Merge pull request #36 from moka-rs/get-or-try-insert-tests

Add UI tests for `get_or_try_insert_with`

tests/ui/future/try_get_with_non_send_future.rs

@@ -0,0 +1,24 @@
+// https://github.com/moka-rs/moka/issues/31
+
+use moka::future::Cache;
+use std::rc::Rc;
+
+#[tokio::main]
+async fn main() {
+    let cache: Cache<_, String> = Cache::new(100);
+
+    // Rc is !Send.
+    let data = Rc::new("zero".to_string());
+    let data1 = Rc::clone(&data);
+
+    cache
+        .get_or_try_insert_with(0, async move {
+            // A data race may occur. 
+            // The async block can be executed by a different thread
+            // but Rc's internal reference counters are not thread safe.
+            Ok(data1.to_string())
+        })
+        .await;
+
+    println!("{:?}", data);
+}

tests/ui/future/try_get_with_non_send_future.stderr

@@ -0,0 +1,12 @@
+error: future cannot be sent between threads safely
+  --> $DIR/try_get_with_non_send_future.rs:15:10
+   |
+15 |         .get_or_try_insert_with(0, async move {
+   |          ^^^^^^^^^^^^^^^^^^^^^^ future created by async block is not `Send`
+   |
+   = help: within `impl Future`, the trait `Send` is not implemented for `Rc<String>`
+note: captured value is not `Send`
+  --> $DIR/try_get_with_non_send_future.rs:19:16
+   |
+19 |             Ok(data1.to_string())
+   |                ^^^^^ has type `Rc<String>` which is not `Send`

tests/ui/future/try_get_with_non_static_future.rs

@@ -0,0 +1,25 @@
+// https://github.com/moka-rs/moka/issues/31
+
+use moka::future::Cache;
+
+#[tokio::main]
+async fn main() {
+    let cache: Cache<_, String> = Cache::new(100);
+
+    let data = "zero".to_string();
+    {
+        // Not 'static.
+        let data_ref = &data;
+
+        cache
+            .get_or_try_insert_with(0, async {
+                // This may become a dangling pointer.
+                // The async block can be executed by a different thread so
+                // the captured reference `data_ref` may outlive its value.
+                Ok(data_ref.to_string())
+            })
+            .await;
+    }
+
+    println!("{:?}", data);
+}

tests/ui/future/try_get_with_non_static_future.stderr

@@ -0,0 +1,41 @@
+error[E0597]: `data` does not live long enough
+  --> $DIR/try_get_with_non_static_future.rs:12:24
+   |
+12 |           let data_ref = &data;
+   |                          ^^^^^ borrowed value does not live long enough
+...
+15 |               .get_or_try_insert_with(0, async {
+   |  ________________________________________-
+16 | |                 // This may become a dangling pointer.
+17 | |                 // The async block can be executed by a different thread so
+18 | |                 // the captured reference `data_ref` may outlive its value.
+19 | |                 Ok(data_ref.to_string())
+20 | |             })
+   | |_____________- argument requires that `data` is borrowed for `'static`
+...
+25 |   }
+   |   - `data` dropped here while still borrowed
+
+error[E0373]: async block may outlive the current function, but it borrows `data_ref`, which is owned by the current function
+  --> $DIR/try_get_with_non_static_future.rs:15:46
+   |
+15 |               .get_or_try_insert_with(0, async {
+   |  ______________________________________________^
+16 | |                 // This may become a dangling pointer.
+17 | |                 // The async block can be executed by a different thread so
+18 | |                 // the captured reference `data_ref` may outlive its value.
+19 | |                 Ok(data_ref.to_string())
+   | |                    -------- `data_ref` is borrowed here
+20 | |             })
+   | |_____________^ may outlive borrowed value `data_ref`
+   |
+   = note: async blocks are not executed immediately and must either take a reference or ownership of outside variables they use
+help: to force the async block to take ownership of `data_ref` (and any other referenced variables), use the `move` keyword
+   |
+15 |             .get_or_try_insert_with(0, async move {
+16 |                 // This may become a dangling pointer.
+17 |                 // The async block can be executed by a different thread so
+18 |                 // the captured reference `data_ref` may outlive its value.
+19 |                 Ok(data_ref.to_string())
+20 |             })
+   |