1 use clippy_utils::diagnostics::span_lint_and_help;
2 use clippy_utils::ty::is_type_diagnostic_item;
3 use clippy_utils::SpanlessEq;
4 use if_chain::if_chain;
5 use rustc_hir::intravisit::{self as visit, NestedVisitorMap, Visitor};
6 use rustc_hir::{Expr, ExprKind, MatchSource};
7 use rustc_lint::{LateContext, LateLintPass};
8 use rustc_middle::hir::map::Map;
9 use rustc_session::{declare_lint_pass, declare_tool_lint};
11 declare_clippy_lint! {
12 /// **What it does:** Checks for `Mutex::lock` calls in `if let` expression
13 /// with lock calls in any of the else blocks.
15 /// **Why is this bad?** The Mutex lock remains held for the whole
16 /// `if let ... else` block and deadlocks.
18 /// **Known problems:** None.
23 /// if let Ok(thing) = mutex.lock() {
31 /// let locked = mutex.lock();
32 /// if let Ok(thing) = locked {
35 /// use_locked(locked);
40 "locking a `Mutex` in an `if let` block can cause deadlocks"
43 declare_lint_pass!(IfLetMutex => [IF_LET_MUTEX]);
45 impl<'tcx> LateLintPass<'tcx> for IfLetMutex {
46 fn check_expr(&mut self, cx: &LateContext<'tcx>, ex: &'tcx Expr<'tcx>) {
47 let mut arm_visit = ArmVisitor {
48 mutex_lock_called: false,
52 let mut op_visit = OppVisitor {
53 mutex_lock_called: false,
57 if let ExprKind::Match(
60 MatchSource::IfLetDesugar {
61 contains_else_clause: true,
65 op_visit.visit_expr(op);
66 if op_visit.mutex_lock_called {
68 arm_visit.visit_arm(arm);
71 if arm_visit.mutex_lock_called && arm_visit.same_mutex(cx, op_visit.found_mutex.unwrap()) {
76 "calling `Mutex::lock` inside the scope of another `Mutex::lock` causes a deadlock",
78 "move the lock call outside of the `if let ...` expression",
86 /// Checks if `Mutex::lock` is called in the `if let` expr.
87 pub struct OppVisitor<'a, 'tcx> {
88 mutex_lock_called: bool,
89 found_mutex: Option<&'tcx Expr<'tcx>>,
90 cx: &'a LateContext<'tcx>,
93 impl<'tcx> Visitor<'tcx> for OppVisitor<'_, 'tcx> {
96 fn visit_expr(&mut self, expr: &'tcx Expr<'_>) {
97 if let Some(mutex) = is_mutex_lock_call(self.cx, expr) {
98 self.found_mutex = Some(mutex);
99 self.mutex_lock_called = true;
102 visit::walk_expr(self, expr);
105 fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
106 NestedVisitorMap::None
110 /// Checks if `Mutex::lock` is called in any of the branches.
111 pub struct ArmVisitor<'a, 'tcx> {
112 mutex_lock_called: bool,
113 found_mutex: Option<&'tcx Expr<'tcx>>,
114 cx: &'a LateContext<'tcx>,
117 impl<'tcx> Visitor<'tcx> for ArmVisitor<'_, 'tcx> {
118 type Map = Map<'tcx>;
120 fn visit_expr(&mut self, expr: &'tcx Expr<'tcx>) {
121 if let Some(mutex) = is_mutex_lock_call(self.cx, expr) {
122 self.found_mutex = Some(mutex);
123 self.mutex_lock_called = true;
126 visit::walk_expr(self, expr);
129 fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
130 NestedVisitorMap::None
134 impl<'tcx, 'l> ArmVisitor<'tcx, 'l> {
135 fn same_mutex(&self, cx: &LateContext<'_>, op_mutex: &Expr<'_>) -> bool {
137 .map_or(false, |arm_mutex| SpanlessEq::new(cx).eq_expr(op_mutex, arm_mutex))
141 fn is_mutex_lock_call<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) -> Option<&'tcx Expr<'tcx>> {
143 if let ExprKind::MethodCall(path, _span, args, _) = &expr.kind;
144 if path.ident.as_str() == "lock";
145 let ty = cx.typeck_results().expr_ty(&args[0]);
146 if is_type_diagnostic_item(cx, ty, sym!(mutex_type));