Version 1.27.2 (2018-07-20)

Compatibility Notes

The borrow checker was fixed to avoid potential unsoundness when using match ergonomics: #52213.

rustdoc would execute plugins in the /tmp/rustdoc/plugins directory when running, which enabled executing code as some other user on a given machine. This release fixes that vulnerability; you can read more about this on the blog. The associated CVE is CVE-2018-1000622.

Thank you to Red Hat for responsibly disclosing this vulnerability to us.

The borrow checker was fixed to avoid an additional potential unsoundness when using match ergonomics: #51415, #49534.

Removed 'proc' from the reserved keywords list. This allows proc to be used as an identifier.
The dyn syntax is now available. This syntax is equivalent to the bare Trait syntax, and should make it clearer when being used in tandem with impl Trait because it is equivalent to the following syntax: &Trait == &dyn Trait, &mut Trait == &mut dyn Trait, and Box<Trait> == Box<dyn Trait>.
Attributes on generic parameters such as types and lifetimes are now stable. e.g. fn foo<#[lifetime_attr] 'a, #[type_attr] T: 'a>() {}
The #[must_use] attribute can now also be used on functions as well as types. It provides a lint that by default warns users when the value returned by a function has not been used.

cargo-metadata now includes authors, categories, keywords, readme, and repository fields.
cargo-metadata now includes a package's metadata table.
Added the --target-dir optional argument. This allows you to specify a different directory than target for placing compilation artifacts.
Cargo will be adding automatic target inference for binaries, benchmarks, examples, and tests in the Rust 2018 edition. If your project specifies specific targets, e.g. using [[bin]], and have other binaries in locations where cargo would infer a binary, Cargo will produce a warning. You can disable this feature ahead of time by setting any of the following to false: autobins, autobenches, autoexamples, autotests.
Cargo will now cache compiler information. This can be disabled by setting CARGO_CACHE_RUSTC_INFO=0 in your environment.

Calling a CharExt or StrExt method directly on core will no longer work. e.g. ::core::prelude::v1::StrExt::is_empty("") will not compile, "".is_empty() will still compile.
Debug output on atomic::{AtomicBool, AtomicIsize, AtomicPtr, AtomicUsize} will only print the inner type. E.g. print!("{:?}", AtomicBool::new(true)) will print true, not AtomicBool(true).
The maximum number for repr(align(N)) is now 2²⁹. Previously you could enter higher numbers but they were not supported by LLVM. Up to 512MB alignment should cover all use cases.
The .description() method on the std::error::Error trait has been soft-deprecated. It is no longer required to implement it.