X-Git-Url: https://git.lizzy.rs/?a=blobdiff_plain;f=compiler%2Frustc_lint%2Fsrc%2Funused.rs;h=43864ed45fae224c5ac60339e84e1eb4399c4557;hb=5fa44b54641cac7dc47964870d08b4ec82fc8157;hp=0471890230aa6a4d6256ce9a570ea4caeb4f4598;hpb=3f2b2eee8f46f2252d2919d7a57bf3068d7df285;p=rust.git

diff --git a/compiler/rustc_lint/src/unused.rs b/compiler/rustc_lint/src/unused.rs
index 0471890230a..43864ed45fa 100644
--- a/compiler/rustc_lint/src/unused.rs
+++ b/compiler/rustc_lint/src/unused.rs
@@ -258,8 +258,9 @@ fn is_ty_must_use<'tcx>(
                     )
                     .filter_map(|obligation| {
                         // We only look at the `DefId`, so it is safe to skip the binder here.
-                        if let ty::PredicateKind::Trait(ref poly_trait_predicate) =
-                            obligation.predicate.kind().skip_binder()
+                        if let ty::PredicateKind::Clause(ty::Clause::Trait(
+                            ref poly_trait_predicate,
+                        )) = obligation.predicate.kind().skip_binder()
                         {
                             let def_id = poly_trait_predicate.trait_ref.def_id;
 
@@ -319,7 +320,20 @@ fn is_ty_must_use<'tcx>(
                         .map(|inner| MustUsePath::Array(Box::new(inner), len)),
                 },
                 ty::Closure(..) => Some(MustUsePath::Closure(span)),
-                ty::Generator(..) => Some(MustUsePath::Generator(span)),
+                ty::Generator(def_id, ..) => {
+                    // async fn should be treated as "implementor of `Future`"
+                    let must_use = if matches!(
+                        cx.tcx.generator_kind(def_id),
+                        Some(hir::GeneratorKind::Async(..))
+                    ) {
+                        let def_id = cx.tcx.lang_items().future_trait().unwrap();
+                        is_def_must_use(cx, def_id, span)
+                            .map(|inner| MustUsePath::Opaque(Box::new(inner)))
+                    } else {
+                        None
+                    };
+                    must_use.or(Some(MustUsePath::Generator(span)))
+                }
                 _ => None,
             }
         }
@@ -1002,6 +1016,7 @@ fn check_ty(&mut self, cx: &EarlyContext<'_>, ty: &ast::Ty) {
         if let ast::TyKind::Paren(r) = &ty.kind {
             match &r.kind {
                 ast::TyKind::TraitObject(..) => {}
+                ast::TyKind::BareFn(b) if b.generic_params.len() > 0 => {}
                 ast::TyKind::ImplTrait(_, bounds) if bounds.len() > 1 => {}
                 ast::TyKind::Array(_, len) => {
                     self.check_unused_delims_expr(