The Rust team is happy to announce a new version of Rust, 1.83.0. Rust is a programming language empowering everyone to build reliable and efficient software. If you have a previous version of Rust installed via rustup, you can get 1.83.0 with: rustup $ rustup update stable $ rustup update stable If you don't have it already, you can get rustup from the appropriate page on our website, and check out the detailed release notes for 1.83.0. get rustup detailed release notes for 1.83.0 If you'd like to help us out by testing future releases, you might consider updating locally to use the beta channel (rustup default beta) or the nightly channel (rustup default nightly). Please report any bugs you might come across! rustup default beta rustup default nightly report What's in 1.83.0 stable New const capabilities This release includes several large extensions to what code running in const contexts can do. This refers to all code that the compiler has to evaluate at compile-time: the initial value of const and static items, array lengths, enum discriminant values, const generic arguments, and functions callable from such contexts (const fn). const static const fn References to statics. So far, const contexts except for the initializer expression of a static item were forbidden from referencing static items. This limitation has now been lifted: References to statics. static static static S: i32 = 25;
const C: &i32 = &S; static S: i32 = 25;
const C: &i32 = &S; Note, however, that reading the value of a mutable or interior mutable static is still not permitted in const contexts. Furthermore, the final value of a constant may not reference any mutable or interior mutable statics: static mut S: i32 = 0;

const C1: i32 = unsafe { S };
// error: constant accesses mutable global memory

const C2: &i32 = unsafe { &S };
// error: encountered reference to mutable memory in `const` static mut S: i32 = 0;

const C1: i32 = unsafe { S };
// error: constant accesses mutable global memory

const C2: &i32 = unsafe { &S };
// error: encountered reference to mutable memory in `const` These limitations ensure that constants are still "constant": the value they evaluate to, and their meaning as a pattern (which can involve dereferencing references), will be the same throughout the entire program execution. That said, a constant is permitted to evaluate to a raw pointer that points to a mutable or interior mutable static: static mut S: i32 = 64;
const C: *mut i32 = &raw mut S; static mut S: i32 = 64;
const C: *mut i32 = &raw mut S; Mutable references and pointers. It is now possible to use mutable references in const contexts: Mutable references and pointers. const fn inc(x: &mut i32) {
    *x += 1;
}

const C: i32 = {
    let mut c = 41;
    inc(&mut c);
    c
}; const fn inc(x: &mut i32) {
    *x += 1;
}

const C: i32 = {
    let mut c = 41;
    inc(&mut c);
    c
}; Mutable raw pointers and interior mutability are also supported: use std::cell::UnsafeCell;

const C: i32 = {
    let c = UnsafeCell::new(41);
    unsafe { *c.get() += 1 };
    c.into_inner()
}; use std::cell::UnsafeCell;

const C: i32 = {
    let c = UnsafeCell::new(41);
    unsafe { *c.get() += 1 };
    c.into_inner()
}; However, mutable references and pointers can only be used inside the computation of a constant, they cannot become a part of the final value of the constant: inside const C: &mut i32 = &mut 4;
// error[E0764]: mutable references are not allowed in the final value of constants const C: &mut i32 = &mut 4;
// error[E0764]: mutable references are not allowed in the final value of constants This release also ships with a whole bag of new functions that are now stable in const contexts (see the end of the "Stabilized APIs" section). These new capabilities and stabilized APIs unblock an entire new category of code to be executed inside const contexts, and we are excited to see how the Rust ecosystem will make use of this! Stabilized APIs BufRead::skip_until
ControlFlow::break_value
ControlFlow::continue_value
ControlFlow::map_break
ControlFlow::map_continue
DebugList::finish_non_exhaustive
DebugMap::finish_non_exhaustive
DebugSet::finish_non_exhaustive
DebugTuple::finish_non_exhaustive
ErrorKind::ArgumentListTooLong
ErrorKind::Deadlock
ErrorKind::DirectoryNotEmpty
ErrorKind::ExecutableFileBusy
ErrorKind::FileTooLarge
ErrorKind::HostUnreachable
ErrorKind::IsADirectory
ErrorKind::NetworkDown
ErrorKind::NetworkUnreachable
ErrorKind::NotADirectory
ErrorKind::NotSeekable
ErrorKind::ReadOnlyFilesystem
ErrorKind::ResourceBusy
ErrorKind::StaleNetworkFileHandle
ErrorKind::StorageFull
ErrorKind::TooManyLinks
Option::get_or_insert_default
Waker::data
Waker::new
Waker::vtable
char::MIN
hash_map::Entry::insert_entry
hash_map::VacantEntry::insert_entry BufRead::skip_until BufRead::skip_until ControlFlow::break_value ControlFlow::break_value ControlFlow::continue_value ControlFlow::continue_value ControlFlow::map_break ControlFlow::map_break ControlFlow::map_continue ControlFlow::map_continue DebugList::finish_non_exhaustive DebugList::finish_non_exhaustive DebugMap::finish_non_exhaustive DebugMap::finish_non_exhaustive DebugSet::finish_non_exhaustive DebugSet::finish_non_exhaustive DebugTuple::finish_non_exhaustive DebugTuple::finish_non_exhaustive ErrorKind::ArgumentListTooLong ErrorKind::ArgumentListTooLong ErrorKind::Deadlock ErrorKind::Deadlock ErrorKind::DirectoryNotEmpty ErrorKind::DirectoryNotEmpty ErrorKind::ExecutableFileBusy ErrorKind::ExecutableFileBusy ErrorKind::FileTooLarge ErrorKind::FileTooLarge ErrorKind::HostUnreachable ErrorKind::HostUnreachable ErrorKind::IsADirectory ErrorKind::IsADirectory ErrorKind::NetworkDown ErrorKind::NetworkDown ErrorKind::NetworkUnreachable ErrorKind::NetworkUnreachable ErrorKind::NotADirectory ErrorKind::NotADirectory ErrorKind::NotSeekable ErrorKind::NotSeekable ErrorKind::ReadOnlyFilesystem ErrorKind::ReadOnlyFilesystem ErrorKind::ResourceBusy ErrorKind::ResourceBusy ErrorKind::StaleNetworkFileHandle ErrorKind::StaleNetworkFileHandle ErrorKind::StorageFull ErrorKind::StorageFull ErrorKind::TooManyLinks ErrorKind::TooManyLinks Option::get_or_insert_default Option::get_or_insert_default Waker::data Waker::data Waker::new Waker::new Waker::vtable Waker::vtable char::MIN char::MIN hash_map::Entry::insert_entry hash_map::Entry::insert_entry hash_map::VacantEntry::insert_entry hash_map::VacantEntry::insert_entry These APIs are now stable in const contexts: Cell::into_inner
Duration::as_secs_f32
Duration::as_secs_f64
Duration::div_duration_f32
Duration::div_duration_f64
MaybeUninit::as_mut_ptr
NonNull::as_mut
NonNull::copy_from
NonNull::copy_from_nonoverlapping
NonNull::copy_to
NonNull::copy_to_nonoverlapping
NonNull::slice_from_raw_parts
NonNull::write
NonNull::write_bytes
NonNull::write_unaligned
OnceCell::into_inner
Option::as_mut
Option::expect
Option::replace
Option::take
Option::unwrap
Option::unwrap_unchecked
Option::<&_>::copied
Option::<&mut _>::copied
Option::<Option<_>>::flatten
Option::<Result<_, _>>::transpose
RefCell::into_inner
Result::as_mut
Result::<&_, _>::copied
Result::<&mut _, _>::copied
Result::<Option<_>, _>::transpose
UnsafeCell::get_mut
UnsafeCell::into_inner
array::from_mut
char::encode_utf8
{float}::classify
{float}::is_finite
{float}::is_infinite
{float}::is_nan
{float}::is_normal
{float}::is_sign_negative
{float}::is_sign_positive
{float}::is_subnormal
{float}::from_bits
{float}::from_be_bytes
{float}::from_le_bytes
{float}::from_ne_bytes
{float}::to_bits
{float}::to_be_bytes
{float}::to_le_bytes
{float}::to_ne_bytes
mem::replace
ptr::replace
ptr::slice_from_raw_parts_mut
ptr::write
ptr::write_unaligned
<*const _>::copy_to
<*const _>::copy_to_nonoverlapping
<*mut _>::copy_from
<*mut _>::copy_from_nonoverlapping
<*mut _>::copy_to
<*mut _>::copy_to_nonoverlapping
<*mut _>::write
<*mut _>::write_bytes
<*mut _>::write_unaligned
slice::from_mut
slice::from_raw_parts_mut
<[_]>::first_mut
<[_]>::last_mut
<[_]>::first_chunk_mut
<[_]>::last_chunk_mut
<[_]>::split_at_mut
<[_]>::split_at_mut_checked
<[_]>::split_at_mut_unchecked
<[_]>::split_first_mut
<[_]>::split_last_mut
<[_]>::split_first_chunk_mut
<[_]>::split_last_chunk_mut
str::as_bytes_mut
str::as_mut_ptr
str::from_utf8_unchecked_mut Cell::into_inner Cell::into_inner Duration::as_secs_f32 Duration::as_secs_f32 Duration::as_secs_f64 Duration::as_secs_f64 Duration::div_duration_f32 Duration::div_duration_f32 Duration::div_duration_f64 Duration::div_duration_f64 MaybeUninit::as_mut_ptr MaybeUninit::as_mut_ptr NonNull::as_mut NonNull::as_mut NonNull::copy_from NonNull::copy_from NonNull::copy_from_nonoverlapping NonNull::copy_from_nonoverlapping NonNull::copy_to NonNull::copy_to NonNull::copy_to_nonoverlapping NonNull::copy_to_nonoverlapping NonNull::slice_from_raw_parts NonNull::slice_from_raw_parts NonNull::write NonNull::write NonNull::write_bytes NonNull::write_bytes NonNull::write_unaligned NonNull::write_unaligned OnceCell::into_inner OnceCell::into_inner Option::as_mut Option::as_mut Option::expect Option::expect Option::replace Option::replace Option::take Option::take Option::unwrap Option::unwrap Option::unwrap_unchecked Option::unwrap_unchecked Option::<&_>::copied Option::<&_>::copied Option::<&mut _>::copied Option::<&mut _>::copied Option::<Option<_>>::flatten Option::<Option<_>>::flatten Option::<Result<_, _>>::transpose Option::<Result<_, _>>::transpose RefCell::into_inner RefCell::into_inner Result::as_mut Result::as_mut Result::<&_, _>::copied Result::<&_, _>::copied Result::<&mut _, _>::copied Result::<&mut _, _>::copied Result::<Option<_>, _>::transpose Result::<Option<_>, _>::transpose UnsafeCell::get_mut UnsafeCell::get_mut UnsafeCell::into_inner UnsafeCell::into_inner array::from_mut array::from_mut char::encode_utf8 char::encode_utf8 {float}::classify {float}::classify {float}::is_finite {float}::is_finite {float}::is_infinite {float}::is_infinite {float}::is_nan {float}::is_nan {float}::is_normal {float}::is_normal {float}::is_sign_negative {float}::is_sign_negative {float}::is_sign_positive {float}::is_sign_positive {float}::is_subnormal {float}::is_subnormal {float}::from_bits {float}::from_bits {float}::from_be_bytes {float}::from_be_bytes {float}::from_le_bytes {float}::from_le_bytes {float}::from_ne_bytes {float}::from_ne_bytes {float}::to_bits {float}::to_bits {float}::to_be_bytes {float}::to_be_bytes {float}::to_le_bytes {float}::to_le_bytes {float}::to_ne_bytes {float}::to_ne_bytes mem::replace mem::replace ptr::replace ptr::replace ptr::slice_from_raw_parts_mut ptr::slice_from_raw_parts_mut ptr::write ptr::write ptr::write_unaligned ptr::write_unaligned <*const _>::copy_to <*const _>::copy_to <*const _>::copy_to_nonoverlapping <*const _>::copy_to_nonoverlapping <*mut _>::copy_from <*mut _>::copy_from <*mut _>::copy_from_nonoverlapping <*mut _>::copy_from_nonoverlapping <*mut _>::copy_to <*mut _>::copy_to <*mut _>::copy_to_nonoverlapping <*mut _>::copy_to_nonoverlapping <*mut _>::write <*mut _>::write <*mut _>::write_bytes <*mut _>::write_bytes <*mut _>::write_unaligned <*mut _>::write_unaligned slice::from_mut slice::from_mut slice::from_raw_parts_mut slice::from_raw_parts_mut <[_]>::first_mut <[_]>::first_mut <[_]>::last_mut <[_]>::last_mut <[_]>::first_chunk_mut <[_]>::first_chunk_mut <[_]>::last_chunk_mut <[_]>::last_chunk_mut <[_]>::split_at_mut <[_]>::split_at_mut <[_]>::split_at_mut_checked <[_]>::split_at_mut_checked <[_]>::split_at_mut_unchecked <[_]>::split_at_mut_unchecked <[_]>::split_first_mut <[_]>::split_first_mut <[_]>::split_last_mut <[_]>::split_last_mut <[_]>::split_first_chunk_mut <[_]>::split_first_chunk_mut <[_]>::split_last_chunk_mut <[_]>::split_last_chunk_mut str::as_bytes_mut str::as_bytes_mut str::as_mut_ptr str::as_mut_ptr str::from_utf8_unchecked_mut str::from_utf8_unchecked_mut Other changes Check out everything that changed in Rust, Cargo, and Clippy. Rust Cargo Clippy Contributors to 1.83.0 Many people came together to create Rust 1.83.0. We couldn't have done it without all of you. Thanks! Thanks! The Rust Release Team The Rust Release Team Also published here Also published here here Photo by Jr Korpa on Unsplash Photo by Jr Korpa on Unsplash Jr Korpa Unsplash

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