rkyv_wrappers.rs

//! Wrapper that allows changing the generic type of a PhantomData<T>
//!
//! Copied from <https://github.com/rkyv/rkyv_contrib> (MIT-Apache2 licences) which isn’t published yet.

use rkyv::{
    rancor::Fallible,
    with::{ArchiveWith, DeserializeWith, SerializeWith},
    Place,
};
use std::marker::PhantomData;

#[derive(Debug)]
/// A wrapper that allows for changing the generic type of a `PhantomData<T>`.
pub struct CustomPhantom<NT: ?Sized> {
    _data: PhantomData<*const NT>,
}

impl<OT: ?Sized, NT: ?Sized> ArchiveWith<PhantomData<OT>> for CustomPhantom<NT> {
    type Archived = PhantomData<NT>;
    type Resolver = ();

    #[inline]
    fn resolve_with(_: &PhantomData<OT>, _: Self::Resolver, _: Place<Self::Archived>) {}
}

impl<OT: ?Sized, NT: ?Sized, S: Fallible + ?Sized> SerializeWith<PhantomData<OT>, S>
    for CustomPhantom<NT>
{
    #[inline]
    fn serialize_with(_: &PhantomData<OT>, _: &mut S) -> Result<Self::Resolver, S::Error> {
        Ok(())
    }
}

impl<OT: ?Sized, NT: ?Sized, D: Fallible + ?Sized>
    DeserializeWith<PhantomData<NT>, PhantomData<OT>, D> for CustomPhantom<NT>
{
    #[inline]
    fn deserialize_with(_: &PhantomData<NT>, _: &mut D) -> Result<PhantomData<OT>, D::Error> {
        Ok(PhantomData)
    }
}

// TODO: implement PartialEq with generics.

#[cfg(feature = "rkyv-serialize")]
impl<NT: ?Sized> PartialEq<CustomPhantom<NT>> for CustomPhantom<NT> {
    fn eq(&self, _other: &CustomPhantom<NT>) -> bool {
        true
    }
}