Rust 1.23.0

Language

• Arbitrary auto traits are now permitted in trait objects.
• rustc now uses subtyping on the left hand side of binary operations. Which should fix some confusing errors in some operations.

Compiler

• Enabled TrapUnreachable in LLVM which should mitigate the impact of undefined behavior.
• rustc now suggests renaming import if names clash.
• Display errors/warnings correctly when there are zero-width or wide characters.
• rustc now avoids unnecessary copies of arguments that are simple bindings This should improve memory usage on average by 5-10%.
• Updated musl used to build musl rustc to 1.1.17

Libraries

• Allow a trailing comma in assert_eq/ne macro
• Implement Hash for raw pointers to unsized types
• impl From<*mut T> for AtomicPtr<T>
• impl From<usize/isize> for AtomicUsize/AtomicIsize.
• Removed the T: Sync requirement for RwLock<T>: Send
• Removed T: Sized requirement for {<*const T>, <*mut T>}::as_ref and <*mut T>::as_mut
• Optimized Thread::{park, unpark} implementation
• Improved SliceExt::binary_search performance.
• impl FromIterator<()> for ()
• Copied AsciiExt trait methods to primitive types. Use of AsciiExt is now deprecated.

Stabilized APIs

Cargo

• Cargo now supports uninstallation of multiple packages eg. cargo uninstall foo bar uninstalls foo and bar.
• Added unit test checking to cargo check
• Cargo now lets you install a specific version using cargo install --version

Misc

• Releases now ship with the Cargo book documentation.
• rustdoc now prints rendering warnings on every run.

Compatibility Notes

• Changes have been made to type equality to make it more correct, in rare cases this could break some code. Tracking issue for further information
• char::escape_debug now uses Unicode 10 over 9.
• Upgraded Android SDK to 27, and NDK to r15c. This drops support for Android 9, the minimum supported version is Android 14.
• Bumped the minimum LLVM to 3.9