Rust 1.30.0

Language

• Procedural macros are now available. These kinds of macros allow for more powerful code generation. There is a new chapter available in the Rust Programming Language book that goes further in depth.
• You can now use keywords as identifiers using the raw identifiers syntax (r#), e.g. let r#for = true;
• Using anonymous parameters in traits is now deprecated with a warning and will be a hard error in the 2018 edition.
• You can now use crate in paths. This allows you to refer to the crate root in the path, e.g. use crate::foo; refers to foo in src/lib.rs.
• Using a external crate no longer requires being prefixed with ::. Previously, using a external crate in a module without a use statement required let json = ::serde_json::from_str(foo); but can now be written as let json = serde_json::from_str(foo);.
• You can now apply the #[used] attribute to static items to prevent the compiler from optimising them away, even if they appear to be unused, e.g. #[used] static FOO: u32 = 1;
• You can now import and reexport macros from other crates with the use syntax. Macros exported with #[macro_export] are now placed into the root module of the crate. If your macro relies on calling other local macros, it is recommended to export with the #[macro_export(local_inner_macros)] attribute so users won't have to import those macros.
• You can now catch visibility keywords (e.g. pub, pub(crate)) in macros using the vis specifier.
• Non-macro attributes now allow all forms of literals, not just strings. Previously, you would write #[attr("true")], and you can now write #[attr(true)].
• You can now specify a function to handle a panic in the Rust runtime with the #[panic_handler] attribute.

Compiler

• Added the riscv32imc-unknown-none-elf target.
• Added the aarch64-unknown-netbsd target
• Upgraded to LLVM 8.

Libraries

• ManuallyDrop now allows the inner type to be unsized.

Stabilized APIs

• Ipv4Addr::BROADCAST

• Ipv4Addr::LOCALHOST

• Ipv4Addr::UNSPECIFIED

• Ipv6Addr::LOCALHOST

• Ipv6Addr::UNSPECIFIED

• Iterator::find_map

  The following methods are replacement methods for trim_left, trim_right, trim_left_matches, and trim_right_matches, which will be deprecated in 1.33.0:

• str::trim_end_matches

• str::trim_end

• str::trim_start_matches

• str::trim_start

Cargo

• cargo run doesn't require specifying a package in workspaces.
• cargo doc now supports --message-format=json. This is equivalent to calling rustdoc --error-format=json.
• Cargo will now provide a progress bar for builds.

Misc

• rustdoc allows you to specify what edition to treat your code as with the --edition option.
• rustdoc now has the --color (specify whether to output color) and --error-format (specify error format, e.g. json) options.
• We now distribute a rust-gdbgui script that invokes gdbgui with Rust debug symbols.
• Attributes from Rust tools such as rustfmt or clippy are now available, e.g. #[rustfmt::skip] will skip formatting the next item.