cgp-field 0.7.0

Context-generic programming field traits
Documentation 
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

use core::marker::PhantomData;

use crate::traits::{FieldGetter, FieldMapper};
use crate::types::{Cons, Nil};

pub struct ChainGetters<Getters>(pub PhantomData<Getters>);

impl<Context, Tag, Getter, RestGetters, ValueA, ValueB> FieldGetter<Context, Tag>
    for ChainGetters<Cons<Getter, RestGetters>>
where
    Getter: FieldMapper<Context, Tag, Value = ValueA>,
    ChainGetters<RestGetters>: FieldGetter<ValueA, Tag, Value = ValueB>,
{
    type Value = ValueB;

    fn get_field(context: &Context, tag: PhantomData<Tag>) -> &ValueB {
        Getter::map_field(context, tag, |value| {
            <ChainGetters<RestGetters>>::get_field(value, tag)
        })
    }
}

impl<Context, Tag> FieldGetter<Context, Tag> for ChainGetters<Nil> {
    type Value = Context;

    fn get_field(context: &Context, _tag: PhantomData<Tag>) -> &Context {
        context
    }
}