diff options
Diffstat (limited to 'rust/alloc/boxed.rs')
| -rw-r--r-- | rust/alloc/boxed.rs | 567 |
1 files changed, 484 insertions, 83 deletions
diff --git a/rust/alloc/boxed.rs b/rust/alloc/boxed.rs index dcfe87b14f3a..c8173cea8317 100644 --- a/rust/alloc/boxed.rs +++ b/rust/alloc/boxed.rs @@ -1,6 +1,6 @@ // SPDX-License-Identifier: Apache-2.0 OR MIT -//! A pointer type for heap allocation. +//! The `Box<T>` type for heap allocation. //! //! [`Box<T>`], casually referred to as a 'box', provides the simplest form of //! heap allocation in Rust. Boxes provide ownership for this allocation, and @@ -124,7 +124,21 @@ //! definition is just using `T*` can lead to undefined behavior, as //! described in [rust-lang/unsafe-code-guidelines#198][ucg#198]. //! +//! # Considerations for unsafe code +//! +//! **Warning: This section is not normative and is subject to change, possibly +//! being relaxed in the future! It is a simplified summary of the rules +//! currently implemented in the compiler.** +//! +//! The aliasing rules for `Box<T>` are the same as for `&mut T`. `Box<T>` +//! asserts uniqueness over its content. Using raw pointers derived from a box +//! after that box has been mutated through, moved or borrowed as `&mut T` +//! is not allowed. For more guidance on working with box from unsafe code, see +//! [rust-lang/unsafe-code-guidelines#326][ucg#326]. +//! +//! //! [ucg#198]: https://github.com/rust-lang/unsafe-code-guidelines/issues/198 +//! [ucg#326]: https://github.com/rust-lang/unsafe-code-guidelines/issues/326 //! [dereferencing]: core::ops::Deref //! [`Box::<T>::from_raw(value)`]: Box::from_raw //! [`Global`]: crate::alloc::Global @@ -138,14 +152,13 @@ use core::any::Any; use core::async_iter::AsyncIterator; use core::borrow; use core::cmp::Ordering; -use core::convert::{From, TryFrom}; +use core::error::Error; use core::fmt; use core::future::Future; use core::hash::{Hash, Hasher}; -#[cfg(not(no_global_oom_handling))] -use core::iter::FromIterator; -use core::iter::{FusedIterator, Iterator}; -use core::marker::{Destruct, Unpin, Unsize}; +use core::iter::FusedIterator; +use core::marker::Tuple; +use core::marker::Unsize; use core::mem; use core::ops::{ CoerceUnsized, Deref, DerefMut, DispatchFromDyn, Generator, GeneratorState, Receiver, @@ -163,6 +176,8 @@ use crate::raw_vec::RawVec; #[cfg(not(no_global_oom_handling))] use crate::str::from_boxed_utf8_unchecked; #[cfg(not(no_global_oom_handling))] +use crate::string::String; +#[cfg(not(no_global_oom_handling))] use crate::vec::Vec; #[cfg(not(no_thin))] @@ -172,7 +187,7 @@ pub use thin::ThinBox; #[cfg(not(no_thin))] mod thin; -/// A pointer type for heap allocation. +/// A pointer type that uniquely owns a heap allocation of type `T`. /// /// See the [module-level documentation](../../std/boxed/index.html) for more. #[lang = "owned_box"] @@ -196,12 +211,14 @@ impl<T> Box<T> { /// ``` /// let five = Box::new(5); /// ``` - #[cfg(not(no_global_oom_handling))] + #[cfg(all(not(no_global_oom_handling)))] #[inline(always)] #[stable(feature = "rust1", since = "1.0.0")] #[must_use] + #[rustc_diagnostic_item = "box_new"] pub fn new(x: T) -> Self { - box x + #[rustc_box] + Box::new(x) } /// Constructs a new box with uninitialized contents. @@ -256,14 +273,19 @@ impl<T> Box<T> { Self::new_zeroed_in(Global) } - /// Constructs a new `Pin<Box<T>>`. If `T` does not implement `Unpin`, then + /// Constructs a new `Pin<Box<T>>`. If `T` does not implement [`Unpin`], then /// `x` will be pinned in memory and unable to be moved. + /// + /// Constructing and pinning of the `Box` can also be done in two steps: `Box::pin(x)` + /// does the same as <code>[Box::into_pin]\([Box::new]\(x))</code>. Consider using + /// [`into_pin`](Box::into_pin) if you already have a `Box<T>`, or if you want to + /// construct a (pinned) `Box` in a different way than with [`Box::new`]. #[cfg(not(no_global_oom_handling))] #[stable(feature = "pin", since = "1.33.0")] #[must_use] #[inline(always)] pub fn pin(x: T) -> Pin<Box<T>> { - (box x).into() + Box::new(x).into() } /// Allocates memory on the heap then places `x` into it, @@ -355,12 +377,11 @@ impl<T, A: Allocator> Box<T, A> { /// ``` #[cfg(not(no_global_oom_handling))] #[unstable(feature = "allocator_api", issue = "32838")] - #[rustc_const_unstable(feature = "const_box", issue = "92521")] #[must_use] #[inline] - pub const fn new_in(x: T, alloc: A) -> Self + pub fn new_in(x: T, alloc: A) -> Self where - A: ~const Allocator + ~const Destruct, + A: Allocator, { let mut boxed = Self::new_uninit_in(alloc); unsafe { @@ -385,12 +406,10 @@ impl<T, A: Allocator> Box<T, A> { /// # Ok::<(), std::alloc::AllocError>(()) /// ``` #[unstable(feature = "allocator_api", issue = "32838")] - #[rustc_const_unstable(feature = "const_box", issue = "92521")] #[inline] - pub const fn try_new_in(x: T, alloc: A) -> Result<Self, AllocError> + pub fn try_new_in(x: T, alloc: A) -> Result<Self, AllocError> where - T: ~const Destruct, - A: ~const Allocator + ~const Destruct, + A: Allocator, { let mut boxed = Self::try_new_uninit_in(alloc)?; unsafe { @@ -420,13 +439,12 @@ impl<T, A: Allocator> Box<T, A> { /// assert_eq!(*five, 5) /// ``` #[unstable(feature = "allocator_api", issue = "32838")] - #[rustc_const_unstable(feature = "const_box", issue = "92521")] #[cfg(not(no_global_oom_handling))] #[must_use] // #[unstable(feature = "new_uninit", issue = "63291")] - pub const fn new_uninit_in(alloc: A) -> Box<mem::MaybeUninit<T>, A> + pub fn new_uninit_in(alloc: A) -> Box<mem::MaybeUninit<T>, A> where - A: ~const Allocator + ~const Destruct, + A: Allocator, { let layout = Layout::new::<mem::MaybeUninit<T>>(); // NOTE: Prefer match over unwrap_or_else since closure sometimes not inlineable. @@ -461,10 +479,9 @@ impl<T, A: Allocator> Box<T, A> { /// ``` #[unstable(feature = "allocator_api", issue = "32838")] // #[unstable(feature = "new_uninit", issue = "63291")] - #[rustc_const_unstable(feature = "const_box", issue = "92521")] - pub const fn try_new_uninit_in(alloc: A) -> Result<Box<mem::MaybeUninit<T>, A>, AllocError> + pub fn try_new_uninit_in(alloc: A) -> Result<Box<mem::MaybeUninit<T>, A>, AllocError> where - A: ~const Allocator + ~const Destruct, + A: Allocator, { let layout = Layout::new::<mem::MaybeUninit<T>>(); let ptr = alloc.allocate(layout)?.cast(); @@ -492,13 +509,12 @@ impl<T, A: Allocator> Box<T, A> { /// /// [zeroed]: mem::MaybeUninit::zeroed #[unstable(feature = "allocator_api", issue = "32838")] - #[rustc_const_unstable(feature = "const_box", issue = "92521")] #[cfg(not(no_global_oom_handling))] // #[unstable(feature = "new_uninit", issue = "63291")] #[must_use] - pub const fn new_zeroed_in(alloc: A) -> Box<mem::MaybeUninit<T>, A> + pub fn new_zeroed_in(alloc: A) -> Box<mem::MaybeUninit<T>, A> where - A: ~const Allocator + ~const Destruct, + A: Allocator, { let layout = Layout::new::<mem::MaybeUninit<T>>(); // NOTE: Prefer match over unwrap_or_else since closure sometimes not inlineable. @@ -533,26 +549,29 @@ impl<T, A: Allocator> Box<T, A> { /// [zeroed]: mem::MaybeUninit::zeroed #[unstable(feature = "allocator_api", issue = "32838")] // #[unstable(feature = "new_uninit", issue = "63291")] - #[rustc_const_unstable(feature = "const_box", issue = "92521")] - pub const fn try_new_zeroed_in(alloc: A) -> Result<Box<mem::MaybeUninit<T>, A>, AllocError> + pub fn try_new_zeroed_in(alloc: A) -> Result<Box<mem::MaybeUninit<T>, A>, AllocError> where - A: ~const Allocator + ~const Destruct, + A: Allocator, { let layout = Layout::new::<mem::MaybeUninit<T>>(); let ptr = alloc.allocate_zeroed(layout)?.cast(); unsafe { Ok(Box::from_raw_in(ptr.as_ptr(), alloc)) } } - /// Constructs a new `Pin<Box<T, A>>`. If `T` does not implement `Unpin`, then + /// Constructs a new `Pin<Box<T, A>>`. If `T` does not implement [`Unpin`], then /// `x` will be pinned in memory and unable to be moved. + /// + /// Constructing and pinning of the `Box` can also be done in two steps: `Box::pin_in(x, alloc)` + /// does the same as <code>[Box::into_pin]\([Box::new_in]\(x, alloc))</code>. Consider using + /// [`into_pin`](Box::into_pin) if you already have a `Box<T, A>`, or if you want to + /// construct a (pinned) `Box` in a different way than with [`Box::new_in`]. #[cfg(not(no_global_oom_handling))] #[unstable(feature = "allocator_api", issue = "32838")] - #[rustc_const_unstable(feature = "const_box", issue = "92521")] #[must_use] #[inline(always)] - pub const fn pin_in(x: T, alloc: A) -> Pin<Self> + pub fn pin_in(x: T, alloc: A) -> Pin<Self> where - A: 'static + ~const Allocator + ~const Destruct, + A: 'static + Allocator, { Self::into_pin(Self::new_in(x, alloc)) } @@ -561,8 +580,7 @@ impl<T, A: Allocator> Box<T, A> { /// /// This conversion does not allocate on the heap and happens in place. #[unstable(feature = "box_into_boxed_slice", issue = "71582")] - #[rustc_const_unstable(feature = "const_box", issue = "92521")] - pub const fn into_boxed_slice(boxed: Self) -> Box<[T], A> { + pub fn into_boxed_slice(boxed: Self) -> Box<[T], A> { let (raw, alloc) = Box::into_raw_with_allocator(boxed); unsafe { Box::from_raw_in(raw as *mut [T; 1], alloc) } } @@ -579,12 +597,8 @@ impl<T, A: Allocator> Box<T, A> { /// assert_eq!(Box::into_inner(c), 5); /// ``` #[unstable(feature = "box_into_inner", issue = "80437")] - #[rustc_const_unstable(feature = "const_box", issue = "92521")] #[inline] - pub const fn into_inner(boxed: Self) -> T - where - Self: ~const Destruct, - { + pub fn into_inner(boxed: Self) -> T { *boxed } } @@ -798,9 +812,8 @@ impl<T, A: Allocator> Box<mem::MaybeUninit<T>, A> { /// assert_eq!(*five, 5) /// ``` #[unstable(feature = "new_uninit", issue = "63291")] - #[rustc_const_unstable(feature = "const_box", issue = "92521")] #[inline] - pub const unsafe fn assume_init(self) -> Box<T, A> { + pub unsafe fn assume_init(self) -> Box<T, A> { let (raw, alloc) = Box::into_raw_with_allocator(self); unsafe { Box::from_raw_in(raw as *mut T, alloc) } } @@ -833,9 +846,8 @@ impl<T, A: Allocator> Box<mem::MaybeUninit<T>, A> { /// } /// ``` #[unstable(feature = "new_uninit", issue = "63291")] - #[rustc_const_unstable(feature = "const_box", issue = "92521")] #[inline] - pub const fn write(mut boxed: Self, value: T) -> Box<T, A> { + pub fn write(mut boxed: Self, value: T) -> Box<T, A> { unsafe { (*boxed).write(value); boxed.assume_init() @@ -926,6 +938,7 @@ impl<T: ?Sized> Box<T> { /// [`Layout`]: crate::Layout #[stable(feature = "box_raw", since = "1.4.0")] #[inline] + #[must_use = "call `drop(Box::from_raw(ptr))` if you intend to drop the `Box`"] pub unsafe fn from_raw(raw: *mut T) -> Self { unsafe { Self::from_raw_in(raw, Global) } } @@ -1078,9 +1091,8 @@ impl<T: ?Sized, A: Allocator> Box<T, A> { /// /// [memory layout]: self#memory-layout #[unstable(feature = "allocator_api", issue = "32838")] - #[rustc_const_unstable(feature = "const_box", issue = "92521")] #[inline] - pub const fn into_raw_with_allocator(b: Self) -> (*mut T, A) { + pub fn into_raw_with_allocator(b: Self) -> (*mut T, A) { let (leaked, alloc) = Box::into_unique(b); (leaked.as_ptr(), alloc) } @@ -1090,10 +1102,9 @@ impl<T: ?Sized, A: Allocator> Box<T, A> { issue = "none", reason = "use `Box::leak(b).into()` or `Unique::from(Box::leak(b))` instead" )] - #[rustc_const_unstable(feature = "const_box", issue = "92521")] #[inline] #[doc(hidden)] - pub const fn into_unique(b: Self) -> (Unique<T>, A) { + pub fn into_unique(b: Self) -> (Unique<T>, A) { // Box is recognized as a "unique pointer" by Stacked Borrows, but internally it is a // raw pointer for the type system. Turning it directly into a raw pointer would not be // recognized as "releasing" the unique pointer to permit aliased raw accesses, @@ -1151,28 +1162,52 @@ impl<T: ?Sized, A: Allocator> Box<T, A> { /// assert_eq!(*static_ref, [4, 2, 3]); /// ``` #[stable(feature = "box_leak", since = "1.26.0")] - #[rustc_const_unstable(feature = "const_box", issue = "92521")] #[inline] - pub const fn leak<'a>(b: Self) -> &'a mut T + pub fn leak<'a>(b: Self) -> &'a mut T where A: 'a, { unsafe { &mut *mem::ManuallyDrop::new(b).0.as_ptr() } } - /// Converts a `Box<T>` into a `Pin<Box<T>>` + /// Converts a `Box<T>` into a `Pin<Box<T>>`. If `T` does not implement [`Unpin`], then + /// `*boxed` will be pinned in memory and unable to be moved. /// /// This conversion does not allocate on the heap and happens in place. /// /// This is also available via [`From`]. - #[unstable(feature = "box_into_pin", issue = "62370")] + /// + /// Constructing and pinning a `Box` with <code>Box::into_pin([Box::new]\(x))</code> + /// can also be written more concisely using <code>[Box::pin]\(x)</code>. + /// This `into_pin` method is useful if you already have a `Box<T>`, or you are + /// constructing a (pinned) `Box` in a different way than with [`Box::new`]. + /// + /// # Notes + /// + /// It's not recommended that crates add an impl like `From<Box<T>> for Pin<T>`, + /// as it'll introduce an ambiguity when calling `Pin::from`. + /// A demonstration of such a poor impl is shown below. + /// + /// ```compile_fail + /// # use std::pin::Pin; + /// struct Foo; // A type defined in this crate. + /// impl From<Box<()>> for Pin<Foo> { + /// fn from(_: Box<()>) -> Pin<Foo> { + /// Pin::new(Foo) + /// } + /// } + /// + /// let foo = Box::new(()); + /// let bar = Pin::from(foo); + /// ``` + #[stable(feature = "box_into_pin", since = "1.63.0")] #[rustc_const_unstable(feature = "const_box", issue = "92521")] pub const fn into_pin(boxed: Self) -> Pin<Self> where A: 'static, { // It's not possible to move or replace the insides of a `Pin<Box<T>>` - // when `T: !Unpin`, so it's safe to pin it directly without any + // when `T: !Unpin`, so it's safe to pin it directly without any // additional requirements. unsafe { Pin::new_unchecked(boxed) } } @@ -1189,15 +1224,16 @@ unsafe impl<#[may_dangle] T: ?Sized, A: Allocator> Drop for Box<T, A> { #[stable(feature = "rust1", since = "1.0.0")] impl<T: Default> Default for Box<T> { /// Creates a `Box<T>`, with the `Default` value for T. + #[inline] fn default() -> Self { - box T::default() + Box::new(T::default()) } } #[cfg(not(no_global_oom_handling))] #[stable(feature = "rust1", since = "1.0.0")] -#[rustc_const_unstable(feature = "const_default_impls", issue = "87864")] -impl<T> const Default for Box<[T]> { +impl<T> Default for Box<[T]> { + #[inline] fn default() -> Self { let ptr: Unique<[T]> = Unique::<[T; 0]>::dangling(); Box(ptr, Global) @@ -1206,8 +1242,8 @@ impl<T> const Default for Box<[T]> { #[cfg(not(no_global_oom_handling))] #[stable(feature = "default_box_extra", since = "1.17.0")] -#[rustc_const_unstable(feature = "const_default_impls", issue = "87864")] -impl const Default for Box<str> { +impl Default for Box<str> { + #[inline] fn default() -> Self { // SAFETY: This is the same as `Unique::cast<U>` but with an unsized `U = str`. let ptr: Unique<str> = unsafe { @@ -1403,26 +1439,60 @@ impl<T> From<T> for Box<T> { } #[stable(feature = "pin", since = "1.33.0")] -#[rustc_const_unstable(feature = "const_box", issue = "92521")] -impl<T: ?Sized, A: Allocator> const From<Box<T, A>> for Pin<Box<T, A>> +impl<T: ?Sized, A: Allocator> From<Box<T, A>> for Pin<Box<T, A>> where A: 'static, { - /// Converts a `Box<T>` into a `Pin<Box<T>>` + /// Converts a `Box<T>` into a `Pin<Box<T>>`. If `T` does not implement [`Unpin`], then + /// `*boxed` will be pinned in memory and unable to be moved. /// /// This conversion does not allocate on the heap and happens in place. + /// + /// This is also available via [`Box::into_pin`]. + /// + /// Constructing and pinning a `Box` with <code><Pin<Box\<T>>>::from([Box::new]\(x))</code> + /// can also be written more concisely using <code>[Box::pin]\(x)</code>. + /// This `From` implementation is useful if you already have a `Box<T>`, or you are + /// constructing a (pinned) `Box` in a different way than with [`Box::new`]. fn from(boxed: Box<T, A>) -> Self { Box::into_pin(boxed) } } +/// Specialization trait used for `From<&[T]>`. +#[cfg(not(no_global_oom_handling))] +trait BoxFromSlice<T> { + fn from_slice(slice: &[T]) -> Self; +} + +#[cfg(not(no_global_oom_handling))] +impl<T: Clone> BoxFromSlice<T> for Box<[T]> { + #[inline] + default fn from_slice(slice: &[T]) -> Self { + slice.to_vec().into_boxed_slice() + } +} + +#[cfg(not(no_global_oom_handling))] +impl<T: Copy> BoxFromSlice<T> for Box<[T]> { + #[inline] + fn from_slice(slice: &[T]) -> Self { + let len = slice.len(); + let buf = RawVec::with_capacity(len); + unsafe { + ptr::copy_nonoverlapping(slice.as_ptr(), buf.ptr(), len); + buf.into_box(slice.len()).assume_init() + } + } +} + #[cfg(not(no_global_oom_handling))] #[stable(feature = "box_from_slice", since = "1.17.0")] -impl<T: Copy> From<&[T]> for Box<[T]> { +impl<T: Clone> From<&[T]> for Box<[T]> { /// Converts a `&[T]` into a `Box<[T]>` /// /// This conversion allocates on the heap - /// and performs a copy of `slice`. + /// and performs a copy of `slice` and its contents. /// /// # Examples /// ```rust @@ -1432,19 +1502,15 @@ impl<T: Copy> From<&[T]> for Box<[T]> { /// /// println!("{boxed_slice:?}"); /// ``` + #[inline] fn from(slice: &[T]) -> Box<[T]> { - let len = slice.len(); - let buf = RawVec::with_capacity(len); - unsafe { - ptr::copy_nonoverlapping(slice.as_ptr(), buf.ptr(), len); - buf.into_box(slice.len()).assume_init() - } + <Self as BoxFromSlice<T>>::from_slice(slice) } } #[cfg(not(no_global_oom_handling))] #[stable(feature = "box_from_cow", since = "1.45.0")] -impl<T: Copy> From<Cow<'_, [T]>> for Box<[T]> { +impl<T: Clone> From<Cow<'_, [T]>> for Box<[T]> { /// Converts a `Cow<'_, [T]>` into a `Box<[T]>` /// /// When `cow` is the `Cow::Borrowed` variant, this @@ -1554,10 +1620,26 @@ impl<T, const N: usize> From<[T; N]> for Box<[T]> { /// println!("{boxed:?}"); /// ``` fn from(array: [T; N]) -> Box<[T]> { - box array + Box::new(array) } } +/// Casts a boxed slice to a boxed array. +/// +/// # Safety +/// +/// `boxed_slice.len()` must be exactly `N`. +unsafe fn boxed_slice_as_array_unchecked<T, A: Allocator, const N: usize>( + boxed_slice: Box<[T], A>, +) -> Box<[T; N], A> { + debug_assert_eq!(boxed_slice.len(), N); + + let (ptr, alloc) = Box::into_raw_with_allocator(boxed_slice); + // SAFETY: Pointer and allocator came from an existing box, + // and our safety condition requires that the length is exactly `N` + unsafe { Box::from_raw_in(ptr as *mut [T; N], alloc) } +} + #[stable(feature = "boxed_slice_try_from", since = "1.43.0")] impl<T, const N: usize> TryFrom<Box<[T]>> for Box<[T; N]> { type Error = Box<[T]>; @@ -1573,13 +1655,46 @@ impl<T, const N: usize> TryFrom<Box<[T]>> for Box<[T; N]> { /// `boxed_slice.len()` does not equal `N`. fn try_from(boxed_slice: Box<[T]>) -> Result<Self, Self::Error> { if boxed_slice.len() == N { - Ok(unsafe { Box::from_raw(Box::into_raw(boxed_slice) as *mut [T; N]) }) + Ok(unsafe { boxed_slice_as_array_unchecked(boxed_slice) }) } else { Err(boxed_slice) } } } +#[cfg(not(no_global_oom_handling))] +#[stable(feature = "boxed_array_try_from_vec", since = "1.66.0")] +impl<T, const N: usize> TryFrom<Vec<T>> for Box<[T; N]> { + type Error = Vec<T>; + + /// Attempts to convert a `Vec<T>` into a `Box<[T; N]>`. + /// + /// Like [`Vec::into_boxed_slice`], this is in-place if `vec.capacity() == N`, + /// but will require a reallocation otherwise. + /// + /// # Errors + /// + /// Returns the original `Vec<T>` in the `Err` variant if + /// `boxed_slice.len()` does not equal `N`. + /// + /// # Examples + /// + /// This can be used with [`vec!`] to create an array on the heap: + /// + /// ``` + /// let state: Box<[f32; 100]> = vec![1.0; 100].try_into().unwrap(); + /// assert_eq!(state.len(), 100); + /// ``` + fn try_from(vec: Vec<T>) -> Result<Self, Self::Error> { + if vec.len() == N { + let boxed_slice = vec.into_boxed_slice(); + Ok(unsafe { boxed_slice_as_array_unchecked(boxed_slice) }) + } else { + Err(vec) + } + } +} + impl<A: Allocator> Box<dyn Any, A> { /// Attempt to downcast the box to a concrete type. /// @@ -1783,8 +1898,7 @@ impl<T: ?Sized, A: Allocator> fmt::Pointer for Box<T, A> { } #[stable(feature = "rust1", since = "1.0.0")] -#[rustc_const_unstable(feature = "const_box", issue = "92521")] -impl<T: ?Sized, A: Allocator> const Deref for Box<T, A> { +impl<T: ?Sized, A: Allocator> Deref for Box<T, A> { type Target = T; fn deref(&self) -> &T { @@ -1793,8 +1907,7 @@ impl<T: ?Sized, A: Allocator> const Deref for Box<T, A> { } #[stable(feature = "rust1", since = "1.0.0")] -#[rustc_const_unstable(feature = "const_box", issue = "92521")] -impl<T: ?Sized, A: Allocator> const DerefMut for Box<T, A> { +impl<T: ?Sized, A: Allocator> DerefMut for Box<T, A> { fn deref_mut(&mut self) -> &mut T { &mut **self } @@ -1869,7 +1982,7 @@ impl<I: ExactSizeIterator + ?Sized, A: Allocator> ExactSizeIterator for Box<I, A impl<I: FusedIterator + ?Sized, A: Allocator> FusedIterator for Box<I, A> {} #[stable(feature = "boxed_closure_impls", since = "1.35.0")] -impl<Args, F: FnOnce<Args> + ?Sized, A: Allocator> FnOnce<Args> for Box<F, A> { +impl<Args: Tuple, F: FnOnce<Args> + ?Sized, A: Allocator> FnOnce<Args> for Box<F, A> { type Output = <F as FnOnce<Args>>::Output; extern "rust-call" fn call_once(self, args: Args) -> Self::Output { @@ -1878,20 +1991,20 @@ impl<Args, F: FnOnce<Args> + ?Sized, A: Allocator> FnOnce<Args> for Box<F, A> { } #[stable(feature = "boxed_closure_impls", since = "1.35.0")] -impl<Args, F: FnMut<Args> + ?Sized, A: Allocator> FnMut<Args> for Box<F, A> { +impl<Args: Tuple, F: FnMut<Args> + ?Sized, A: Allocator> FnMut<Args> for Box<F, A> { extern "rust-call" fn call_mut(&mut self, args: Args) -> Self::Output { <F as FnMut<Args>>::call_mut(self, args) } } #[stable(feature = "boxed_closure_impls", since = "1.35.0")] -impl<Args, F: Fn<Args> + ?Sized, A: Allocator> Fn<Args> for Box<F, A> { +impl<Args: Tuple, F: Fn<Args> + ?Sized, A: Allocator> Fn<Args> for Box<F, A> { extern "rust-call" fn call(&self, args: Args) -> Self::Output { <F as Fn<Args>>::call(self, args) } } -#[unstable(feature = "coerce_unsized", issue = "27732")] +#[unstable(feature = "coerce_unsized", issue = "18598")] impl<T: ?Sized + Unsize<U>, U: ?Sized, A: Allocator> CoerceUnsized<Box<U, A>> for Box<T, A> {} #[unstable(feature = "dispatch_from_dyn", issue = "none")] @@ -1973,8 +2086,7 @@ impl<T: ?Sized, A: Allocator> AsMut<T> for Box<T, A> { * could have a method to project a Pin<T> from it. */ #[stable(feature = "pin", since = "1.33.0")] -#[rustc_const_unstable(feature = "const_box", issue = "92521")] -impl<T: ?Sized, A: Allocator> const Unpin for Box<T, A> where A: 'static {} +impl<T: ?Sized, A: Allocator> Unpin for Box<T, A> where A: 'static {} #[unstable(feature = "generator_trait", issue = "43122")] impl<G: ?Sized + Generator<R> + Unpin, R, A: Allocator> Generator<R> for Box<G, A> @@ -2026,3 +2138,292 @@ impl<S: ?Sized + AsyncIterator + Unpin> AsyncIterator for Box<S> { (**self).size_hint() } } + +impl dyn Error { + #[inline] + #[stable(feature = "error_downcast", since = "1.3.0")] + #[rustc_allow_incoherent_impl] + /// Attempts to downcast the box to a concrete type. + pub fn downcast<T: Error + 'static>(self: Box<Self>) -> Result<Box<T>, Box<dyn Error>> { + if self.is::<T>() { + unsafe { + let raw: *mut dyn Error = Box::into_raw(self); + Ok(Box::from_raw(raw as *mut T)) + } + } else { + Err(self) + } + } +} + +impl dyn Error + Send { + #[inline] + #[stable(feature = "error_downcast", since = "1.3.0")] + #[rustc_allow_incoherent_impl] + /// Attempts to downcast the box to a concrete type. + pub fn downcast<T: Error + 'static>(self: Box<Self>) -> Result<Box<T>, Box<dyn Error + Send>> { + let err: Box<dyn Error> = self; + <dyn Error>::downcast(err).map_err(|s| unsafe { + // Reapply the `Send` marker. + mem::transmute::<Box<dyn Error>, Box<dyn Error + Send>>(s) + }) + } +} + +impl dyn Error + Send + Sync { + #[inline] + #[stable(feature = "error_downcast", since = "1.3.0")] + #[rustc_allow_incoherent_impl] + /// Attempts to downcast the box to a concrete type. + pub fn downcast<T: Error + 'static>(self: Box<Self>) -> Result<Box<T>, Box<Self>> { + let err: Box<dyn Error> = self; + <dyn Error>::downcast(err).map_err(|s| unsafe { + // Reapply the `Send + Sync` marker. + mem::transmute::<Box<dyn Error>, Box<dyn Error + Send + Sync>>(s) + }) + } +} + +#[cfg(not(no_global_oom_handling))] +#[stable(feature = "rust1", since = "1.0.0")] +impl<'a, E: Error + 'a> From<E> for Box<dyn Error + 'a> { + /// Converts a type of [`Error`] into a box of dyn [`Error`]. + /// + /// # Examples + /// + /// ``` + /// use std::error::Error; + /// use std::fmt; + /// use std::mem; + /// + /// #[derive(Debug)] + /// struct AnError; + /// + /// impl fmt::Display for AnError { + /// fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + /// write!(f, "An error") + /// } + /// } + /// + /// impl Error for AnError {} + /// + /// let an_error = AnError; + /// assert!(0 == mem::size_of_val(&an_error)); + /// let a_boxed_error = Box::<dyn Error>::from(an_error); + /// assert!(mem::size_of::<Box<dyn Error>>() == mem::size_of_val(&a_boxed_error)) + /// ``` + fn from(err: E) -> Box<dyn Error + 'a> { + Box::new(err) + } +} + +#[cfg(not(no_global_oom_handling))] +#[stable(feature = "rust1", since = "1.0.0")] +impl<'a, E: Error + Send + Sync + 'a> From<E> for Box<dyn Error + Send + Sync + 'a> { + /// Converts a type of [`Error`] + [`Send`] + [`Sync`] into a box of + /// dyn [`Error`] + [`Send`] + [`Sync`]. + /// + /// # Examples + /// + /// ``` + /// use std::error::Error; + /// use std::fmt; + /// use std::mem; + /// + /// #[derive(Debug)] + /// struct AnError; + /// + /// impl fmt::Display for AnError { + /// fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + /// write!(f, "An error") + /// } + /// } + /// + /// impl Error for AnError {} + /// + /// unsafe impl Send for AnError {} + /// + /// unsafe impl Sync for AnError {} + /// + /// let an_error = AnError; + /// assert!(0 == mem::size_of_val(&an_error)); + /// let a_boxed_error = Box::<dyn Error + Send + Sync>::from(an_error); + /// assert!( + /// mem::size_of::<Box<dyn Error + Send + Sync>>() == mem::size_of_val(&a_boxed_error)) + /// ``` + fn from(err: E) -> Box<dyn Error + Send + Sync + 'a> { + Box::new(err) + } +} + +#[cfg(not(no_global_oom_handling))] +#[stable(feature = "rust1", since = "1.0.0")] +impl From<String> for Box<dyn Error + Send + Sync> { + /// Converts a [`String`] into a box of dyn [`Error`] + [`Send`] + [`Sync`]. + /// + /// # Examples + /// + /// ``` + /// use std::error::Error; + /// use std::mem; + /// + /// let a_string_error = "a string error".to_string(); + /// let a_boxed_error = Box::<dyn Error + Send + Sync>::from(a_string_error); + /// assert!( + /// mem::size_of::<Box<dyn Error + Send + Sync>>() == mem::size_of_val(&a_boxed_error)) + /// ``` + #[inline] + fn from(err: String) -> Box<dyn Error + Send + Sync> { + struct StringError(String); + + impl Error for StringError { + #[allow(deprecated)] + fn description(&self) -> &str { + &self.0 + } + } + + impl fmt::Display for StringError { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + fmt::Display::fmt(&self.0, f) + } + } + + // Purposefully skip printing "StringError(..)" + impl fmt::Debug for StringError { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + fmt::Debug::fmt(&self.0, f) + } + } + + Box::new(StringError(err)) + } +} + +#[cfg(not(no_global_oom_handling))] +#[stable(feature = "string_box_error", since = "1.6.0")] +impl From<String> for Box<dyn Error> { + /// Converts a [`String`] into a box of dyn [`Error`]. + /// + /// # Examples + /// + /// ``` + /// use std::error::Error; + /// use std::mem; + /// + /// let a_string_error = "a string error".to_string(); + /// let a_boxed_error = Box::<dyn Error>::from(a_string_error); + /// assert!(mem::size_of::<Box<dyn Error>>() == mem::size_of_val(&a_boxed_error)) + /// ``` + fn from(str_err: String) -> Box<dyn Error> { + let err1: Box<dyn Error + Send + Sync> = From::from(str_err); + let err2: Box<dyn Error> = err1; + err2 + } +} + +#[cfg(not(no_global_oom_handling))] +#[stable(feature = "rust1", since = "1.0.0")] +impl<'a> From<&str> for Box<dyn Error + Send + Sync + 'a> { + /// Converts a [`str`] into a box of dyn [`Error`] + [`Send`] + [`Sync`]. + /// + /// [`str`]: prim@str + /// + /// # Examples + /// + /// ``` + /// use std::error::Error; + /// use std::mem; + /// + /// let a_str_error = "a str error"; + /// let a_boxed_error = Box::<dyn Error + Send + Sync>::from(a_str_error); + /// assert!( + /// mem::size_of::<Box<dyn Error + Send + Sync>>() == mem::size_of_val(&a_boxed_error)) + /// ``` + #[inline] + fn from(err: &str) -> Box<dyn Error + Send + Sync + 'a> { + From::from(String::from(err)) + } +} + +#[cfg(not(no_global_oom_handling))] +#[stable(feature = "string_box_error", since = "1.6.0")] +impl From<&str> for Box<dyn Error> { + /// Converts a [`str`] into a box of dyn [`Error`]. + /// + /// [`str`]: prim@str + /// + /// # Examples + /// + /// ``` + /// use std::error::Error; + /// use std::mem; + /// + /// let a_str_error = "a str error"; + /// let a_boxed_error = Box::<dyn Error>::from(a_str_error); + /// assert!(mem::size_of::<Box<dyn Error>>() == mem::size_of_val(&a_boxed_error)) + /// ``` + fn from(err: &str) -> Box<dyn Error> { + From::from(String::from(err)) + } +} + +#[cfg(not(no_global_oom_handling))] +#[stable(feature = "cow_box_error", since = "1.22.0")] +impl<'a, 'b> From<Cow<'b, str>> for Box<dyn Error + Send + Sync + 'a> { + /// Converts a [`Cow`] into a box of dyn [`Error`] + [`Send`] + [`Sync`]. + /// + /// # Examples + /// + /// ``` + /// use std::error::Error; + /// use std::mem; + /// use std::borrow::Cow; + /// + /// let a_cow_str_error = Cow::from("a str error"); + /// let a_boxed_error = Box::<dyn Error + Send + Sync>::from(a_cow_str_error); + /// assert!( + /// mem::size_of::<Box<dyn Error + Send + Sync>>() == mem::size_of_val(&a_boxed_error)) + /// ``` + fn from(err: Cow<'b, str>) -> Box<dyn Error + Send + Sync + 'a> { + From::from(String::from(err)) + } +} + +#[cfg(not(no_global_oom_handling))] +#[stable(feature = "cow_box_error", since = "1.22.0")] +impl<'a> From<Cow<'a, str>> for Box<dyn Error> { + /// Converts a [`Cow`] into a box of dyn [`Error`]. + /// + /// # Examples + /// + /// ``` + /// use std::error::Error; + /// use std::mem; + /// use std::borrow::Cow; + /// + /// let a_cow_str_error = Cow::from("a str error"); + /// let a_boxed_error = Box::<dyn Error>::from(a_cow_str_error); + /// assert!(mem::size_of::<Box<dyn Error>>() == mem::size_of_val(&a_boxed_error)) + /// ``` + fn from(err: Cow<'a, str>) -> Box<dyn Error> { + From::from(String::from(err)) + } +} + +#[stable(feature = "box_error", since = "1.8.0")] +impl<T: core::error::Error> core::error::Error for Box<T> { + #[allow(deprecated, deprecated_in_future)] + fn description(&self) -> &str { + core::error::Error::description(&**self) + } + + #[allow(deprecated)] + fn cause(&self) -> Option<&dyn core::error::Error> { + core::error::Error::cause(&**self) + } + + fn source(&self) -> Option<&(dyn core::error::Error + 'static)> { + core::error::Error::source(&**self) + } +} |