Version 1.12.1 (2016-10-20)

Regression Fixes

Version 1.12.0 (2016-09-29)

Highlights

rustc translates code to LLVM IR via its own "middle" IR (MIR). This translation pass is far simpler than the previous AST->LLVM pass, and creates opportunities to perform new optimizations directly on the MIR. It was previously described on the Rust blog.
rustc presents a new, more readable error format, along with machine-readable JSON error output for use by IDEs. Most common editors supporting Rust have been updated to work with it. It was previously described on the Rust blog.

Compiler

rustc translates code to LLVM IR via its own "middle" IR (MIR). This translation pass is far simpler than the previous AST->LLVM pass, and creates opportunities to perform new optimizations directly on the MIR. It was previously described on the Rust blog.
Print the Rust target name, not the LLVM target name, with --print target-list
The computation of TypeId is correct in some cases where it was previously producing inconsistent results
The mips-unknown-linux-gnu target uses hardware floating point by default
The rustc arguments, --print target-cpus, --print target-features, --print relocation-models, and --print code-models print the available options to the -C target-cpu, -C target-feature, -C relocation-model and -C code-model code generation arguments
rustc supports three new MUSL targets on ARM: arm-unknown-linux-musleabi, arm-unknown-linux-musleabihf, and armv7-unknown-linux-musleabihf. These targets produce statically-linked binaries. There are no binary release builds yet though.

Diagnostics

rustc presents a new, more readable error format, along with machine-readable JSON error output for use by IDEs. Most common editors supporting Rust have been updated to work with it. It was previously described on the Rust blog.
In error descriptions, references are now described in plain English, instead of as "&-ptr"
In error type descriptions, unknown numeric types are named {integer} or {float} instead of _
rustc emits a clearer error when inner attributes follow a doc comment

Language

Stabilized APIs

Libraries

Cargo

Performance

Tooling

Test binaries now support a --test-threads argument to specify the number of threads used to run tests, and which acts the same as the RUST_TEST_THREADS environment variable
The test runner now emits a warning when tests run over 60 seconds
rustdoc: Fix methods in search results
rust-lldb warns about unsupported versions of LLDB
Rust releases now come with source packages that can be installed by rustup via rustup component add rust-src. The resulting source code can be used by tools and IDES, located in the sysroot under lib/rustlib/src.

Misc

The compiler can now be built against LLVM 3.9
Many minor improvements to the documentation.
The Rust exception handling "personality" routine is now written in Rust

Compatibility Notes