Using the bits parser and its error

[TheNeikos]

Heya!

I have a function that returns a PResult, but I can't easily use the bits::bits parser because the error traits it requires are not implemented/compatible with PResult's definition:

bits requires that:

• BitError: ParserError<(Input, usize)> + ErrorConvert<ByteError>
• ByteError: ParserError<Input>

But ErrorConvert is only implemented for InputError. Since PResult is the 'main' way of using winnow, this means I have to awkwardly specify the Error type using a turbofish. bits has 5 generics (even if I can infer 4 of them).

So for example an invocation looks like this:

winnow::binary::bits::bits::<_, _, InputError<(_, usize)>, _, _>((
                winnow::binary::bits::pattern(0x0, 1usize),
                winnow::binary::bits::bool,
                winnow::binary::bits::bool,
                winnow::binary::bits::take(2usize)
                    .try_map(<QualityOfService as TryFrom<u8>>::try_from),
                winnow::binary::bits::bool,
                winnow::binary::bits::bool,
                winnow::binary::bits::bool,
            ))
            .parse_next(input)
            .map_err(|_: ErrMode<InputError<_>>| {
                ErrMode::from_error_kind(input, winnow::error::ErrorKind::Slice)
            })?

Now, am I doing something wrong? Or is this just a current limitation?

Thanks for any pointers!

[epage]

But ErrorConvert is only implemented for InputError.

This is just overlooked as bit parsing doesn't get much attention (I wasn't even sure how much desire there is for this API!).

Feel free to create an issue.

Since PResult is the 'main' way of using winnow, this means I have to awkwardly specify the Error type using a turbofish. bits has 5 generics (even if I can infer 4 of them).

Note that PResult only defaults the error type. You can explicitly specify it.

[TheNeikos]

This is just overlooked as bit parsing doesn't get much attention (I wasn't even sure how much desire there is for this API!).

I like it a lot! Its super handy when one needs it, and is definitely a step up from manually using masks.

Feel free to create an issue.

Alright, I'll try to see if I can think of something to make it easier.

Note that PResult only defaults the error type. You can explicitly specify it.

Oh yeah, totally! Was mostly in the context of it being unweildy in the 'default' arrangement. I'm happy that it can be fixed!

[praveenperera]

Just ran into this myself, I think docs on how to use bits with parse_next would be helpful