serde integration, or custom proc macro for function arguments

[samuelcolvin]

Code like this is ugly, and similar code will exist in lots of places

monty/crates/monty/src/types/datetime.rs

Line 183 in 3759c96

pub(crate) fn init(heap: &mut Heap<impl ResourceTracker>, args: ArgValues, interns: &Interns) -> RunResult<Value> {

We should support parsing args/kwargs into a struct using serde::Deserialize if it can support all forms of arguments, or a custom procedural macro if it can't.

So you would do something like

#[derive(serde::Deserialize)]
struct FunctionArgs {
  #[args_kwargs]
  a: i64,
  #[kwarg_only]
  b: String,
}

[Embers-of-the-Fire]

I personally prefer a different approach (ignoring implementation complexity):

declare_args!(FunctionArgs( a: i64, b: String, /, *args: f32 ));

which expands to

struct FunctionArgs {
    a: i64,
    b: String,
    args: Vec<f32>,
}

[davidhewitt]

I suspect serde is not quite the right abstraction (unsure, I could be wrong?), but yes, a way to cleanly express function signatures which can compile to efficient extraction code would be nice.