1.84.0

Language

• Allow #[deny] inside #[forbid] as a no-op
• Show a warning when -Ctarget-feature is used to toggle features that can lead to unsoundness due to ABI mismatches
• Use the next-generation trait solver in coherence
• Allow coercions to drop the principal of trait objects
• Support / as the path separator for include!() in all cases on Windows
• Taking a raw ref (raw (const|mut)) of a deref of a pointer (*ptr) is now safe
• Stabilize s390x inline assembly
• Stabilize Arm64EC inline assembly
• Lint against creating pointers to immediately dropped temporaries
• Execute drop glue when unwinding in an extern "C" function

Compiler

• Add --print host-tuple flag to print the host target tuple and affirm the "target tuple" terminology over "target triple"
• Declaring functions with a calling convention not supported on the current target now triggers a hard error
• Set up indirect access to external data for loongarch64-unknown-linux-{musl,ohos}
• Enable XRay instrumentation for LoongArch Linux targets
• Extend the unexpected_cfgs lint to also warn in external macros
• Stabilize WebAssembly multivalue, reference-types, and tail-call target features
• Added Tier 2 support for the wasm32v1-none target

Libraries

• Implement From<&mut {slice}> for Box/Rc/Arc<{slice}>
• Move <float>::copysign, <float>::abs, <float>::signum to core
• Add LowerExp and UpperExp implementations to NonZero
• Implement FromStr for CString and TryFrom<CString> for String
• std::os::darwin has been made public

Stabilized APIs

• Ipv6Addr::is_unique_local
• Ipv6Addr::is_unicast_link_local
• core::ptr::with_exposed_provenance
• core::ptr::with_exposed_provenance_mut
• <ptr>::addr
• <ptr>::expose_provenance
• <ptr>::with_addr
• <ptr>::map_addr
• <int>::isqrt
• <int>::checked_isqrt
• <uint>::isqrt
• NonZero::isqrt
• core::ptr::without_provenance
• core::ptr::without_provenance_mut
• core::ptr::dangling
• core::ptr::dangling_mut
• Pin::as_deref_mut

These APIs are now stable in const contexts

• AtomicBool::from_ptr
• AtomicPtr::from_ptr
• AtomicU8::from_ptr
• AtomicU16::from_ptr
• AtomicU32::from_ptr
• AtomicU64::from_ptr
• AtomicUsize::from_ptr
• AtomicI8::from_ptr
• AtomicI16::from_ptr
• AtomicI32::from_ptr
• AtomicI64::from_ptr
• AtomicIsize::from_ptr
• <ptr>::is_null
• <ptr>::as_ref
• <ptr>::as_mut
• Pin::new
• Pin::new_unchecked
• Pin::get_ref
• Pin::into_ref
• Pin::get_mut
• Pin::get_unchecked_mut
• Pin::static_ref
• Pin::static_mut

Cargo

• Stabilize MSRV-aware resolver config
• Stabilize resolver v3

Rustdoc

• rustdoc-search: improve type-driven search

Compatibility Notes

• Enable by default the LSX target feature for LoongArch Linux targets
• The unstable -Zprofile flag (“gcov-style” coverage instrumentation) has been removed. This does not affect the stable flags for coverage instrumentation (-Cinstrument-coverage) and profile-guided optimization (-Cprofile-generate, -Cprofile-use), which are unrelated and remain available.
• Support for the target named wasm32-wasi has been removed as the target is now named wasm32-wasip1. This completes the transition plan for this target following the introduction of wasm32-wasip1 in Rust 1.78. Compiler warnings on use of wasm32-wasi introduced in Rust 1.81 are now gone as well as the target is removed.
• The syntax &pin (mut|const) T is now parsed as a type which in theory could affect macro expansion results in some edge cases
• Legacy syntax for calling std::arch functions is no longer permitted to declare items or bodies (such as closures, inline consts, or async blocks).
• Declaring functions with a calling convention not supported on the current target now triggers a hard error
• The next-generation trait solver is now enabled for coherence, fixing multiple soundness issues