Attribute Macro encoder 

#[encoder]

This is an attribute macro that must be used when implementing a Encoder.

It is required to use because a Encoder implementation might introduce new associated types in the future, and this not yet supported on a language level in Rust. So this attribute macro polyfills any missing types automatically.

Note that if the Cx or Mode associated types are not specified, they will be defaulted to any type parameters which starts with the uppercase C or M respectively.

Note that using this macro directly from musli_core requires you to use the #[musli_core::encoder(crate = musli_core)] attribute.

Examples

use std::fmt;
use std::marker::PhantomData;

use musli_core::Context;
use musli_core::en::{Encoder, Encode};

struct MyEncoder<'a, C, M> {
    value: &'a mut Option<u32>,
    cx: C,
    _marker: PhantomData<M>,
}

#[musli_core::encoder(crate = musli_core)]
impl<C, M> Encoder for MyEncoder<'_, C, M>
where
    C: Context,
    M: 'static,
{
    #[inline]
    fn expecting(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "32-bit unsigned integers")
    }

    #[inline]
    fn encode<T>(self, value: T) -> Result<(), C::Error>
    where
        T: Encode<Self::Mode>,
    {
        value.encode(self)
    }

    #[inline]
    fn encode_u32(self, value: u32) -> Result<(), Self::Error> {
        *self.value = Some(value);
        Ok(())
    }
}