My idea was that with single pass, I can build SSA form during AST construction, and use phi-nodes to update type flow info. Then I could use SSA form to prove that I can use certain optimized bytecode instructions when a variable/register is known to be of certain type (I have virtual registers and fat instructions, eg ADD takes 2 sources and destination). Maybe I'm mixing control flow, type flow and SSA. I do not understand where I should stop with the pipeline if I use bytecode/VM.

The paper is: Brandis, Marc M., and Hanspeter Mössenböck. "Single-pass generation of static single-assignment form for structured languages." (https://bernsteinbear.com/assets/img/brandis-single-pass.pdf). It was quite understandable to me. For a deeper dive with proper SSA construction with dominance frontiers I could not find time to dig deeper, many other papers on SSA require focused CS work on them, not practically feasible for a side project. Also, single-pass is a requirement for very fast compilation to bytecode and LSP feedback.

I tried to read TS and Pyright source code, they share the same style of immense files and nested local functions, that was quite a steep wall to understand actual inner workings in detail. Maybe TS implementation in Go will be easier to read, it's on my later TODO list. It's tempting to use AI for help, but I'm quite experienced already with undoing AI work when it takes a wrong direction and I do not notice early.