Auto merge of #104455 - the8472:dont-drain-on-drop, r=Amanieu

Don't drain-on-drop in DrainFilter impls of various collections.

This removes drain-on-drop behavior from various unstable DrainFilter impls (not yet for HashSet/Map) because that behavior [is problematic](https://github.com/rust-lang/rust/issues/43244#issuecomment-641638196) (because it can lead to panic-in-drop when user closures panic) and may become forbidden if [this draft RFC passes](https://github.com/rust-lang/rfcs/pull/3288).

closes #101122

[ACP](https://github.com/rust-lang/libs-team/issues/136)

affected tracking issues
* #43244
* #70530
* #59618

Related hashbrown update: https://github.com/rust-lang/hashbrown/pull/374

3 files changed, 5 insertions, 6 deletions

diff --git a/compiler/rustc_trait_selection/src/lib.rs b/compiler/rustc_trait_selection/src/lib.rs
index ed3994be987..56d37d58de7 100644
--- a/compiler/rustc_trait_selection/src/lib.rs
+++ b/compiler/rustc_trait_selection/src/lib.rs
@@ -14,8 +14,7 @@
 #![feature(associated_type_bounds)]
 #![feature(box_patterns)]
 #![feature(control_flow_enum)]
-#![feature(drain_filter)]
-#![feature(hash_drain_filter)]
+#![feature(extract_if)]
 #![feature(let_chains)]
 #![feature(if_let_guard)]
 #![feature(never_type)]
diff --git a/compiler/rustc_trait_selection/src/traits/mod.rs b/compiler/rustc_trait_selection/src/traits/mod.rs
index ab58684ffd9..db9cb82585f 100644
--- a/compiler/rustc_trait_selection/src/traits/mod.rs
+++ b/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(..))
diff --git a/compiler/rustc_trait_selection/src/traits/project.rs b/compiler/rustc_trait_selection/src/traits/project.rs
index 563cc257e03..0a1e971f268 100644
--- a/compiler/rustc_trait_selection/src/traits/project.rs
+++ b/compiler/rustc_trait_selection/src/traits/project.rs
@@ -1170,11 +1170,11 @@ fn opt_normalize_projection_type<'a, 'b, 'tcx>(
             };
 
             let mut deduped: SsoHashSet<_> = Default::default();
-            result.obligations.drain_filter(|projected_obligation| {
+            result.obligations.retain(|projected_obligation| {
                 if !deduped.insert(projected_obligation.clone()) {
-                    return true;
+                    return false;
                 }
-                false
+                true
             });
 
             if use_cache {