This is pretty cool, but couldn't this have been leveraged to be just an intermediate step of the actual source-level substitution? i.e. you run this tool on t

This is pretty cool, but couldn't this have been leveraged to be just an intermediate step of the actual source-level substitution? i.e. you run this tool on the codebase, cache somewhere the post-tokenized-and-rewritten output, then run a separate tool that does the '' -> b'' change in the source code, rerun the tokenizer without the translation and verify the two outputs are identical? This way one would not need to do this at runtime every time, and you would have a guarantee that your source code text changes are correct (because you compare the tokenized output between the '' and the b'' versions of the code).