Move last remaining Rc test to alloctests

Author: bjorn3

library/alloc/src/rc/mod.rs library/alloc/src/rc.rs

@@ -276,9 +276,6 @@ use crate::string::String;
 #[cfg(not(no_global_oom_handling))]
 use crate::vec::Vec;
 
-#[cfg(test)]
-mod tests;
-
 // This is repr(C) to future-proof against possible field-reordering, which
 // would interfere with otherwise safe [into|from]_raw() of transmutable
 // inner types.

library/alloc/src/rc/tests.rs

@@ -315,6 +315,24 @@ fn weak_self_cyclic() {
     // hopefully we don't double-free (or leak)...
 }
 
+#[test]
+fn is_unique() {
+    fn is_unique<T>(this: &Rc<T>) -> bool {
+        Rc::weak_count(this) == 0 && Rc::strong_count(this) == 1
+    }
+
+    let x = Rc::new(3);
+    assert!(is_unique(&x));
+    let y = x.clone();
+    assert!(!is_unique(&x));
+    drop(y);
+    assert!(is_unique(&x));
+    let w = Rc::downgrade(&x);
+    assert!(!is_unique(&x));
+    drop(w);
+    assert!(is_unique(&x));
+}
+
 #[test]
 fn test_strong_count() {
     let a = Rc::new(0);