From aceff07bbf70ea78d63c8135e5d4d9466a468c43 Mon Sep 17 00:00:00 2001
From: Pieter-Louis Schoeman <pl.schoeman44@gmail.com>
Date: Sat, 2 May 2026 00:46:09 +0200
Subject: [PATCH] Fix async drop glue for Box<T>

---
 compiler/rustc_ty_utils/src/needs_drop.rs     | 32 ++++++++++++++-----
 .../async-await/async-drop/async-drop-box.rs  |  3 --
 .../async-drop/async-drop-box.run.stdout      |  2 +-
 3 files changed, 25 insertions(+), 12 deletions(-)

diff --git a/compiler/rustc_ty_utils/src/needs_drop.rs b/compiler/rustc_ty_utils/src/needs_drop.rs
index 89c526bf8d70a..e9b79f512853a 100644
--- a/compiler/rustc_ty_utils/src/needs_drop.rs
+++ b/compiler/rustc_ty_utils/src/needs_drop.rs
@@ -23,10 +23,11 @@ fn needs_drop_raw<'tcx>(
     // needs drop.
     let adt_has_dtor =
         |adt_def: ty::AdtDef<'tcx>| adt_def.destructor(tcx).map(|_| DtorType::Significant);
-    let res = drop_tys_helper(tcx, query.value, query.typing_env, adt_has_dtor, false, false)
-        .filter(filter_array_elements(tcx, query.typing_env))
-        .next()
-        .is_some();
+    let res =
+        drop_tys_helper(tcx, query.value, query.typing_env, adt_has_dtor, false, false, false)
+            .filter(filter_array_elements(tcx, query.typing_env))
+            .next()
+            .is_some();
 
     debug!("needs_drop_raw({:?}) = {:?}", query, res);
     res
@@ -41,10 +42,11 @@ fn needs_async_drop_raw<'tcx>(
     // it needs async drop.
     let adt_has_async_dtor =
         |adt_def: ty::AdtDef<'tcx>| adt_def.async_destructor(tcx).map(|_| DtorType::Significant);
-    let res = drop_tys_helper(tcx, query.value, query.typing_env, adt_has_async_dtor, false, false)
-        .filter(filter_array_elements_async(tcx, query.typing_env))
-        .next()
-        .is_some();
+    let res =
+        drop_tys_helper(tcx, query.value, query.typing_env, adt_has_async_dtor, false, false, true)
+            .filter(filter_array_elements_async(tcx, query.typing_env))
+            .next()
+            .is_some();
 
     debug!("needs_async_drop_raw({:?}) = {:?}", query, res);
     res
@@ -90,6 +92,7 @@ fn has_significant_drop_raw<'tcx>(
         adt_consider_insignificant_dtor(tcx),
         true,
         false,
+        false,
     )
     .filter(filter_array_elements(tcx, query.typing_env))
     .next()
@@ -331,6 +334,7 @@ fn drop_tys_helper<'tcx>(
     adt_has_dtor: impl Fn(ty::AdtDef<'tcx>) -> Option<DtorType>,
     only_significant: bool,
     exhaustive: bool,
+    async_drop_recurses_into_box: bool,
 ) -> impl Iterator<Item = NeedsDropResult<Ty<'tcx>>> {
     fn with_query_cache<'tcx>(
         tcx: TyCtxt<'tcx>,
@@ -353,6 +357,14 @@ fn drop_tys_helper<'tcx>(
         if adt_def.is_manually_drop() {
             debug!("drop_tys_helper: `{:?}` is manually drop", adt_def);
             Ok(Vec::new())
+        } else if async_drop_recurses_into_box && adt_def.is_box() {
+            let boxed_ty = args.type_at(0);
+            let allocator_ty = args.get(1).map(|arg| arg.expect_ty());
+            let boxed_ty = match boxed_ty.kind() {
+                ty::Dynamic(..) | ty::Error(_) => None,
+                _ => Some(boxed_ty),
+            };
+            Ok([boxed_ty, allocator_ty].into_iter().flatten().collect())
         } else if let Some(dtor_info) = adt_has_dtor(adt_def) {
             match dtor_info {
                 DtorType::Significant => {
@@ -435,6 +447,7 @@ fn adt_drop_tys<'tcx>(
         adt_has_dtor,
         false,
         false,
+        false,
     )
     .collect::<Result<Vec<_>, _>>()
     .map(|components| tcx.mk_type_list(&components))
@@ -455,6 +468,7 @@ fn adt_async_drop_tys<'tcx>(
         adt_has_dtor,
         false,
         false,
+        true,
     )
     .collect::<Result<Vec<_>, _>>()
     .map(|components| tcx.mk_type_list(&components))
@@ -474,6 +488,7 @@ fn adt_significant_drop_tys(
         adt_consider_insignificant_dtor(tcx),
         true,
         false,
+        false,
     )
     .collect::<Result<Vec<_>, _>>()
     .map(|components| tcx.mk_type_list(&components))
@@ -492,6 +507,7 @@ fn list_significant_drop_tys<'tcx>(
             adt_consider_insignificant_dtor(tcx),
             true,
             true,
+            false,
         )
         .filter_map(|res| res.ok())
         .collect::<Vec<_>>(),
diff --git a/tests/ui/async-await/async-drop/async-drop-box.rs b/tests/ui/async-await/async-drop/async-drop-box.rs
index 0a6ed412863a2..f54176afe89a7 100644
--- a/tests/ui/async-await/async-drop/async-drop-box.rs
+++ b/tests/ui/async-await/async-drop/async-drop-box.rs
@@ -4,9 +4,6 @@
 // `Foo` is always inside `Box`
 // Sync version is called in sync context, async version is called in async function.
 
-//@ known-bug: #143658
-// async version is never actually called
-
 #![feature(async_drop)]
 #![allow(incomplete_features)]
 
diff --git a/tests/ui/async-await/async-drop/async-drop-box.run.stdout b/tests/ui/async-await/async-drop/async-drop-box.run.stdout
index a2dab2ba992b5..cb7d0b0fea59d 100644
--- a/tests/ui/async-await/async-drop/async-drop-box.run.stdout
+++ b/tests/ui/async-await/async-drop/async-drop-box.run.stdout
@@ -2,5 +2,5 @@ Foo::new() : 7
 Foo::drop() : 7
 Middle
 Foo::new() : 10
-Foo::drop() : 10
+Foo::async drop() : 10
 Done