Rust 1.63.0

Language

• Remove migrate borrowck mode for pre-NLL errors.
• Modify MIR building to drop repeat expressions with length zero.
• Remove label/lifetime shadowing warnings.
• Allow explicit generic arguments in the presence of impl Trait args.
• Make cenum_impl_drop_cast warnings deny-by-default.
• Prevent unwinding when -C panic=abort is used regardless of declared ABI.
• lub: don't bail out due to empty binders.

Compiler

• Stabilize the bundle native library modifier, also removing the deprecated static-nobundle linking kind.
• Add Apple WatchOS compile targets*.
• Add a Windows application manifest to rustc-main.

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

Libraries

• Implement Copy, Clone, PartialEq and Eq for core::fmt::Alignment.
• Extend ptr::null and null_mut to all thin (including extern) types.
• impl Read and Write for VecDeque<u8>.
• STD support for the Nintendo 3DS.
• Use rounding in float to Duration conversion methods.
• Make write/print macros eagerly drop temporaries.
• Implement internal traits that enable [OsStr]::join.
• Implement Hash for core::alloc::Layout.
• Add capacity documentation for OsString.
• Put a bound on collection misbehavior.
• Make std::mem::needs_drop accept ?Sized.
• impl Termination for Infallible and then make the Result impls of Termination more generic.
• Document Rust's stance on /proc/self/mem.

Stabilized APIs

• array::from_fn
• Box::into_pin
• BinaryHeap::try_reserve
• BinaryHeap::try_reserve_exact
• OsString::try_reserve
• OsString::try_reserve_exact
• PathBuf::try_reserve
• PathBuf::try_reserve_exact
• Path::try_exists
• Ref::filter_map
• RefMut::filter_map
• NonNull::<[T]>::len
• ToOwned::clone_into
• Ipv6Addr::to_ipv4_mapped
• unix::io::AsFd
• unix::io::BorrowedFd<'fd>
• unix::io::OwnedFd
• windows::io::AsHandle
• windows::io::BorrowedHandle<'handle>
• windows::io::OwnedHandle
• windows::io::HandleOrInvalid
• windows::io::HandleOrNull
• windows::io::InvalidHandleError
• windows::io::NullHandleError
• windows::io::AsSocket
• windows::io::BorrowedSocket<'handle>
• windows::io::OwnedSocket
• thread::scope
• thread::Scope
• thread::ScopedJoinHandle

These APIs are now usable in const contexts:

• array::from_ref
• slice::from_ref
• intrinsics::copy
• intrinsics::copy_nonoverlapping
• <*const T>::copy_to
• <*const T>::copy_to_nonoverlapping
• <*mut T>::copy_to
• <*mut T>::copy_to_nonoverlapping
• <*mut T>::copy_from
• <*mut T>::copy_from_nonoverlapping
• str::from_utf8
• Utf8Error::error_len
• Utf8Error::valid_up_to
• Condvar::new
• Mutex::new
• RwLock::new

Cargo

• Stabilize the --config path command-line argument.
• Expose rust-version in the environment as CARGO_PKG_RUST_VERSION.

Compatibility Notes

• #[link] attributes are now checked more strictly, which may introduce errors for invalid attribute arguments that were previously ignored.
• Rounding is now used when converting a float to a Duration. The converted duration can differ slightly from what it was.

Internal Changes

These changes provide no direct user facing benefits, but represent significant improvements to the internals and overall performance of rustc and related tools.

• Prepare Rust for LLVM opaque pointers.