Let's write a compiler, part 4: Testing

It seems like we're going to have the same discussion on this topic every day until all parts are posted.

> more like an assembler than a compiler since there is no mess and it outputs C code.

Yes, translating between closely related languages is often like this: the mapping between their constructs is 1-to-1 and almost trivial. But try translating e.g. λ-calculus into C in one go, without separate lambda-lifting/closure-converting steps: it's absolutely doable but quite messy.

> feels more like an assembler than a compiler

Yes it's a kind of transpiler, or template compiler, a typically 1-1 mapping.

When absolute compiler perf isn't required, I love nanopass compilers for this. Each pass slowly massages a slightly different IR towards the final form and there isn't really a limit to how different the code source and end target can be, just needs more passes.