Replace pointer castings (as) by their API equivalent (#11818)

# Objective

Since rust `1.76`,
[`ptr::from_ref`](https://doc.rust-lang.org/stable/std/ptr/fn.from_ref.html)
and
[`ptr::from_mut`](https://doc.rust-lang.org/stable/std/ptr/fn.from_mut.html)
are stable.

This PR replaces code that use `as` casting by one of `ptr::from_ref`,
`ptr::from_mut`, `cast_mut`, `cast_const`, or `cast` methods, which are
less error-prone.

## Solution

- Bump MSRV to `1.76.0`
- Enables the following clippy lints:
-
[`ptr_as_ptr`](https://rust-lang.github.io/rust-clippy/master/index.html#/ptr_as_ptr)
-
[`ptr_cast_constness`](https://rust-lang.github.io/rust-clippy/master/index.html#/ptr_cast_constness)
-
[`ref_as_ptr`](https://rust-lang.github.io/rust-clippy/master/index.html#/ref_as_ptr)
(I fix all warnings for this one, but it requires rust 1.77 to be
enabled)
- Fix the lints mentioned above

Cargo.toml

@@ -11,7 +11,7 @@ license = "MIT OR Apache-2.0"
 readme = "README.md"
 repository = "https://github.com/bevyengine/bevy"
 documentation = "https://docs.rs/bevy"
-rust-version = "1.74.0"
+rust-version = "1.76.0"
 
 [workspace]
 exclude = [
@@ -40,6 +40,11 @@ match_same_arms = "warn"
 semicolon_if_nothing_returned = "warn"
 map_flatten = "warn"
 
+ptr_as_ptr = "warn"
+ptr_cast_constness = "warn"
+#TODO(rust 1.77): enable `ref_as_ptr`
+# ref_as_ptr = "warn"
+
 [workspace.lints.rust]
 unsafe_op_in_unsafe_fn = "warn"
 missing_docs = "warn"

crates/bevy_ecs/src/query/state.rs

@@ -14,7 +14,7 @@ use crate::{
 #[cfg(feature = "trace")]
 use bevy_utils::tracing::Span;
 use fixedbitset::FixedBitSet;
-use std::{any::TypeId, borrow::Borrow, fmt, mem::MaybeUninit};
+use std::{any::TypeId, borrow::Borrow, fmt, mem::MaybeUninit, ptr};
 
 use super::{
     NopWorldQuery, QueryBuilder, QueryData, QueryEntityError, QueryFilter, QueryManyIter,
@@ -93,7 +93,7 @@ impl<D: QueryData, F: QueryFilter> QueryState<D, F> {
     >(
         &self,
     ) -> &QueryState<NewD, NewF> {
-        &*(self as *const QueryState<D, F> as *const QueryState<NewD, NewF>)
+        &*ptr::from_ref(self).cast::<QueryState<NewD, NewF>>()
     }
 
     /// Returns the archetype components accessed by this query.

crates/bevy_ecs/src/world/unsafe_world_cell.rs

@@ -17,7 +17,7 @@ use crate::{
     system::{Res, Resource},
 };
 use bevy_ptr::Ptr;
-use std::{any::TypeId, cell::UnsafeCell, fmt::Debug, marker::PhantomData};
+use std::{any::TypeId, cell::UnsafeCell, fmt::Debug, marker::PhantomData, ptr};
 
 /// Variant of the [`World`] where resource and component accesses take `&self`, and the responsibility to avoid
 /// aliasing violations are given to the caller instead of being checked at compile-time by rust's unique XOR shared rule.
@@ -85,13 +85,13 @@ impl<'w> UnsafeWorldCell<'w> {
     /// Creates a [`UnsafeWorldCell`] that can be used to access everything immutably
     #[inline]
     pub(crate) fn new_readonly(world: &'w World) -> Self {
-        UnsafeWorldCell(world as *const World as *mut World, PhantomData)
+        Self(ptr::from_ref(world).cast_mut(), PhantomData)
     }
 
     /// Creates [`UnsafeWorldCell`] that can be used to access everything mutably
     #[inline]
     pub(crate) fn new_mutable(world: &'w mut World) -> Self {
-        Self(world as *mut World, PhantomData)
+        Self(ptr::from_mut(world), PhantomData)
     }
 
     /// Gets a mutable reference to the [`World`] this [`UnsafeWorldCell`] belongs to.

crates/bevy_mikktspace/src/lib.rs

@@ -1,7 +1,8 @@
 #![allow(
     unsafe_op_in_unsafe_fn,
     clippy::all,
-    clippy::undocumented_unsafe_blocks
+    clippy::undocumented_unsafe_blocks,
+    clippy::ptr_cast_constness
 )]
 // FIXME(3492): remove once docs are ready
 #![allow(missing_docs)]

crates/bevy_ptr/src/lib.rs

@@ -393,7 +393,7 @@ impl<'a, T> Copy for ThinSlicePtr<'a, T> {}
 impl<'a, T> From<&'a [T]> for ThinSlicePtr<'a, T> {
     #[inline]
     fn from(slice: &'a [T]) -> Self {
-        let ptr = slice.as_ptr() as *mut T;
+        let ptr = slice.as_ptr().cast_mut();
         Self {
             // SAFETY: a reference can never be null
             ptr: unsafe { NonNull::new_unchecked(ptr.debug_ensure_aligned()) },

crates/bevy_utils/src/synccell.rs

@@ -2,6 +2,8 @@
 //!
 //! [`std::sync::Exclusive`]: https://doc.rust-lang.org/nightly/std/sync/struct.Exclusive.html
 
+use std::ptr;
+
 /// See [`Exclusive`](https://github.com/rust-lang/rust/issues/98407) for stdlib's upcoming implementation,
 /// which should replace this one entirely.
 ///
@@ -41,7 +43,7 @@ impl<T: ?Sized> SyncCell<T> {
     /// to its inner value, to skip constructing with [`new()`](SyncCell::new()).
     pub fn from_mut(r: &'_ mut T) -> &'_ mut SyncCell<T> {
         // SAFETY: repr is transparent, so refs have the same layout; and `SyncCell` properties are `&mut`-agnostic
-        unsafe { &mut *(r as *mut T as *mut SyncCell<T>) }
+        unsafe { &mut *(ptr::from_mut(r) as *mut SyncCell<T>) }
     }
 }
 

crates/bevy_utils/src/syncunsafecell.rs

@@ -3,6 +3,7 @@
 //! [`std::cell::SyncUnsafeCell`]: https://doc.rust-lang.org/nightly/std/cell/struct.SyncUnsafeCell.html
 
 pub use core::cell::UnsafeCell;
+use core::ptr;
 
 /// [`UnsafeCell`], but [`Sync`].
 ///
@@ -72,13 +73,13 @@ impl<T: ?Sized> SyncUnsafeCell<T> {
         // We can just cast the pointer from `SyncUnsafeCell<T>` to `T` because
         // of #[repr(transparent)] on both SyncUnsafeCell and UnsafeCell.
         // See UnsafeCell::raw_get.
-        this as *const T as *mut T
+        (this as *const T).cast_mut()
     }
 
     #[inline]
     /// Returns a `&mut SyncUnsafeCell<T>` from a `&mut T`.
     pub fn from_mut(t: &mut T) -> &mut SyncUnsafeCell<T> {
-        let ptr = t as *mut T as *mut SyncUnsafeCell<T>;
+        let ptr = ptr::from_mut(t) as *mut SyncUnsafeCell<T>;
         // SAFETY: `ptr` must be safe to mutably dereference, since it was originally
         // obtained from a mutable reference. `SyncUnsafeCell` has the same representation
         // as the original type `T`, since the former is annotated with #[repr(transparent)].
@@ -105,7 +106,7 @@ impl<T> SyncUnsafeCell<[T]> {
         // - `SyncUnsafeCell<T>` has the same layout as `T`
         // - `SyncUnsafeCell<[T]>` has the same layout as `[T]`
         // - `SyncUnsafeCell<[T]>` has the same layout as `[SyncUnsafeCell<T>]`
-        unsafe { &*(self as *const SyncUnsafeCell<[T]> as *const [SyncUnsafeCell<T>]) }
+        unsafe { &*(ptr::from_ref(self) as *const [SyncUnsafeCell<T>]) }
     }
 }