1 files changed, 15 insertions, 0 deletions
diff --git a/src/test/ui/lint/opaque-ty-ffi-unsafe.rs b/src/test/ui/lint/opaque-ty-ffi-unsafe.rs
new file mode 100644
index 000000000..b7cc38e99
--- /dev/null
+++ b/src/test/ui/lint/opaque-ty-ffi-unsafe.rs
@@ -0,0 +1,15 @@
+#![feature(type_alias_impl_trait)]
+#![deny(improper_ctypes)]
+
+type A = impl Fn();
+
+pub fn ret_closure() -> A {
+    || {}
+}
+
+extern "C" {
+    pub fn a(_: A);
+    //~^ ERROR `extern` block uses type `A`, which is not FFI-safe [improper_ctypes]
+}
+
+fn main() {}