Support Vec, HashMap and more types

[sw1sh]

I'm a Rust noob, so some things could probably be improved. I'm trying to build a paclet for this small library: https://github.com/jcmgray/cotengrust/blob/main/src/lib.rs. With these additional types and traits, I've been able to just use #[wll::export] attribute on a function I need:

#[wll::export]
fn optimize_optimal(
    inputs: Vec<Vec<char>>,
    output: Vec<char>,
    size_dict: Dict<char, f32>,
    minimize: Option<String>,
    cost_cap: Option<Score>,
    search_outer: Option<bool>,
    simplify: Option<bool>,
    use_ssa: Option<bool>,
) -> Vec<Vec<Node>>

And it works without fiddling with wstp. Pretty cool stuff! :)

[ConnorGray]

Hi @sw1sh, as discussed in our meeting, the basic implementation here is exactly right, but we may want to improve the error reporting to help users out in cases where they accidentally pass in strings that are not a single char in length.

My proposal would be something like:

unsafe fn from_arg(arg: &MArgument) -> Self {
    let string = String::from_arg(arg);

    let mut chars = string.chars();

    let Some(char) = chars.next() else {
        panic!("char argument string was empty")
    };

    if chars.next().is_some() {
        panic!("char argument string contains multiple chars: {string}")
    }

    char
}