Auto merge of #8260 - taiki-e:mutex_atomic, r=llogiq

Downgrade mutex_atomic to nursery

See #1516 and #4295.

There are suggestions about removing this lint from the default warned lints in both issues.
Also, [`mutex_integer`](https://rust-lang.github.io/rust-clippy/master/index.html#mutex_integer) lint that has the same problems as this lint is in `nursery` group.

changelog: Moved [`mutex_atomic`] to `nursery`

Author: bors

clippy_lints/src/lib.register_all.rs

@@ -206,7 +206,6 @@ store.register_group(true, "clippy::all", Some("clippy_all"), vec![
     LintId::of(mut_key::MUTABLE_KEY_TYPE),
     LintId::of(mut_mutex_lock::MUT_MUTEX_LOCK),
     LintId::of(mut_reference::UNNECESSARY_MUT_PASSED),
-    LintId::of(mutex_atomic::MUTEX_ATOMIC),
     LintId::of(needless_arbitrary_self_type::NEEDLESS_ARBITRARY_SELF_TYPE),
     LintId::of(needless_bool::BOOL_COMPARISON),
     LintId::of(needless_bool::NEEDLESS_BOOL),

clippy_lints/src/lib.register_nursery.rs

@@ -15,6 +15,7 @@ store.register_group(true, "clippy::nursery", Some("clippy_nursery"), vec![
     LintId::of(let_if_seq::USELESS_LET_IF_SEQ),
     LintId::of(missing_const_for_fn::MISSING_CONST_FOR_FN),
     LintId::of(mutable_debug_assertion::DEBUG_ASSERT_WITH_MUT_CALL),
+    LintId::of(mutex_atomic::MUTEX_ATOMIC),
     LintId::of(mutex_atomic::MUTEX_INTEGER),
     LintId::of(non_send_fields_in_send_ty::NON_SEND_FIELDS_IN_SEND_TY),
     LintId::of(nonstandard_macro_braces::NONSTANDARD_MACRO_BRACES),

clippy_lints/src/lib.register_perf.rs

@@ -19,7 +19,6 @@ store.register_group(true, "clippy::perf", Some("clippy_perf"), vec![
     LintId::of(methods::SINGLE_CHAR_PATTERN),
     LintId::of(methods::UNNECESSARY_TO_OWNED),
     LintId::of(misc::CMP_OWNED),
-    LintId::of(mutex_atomic::MUTEX_ATOMIC),
     LintId::of(redundant_clone::REDUNDANT_CLONE),
     LintId::of(slow_vector_initialization::SLOW_VECTOR_INITIALIZATION),
     LintId::of(stable_sort_primitive::STABLE_SORT_PRIMITIVE),

clippy_lints/src/mutex_atomic.rs

@@ -38,7 +38,7 @@ declare_clippy_lint! {
     /// ```
     #[clippy::version = "pre 1.29.0"]
     pub MUTEX_ATOMIC,
-    perf,
+    nursery,
     "using a mutex where an atomic value could be used instead"
 }
 

tests/ui/mutex_atomic.rs

@@ -1,5 +1,6 @@
 #![warn(clippy::all)]
 #![warn(clippy::mutex_integer)]
+#![warn(clippy::mutex_atomic)]
 
 fn main() {
     use std::sync::Mutex;

tests/ui/mutex_atomic.stderr

@@ -1,45 +1,45 @@
 error: consider using an `AtomicBool` instead of a `Mutex` here; if you just want the locking behavior and not the internal type, consider using `Mutex<()>`
-  --> $DIR/mutex_atomic.rs:6:5
+  --> $DIR/mutex_atomic.rs:7:5
    |
 LL |     Mutex::new(true);
    |     ^^^^^^^^^^^^^^^^
    |
    = note: `-D clippy::mutex-atomic` implied by `-D warnings`
 
 error: consider using an `AtomicUsize` instead of a `Mutex` here; if you just want the locking behavior and not the internal type, consider using `Mutex<()>`
-  --> $DIR/mutex_atomic.rs:7:5
+  --> $DIR/mutex_atomic.rs:8:5
    |
 LL |     Mutex::new(5usize);
    |     ^^^^^^^^^^^^^^^^^^
 
 error: consider using an `AtomicIsize` instead of a `Mutex` here; if you just want the locking behavior and not the internal type, consider using `Mutex<()>`
-  --> $DIR/mutex_atomic.rs:8:5
+  --> $DIR/mutex_atomic.rs:9:5
    |
 LL |     Mutex::new(9isize);
    |     ^^^^^^^^^^^^^^^^^^
 
 error: consider using an `AtomicPtr` instead of a `Mutex` here; if you just want the locking behavior and not the internal type, consider using `Mutex<()>`
-  --> $DIR/mutex_atomic.rs:10:5
+  --> $DIR/mutex_atomic.rs:11:5
    |
 LL |     Mutex::new(&x as *const u32);
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: consider using an `AtomicPtr` instead of a `Mutex` here; if you just want the locking behavior and not the internal type, consider using `Mutex<()>`
-  --> $DIR/mutex_atomic.rs:11:5
+  --> $DIR/mutex_atomic.rs:12:5
    |
 LL |     Mutex::new(&mut x as *mut u32);
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: consider using an `AtomicUsize` instead of a `Mutex` here; if you just want the locking behavior and not the internal type, consider using `Mutex<()>`
-  --> $DIR/mutex_atomic.rs:12:5
+  --> $DIR/mutex_atomic.rs:13:5
    |
 LL |     Mutex::new(0u32);
    |     ^^^^^^^^^^^^^^^^
    |
    = note: `-D clippy::mutex-integer` implied by `-D warnings`
 
 error: consider using an `AtomicIsize` instead of a `Mutex` here; if you just want the locking behavior and not the internal type, consider using `Mutex<()>`
-  --> $DIR/mutex_atomic.rs:13:5
+  --> $DIR/mutex_atomic.rs:14:5
    |
 LL |     Mutex::new(0i32);
    |     ^^^^^^^^^^^^^^^^