Rust 1.87: what's new, what was stabilized

• [Rust now raises an error for macro invocations inside the #![crate_name] attribute](https://github.com/rust-lang/rust/pull/127581)
• Unstable fields are now always considered to be inhabited
• Macro arguments of unary operators followed by open beginning ranges may now be matched differently
• Make Debug impl of raw pointers print metadata if present
• Warn against function pointers using unsupported ABI strings in dependencies
• Associated types on dyn types are no longer deduplicated
• [Forbid attributes on .. inside of struct patterns (let Struct { #[attribute] .. }) =](https://github.com/rust-lang/rust/pull/136490)
• Make ptr_cast_add_auto_to_object lint into hard error
• Many std::arch intrinsics are now safe to call in some contexts, there may now be new unused_unsafe warnings in existing codebases.
• Limit width and precision formatting options to 16 bits on all targets
• Turn order dependent trait objects future incompat warning into a hard error
• [Denote ControlFlow as #[must_use]](https://github.com/rust-lang/rust/pull/137449)
• Windows: The standard library no longer links advapi32, except on win7. Code such as C libraries that were relying on this assumption may need to explicitly link advapi32.
• Proc macros can no longer observe expanded cfg(true) attributes.
• Start changing the internal representation of pasted tokens. Certain invalid declarative macros that were previously accepted in obscure circumstances are now correctly rejected by the compiler. Use of a tt fragment specifier can often fix these macros.
• Don't allow flattened format_args in const.

Language

• Stabilize asm_goto feature
• Allow parsing open beginning ranges (..EXPR) after unary operators !, -, and *.
• Don't require method impls for methods with Self: Sized bounds in impls for unsized types
• Stabilize feature(precise_capturing_in_traits) allowing use<...> bounds on return position impl Trait in traits

<a id="1.87.0-Compiler"></a>

Compiler

• x86: make SSE2 required for i686 targets and use it to pass SIMD types

<a id="1.87.0-Platform-Support"></a>

Platform Support

• Remove i586-pc-windows-msvc target

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

<a id="1.87.0-Libraries"></a>

Libraries

• Stabilize the anonymous pipe API
• Add support for unbounded left/right shift operations
• Print pointer metadata in Debug impl of raw pointers
• Vec::with_capacity guarantees it allocates with the amount requested, even if Vec::capacity returns a different number.
• Most std::arch intrinsics which don't take pointer arguments can now be called from safe code if the caller has the appropriate target features already enabled (https://github.com/rust-lang/stdarch/pull/1714, https://github.com/rust-lang/stdarch/pull/1716, https://github.com/rust-lang/stdarch/pull/1717)
• Undeprecate env::home_dir
• [Denote ControlFlow as #[must_use]](https://github.com/rust-lang/rust/pull/137449)
• Macros such as assert_eq! and vec! now support const {...} expressions

<a id="1.87.0-Stabilized-APIs"></a>

Stabilized APIs

• Vec::extract_if
• vec::ExtractIf
• LinkedList::extract_if
• linked_list::ExtractIf
• [<[T]>::split_off](https://doc.rust-lang.org/stable/std/primitive.slice.html#method.split_off)
• [<[T]>::split_off_mut](https://doc.rust-lang.org/stable/std/primitive.slice.html#method.split_off_mut)
• [<[T]>::split_off_first](https://doc.rust-lang.org/stable/std/primitive.slice.html#method.split_off_first)
• [<[T]>::split_off_first_mut](https://doc.rust-lang.org/stable/std/primitive.slice.html#method.split_off_first_mut)
• [<[T]>::split_off_last](https://doc.rust-lang.org/stable/std/primitive.slice.html#method.split_off_last)
• [<[T]>::split_off_last_mut](https://doc.rust-lang.org/stable/std/primitive.slice.html#method.split_off_last_mut)
• String::extend_from_within
• os_str::Display
• OsString::display
• OsStr::display
• io::pipe
• io::PipeReader
• io::PipeWriter
• impl From<PipeReader> for OwnedHandle
• impl From<PipeWriter> for OwnedHandle
• impl From<PipeReader> for Stdio
• impl From<PipeWriter> for Stdio
• impl From<PipeReader> for OwnedFd
• impl From<PipeWriter> for OwnedFd
• Box<MaybeUninit<T>>::write
• impl TryFrom<Vec<u8>> for String
• <*const T>::offset_from_unsigned
• <*const T>::byte_offset_from_unsigned
• <*mut T>::offset_from_unsigned
• <*mut T>::byte_offset_from_unsigned
• NonNull::offset_from_unsigned
• NonNull::byte_offset_from_unsigned
• <uN>::cast_signed
• NonZero::<uN>::cast_signed.
• <iN>::cast_unsigned.
• NonZero::<iN>::cast_unsigned.
• <uN>::is_multiple_of
• <uN>::unbounded_shl
• <uN>::unbounded_shr
• <iN>::unbounded_shl
• <iN>::unbounded_shr
• <iN>::midpoint
• <str>::from_utf8
• <str>::from_utf8_mut
• <str>::from_utf8_unchecked
• <str>::from_utf8_unchecked_mut

These previously stable APIs are now stable in const contexts:

• core::str::from_utf8_mut
• [<[T]>::copy_from_slice](https://doc.rust-lang.org/stable/std/primitive.slice.html#method.copy_from_slice)
• SocketAddr::set_ip
• SocketAddr::set_port,
• SocketAddrV4::set_ip
• SocketAddrV4::set_port,
• SocketAddrV6::set_ip
• SocketAddrV6::set_port
• SocketAddrV6::set_flowinfo
• SocketAddrV6::set_scope_id
• char::is_digit
• char::is_whitespace
• [<[[T; N]]>::as_flattened](https://doc.rust-lang.org/stable/std/primitive.slice.html#method.as_flattened)
• [<[[T; N]]>::as_flattened_mut](https://doc.rust-lang.org/stable/std/primitive.slice.html#method.as_flattened_mut)
• String::into_bytes
• String::as_str
• String::capacity
• String::as_bytes
• String::len
• String::is_empty
• String::as_mut_str
• String::as_mut_vec
• Vec::as_ptr
• Vec::as_slice
• Vec::capacity
• Vec::len
• Vec::is_empty
• Vec::as_mut_slice
• Vec::as_mut_ptr

<a id="1.87.0-Cargo"></a>

Cargo

• Add terminal integration via ANSI OSC 9;4 sequences
• chore: bump openssl to v3
• feat(package): add --exclude-lockfile flag

<a id="1.87.0-Compatibility-Notes"></a>

Compatibility Notes

• [Rust now raises an error for macro invocations inside the #![crate_name] attribute](https://github.com/rust-lang/rust/pull/127581)
• Unstable fields are now always considered to be inhabited
• Macro arguments of unary operators followed by open beginning ranges may now be matched differently
• Make Debug impl of raw pointers print metadata if present
• Warn against function pointers using unsupported ABI strings in dependencies
• Associated types on dyn types are no longer deduplicated
• [Forbid attributes on .. inside of struct patterns (let Struct { #[attribute] .. }) =](https://github.com/rust-lang/rust/pull/136490)
• Make ptr_cast_add_auto_to_object lint into hard error
• Many std::arch intrinsics are now safe to call in some contexts, there may now be new unused_unsafe warnings in existing codebases.
• Limit width and precision formatting options to 16 bits on all targets
• Turn order dependent trait objects future incompat warning into a hard error
• [Denote ControlFlow as #[must_use]](https://github.com/rust-lang/rust/pull/137449)
• Windows: The standard library no longer links advapi32, except on win7. Code such as C libraries that were relying on this assumption may need to explicitly link advapi32.
• Proc macros can no longer observe expanded cfg(true) attributes.
• Start changing the internal representation of pasted tokens. Certain invalid declarative macros that were previously accepted in obscure circumstances are now correctly rejected by the compiler. Use of a tt fragment specifier can often fix these macros.
• Don't allow flattened format_args in const.

<a id="1.87.0-Internal-Changes"></a>

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.

• Update to LLVM 20