diff options
Diffstat (limited to '')
| -rw-r--r-- | library/alloc/src/boxed.rs | 68 |
1 files changed, 51 insertions, 17 deletions
diff --git a/library/alloc/src/boxed.rs b/library/alloc/src/boxed.rs index 65e323c9e..d6681a317 100644 --- a/library/alloc/src/boxed.rs +++ b/library/alloc/src/boxed.rs @@ -151,7 +151,6 @@ use core::async_iter::AsyncIterator; use core::borrow; use core::cmp::Ordering; use core::convert::{From, TryFrom}; -#[cfg(not(bootstrap))] use core::error::Error; use core::fmt; use core::future::Future; @@ -176,7 +175,6 @@ use crate::borrow::Cow; use crate::raw_vec::RawVec; #[cfg(not(no_global_oom_handling))] use crate::str::from_boxed_utf8_unchecked; -#[cfg(not(bootstrap))] #[cfg(not(no_global_oom_handling))] use crate::string::String; #[cfg(not(no_global_oom_handling))] @@ -1622,6 +1620,22 @@ impl<T, const N: usize> From<[T; N]> for Box<[T]> { } } +/// 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]>; @@ -1637,13 +1651,46 @@ 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. /// @@ -2037,8 +2084,7 @@ 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> @@ -2091,7 +2137,6 @@ impl<S: ?Sized + AsyncIterator + Unpin> AsyncIterator for Box<S> { } } -#[cfg(not(bootstrap))] impl dyn Error { #[inline] #[stable(feature = "error_downcast", since = "1.3.0")] @@ -2109,7 +2154,6 @@ impl dyn Error { } } -#[cfg(not(bootstrap))] impl dyn Error + Send { #[inline] #[stable(feature = "error_downcast", since = "1.3.0")] @@ -2124,7 +2168,6 @@ impl dyn Error + Send { } } -#[cfg(not(bootstrap))] impl dyn Error + Send + Sync { #[inline] #[stable(feature = "error_downcast", since = "1.3.0")] @@ -2139,7 +2182,6 @@ impl dyn Error + Send + Sync { } } -#[cfg(not(bootstrap))] #[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> { @@ -2173,7 +2215,6 @@ impl<'a, E: Error + 'a> From<E> for Box<dyn Error + 'a> { } } -#[cfg(not(bootstrap))] #[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> { @@ -2213,7 +2254,6 @@ impl<'a, E: Error + Send + Sync + 'a> From<E> for Box<dyn Error + Send + Sync + } } -#[cfg(not(bootstrap))] #[cfg(not(no_global_oom_handling))] #[stable(feature = "rust1", since = "1.0.0")] impl From<String> for Box<dyn Error + Send + Sync> { @@ -2258,7 +2298,6 @@ impl From<String> for Box<dyn Error + Send + Sync> { } } -#[cfg(not(bootstrap))] #[cfg(not(no_global_oom_handling))] #[stable(feature = "string_box_error", since = "1.6.0")] impl From<String> for Box<dyn Error> { @@ -2281,7 +2320,6 @@ impl From<String> for Box<dyn Error> { } } -#[cfg(not(bootstrap))] #[cfg(not(no_global_oom_handling))] #[stable(feature = "rust1", since = "1.0.0")] impl<'a> From<&str> for Box<dyn Error + Send + Sync + 'a> { @@ -2306,7 +2344,6 @@ impl<'a> From<&str> for Box<dyn Error + Send + Sync + 'a> { } } -#[cfg(not(bootstrap))] #[cfg(not(no_global_oom_handling))] #[stable(feature = "string_box_error", since = "1.6.0")] impl From<&str> for Box<dyn Error> { @@ -2329,7 +2366,6 @@ impl From<&str> for Box<dyn Error> { } } -#[cfg(not(bootstrap))] #[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> { @@ -2352,7 +2388,6 @@ impl<'a, 'b> From<Cow<'b, str>> for Box<dyn Error + Send + Sync + 'a> { } } -#[cfg(not(bootstrap))] #[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> { @@ -2374,7 +2409,6 @@ impl<'a> From<Cow<'a, str>> for Box<dyn Error> { } } -#[cfg(not(bootstrap))] #[stable(feature = "box_error", since = "1.8.0")] impl<T: core::error::Error> core::error::Error for Box<T> { #[allow(deprecated, deprecated_in_future)] |