Add lint for holding RefCell Ref across an await

This commit is contained in:
Daniel Smith 2020-09-10 15:53:36 -04:00
parent 74530adcba
commit 57bf80f776
5 changed files with 237 additions and 0 deletions

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@ -0,0 +1,83 @@
use crate::utils::{match_def_path, paths, span_lint_and_note};
use rustc_hir::def_id::DefId;
use rustc_hir::{AsyncGeneratorKind, Body, BodyId, GeneratorKind};
use rustc_lint::{LateContext, LateLintPass};
use rustc_middle::ty::GeneratorInteriorTypeCause;
use rustc_session::{declare_lint_pass, declare_tool_lint};
use rustc_span::Span;
declare_clippy_lint! {
/// **What it does:** Checks for calls to await while holding a
/// `RefCell` `Ref` or `RefMut`.
///
/// **Why is this bad?** `RefCell` refs only check for exclusive mutable access
/// at runtime. Holding onto a `RefCell` ref across an `await` suspension point
/// risks panics from a mutable ref shared while other refs are outstanding.
///
/// **Known problems:** None.
///
/// **Example:**
///
/// ```rust,ignore
/// use std::cell::RefCell;
///
/// async fn foo(x: &RefCell<u32>) {
/// let b = x.borrow_mut()();
/// *ref += 1;
/// bar.await;
/// }
/// ```
///
/// Use instead:
/// ```rust,ignore
/// use std::cell::RefCell;
///
/// async fn foo(x: &RefCell<u32>) {
/// {
/// let b = x.borrow_mut();
/// *ref += 1;
/// }
/// bar.await;
/// }
/// ```
pub AWAIT_HOLDING_REFCELL_REF,
pedantic,
"Inside an async function, holding a RefCell ref while calling await"
}
declare_lint_pass!(AwaitHoldingRefCellRef => [AWAIT_HOLDING_REFCELL_REF]);
impl LateLintPass<'_> for AwaitHoldingRefCellRef {
fn check_body(&mut self, cx: &LateContext<'_>, body: &'_ Body<'_>) {
use AsyncGeneratorKind::{Block, Closure, Fn};
if let Some(GeneratorKind::Async(Block | Closure | Fn)) = body.generator_kind {
let body_id = BodyId {
hir_id: body.value.hir_id,
};
let def_id = cx.tcx.hir().body_owner_def_id(body_id);
let typeck_results = cx.tcx.typeck(def_id);
check_interior_types(cx, &typeck_results.generator_interior_types, body.value.span);
}
}
}
fn check_interior_types(cx: &LateContext<'_>, ty_causes: &[GeneratorInteriorTypeCause<'_>], span: Span) {
for ty_cause in ty_causes {
if let rustc_middle::ty::Adt(adt, _) = ty_cause.ty.kind() {
if is_refcell_ref(cx, adt.did) {
span_lint_and_note(
cx,
AWAIT_HOLDING_REFCELL_REF,
ty_cause.span,
"this RefCell Ref is held across an 'await' point. Consider ensuring the Ref is dropped before calling await.",
ty_cause.scope_span.or(Some(span)),
"these are all the await points this ref is held through",
);
}
}
}
}
fn is_refcell_ref(cx: &LateContext<'_>, def_id: DefId) -> bool {
match_def_path(cx, def_id, &paths::REFCELL_REF) || match_def_path(cx, def_id, &paths::REFCELL_REFMUT)
}

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@ -161,6 +161,7 @@ mod async_yields_async;
mod atomic_ordering;
mod attrs;
mod await_holding_lock;
mod await_holding_refcell_ref;
mod bit_mask;
mod blacklisted_name;
mod blocks_in_if_conditions;
@ -510,6 +511,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
&attrs::UNKNOWN_CLIPPY_LINTS,
&attrs::USELESS_ATTRIBUTE,
&await_holding_lock::AWAIT_HOLDING_LOCK,
&await_holding_refcell_ref::AWAIT_HOLDING_REFCELL_REF,
&bit_mask::BAD_BIT_MASK,
&bit_mask::INEFFECTIVE_BIT_MASK,
&bit_mask::VERBOSE_BIT_MASK,
@ -906,6 +908,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
// end register lints, do not remove this comment, its used in `update_lints`
store.register_late_pass(|| box await_holding_lock::AwaitHoldingLock);
store.register_late_pass(|| box await_holding_refcell_ref::AwaitHoldingRefCellRef);
store.register_late_pass(|| box serde_api::SerdeAPI);
store.register_late_pass(|| box utils::internal_lints::CompilerLintFunctions::new());
store.register_late_pass(|| box utils::internal_lints::LintWithoutLintPass::default());
@ -1189,6 +1192,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
store.register_group(true, "clippy::pedantic", Some("clippy_pedantic"), vec![
LintId::of(&attrs::INLINE_ALWAYS),
LintId::of(&await_holding_lock::AWAIT_HOLDING_LOCK),
LintId::of(&await_holding_refcell_ref::AWAIT_HOLDING_REFCELL_REF),
LintId::of(&bit_mask::VERBOSE_BIT_MASK),
LintId::of(&checked_conversions::CHECKED_CONVERSIONS),
LintId::of(&copies::MATCH_SAME_ARMS),

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@ -93,6 +93,8 @@ pub const RANGE_ARGUMENT_TRAIT: [&str; 3] = ["core", "ops", "RangeBounds"];
pub const RC: [&str; 3] = ["alloc", "rc", "Rc"];
pub const RC_PTR_EQ: [&str; 4] = ["alloc", "rc", "Rc", "ptr_eq"];
pub const RECEIVER: [&str; 4] = ["std", "sync", "mpsc", "Receiver"];
pub const REFCELL_REF: [&str; 3] = ["core", "cell", "Ref"];
pub const REFCELL_REFMUT: [&str; 3] = ["core", "cell", "RefMut"];
pub const REGEX_BUILDER_NEW: [&str; 5] = ["regex", "re_builder", "unicode", "RegexBuilder", "new"];
pub const REGEX_BYTES_BUILDER_NEW: [&str; 5] = ["regex", "re_builder", "bytes", "RegexBuilder", "new"];
pub const REGEX_BYTES_NEW: [&str; 4] = ["regex", "re_bytes", "Regex", "new"];

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@ -0,0 +1,71 @@
// edition:2018
#![warn(clippy::await_holding_refcell_ref)]
use std::cell::RefCell;
async fn bad(x: &RefCell<u32>) -> u32 {
let b = x.borrow();
baz().await
}
async fn bad_mut(x: &RefCell<u32>) -> u32 {
let b = x.borrow_mut();
baz().await
}
async fn good(x: &RefCell<u32>) -> u32 {
{
let b = x.borrow_mut();
let y = *b + 1;
}
baz().await;
let b = x.borrow_mut();
47
}
async fn baz() -> u32 {
42
}
async fn also_bad(x: &RefCell<u32>) -> u32 {
let first = baz().await;
let b = x.borrow_mut();
let second = baz().await;
let third = baz().await;
first + second + third
}
async fn not_good(x: &RefCell<u32>) -> u32 {
let first = baz().await;
let second = {
let b = x.borrow_mut();
baz().await
};
let third = baz().await;
first + second + third
}
#[allow(clippy::manual_async_fn)]
fn block_bad(x: &RefCell<u32>) -> impl std::future::Future<Output = u32> + '_ {
async move {
let b = x.borrow_mut();
baz().await
}
}
fn main() {
let m = RefCell::new(100);
good(&m);
bad(&m);
bad_mut(&m);
also_bad(&m);
not_good(&m);
block_bad(&m);
}

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@ -0,0 +1,77 @@
error: this RefCell Ref is held across an 'await' point. Consider ensuring the Ref is dropped before calling await.
--> $DIR/await_holding_refcell_ref.rs:7:9
|
LL | let b = x.borrow();
| ^
|
= note: `-D clippy::await-holding-refcell-ref` implied by `-D warnings`
note: these are all the await points this ref is held through
--> $DIR/await_holding_refcell_ref.rs:7:5
|
LL | / let b = x.borrow();
LL | | baz().await
LL | | }
| |_^
error: this RefCell Ref is held across an 'await' point. Consider ensuring the Ref is dropped before calling await.
--> $DIR/await_holding_refcell_ref.rs:12:9
|
LL | let b = x.borrow_mut();
| ^
|
note: these are all the await points this ref is held through
--> $DIR/await_holding_refcell_ref.rs:12:5
|
LL | / let b = x.borrow_mut();
LL | | baz().await
LL | | }
| |_^
error: this RefCell Ref is held across an 'await' point. Consider ensuring the Ref is dropped before calling await.
--> $DIR/await_holding_refcell_ref.rs:33:9
|
LL | let b = x.borrow_mut();
| ^
|
note: these are all the await points this ref is held through
--> $DIR/await_holding_refcell_ref.rs:33:5
|
LL | / let b = x.borrow_mut();
LL | |
LL | | let second = baz().await;
LL | |
... |
LL | | first + second + third
LL | | }
| |_^
error: this RefCell Ref is held across an 'await' point. Consider ensuring the Ref is dropped before calling await.
--> $DIR/await_holding_refcell_ref.rs:46:13
|
LL | let b = x.borrow_mut();
| ^
|
note: these are all the await points this ref is held through
--> $DIR/await_holding_refcell_ref.rs:46:9
|
LL | / let b = x.borrow_mut();
LL | | baz().await
LL | | };
| |_____^
error: this RefCell Ref is held across an 'await' point. Consider ensuring the Ref is dropped before calling await.
--> $DIR/await_holding_refcell_ref.rs:58:13
|
LL | let b = x.borrow_mut();
| ^
|
note: these are all the await points this ref is held through
--> $DIR/await_holding_refcell_ref.rs:58:9
|
LL | / let b = x.borrow_mut();
LL | | baz().await
LL | | }
| |_____^
error: aborting due to 5 previous errors