Rust 1.11: what's new, what was stabilized

• consts and statics may not have unsized types
• [The new follow-set rules that place restrictions on macro_rules!
• cfg attribute process has been refactored to fix various bugs.

Language

• Support nested cfg_attr attributes
• Allow statement-generating braced macro invocations at the end of blocks
• Macros can be expanded inside of trait definitions
• [#[macro_use] works properly when it is itself expanded from a macro](https://github.com/rust-lang/rust/pull/34032)

Stabilized APIs

• BinaryHeap::append
• BTreeMap::append
• BTreeMap::split_off
• BTreeSet::append
• BTreeSet::split_off
• f32::to_degrees (in libcore - previously stabilized in libstd)
• f32::to_radians (in libcore - previously stabilized in libstd)
• f64::to_degrees (in libcore - previously stabilized in libstd)
• f64::to_radians (in libcore - previously stabilized in libstd)
• Iterator::sum
• Iterator::product
• Cell::get_mut
• RefCell::get_mut

Libraries

• The thread_local! macro supports multiple definitions in a single invocation, and can apply attributes
• Cow implements Default
• Wrapping implements binary, octal, lower-hex and upper-hex Display formatting
• The range types implement Hash
• lookup_host ignores unknown address types
• assert_eq! accepts a custom error message, like assert! does
• The main thread is now called "main" instead of "<main>"

Cargo

• Disallow specifying features of transitive deps
• Add color support for Windows consoles
• [Fix harness = false on [lib] sections](https://github.com/rust-lang/cargo/pull/2795)
• Don't panic when links contains a '.'
• Build scripts can emit warnings, and -vv prints warnings for all crates.
• Ignore file locks on OS X NFS mounts
• Don't warn about package.metadata keys. This provides room for expansion by arbitrary tools.
• Add support for cdylib crate types
• Prevent publishing crates when files are dirty
• Don't fetch all crates on clean
• Propagate --color option to rustc
• Fix cargo doc --open on Windows
• Improve autocompletion
• Configure colors of stderr as well as stdout

Performance

• Caching projections speeds up type check dramatically for some workloads
• The default HashMap hasher is SipHash 1-3 instead of SipHash 2-4 This hasher is faster, but is believed to provide sufficient protection from collision attacks.
• Comparison of Ipv4Addr is 10x faster

Rustdoc

• Fix empty implementation section on some module pages
• Fix inlined renamed re-exports in import lists
• Fix search result layout for enum variants and struct fields
• Fix issues with source links to external crates
• Fix redirect pages for renamed re-exports

Tooling

• rustc is better at finding the MSVC toolchain
• When emitting debug info, rustc emits frame pointers for closures, shims and glue, as it does for all other functions
• rust-lldb warns about unsupported versions of LLDB
• Many more errors have been given error codes and extended explanations
• API documentation continues to be improved, with many new examples

Misc

• rustc no longer hangs when dependencies recursively re-export submodules
• rustc requires LLVM 3.7+
• The 'How Safe and Unsafe Interact' chapter of The Rustonomicon was rewritten
• rustc support 16-bit pointer sizes. No targets use this yet, but it works toward AVR support.

Compatibility Notes

• consts and statics may not have unsized types
• The new follow-set rules that place restrictions on macro_rules! in order to ensure syntax forward-compatibility have been enabled This was an amendment to RFC 550, and has been a warning since 1.10.
• cfg attribute process has been refactored to fix various bugs. This causes breakage in some corner cases.