Declarative API

[kaleidawave]

Currently the way to create an implementation is to create a new Trait structure with a vector of TraitItems with their respective handlers. The handlers are call-backs that are fired for every structure.

These handlers are currently imperative in the way the handler evaluates the input and reads the data to generate a token stream. A possible way could be to generate a trait and it's handlers using a declarative form from a TokenStream generated by quote:

let my_trait = Trait::from_tokens(quote! {
    trait ::my_crate::MyTrait {
        fn method_one(&self) {
            #(do_thing(self.*);)*
        }
    }
});

This should be possible by creating a ComputedBody struct which implements for<'a> Fn(Item<'a>) -> HandlerResult and evaluates based on the declaration in the token stream.

Few complications:

• How to do a basic set of things declarative
• Where to draw the line as to where an imperiative implementation is required
• How to parse the token stream especially function bodies