Rust 1.6: what's new, what was stabilized

• The compiler no longer makes use of the [RUST_PATH][1.6rp]
• [A number of bugs were fixed in the privacy checker][1.6p] that
• [Modules and unit/tuple structs may not share the same name][1.6ts].
• [Bugs in pattern matching unit structs were fixed][1.6us]. The tuple
• A bug was fixed that causes [rustc not to apply default type

Language

• The #![no_std] attribute causes a crate to not be linked to the standard library, but only the [core library][1.6co], as described in [RFC 1184]. The core library defines common types and traits but has no platform dependencies whatsoever, and is the basis for Rust software in environments that cannot support a full port of the standard library, such as operating systems. Most of the core library is now stable.

Libraries

• Stabilized APIs: [Read::read_exact], [ErrorKind::UnexpectedEof] (renamed from UnexpectedEOF), [fs::DirBuilder], [fs::DirBuilder::new], [fs::DirBuilder::recursive], [fs::DirBuilder::create], [os::unix::fs::DirBuilderExt], [os::unix::fs::DirBuilderExt::mode], [vec::Drain], [vec::Vec::drain], [string::Drain], [string::String::drain], [vec_deque::Drain], [vec_deque::VecDeque::drain], [collections::hash_map::Drain], [collections::hash_map::HashMap::drain], [collections::hash_set::Drain], [collections::hash_set::HashSet::drain], [collections::binary_heap::Drain], [collections::binary_heap::BinaryHeap::drain], [Vec::extend_from_slice] (renamed from push_all), [Mutex::get_mut], [Mutex::into_inner], [RwLock::get_mut], [RwLock::into_inner], [Iterator::min_by_key] (renamed from min_by), [Iterator::max_by_key] (renamed from max_by).
• The [core library][1.6co] is stable, as are most of its APIs.
• [The assert_eq! macro supports arguments that don't implement Sized][1.6ae], such as arrays. In this way it behaves more like assert!.
• Several timer functions that take duration in milliseconds [are deprecated in favor of those that take Duration][1.6ms]. These include Condvar::wait_timeout_ms, thread::sleep_ms, and thread::park_timeout_ms.
• The algorithm by which Vec reserves additional elements was [tweaked to not allocate excessive space][1.6a] while still growing exponentially.
• From conversions are [implemented from integers to floats][1.6f] in cases where the conversion is lossless. Thus they are not implemented for 32-bit ints to f32, nor for 64-bit ints to f32 or f64. They are also not implemented for isize and usize because the implementations would be platform-specific. From is also implemented from f32 to f64.
• From<&Path> and From<PathBuf> are implemented for Cow<Path>.
• From<T> is implemented for Box<T>, Rc<T> and Arc<T>.
• IntoIterator is implemented for &PathBuf and &Path.
• [BinaryHeap was refactored][1.6bh] for modest performance improvements.
• Sorting slices that are already sorted [is 50% faster in some cases][1.6s].

Cargo

• Cargo will look in $CARGO_HOME/bin for subcommands [by default][1.6c].
• Cargo build scripts can specify their dependencies by emitting the [rerun-if-changed][1.6rr] key.
• crates.io will reject publication of crates with dependencies that have a wildcard version constraint. Crates with wildcard dependencies were seen to cause a variety of problems, as described in [RFC 1241]. Since 1.5 publication of such crates has emitted a warning.
• cargo clean [accepts a --release flag][1.6cc] to clean the release folder. A variety of artifacts that Cargo failed to clean are now correctly deleted.

Misc

• The unreachable_code lint [warns when a function call's argument diverges][1.6dv].
• The parser indicates [failures that may be caused by confusingly-similar Unicode characters][1.6uc]
• Certain macro errors [are reported at definition time][1.6m], not expansion.

Compatibility Notes

• The compiler no longer makes use of the RUST_PATH environment variable when locating crates. This was a pre-cargo feature for integrating with the package manager that was accidentally never removed.
• A number of bugs were fixed in the privacy checker that could cause previously-accepted code to break.
• Modules and unit/tuple structs may not share the same name.
• Bugs in pattern matching unit structs were fixed. The tuple struct pattern syntax (Foo(..)) can no longer be used to match unit structs. This is a warning now, but will become an error in future releases. Patterns that share the same name as a const are now an error.
• A bug was fixed that causes rustc not to apply default type parameters when resolving certain method implementations of traits defined in other crates.