The Rust nightly compiler accepts loading extensions, called plugins. They effectively change the way the compiler behaves, so they can modify the language itself. A plugin is a crate, similar to the procedural macro crate we created previously.
The difference between a procedural or standard macro and a plugin is that, while the first two modify the Rust code they are given, a plugin is able to perform extra computations that can greatly improve the performance of your crate.
Since these plugins get loaded inside the compiler, they will have access to a lot of information that standard macros don't have. Moreover, this requires using the rustc compiler and the libsyntax library as external crates, which means ...
