fix(core): #[default_method_body_is_const] has been superseded by #[const_trait]

96964

Author: yvt

doc/toolchain_limitations.md

@@ -536,7 +536,7 @@ const _: () = assert!(matches!((2..4).next(), Some(2)));
 ```
 
 
-### `[tag:iterator_const_default]` `Iterator`'s methods lack `#[default_method_body_is_const]`
+### `[tag:iterator_const_default]` `Iterator` lack `#[const_trait]`
 
 Implementing `const Iterator` requires you to implement all of its methods, which is impossible to do correctly.
 

src/r3_core/src/bag.rs

@@ -2,12 +2,12 @@
 use core::mem::transmute;
 
 /// A heterogeneous collection to store property values.
+#[const_trait]
 pub trait Bag: private::Sealed + Copy {
     /// Insert an item and return a new `impl Bag`.
     ///
     /// For `const fn`-ness, this method can't have a provided implementation.
     #[inline]
-    #[default_method_body_is_const]
     fn insert<T: 'static>(self, head: T) -> List<T, Self> {
         assert!(self.get::<T>().is_none(), "duplicate entry");
         (head, self)

src/r3_core/src/utils/alloc.rs

@@ -225,13 +225,13 @@ pub struct AllocError;
 /// This trait is subject to [the kernel-side API stability guarantee][1].
 ///
 /// [1]: crate#stability
+#[const_trait]
 pub unsafe trait Allocator {
     /// Attempts to allocate a block of memory.
     fn allocate(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocError>;
 
     /// Behaves like `allocate`, but also ensures that the returned memory is
     /// zero-initialized.
-    #[default_method_body_is_const]
     fn allocate_zeroed(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocError> {
         let ptr = const_try_result!(self.allocate(layout));
         // SAFETY: `alloc` returns a valid memory block
@@ -251,7 +251,6 @@ pub unsafe trait Allocator {
     /// # Safety
     ///
     /// See [`core::alloc::Allocator::grow`]'s documentation.
-    #[default_method_body_is_const]
     unsafe fn grow(
         &self,
         ptr: NonNull<u8>,
@@ -284,7 +283,6 @@ pub unsafe trait Allocator {
     /// # Safety
     ///
     /// See [`core::alloc::Allocator::grow_zeroed`]'s documentation.
-    #[default_method_body_is_const]
     unsafe fn grow_zeroed(
         &self,
         ptr: NonNull<u8>,
@@ -316,7 +314,6 @@ pub unsafe trait Allocator {
     /// # Safety
     ///
     /// See [`core::alloc::Allocator::shrink`]'s documentation.
-    #[default_method_body_is_const]
     unsafe fn shrink(
         &self,
         ptr: NonNull<u8>,
@@ -344,7 +341,6 @@ pub unsafe trait Allocator {
     }
 
     /// Creates a “by reference” adapter for this instance of `Allocator`.
-    #[default_method_body_is_const]
     fn by_ref(&self) -> &Self
     where
         Self: Sized,

src/r3_core/src/utils/binary_heap/mod.rs

@@ -11,12 +11,12 @@ mod veclike;
 pub use self::veclike::*;
 
 /// Context type for [`BinaryHeap`]'s operations.
+#[const_trait]
 pub trait BinaryHeapCtx<Element> {
     /// Return `true` iff `x < y`.
     fn lt(&mut self, x: &Element, y: &Element) -> bool;
 
     /// Called when the element `e` is moved to the new position `new_index`.
-    #[default_method_body_is_const]
     fn on_move(&mut self, e: &mut Element, new_index: usize) {
         let _ = (e, new_index);
     }