Decode breaks when conditionally using write!

[Dirbaio]

    enum OneOrTwo {
        One(u32),
        Two((u32, u32)),
    }

    impl defmt::Format for OneOrTwo {
        fn format(&self, fmt: Formatter) {
            match self {
                Self::One(x) => defmt::write!(fmt, "{=u32}", x),
                Self::Two((x, y)) => defmt::write!(fmt, "{=u32}-{=u32}", x, y),
            }
        }
    }

    let mix = [OneOrTwo::One(1), OneOrTwo::Two((2, 3))];
    defmt::info!("boom: {=[?]}", &mix[..]);

prints

 INFO  boom: [1, 2]
└─ spam::run_test::{{impl}}::format @ /home/dirbaio/nanofmt/fw/src/bin/spam.rs:51
(HOST) ERROR failed to decode defmt data: [3, 0, 0, 0, 28, 1, 0, 0, ... etc

This happens because slices omit the format tag for all but the first item assuming they're equal. With custom Format impls they're not necessarily equal.

[japaric]

this appears to already have been fixed in the main branch (possibly by #508)