Rust 1.4: what's new, what was stabilized

Highlights

• Windows builds targeting the 64-bit MSVC ABI and linker (instead of GNU) are now supported and recommended for use.

Breaking Changes

• [Several changes have been made to fix type soundness and improve the behavior of associated types][sound]. See [RFC 1214]. Although we have mostly introduced these changes as warnings this release, to become errors next release, there are still some scenarios that will see immediate breakage.
• [The str::lines and BufRead::lines iterators treat \r\n as line breaks in addition to \n][crlf].
• [Loans of 'static lifetime extend to the end of a function][stat].
• [str::parse no longer introduces avoidable rounding error when parsing floating point numbers. Together with earlier changes to float formatting/output, "round trips" like f.to_string().parse() now preserve the value of f exactly. Additionally, leading plus signs are now accepted][fp3].

Language

• use statements that import multiple items [can now rename them][i], as in use foo::{bar as kitten, baz as puppy}.
• [Binops work correctly on fat pointers][binfat].
• pub extern crate, which does not behave as expected, [issues a warning][pec] until a better solution is found.

Libraries

• [Many APIs were stabilized][stab]: <Box<str>>::into_string, [Arc::downgrade], [Arc::get_mut], [Arc::make_mut], [Arc::try_unwrap], [Box::from_raw], [Box::into_raw], [CStr::to_str], [CStr::to_string_lossy], [CString::from_raw], [CString::into_raw], [IntoRawFd::into_raw_fd], [IntoRawFd], IntoRawHandle::into_raw_handle, IntoRawHandle, IntoRawSocket::into_raw_socket, IntoRawSocket, [Rc::downgrade], [Rc::get_mut], [Rc::make_mut], [Rc::try_unwrap], [Result::expect], [String::into_boxed_str], [TcpStream::read_timeout], [TcpStream::set_read_timeout], [TcpStream::set_write_timeout], [TcpStream::write_timeout], [UdpSocket::read_timeout], [UdpSocket::set_read_timeout], [UdpSocket::set_write_timeout], [UdpSocket::write_timeout], Vec::append, Vec::split_off, [VecDeque::append], [VecDeque::retain], [VecDeque::split_off], [rc::Weak::upgrade], [rc::Weak], [slice::Iter::as_slice], [slice::IterMut::into_slice], [str::CharIndices::as_str], [str::Chars::as_str], [str::split_at_mut], [str::split_at], [sync::Weak::upgrade], [sync::Weak], [thread::park_timeout], [thread::sleep].
• [Some APIs were deprecated][dep]: BTreeMap::with_b, BTreeSet::with_b, Option::as_mut_slice, Option::as_slice, Result::as_mut_slice, Result::as_slice, f32::from_str_radix, f64::from_str_radix.
• [Reverse-searching strings is faster with the 'two-way' algorithm][s].
• [std::io::copy allows ?Sized arguments][cc].
• The Windows, Chunks, and ChunksMut iterators over slices all [override count, nth and last with an *O*(1) implementation][it].
• [Default is implemented for arrays up to [T; 32]][d].
• [IntoRawFd has been added to the Unix-specific prelude, IntoRawSocket and IntoRawHandle to the Windows-specific prelude][pr].
• [Extend<String> and FromIterator<String are both implemented for String][es].
• [IntoIterator is implemented for references to Option and Result][into2].
• [HashMap and HashSet implement Extend<&T> where T: Copy][ext] as part of [RFC 839]. This will cause type inference breakage in rare situations.
• [BinaryHeap implements Debug][bh2].
• [Borrow and BorrowMut are implemented for fixed-size arrays][bm].
• [extern fns with the "Rust" and "C" ABIs implement common traits including Eq, Ord, Debug, Hash][fp].
• [String comparison is faster][faststr].
• &mut T where T: std::fmt::Write [also implements std::fmt::Write][mutw].
• [A stable regression in VecDeque::push_back and other capacity-altering methods that caused panics for zero-sized types was fixed][vd].
• [Function pointers implement traits for up to 12 parameters][fp2].

Miscellaneous

• The compiler no longer uses the 'morestack' feature to prevent stack overflow. Instead it uses guard pages and stack probes (though stack probes are not yet implemented on any platform but Windows).
• The compiler matches traits faster when projections are involved.
• The 'improper_ctypes' lint no longer warns about use of isize and usize.
• Cargo now displays useful information about what its doing during cargo update.