Fixes for 427

[VictorKoenders]

#427 uncovered some issues.

1. if there is a newline in a doc comment, rust's token stream feeds us 2x '#' in a row with no attribute group. bincode_derive now handles this correctly
2. bincode_derive now supports min_const_generics
3. bincode_derive now supports c-style enums where the variants have a fixed value

For 3 I have made it so that bincode_derive outputs code like this:

CStyleEnum output

enum CStyleEnum {
    A = 1,
    B = 2,
    C,
    D = 5,
    E,
}


impl bincode::de::Decode for CStyleEnum {
    fn decode<D: bincode::de::Decoder>(
        mut decoder: D,
    ) -> Result<Self, bincode::error::DecodeError> {
        let variant_index = <u32 as bincode::de::Decode>::decode(&mut decoder)?;
        match variant_index {
            1 => Ok(Self::A {}),
            2 => Ok(Self::B {}),
            x if x == 2 + 1u32 => Ok(Self::C {}),
            5 => Ok(Self::D {}),
            x if x == 5 + 1u32 => Ok(Self::E {}),
            variant => Err(bincode::error::DecodeError::UnexpectedVariant {
                found: variant,
                type_name: "CStyleEnum",
                allowed: bincode::error::AllowedEnumVariants::Allowed(&[
                    1,
                    2,
                    2 + 1u32,
                    5,
                    5 + 1u32,
                ]),
            }),
        }
    }
}

impl bincode::enc::Encode for CStyleEnum {
    fn encode<E: bincode::enc::Encoder>(
        &self,
        mut encoder: E,
    ) -> core::result::Result<(), bincode::error::EncodeError> {
        match self {
            Self::A => {
                <u32 as bincode::enc::Encode>::encode(&(1), &mut encoder)?;
            }
            Self::B => {
                <u32 as bincode::enc::Encode>::encode(&(2), &mut encoder)?;
            }
            Self::C => {
                <u32 as bincode::enc::Encode>::encode(&(2 + 1u32), &mut encoder)?;
            }
            Self::D => {
                <u32 as bincode::enc::Encode>::encode(&(5), &mut encoder)?;
            }
            Self::E => {
                <u32 as bincode::enc::Encode>::encode(&(5 + 1u32), &mut encoder)?;
            }
        }
        Ok(())
    }
}

[VictorKoenders]

@haata the only thing that is left of #427 is that heapless::Vec does not support Decode/Encode for now. I think it's be best to use a wrapper for this that implements Decode/Encode. Something like:

#[repr(transparent)]
struct BincodeVec<T, const N: usize>(heapless::Vec<T, N>);

impl<T: Decode + Default, const N: usize> Decode for BincodeVec<T, N> {
    fn decode<D: bincode::de::Decoder>(
        mut decoder: D,
    ) -> Result<Self, bincode::error::DecodeError> {
        let len = usize::decode(&mut decoder)?;
        let mut vec = heapless::Vec::default();
        for _ in 0..len {
            // TODO: handle the heapless error?
            let _ = vec.push(T::decode(&mut decoder)?);
        }
        Ok(Self(vec))
    }
}

impl<T: Encode, const N: usize> Encode for BincodeVec<T, N> {
    fn encode<E: bincode::enc::Encoder>(
        &self,
        mut encoder: E,
    ) -> Result<(), bincode::error::EncodeError> {
        self.0.len().encode(&mut encoder)?;
        for val in self.0.iter() {
            val.encode(&mut encoder)?;
        }
        Ok(())
    }
}

[codecov-commenter]

Codecov Report

Merging #428 (57ed145) into trunk (4120069) will decrease coverage by 1.75%.
The diff coverage is 31.57%.

@@            Coverage Diff             @@
##            trunk     #428      +/-   ##
==========================================
- Coverage   71.04%   69.28%   -1.76%     
==========================================
  Files          41       41              
  Lines        2811     2924     +113     
==========================================
+ Hits         1997     2026      +29     
- Misses        814      898      +84     

Impacted Files	Coverage Δ
derive/src/derive_enum.rs	0.00% <0.00%> (ø)
derive/src/generate/stream_builder.rs	0.00% <ø> (ø)
derive/src/lib.rs	7.40% <0.00%> (ø)
derive/src/parse/mod.rs	90.74% <0.00%> (-5.34%)	⬇️
src/de/impls.rs	76.47% <0.00%> (+0.88%)	⬆️
src/error.rs	0.00% <ø> (ø)
src/features/impl_std.rs	72.86% <0.00%> (+1.11%)	⬆️
derive/src/parse/body.rs	68.24% <25.58%> (-4.11%)	⬇️
derive/src/parse/generics.rs	62.45% <52.23%> (-4.50%)	⬇️
derive/src/parse/attributes.rs	62.06% <55.00%> (-11.85%)	⬇️
... and 4 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 4120069...57ed145. Read the comment docs.