From ea173f9ca99701b148ae01bb768bdd01a29f7462 Mon Sep 17 00:00:00 2001
From: David Tolnay <dtolnay@gmail.com>
Date: Tue, 9 Nov 2021 20:26:05 -0800
Subject: [PATCH] Add ui test of sync bound

---
 tests/ui/non-sync.rs     | 21 +++++++++++++++++++++
 tests/ui/non-sync.stderr | 18 ++++++++++++++++++
 2 files changed, 39 insertions(+)
 create mode 100644 tests/ui/non-sync.rs
 create mode 100644 tests/ui/non-sync.stderr

diff --git a/tests/ui/non-sync.rs b/tests/ui/non-sync.rs
new file mode 100644
index 0000000..190655d
--- /dev/null
+++ b/tests/ui/non-sync.rs
@@ -0,0 +1,21 @@
+use std::rc::Rc;
+use std::thread;
+
+struct Thing(Rc<i32>);
+
+inventory::collect!(Thing);
+
+fn clone_all() {
+    for thing in inventory::iter::<Thing> {
+        let _ = Rc::clone(&thing.0);
+    }
+}
+
+fn main() {
+    // It would be bad if this were allowed. These threads would race on the
+    // nonatomic reference counts.
+    let thread1 = thread::spawn(clone_all);
+    let thread2 = thread::spawn(clone_all);
+    thread1.join().unwrap();
+    thread2.join().unwrap();
+}
diff --git a/tests/ui/non-sync.stderr b/tests/ui/non-sync.stderr
new file mode 100644
index 0000000..4eca860
--- /dev/null
+++ b/tests/ui/non-sync.stderr
@@ -0,0 +1,18 @@
+error[E0277]: `Rc<i32>` cannot be shared between threads safely
+   --> tests/ui/non-sync.rs:6:1
+    |
+6   | inventory::collect!(Thing);
+    | ^^^^^^^^^^^^^^^^^^^^^^^^^^ `Rc<i32>` cannot be shared between threads safely
+    |
+    = help: within `Thing`, the trait `Sync` is not implemented for `Rc<i32>`
+note: required because it appears within the type `Thing`
+   --> tests/ui/non-sync.rs:4:8
+    |
+4   | struct Thing(Rc<i32>);
+    |        ^^^^^
+note: required by a bound in `Collect`
+   --> src/lib.rs
+    |
+    | pub trait Collect: Sync + Sized + 'static {
+    |                    ^^^^ required by this bound in `Collect`
+    = note: this error originates in the macro `inventory::collect` (in Nightly builds, run with -Z macro-backtrace for more info)