Rust 1.62.0

Language

• Stabilize #[derive(Default)] on enums with a #[default] variant
• Teach flow sensitive checks that visibly uninhabited call expressions never return
• Fix constants not getting dropped if part of a diverging expression
• Support unit struct/enum variant in destructuring assignment
• Remove mutable_borrow_reservation_conflict lint and allow the code pattern
• const functions may now specify extern "C" or extern "Rust"

Compiler

• linker: Stop using whole-archive on dependencies of dylibs
• Make unaligned_references lint deny-by-default This lint is also a future compatibility lint, and is expected to eventually become a hard error.
• Only add codegen backend to dep info if -Zbinary-dep-depinfo is used
• Reject #[thread_local] attribute on non-static items
• Add tier 3 aarch64-pc-windows-gnullvm and x86_64-pc-windows-gnullvm targets*
• Implement a lint to warn about unused macro rules
• Promote x86_64-unknown-none target to Tier 2*

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

Libraries

• Windows: Use a pipe relay for chaining pipes
• Replace Linux Mutex and Condvar with futex based ones.
• Replace RwLock by a futex based one on Linux
• std: directly use pthread in UNIX parker implementation

Stabilized APIs

• bool::then_some
• f32::total_cmp
• f64::total_cmp
• Stdin::lines
• windows::CommandExt::raw_arg
• impl<T: Default> Default for AssertUnwindSafe<T>
• From<Rc<str>> for Rc<[u8]>
• From<Arc<str>> for Arc<[u8]>
• FusedIterator for EncodeWide
• RDM intrinsics on aarch64

Clippy

• Create clippy lint against unexpectedly late drop for temporaries in match scrutinee expressions

Cargo

• Added the cargo add command for adding dependencies to Cargo.toml from the command-line. docs
• Package ID specs now support name@version syntax in addition to the previous name:version to align with the behavior in cargo add and other tools. cargo install and cargo yank also now support this syntax so the version does not need to passed as a separate flag.
• The git and registry directories in Cargo's home directory (usually ~/.cargo) are now marked as cache directories so that they are not included in backups or content indexing (on Windows).
• Added automatic @ argfile support, which will use "response files" if the command-line to rustc exceeds the operating system's limit.

Compatibility Notes

• cargo test now passes --target to rustdoc if the specified target is the same as the host target. #10594
• rustdoc: doctests are now run on unexported macro_rules! macros, matching other private items
• rustdoc: Remove .woff font files
• Enforce Copy bounds for repeat elements while considering lifetimes
• Windows: Fix potential unsoundness by aborting if File reads or writes cannot complete synchronously.

Internal Changes

• Unify ReentrantMutex implementations across all platforms

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