[librustc_privacy](https://github.com/rust-lang/rust/blob/master/src/librustc_privacy/error_codes.rs),
[librustc_resolve](https://github.com/rust-lang/rust/blob/master/src/librustc_resolve/error_codes.rs),
[librustc_codegen_llvm](https://github.com/rust-lang/rust/blob/master/src/librustc_codegen_llvm/error_codes.rs),
- [librustc_plugin](https://github.com/rust-lang/rust/blob/master/src/librustc_plugin/error_codes.rs),
+ [librustc_plugin_impl](https://github.com/rust-lang/rust/blob/master/src/librustc_plugin/error_codes.rs),
[librustc_typeck](https://github.com/rust-lang/rust/blob/master/src/librustc_typeck/error_codes.rs).
* Explanations have full markdown support. Use it, especially to highlight
code with backticks.