treaty -


1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70

use crate::{
    any::{TypeName, WithContextLt}, bijective_higher_ranked_type, effect::{Effect, Future}, hkt::AnySizedSend, protocol::{walker::hint::HintMeta, Visitor}, Flow
};

use super::Status;

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

bijective_higher_ranked_type! {
    pub type DynRecoverable['ctx][E]: WithContextLt['ctx][]
    for<'a>
    (dyn Recoverable<'ctx, E> + Send + 'a)
    where {
        E: Effect
    }
}

bijective_higher_ranked_type! {
    pub type [][E]: TypeName[][]
    for<'ctx>
    (DynRecoverable<'ctx, E>)
    where {
        E: Effect
    }
}

pub trait RecoverableScope<'ctx, E: Effect> {
    fn new_walk<'a>(&'a mut self, visitor: Visitor<'a, 'ctx>) -> Future<'a, Flow, E>;
}

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

bijective_higher_ranked_type! {
    pub type RecoverableKnownHkt[][]: AnySizedSend[][] for<'lt> (())
}

impl<'ctx, E: Effect> HintMeta<'ctx> for DynRecoverable<'ctx, E> {
    type Known = RecoverableKnownHkt;

    type Hint = ();
}

pub fn visit_recoverable<'a, 'ctx, E: Effect>(
    visitor: Visitor<'a, 'ctx>,
    scope: DynRecoverableScope<'a, 'ctx, E>,
) -> Future<'a, Status, E> {
    if let Some(object) = visitor.upcast_mut::<DynRecoverable<'ctx, E>>() {
        // Allow the visitor to give a hint if it wants.
        E::map(object.visit(scope), |flow| match flow {
            Flow::Continue => {
                // The visitor wants the walker to continue to it's normal
                // walking.
                Status::r#continue()
            }
            Flow::Break | Flow::Done => {
                // The visitor is done (either because of an error or because
                // it already used a hint).
                Status::r#break()
            }
        })
    } else {
        // If the visitor doesn't support request hint then we continue.
        E::ready(Status::skipped())
    }
}