| //! The arena, a fast but limited type of allocator. |
| //! |
| //! Arenas are a type of allocator that destroy the objects within, all at |
| //! once, once the arena itself is destroyed. They do not support deallocation |
| //! of individual objects while the arena itself is still alive. The benefit |
| //! of an arena is very fast allocation; just a pointer bump. |
| //! |
| //! This crate implements several kinds of arena. |
| |
| #![doc( |
| html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/", |
| test(no_crate_inject, attr(deny(warnings))) |
| )] |
| #![feature(dropck_eyepatch)] |
| #![feature(new_uninit)] |
| #![feature(maybe_uninit_slice)] |
| #![cfg_attr(test, feature(test))] |
| |
| use smallvec::SmallVec; |
| |
| use std::alloc::Layout; |
| use std::cell::{Cell, RefCell}; |
| use std::cmp; |
| use std::marker::{PhantomData, Send}; |
| use std::mem::{self, MaybeUninit}; |
| use std::ptr; |
| use std::slice; |
| |
| #[inline(never)] |
| #[cold] |
| pub fn cold_path<F: FnOnce() -> R, R>(f: F) -> R { |
| f() |
| } |
| |
| /// An arena that can hold objects of only one type. |
| pub struct TypedArena<T> { |
| /// A pointer to the next object to be allocated. |
| ptr: Cell<*mut T>, |
| |
| /// A pointer to the end of the allocated area. When this pointer is |
| /// reached, a new chunk is allocated. |
| end: Cell<*mut T>, |
| |
| /// A vector of arena chunks. |
| chunks: RefCell<Vec<TypedArenaChunk<T>>>, |
| |
| /// Marker indicating that dropping the arena causes its owned |
| /// instances of `T` to be dropped. |
| _own: PhantomData<T>, |
| } |
| |
| struct TypedArenaChunk<T> { |
| /// The raw storage for the arena chunk. |
| storage: Box<[MaybeUninit<T>]>, |
| /// The number of valid entries in the chunk. |
| entries: usize, |
| } |
| |
| impl<T> TypedArenaChunk<T> { |
| #[inline] |
| unsafe fn new(capacity: usize) -> TypedArenaChunk<T> { |
| TypedArenaChunk { storage: Box::new_uninit_slice(capacity), entries: 0 } |
| } |
| |
| /// Destroys this arena chunk. |
| #[inline] |
| unsafe fn destroy(&mut self, len: usize) { |
| // The branch on needs_drop() is an -O1 performance optimization. |
| // Without the branch, dropping TypedArena<u8> takes linear time. |
| if mem::needs_drop::<T>() { |
| ptr::drop_in_place(MaybeUninit::slice_assume_init_mut(&mut self.storage[..len])); |
| } |
| } |
| |
| // Returns a pointer to the first allocated object. |
| #[inline] |
| fn start(&mut self) -> *mut T { |
| MaybeUninit::slice_as_mut_ptr(&mut self.storage) |
| } |
| |
| // Returns a pointer to the end of the allocated space. |
| #[inline] |
| fn end(&mut self) -> *mut T { |
| unsafe { |
| if mem::size_of::<T>() == 0 { |
| // A pointer as large as possible for zero-sized elements. |
| !0 as *mut T |
| } else { |
| self.start().add(self.storage.len()) |
| } |
| } |
| } |
| } |
| |
| // The arenas start with PAGE-sized chunks, and then each new chunk is twice as |
| // big as its predecessor, up until we reach HUGE_PAGE-sized chunks, whereupon |
| // we stop growing. This scales well, from arenas that are barely used up to |
| // arenas that are used for 100s of MiBs. Note also that the chosen sizes match |
| // the usual sizes of pages and huge pages on Linux. |
| const PAGE: usize = 4096; |
| const HUGE_PAGE: usize = 2 * 1024 * 1024; |
| |
| impl<T> Default for TypedArena<T> { |
| /// Creates a new `TypedArena`. |
| fn default() -> TypedArena<T> { |
| TypedArena { |
| // We set both `ptr` and `end` to 0 so that the first call to |
| // alloc() will trigger a grow(). |
| ptr: Cell::new(ptr::null_mut()), |
| end: Cell::new(ptr::null_mut()), |
| chunks: RefCell::new(vec![]), |
| _own: PhantomData, |
| } |
| } |
| } |
| |
| impl<T> TypedArena<T> { |
| /// Allocates an object in the `TypedArena`, returning a reference to it. |
| #[inline] |
| pub fn alloc(&self, object: T) -> &mut T { |
| if self.ptr == self.end { |
| self.grow(1) |
| } |
| |
| unsafe { |
| if mem::size_of::<T>() == 0 { |
| self.ptr.set((self.ptr.get() as *mut u8).wrapping_offset(1) as *mut T); |
| let ptr = mem::align_of::<T>() as *mut T; |
| // Don't drop the object. This `write` is equivalent to `forget`. |
| ptr::write(ptr, object); |
| &mut *ptr |
| } else { |
| let ptr = self.ptr.get(); |
| // Advance the pointer. |
| self.ptr.set(self.ptr.get().offset(1)); |
| // Write into uninitialized memory. |
| ptr::write(ptr, object); |
| &mut *ptr |
| } |
| } |
| } |
| |
| #[inline] |
| fn can_allocate(&self, additional: usize) -> bool { |
| let available_bytes = self.end.get() as usize - self.ptr.get() as usize; |
| let additional_bytes = additional.checked_mul(mem::size_of::<T>()).unwrap(); |
| available_bytes >= additional_bytes |
| } |
| |
| /// Ensures there's enough space in the current chunk to fit `len` objects. |
| #[inline] |
| fn ensure_capacity(&self, additional: usize) { |
| if !self.can_allocate(additional) { |
| self.grow(additional); |
| debug_assert!(self.can_allocate(additional)); |
| } |
| } |
| |
| #[inline] |
| unsafe fn alloc_raw_slice(&self, len: usize) -> *mut T { |
| assert!(mem::size_of::<T>() != 0); |
| assert!(len != 0); |
| |
| self.ensure_capacity(len); |
| |
| let start_ptr = self.ptr.get(); |
| self.ptr.set(start_ptr.add(len)); |
| start_ptr |
| } |
| |
| /// Allocates a slice of objects that are copied into the `TypedArena`, returning a mutable |
| /// reference to it. Will panic if passed a zero-sized types. |
| /// |
| /// Panics: |
| /// |
| /// - Zero-sized types |
| /// - Zero-length slices |
| #[inline] |
| pub fn alloc_slice(&self, slice: &[T]) -> &mut [T] |
| where |
| T: Copy, |
| { |
| unsafe { |
| let len = slice.len(); |
| let start_ptr = self.alloc_raw_slice(len); |
| slice.as_ptr().copy_to_nonoverlapping(start_ptr, len); |
| slice::from_raw_parts_mut(start_ptr, len) |
| } |
| } |
| |
| #[inline] |
| pub fn alloc_from_iter<I: IntoIterator<Item = T>>(&self, iter: I) -> &mut [T] { |
| assert!(mem::size_of::<T>() != 0); |
| let mut vec: SmallVec<[_; 8]> = iter.into_iter().collect(); |
| if vec.is_empty() { |
| return &mut []; |
| } |
| // Move the content to the arena by copying it and then forgetting |
| // the content of the SmallVec |
| unsafe { |
| let len = vec.len(); |
| let start_ptr = self.alloc_raw_slice(len); |
| vec.as_ptr().copy_to_nonoverlapping(start_ptr, len); |
| vec.set_len(0); |
| slice::from_raw_parts_mut(start_ptr, len) |
| } |
| } |
| |
| /// Grows the arena. |
| #[inline(never)] |
| #[cold] |
| fn grow(&self, additional: usize) { |
| unsafe { |
| // We need the element size to convert chunk sizes (ranging from |
| // PAGE to HUGE_PAGE bytes) to element counts. |
| let elem_size = cmp::max(1, mem::size_of::<T>()); |
| let mut chunks = self.chunks.borrow_mut(); |
| let mut new_cap; |
| if let Some(last_chunk) = chunks.last_mut() { |
| // If a type is `!needs_drop`, we don't need to keep track of how many elements |
| // the chunk stores - the field will be ignored anyway. |
| if mem::needs_drop::<T>() { |
| let used_bytes = self.ptr.get() as usize - last_chunk.start() as usize; |
| last_chunk.entries = used_bytes / mem::size_of::<T>(); |
| } |
| |
| // If the previous chunk's len is less than HUGE_PAGE |
| // bytes, then this chunk will be least double the previous |
| // chunk's size. |
| new_cap = last_chunk.storage.len().min(HUGE_PAGE / elem_size / 2); |
| new_cap = new_cap * 2; |
| } else { |
| new_cap = PAGE / elem_size; |
| } |
| // Also ensure that this chunk can fit `additional`. |
| new_cap = cmp::max(additional, new_cap); |
| |
| let mut chunk = TypedArenaChunk::<T>::new(new_cap); |
| self.ptr.set(chunk.start()); |
| self.end.set(chunk.end()); |
| chunks.push(chunk); |
| } |
| } |
| |
| /// Clears the arena. Deallocates all but the longest chunk which may be reused. |
| pub fn clear(&mut self) { |
| unsafe { |
| // Clear the last chunk, which is partially filled. |
| let mut chunks_borrow = self.chunks.borrow_mut(); |
| if let Some(mut last_chunk) = chunks_borrow.last_mut() { |
| self.clear_last_chunk(&mut last_chunk); |
| let len = chunks_borrow.len(); |
| // If `T` is ZST, code below has no effect. |
| for mut chunk in chunks_borrow.drain(..len - 1) { |
| chunk.destroy(chunk.entries); |
| } |
| } |
| } |
| } |
| |
| // Drops the contents of the last chunk. The last chunk is partially empty, unlike all other |
| // chunks. |
| fn clear_last_chunk(&self, last_chunk: &mut TypedArenaChunk<T>) { |
| // Determine how much was filled. |
| let start = last_chunk.start() as usize; |
| // We obtain the value of the pointer to the first uninitialized element. |
| let end = self.ptr.get() as usize; |
| // We then calculate the number of elements to be dropped in the last chunk, |
| // which is the filled area's length. |
| let diff = if mem::size_of::<T>() == 0 { |
| // `T` is ZST. It can't have a drop flag, so the value here doesn't matter. We get |
| // the number of zero-sized values in the last and only chunk, just out of caution. |
| // Recall that `end` was incremented for each allocated value. |
| end - start |
| } else { |
| (end - start) / mem::size_of::<T>() |
| }; |
| // Pass that to the `destroy` method. |
| unsafe { |
| last_chunk.destroy(diff); |
| } |
| // Reset the chunk. |
| self.ptr.set(last_chunk.start()); |
| } |
| } |
| |
| unsafe impl<#[may_dangle] T> Drop for TypedArena<T> { |
| fn drop(&mut self) { |
| unsafe { |
| // Determine how much was filled. |
| let mut chunks_borrow = self.chunks.borrow_mut(); |
| if let Some(mut last_chunk) = chunks_borrow.pop() { |
| // Drop the contents of the last chunk. |
| self.clear_last_chunk(&mut last_chunk); |
| // The last chunk will be dropped. Destroy all other chunks. |
| for chunk in chunks_borrow.iter_mut() { |
| chunk.destroy(chunk.entries); |
| } |
| } |
| // Box handles deallocation of `last_chunk` and `self.chunks`. |
| } |
| } |
| } |
| |
| unsafe impl<T: Send> Send for TypedArena<T> {} |
| |
| pub struct DroplessArena { |
| /// A pointer to the start of the free space. |
| start: Cell<*mut u8>, |
| |
| /// A pointer to the end of free space. |
| /// |
| /// The allocation proceeds from the end of the chunk towards the start. |
| /// When this pointer crosses the start pointer, a new chunk is allocated. |
| end: Cell<*mut u8>, |
| |
| /// A vector of arena chunks. |
| chunks: RefCell<Vec<TypedArenaChunk<u8>>>, |
| } |
| |
| unsafe impl Send for DroplessArena {} |
| |
| impl Default for DroplessArena { |
| #[inline] |
| fn default() -> DroplessArena { |
| DroplessArena { |
| start: Cell::new(ptr::null_mut()), |
| end: Cell::new(ptr::null_mut()), |
| chunks: Default::default(), |
| } |
| } |
| } |
| |
| impl DroplessArena { |
| #[inline(never)] |
| #[cold] |
| fn grow(&self, additional: usize) { |
| unsafe { |
| let mut chunks = self.chunks.borrow_mut(); |
| let mut new_cap; |
| if let Some(last_chunk) = chunks.last_mut() { |
| // There is no need to update `last_chunk.entries` because that |
| // field isn't used by `DroplessArena`. |
| |
| // If the previous chunk's len is less than HUGE_PAGE |
| // bytes, then this chunk will be least double the previous |
| // chunk's size. |
| new_cap = last_chunk.storage.len().min(HUGE_PAGE / 2); |
| new_cap = new_cap * 2; |
| } else { |
| new_cap = PAGE; |
| } |
| // Also ensure that this chunk can fit `additional`. |
| new_cap = cmp::max(additional, new_cap); |
| |
| let mut chunk = TypedArenaChunk::<u8>::new(new_cap); |
| self.start.set(chunk.start()); |
| self.end.set(chunk.end()); |
| chunks.push(chunk); |
| } |
| } |
| |
| /// Allocates a byte slice with specified layout from the current memory |
| /// chunk. Returns `None` if there is no free space left to satisfy the |
| /// request. |
| #[inline] |
| fn alloc_raw_without_grow(&self, layout: Layout) -> Option<*mut u8> { |
| let start = self.start.get() as usize; |
| let end = self.end.get() as usize; |
| |
| let align = layout.align(); |
| let bytes = layout.size(); |
| |
| let new_end = end.checked_sub(bytes)? & !(align - 1); |
| if start <= new_end { |
| let new_end = new_end as *mut u8; |
| self.end.set(new_end); |
| Some(new_end) |
| } else { |
| None |
| } |
| } |
| |
| #[inline] |
| pub fn alloc_raw(&self, layout: Layout) -> *mut u8 { |
| assert!(layout.size() != 0); |
| loop { |
| if let Some(a) = self.alloc_raw_without_grow(layout) { |
| break a; |
| } |
| // No free space left. Allocate a new chunk to satisfy the request. |
| // On failure the grow will panic or abort. |
| self.grow(layout.size()); |
| } |
| } |
| |
| #[inline] |
| pub fn alloc<T>(&self, object: T) -> &mut T { |
| assert!(!mem::needs_drop::<T>()); |
| |
| let mem = self.alloc_raw(Layout::for_value::<T>(&object)) as *mut T; |
| |
| unsafe { |
| // Write into uninitialized memory. |
| ptr::write(mem, object); |
| &mut *mem |
| } |
| } |
| |
| /// Allocates a slice of objects that are copied into the `DroplessArena`, returning a mutable |
| /// reference to it. Will panic if passed a zero-sized type. |
| /// |
| /// Panics: |
| /// |
| /// - Zero-sized types |
| /// - Zero-length slices |
| #[inline] |
| pub fn alloc_slice<T>(&self, slice: &[T]) -> &mut [T] |
| where |
| T: Copy, |
| { |
| assert!(!mem::needs_drop::<T>()); |
| assert!(mem::size_of::<T>() != 0); |
| assert!(!slice.is_empty()); |
| |
| let mem = self.alloc_raw(Layout::for_value::<[T]>(slice)) as *mut T; |
| |
| unsafe { |
| mem.copy_from_nonoverlapping(slice.as_ptr(), slice.len()); |
| slice::from_raw_parts_mut(mem, slice.len()) |
| } |
| } |
| |
| #[inline] |
| unsafe fn write_from_iter<T, I: Iterator<Item = T>>( |
| &self, |
| mut iter: I, |
| len: usize, |
| mem: *mut T, |
| ) -> &mut [T] { |
| let mut i = 0; |
| // Use a manual loop since LLVM manages to optimize it better for |
| // slice iterators |
| loop { |
| let value = iter.next(); |
| if i >= len || value.is_none() { |
| // We only return as many items as the iterator gave us, even |
| // though it was supposed to give us `len` |
| return slice::from_raw_parts_mut(mem, i); |
| } |
| ptr::write(mem.add(i), value.unwrap()); |
| i += 1; |
| } |
| } |
| |
| #[inline] |
| pub fn alloc_from_iter<T, I: IntoIterator<Item = T>>(&self, iter: I) -> &mut [T] { |
| let iter = iter.into_iter(); |
| assert!(mem::size_of::<T>() != 0); |
| assert!(!mem::needs_drop::<T>()); |
| |
| let size_hint = iter.size_hint(); |
| |
| match size_hint { |
| (min, Some(max)) if min == max => { |
| // We know the exact number of elements the iterator will produce here |
| let len = min; |
| |
| if len == 0 { |
| return &mut []; |
| } |
| |
| let mem = self.alloc_raw(Layout::array::<T>(len).unwrap()) as *mut T; |
| unsafe { self.write_from_iter(iter, len, mem) } |
| } |
| (_, _) => { |
| cold_path(move || -> &mut [T] { |
| let mut vec: SmallVec<[_; 8]> = iter.collect(); |
| if vec.is_empty() { |
| return &mut []; |
| } |
| // Move the content to the arena by copying it and then forgetting |
| // the content of the SmallVec |
| unsafe { |
| let len = vec.len(); |
| let start_ptr = |
| self.alloc_raw(Layout::for_value::<[T]>(vec.as_slice())) as *mut T; |
| vec.as_ptr().copy_to_nonoverlapping(start_ptr, len); |
| vec.set_len(0); |
| slice::from_raw_parts_mut(start_ptr, len) |
| } |
| }) |
| } |
| } |
| } |
| } |
| |
| /// Calls the destructor for an object when dropped. |
| struct DropType { |
| drop_fn: unsafe fn(*mut u8), |
| obj: *mut u8, |
| } |
| |
| unsafe fn drop_for_type<T>(to_drop: *mut u8) { |
| std::ptr::drop_in_place(to_drop as *mut T) |
| } |
| |
| impl Drop for DropType { |
| fn drop(&mut self) { |
| unsafe { (self.drop_fn)(self.obj) } |
| } |
| } |
| |
| /// An arena which can be used to allocate any type. |
| /// Allocating in this arena is unsafe since the type system |
| /// doesn't know which types it contains. In order to |
| /// allocate safely, you must store a PhantomData<T> |
| /// alongside this arena for each type T you allocate. |
| #[derive(Default)] |
| pub struct DropArena { |
| /// A list of destructors to run when the arena drops. |
| /// Ordered so `destructors` gets dropped before the arena |
| /// since its destructor can reference memory in the arena. |
| destructors: RefCell<Vec<DropType>>, |
| arena: DroplessArena, |
| } |
| |
| impl DropArena { |
| #[inline] |
| pub unsafe fn alloc<T>(&self, object: T) -> &mut T { |
| let mem = self.arena.alloc_raw(Layout::new::<T>()) as *mut T; |
| // Write into uninitialized memory. |
| ptr::write(mem, object); |
| let result = &mut *mem; |
| // Record the destructor after doing the allocation as that may panic |
| // and would cause `object`'s destuctor to run twice if it was recorded before |
| self.destructors |
| .borrow_mut() |
| .push(DropType { drop_fn: drop_for_type::<T>, obj: result as *mut T as *mut u8 }); |
| result |
| } |
| |
| #[inline] |
| pub unsafe fn alloc_from_iter<T, I: IntoIterator<Item = T>>(&self, iter: I) -> &mut [T] { |
| let mut vec: SmallVec<[_; 8]> = iter.into_iter().collect(); |
| if vec.is_empty() { |
| return &mut []; |
| } |
| let len = vec.len(); |
| |
| let start_ptr = self.arena.alloc_raw(Layout::array::<T>(len).unwrap()) as *mut T; |
| |
| let mut destructors = self.destructors.borrow_mut(); |
| // Reserve space for the destructors so we can't panic while adding them |
| destructors.reserve(len); |
| |
| // Move the content to the arena by copying it and then forgetting |
| // the content of the SmallVec |
| vec.as_ptr().copy_to_nonoverlapping(start_ptr, len); |
| mem::forget(vec.drain(..)); |
| |
| // Record the destructors after doing the allocation as that may panic |
| // and would cause `object`'s destuctor to run twice if it was recorded before |
| for i in 0..len { |
| destructors.push(DropType { |
| drop_fn: drop_for_type::<T>, |
| obj: start_ptr.offset(i as isize) as *mut u8, |
| }); |
| } |
| |
| slice::from_raw_parts_mut(start_ptr, len) |
| } |
| } |
| |
| #[macro_export] |
| macro_rules! arena_for_type { |
| ([][$ty:ty]) => { |
| $crate::TypedArena<$ty> |
| }; |
| ([few $(, $attrs:ident)*][$ty:ty]) => { |
| ::std::marker::PhantomData<$ty> |
| }; |
| ([$ignore:ident $(, $attrs:ident)*]$args:tt) => { |
| $crate::arena_for_type!([$($attrs),*]$args) |
| }; |
| } |
| |
| #[macro_export] |
| macro_rules! which_arena_for_type { |
| ([][$arena:expr]) => { |
| ::std::option::Option::Some($arena) |
| }; |
| ([few$(, $attrs:ident)*][$arena:expr]) => { |
| ::std::option::Option::None |
| }; |
| ([$ignore:ident$(, $attrs:ident)*]$args:tt) => { |
| $crate::which_arena_for_type!([$($attrs),*]$args) |
| }; |
| } |
| |
| #[macro_export] |
| macro_rules! declare_arena { |
| ([], [$($a:tt $name:ident: $ty:ty,)*], $tcx:lifetime) => { |
| #[derive(Default)] |
| pub struct Arena<$tcx> { |
| pub dropless: $crate::DroplessArena, |
| drop: $crate::DropArena, |
| $($name: $crate::arena_for_type!($a[$ty]),)* |
| } |
| |
| pub trait ArenaAllocatable<'tcx, T = Self>: Sized { |
| fn allocate_on<'a>(self, arena: &'a Arena<'tcx>) -> &'a mut Self; |
| fn allocate_from_iter<'a>( |
| arena: &'a Arena<'tcx>, |
| iter: impl ::std::iter::IntoIterator<Item = Self>, |
| ) -> &'a mut [Self]; |
| } |
| |
| impl<'tcx, T: Copy> ArenaAllocatable<'tcx, ()> for T { |
| #[inline] |
| fn allocate_on<'a>(self, arena: &'a Arena<'tcx>) -> &'a mut Self { |
| arena.dropless.alloc(self) |
| } |
| #[inline] |
| fn allocate_from_iter<'a>( |
| arena: &'a Arena<'tcx>, |
| iter: impl ::std::iter::IntoIterator<Item = Self>, |
| ) -> &'a mut [Self] { |
| arena.dropless.alloc_from_iter(iter) |
| } |
| |
| } |
| $( |
| impl<$tcx> ArenaAllocatable<$tcx, $ty> for $ty { |
| #[inline] |
| fn allocate_on<'a>(self, arena: &'a Arena<$tcx>) -> &'a mut Self { |
| if !::std::mem::needs_drop::<Self>() { |
| return arena.dropless.alloc(self); |
| } |
| match $crate::which_arena_for_type!($a[&arena.$name]) { |
| ::std::option::Option::<&$crate::TypedArena<Self>>::Some(ty_arena) => { |
| ty_arena.alloc(self) |
| } |
| ::std::option::Option::None => unsafe { arena.drop.alloc(self) }, |
| } |
| } |
| |
| #[inline] |
| fn allocate_from_iter<'a>( |
| arena: &'a Arena<$tcx>, |
| iter: impl ::std::iter::IntoIterator<Item = Self>, |
| ) -> &'a mut [Self] { |
| if !::std::mem::needs_drop::<Self>() { |
| return arena.dropless.alloc_from_iter(iter); |
| } |
| match $crate::which_arena_for_type!($a[&arena.$name]) { |
| ::std::option::Option::<&$crate::TypedArena<Self>>::Some(ty_arena) => { |
| ty_arena.alloc_from_iter(iter) |
| } |
| ::std::option::Option::None => unsafe { arena.drop.alloc_from_iter(iter) }, |
| } |
| } |
| } |
| )* |
| |
| impl<'tcx> Arena<'tcx> { |
| #[inline] |
| pub fn alloc<T: ArenaAllocatable<'tcx, U>, U>(&self, value: T) -> &mut T { |
| value.allocate_on(self) |
| } |
| |
| #[inline] |
| pub fn alloc_slice<T: ::std::marker::Copy>(&self, value: &[T]) -> &mut [T] { |
| if value.is_empty() { |
| return &mut []; |
| } |
| self.dropless.alloc_slice(value) |
| } |
| |
| pub fn alloc_from_iter<'a, T: ArenaAllocatable<'tcx, U>, U>( |
| &'a self, |
| iter: impl ::std::iter::IntoIterator<Item = T>, |
| ) -> &'a mut [T] { |
| T::allocate_from_iter(self, iter) |
| } |
| } |
| } |
| } |
| |
| #[cfg(test)] |
| mod tests; |