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Auto merge of #11772 - partiallytyped:11714, r=blyxyas

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[arc_with_non_send_sync] Improve suggested resolution

Fixes: #11714

Improved the lint message for [`arc_with_non_send_sync`] to suggest using `RC` unless user needs an Arc, then suggests wrapping in a mutex, and then suggests implementing `Sync` and `Send`.

---

changelog: [`arc_with_non_send_sync`]: Suggest RC over unsafe impl of Send and Sync
This commit is contained in:
bors 2023-11-08 20:30:02 +00:00
commit e16d42f540
3 changed files with 37 additions and 23 deletions
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22
clippy_lints/src/arc_with_non_send_sync.rs
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@ -14,7 +14,9 @@
/// This lint warns when you use `Arc` with a type that does not implement `Send` or `Sync`. /// This lint warns when you use `Arc` with a type that does not implement `Send` or `Sync`.
/// ///
/// ### Why is this bad? /// ### Why is this bad?
/// `Arc<T>` is only `Send`/`Sync` when `T` is [both `Send` and `Sync`](https://doc.rust-lang.org/std/sync/struct.Arc.html#impl-Send-for-Arc%3CT%3E), /// `Arc<T>` is an Atomic `RC<T>` and guarantees that updates to the reference counter are
/// Atomic. This is useful in multiprocessing scenarios. To send an `Arc<T>` across processes
/// and make use of the atomic ref counter, `T` must be [both `Send` and `Sync`](https://doc.rust-lang.org/std/sync/struct.Arc.html#impl-Send-for-Arc%3CT%3E),
/// either `T` should be made `Send + Sync` or an `Rc` should be used instead of an `Arc` /// either `T` should be made `Send + Sync` or an `Rc` should be used instead of an `Arc`
/// ///
/// ### Example /// ### Example
@ -34,7 +36,7 @@
#[clippy::version = "1.72.0"] #[clippy::version = "1.72.0"]
pub ARC_WITH_NON_SEND_SYNC, pub ARC_WITH_NON_SEND_SYNC,
suspicious, suspicious,
"using `Arc` with a type that does not implement `Send` or `Sync`" "using `Arc` with a type that does not implement `Send` and `Sync`"
} }
declare_lint_pass!(ArcWithNonSendSync => [ARC_WITH_NON_SEND_SYNC]); declare_lint_pass!(ArcWithNonSendSync => [ARC_WITH_NON_SEND_SYNC]);
@ -61,19 +63,25 @@ fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) {
cx, cx,
ARC_WITH_NON_SEND_SYNC, ARC_WITH_NON_SEND_SYNC,
expr.span, expr.span,
"usage of an `Arc` that is not `Send` or `Sync`", "usage of an `Arc` that is not `Send` and `Sync`",
|diag| { |diag| {
with_forced_trimmed_paths!({ with_forced_trimmed_paths!({
diag.note(format!("`Arc<{arg_ty}>` is not `Send` and `Sync` as:"));
if !is_send { if !is_send {
diag.note(format!("the trait `Send` is not implemented for `{arg_ty}`")); diag.note(format!("- the trait `Send` is not implemented for `{arg_ty}`"));
} }
if !is_sync { if !is_sync {
diag.note(format!("the trait `Sync` is not implemented for `{arg_ty}`")); diag.note(format!("- the trait `Sync` is not implemented for `{arg_ty}`"));
} }
diag.note(format!("required for `{ty}` to implement `Send` and `Sync`")); diag.help("consider using an `Rc` instead. `Arc` does not provide benefits for non `Send` and `Sync` types");
diag.help("consider using an `Rc` instead or wrapping the inner type with a `Mutex`"); diag.note("if you intend to use `Arc` with `Send` and `Sync` traits");
diag.note(format!(
"wrap the inner type with a `Mutex` or implement `Send` and `Sync` for `{arg_ty}`"
));
}); });
}, },
); );

6
tests/ui/arc_with_non_send_sync.rs
View File

@ -33,16 +33,16 @@ fn main() {
let _ = Arc::new(42); let _ = Arc::new(42);
let _ = Arc::new(RefCell::new(42)); let _ = Arc::new(RefCell::new(42));
//~^ ERROR: usage of an `Arc` that is not `Send` or `Sync` //~^ ERROR: usage of an `Arc` that is not `Send` and `Sync`
//~| NOTE: the trait `Sync` is not implemented for `RefCell<i32>` //~| NOTE: the trait `Sync` is not implemented for `RefCell<i32>`
let mutex = Mutex::new(1); let mutex = Mutex::new(1);
let _ = Arc::new(mutex.lock().unwrap()); let _ = Arc::new(mutex.lock().unwrap());
//~^ ERROR: usage of an `Arc` that is not `Send` or `Sync` //~^ ERROR: usage of an `Arc` that is not `Send` and `Sync`
//~| NOTE: the trait `Send` is not implemented for `MutexGuard<'_, i32>` //~| NOTE: the trait `Send` is not implemented for `MutexGuard<'_, i32>`
let _ = Arc::new(&42 as *const i32); let _ = Arc::new(&42 as *const i32);
//~^ ERROR: usage of an `Arc` that is not `Send` or `Sync` //~^ ERROR: usage of an `Arc` that is not `Send` and `Sync`
//~| NOTE: the trait `Send` is not implemented for `*const i32` //~| NOTE: the trait `Send` is not implemented for `*const i32`
//~| NOTE: the trait `Sync` is not implemented for `*const i32` //~| NOTE: the trait `Sync` is not implemented for `*const i32`
} }

32
tests/ui/arc_with_non_send_sync.stderr
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@ -1,35 +1,41 @@
error: usage of an `Arc` that is not `Send` or `Sync` error: usage of an `Arc` that is not `Send` and `Sync`
--> $DIR/arc_with_non_send_sync.rs:35:13 --> $DIR/arc_with_non_send_sync.rs:35:13
| |
LL | let _ = Arc::new(RefCell::new(42)); LL | let _ = Arc::new(RefCell::new(42));
| ^^^^^^^^^^^^^^^^^^^^^^^^^^ | ^^^^^^^^^^^^^^^^^^^^^^^^^^
| |
= note: the trait `Sync` is not implemented for `RefCell<i32>` = note: `Arc<RefCell<i32>>` is not `Send` and `Sync` as:
= note: required for `Arc<RefCell<i32>>` to implement `Send` and `Sync` = note: - the trait `Sync` is not implemented for `RefCell<i32>`
= help: consider using an `Rc` instead or wrapping the inner type with a `Mutex` = help: consider using an `Rc` instead. `Arc` does not provide benefits for non `Send` and `Sync` types
= note: if you intend to use `Arc` with `Send` and `Sync` traits
= note: wrap the inner type with a `Mutex` or implement `Send` and `Sync` for `RefCell<i32>`
= note: `-D clippy::arc-with-non-send-sync` implied by `-D warnings` = note: `-D clippy::arc-with-non-send-sync` implied by `-D warnings`
= help: to override `-D warnings` add `#[allow(clippy::arc_with_non_send_sync)]` = help: to override `-D warnings` add `#[allow(clippy::arc_with_non_send_sync)]`
error: usage of an `Arc` that is not `Send` or `Sync` error: usage of an `Arc` that is not `Send` and `Sync`
--> $DIR/arc_with_non_send_sync.rs:40:13 --> $DIR/arc_with_non_send_sync.rs:40:13
| |
LL | let _ = Arc::new(mutex.lock().unwrap()); LL | let _ = Arc::new(mutex.lock().unwrap());
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
| |
= note: the trait `Send` is not implemented for `MutexGuard<'_, i32>` = note: `Arc<MutexGuard<'_, i32>>` is not `Send` and `Sync` as:
= note: required for `Arc<MutexGuard<'_, i32>>` to implement `Send` and `Sync` = note: - the trait `Send` is not implemented for `MutexGuard<'_, i32>`
= help: consider using an `Rc` instead or wrapping the inner type with a `Mutex` = help: consider using an `Rc` instead. `Arc` does not provide benefits for non `Send` and `Sync` types
= note: if you intend to use `Arc` with `Send` and `Sync` traits
= note: wrap the inner type with a `Mutex` or implement `Send` and `Sync` for `MutexGuard<'_, i32>`
error: usage of an `Arc` that is not `Send` or `Sync` error: usage of an `Arc` that is not `Send` and `Sync`
--> $DIR/arc_with_non_send_sync.rs:44:13 --> $DIR/arc_with_non_send_sync.rs:44:13
| |
LL | let _ = Arc::new(&42 as *const i32); LL | let _ = Arc::new(&42 as *const i32);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^
| |
= note: the trait `Send` is not implemented for `*const i32` = note: `Arc<*const i32>` is not `Send` and `Sync` as:
= note: the trait `Sync` is not implemented for `*const i32` = note: - the trait `Send` is not implemented for `*const i32`
= note: required for `Arc<*const i32>` to implement `Send` and `Sync` = note: - the trait `Sync` is not implemented for `*const i32`
= help: consider using an `Rc` instead or wrapping the inner type with a `Mutex` = help: consider using an `Rc` instead. `Arc` does not provide benefits for non `Send` and `Sync` types
= note: if you intend to use `Arc` with `Send` and `Sync` traits
= note: wrap the inner type with a `Mutex` or implement `Send` and `Sync` for `*const i32`
error: aborting due to 3 previous errors error: aborting due to 3 previous errors