Returning `WithCtx` trait is missing type information from `Parser`

[ryansuhartanto]

Take a look at this:
https://codesandbox.io/p/devbox/jolly-engelbart-967dnc?embed=1&file=%2Fsrc%2Flib.rs

I expect the .with_ctx(...) can be easily be piped before .parse(...), but it throws E0284 instead.
A bit of an issue too, the .configure(...)'s second parameter (ctx) throws E0282 without explicit type information.

I provided a workaround by making WithCtx into a Parser first.

Here's the actual code from the link:

use chumsky::prelude::*;

#[derive(Debug, Clone, Copy, Default)]
pub struct ExtraContext {
    pub dont_parse: bool,
}

pub fn parser<'src>() -> impl Parser<'src, &'src str, bool, extra::Context<ExtraContext>> {
    any::<'src, _, extra::Context<ExtraContext>>() // I need this so `configure` has proper `ctx` type
        .contextual()
        .configure(|_cfg, ctx| !ctx.dont_parse)
        .to(true)
}

// Workaround
pub fn parser_with_ctx<'src>(
    ctx: ExtraContext,
) -> impl Parser<'src, &'src str, bool, extra::Context<ExtraContext>> {
    parser().with_ctx(ctx)
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_parser() {
        assert_eq!(
            parser()
                // Error if uncommented
                //.with_ctx(ExtraContext { dont_parse: false })
                .parse("a")
                .into_result(),
            Ok(true)
        )
    }

    #[test]
    fn test_parser_with_ctx() {
        assert_eq!(
            parser_with_ctx(ExtraContext { dont_parse: false })
                .parse("a")
                .into_result(),
            Ok(true)
        )
    }
}

error[E0282]: type annotations needed for `&_`
  --> src/lib.rs:11:27
   |
11 |         .configure(|_cfg, ctx| !ctx.dont_parse)
   |                           ^^^   -------------- type must be known at this point
   |
help: consider giving this closure parameter an explicit type, where the placeholders `_` are specified
   |
11 |         .configure(|_cfg, ctx: &_| !ctx.dont_parse)
   |                              ++++

error[E0284]: type annotations needed
  --> src/lib.rs:32:18
   |
32 |                 .parse("a")
   |                  ^^^^^
   |
   = note: cannot satisfy `<_ as ParserExtra<'_, &str>>::Error == _`

I'm quite new to Rust. Is this intended or simply a Rust limitation that's outside the scope of this library?

[Zij-IT]

The problem lies in the implementation of Parser for WithContext:

impl<'src, I, O, E, A, Ctx> Parser<'src, I, O, E> for WithCtx<A, Ctx>
where
    I: Input<'src>,
    E: ParserExtra<'src, I>,
    A: Parser<'src, I, O, extra::Full<E::Error, E::State, Ctx>>,
    Ctx: 'src,
{
    /* snip */
}

The A is the generic for the original parser that WithContext was created with. The problem is that Chumsky doesn't retain any information about what type of parser A was, only that it :/ So, it's a Chumsky problem

[ryansuhartanto]

I'll see if I can learn more about Rust and make a PR that fixes this.