Labelling parsers using non-textual tokens

[tari]

I'm attempting to update a parser to Chumsky 0.11, where my token type is a u16 and I have a custom error type that I want to implement chumsky::Error for while also being able to label parsers using labelled.

I have something like this from before:

fn letter<'a, I>() -> impl Parser<'a, I, u8, extra::Err<MyError>> + Clone
where
    I: ValueInput<'a, Token = u16, Span = SimpleSpan>,
{
    one_of(0x41..=0x5b).labelled("A-Zθ").map(|x| x - 0x41)
}

Using 0.11, this no longer works because in order to implement chumsky::Error for MyError it seems that the LabelError trait now only accepts a token as a label, meaning I would need to do .labelled(some_u16) rather than labelling the parser with a human-readable string.

That doesn't seem useful- is this a shortcoming of how the error interface was changed in 0.11, or am I missing something that would allow me to label these parsers with human-readable names while still operating on non-textual tokens?

[zesterer]

Hmm, arbitrary labels should still be supported: they just require your error type to implement LabelError<T>. It might be that the error message you're seeing is pointing you in the wrong direction by making assumptions about which implementation you want to use.

For example, Rich implements LabelError for any label that can be converted into a RichPattern:

chumsky/src/error.rs

Line 730 in 7733a7f

impl<'a, I: Input<'a>, L> LabelError<'a, I, L> for Rich<'a, I::Token, I::Span>

[tari]

Hm, yeah; I think the error messages were being misleading. Changing my impl of LabelError to take a generic L rather than directly specifying &'static str as the label type seems to work better. I haven't worked through all of it yet, but that seems promising.

[tari]

I finished working through the changes, and yes making my error type generic over the label type has fixed those errors.

Was:

impl<'src, I,> chumsky::label::LabelError<'src, I, &'static str> for MyError { ... }

Is now:

impl<'src, I, L> chumsky::label::LabelError<'src, I, L> for MyError { ... }