1 use crate::utils::{span_lint_and_help, SpanlessEq};
2 use clippy_utils::ty::is_type_diagnostic_item;
3 use if_chain::if_chain;
4 use rustc_hir::intravisit::{self as visit, NestedVisitorMap, Visitor};
5 use rustc_hir::{Expr, ExprKind, MatchSource};
6 use rustc_lint::{LateContext, LateLintPass};
7 use rustc_middle::hir::map::Map;
8 use rustc_session::{declare_lint_pass, declare_tool_lint};
10 declare_clippy_lint! {
11 /// **What it does:** Checks for `Mutex::lock` calls in `if let` expression
12 /// with lock calls in any of the else blocks.
14 /// **Why is this bad?** The Mutex lock remains held for the whole
15 /// `if let ... else` block and deadlocks.
17 /// **Known problems:** None.
22 /// if let Ok(thing) = mutex.lock() {
30 /// let locked = mutex.lock();
31 /// if let Ok(thing) = locked {
34 /// use_locked(locked);
39 "locking a `Mutex` in an `if let` block can cause deadlocks"
42 declare_lint_pass!(IfLetMutex => [IF_LET_MUTEX]);
44 impl<'tcx> LateLintPass<'tcx> for IfLetMutex {
45 fn check_expr(&mut self, cx: &LateContext<'tcx>, ex: &'tcx Expr<'tcx>) {
46 let mut arm_visit = ArmVisitor {
47 mutex_lock_called: false,
51 let mut op_visit = OppVisitor {
52 mutex_lock_called: false,
56 if let ExprKind::Match(
59 MatchSource::IfLetDesugar {
60 contains_else_clause: true,
64 op_visit.visit_expr(op);
65 if op_visit.mutex_lock_called {
67 arm_visit.visit_arm(arm);
70 if arm_visit.mutex_lock_called && arm_visit.same_mutex(cx, op_visit.found_mutex.unwrap()) {
75 "calling `Mutex::lock` inside the scope of another `Mutex::lock` causes a deadlock",
77 "move the lock call outside of the `if let ...` expression",
85 /// Checks if `Mutex::lock` is called in the `if let _ = expr.
86 pub struct OppVisitor<'a, 'tcx> {
87 mutex_lock_called: bool,
88 found_mutex: Option<&'tcx Expr<'tcx>>,
89 cx: &'a LateContext<'tcx>,
92 impl<'tcx> Visitor<'tcx> for OppVisitor<'_, 'tcx> {
95 fn visit_expr(&mut self, expr: &'tcx Expr<'_>) {
97 if let Some(mutex) = is_mutex_lock_call(self.cx, expr);
99 self.found_mutex = Some(mutex);
100 self.mutex_lock_called = true;
104 visit::walk_expr(self, expr);
107 fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
108 NestedVisitorMap::None
112 /// Checks if `Mutex::lock` is called in any of the branches.
113 pub struct ArmVisitor<'a, 'tcx> {
114 mutex_lock_called: bool,
115 found_mutex: Option<&'tcx Expr<'tcx>>,
116 cx: &'a LateContext<'tcx>,
119 impl<'tcx> Visitor<'tcx> for ArmVisitor<'_, 'tcx> {
120 type Map = Map<'tcx>;
122 fn visit_expr(&mut self, expr: &'tcx Expr<'tcx>) {
124 if let Some(mutex) = is_mutex_lock_call(self.cx, expr);
126 self.found_mutex = Some(mutex);
127 self.mutex_lock_called = true;
131 visit::walk_expr(self, expr);
134 fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
135 NestedVisitorMap::None
139 impl<'tcx, 'l> ArmVisitor<'tcx, 'l> {
140 fn same_mutex(&self, cx: &LateContext<'_>, op_mutex: &Expr<'_>) -> bool {
142 .map_or(false, |arm_mutex| SpanlessEq::new(cx).eq_expr(op_mutex, arm_mutex))
146 fn is_mutex_lock_call<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) -> Option<&'tcx Expr<'tcx>> {
148 if let ExprKind::MethodCall(path, _span, args, _) = &expr.kind;
149 if path.ident.as_str() == "lock";
150 let ty = cx.typeck_results().expr_ty(&args[0]);
151 if is_type_diagnostic_item(cx, ty, sym!(mutex_type));