Really interesting writeup. What stood out to me most was the shift from the earlier node execution path to the streamed path. The benchmark gap between execute_r_nodes and execute_stream is huge, and the latter getting relatively close to the handwritten C++ baseline is the part I keep thinking about.

After building this, where do you think most compiler complexity actually comes from? My impression from your post is that a lot of the “millions of lines” are not from the core syntax-to-execution path itself, but from language surface area, tooling, diagnostics, optimization passes, and long-tail ecosystem baggage.