rustc/vendor/if_chain/README.md

if_chain

This crate provides a single macro called if_chain!.

if_chain! lets you write long chains of nested if and if let statements without the associated rightward drift. It also supports multiple patterns (e.g. if let Foo(a) | Bar(a) = b) in places where Rust would normally not allow them.

For more information on this crate, see the documentation and associated blog post.