The "different laws" thing really should be handled by changing the types of all the nodes around the critical passes. Unfortunately, every language I know suck

The "different laws" thing really should be handled by changing the types of all the nodes around the critical passes. Unfortunately, every language I know sucks at typing if you want to avoid all the copying that the naive approach gives you. (remember especially that some types will only exist during certain phases. The most basic of these is: which token types are valid in a parse tree and which aren't? E.g. binary operator tokens usually remain valid, but parentheses disappear, whereas many new types appear. For later phases this only gets more complicated.)