / 2);
+        assert_eq!(map.extract_if(|i, _| i % 2 == 0).count(), 100 / 2);
         assert_eq!(map.len(), 100 / 2);
     })
 }

library/alloc/benches/btree/set.rs

@@ -69,7 +69,7 @@ pub fn clone_100_and_clear(b: &mut Bencher) {
 #[bench]
 pub fn clone_100_and_drain_all(b: &mut Bencher) {
     let src = slim_set(100);
-    b.iter(|| src.clone().drain_filter(|_| true).count())
+    b.iter(|| src.clone().extract_if(|_| true).count())
 }
 
 #[bench]
@@ -77,7 +77,7 @@ pub fn clone_100_and_drain_half(b: &mut Bencher) {
     let src = slim_set(100);
     b.iter(|| {
         let mut set = src.clone();
-        assert_eq!(set.drain_filter(|i| i % 2 == 0).count(), 100 / 2);
+        assert_eq!(set.extract_if(|i| i % 2 == 0).count(), 100 / 2);
         assert_eq!(set.len(), 100 / 2);
     })
 }
@@ -140,7 +140,7 @@ pub fn clone_10k_and_clear(b: &mut Bencher) {
 #[bench]
 pub fn clone_10k_and_drain_all(b: &mut Bencher) {
     let src = slim_set(10_000);
-    b.iter(|| src.clone().drain_filter(|_| true).count())
+    b.iter(|| src.clone().extract_if(|_| true).count())
 }
 
 #[bench]
@@ -148,7 +148,7 @@ pub fn clone_10k_and_drain_half(b: &mut Bencher) {
     let src = slim_set(10_000);
     b.iter(|| {
         let mut set = src.clone();
-        assert_eq!(set.drain_filter(|i| i % 2 == 0).count(), 10_000 / 2);
+        assert_eq!(set.extract_if(|i| i % 2 == 0).count(), 10_000 / 2);
         assert_eq!(set.len(), 10_000 / 2);
     })
 }

library/alloc/benches/lib.rs

@@ -1,7 +1,7 @@
 // Disabling on android for the time being
 // See https://github.com/rust-lang/rust/issues/73535#event-3477699747
 #![cfg(not(target_os = "android"))]
-#![feature(btree_drain_filter)]
+#![feature(btree_extract_if)]
 #![feature(iter_next_chunk)]
 #![feature(repr_simd)]
 #![feature(slice_partition_dedup)]

library/alloc/src/collections/btree/map.rs

@@ -1132,7 +1132,7 @@ impl<K, V, A: Allocator + Clone> BTreeMap<K, V, A> {
         K: Ord,
         F: FnMut(&K, &mut V) -> bool,
     {
-        self.drain_filter(|k, v| !f(k, v)).for_each(drop);
+        self.extract_if(|k, v| !f(k, v)).for_each(drop);
     }
 
     /// Moves all elements from `other` into `self`, leaving `other` empty.
@@ -1395,7 +1395,7 @@ impl<K, V, A: Allocator + Clone> BTreeMap<K, V, A> {
     /// The iterator also lets you mutate the value of each element in the
     /// closure, regardless of whether you choose to keep or remove it.
     ///
-    /// If the returned `DrainFilter` is not exhausted, e.g. because it is dropped without iterating
+    /// If the returned `ExtractIf` is not exhausted, e.g. because it is dropped without iterating
     /// or the iteration short-circuits, then the remaining elements will be retained.
     /// Use [`retain`] with a negated predicate if you do not need the returned iterator.
     ///
@@ -1406,26 +1406,26 @@ impl<K, V, A: Allocator + Clone> BTreeMap<K, V, A> {
     /// Splitting a map into even and odd keys, reusing the original map:
     ///
     /// ```
-    /// #![feature(btree_drain_filter)]
+    /// #![feature(btree_extract_if)]
     /// use std::collections::BTreeMap;
     ///
     /// let mut map: BTreeMap<i32, i32> = (0..8).map(|x| (x, x)).collect();
-    /// let evens: BTreeMap<_, _> = map.drain_filter(|k, _v| k % 2 == 0).collect();
+    /// let evens: BTreeMap<_, _> = map.extract_if(|k, _v| k % 2 == 0).collect();
     /// let odds = map;
     /// assert_eq!(evens.keys().copied().collect::<Vec<_>>(), [0, 2, 4, 6]);
     /// assert_eq!(odds.keys().copied().collect::<Vec<_>>(), [1, 3, 5, 7]);
     /// ```
-    #[unstable(feature = "btree_drain_filter", issue = "70530")]
+    #[unstable(feature = "btree_extract_if", issue = "70530")]
-    pub fn drain_filter<F>(&mut self, pred: F) -> DrainFilter<'_, K, V, F, A>
+    pub fn extract_if<F>(&mut self, pred: F) -> ExtractIf<'_, K, V, F, A>
     where
         K: Ord,
         F: FnMut(&K, &mut V) -> bool,
     {
-        let (inner, alloc) = self.drain_filter_inner();
+        let (inner, alloc) = self.extract_if_inner();
-        DrainFilter { pred, inner, alloc }
+        ExtractIf { pred, inner, alloc }
     }
 
-    pub(super) fn drain_filter_inner(&mut self) -> (DrainFilterInner<'_, K, V>, A)
+    pub(super) fn extract_if_inner(&mut self) -> (ExtractIfInner<'_, K, V>, A)
     where
         K: Ord,
     {
@@ -1433,7 +1433,7 @@ impl<K, V, A: Allocator + Clone> BTreeMap<K, V, A> {
             let (root, dormant_root) = DormantMutRef::new(root);
             let front = root.borrow_mut().first_leaf_edge();
             (
-                DrainFilterInner {
+                ExtractIfInner {
                     length: &mut self.length,
                     dormant_root: Some(dormant_root),
                     cur_leaf_edge: Some(front),
@@ -1442,7 +1442,7 @@ impl<K, V, A: Allocator + Clone> BTreeMap<K, V, A> {
             )
         } else {
             (
-                DrainFilterInner {
+                ExtractIfInner {
                     length: &mut self.length,
                     dormant_root: None,
                     cur_leaf_edge: None,
@@ -1896,10 +1896,10 @@ impl<K, V> Default for Values<'_, K, V> {
     }
 }
 
-/// An iterator produced by calling `drain_filter` on BTreeMap.
+/// An iterator produced by calling `extract_if` on BTreeMap.
-#[unstable(feature = "btree_drain_filter", issue = "70530")]
+#[unstable(feature = "btree_extract_if", issue = "70530")]
 #[must_use = "iterators are lazy and do nothing unless consumed"]
-pub struct DrainFilter<
+pub struct ExtractIf<
     'a,
     K,
     V,
@@ -1909,13 +1909,13 @@ pub struct DrainFilter<
     F: 'a + FnMut(&K, &mut V) -> bool,
 {
     pred: F,
-    inner: DrainFilterInner<'a, K, V>,
+    inner: ExtractIfInner<'a, K, V>,
     /// The BTreeMap will outlive this IntoIter so we don't care about drop order for `alloc`.
     alloc: A,
 }
-/// Most of the implementation of DrainFilter are generic over the type
+/// Most of the implementation of ExtractIf are generic over the type
-/// of the predicate, thus also serving for BTreeSet::DrainFilter.
+/// of the predicate, thus also serving for BTreeSet::ExtractIf.
-pub(super) struct DrainFilterInner<'a, K, V> {
+pub(super) struct ExtractIfInner<'a, K, V> {
     /// Reference to the length field in the borrowed map, updated live.
     length: &'a mut usize,
     /// Buried reference to the root field in the borrowed map.
@@ -1927,20 +1927,20 @@ pub(super) struct DrainFilterInner<'a, K, V> {
     cur_leaf_edge: Option<Handle<NodeRef<marker::Mut<'a>, K, V, marker::Leaf>, marker::Edge>>,
 }
 
-#[unstable(feature = "btree_drain_filter", issue = "70530")]
+#[unstable(feature = "btree_extract_if", issue = "70530")]
-impl<K, V, F> fmt::Debug for DrainFilter<'_, K, V, F>
+impl<K, V, F> fmt::Debug for ExtractIf<'_, K, V, F>
 where
     K: fmt::Debug,
     V: fmt::Debug,
     F: FnMut(&K, &mut V) -> bool,
 {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        f.debug_tuple("DrainFilter").field(&self.inner.peek()).finish()
+        f.debug_tuple("ExtractIf").field(&self.inner.peek()).finish()
     }
 }
 
-#[unstable(feature = "btree_drain_filter", issue = "70530")]
+#[unstable(feature = "btree_extract_if", issue = "70530")]
-impl<K, V, F, A: Allocator + Clone> Iterator for DrainFilter<'_, K, V, F, A>
+impl<K, V, F, A: Allocator + Clone> Iterator for ExtractIf<'_, K, V, F, A>
 where
     F: FnMut(&K, &mut V) -> bool,
 {
@@ -1955,14 +1955,14 @@ where
     }
 }
 
-impl<'a, K, V> DrainFilterInner<'a, K, V> {
+impl<'a, K, V> ExtractIfInner<'a, K, V> {
     /// Allow Debug implementations to predict the next element.
     pub(super) fn peek(&self) -> Option<(&K, &V)> {
         let edge = self.cur_leaf_edge.as_ref()?;
         edge.reborrow().next_kv().ok().map(Handle::into_kv)
     }
 
-    /// Implementation of a typical `DrainFilter::next` method, given the predicate.
+    /// Implementation of a typical `ExtractIf::next` method, given the predicate.
     pub(super) fn next<F, A: Allocator + Clone>(&mut self, pred: &mut F, alloc: A) -> Option<(K, V)>
     where
         F: FnMut(&K, &mut V) -> bool,
@@ -1989,7 +1989,7 @@ impl<'a, K, V> DrainFilterInner<'a, K, V> {
         None
     }
 
-    /// Implementation of a typical `DrainFilter::size_hint` method.
+    /// Implementation of a typical `ExtractIf::size_hint` method.
     pub(super) fn size_hint(&self) -> (usize, Option<usize>) {
         // In most of the btree iterators, `self.length` is the number of elements
         // yet to be visited. Here, it includes elements that were visited and that
@@ -1999,8 +1999,8 @@ impl<'a, K, V> DrainFilterInner<'a, K, V> {
     }
 }
 
-#[unstable(feature = "btree_drain_filter", issue = "70530")]
+#[unstable(feature = "btree_extract_if", issue = "70530")]
-impl<K, V, F> FusedIterator for DrainFilter<'_, K, V, F> where F: FnMut(&K, &mut V) -> bool {}
+impl<K, V, F> FusedIterator for ExtractIf<'_, K, V, F> where F: FnMut(&K, &mut V) -> bool {}
 
 #[stable(feature = "btree_range", since = "1.17.0")]
 impl<'a, K, V> Iterator for Range<'a, K, V> {

library/alloc/src/collections/btree/map/tests.rs

@@ -941,13 +941,13 @@ fn test_retain() {
     assert_eq!(map[&6], 60);
 }
 
-mod test_drain_filter {
+mod test_extract_if {
     use super::*;
 
     #[test]
     fn empty() {
         let mut map: BTreeMap<i32, i32> = BTreeMap::new();
-        map.drain_filter(|_, _| unreachable!("there's nothing to decide on")).for_each(drop);
+        map.extract_if(|_, _| unreachable!("there's nothing to decide on")).for_each(drop);
         assert_eq!(map.height(), None);
         map.check();
     }
@@ -957,7 +957,7 @@ mod test_drain_filter {
     fn consumed_keeping_all() {
         let pairs = (0..3).map(|i| (i, i));
         let mut map = BTreeMap::from_iter(pairs);
-        assert!(map.drain_filter(|_, _| false).eq(iter::empty()));
+        assert!(map.extract_if(|_, _| false).eq(iter::empty()));
         map.check();
     }
 
@@ -966,7 +966,7 @@ mod test_drain_filter {
     fn consumed_removing_all() {
         let pairs = (0..3).map(|i| (i, i));
         let mut map = BTreeMap::from_iter(pairs.clone());
-        assert!(map.drain_filter(|_, _| true).eq(pairs));
+        assert!(map.extract_if(|_, _| true).eq(pairs));
         assert!(map.is_empty());
         map.check();
     }
@@ -977,7 +977,7 @@ mod test_drain_filter {
         let pairs = (0..3).map(|i| (i, i));
         let mut map = BTreeMap::from_iter(pairs);
         assert!(
-            map.drain_filter(|_, v| {
+            map.extract_if(|_, v| {
                 *v += 6;
                 false
             })
@@ -994,7 +994,7 @@ mod test_drain_filter {
         let pairs = (0..3).map(|i| (i, i));
         let mut map = BTreeMap::from_iter(pairs);
         assert!(
-            map.drain_filter(|_, v| {
+            map.extract_if(|_, v| {
                 *v += 6;
                 true
             })
@@ -1008,7 +1008,7 @@ mod test_drain_filter {
     fn underfull_keeping_all() {
         let pairs = (0..3).map(|i| (i, i));
         let mut map = BTreeMap::from_iter(pairs);
-        map.drain_filter(|_, _| false).for_each(drop);
+        map.extract_if(|_, _| false).for_each(drop);
         assert!(map.keys().copied().eq(0..3));
         map.check();
     }
@@ -1018,7 +1018,7 @@ mod test_drain_filter {
         let pairs = (0..3).map(|i| (i, i));
         for doomed in 0..3 {
             let mut map = BTreeMap::from_iter(pairs.clone());
-            map.drain_filter(|i, _| *i == doomed).for_each(drop);
+            map.extract_if(|i, _| *i == doomed).for_each(drop);
             assert_eq!(map.len(), 2);
             map.check();
         }
@@ -1029,7 +1029,7 @@ mod test_drain_filter {
         let pairs = (0..3).map(|i| (i, i));
         for sacred in 0..3 {
             let mut map = BTreeMap::from_iter(pairs.clone());
-            map.drain_filter(|i, _| *i != sacred).for_each(drop);
+            map.extract_if(|i, _| *i != sacred).for_each(drop);
             assert!(map.keys().copied().eq(sacred..=sacred));
             map.check();
         }
@@ -1039,7 +1039,7 @@ mod test_drain_filter {
     fn underfull_removing_all() {
         let pairs = (0..3).map(|i| (i, i));
         let mut map = BTreeMap::from_iter(pairs);
-        map.drain_filter(|_, _| true).for_each(drop);
+        map.extract_if(|_, _| true).for_each(drop);
         assert!(map.is_empty());
         map.check();
     }
@@ -1048,7 +1048,7 @@ mod test_drain_filter {
     fn height_0_keeping_all() {
         let pairs = (0..node::CAPACITY).map(|i| (i, i));
         let mut map = BTreeMap::from_iter(pairs);
-        map.drain_filter(|_, _| false).for_each(drop);
+        map.extract_if(|_, _| false).for_each(drop);
         assert!(map.keys().copied().eq(0..node::CAPACITY));
         map.check();
     }
@@ -1058,7 +1058,7 @@ mod test_drain_filter {
         let pairs = (0..node::CAPACITY).map(|i| (i, i));
         for doomed in 0..node::CAPACITY {
             let mut map = BTreeMap::from_iter(pairs.clone());
-            map.drain_filter(|i, _| *i == doomed).for_each(drop);
+            map.extract_if(|i, _| *i == doomed).for_each(drop);
             assert_eq!(map.len(), node::CAPACITY - 1);
             map.check();
         }
@@ -1069,7 +1069,7 @@ mod test_drain_filter {
         let pairs = (0..node::CAPACITY).map(|i| (i, i));
         for sacred in 0..node::CAPACITY {
             let mut map = BTreeMap::from_iter(pairs.clone());
-            map.drain_filter(|i, _| *i != sacred).for_each(drop);
+            map.extract_if(|i, _| *i != sacred).for_each(drop);
             assert!(map.keys().copied().eq(sacred..=sacred));
             map.check();
         }
@@ -1079,7 +1079,7 @@ mod test_drain_filter {
     fn height_0_removing_all() {
         let pairs = (0..node::CAPACITY).map(|i| (i, i));
         let mut map = BTreeMap::from_iter(pairs);
-        map.drain_filter(|_, _| true).for_each(drop);
+        map.extract_if(|_, _| true).for_each(drop);
         assert!(map.is_empty());
         map.check();
     }
@@ -1087,7 +1087,7 @@ mod test_drain_filter {
     #[test]
     fn height_0_keeping_half() {
         let mut map = BTreeMap::from_iter((0..16).map(|i| (i, i)));
-        assert_eq!(map.drain_filter(|i, _| *i % 2 == 0).count(), 8);
+        assert_eq!(map.extract_if(|i, _| *i % 2 == 0).count(), 8);
         assert_eq!(map.len(), 8);
         map.check();
     }
@@ -1096,7 +1096,7 @@ mod test_drain_filter {
     fn height_1_removing_all() {
         let pairs = (0..MIN_INSERTS_HEIGHT_1).map(|i| (i, i));
         let mut map = BTreeMap::from_iter(pairs);
-        map.drain_filter(|_, _| true).for_each(drop);
+        map.extract_if(|_, _| true).for_each(drop);
         assert!(map.is_empty());
         map.check();
     }
@@ -1106,7 +1106,7 @@ mod test_drain_filter {
         let pairs = (0..MIN_INSERTS_HEIGHT_1).map(|i| (i, i));
         for doomed in 0..MIN_INSERTS_HEIGHT_1 {
             let mut map = BTreeMap::from_iter(pairs.clone());
-            map.drain_filter(|i, _| *i == doomed).for_each(drop);
+            map.extract_if(|i, _| *i == doomed).for_each(drop);
             assert_eq!(map.len(), MIN_INSERTS_HEIGHT_1 - 1);
             map.check();
         }
@@ -1117,7 +1117,7 @@ mod test_drain_filter {
         let pairs = (0..MIN_INSERTS_HEIGHT_1).map(|i| (i, i));
         for sacred in 0..MIN_INSERTS_HEIGHT_1 {
             let mut map = BTreeMap::from_iter(pairs.clone());
-            map.drain_filter(|i, _| *i != sacred).for_each(drop);
+            map.extract_if(|i, _| *i != sacred).for_each(drop);
             assert!(map.keys().copied().eq(sacred..=sacred));
             map.check();
         }
@@ -1128,7 +1128,7 @@ mod test_drain_filter {
         let pairs = (0..MIN_INSERTS_HEIGHT_2).map(|i| (i, i));
         for doomed in (0..MIN_INSERTS_HEIGHT_2).step_by(12) {
             let mut map = BTreeMap::from_iter(pairs.clone());
-            map.drain_filter(|i, _| *i == doomed).for_each(drop);
+            map.extract_if(|i, _| *i == doomed).for_each(drop);
             assert_eq!(map.len(), MIN_INSERTS_HEIGHT_2 - 1);
             map.check();
         }
@@ -1139,7 +1139,7 @@ mod test_drain_filter {
         let pairs = (0..MIN_INSERTS_HEIGHT_2).map(|i| (i, i));
         for sacred in (0..MIN_INSERTS_HEIGHT_2).step_by(12) {
             let mut map = BTreeMap::from_iter(pairs.clone());
-            map.drain_filter(|i, _| *i != sacred).for_each(drop);
+            map.extract_if(|i, _| *i != sacred).for_each(drop);
             assert!(map.keys().copied().eq(sacred..=sacred));
             map.check();
         }
@@ -1149,7 +1149,7 @@ mod test_drain_filter {
     fn height_2_removing_all() {
         let pairs = (0..MIN_INSERTS_HEIGHT_2).map(|i| (i, i));
         let mut map = BTreeMap::from_iter(pairs);
-        map.drain_filter(|_, _| true).for_each(drop);
+        map.extract_if(|_, _| true).for_each(drop);
         assert!(map.is_empty());
         map.check();
     }
@@ -1165,7 +1165,7 @@ mod test_drain_filter {
         map.insert(b.spawn(Panic::InDrop), ());
         map.insert(c.spawn(Panic::Never), ());
 
-        catch_unwind(move || map.drain_filter(|dummy, _| dummy.query(true)).for_each(drop))
+        catch_unwind(move || map.extract_if(|dummy, _| dummy.query(true)).for_each(drop))
             .unwrap_err();
 
         assert_eq!(a.queried(), 1);
@@ -1188,7 +1188,7 @@ mod test_drain_filter {
         map.insert(c.spawn(Panic::InQuery), ());
 
         catch_unwind(AssertUnwindSafe(|| {
-            map.drain_filter(|dummy, _| dummy.query(true)).for_each(drop)
+            map.extract_if(|dummy, _| dummy.query(true)).for_each(drop)
         }))
         .unwrap_err();
 
@@ -1217,7 +1217,7 @@ mod test_drain_filter {
         map.insert(c.spawn(Panic::InQuery), ());
 
         {
-            let mut it = map.drain_filter(|dummy, _| dummy.query(true));
+            let mut it = map.extract_if(|dummy, _| dummy.query(true));
             catch_unwind(AssertUnwindSafe(|| while it.next().is_some() {})).unwrap_err();
             // Iterator behaviour after a panic is explicitly unspecified,
             // so this is just the current implementation:
@@ -1660,8 +1660,8 @@ fn assert_sync() {
         v.into_values()
     }
 
-    fn drain_filter<T: Sync + Ord>(v: &mut BTreeMap<T, T>) -> impl Sync + '_ {
+    fn extract_if<T: Sync + Ord>(v: &mut BTreeMap<T, T>) -> impl Sync + '_ {
-        v.drain_filter(|_, _| false)
+        v.extract_if(|_, _| false)
     }
 
     fn iter<T: Sync>(v: &BTreeMap<T, T>) -> impl Sync + '_ {
@@ -1729,8 +1729,8 @@ fn assert_send() {
         v.into_values()
     }
 
-    fn drain_filter<T: Send + Ord>(v: &mut BTreeMap<T, T>) -> impl Send + '_ {
+    fn extract_if<T: Send + Ord>(v: &mut BTreeMap<T, T>) -> impl Send + '_ {
-        v.drain_filter(|_, _| false)
+        v.extract_if(|_, _| false)
     }
 
     fn iter<T: Send + Sync>(v: &BTreeMap<T, T>) -> impl Send + '_ {

library/alloc/src/collections/btree/set.rs

@@ -999,7 +999,7 @@ impl<T, A: Allocator + Clone> BTreeSet<T, A> {
         T: Ord,
         F: FnMut(&T) -> bool,
     {
-        self.drain_filter(|v| !f(v)).for_each(drop);
+        self.extract_if(|v| !f(v)).for_each(drop);
     }
 
     /// Moves all elements from `other` into `self`, leaving `other` empty.
@@ -1084,7 +1084,7 @@ impl<T, A: Allocator + Clone> BTreeSet<T, A> {
     /// yielded. If the closure returns `false`, or panics, the element remains
     /// in the set and will not be yielded.
     ///
-    /// If the returned `DrainFilter` is not exhausted, e.g. because it is dropped without iterating
+    /// If the returned `ExtractIf` is not exhausted, e.g. because it is dropped without iterating
     /// or the iteration short-circuits, then the remaining elements will be retained.
     /// Use [`retain`] with a negated predicate if you do not need the returned iterator.
     ///
@@ -1094,23 +1094,23 @@ impl<T, A: Allocator + Clone> BTreeSet<T, A> {
     /// Splitting a set into even and odd values, reusing the original set:
     ///
     /// ```
-    /// #![feature(btree_drain_filter)]
+    /// #![feature(btree_extract_if)]
     /// use std::collections::BTreeSet;
     ///
     /// let mut set: BTreeSet<i32> = (0..8).collect();
-    /// let evens: BTreeSet<_> = set.drain_filter(|v| v % 2 == 0).collect();
+    /// let evens: BTreeSet<_> = set.extract_if(|v| v % 2 == 0).collect();
     /// let odds = set;
     /// assert_eq!(evens.into_iter().collect::<Vec<_>>(), vec![0, 2, 4, 6]);
     /// assert_eq!(odds.into_iter().collect::<Vec<_>>(), vec![1, 3, 5, 7]);
     /// ```
-    #[unstable(feature = "btree_drain_filter", issue = "70530")]
+    #[unstable(feature = "btree_extract_if", issue = "70530")]
-    pub fn drain_filter<'a, F>(&'a mut self, pred: F) -> DrainFilter<'a, T, F, A>
+    pub fn extract_if<'a, F>(&'a mut self, pred: F) -> ExtractIf<'a, T, F, A>
     where
         T: Ord,
         F: 'a + FnMut(&T) -> bool,
     {
-        let (inner, alloc) = self.map.drain_filter_inner();
+        let (inner, alloc) = self.map.extract_if_inner();
-        DrainFilter { pred, inner, alloc }
+        ExtractIf { pred, inner, alloc }
     }
 
     /// Gets an iterator that visits the elements in the `BTreeSet` in ascending
@@ -1272,10 +1272,10 @@ impl<'a, T, A: Allocator + Clone> IntoIterator for &'a BTreeSet<T, A> {
     }
 }
 
-/// An iterator produced by calling `drain_filter` on BTreeSet.
+/// An iterator produced by calling `extract_if` on BTreeSet.
-#[unstable(feature = "btree_drain_filter", issue = "70530")]
+#[unstable(feature = "btree_extract_if", issue = "70530")]
 #[must_use = "iterators are lazy and do nothing unless consumed"]
-pub struct DrainFilter<
+pub struct ExtractIf<
     'a,
     T,
     F,
@@ -1285,24 +1285,24 @@ pub struct DrainFilter<
     F: 'a + FnMut(&T) -> bool,
 {
     pred: F,
-    inner: super::map::DrainFilterInner<'a, T, SetValZST>,
+    inner: super::map::ExtractIfInner<'a, T, SetValZST>,
     /// The BTreeMap will outlive this IntoIter so we don't care about drop order for `alloc`.
     alloc: A,
 }
 
-#[unstable(feature = "btree_drain_filter", issue = "70530")]
+#[unstable(feature = "btree_extract_if", issue = "70530")]
-impl<T, F, A: Allocator + Clone> fmt::Debug for DrainFilter<'_, T, F, A>
+impl<T, F, A: Allocator + Clone> fmt::Debug for ExtractIf<'_, T, F, A>
 where
     T: fmt::Debug,
     F: FnMut(&T) -> bool,
 {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        f.debug_tuple("DrainFilter").field(&self.inner.peek().map(|(k, _)| k)).finish()
+        f.debug_tuple("ExtractIf").field(&self.inner.peek().map(|(k, _)| k)).finish()
     }
 }
 
-#[unstable(feature = "btree_drain_filter", issue = "70530")]
+#[unstable(feature = "btree_extract_if", issue = "70530")]
-impl<'a, T, F, A: Allocator + Clone> Iterator for DrainFilter<'_, T, F, A>
+impl<'a, T, F, A: Allocator + Clone> Iterator for ExtractIf<'_, T, F, A>
 where
     F: 'a + FnMut(&T) -> bool,
 {
@@ -1319,11 +1319,8 @@ where
     }
 }
 
-#[unstable(feature = "btree_drain_filter", issue = "70530")]
+#[unstable(feature = "btree_extract_if", issue = "70530")]
-impl<T, F, A: Allocator + Clone> FusedIterator for DrainFilter<'_, T, F, A> where
+impl<T, F, A: Allocator + Clone> FusedIterator for ExtractIf<'_, T, F, A> where F: FnMut(&T) -> bool {}
-    F: FnMut(&T) -> bool
-{
-}
 
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T: Ord, A: Allocator + Clone> Extend<T> for BTreeSet<T, A> {

library/alloc/src/collections/btree/set/tests.rs

@@ -366,19 +366,19 @@ fn test_retain() {
 }
 
 #[test]
-fn test_drain_filter() {
+fn test_extract_if() {
     let mut x = BTreeSet::from([1]);
     let mut y = BTreeSet::from([1]);
 
-    x.drain_filter(|_| true).for_each(drop);
+    x.extract_if(|_| true).for_each(drop);
-    y.drain_filter(|_| false).for_each(drop);
+    y.extract_if(|_| false).for_each(drop);
     assert_eq!(x.len(), 0);
     assert_eq!(y.len(), 1);
 }
 
 #[test]
 #[cfg_attr(not(panic = "unwind"), ignore = "test requires unwinding support")]
-fn test_drain_filter_drop_panic_leak() {
+fn test_extract_if_drop_panic_leak() {
     let a = CrashTestDummy::new(0);
     let b = CrashTestDummy::new(1);
     let c = CrashTestDummy::new(2);
@@ -387,7 +387,7 @@ fn test_drain_filter_drop_panic_leak() {
     set.insert(b.spawn(Panic::InDrop));
     set.insert(c.spawn(Panic::Never));
 
-    catch_unwind(move || set.drain_filter(|dummy| dummy.query(true)).for_each(drop)).ok();
+    catch_unwind(move || set.extract_if(|dummy| dummy.query(true)).for_each(drop)).ok();
 
     assert_eq!(a.queried(), 1);
     assert_eq!(b.queried(), 1);
@@ -399,7 +399,7 @@ fn test_drain_filter_drop_panic_leak() {
 
 #[test]
 #[cfg_attr(not(panic = "unwind"), ignore = "test requires unwinding support")]
-fn test_drain_filter_pred_panic_leak() {
+fn test_extract_if_pred_panic_leak() {
     let a = CrashTestDummy::new(0);
     let b = CrashTestDummy::new(1);
     let c = CrashTestDummy::new(2);
@@ -408,9 +408,7 @@ fn test_drain_filter_pred_panic_leak() {
     set.insert(b.spawn(Panic::InQuery));
     set.insert(c.spawn(Panic::InQuery));
 
-    catch_unwind(AssertUnwindSafe(|| {
+    catch_unwind(AssertUnwindSafe(|| set.extract_if(|dummy| dummy.query(true)).for_each(drop)))
-        set.drain_filter(|dummy| dummy.query(true)).for_each(drop)
-    }))
         .ok();
 
     assert_eq!(a.queried(), 1);
@@ -608,8 +606,8 @@ fn assert_sync() {
         v.range(..)
     }
 
-    fn drain_filter<T: Sync + Ord>(v: &mut BTreeSet<T>) -> impl Sync + '_ {
+    fn extract_if<T: Sync + Ord>(v: &mut BTreeSet<T>) -> impl Sync + '_ {
-        v.drain_filter(|_| false)
+        v.extract_if(|_| false)
     }
 
     fn difference<T: Sync + Ord>(v: &BTreeSet<T>) -> impl Sync + '_ {
@@ -647,8 +645,8 @@ fn assert_send() {
         v.range(..)
     }
 
-    fn drain_filter<T: Send + Ord>(v: &mut BTreeSet<T>) -> impl Send + '_ {
+    fn extract_if<T: Send + Ord>(v: &mut BTreeSet<T>) -> impl Send + '_ {
-        v.drain_filter(|_| false)
+        v.extract_if(|_| false)
     }
 
     fn difference<T: Send + Sync + Ord>(v: &BTreeSet<T>) -> impl Send + '_ {

library/alloc/src/collections/linked_list.rs

@@ -1030,11 +1030,11 @@ impl<T, A: Allocator> LinkedList<T, A> {
     /// If the closure returns false, the element will remain in the list and will not be yielded
     /// by the iterator.
     ///
-    /// If the returned `DrainFilter` is not exhausted, e.g. because it is dropped without iterating
+    /// If the returned `ExtractIf` is not exhausted, e.g. because it is dropped without iterating
     /// or the iteration short-circuits, then the remaining elements will be retained.
-    /// Use `drain_filter().for_each(drop)` if you do not need the returned iterator.
+    /// Use `extract_if().for_each(drop)` if you do not need the returned iterator.
     ///
-    /// Note that `drain_filter` lets you mutate every element in the filter closure, regardless of
+    /// Note that `extract_if` lets you mutate every element in the filter closure, regardless of
     /// whether you choose to keep or remove it.
     ///
     /// # Examples
@@ -1042,20 +1042,20 @@ impl<T, A: Allocator> LinkedList<T, A> {
     /// Splitting a list into evens and odds, reusing the original list:
     ///
     /// ```
-    /// #![feature(drain_filter)]
+    /// #![feature(extract_if)]
     /// use std::collections::LinkedList;
     ///
     /// let mut numbers: LinkedList<u32> = LinkedList::new();
     /// numbers.extend(&[1, 2, 3, 4, 5, 6, 8, 9, 11, 13, 14, 15]);
     ///
-    /// let evens = numbers.drain_filter(|x| *x % 2 == 0).collect::<LinkedList<_>>();
+    /// let evens = numbers.extract_if(|x| *x % 2 == 0).collect::<LinkedList<_>>();
     /// let odds = numbers;
     ///
     /// assert_eq!(evens.into_iter().collect::<Vec<_>>(), vec![2, 4, 6, 8, 14]);
     /// assert_eq!(odds.into_iter().collect::<Vec<_>>(), vec![1, 3, 5, 9, 11, 13, 15]);
     /// ```
-    #[unstable(feature = "drain_filter", reason = "recently added", issue = "43244")]
+    #[unstable(feature = "extract_if", reason = "recently added", issue = "43244")]
-    pub fn drain_filter<F>(&mut self, filter: F) -> DrainFilter<'_, T, F, A>
+    pub fn extract_if<F>(&mut self, filter: F) -> ExtractIf<'_, T, F, A>
     where
         F: FnMut(&mut T) -> bool,
     {
@@ -1063,7 +1063,7 @@ impl<T, A: Allocator> LinkedList<T, A> {
         let it = self.head;
         let old_len = self.len;
 
-        DrainFilter { list: self, it, pred: filter, idx: 0, old_len }
+        ExtractIf { list: self, it, pred: filter, idx: 0, old_len }
     }
 }
 
@@ -1807,10 +1807,10 @@ impl<'a, T, A: Allocator> CursorMut<'a, T, A> {
     }
 }
 
-/// An iterator produced by calling `drain_filter` on LinkedList.
+/// An iterator produced by calling `extract_if` on LinkedList.
-#[unstable(feature = "drain_filter", reason = "recently added", issue = "43244")]
+#[unstable(feature = "extract_if", reason = "recently added", issue = "43244")]
 #[must_use = "iterators are lazy and do nothing unless consumed"]
-pub struct DrainFilter<
+pub struct ExtractIf<
     'a,
     T: 'a,
     F: 'a,
@@ -1825,8 +1825,8 @@ pub struct DrainFilter<
     old_len: usize,
 }
 
-#[unstable(feature = "drain_filter", reason = "recently added", issue = "43244")]
+#[unstable(feature = "extract_if", reason = "recently added", issue = "43244")]
-impl<T, F, A: Allocator> Iterator for DrainFilter<'_, T, F, A>
+impl<T, F, A: Allocator> Iterator for ExtractIf<'_, T, F, A>
 where
     F: FnMut(&mut T) -> bool,
 {
@@ -1854,13 +1854,13 @@ where
     }
 }
 
-#[unstable(feature = "drain_filter", reason = "recently added", issue = "43244")]
+#[unstable(feature = "extract_if", reason = "recently added", issue = "43244")]
-impl<T: fmt::Debug, F> fmt::Debug for DrainFilter<'_, T, F>
+impl<T: fmt::Debug, F> fmt::Debug for ExtractIf<'_, T, F>
 where
     F: FnMut(&mut T) -> bool,
 {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        f.debug_tuple("DrainFilter").field(&self.list).finish()
+        f.debug_tuple("ExtractIf").field(&self.list).finish()
     }
 }
 

library/alloc/src/collections/linked_list/tests.rs

@@ -540,10 +540,10 @@ fn test_show() {
 }
 
 #[test]
-fn drain_filter_test() {
+fn extract_if_test() {
     let mut m: LinkedList<u32> = LinkedList::new();
     m.extend(&[1, 2, 3, 4, 5, 6]);
-    let deleted = m.drain_filter(|v| *v < 4).collect::<Vec<_>>();
+    let deleted = m.extract_if(|v| *v < 4).collect::<Vec<_>>();
 
     check_links(&m);
 
@@ -555,7 +555,7 @@ fn drain_filter_test() {
 fn drain_to_empty_test() {
     let mut m: LinkedList<u32> = LinkedList::new();
     m.extend(&[1, 2, 3, 4, 5, 6]);
-    let deleted = m.drain_filter(|_| true).collect::<Vec<_>>();
+    let deleted = m.extract_if(|_| true).collect::<Vec<_>>();
 
     check_links(&m);
 
@@ -811,11 +811,11 @@ fn test_contains() {
 }
 
 #[test]
-fn drain_filter_empty() {
+fn extract_if_empty() {
     let mut list: LinkedList<i32> = LinkedList::new();
 
     {
-        let mut iter = list.drain_filter(|_| true);
+        let mut iter = list.extract_if(|_| true);
         assert_eq!(iter.size_hint(), (0, Some(0)));
         assert_eq!(iter.next(), None);
         assert_eq!(iter.size_hint(), (0, Some(0)));
@@ -828,13 +828,13 @@ fn drain_filter_empty() {
 }
 
 #[test]
-fn drain_filter_zst() {
+fn extract_if_zst() {
     let mut list: LinkedList<_> = [(), (), (), (), ()].into_iter().collect();
     let initial_len = list.len();
     let mut count = 0;
 
     {
-        let mut iter = list.drain_filter(|_| true);
+        let mut iter = list.extract_if(|_| true);
         assert_eq!(iter.size_hint(), (0, Some(initial_len)));
         while let Some(_) = iter.next() {
             count += 1;
@@ -851,14 +851,14 @@ fn drain_filter_zst() {
 }
 
 #[test]
-fn drain_filter_false() {
+fn extract_if_false() {
     let mut list: LinkedList<_> = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10].into_iter().collect();
 
     let initial_len = list.len();
     let mut count = 0;
 
     {
-        let mut iter = list.drain_filter(|_| false);
+        let mut iter = list.extract_if(|_| false);
         assert_eq!(iter.size_hint(), (0, Some(initial_len)));
         for _ in iter.by_ref() {
             count += 1;
@@ -874,14 +874,14 @@ fn drain_filter_false() {
 }
 
 #[test]
-fn drain_filter_true() {
+fn extract_if_true() {
     let mut list: LinkedList<_> = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10].into_iter().collect();
 
     let initial_len = list.len();
     let mut count = 0;
 
     {
-        let mut iter = list.drain_filter(|_| true);
+        let mut iter = list.extract_if(|_| true);
         assert_eq!(iter.size_hint(), (0, Some(initial_len)));
         while let Some(_) = iter.next() {
             count += 1;
@@ -898,7 +898,7 @@ fn drain_filter_true() {
 }
 
 #[test]
-fn drain_filter_complex() {
+fn extract_if_complex() {
     {
         //                [+xxx++++++xxxxx++++x+x++]
         let mut list = [
@@ -908,7 +908,7 @@ fn drain_filter_complex() {
         .into_iter()
         .collect::<LinkedList<_>>();
 
-        let removed = list.drain_filter(|x| *x % 2 == 0).collect::<Vec<_>>();
+        let removed = list.extract_if(|x| *x % 2 == 0).collect::<Vec<_>>();
         assert_eq!(removed.len(), 10);
         assert_eq!(removed, vec![2, 4, 6, 18, 20, 22, 24, 26, 34, 36]);
 
@@ -926,7 +926,7 @@ fn drain_filter_complex() {
                 .into_iter()
                 .collect::<LinkedList<_>>();
 
-        let removed = list.drain_filter(|x| *x % 2 == 0).collect::<Vec<_>>();
+        let removed = list.extract_if(|x| *x % 2 == 0).collect::<Vec<_>>();
         assert_eq!(removed.len(), 10);
         assert_eq!(removed, vec![2, 4, 6, 18, 20, 22, 24, 26, 34, 36]);
 
@@ -944,7 +944,7 @@ fn drain_filter_complex() {
                 .into_iter()
                 .collect::<LinkedList<_>>();
 
-        let removed = list.drain_filter(|x| *x % 2 == 0).collect::<Vec<_>>();
+        let removed = list.extract_if(|x| *x % 2 == 0).collect::<Vec<_>>();
         assert_eq!(removed.len(), 10);
         assert_eq!(removed, vec![2, 4, 6, 18, 20, 22, 24, 26, 34, 36]);
 
@@ -961,7 +961,7 @@ fn drain_filter_complex() {
             .into_iter()
             .collect::<LinkedList<_>>();
 
-        let removed = list.drain_filter(|x| *x % 2 == 0).collect::<Vec<_>>();
+        let removed = list.extract_if(|x| *x % 2 == 0).collect::<Vec<_>>();
         assert_eq!(removed.len(), 10);
         assert_eq!(removed, vec![2, 4, 6, 8, 10, 12, 14, 16, 18, 20]);
 
@@ -975,7 +975,7 @@ fn drain_filter_complex() {
             .into_iter()
             .collect::<LinkedList<_>>();
 
-        let removed = list.drain_filter(|x| *x % 2 == 0).collect::<Vec<_>>();
+        let removed = list.extract_if(|x| *x % 2 == 0).collect::<Vec<_>>();
         assert_eq!(removed.len(), 10);
         assert_eq!(removed, vec![2, 4, 6, 8, 10, 12, 14, 16, 18, 20]);
 
@@ -986,7 +986,7 @@ fn drain_filter_complex() {
 
 #[test]
 #[cfg_attr(not(panic = "unwind"), ignore = "test requires unwinding support")]
-fn drain_filter_drop_panic_leak() {
+fn extract_if_drop_panic_leak() {
     let d0 = CrashTestDummy::new(0);
     let d1 = CrashTestDummy::new(1);
     let d2 = CrashTestDummy::new(2);
@@ -1005,7 +1005,7 @@ fn drain_filter_drop_panic_leak() {
     q.push_front(d1.spawn(Panic::InDrop));
     q.push_front(d0.spawn(Panic::Never));
 
-    catch_unwind(AssertUnwindSafe(|| q.drain_filter(|_| true).for_each(drop))).unwrap_err();
+    catch_unwind(AssertUnwindSafe(|| q.extract_if(|_| true).for_each(drop))).unwrap_err();
 
     assert_eq!(d0.dropped(), 1);
     assert_eq!(d1.dropped(), 1);
@@ -1026,7 +1026,7 @@ fn drain_filter_drop_panic_leak() {
 
 #[test]
 #[cfg_attr(not(panic = "unwind"), ignore = "test requires unwinding support")]
-fn drain_filter_pred_panic_leak() {
+fn extract_if_pred_panic_leak() {
     static mut DROPS: i32 = 0;
 
     #[derive(Debug)]
@@ -1051,7 +1051,7 @@ fn drain_filter_pred_panic_leak() {
     q.push_front(D(0));
 
     catch_unwind(AssertUnwindSafe(|| {
-        q.drain_filter(|item| if item.0 >= 2 { panic!() } else { true }).for_each(drop)
+        q.extract_if(|item| if item.0 >= 2 { panic!() } else { true }).for_each(drop)
     }))
     .ok();
 

library/alloc/src/vec/extract_if.rs

@@ -6,21 +6,21 @@ use super::Vec;
 
 /// An iterator which uses a closure to determine if an element should be removed.
 ///
-/// This struct is created by [`Vec::drain_filter`].
+/// This struct is created by [`Vec::extract_if`].
 /// See its documentation for more.
 ///
 /// # Example
 ///
 /// ```
-/// #![feature(drain_filter)]
+/// #![feature(extract_if)]
 ///
 /// let mut v = vec![0, 1, 2];
-/// let iter: std::vec::DrainFilter<'_, _, _> = v.drain_filter(|x| *x % 2 == 0);
+/// let iter: std::vec::ExtractIf<'_, _, _> = v.extract_if(|x| *x % 2 == 0);
 /// ```
-#[unstable(feature = "drain_filter", reason = "recently added", issue = "43244")]
+#[unstable(feature = "extract_if", reason = "recently added", issue = "43244")]
 #[derive(Debug)]
 #[must_use = "iterators are lazy and do nothing unless consumed"]
-pub struct DrainFilter<
+pub struct ExtractIf<
     'a,
     T,
     F,
@@ -39,13 +39,13 @@ pub struct DrainFilter<
     pub(super) pred: F,
     /// A flag that indicates a panic has occurred in the filter test predicate.
     /// This is used as a hint in the drop implementation to prevent consumption
-    /// of the remainder of the `DrainFilter`. Any unprocessed items will be
+    /// of the remainder of the `ExtractIf`. Any unprocessed items will be
     /// backshifted in the `vec`, but no further items will be dropped or
     /// tested by the filter predicate.
     pub(super) panic_flag: bool,
 }
 
-impl<T, F, A: Allocator> DrainFilter<'_, T, F, A>
+impl<T, F, A: Allocator> ExtractIf<'_, T, F, A>
 where
     F: FnMut(&mut T) -> bool,
 {
@@ -57,8 +57,8 @@ where
     }
 }
 
-#[unstable(feature = "drain_filter", reason = "recently added", issue = "43244")]
+#[unstable(feature = "extract_if", reason = "recently added", issue = "43244")]
-impl<T, F, A: Allocator> Iterator for DrainFilter<'_, T, F, A>
+impl<T, F, A: Allocator> Iterator for ExtractIf<'_, T, F, A>
 where
     F: FnMut(&mut T) -> bool,
 {
@@ -95,8 +95,8 @@ where
     }
 }
 
-#[unstable(feature = "drain_filter", reason = "recently added", issue = "43244")]
+#[unstable(feature = "extract_if", reason = "recently added", issue = "43244")]
-impl<T, F, A: Allocator> Drop for DrainFilter<'_, T, F, A>
+impl<T, F, A: Allocator> Drop for ExtractIf<'_, T, F, A>
 where
     F: FnMut(&mut T) -> bool,
 {

library/alloc/src/vec/mod.rs

@@ -71,10 +71,10 @@ use crate::boxed::Box;
 use crate::collections::TryReserveError;
 use crate::raw_vec::RawVec;
 
-#[unstable(feature = "drain_filter", reason = "recently added", issue = "43244")]
+#[unstable(feature = "extract_if", reason = "recently added", issue = "43244")]
-pub use self::drain_filter::DrainFilter;
+pub use self::extract_if::ExtractIf;
 
-mod drain_filter;
+mod extract_if;
 
 #[cfg(not(no_global_oom_handling))]
 #[stable(feature = "vec_splice", since = "1.21.0")]
@@ -2892,7 +2892,7 @@ impl<T, A: Allocator> Vec<T, A> {
     /// If the closure returns false, the element will remain in the vector and will not be yielded
     /// by the iterator.
     ///
-    /// If the returned `DrainFilter` is not exhausted, e.g. because it is dropped without iterating
+    /// If the returned `ExtractIf` is not exhausted, e.g. because it is dropped without iterating
     /// or the iteration short-circuits, then the remaining elements will be retained.
     /// Use [`retain`] with a negated predicate if you do not need the returned iterator.
     ///
@@ -2916,10 +2916,10 @@ impl<T, A: Allocator> Vec<T, A> {
     /// # assert_eq!(vec, vec![1, 4, 5]);
     /// ```
     ///
-    /// But `drain_filter` is easier to use. `drain_filter` is also more efficient,
+    /// But `extract_if` is easier to use. `extract_if` is also more efficient,
     /// because it can backshift the elements of the array in bulk.
     ///
-    /// Note that `drain_filter` also lets you mutate every element in the filter closure,
+    /// Note that `extract_if` also lets you mutate every element in the filter closure,
     /// regardless of whether you choose to keep or remove it.
     ///
     /// # Examples
@@ -2927,17 +2927,17 @@ impl<T, A: Allocator> Vec<T, A> {
     /// Splitting an array into evens and odds, reusing the original allocation:
     ///
     /// ```
-    /// #![feature(drain_filter)]
+    /// #![feature(extract_if)]
     /// let mut numbers = vec![1, 2, 3, 4, 5, 6, 8, 9, 11, 13, 14, 15];
     ///
-    /// let evens = numbers.drain_filter(|x| *x % 2 == 0).collect::<Vec<_>>();
+    /// let evens = numbers.extract_if(|x| *x % 2 == 0).collect::<Vec<_>>();
     /// let odds = numbers;
     ///
     /// assert_eq!(evens, vec![2, 4, 6, 8, 14]);
     /// assert_eq!(odds, vec![1, 3, 5, 9, 11, 13, 15]);
     /// ```
-    #[unstable(feature = "drain_filter", reason = "recently added", issue = "43244")]
+    #[unstable(feature = "extract_if", reason = "recently added", issue = "43244")]
-    pub fn drain_filter<F>(&mut self, filter: F) -> DrainFilter<'_, T, F, A>
+    pub fn extract_if<F>(&mut self, filter: F) -> ExtractIf<'_, T, F, A>
     where
         F: FnMut(&mut T) -> bool,
     {
@@ -2948,7 +2948,7 @@ impl<T, A: Allocator> Vec<T, A> {
             self.set_len(0);
         }
 
-        DrainFilter { vec: self, idx: 0, del: 0, old_len, pred: filter, panic_flag: false }
+        ExtractIf { vec: self, idx: 0, del: 0, old_len, pred: filter, panic_flag: false }
     }
 }
 

library/alloc/tests/autotraits.rs

@@ -55,7 +55,7 @@ fn test_btree_map() {
 
     require_send_sync(async {
         let _v = None::<
-            alloc::collections::btree_map::DrainFilter<
+            alloc::collections::btree_map::ExtractIf<
                 '_,
                 &u32,
                 &u32,
@@ -149,7 +149,7 @@ fn test_btree_set() {
     });
 
     require_send_sync(async {
-        let _v = None::<alloc::collections::btree_set::DrainFilter<'_, &u32, fn(&&u32) -> bool>>;
+        let _v = None::<alloc::collections::btree_set::ExtractIf<'_, &u32, fn(&&u32) -> bool>>;
         async {}.await;
     });
 
@@ -238,7 +238,7 @@ fn test_linked_list() {
     /*
     require_send_sync(async {
         let _v =
-            None::<alloc::collections::linked_list::DrainFilter<'_, &u32, fn(&mut &u32) -> bool>>;
+            None::<alloc::collections::linked_list::ExtractIf<'_, &u32, fn(&mut &u32) -> bool>>;
         async {}.await;
     });
     */

library/alloc/tests/lib.rs

@@ -1,7 +1,7 @@
 #![feature(allocator_api)]
 #![feature(alloc_layout_extra)]
 #![feature(assert_matches)]
-#![feature(btree_drain_filter)]
+#![feature(btree_extract_if)]
 #![feature(cow_is_borrowed)]
 #![feature(const_cow_is_borrowed)]
 #![feature(const_heap)]
@@ -10,7 +10,7 @@
 #![feature(const_ptr_write)]
 #![feature(const_try)]
 #![feature(core_intrinsics)]
-#![feature(drain_filter)]
+#![feature(extract_if)]
 #![feature(exact_size_is_empty)]
 #![feature(linked_list_cursors)]
 #![feature(map_try_insert)]

library/alloc/tests/vec.rs

@@ -1347,11 +1347,11 @@ fn overaligned_allocations() {
 }
 
 #[test]
-fn drain_filter_empty() {
+fn extract_if_empty() {
     let mut vec: Vec<i32> = vec![];
 
     {
-        let mut iter = vec.drain_filter(|_| true);
+        let mut iter = vec.extract_if(|_| true);
         assert_eq!(iter.size_hint(), (0, Some(0)));
         assert_eq!(iter.next(), None);
         assert_eq!(iter.size_hint(), (0, Some(0)));
@@ -1363,12 +1363,12 @@ fn drain_filter_empty() {
 }
 
 #[test]
-fn drain_filter_zst() {
+fn extract_if_zst() {
     let mut vec = vec![(), (), (), (), ()];
     let initial_len = vec.len();
     let mut count = 0;
     {
-        let mut iter = vec.drain_filter(|_| true);
+        let mut iter = vec.extract_if(|_| true);
         assert_eq!(iter.size_hint(), (0, Some(initial_len)));
         while let Some(_) = iter.next() {
             count += 1;
@@ -1385,13 +1385,13 @@ fn drain_filter_zst() {
 }
 
 #[test]
-fn drain_filter_false() {
+fn extract_if_false() {
     let mut vec = vec![1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
 
     let initial_len = vec.len();
     let mut count = 0;
     {
-        let mut iter = vec.drain_filter(|_| false);
+        let mut iter = vec.extract_if(|_| false);
         assert_eq!(iter.size_hint(), (0, Some(initial_len)));
         for _ in iter.by_ref() {
             count += 1;
@@ -1407,13 +1407,13 @@ fn drain_filter_false() {
 }
 
 #[test]
-fn drain_filter_true() {
+fn extract_if_true() {
     let mut vec = vec![1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
 
     let initial_len = vec.len();
     let mut count = 0;
     {
-        let mut iter = vec.drain_filter(|_| true);
+        let mut iter = vec.extract_if(|_| true);
         assert_eq!(iter.size_hint(), (0, Some(initial_len)));
         while let Some(_) = iter.next() {
             count += 1;
@@ -1430,7 +1430,7 @@ fn drain_filter_true() {
 }
 
 #[test]
-fn drain_filter_complex() {
+fn extract_if_complex() {
     {
         //                [+xxx++++++xxxxx++++x+x++]
         let mut vec = vec![
@@ -1438,7 +1438,7 @@ fn drain_filter_complex() {
             39,
         ];
 
-        let removed = vec.drain_filter(|x| *x % 2 == 0).collect::<Vec<_>>();
+        let removed = vec.extract_if(|x| *x % 2 == 0).collect::<Vec<_>>();
         assert_eq!(removed.len(), 10);
         assert_eq!(removed, vec![2, 4, 6, 18, 20, 22, 24, 26, 34, 36]);
 
@@ -1452,7 +1452,7 @@ fn drain_filter_complex() {
             2, 4, 6, 7, 9, 11, 13, 15, 17, 18, 20, 22, 24, 26, 27, 29, 31, 33, 34, 35, 36, 37, 39,
         ];
 
-        let removed = vec.drain_filter(|x| *x % 2 == 0).collect::<Vec<_>>();
+        let removed = vec.extract_if(|x| *x % 2 == 0).collect::<Vec<_>>();
         assert_eq!(removed.len(), 10);
         assert_eq!(removed, vec![2, 4, 6, 18, 20, 22, 24, 26, 34, 36]);
 
@@ -1465,7 +1465,7 @@ fn drain_filter_complex() {
         let mut vec =
             vec![2, 4, 6, 7, 9, 11, 13, 15, 17, 18, 20, 22, 24, 26, 27, 29, 31, 33, 34, 35, 36];
 
-        let removed = vec.drain_filter(|x| *x % 2 == 0).collect::<Vec<_>>();
+        let removed = vec.extract_if(|x| *x % 2 == 0).collect::<Vec<_>>();
         assert_eq!(removed.len(), 10);
         assert_eq!(removed, vec![2, 4, 6, 18, 20, 22, 24, 26, 34, 36]);
 
@@ -1477,7 +1477,7 @@ fn drain_filter_complex() {
         //                [xxxxxxxxxx+++++++++++]
         let mut vec = vec![2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 1, 3, 5, 7, 9, 11, 13, 15, 17, 19];
 
-        let removed = vec.drain_filter(|x| *x % 2 == 0).collect::<Vec<_>>();
+        let removed = vec.extract_if(|x| *x % 2 == 0).collect::<Vec<_>>();
         assert_eq!(removed.len(), 10);
         assert_eq!(removed, vec![2, 4, 6, 8, 10, 12, 14, 16, 18, 20]);
 
@@ -1489,7 +1489,7 @@ fn drain_filter_complex() {
         //                [+++++++++++xxxxxxxxxx]
         let mut vec = vec![1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20];
 
-        let removed = vec.drain_filter(|x| *x % 2 == 0).collect::<Vec<_>>();
+        let removed = vec.extract_if(|x| *x % 2 == 0).collect::<Vec<_>>();
         assert_eq!(removed.len(), 10);
         assert_eq!(removed, vec![2, 4, 6, 8, 10, 12, 14, 16, 18, 20]);
 
@@ -1502,7 +1502,7 @@ fn drain_filter_complex() {
 #[test]
 #[cfg(not(target_os = "emscripten"))]
 #[cfg_attr(not(panic = "unwind"), ignore = "test requires unwinding support")]
-fn drain_filter_consumed_panic() {
+fn extract_if_consumed_panic() {
     use std::rc::Rc;
     use std::sync::Mutex;
 
@@ -1537,9 +1537,9 @@ fn drain_filter_consumed_panic() {
             }
             c.index < 6
         };
-        let drain = data.drain_filter(filter);
+        let drain = data.extract_if(filter);
 
-        // NOTE: The DrainFilter is explicitly consumed
+        // NOTE: The ExtractIf is explicitly consumed
         drain.for_each(drop);
     });
 
@@ -1555,7 +1555,7 @@ fn drain_filter_consumed_panic() {
 #[test]
 #[cfg(not(target_os = "emscripten"))]
 #[cfg_attr(not(panic = "unwind"), ignore = "test requires unwinding support")]
-fn drain_filter_unconsumed_panic() {
+fn extract_if_unconsumed_panic() {
     use std::rc::Rc;
     use std::sync::Mutex;
 
@@ -1590,9 +1590,9 @@ fn drain_filter_unconsumed_panic() {
             }
             c.index < 6
         };
-        let _drain = data.drain_filter(filter);
+        let _drain = data.extract_if(filter);
 
-        // NOTE: The DrainFilter is dropped without being consumed
+        // NOTE: The ExtractIf is dropped without being consumed
     });
 
     let drop_counts = drop_counts.lock().unwrap();
@@ -1604,9 +1604,9 @@ fn drain_filter_unconsumed_panic() {
 }
 
 #[test]
-fn drain_filter_unconsumed() {
+fn extract_if_unconsumed() {
     let mut vec = vec![1, 2, 3, 4];
-    let drain = vec.drain_filter(|&mut x| x % 2 != 0);
+    let drain = vec.extract_if(|&mut x| x % 2 != 0);
     drop(drain);
     assert_eq!(vec, [1, 2, 3, 4]);
 }

src/librustdoc/lib.rs

@@ -6,7 +6,6 @@
 #![feature(array_methods)]
 #![feature(assert_matches)]
 #![feature(box_patterns)]
-#![feature(drain_filter)]
 #![feature(impl_trait_in_assoc_type)]
 #![feature(iter_intersperse)]
 #![feature(lazy_cell)]

tests/ui/closures/2229_closure_analysis/run_pass/lit-pattern-matching-with-methods.rs

@@ -2,7 +2,7 @@
 //check-pass
 #![warn(unused)]
 #![feature(rustc_attrs)]
-#![feature(btree_drain_filter)]
+#![feature(btree_extract_if)]
 
 use std::collections::BTreeMap;
 use std::panic::{catch_unwind, AssertUnwindSafe};
@@ -14,14 +14,14 @@ fn main() {
     map.insert("c", ());
 
     {
-        let mut it = map.drain_filter(|_, _| true);
+        let mut it = map.extract_if(|_, _| true);
         catch_unwind(AssertUnwindSafe(|| while it.next().is_some() {})).unwrap_err();
         let result = catch_unwind(AssertUnwindSafe(|| it.next()));
         assert!(matches!(result, Ok(None)));
     }
 
     {
-        let mut it = map.drain_filter(|_, _| true);
+        let mut it = map.extract_if(|_, _| true);
         catch_unwind(AssertUnwindSafe(|| while let Some(_) = it.next() {})).unwrap_err();
         let result = catch_unwind(AssertUnwindSafe(|| it.next()));
         assert!(matches!(result, Ok(None)));