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
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157

#![doc = include_str!("../README.md")]

use std::{any::TypeId, marker::PhantomData};

/// Sets of types from 0 to 10 elements.
pub mod sets;

/// Indicates that a set contains element `E`.
pub trait Contains<E> {}
impl<T: ?Sized, E> Contains<E> for Set<T> where T: Contains<E> {}

/// Trait to get the members (type-ids) of a set.
pub trait Members {
    /// Get the members (type-ids) of this set.
    fn members() -> &'static [TypeId];
}

/// Implemented if set is a subset of `S`.
pub trait SubsetOf<S> {}

/// Implemented if set is a superset of `S`.
pub trait SupersetOf<S> {}
impl<T, S> SupersetOf<S> for T where S: SubsetOf<T> {}

/// Trait that allows usage of custom types as a set.
pub trait AsSet {
    /// The [`struct@Set`] type.
    type Set: Members;
}

impl<T, S> SubsetOf<S> for T
where
    T: AsSet,
    T::Set: SubsetOf<S>,
{
}

impl<T, E> Contains<E> for T
where
    T: AsSet,
    T::Set: Contains<E>,
{
}

impl<T> Members for T
where
    T: AsSet,
{
    fn members() -> &'static [TypeId] {
        <T::Set as Members>::members()
    }
}

/// Marker struct to act as a set of elements.
///
/// Usually created using the [`macro@Set`] macro.
///
/// The inner type `T` is usually one of the [`sets`]:
/// - `Set![]` == `Set<dyn Zero>`
/// - `Set![u32]` == `Set<dyn One<u32>>`
/// - `Set![u32, u64]` == `Set<dyn Two<u32, u64>>`
pub struct Set<T: ?Sized>(PhantomData<fn() -> T>);

/// Create a [`struct@Set`] from a list of types.
///
/// Example:
/// - `Set![]` == `Set<dyn Zero>`
/// - `Set![u32]` == `Set<dyn One<u32>>`
/// - `Set![u32, u64]` == `Set<dyn Two<u32, u64>>`
#[macro_export]
macro_rules! Set {
    ($(,)?) => {
        $crate::Set<dyn $crate::sets::Zero>
    };
    ($t1:ty $(,)?) => {
        $crate::Set<dyn $crate::sets::One<$t1>>
    };
    ($t1:ty, $t2:ty $(,)?) => {
        $crate::Set<dyn $crate::sets::Two<$t1, $t2>>
    };
    ($t1:ty, $t2:ty, $t3:ty $(,)?) => {
        $crate::Set<dyn $crate::sets::Three<$t1, $t2, $t3>>
    };
    ($t1:ty, $t2:ty, $t3:ty, $t4:ty $(,)?) => {
        $crate::Set<dyn $crate::sets::Four<$t1, $t2, $t3, $t4>>
    };
    ($t1:ty, $t2:ty, $t3:ty, $t4:ty, $t5:ty $(,)?) => {
        $crate::Set<dyn $crate::sets::Five<$t1, $t2, $t3, $t4, $t5>>
    };
    ($t1:ty, $t2:ty, $t3:ty, $t4:ty, $t5:ty, $t6:ty $(,)?) => {
        $crate::Set<dyn $crate::sets::Six<$t1, $t2, $t3, $t4, $t5, $t6>>
    };
    ($t1:ty, $t2:ty, $t3:ty, $t4:ty, $t5:ty, $t6:ty, $t7:ty $(,)?) => {
        $crate::Set<dyn $crate::sets::Seven<$t1, $t2, $t3, $t4, $t5, $t6, $t7>>
    };
    ($t1:ty, $t2:ty, $t3:ty, $t4:ty, $t5:ty, $t6:ty, $t7:ty, $t8:ty $(,)?) => {
        $crate::Set<dyn $crate::sets::Eight<$t1, $t2, $t3, $t4, $t5, $t6, $t7, $t8>>
    };
    ($t1:ty, $t2:ty, $t3:ty, $t4:ty, $t5:ty, $t6:ty, $t7:ty, $t8:ty, $t9:ty $(,)?) => {
        $crate::Set<dyn $crate::sets::Nine<$t1, $t2, $t3, $t4, $t5, $t6, $t7, $t8, $t9>>
    };
    ($t1:ty, $t2:ty, $t3:ty, $t4:ty, $t5:ty, $t6:ty, $t7:ty, $t8:ty, $t9:ty, $t10:ty $(,)?) => {
        $crate::Set<dyn $crate::sets::Ten<$t1, $t2, $t3, $t4, $t5, $t6, $t7, $t8, $t9, $t10>>
    };
}

#[cfg(test)]
mod tests {
    use super::*;

    struct MySet;

    impl AsSet for MySet {
        type Set = Set![u32, u64];
    }

    #[test]
    fn test() {
        is_subset::<Set![u32, u64, u32, u32]>();
        is_subset::<Set![u32]>();
        is_subset::<Set![u64]>();
        is_subset2::<Set![]>();
        is_subset::<MySet>();
        // is_subset2::<MySet>(); // does not compile
        // is_subset::<Set![u32, u64, u128]>(); // does not compile

        is_superset1::<Set![u32, u64]>();
        is_superset2::<Set![u32, u64, u128]>();
        is_superset1::<MySet>();
        // is_superset1::<Set![u32]>(); // does not compile
        // is_superset2::<MySet>(); // does not compile
    }

    fn is_subset<T>()
    where
        T: SubsetOf<Set![u32, u64]>,
    {
    }

    fn is_subset2<T>()
    where
        T: SubsetOf<Set![u32]>,
    {
    }

    fn is_superset1<T>()
    where
        T: SupersetOf<Set![u32, u64]>,
    {
    }

    fn is_superset2<T>()
    where
        T: SupersetOf<Set![u32, u64, u128]>,
    {
    }
}