Address lints in bevy_platform_support (#18477)

# Objective

@mockersf noticed there were some failing lints in
`bevy_platform_support`.

## Solution

Addressed the lints!

## Testing

- CI

crates/bevy_platform_support/src/sync/barrier.rs

@@ -1,12 +1,12 @@
 //! Provides `Barrier` and `BarrierWaitResult`
 
-pub use barrier::{Barrier, BarrierWaitResult};
+pub use implementation::{Barrier, BarrierWaitResult};
 
 #[cfg(feature = "std")]
-use std::sync as barrier;
+use std::sync as implementation;
 
 #[cfg(not(feature = "std"))]
-mod barrier {
+mod implementation {
     use core::fmt;
 
     /// Fallback implementation of `Barrier` from the standard library.

crates/bevy_platform_support/src/sync/lazy_lock.rs

@@ -1,11 +1,11 @@
 //! Provides `LazyLock`
 
-pub use lazy_lock::LazyLock;
+pub use implementation::LazyLock;
 
 #[cfg(feature = "std")]
-use std::sync as lazy_lock;
+use std::sync as implementation;
 
 #[cfg(not(feature = "std"))]
-mod lazy_lock {
+mod implementation {
     pub use spin::Lazy as LazyLock;
 }

crates/bevy_platform_support/src/sync/mutex.rs

@@ -1,12 +1,12 @@
 //! Provides `Mutex` and `MutexGuard`
 
-pub use mutex::{Mutex, MutexGuard};
+pub use implementation::{Mutex, MutexGuard};
 
 #[cfg(feature = "std")]
-use std::sync as mutex;
+use std::sync as implementation;
 
 #[cfg(not(feature = "std"))]
-mod mutex {
+mod implementation {
     use crate::sync::{LockResult, TryLockError, TryLockResult};
     use core::fmt;
 
@@ -81,7 +81,7 @@ mod mutex {
         }
     }
 
-    impl<T: ?Sized + Default> Default for Mutex<T> {
+    impl<T: Default> Default for Mutex<T> {
         fn default() -> Mutex<T> {
             Mutex::new(Default::default())
         }

crates/bevy_platform_support/src/sync/once.rs

@@ -1,12 +1,12 @@
 //! Provides `Once`, `OnceState`, `OnceLock`
 
-pub use once::{Once, OnceLock, OnceState};
+pub use implementation::{Once, OnceLock, OnceState};
 
 #[cfg(feature = "std")]
-use std::sync as once;
+use std::sync as implementation;
 
 #[cfg(not(feature = "std"))]
-mod once {
+mod implementation {
     use core::{
         fmt,
         panic::{RefUnwindSafe, UnwindSafe},
@@ -145,6 +145,7 @@ mod once {
         /// Creates a new `Once` value.
         ///
         /// See the standard library for further details.
+        #[expect(clippy::new_without_default, reason = "matching std::sync::Once")]
         pub const fn new() -> Self {
             Self {
                 inner: OnceLock::new(),

crates/bevy_platform_support/src/sync/poison.rs

@@ -1,12 +1,12 @@
 //! Provides `LockResult`, `PoisonError`, `TryLockError`, `TryLockResult`
 
-pub use poison::{LockResult, PoisonError, TryLockError, TryLockResult};
+pub use implementation::{LockResult, PoisonError, TryLockError, TryLockResult};
 
 #[cfg(feature = "std")]
-use std::sync as poison;
+use std::sync as implementation;
 
 #[cfg(not(feature = "std"))]
-mod poison {
+mod implementation {
     use core::{error::Error, fmt};
 
     /// Fallback implementation of `PoisonError` from the standard library.

crates/bevy_platform_support/src/sync/rwlock.rs

@@ -1,12 +1,12 @@
-//! TODO: Implement `RwLock`, `RwLockReadGuard`, `RwLockWriteGuard`
+//! Provides `RwLock`, `RwLockReadGuard`, `RwLockWriteGuard`
 
-pub use rwlock::{RwLock, RwLockReadGuard, RwLockWriteGuard};
+pub use implementation::{RwLock, RwLockReadGuard, RwLockWriteGuard};
 
 #[cfg(feature = "std")]
-use std::sync as rwlock;
+use std::sync as implementation;
 
 #[cfg(not(feature = "std"))]
-mod rwlock {
+mod implementation {
     use crate::sync::{LockResult, TryLockError, TryLockResult};
     use core::fmt;
 

crates/bevy_platform_support/src/time/fallback.rs

@@ -36,7 +36,7 @@ impl Instant {
         let getter = ELAPSED_GETTER.load(Ordering::Acquire);
 
         // SAFETY: Function pointer is always valid
-        let getter = unsafe { core::mem::transmute::<_, fn() -> Duration>(getter) };
+        let getter = unsafe { core::mem::transmute::<*mut (), fn() -> Duration>(getter) };
 
         Self((getter)())
     }
@@ -149,28 +149,29 @@ impl fmt::Debug for Instant {
 }
 
 fn unset_getter() -> Duration {
-    let _nanos: u64;
-
-    #[cfg(target_arch = "x86")]
-    unsafe {
-        _nanos = core::arch::x86::_rdtsc();
+    cfg_if::cfg_if! {
+        if #[cfg(target_arch = "x86")] {
+            // SAFETY: standard technique for getting a nanosecond counter on x86
+            let nanos = unsafe {
+                core::arch::x86::_rdtsc()
+            };
+            Duration::from_nanos(nanos)
+        } else if #[cfg(target_arch = "x86_64")] {
+            // SAFETY: standard technique for getting a nanosecond counter on x86_64
+            let nanos = unsafe {
+                core::arch::x86_64::_rdtsc()
+            };
+            Duration::from_nanos(nanos)
+        } else if #[cfg(target_arch = "aarch64")] {
+            // SAFETY: standard technique for getting a nanosecond counter of aarch64
+            let nanos = unsafe {
+                let mut ticks: u64;
+                core::arch::asm!("mrs {}, cntvct_el0", out(reg) ticks);
+                ticks
+            };
+            Duration::from_nanos(nanos)
+        } else {
+            panic!("An elapsed time getter has not been provided to `Instant`. Please use `Instant::set_elapsed(...)` before calling `Instant::now()`")
+        }
     }
-
-    #[cfg(target_arch = "x86_64")]
-    unsafe {
-        _nanos = core::arch::x86_64::_rdtsc();
-    }
-
-    #[cfg(target_arch = "aarch64")]
-    unsafe {
-        let mut ticks: u64;
-        core::arch::asm!("mrs {}, cntvct_el0", out(reg) ticks);
-        _nanos = ticks;
-    }
-
-    #[cfg(not(any(target_arch = "x86", target_arch = "x86_64", target_arch = "aarch64")))]
-    panic!("An elapsed time getter has not been provided to `Instant`. Please use `Instant::set_elapsed(...)` before calling `Instant::now()`");
-
-    #[cfg(any(target_arch = "x86", target_arch = "x86_64", target_arch = "aarch64"))]
-    return Duration::from_nanos(_nanos);
 }