disjoint_impls 1.3.8

Support for mutually disjoint impls
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
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

[![License: Apache 2.0](https://img.shields.io/badge/License-Apache%202.0-blue.svg)](https://github.com/mversic/disjoint_impls/blob/master/LICENSE)
[![Crates.io](https://img.shields.io/crates/v/disjoint_impls.svg)](https://crates.io/crates/disjoint_impls)

Crate will be maintained (at least) until [this idiom](https://github.com/rust-lang/rust/issues/20400) is allowed by the Rust compiler directly

## Description

Enables writing non-overlapping (*disjoint*) impls distinguished by a set of associated types.

Works for trait and inherent implementations alike (no special syntax).

### Trait implementations

```rs
use disjoint_impls::disjoint_impls;

pub trait Dispatch {
    type Group;
}

disjoint_impls! {
    pub trait Kita {}

    impl<T: Dispatch<Group = u32>> Kita for T {}
    impl<T: Dispatch<Group = i32>> Kita for T {}
}
```

### Inherent implementations

```rs
use disjoint_impls::disjoint_impls;

pub trait Dispatch {
    type Group;
}

struct Wrapper<T>(T);

disjoint_impls! {
    impl<T: Dispatch<Group = u32>> Wrapper<T> {}
    impl<T: Dispatch<Group = i32>> Wrapper<T> {}
}
```

### Foreign(remote) traits

For traits defined outside the current crate (a.k.a. foreign or remote traits), duplicate
the trait definition inside the macro and annotate it with `#[disjoint_impls(remote)]`.

```rs
use disjoint_impls::disjoint_impls;
// A foreign trait must be brought into scope so
// the `disjoint_impls!` macro can refer to it.
use remote_trait::ForeignKita;

pub trait Dispatch {
    type Group;
}

// (orphan rule): You can define blanket impls only
// for types that are defined in the current crate
pub struct LocalType<T>(T);

disjoint_impls! {
    #[disjoint_impls(remote)]
    pub trait ForeignKita {
        fn kita() {
            unreachable!("method is accessed through the original trait");
        }
    }

    impl<T: Dispatch<Group = u32>> ForeignKita for LocalType<T> {}
    impl<T: Dispatch<Group = i32>> ForeignKita for LocalType<T> {}
}
```

Other, much more complex examples, can be found in tests.