Automatic parsing of Vec<SomeSynType> collections

[sam0x17]

I think the built-in support for bracket/brace/paren delimited things is great. I have been thinking about seeing if I could submit a PR that would make the following "just work":

#[derive(derive_syn_parse::Parse))
struct MyArgs {
    #[brace]
    _brace: Brace,
    #[inside(_brace)]
    contents: Vec<Stmt>,
}

In other words, I want to extend derive_syn_parse so that any Vec containing a type that implements Parse is automatically digestible by derive_syn_parse.

The way this would work under the hood is in the expansion, we would automatically output the following for such fields within the Parse implementation:

let mut #field_name = Vec::new();
while (some condition relating to the subsequent field) {
    #field_name.push(input.parse()?);
}

Would you be interested in such a PR and/or do you think something like this would be feasible @sharnoff?

[sharnoff]

Late reply here as well, as I'm going through everything now.

Any automatic handling of Vec<T> would have to be syntax-based, because derive-syn-parse, as a proc macro crate, cannot expose any other public items (unless things have changed since I first wrote this).

If we try, we get:

error: `proc-macro` crate types currently cannot export any items other than functions tagged with `#[proc_macro]`, `#[proc_macro_derive]`, or `#[proc_macro_attribute]`

(Incidentally, this is also why we don't have automated handling of Delimited<P, T>)

That said, I think it'd make sense to provide this behavior built-in. I'd be happy to have it under #[repeat] or something similar (bikeshedding welcome! you probably use this more than I do 😅).

What do you think? (Is this still relevant?)

[sam0x17]

Yeah I mean I think something around this would definitely be helpful. I've run into this same problem making my own parsing library quoth recently, and I don't have a perfect solution there either