RUST-1.96.0 release notes and known issues

Summary

Language Allow passing expr metavariable to cfg Always coerce never types in tuple expressions Avoid incorrect inference guidance of function arguments in rare cases Support s390x vector registers in inline assembly Allow using constants of type ManuallyDrop as patterns (fixing a regression introduced in 1.94.0) Compiler Enable link relaxation feature for LoongArch Linux targets Update riscv64gc-unknown-fuchsia baseline to RVA22 + vector Libraries Support iterating over ranges of NonZero integers refactor 'valid for read/write' definition: exclude null; add that as an exception on individual methods instead Fix SGX delayed host lookup via ToSocketAddr Stabilized APIs assert_matches! debug_assert_matches! From<T> for AssertUnwindSafe<T> From<T> for LazyCell<T, F> From<T> for LazyLock<T, F> core::range::RangeToInclusive core::range::RangeToInclusiveIter core::range::RangeFrom core::range::RangeFromIter core::range::Range core::range::RangeIter Cargo Allow a dependency to specify both a git repository and an alternate registry. Just like with crates.io, the git repository will be used locally, but the registry version will be used when published. Added target.'cfg(..)'.rustdocflags support in configuration. Fixed CVE-2026-5222 and CVE-2026-5223 . Rustdoc Deprecation notes are now rendered like any other documentation . Previously they used the css white-space: pre-wrap; property and stripped any <p> elements from the rendered html, however this caused issues and unintuitive behavior. The new behavior should be more predictable, however some multi-line deprecation notes will now be rendered as as single lines. If this is undesirable, you can use the standard markdown method of forcing a linebreak, which is two spaces followed by a newline ( "\n" ). Don't emit rustdoc missing_doc_code_examples lint on impl items Separate methods and associated functions in sidebar Compatibility Notes Fix layout of #[repr(Int)] enums in some edge cases involving fields of uninhabited zero-sized types Prevent unsize-coercing into Pin<Foo> where Foo doesn't implement Deref . Some such coercions were previously allowed, but produce a type with no useful public API. rustc: Stop passing --allow-undefined on wasm targets Gate the accidentally stabilized #![reexport_test_harness_main] attribute Error on return-position-impl-trait-in-traits whose types are too private Report the uninhabited_static lint in dependencies and make it deny-by-default Distributed builds now contain non-split debuginfo for windows-gnu This appears to improve the quality of backtraces. This change has no effect on the defaults for the output of rustc/cargo on these targets. Check const generic arguments are correctly typed in more positions Remove -Csoft-float Importing structs with ::{self [as name]} , e.g., struct S {}; use S::{self as Other}; , is now no longer permitted because {self} imports require a module parent. For export_name , link_name , and link_section attributes, if multiple of the same attribute is present, the first one now takes precedence. Update the minimum external LLVM to 21 On avr targets, C's double type is 32-bit by default, so change c_double to f32 on avr targets to match . This is a breaking change, but necessary to make c_double match C's double. BTreeMap::append() was optimized, which may now cause panics for types with incorrect Ord impls 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. JSON targets: aarch64 softfloat targets now have to have rustc_abi set to "softfloat" target specs: stricter checks for LLVM ABI values, and correlate that with cfg(target_abi)

Improvements and security content

• Language Allow passing expr metavariable to cfg Always coerce never types in tuple expressions Avoid incorrect inference guidance of function arguments in rare cases Support s390x vector registers in inline assembly Allow using constants of type ManuallyDrop as patterns (fixing a regression introduced in 1.94.0) Compiler Enable link relaxation feature for LoongArch Linux targets Update riscv64gc-unknown-fuchsia baseline to RVA22 + vector Libraries Support iterating over ranges of NonZero integers refactor 'valid for read/write' definition: exclude null; add that as an exception on individual methods instead Fix SGX delayed host lookup via ToSocketAddr Stabilized APIs assert_matches! debug_assert_matches! From<T> for AssertUnwindSafe<T> From<T> for LazyCell<T, F> From<T> for LazyLock<T, F> core::range::RangeToInclusive core::range::RangeToInclusiveIter core::range::RangeFrom core::range::RangeFromIter core::range::Range core::range::RangeIter Cargo Allow a dependency to specify both a git repository and an alternate registry. Just like with crates.io, the git repository will be used locally, but the registry version will be used when published. Added target.'cfg(..)'.rustdocflags support in configuration. Fixed CVE-2026-5222 and CVE-2026-5223 . Rustdoc Deprecation notes are now rendered like any other documentation . Previously they used the css white-space: pre-wrap; property and stripped any <p> elements from the rendered html, however this caused issues and unintuitive behavior. The new behavior should be more predictable, however some multi-line deprecation notes will now be rendered as as single lines. If this is undesirable, you can use the standard markdown method of forcing a linebreak, which is two spaces followed by a newline ( "\n" ). Don't emit rustdoc missing_doc_code_examples lint on impl items Separate methods and associated functions in sidebar Compatibility Notes Fix layout of #[repr(Int)] enums in some edge cases involving fields of uninhabited zero-sized types Prevent unsize-coercing into Pin<Foo> where Foo doesn't implement Deref . Some such coercions were previously allowed, but produce a type with no useful public API. rustc: Stop passing --allow-undefined on wasm targets Gate the accidentally stabilized #![reexport_test_harness_main] attribute Error on return-position-impl-trait-in-traits whose types are too private Report the uninhabited_static lint in dependencies and make it deny-by-default Distributed builds now contain non-split debuginfo for windows-gnu This appears to improve the quality of backtraces. This change has no effect on the defaults for the output of rustc/cargo on these targets. Check const generic arguments are correctly typed in more positions Remove -Csoft-float Importing structs with ::{self [as name]} , e.g., struct S {}; use S::{self as Other}; , is now no longer permitted because {self} imports require a module parent. For export_name , link_name , and link_section attributes, if multiple of the same attribute is present, the first one now takes precedence. Update the minimum external LLVM to 21 On avr targets, C's double type is 32-bit by default, so change c_double to f32 on avr targets to match . This is a breaking change, but necessary to make c_double match C's double. BTreeMap::append() was optimized, which may now cause panics for types with incorrect Ord impls 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. JSON targets: aarch64 softfloat targets now have to have rustc_abi set to "softfloat" target specs: stricter checks for LLVM ABI values, and correlate that with cfg(target_abi)

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