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Auto merge of #11104 - Alexendoo:arc-with-non-send-sync, r=Centri3

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`arc_with_non_send_sync`: reword and move to `suspicious`

Fixes #11079

changelog: [`arc_with_non_send_sync`]: move to complexity
This commit is contained in:
bors 2023-07-07 12:06:01 +00:00
commit 26edd5a2ab
3 changed files with 73 additions and 43 deletions
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71
clippy_lints/src/arc_with_non_send_sync.rs
View File

@ -1,12 +1,11 @@
use clippy_utils::diagnostics::span_lint_and_help;
use clippy_utils::diagnostics::span_lint_and_then;
use clippy_utils::last_path_segment;
use clippy_utils::ty::{implements_trait, is_type_diagnostic_item};
use if_chain::if_chain;
use rustc_hir::{Expr, ExprKind};
use rustc_lint::LateContext;
use rustc_lint::LateLintPass;
use rustc_middle::ty;
use rustc_middle::ty::print::with_forced_trimmed_paths;
use rustc_middle::ty::GenericArgKind;
use rustc_session::{declare_lint_pass, declare_tool_lint};
use rustc_span::symbol::sym;
@ -16,8 +15,8 @@
/// This lint warns when you use `Arc` with a type that does not implement `Send` or `Sync`.
///
/// ### Why is this bad?
/// Wrapping a type in Arc doesn't add thread safety to the underlying data, so data races
/// could occur when touching the underlying data.
/// `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),
/// either `T` should be made `Send + Sync` or an `Rc` should be used instead of an `Arc`
///
/// ### Example
/// ```rust
@ -25,16 +24,17 @@
/// # use std::sync::Arc;
///
/// fn main() {
/// // This is safe, as `i32` implements `Send` and `Sync`.
/// // This is fine, as `i32` implements `Send` and `Sync`.
/// let a = Arc::new(42);
///
/// // This is not safe, as `RefCell` does not implement `Sync`.
/// // `RefCell` is `!Sync`, so either the `Arc` should be replaced with an `Rc`
/// // or the `RefCell` replaced with something like a `RwLock`
/// let b = Arc::new(RefCell::new(42));
/// }
/// ```
#[clippy::version = "1.72.0"]
pub ARC_WITH_NON_SEND_SYNC,
correctness,
suspicious,
"using `Arc` with a type that does not implement `Send` or `Sync`"
}
declare_lint_pass!(ArcWithNonSendSync => [ARC_WITH_NON_SEND_SYNC]);
@ -42,35 +42,38 @@
impl LateLintPass<'_> for ArcWithNonSendSync {
fn check_expr(&mut self, cx: &LateContext<'_>, expr: &Expr<'_>) {
let ty = cx.typeck_results().expr_ty(expr);
if_chain! {
if is_type_diagnostic_item(cx, ty, sym::Arc);
if let ExprKind::Call(func, [arg]) = expr.kind;
if let ExprKind::Path(func_path) = func.kind;
if last_path_segment(&func_path).ident.name == sym::new;
if let arg_ty = cx.typeck_results().expr_ty(arg);
if is_type_diagnostic_item(cx, ty, sym::Arc)
&& let ExprKind::Call(func, [arg]) = expr.kind
&& let ExprKind::Path(func_path) = func.kind
&& last_path_segment(&func_path).ident.name == sym::new
&& let arg_ty = cx.typeck_results().expr_ty(arg)
// make sure that the type is not and does not contain any type parameters
if arg_ty.walk().all(|arg| {
&& arg_ty.walk().all(|arg| {
!matches!(arg.unpack(), GenericArgKind::Type(ty) if matches!(ty.kind(), ty::Param(_)))
});
if !cx.tcx
.lang_items()
.sync_trait()
.map_or(false, |id| implements_trait(cx, arg_ty, id, &[])) ||
!cx.tcx
.get_diagnostic_item(sym::Send)
.map_or(false, |id| implements_trait(cx, arg_ty, id, &[]));
})
&& let Some(send) = cx.tcx.get_diagnostic_item(sym::Send)
&& let Some(sync) = cx.tcx.lang_items().sync_trait()
&& let [is_send, is_sync] = [send, sync].map(|id| implements_trait(cx, arg_ty, id, &[]))
&& !(is_send && is_sync)
{
span_lint_and_then(
cx,
ARC_WITH_NON_SEND_SYNC,
expr.span,
"usage of an `Arc` that is not `Send` or `Sync`",
|diag| with_forced_trimmed_paths!({
if !is_send {
diag.note(format!("the trait `Send` is not implemented for `{arg_ty}`"));
}
if !is_sync {
diag.note(format!("the trait `Sync` is not implemented for `{arg_ty}`"));
}
then {
span_lint_and_help(
cx,
ARC_WITH_NON_SEND_SYNC,
expr.span,
"usage of `Arc<T>` where `T` is not `Send` or `Sync`",
None,
"consider using `Rc<T>` instead or wrapping `T` in a std::sync type like \
`Mutex<T>`",
);
}
diag.note(format!("required for `{ty}` to implement `Send` and `Sync`"));
diag.help("consider using an `Rc` instead or wrapping the inner type with a `Mutex`");
}
));
}
}
}

12
tests/ui/arc_with_non_send_sync.rs
View File

@ -12,9 +12,13 @@ fn issue11076<T>() {
}
fn main() {
// This is safe, as `i32` implements `Send` and `Sync`.
let a = Arc::new(42);
let _ = Arc::new(42);
// This is not safe, as `RefCell` does not implement `Sync`.
let b = Arc::new(RefCell::new(42));
// !Sync
let _ = Arc::new(RefCell::new(42));
let mutex = Mutex::new(1);
// !Send
let _ = Arc::new(mutex.lock().unwrap());
// !Send + !Sync
let _ = Arc::new(&42 as *const i32);
}

33
tests/ui/arc_with_non_send_sync.stderr
View File

@ -1,11 +1,34 @@
error: usage of `Arc<T>` where `T` is not `Send` or `Sync`
--> $DIR/arc_with_non_send_sync.rs:19:13
error: usage of an `Arc` that is not `Send` or `Sync`
--> $DIR/arc_with_non_send_sync.rs:18:13
|
LL | let b = Arc::new(RefCell::new(42));
LL | let _ = Arc::new(RefCell::new(42));
| ^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= help: consider using `Rc<T>` instead or wrapping `T` in a std::sync type like `Mutex<T>`
= note: the trait `Sync` is not implemented for `RefCell<i32>`
= note: required for `Arc<RefCell<i32>>` to implement `Send` and `Sync`
= help: consider using an `Rc` instead or wrapping the inner type with a `Mutex`
= note: `-D clippy::arc-with-non-send-sync` implied by `-D warnings`
error: aborting due to previous error
error: usage of an `Arc` that is not `Send` or `Sync`
--> $DIR/arc_with_non_send_sync.rs:21:13
|
LL | let _ = Arc::new(mutex.lock().unwrap());
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= note: the trait `Send` is not implemented for `MutexGuard<'_, i32>`
= note: required for `Arc<MutexGuard<'_, i32>>` to implement `Send` and `Sync`
= help: consider using an `Rc` instead or wrapping the inner type with a `Mutex`
error: usage of an `Arc` that is not `Send` or `Sync`
--> $DIR/arc_with_non_send_sync.rs:23:13
|
LL | let _ = Arc::new(&42 as *const i32);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= note: the trait `Send` is not implemented for `*const i32`
= note: the trait `Sync` is not implemented for `*const i32`
= note: required for `Arc<*const i32>` to implement `Send` and `Sync`
= help: consider using an `Rc` instead or wrapping the inner type with a `Mutex`
error: aborting due to 3 previous errors