Fix let_undescore_lock false-positive when binding without locking

Signed-off-by: Klim Tsoutsman <klimusha@gmail.com>

Author: tsoutsman

clippy_lints/src/let_underscore.rs

@@ -99,12 +99,13 @@ declare_clippy_lint! {
 
 declare_lint_pass!(LetUnderscore => [LET_UNDERSCORE_MUST_USE, LET_UNDERSCORE_LOCK, LET_UNDERSCORE_DROP]);
 
-const SYNC_GUARD_PATHS: [&[&str]; 5] = [
+const SYNC_GUARD_PATHS: [&[&str]; 6] = [
     &paths::MUTEX_GUARD,
     &paths::RWLOCK_READ_GUARD,
     &paths::RWLOCK_WRITE_GUARD,
-    &paths::PARKING_LOT_RAWMUTEX,
-    &paths::PARKING_LOT_RAWRWLOCK,
+    &paths::PARKING_LOT_MUTEX_GUARD,
+    &paths::PARKING_LOT_RWLOCK_READ_GUARD,
+    &paths::PARKING_LOT_RWLOCK_WRITE_GUARD,
 ];
 
 impl<'tcx> LateLintPass<'tcx> for LetUnderscore {

clippy_utils/src/paths.rs

@@ -84,8 +84,6 @@ pub const OPTION_SOME: [&str; 4] = ["core", "option", "Option", "Some"];
 pub const ORD: [&str; 3] = ["core", "cmp", "Ord"];
 pub const OS_STRING_AS_OS_STR: [&str; 5] = ["std", "ffi", "os_str", "OsString", "as_os_str"];
 pub const OS_STR_TO_OS_STRING: [&str; 5] = ["std", "ffi", "os_str", "OsStr", "to_os_string"];
-pub const PARKING_LOT_RAWMUTEX: [&str; 3] = ["parking_lot", "raw_mutex", "RawMutex"];
-pub const PARKING_LOT_RAWRWLOCK: [&str; 3] = ["parking_lot", "raw_rwlock", "RawRwLock"];
 pub const PARKING_LOT_MUTEX_GUARD: [&str; 3] = ["lock_api", "mutex", "MutexGuard"];
 pub const PARKING_LOT_RWLOCK_READ_GUARD: [&str; 3] = ["lock_api", "rwlock", "RwLockReadGuard"];
 pub const PARKING_LOT_RWLOCK_WRITE_GUARD: [&str; 3] = ["lock_api", "rwlock", "RwLockWriteGuard"];

tests/ui/let_underscore_lock.rs

@@ -13,6 +13,10 @@ fn main() {
     let _ = rw.try_read();
     let _ = rw.try_write();
 
+    // These shouldn't throw an error.
+    let _ = m;
+    let _ = rw;
+
     use parking_lot::{lock_api::RawMutex, Mutex, RwLock};
 
     let p_m: Mutex<()> = Mutex::const_new(RawMutex::INIT, ());
@@ -24,4 +28,9 @@ fn main() {
     let p_rw = RwLock::new(0);
     let _ = p_rw.read();
     let _ = p_rw.write();
+
+    // These shouldn't throw an error.
+    let _ = p_m;
+    let _ = p_m1;
+    let _ = p_rw;
 }

tests/ui/let_underscore_lock.stderr

@@ -48,31 +48,31 @@ LL |     let _ = rw.try_write();
    = help: consider using an underscore-prefixed named binding or dropping explicitly with `std::mem::drop`
 
 error: non-binding let on a synchronization lock
-  --> $DIR/let_underscore_lock.rs:19:5
+  --> $DIR/let_underscore_lock.rs:23:5
    |
 LL |     let _ = p_m.lock();
    |     ^^^^^^^^^^^^^^^^^^^
    |
    = help: consider using an underscore-prefixed named binding or dropping explicitly with `std::mem::drop`
 
 error: non-binding let on a synchronization lock
-  --> $DIR/let_underscore_lock.rs:22:5
+  --> $DIR/let_underscore_lock.rs:26:5
    |
 LL |     let _ = p_m1.lock();
    |     ^^^^^^^^^^^^^^^^^^^^
    |
    = help: consider using an underscore-prefixed named binding or dropping explicitly with `std::mem::drop`
 
 error: non-binding let on a synchronization lock
-  --> $DIR/let_underscore_lock.rs:25:5
+  --> $DIR/let_underscore_lock.rs:29:5
    |
 LL |     let _ = p_rw.read();
    |     ^^^^^^^^^^^^^^^^^^^^
    |
    = help: consider using an underscore-prefixed named binding or dropping explicitly with `std::mem::drop`
 
 error: non-binding let on a synchronization lock
-  --> $DIR/let_underscore_lock.rs:26:5
+  --> $DIR/let_underscore_lock.rs:30:5
    |
 LL |     let _ = p_rw.write();
    |     ^^^^^^^^^^^^^^^^^^^^^