Thanks for the response, getting to an ‘exec-free’ compiler was what I had in mind.
I actually thought I should make that more tangible, so I mocked something up last night, and given it just a little bit of polish this morning.
I’ve put that code up on https://gist.github.com/Pike/1faef13e891a73c9835bf4b895c59987.
The starting point is a runtime tree, which can be instantiated either for a resource or just an entry. Most of the AST constructs in the parser have a matching runtime AST, I just dropped some abstract base classes, I think.
The __call__ methods on those would effectively be what your code generator would create, to a significant part. Only the literals and pattern are interesting. I see that my NumberLiteral is a good deal away from your implementation stil.
The Compiler class is just the visitor that transforms parser->runtime, plus an optimizer. I’ve demoed taking string literals out of placeables, and concating string literals in patterns, and fast-forwarding simple text instead of pattern expression.
Obviously, that code isn’t even trying to be complete 
Ideas based on that concept that go around in my head:
- create a
class IsolatingVarRef(VariableReference)when isolation is wanted - keep
parsedandrunnablemembers on bundle, and only compile messages on demand - loop detection could be done at compile time, depending on whether we’d want loop detection to kick in on any possible loop, or just when actually triggering a loop
I did also spend more time looking at your compiler branch, and just want to emphasize that I realize how much energy you’ve put into that.