From ead96f7f749846a2310e7aaedef0ea38fc7c3a4a Mon Sep 17 00:00:00 2001
From: Mara Bos <m-ou.se@m-ou.se>
Date: Wed, 19 Oct 2022 12:41:35 +0200
Subject: [PATCH] Allow #[unstable] impls for fn() with unstable abi.

---
 compiler/rustc_passes/src/stability.rs | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/compiler/rustc_passes/src/stability.rs b/compiler/rustc_passes/src/stability.rs
index cfd6acd8d7c..78591e640e3 100644
--- a/compiler/rustc_passes/src/stability.rs
+++ b/compiler/rustc_passes/src/stability.rs
@@ -888,10 +888,15 @@ impl<'tcx> Visitor<'tcx> for CheckTraitImplStable<'tcx> {
     }
 
     fn visit_ty(&mut self, t: &'tcx Ty<'tcx>) {
-        if let TyKind::Never = t.kind {
-            self.fully_stable = false;
+        match t.kind {
+            TyKind::Never => self.fully_stable = false,
+            TyKind::BareFn(f) => {
+                if rustc_target::spec::abi::is_stable(f.abi.name()).is_err() {
+                    self.fully_stable = false;
+                }
+            }
+            _ => intravisit::walk_ty(self, t),
         }
-        intravisit::walk_ty(self, t)
     }
 }