Restriction on Serializing Zero-Sized Types Affects Marker Component Usage about borsh-rs HOT 7 CLOSED

@cybersoulK , this is probably due to an optimization from compiler, where it makes single-variant enum zero-size.
rust-lang/rust#37649 .
Can likely be helped with adding #[repr(u8)] attribute to the definition or just adding another variant.

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oh, congrats coming a long way with borsh 1.2!

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@cybersoulK , we've decided that using zero-sized types as keys in HashSet/HashMap is impractical, as there cannot be more that one instance of the type (and, transitively, more than one key in collection of this type).

Please share a minimal excerpt from your code to illustrate how this case is useful for you.
Ideally, if you shared it as a compilable repo with a previous version of borsh.

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honestly i am having a hard time replicating it manually.

I thought it was

struct Marker;
enum Enum {
    Marker(Marker)
    SomethingElse(f32, ...)
}
Vec<Enum>

but i am able to run that successfuly, is there a way to print the exact type that's causing the issue?

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yep, i cannot see any Hashmap Key, or Vec Value that is an empty struct. i looked 10 times at the data

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Ok, i got it:

#[Component]
pub struct Cooldowns(pub HashMap<Skill, Interval>);

#[Component]
pub enum Skill {
    Dash,
}

where right now, Skill is only one variant.

I feel relieved that my assumption of the markers was wrong.
But still, why ban an enum from being a key, if it only has one variant?

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Thank you ❤️, #[repr(u8)] should be good enough.
If there was anything can could be done is Borsh Derive to correct it automatically, would be nice.

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