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

pub trait TypeAppParam {
    type Param;
}

pub trait WithTypeArg<T: ?Sized> {
    type Type: TypeApp<Self, T>;
}

pub trait TypeApp<TCon, T>:
    is_type::Is<Type = <TCon as WithTypeArg<T>>::Type> + TypeAppParam
where
    TCon: WithTypeArg<T> + ?Sized,
    T: ?Sized,
{
}

pub struct Ref {}
pub struct Val {}

// This is useful for traits like CallMap where you're not sure whether your impls are either taking
// reference or value arguments.
// There might be a cleaner approach to this but I haven't found it.
pub trait TypeAppMaybeRef<TCon, T, RefT>
where
    TCon: WithTypeArg<T> + ?Sized,
    T: ?Sized,
    RefT: ?Sized,
{
}

impl<TCon, T, TCollection> TypeAppMaybeRef<TCon, T, Val> for TCollection
where
    TCollection: TypeApp<TCon, T>,
    TCon: WithTypeArg<T> + ?Sized,
    T: ?Sized,
{
}

impl<TCon, T, TCollection> TypeAppMaybeRef<TCon, T, Ref> for &TCollection
where
    TCollection: TypeApp<TCon, T>,
    TCon: WithTypeArg<T> + ?Sized,
    T: ?Sized,
{
}