> Writing a parser by hand is tricky and not worth the alleged performance increases Not my experience at all. It is easy and fun. And I can actually debug the

> Writing a parser by hand is tricky and not worth the alleged performance increases Not my experience at all. It is easy and fun. And I can actually debug the parser instead of staring at generated noise/tables. And the performance is usually x2 or more, making it worth it for compiling large projects. Background: I am the maintainer of a high performance JIT optimising compiler for a Haskell like rules language used in production by commercial companies around the world. And yes tests are absolutely necessary to maintain a commercial optimising compiler. I use a test suite of more than 9000 tests. The result is zero bugs in production the last 5+ years. The upfront cost is absolutely worth it because I can make massive changes to the internals of the compiler and still confidently release the result into production. As for type checking: you typically won’t find any useful stuff in compiler books. However there is a massive amount of information available on type checking and type systems online. It is a huge research area and kinda the foundation of computer science. There are whole books dedicated to type checking and type systems alone.