Announcing Rust 1.13

This release contains important security updates to Cargo, which depends on curl and OpenSSL, which both published security updates recently. For more information see the respective announcements for curl 7.51.0 and OpenSSL 1.0.2j.

Macros can now be used in type position (RFC 873), and attributes can be applied to statements (RFC 16):

// Use a macro to name a type
macro_rules! Tuple {
    { $A:ty,$B:ty } => { ($A, $B) }
}

let x: Tuple!(i32, i32) = (1, 2);

// Apply a lint attribute to a single statement
#[allow(non_snake_case)]
let BAD_STYLE = List::new();

Inline drop flags have been removed. Previously, in case of a conditional move, the compiler would store a “drop flag” inline in a struct (increasing its size) to keep track of whether or not it needs to be dropped. This means that some structs take up some unexpected extra space, which interfered with things like passing types with destructors over FFI. It also was a waste of space for code that didn’t have conditional moves. In 1.12, MIR became the default, which laid the groundwork for many improvements, including getting rid of these inline drop flags. Now, drop flags are stored in an extra slot on the stack frames of functions that need them.

1.13 contains a serious bug in code generation for ARM targets using hardware floats (which is most ARM targets). ARM targets in Rust are presently in our 2nd support tier, so this bug was not determined to block the release. Because 1.13 contains a security update, users that must target ARM are encouraged to use the 1.14 betas, which will soon get a fix for ARM.

Language stabilizations

• The Reflect trait is deprecated. See the explanation of what this means for parametricity in Rust.
• Stabilize macros in type position. RFC 873.
• Stabilize attributes on statements. RFC 16.

Library stabilizations

• checked_abs, wrapping_abs, and overflowing_abs
• RefCell::try_borrow, and RefCell::try_borrow_mut
• Add assert_ne! and debug_assert_ne!
• Implement AsRef<[T]> for std::slice::Iter
• Implement CoerceUnsized for {Cell, RefCell, UnsafeCell}
• Implement Debug for std::path::{Components,Iter}
• Implement conversion traits for char
• SipHasher is deprecated. Use DefaultHasher.
• Implement more traits for std::io::ErrorKind

Cargo features

• cargo: Add –all-features flag to cargo
• cargo: Add –message-format flag

See the detailed release notes for more.