treaty -


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use crate::{
    any::TypeName,
    effect::{Effect, Effective, ErasedEffective},
    higher_ranked_type,
    hkt::Marker,
    protocol::{
        walker::hint::{HintMeta, Meta},
        DynVisitor,
    },
    Status,
};

use super::VisitResult;

pub trait Recoverable<'ctx, E: Effect> {
    fn visit<'a>(
        &'a mut self,
        scope: DynRecoverableScope<'a, 'ctx, E>,
    ) -> ErasedEffective<'a, VisitResult<DynRecoverableScope<'a, 'ctx, E>>, E>;
}

pub struct RecoverableProto<E: Effect>(Marker<E>);

higher_ranked_type! {
    impl TypeName {
        impl['a, 'ctx, E] type T['a, 'ctx] for RecoverableProto<E> =
            dyn Recoverable<'ctx, E> + Send + Sync + 'a
        where {
            E: Effect
        };

        impl['a, 'ctx, E] type HigherRanked['a, 'ctx] for dyn Recoverable<'ctx, E> + Send + Sync + 'a =
            RecoverableProto<E>
        where {
            E: Effect
        };
    }
}

pub trait RecoverableScope<'ctx, E: Effect> {
    fn new_walk<'this: 'effect, 'visitor: 'effect, 'effect>(
        &'this mut self,
        visitor: DynVisitor<'visitor, 'ctx>,
    ) -> ErasedEffective<'effect, Status, E>;
}

pub type DynRecoverableScope<'a, 'ctx, E> =
    &'a mut (dyn RecoverableScope<'ctx, E> + Send + Sync + 'a);

pub struct RecoverableKnown;

higher_ranked_type! {
    impl Meta {
        impl['a, 'ctx] type T['a, 'ctx] for RecoverableKnown =
            RecoverableKnown;

        impl['a, 'ctx] type HigherRanked['a, 'ctx] for RecoverableKnown =
            RecoverableKnown;
    }
}

impl<E: Effect> HintMeta for RecoverableProto<E> {
    type Known = RecoverableKnown;

    type Hint = ();

    type Effect = E;
}

pub fn visit_recoverable<'a, 'ctx, E: Effect>(
    visitor: DynVisitor<'a, 'ctx>,
    scope: DynRecoverableScope<'a, 'ctx, E>,
) -> ErasedEffective<'a, VisitResult<DynRecoverableScope<'a, 'ctx, E>>, E> {
    if let Some(object) = visitor.0.upcast_mut::<RecoverableProto<E>>() {
        // Allow the visitor to give a hint if it wants.
        object.visit(scope)
    } else {
        // If the visitor doesn't support request hint then we continue.
        E::ready(VisitResult::Skipped(scope)).into_erased()
    }
}