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 /// non-async-aware MutexGuard. /// /// **Why is this bad?** The Mutex types found in std::sync and parking_lot /// are not designed to operate in an async context across await points. /// /// There are two potential solutions. One is to use an asynx-aware Mutex /// type. Many asynchronous foundation crates provide such a Mutex type. The /// other solution is to ensure the mutex is unlocked before calling await, /// either by introducing a scope or an explicit call to Drop::drop. /// /// **Known problems:** None. /// /// **Example:** /// /// ```rust,ignore /// use std::sync::Mutex; /// /// async fn foo(x: &Mutex) { /// let guard = x.lock().unwrap(); /// *guard += 1; /// bar.await; /// } /// ``` /// /// Use instead: /// ```rust,ignore /// use std::sync::Mutex; /// /// async fn foo(x: &Mutex) { /// { /// let guard = x.lock().unwrap(); /// *guard += 1; /// } /// bar.await; /// } /// ``` pub AWAIT_HOLDING_LOCK, pedantic, "Inside an async function, holding a MutexGuard while calling await" } 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) { /// let mut y = x.borrow_mut(); /// *y += 1; /// bar.await; /// } /// ``` /// /// Use instead: /// ```rust,ignore /// use std::cell::RefCell; /// /// async fn foo(x: &RefCell) { /// { /// let mut y = x.borrow_mut(); /// *y += 1; /// } /// bar.await; /// } /// ``` pub AWAIT_HOLDING_REFCELL_REF, pedantic, "Inside an async function, holding a RefCell ref while calling await" } declare_lint_pass!(AwaitHolding => [AWAIT_HOLDING_LOCK, AWAIT_HOLDING_REFCELL_REF]); impl LateLintPass<'_> for AwaitHolding { 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.as_ref().skip_binder(), 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_mutex_guard(cx, adt.did) { span_lint_and_note( cx, AWAIT_HOLDING_LOCK, ty_cause.span, "this MutexGuard is held across an 'await' point. Consider using an async-aware Mutex type or ensuring the MutexGuard is dropped before calling await.", ty_cause.scope_span.or(Some(span)), "these are all the await points this lock is held through", ); } 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_mutex_guard(cx: &LateContext<'_>, def_id: DefId) -> bool { match_def_path(cx, def_id, &paths::MUTEX_GUARD) || match_def_path(cx, def_id, &paths::RWLOCK_READ_GUARD) || match_def_path(cx, def_id, &paths::RWLOCK_WRITE_GUARD) || match_def_path(cx, def_id, &paths::PARKING_LOT_MUTEX_GUARD) || match_def_path(cx, def_id, &paths::PARKING_LOT_RWLOCK_READ_GUARD) || match_def_path(cx, def_id, &paths::PARKING_LOT_RWLOCK_WRITE_GUARD) } 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) }