From b973eb94a52630da5606b44272b89198f60968cc Mon Sep 17 00:00:00 2001
From: Emmanuel Ugwu <emmanuelugwu121@gmail.com>
Date: Mon, 22 Jun 2026 19:02:02 +0100
Subject: [PATCH 1/2] Allow unstable attribute on foreign types and add
 stability test

---
 compiler/rustc_attr_parsing/src/attributes/stability.rs | 1 +
 tests/ui/lint/lint-stability.rs                         | 6 +++++-
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/compiler/rustc_attr_parsing/src/attributes/stability.rs b/compiler/rustc_attr_parsing/src/attributes/stability.rs
index b38bb6d535770..734acb9ea21e7 100644
--- a/compiler/rustc_attr_parsing/src/attributes/stability.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/stability.rs
@@ -40,6 +40,7 @@ const ALLOWED_TARGETS: AllowedTargets = AllowedTargets::AllowList(&[
     Allow(Target::Static),
     Allow(Target::ForeignFn),
     Allow(Target::ForeignStatic),
+    Allow(Target::ForeignTy),
     Allow(Target::ExternCrate),
 ]);
 
diff --git a/tests/ui/lint/lint-stability.rs b/tests/ui/lint/lint-stability.rs
index f080b5e4bbeb1..21009b1e61db4 100644
--- a/tests/ui/lint/lint-stability.rs
+++ b/tests/ui/lint/lint-stability.rs
@@ -6,9 +6,13 @@
 #![allow(deprecated)]
 #![allow(dead_code)]
 #![feature(staged_api)]
-
+#![feature(extern_types)]
 #![stable(feature = "rust1", since = "1.0.0")]
 
+extern "C" {
+    #[unstable(feature = "fn_static", issue = "none")]
+    type Ty;
+}
 #[macro_use]
 extern crate lint_stability;
 

From 2592b4176d62f5310957cc5595d2ab0747326d3c Mon Sep 17 00:00:00 2001
From: Emmanuel Ugwu <emmanuelugwu121@gmail.com>
Date: Fri, 26 Jun 2026 22:34:26 +0100
Subject: [PATCH 2/2] Add test to confirm usage of unstable foreign type error

Signed-off-by: Emmanuel Ugwu <emmanuelugwu121@gmail.com>
---
 tests/ui/lint/auxiliary/lint_stability.rs | 6 ++++++
 tests/ui/lint/lint-stability.rs           | 7 +++----
 2 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/tests/ui/lint/auxiliary/lint_stability.rs b/tests/ui/lint/auxiliary/lint_stability.rs
index 99c29dcdda677..bc2d47aebbc29 100644
--- a/tests/ui/lint/auxiliary/lint_stability.rs
+++ b/tests/ui/lint/auxiliary/lint_stability.rs
@@ -1,5 +1,6 @@
 #![crate_name="lint_stability"]
 #![crate_type = "lib"]
+#![feature(extern_types)]
 #![feature(staged_api)]
 #![feature(associated_type_defaults)]
 #![stable(feature = "lint_stability", since = "1.0.0")]
@@ -186,3 +187,8 @@ macro_rules! macro_test_arg {
 macro_rules! macro_test_arg_nested {
     ($func:ident) => (macro_test_arg!($func()));
 }
+
+extern "C" {
+    #[unstable(feature = "unstable_test_feature", issue = "none")]
+    pub type UnstableForeignType;
+}
diff --git a/tests/ui/lint/lint-stability.rs b/tests/ui/lint/lint-stability.rs
index 21009b1e61db4..c8712397189c7 100644
--- a/tests/ui/lint/lint-stability.rs
+++ b/tests/ui/lint/lint-stability.rs
@@ -9,10 +9,6 @@
 #![feature(extern_types)]
 #![stable(feature = "rust1", since = "1.0.0")]
 
-extern "C" {
-    #[unstable(feature = "fn_static", issue = "none")]
-    type Ty;
-}
 #[macro_use]
 extern crate lint_stability;
 
@@ -22,6 +18,9 @@ mod cross_crate {
 
     use lint_stability::*;
 
+    fn test_foreign_type(_: &mut UnstableForeignType) { //~ ERROR use of unstable library feature
+    }
+
     fn test() {
         type Foo = MethodTester;
         let foo = MethodTester;