Add simple async drop glue generation

Explainer: https://zetanumbers.github.io/book/async-drop-design.html

https://github.com/rust-lang/rust/pull/121801

2 files changed, 61 insertions, 1 deletions

diff --git a/compiler/rustc_ty_utils/src/common_traits.rs b/compiler/rustc_ty_utils/src/common_traits.rs
index 51b908881eb..cb95239e991 100644
--- a/compiler/rustc_ty_utils/src/common_traits.rs
+++ b/compiler/rustc_ty_utils/src/common_traits.rs
@@ -22,6 +22,17 @@ fn is_unpin_raw<'tcx>(tcx: TyCtxt<'tcx>, query: ty::ParamEnvAnd<'tcx, Ty<'tcx>>)
     is_item_raw(tcx, query, LangItem::Unpin)
 }
 
+fn has_surface_async_drop_raw<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    query: ty::ParamEnvAnd<'tcx, Ty<'tcx>>,
+) -> bool {
+    is_item_raw(tcx, query, LangItem::AsyncDrop)
+}
+
+fn has_surface_drop_raw<'tcx>(tcx: TyCtxt<'tcx>, query: ty::ParamEnvAnd<'tcx, Ty<'tcx>>) -> bool {
+    is_item_raw(tcx, query, LangItem::Drop)
+}
+
 fn is_item_raw<'tcx>(
     tcx: TyCtxt<'tcx>,
     query: ty::ParamEnvAnd<'tcx, Ty<'tcx>>,
@@ -34,5 +45,13 @@ fn is_item_raw<'tcx>(
 }
 
 pub(crate) fn provide(providers: &mut Providers) {
-    *providers = Providers { is_copy_raw, is_sized_raw, is_freeze_raw, is_unpin_raw, ..*providers };
+    *providers = Providers {
+        is_copy_raw,
+        is_sized_raw,
+        is_freeze_raw,
+        is_unpin_raw,
+        has_surface_async_drop_raw,
+        has_surface_drop_raw,
+        ..*providers
+    };
 }
diff --git a/compiler/rustc_ty_utils/src/instance.rs b/compiler/rustc_ty_utils/src/instance.rs
index a8f9afb87dd..3a18f4d0939 100644
--- a/compiler/rustc_ty_utils/src/instance.rs
+++ b/compiler/rustc_ty_utils/src/instance.rs
@@ -54,6 +54,47 @@ fn resolve_instance<'tcx>(
                 debug!(" => trivial drop glue");
                 ty::InstanceDef::DropGlue(def_id, None)
             }
+        } else if Some(def_id) == tcx.lang_items().async_drop_in_place_fn() {
+            let ty = args.type_at(0);
+
+            match *ty.kind() {
+                ty::Array(..)
+                | ty::Slice(_)
+                | ty::Tuple(_)
+                | ty::Bool
+                | ty::Char
+                | ty::Int(_)
+                | ty::Uint(_)
+                | ty::Float(_)
+                | ty::Str
+                | ty::RawPtr(_, _)
+                | ty::Ref(..)
+                | ty::FnDef(..)
+                | ty::FnPtr(..)
+                | ty::Infer(ty::IntVar(_) | ty::FloatVar(_))
+                | ty::Adt(..)
+                | ty::Closure(..)
+                | ty::CoroutineClosure(..)
+                | ty::CoroutineWitness(..)
+                | ty::Pat(..)
+                | ty::Never
+                | ty::Coroutine(..) => {}
+
+                ty::Param(_)
+                | ty::Error(_)
+                | ty::Dynamic(..)
+                | ty::Alias(..)
+                | ty::Infer(ty::TyVar(_))
+                | ty::Bound(..)
+                | ty::Foreign(_)
+                | ty::Placeholder(_)
+                | ty::Infer(ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_)) => {
+                    return Ok(None);
+                }
+            }
+
+            debug!(" =>  async drop glue ctor");
+            ty::InstanceDef::AsyncDropGlueCtorShim(def_id, ty)
         } else {
             debug!(" => free item");
             // FIXME(effects): we may want to erase the effect param if that is present on this item.