Rust 1.1: what's new, what was stabilized

Highlights

• The [std::fs module has been expanded][fs] to expand the set of functionality exposed:
• DirEntry now supports optimizations like file_type and metadata which don't incur a syscall on some platforms.
• A symlink_metadata function has been added.
• The fs::Metadata structure now lowers to its OS counterpart, providing access to all underlying information.
• The compiler now contains extended explanations of many errors. When an error with an explanation occurs the compiler suggests using the --explain flag to read the explanation. Error explanations are also [available online][err-index].
• Thanks to multiple [improvements][sk] to [type checking][pre], as well as other work, the time to bootstrap the compiler decreased by 32%.

Libraries

• The [str::split_whitespace] method splits a string on unicode whitespace boundaries.
• On both Windows and Unix, new extension traits provide conversion of I/O types to and from the underlying system handles. On Unix, these traits are [FromRawFd] and [AsRawFd], on Windows FromRawHandle and AsRawHandle. These are implemented for File, TcpStream, TcpListener, and UpdSocket. Further implementations for std::process will be stabilized later.
• On Unix, [std::os::unix::symlink] creates symlinks. On Windows, symlinks can be created with std::os::windows::symlink_dir and std::os::windows::symlink_file.
• The mpsc::Receiver type can now be converted into an iterator with into_iter on the [IntoIterator] trait.
• Ipv4Addr can be created from u32 with the From<u32> implementation of the [From] trait.
• The Debug implementation for RangeFull [creates output that is more consistent with other implementations][rf].
• [Debug is implemented for File][file].
• The Default implementation for Arc [no longer requires Sync + Send][arc].
• [The Iterator methods count, nth, and last have been overridden for slices to have *O*(1) performance instead of *O*(*n*)][si].
• Incorrect handling of paths on Windows has been improved in both the compiler and the standard library.
• [AtomicPtr gained a Default implementation][ap].
• In accordance with Rust's policy on arithmetic overflow abs now [panics on overflow when debug assertions are enabled][abs].
• The [Cloned] iterator, which was accidentally left unstable for 1.0 [has been stabilized][c].
• The [Incoming] iterator, which iterates over incoming TCP connections, and which was accidentally unnamable in 1.0, [is now properly exported][inc].
• [BinaryHeap] no longer corrupts itself [when functions called by sift_up or sift_down panic][bh].
• The [split_off] method of LinkedList [no longer corrupts the list in certain scenarios][ll].

Misc

• Type checking performance has improved notably with multiple improvements.
• The compiler suggests code changes for more errors.
• rustc and it's build system have experimental support for building toolchains against MUSL instead of glibc on Linux.
• The compiler defines the target_env cfg value, which is used for distinguishing toolchains that are otherwise for the same platform. Presently this is set to gnu for common GNU Linux targets and for MinGW targets, and musl for MUSL Linux targets.
• The cargo rustc command invokes a build with custom flags to rustc.
• Android executables are always position independent.
• The drop_with_repr_extern lint warns about mixing repr(C) with Drop.