- Added several language syntax features (cfg on if, self in all fn contexts, type Foo: Ord, macro fragment interpolation, associated constants on primitives) and stabilized new const APIs.
- Improved compiler behavior: multiple lint flag ordering, prefer system MinGW libs on Windows, buffered JSON output, increased optimization level and numerous internal performance boosts.
- Extended standard library: TryFrom implementations for Arc/Box/Rc arrays, const u8::is_ascii, String AsMut<str>, primitive module, relaxed HashMap/HashSet bounds, and new numeric constants.