Do not trigger if_let_mutex strating from Edition 2024

clippy_lints/src/if_let_mutex.rs

@@ -7,13 +7,20 @@ use rustc_errors::Diag;
 use rustc_hir::{Expr, ExprKind};
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_session::declare_lint_pass;
+use rustc_span::edition::Edition::Edition2024;
 use rustc_span::sym;
 
 declare_clippy_lint! {
     /// ### What it does
     /// Checks for `Mutex::lock` calls in `if let` expression
     /// with lock calls in any of the else blocks.
     ///
+    /// ### Disabled starting in Edition 2024
+    /// `Mutex::lock` is effectively disabled starting in
+    /// Edition 2024 as `if let ... else` scoping was reworked
+    /// such that this is no longer an issue. See
+    /// [Proposal: stabilize if_let_rescope for Edition 2024](https://github.com/rust-lang/rust/issues/131154)
+    ///
     /// ### Why is this bad?
     /// The Mutex lock remains held for the whole
     /// `if let ... else` block and deadlocks.
@@ -45,6 +52,10 @@ declare_lint_pass!(IfLetMutex => [IF_LET_MUTEX]);
 
 impl<'tcx> LateLintPass<'tcx> for IfLetMutex {
     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) {
+        if cx.tcx.sess.edition() >= Edition2024 {
+            return;
+        }
+
         if let Some(higher::IfLet {
             let_expr,
             if_then,

tests/ui/if_let_mutex.rs

@@ -1,3 +1,6 @@
+//@ compile-flags: -Zunstable-options
+
+//@edition:2024
 #![warn(clippy::if_let_mutex)]
 #![allow(clippy::redundant_pattern_matching)]
 
@@ -9,7 +12,6 @@ fn do_stuff<T>(_: T) {}
 fn if_let() {
     let m = Mutex::new(1_u8);
     if let Err(locked) = m.lock() {
-        //~^ ERROR: calling `Mutex::lock` inside the scope of another `Mutex::lock` causes a d
         do_stuff(locked);
     } else {
         let lock = m.lock().unwrap();
@@ -22,7 +24,6 @@ fn if_let() {
 fn if_let_option() {
     let m = Mutex::new(Some(0_u8));
     if let Some(locked) = m.lock().unwrap().deref() {
-        //~^ ERROR: calling `Mutex::lock` inside the scope of another `Mutex::lock` causes a d
         do_stuff(locked);
     } else {
         let lock = m.lock().unwrap();
@@ -44,7 +45,6 @@ fn if_let_different_mutex() {
 
 fn mutex_ref(mutex: &Mutex<i32>) {
     if let Ok(i) = mutex.lock() {
-        //~^ ERROR: calling `Mutex::lock` inside the scope of another `Mutex::lock` causes a d
         do_stuff(i);
     } else {
         let _x = mutex.lock();

tests/ui/if_let_mutex_2021.rs

@@ -0,0 +1,63 @@
+//@edition:2021
+#![warn(clippy::if_let_mutex)]
+#![allow(clippy::redundant_pattern_matching)]
+
+use std::ops::Deref;
+use std::sync::Mutex;
+
+fn do_stuff<T>(_: T) {}
+
+fn if_let() {
+    let m = Mutex::new(1_u8);
+    if let Err(locked) = m.lock() {
+        //~^ ERROR: calling `Mutex::lock` inside the scope of another `Mutex::lock` causes a d
+        do_stuff(locked);
+    } else {
+        let lock = m.lock().unwrap();
+        do_stuff(lock);
+    };
+}
+
+// This is the most common case as the above case is pretty
+// contrived.
+fn if_let_option() {
+    let m = Mutex::new(Some(0_u8));
+    if let Some(locked) = m.lock().unwrap().deref() {
+        //~^ ERROR: calling `Mutex::lock` inside the scope of another `Mutex::lock` causes a d
+        do_stuff(locked);
+    } else {
+        let lock = m.lock().unwrap();
+        do_stuff(lock);
+    };
+}
+
+// When mutexes are different don't warn
+fn if_let_different_mutex() {
+    let m = Mutex::new(Some(0_u8));
+    let other = Mutex::new(None::<u8>);
+    if let Some(locked) = m.lock().unwrap().deref() {
+        do_stuff(locked);
+    } else {
+        let lock = other.lock().unwrap();
+        do_stuff(lock);
+    };
+}
+
+fn mutex_ref(mutex: &Mutex<i32>) {
+    if let Ok(i) = mutex.lock() {
+        //~^ ERROR: calling `Mutex::lock` inside the scope of another `Mutex::lock` causes a d
+        do_stuff(i);
+    } else {
+        let _x = mutex.lock();
+    };
+}
+
+fn multiple_mutexes(m1: &Mutex<()>, m2: &Mutex<()>) {
+    if let Ok(_) = m1.lock() {
+        m2.lock();
+    } else {
+        m1.lock();
+    }
+}
+
+fn main() {}

tests/ui/if_let_mutex.stderr → tests/ui/if_let_mutex_2021.stderr

@@ -1,5 +1,5 @@
 error: calling `Mutex::lock` inside the scope of another `Mutex::lock` causes a deadlock
-  --> tests/ui/if_let_mutex.rs:11:5
+  --> tests/ui/if_let_mutex_2021.rs:12:5
    |
 LL |       if let Err(locked) = m.lock() {
    |       ^                    - this Mutex will remain locked for the entire `if let`-block...
@@ -19,7 +19,7 @@ LL | |     };
    = help: to override `-D warnings` add `#[allow(clippy::if_let_mutex)]`
 
 error: calling `Mutex::lock` inside the scope of another `Mutex::lock` causes a deadlock
-  --> tests/ui/if_let_mutex.rs:24:5
+  --> tests/ui/if_let_mutex_2021.rs:25:5
    |
 LL |       if let Some(locked) = m.lock().unwrap().deref() {
    |       ^                     - this Mutex will remain locked for the entire `if let`-block...
@@ -37,7 +37,7 @@ LL | |     };
    = help: move the lock call outside of the `if let ...` expression
 
 error: calling `Mutex::lock` inside the scope of another `Mutex::lock` causes a deadlock
-  --> tests/ui/if_let_mutex.rs:46:5
+  --> tests/ui/if_let_mutex_2021.rs:47:5
    |
 LL |       if let Ok(i) = mutex.lock() {
    |       ^              ----- this Mutex will remain locked for the entire `if let`-block...
@@ -54,7 +54,7 @@ LL | |     };
    = help: move the lock call outside of the `if let ...` expression
 
 error: calling `Mutex::lock` inside the scope of another `Mutex::lock` causes a deadlock
-  --> tests/ui/if_let_mutex.rs:55:5
+  --> tests/ui/if_let_mutex_2021.rs:56:5
    |
 LL |       if let Ok(_) = m1.lock() {
    |       ^              -- this Mutex will remain locked for the entire `if let`-block...