1 files changed, 13 insertions, 0 deletions

diff --git a/embassy-sync/tests/ui.rs b/embassy-sync/tests/ui.rs
new file mode 100644
index 000000000..9ef0d4c67
--- /dev/null
+++ b/embassy-sync/tests/ui.rs
@@ -0,0 +1,13 @@
+// #[cfg(not(miri))]
+#[test]
+fn ui() {
+    let t = trybuild::TestCases::new();
+
+    // These test cases should fail to compile since OnceLock and LazyLock should not unconditionally implement sync
+    // for all types. These tests are regression tests against the following issues:
+    // * https://github.com/embassy-rs/embassy/issues/4307
+    // * https://github.com/embassy-rs/embassy/issues/3904
+    t.compile_fail("tests/ui/sync_impl/lazy_lock_function.rs");
+    t.compile_fail("tests/ui/sync_impl/lazy_lock_type.rs");
+    t.compile_fail("tests/ui/sync_impl/once_lock.rs");
+}