Rust 1.98.0

Language

• Allow shortening lifetime of &mut when unsize-coercing, even in an invariant position. For example, you can now coerce a Cell<&'long mut i32> to a Cell<&'short mut dyn Send>. Such shortenings were already previously allowed when coercing a &mut to a &, or coercing a & to a &.
• Add deny-by-default invalid_runtime_symbol_definitions lint and warn-by-default suspicious_runtime_symbol_definitions lint
  • The lints currently specifically targets core runtime symbols like memcmp, memset, strlen, ... and is planned to be expanded in the next few releases.
• Add warn-by-default c_void_returns lint to check core::ffi::c_void as a return type

Platform Support

• Add powerpc64-unknown-linux-gnuelfv2 as Tier 3
• Add aarch64-unknown-linux-pauthtest as Tier 3 target
• Promote thumbv7a-none-eabi to Tier 2
• Promote thumbv7a-none-eabihf to Tier 2
• Promote thumbv7r-none-eabi to Tier 2
• Promote thumbv7r-none-eabihf to Tier 2
• Promote thumbv8r-none-eabihf to Tier 2

Refer to Rust's platform support page for more information on Rust's tiered platform support.

Libraries

• Change Location<'_> lifetime to 'static in Panic[Hook]Info
• Document panic in RangeInclusive::from(legacy::RangeInclusive)
• Document that ManuallyDrop's Box interaction has been fixed
• Stabilize LoongArch CRC Intrinsics
• The derive macro is available at {core,std}::derive. This was previously unintentionally stabilized in 1.96, but is now explicitly accepted as a stabilized API.
  • Please note that the MSRV for {core,std}::derive will be 1.96, and not 1.98.

Stabilized APIs

• str::substr_range
• [T]::subslice_range
• core::fmt::NumBuffer
• <{integer}>::format_into
• Send/Sync for std::process::CommandArgs
• {fN}::algebraic_add
• {fN}::algebraic_sub
• {fN}::algebraic_mul
• {fN}::algebraic_div
• {fN}::algebraic_rem
• NonZero<{integer}>::from_str_radix
• String::from_utf16le
• String::from_utf16le_lossy
• String::from_utf16be
• String::from_utf16be_lossy
• [T]::strip_circumfix
• str::strip_circumfix
• Atomic<T>::from_mut
• Atomic<T>::get_mut_slice
• Atomic<T>::from_mut_slice
• std::range::legacy

Compatibility Notes

• If fully elided, lifetime bounds of trait object types may now resolve differently or even get rejected in very specific niche scenarios
• Error in more cases of ambiguous imports
• Switch the destructors implementation for thread locals on Windows to use Fiber Local Storage (FLS)
• Convert some cases of the ambiguous_glob_imports lint into a hard error
• Where-bounds of the form Type = Type and Type == Type are no longer syntactically allowed
• Ensure Send/Sync is not implemented for std::env::Vars{,Os}
• Fix that in some attributes, arguments were not properly rejected
• repr(transparent) is now more strict about which fields have "trivial" layout and hence can be ignored: repr(C) types, types with private fields, and #[non_exhaustive] types are no longer considered "trivial"
• Correctly check whether types have equal size in transmute() when some repr attributes are involved.
• More characters are escaped when printing strings and chars
• Implement fast path for derive(PartialOrd) when deriving Ord This can break crates in practice where a type's PartialOrd and Ord impls were inconsistent with each other.
• Add temporary scope to assert_eq and assert_ne
• Closed a hole in the pattern matching structural equality check, preventing cases where a match of a constant would be allowed, despite disagreeing with a manually written PartialEq implementation, when a derive(PartialEq) implementation for that type also exists.
• On Emscripten the WASM exception handling ABI is now unconditionally used The -Zemscripten-wasm-eh=false flag to switch back to JS exceptions has been removed.
• The UNSAFE_CODE lint is now consistently emitted for all unsafe attributes
• Solaris: remove File::lock implementation, it has the wrong semantics (return "unsupported" instead)
• Windows-gnu targets now specify baseline tools versions
• rustfmt now discovers module files that are defined in cfg_select! This may cause more code to be formatted which was previously ignored.