Async drop box support

compiler/rustc_feature/src/unstable.rs

@@ -388,8 +388,10 @@ declare_features! (
     (unstable, associated_const_equality, "1.58.0", Some(92827)),
     /// Allows associated type defaults.
     (unstable, associated_type_defaults, "1.2.0", Some(29661)),
-    /// Allows implementing `AsyncDrop`.
+    /// Enables async drop code generation
     (incomplete, async_drop, "1.88.0", Some(126482)),
+    /// Allows implementing `AsyncDrop`. For usage in standard library.
+    (incomplete, async_drop_lib, "1.88.0", Some(126482)),
     /// Allows async functions to be called from `dyn Trait`.
     (incomplete, async_fn_in_dyn_trait, "1.85.0", Some(133119)),
     /// Allows `#[track_caller]` on async functions.

compiler/rustc_interface/src/passes.rs

@@ -295,7 +295,6 @@ fn configure_and_expand(
     resolver.resolve_crate(&krate);
 
     CStore::from_tcx(tcx).report_incompatible_target_modifiers(tcx, &krate);
-    CStore::from_tcx(tcx).report_incompatible_async_drop_feature(tcx, &krate);
     krate
 }
 

compiler/rustc_metadata/src/creader.rs

@@ -461,27 +461,6 @@ impl CStore {
         }
     }
 
-    // Report about async drop types in dependency if async drop feature is disabled
-    pub fn report_incompatible_async_drop_feature(&self, tcx: TyCtxt<'_>, krate: &Crate) {
-        if tcx.features().async_drop() {
-            return;
-        }
-        for (_cnum, data) in self.iter_crate_data() {
-            if data.is_proc_macro_crate() {
-                continue;
-            }
-            if data.has_async_drops() {
-                let extern_crate = data.name();
-                let local_crate = tcx.crate_name(LOCAL_CRATE);
-                tcx.dcx().emit_warn(errors::AsyncDropTypesInDependency {
-                    span: krate.spans.inner_span.shrink_to_lo(),
-                    extern_crate,
-                    local_crate,
-                });
-            }
-        }
-    }
-
     pub fn new(metadata_loader: Box<MetadataLoaderDyn>) -> CStore {
         CStore {
             metadata_loader,

compiler/rustc_metadata/src/rmeta/decoder.rs

@@ -2022,10 +2022,6 @@ impl CrateMetadata {
         self.root.header.hash
     }
 
-    pub(crate) fn has_async_drops(&self) -> bool {
-        self.root.tables.adt_async_destructor.len > 0
-    }
-
     fn num_def_ids(&self) -> usize {
         self.root.tables.def_keys.size()
     }

compiler/rustc_passes/src/check_attr.rs

@@ -1648,7 +1648,8 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
             && let hir::ItemKind::Impl(impl_) = item.kind
             && let Some(trait_) = impl_.of_trait
             && let Some(def_id) = trait_.trait_def_id()
-            && self.tcx.is_lang_item(def_id, hir::LangItem::Drop)
+            && (self.tcx.is_lang_item(def_id, hir::LangItem::Drop)
+                || self.tcx.is_lang_item(def_id, hir::LangItem::AsyncDrop))
         {
             return;
         }

compiler/rustc_span/src/symbol.rs

@@ -501,6 +501,7 @@ symbols! {
         async_closure,
         async_drop,
         async_drop_in_place,
+        async_drop_lib,
         async_fn,
         async_fn_in_dyn_trait,
         async_fn_in_trait,

library/alloc/src/boxed.rs

@@ -189,7 +189,7 @@ use core::clone::CloneToUninit;
 use core::cmp::Ordering;
 use core::error::{self, Error};
 use core::fmt;
-use core::future::Future;
+use core::future::{AsyncDrop, Future};
 use core::hash::{Hash, Hasher};
 use core::marker::{Tuple, Unsize};
 use core::mem::{self, SizedTypeProperties};
@@ -1669,6 +1669,23 @@ unsafe impl<#[may_dangle] T: ?Sized, A: Allocator> Drop for Box<T, A> {
     }
 }
 
+#[unstable(feature = "async_drop_lib", issue = "126482")]
+unsafe impl<#[may_dangle] T: ?Sized, A: Allocator> AsyncDrop for Box<T, A> {
+    #[inline]
+    async fn drop(self: Pin<&mut Self>) {
+        // the T in the Box is dropped by the compiler before the destructor is run
+
+        let ptr = self.0;
+
+        unsafe {
+            let layout = Layout::for_value_raw(ptr.as_ptr());
+            if layout.size() != 0 {
+                self.1.deallocate(From::from(ptr.cast()), layout);
+            }
+        }
+    }
+}
+
 #[cfg(not(no_global_oom_handling))]
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T: Default> Default for Box<T> {

library/alloc/src/lib.rs

@@ -164,6 +164,7 @@
 // tidy-alphabetical-start
 #![feature(allocator_internals)]
 #![feature(allow_internal_unstable)]
+#![feature(async_drop_lib)]
 #![feature(cfg_sanitize)]
 #![feature(const_precise_live_drops)]
 #![feature(coroutine_trait)]

library/core/src/future/async_drop.rs

@@ -1,4 +1,4 @@
-#![unstable(feature = "async_drop", issue = "126482")]
+#![unstable(feature = "async_drop_lib", issue = "126482")]
 
 #[allow(unused_imports)]
 use core::future::Future;
@@ -24,7 +24,7 @@ use crate::task::{Context, Poll};
 /// are `Copy` get implicitly duplicated by the compiler, making it very
 /// hard to predict when, and how often destructors will be executed. As such,
 /// these types cannot have destructors.
-#[unstable(feature = "async_drop", issue = "126482")]
+#[unstable(feature = "async_drop_lib", issue = "126482")]
 #[lang = "async_drop"]
 pub trait AsyncDrop {
     /// Executes the async destructor for this type.
@@ -41,7 +41,7 @@ pub trait AsyncDrop {
 }
 
 /// Async drop.
-#[unstable(feature = "async_drop", issue = "126482")]
+#[unstable(feature = "async_drop_lib", issue = "126482")]
 #[lang = "async_drop_in_place"]
 pub async unsafe fn async_drop_in_place<T: ?Sized>(_to_drop: *mut T) {
     // Code here does not matter - this is replaced by the

library/core/src/future/mod.rs

@@ -20,7 +20,7 @@ mod pending;
 mod poll_fn;
 mod ready;
 
-#[unstable(feature = "async_drop", issue = "126482")]
+#[unstable(feature = "async_drop_lib", issue = "126482")]
 pub use async_drop::{AsyncDrop, async_drop_in_place};
 #[stable(feature = "into_future", since = "1.64.0")]
 pub use into_future::IntoFuture;

src/tools/miri/tests/pass/async-drop.rs

@@ -6,7 +6,7 @@
 // please consider modifying rustc's async drop test at
 // `tests/ui/async-await/async-drop/async-drop-initial.rs`.
 
-#![feature(async_drop, impl_trait_in_assoc_type)]
+#![feature(async_drop, async_drop_lib, impl_trait_in_assoc_type)]
 #![allow(incomplete_features, dead_code)]
 
 // FIXME(zetanumbers): consider AsyncDestruct::async_drop cleanup tests

tests/ui/async-await/async-drop/async-drop-future-from-future.rs

@@ -3,7 +3,7 @@
 // Future `bar` with internal async drop `Foo` will have async drop itself.
 // And we trying to drop this future in sync context (`block_on` func)
 
-#![feature(async_drop)]
+#![feature(async_drop, async_drop_lib)]
 #![allow(incomplete_features)]
 
 use std::mem::ManuallyDrop;

tests/ui/async-await/async-drop/async-drop-future-in-sync-context.rs

@@ -3,7 +3,7 @@
 // Future `bar` with internal async drop `Foo` will have async drop itself.
 // And we trying to drop this future in sync context (`block_on` func)
 
-#![feature(async_drop)]
+#![feature(async_drop, async_drop_lib)]
 #![allow(incomplete_features)]
 
 //@ edition: 2021

tests/ui/async-await/async-drop/async-drop-glue-array.rs

@@ -3,7 +3,7 @@
 // struct `Foo` has both sync and async drop.
 // Struct `Complex` contains three `Foo` fields and has complex async drop glue.
 
-#![feature(async_drop)]
+#![feature(async_drop, async_drop_lib)]
 #![allow(incomplete_features)]
 
 use std::mem::ManuallyDrop;

tests/ui/async-await/async-drop/async-drop-glue-generic.rs

@@ -2,7 +2,7 @@
 //@ check-run-results
 // struct `Foo` has both sync and async drop.
 
-#![feature(async_drop)]
+#![feature(async_drop, async_drop_lib)]
 #![allow(incomplete_features)]
 
 use std::mem::ManuallyDrop;

tests/ui/async-await/async-drop/async-drop-glue.rs

@@ -3,7 +3,7 @@
 // struct `Foo` has both sync and async drop.
 // Struct `Complex` contains three `Foo` fields and has complex async drop glue.
 
-#![feature(async_drop)]
+#![feature(async_drop, async_drop_lib)]
 #![allow(incomplete_features)]
 
 use std::mem::ManuallyDrop;

tests/ui/async-await/async-drop/async-drop-initial.rs

@@ -5,7 +5,7 @@
 // please consider modifying miri's async drop test at
 // `src/tools/miri/tests/pass/async-drop.rs`.
 
-#![feature(async_drop, impl_trait_in_assoc_type)]
+#![feature(async_drop, async_drop_lib, impl_trait_in_assoc_type)]
 #![allow(incomplete_features, dead_code)]
 
 //@ edition: 2021

tests/ui/async-await/async-drop/async-drop-middle-drop.rs

@@ -3,7 +3,7 @@
 // Test async drop of coroutine `bar` (with internal async drop),
 // stopped at the middle of execution, with AsyncDrop object Foo active.
 
-#![feature(async_drop)]
+#![feature(async_drop, async_drop_lib)]
 #![allow(incomplete_features)]
 
 //@ edition: 2021

tests/ui/async-await/async-drop/async-drop-open.rs

@@ -3,7 +3,7 @@
 // struct `Foo` has both sync and async drop.
 // Struct `Complex` contains three `Foo` fields and one of them is moved out.
 
-#![feature(async_drop)]
+#![feature(async_drop, async_drop_lib)]
 #![allow(incomplete_features)]
 
 use std::mem::ManuallyDrop;

tests/ui/async-await/async-drop/async-drop.rs

@@ -3,7 +3,7 @@
 // struct `Foo` has both sync and async drop.
 // Sync version is called in sync context, async version is called in async function.
 
-#![feature(async_drop)]
+#![feature(async_drop, async_drop_lib)]
 #![allow(incomplete_features)]
 
 use std::mem::ManuallyDrop;

tests/ui/async-await/async-drop/auxiliary/async-drop-dep.rs

@@ -1,6 +1,6 @@
 //@ edition:2021
 
-#![feature(async_drop)]
+#![feature(async_drop, async_drop_lib)]
 #![allow(incomplete_features)]
 
 pub struct HasDrop;

tests/ui/async-await/async-drop/deref-later-projection.rs

@@ -3,7 +3,7 @@
 //@ build-pass
 //@ edition:2021
 #![crate_type = "lib"]
-#![feature(async_drop)]
+#![feature(async_drop, async_drop_lib)]
 #![allow(incomplete_features)]
 
 use std::{future::AsyncDrop, pin::Pin};

tests/ui/async-await/async-drop/elaborate-index-out-of-bounds.rs

@@ -2,7 +2,7 @@
 // Ex-ICE: #140974
 #![crate_type = "lib"]
 #![allow(incomplete_features)]
-#![feature(async_drop)]
+#![feature(async_drop, async_drop_lib)]
 use core::future::AsyncDrop;
 
 async fn fun(_: HasIncompleteAsyncDrop) {}

tests/ui/async-await/async-drop/ex-ice-132103.rs

@@ -3,7 +3,7 @@
 //! Fixed when re-work async drop to shim drop glue coroutine scheme.
 //@ compile-flags: -Zvalidate-mir -Zinline-mir=yes
 //@ edition: 2018
-#![feature(async_drop)]
+#![feature(async_drop, async_drop_lib)]
 #![allow(incomplete_features)]
 
 use core::future::{async_drop_in_place, Future};