1.65.0 #

• Released on: 3 November, 2022
• Branched from master on: 16 September, 2022

Language #

• Error on as casts of enums with #[non_exhaustive] variants
• Stabilize let else
• Stabilize generic associated types (GATs)
• Add lints let_underscore_drop and let_underscore_lock from Clippy
• Stabilize breaking from arbitrary labeled blocks (“label-break-value”)
• Uninitialized integers, floats, and raw pointers are now considered immediate UB. Usage of MaybeUninit is the correct way to work with uninitialized memory.
• Stabilize raw-dylib for Windows x86_64, aarch64, and thumbv7a
• Do not allow Drop impl on foreign ADTs

Compiler #

• Stabilize -Csplit-debuginfo on Linux
• Use niche-filling optimization even when multiple variants have data
• Associated type projections are now verified to be well-formed prior to resolving the underlying type
• Stringify non-shorthand visibility correctly
• Normalize struct field types when unsizing
• Update to LLVM 15
• Fix aarch64 call abi to correctly zeroext when needed
• debuginfo: Generalize C++-like encoding for enums
• Add special_module_name lint
• Add support for generating unique profraw files by default when using -C instrument-coverage
• Allow dynamic linking for iOS/tvOS targets

New targets:

• Add armv4t-none-eabi as a tier 3 target
• Add powerpc64-unknown-openbsd and riscv64-unknown-openbsd as tier 3 targets
  • Refer to Rust’s [platform support page][platform-support-doc] for more information on Rust’s tiered platform support.

Libraries #

• Don’t generate PartialEq::ne in derive(PartialEq)
• Windows RNG: Use BCRYPT_RNG_ALG_HANDLE by default
• Forbid mixing System with direct system allocator calls
• Document no support for writing to non-blocking stdio/stderr
• std::layout::Layout size must not overflow isize::MAX when rounded up to align This also changes the safety conditions on Layout::from_size_align_unchecked.

Stabilized APIs #

• std::backtrace::Backtrace
• Bound::as_ref
• std::io::read_to_string
• <*const T>::cast_mut
• <*mut T>::cast_const

These APIs are now stable in const contexts:

• <*const T>::offset_from
• <*mut T>::offset_from

Cargo #

• Apply GitHub fast path even for partial hashes
• Do not add home bin path to PATH if it’s already there
• Take priority into account within the pending queue. This slightly optimizes job scheduling by Cargo, with typically small improvements on larger crate graph builds.

Compatibility Notes #

• std::layout::Layout size must not overflow isize::MAX when rounded up to align. This also changes the safety conditions on Layout::from_size_align_unchecked.
• PollFn now only implements Unpin if the closure is Unpin. This is a possible breaking change if users were relying on the blanket unpin implementation. See discussion on the PR for details of why this change was made.
• Drop ExactSizeIterator impl from std::char::EscapeAscii This is a backwards-incompatible change to the standard library’s surface area, but is unlikely to affect real world usage.
• Do not consider a single repeated lifetime eligible for elision in the return type This behavior was unintentionally changed in 1.64.0, and this release reverts that change by making this an error again.
• Reenable disabled early syntax gates as future-incompatibility lints
• Update the minimum external LLVM to 13
• Don’t duplicate file descriptors into stdio fds
• Sunset RLS
• Deny usage of #![cfg_attr(..., crate_type = ...)] to set the crate type This strengthens the forward compatibility lint deprecated_cfg_attr_crate_type_name to deny.
• llvm-has-rust-patches allows setting the build system to treat the LLVM as having Rust-specific patches This option may need to be set for distributions that are building Rust with a patched LLVM via llvm-config, not the built-in LLVM.
• Combining three or more languages (e.g. Objective C, C++ and Rust) into one binary may hit linker limitations when using lld. For more information, see issue 102754.

Internal Changes #

These changes do not affect any public interfaces of Rust, but they represent significant improvements to the performance or internals of rustc and related tools.

• Add x.sh and x.ps1 shell scripts
• compiletest: use target cfg instead of hard-coded tables
• Use object instead of LLVM for reading bitcode from rlibs
• Enable MIR inlining for optimized compilations This provides a 3-10% improvement in compiletimes for real world crates. See perf results.