Hi! Thank you for this cool work!

I think that this approach could also address this issue. More precisely, I mean persistent data storage for all macros. This could be obtained by Wasm multimodules approach and sharing the same memory for one modules. Moreover, SQLite or Redis could be used to save state. All of them compiled in such a way to work like in-memory db without any imports. With our proc macro they could be used in the following way:

#[invocation_handler(side_modules = redis)]
fn run(arg: String) -> Vec<u8> {
    redis::call("SET A 1")
}

#[invocation_handler(side_modules = sqlite)]
fn run(arg: String) -> Vec<u8> {
    sqlite::call("SELECT * FROM Table")
}

And I can adapt them to any convention.

What do you think about that? I haven't look at the internals of watt, so can't estimate how many should be add to support this idea.