Hacking rustc: Contributing to the Compiler by Esteban Kuber
Compilers are very often treated as a daunting "black box" that only a select few can understand. In reality compilers are "just" another type of program. As long as you know the language the compiler is written in, the language the compiler compiles, and have the time, you too can work on them. If you ever were intrigued about modifying a compiler, or you encountered a bug that you really want fixed soon, this is your chance to roll your sleeves and do it yourself, as we go over the basics of hacking on rustc.