auto_enums 0.7.5

A library for to allow multiple return types by automatically generated enum.
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
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
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259

# auto_enums

[![crates-badge]][crates-url]
[![docs-badge]][docs-url]
[![license-badge]][license]
[![rustc-badge]][rustc-url]

[crates-badge]: https://img.shields.io/crates/v/auto_enums.svg
[crates-url]: https://crates.io/crates/auto_enums
[docs-badge]: https://docs.rs/auto_enums/badge.svg
[docs-url]: https://docs.rs/auto_enums
[license-badge]: https://img.shields.io/badge/license-Apache--2.0%20OR%20MIT-blue.svg
[license]: #license
[rustc-badge]: https://img.shields.io/badge/rustc-1.31+-lightgray.svg
[rustc-url]: https://blog.rust-lang.org/2018/12/06/Rust-1.31-and-rust-2018.html

A library for to allow multiple return types by automatically generated enum.

This crate is a procedural macro implementation of the features discussions in <https://github.com/rust-lang/rfcs/issues/2414>.

This library provides the following attribute macros:

* `#[auto_enum]`

  Parses syntax, creates the enum, inserts variants, and passes specified traits to `#[enum_derive]`.

* `#[enum_derive]`

  Implements specified traits to the enum.

## Usage

Add this to your `Cargo.toml`:

```toml
[dependencies]
auto_enums = "0.7"
```

The current auto_enums requires Rust 1.31 or later.

## Examples

`#[auto_enum]`'s basic feature is to wrap the value returned by the obvious branches (`match`, `if`, `return`, etc..) by an enum that implemented the specified traits.

```rust
use auto_enums::auto_enum;

#[auto_enum(Iterator)]
fn foo(x: i32) -> impl Iterator<Item = i32> {
    match x {
        0 => 1..10,
        _ => vec![5, 10].into_iter(),
    }
}
```

`#[auto_enum]` generates code in two stages.

First, `#[auto_enum]` will do the following.

* parses syntax
* creates the enum
* inserts variants

Code like this will be generated:

```rust
fn foo(x: i32) -> impl Iterator<Item = i32> {
    #[::auto_enums::enum_derive(Iterator)]
    enum __Enum1<__T1, __T2> {
        __T1(__T1),
        __T2(__T2),
    }

    match x {
        0 => __Enum1::__T1(1..10),
        _ => __Enum1::__T2(vec![5, 10].into_iter()),
    }
}
```

Next, `#[enum_derive]` implements the specified traits.

[Code like this will be generated](docs/example-1.md)

`#[auto_enum]` can also parse nested arms/branches by using the `#[nested]` attribute.

```rust
use auto_enums::auto_enum;
#[auto_enum(Iterator)]
fn foo(x: i32) -> impl Iterator<Item = i32> {
    match x {
        0 => 1..10,
        #[nested]
        _ => match x {
            1 => vec![5, 10].into_iter(),
            _ => 0..=x,
        },
    }
}
```

See [API Documentation][docs-url] for more details.

## Supported traits

`#[enum_derive]` implements the supported traits and passes unsupported traits to `#[derive]`.

If you want to use traits that are not supported by `#[enum_derive]`, you can use another crate that provides `proc_macro_derive`, or you can define `proc_macro_derive` yourself ([derive_utils] probably can help it).

Basic usage of `#[enum_derive]`

```rust
use auto_enums::enum_derive;

// `#[enum_derive]` implements `Iterator`, and `#[derive]` implements `Clone`.
#[enum_derive(Iterator, Clone)]
enum Foo<A, B> {
    A(A),
    B(B),
}
```

### [std|core] libraries

Some traits support is disabled by default.
Note that some traits have aliases.

*When using features that depend on unstable APIs, the `"unstable"` feature must be explicitly enabled*

`[std|core]::iter`

* [`Iterator`](https://doc.rust-lang.org/std/iter/trait.Iterator.html) - [generated code](docs/supported_traits/std/iter/iterator.md)
* [`DoubleEndedIterator`](https://doc.rust-lang.org/std/iter/trait.DoubleEndedIterator.html) - [generated code](docs/supported_traits/std/iter/DoubleEndedIterator.md)
* [`ExactSizeIterator`](https://doc.rust-lang.org/std/iter/trait.ExactSizeIterator.html) - [generated code](docs/supported_traits/std/iter/ExactSizeIterator.md)
* [`FusedIterator`](https://doc.rust-lang.org/std/iter/trait.FusedIterator.html) - [generated code](docs/supported_traits/std/iter/FusedIterator.md)
* [`Extend`](https://doc.rust-lang.org/std/iter/trait.Extend.html) - [generated code](docs/supported_traits/std/iter/extend.md)
* [`TrustedLen`](https://doc.rust-lang.org/std/iter/trait.TrustedLen.html) - [generated code](docs/supported_traits/std/iter/TrustedLen.md) *(requires `"trusted_len"` and `"unstable"` crate features)*

*See also [iter-enum] crate.*

`[std|core]::future`

* [`Future`](https://doc.rust-lang.org/nightly/std/future/trait.Future.html) - [generated code](docs/supported_traits/std/future.md)

*See also [futures-enum] crate.*

`std::io`

* [`Read`](https://doc.rust-lang.org/std/io/trait.Read.html) (alias: `io::Read`) - [generated code](docs/supported_traits/std/io/read.md)
* [`BufRead`](https://doc.rust-lang.org/std/io/trait.BufRead.html) (alias: `io::BufRead`) - [generated code](docs/supported_traits/std/io/BufRead.md)
* [`Write`](https://doc.rust-lang.org/std/io/trait.Write.html) (alias: `io::Write`) - [generated code](docs/supported_traits/std/io/write.md)
* [`Seek`](https://doc.rust-lang.org/std/io/trait.Seek.html) (alias: `io::Seek`) - [generated code](docs/supported_traits/std/io/seek.md)

*See also [io-enum] crate.*

`[std|core]::ops`

* [`Deref`](https://doc.rust-lang.org/std/ops/trait.Deref.html) *(requires `"ops"` crate feature)*
* [`DerefMut`](https://doc.rust-lang.org/std/ops/trait.DerefMut.html) *(requires `"ops"` crate feature)*
* [`Index`](https://doc.rust-lang.org/std/ops/trait.Index.html) *(requires `"ops"` crate feature)*
* [`IndexMut`](https://doc.rust-lang.org/std/ops/trait.IndexMut.html) *(requires `"ops"` crate feature)*
* [`RangeBounds`](https://doc.rust-lang.org/std/ops/trait.RangeBounds.html) *(requires `"ops"` crate feature)*
* [`Fn`](https://doc.rust-lang.org/std/ops/trait.Fn.html) *(requires `"fn_traits"` and `"unstable"` crate features)*
* [`FnMut`](https://doc.rust-lang.org/std/ops/trait.FnMut.html) *(requires `"fn_traits"` and `"unstable"` crate features)*
* [`FnOnce`](https://doc.rust-lang.org/std/ops/trait.FnOnce.html) *(requires `"fn_traits"` and `"unstable"` crate features)*
* [`Generator`](https://doc.rust-lang.org/nightly/std/ops/trait.Generator.html) *(requires `"generator_trait"` and `"unstable"` crate features)*

`[std|core]::convert`

* [`AsRef`](https://doc.rust-lang.org/std/convert/trait.AsRef.html) *(requires `"convert"` crate feature)*
* [`AsMut`](https://doc.rust-lang.org/std/convert/trait.AsMut.html) *(requires `"convert"` crate feature)*

`[std|core]::fmt`

* [`Debug`](https://doc.rust-lang.org/std/fmt/trait.Debug.html) (alias: `fmt::Debug`) - [generated code](docs/supported_traits/std/debug.md)
* [`Display`](https://doc.rust-lang.org/std/fmt/trait.Display.html) (alias: `fmt::Display`)
* [`fmt::Binary`](https://doc.rust-lang.org/std/fmt/trait.Binary.html) *(requires `"fmt"` crate feature)*
* [`fmt::LowerExp`](https://doc.rust-lang.org/std/fmt/trait.LowerExp.html) *(requires `"fmt"` crate feature)*
* [`fmt::LowerHex`](https://doc.rust-lang.org/std/fmt/trait.LowerHex.html) *(requires `"fmt"` crate feature)*
* [`fmt::Octal`](https://doc.rust-lang.org/std/fmt/trait.Octal.html) *(requires `"fmt"` crate feature)*
* [`fmt::Pointer`](https://doc.rust-lang.org/std/fmt/trait.Pointer.html) *(requires `"fmt"` crate feature)*
* [`fmt::UpperExp`](https://doc.rust-lang.org/std/fmt/trait.UpperExp.html) *(requires `"fmt"` crate feature)*
* [`fmt::UpperHex`](https://doc.rust-lang.org/std/fmt/trait.UpperHex.html) *(requires `"fmt"` crate feature)*
* [`fmt::Write`](https://doc.rust-lang.org/std/fmt/trait.Write.html)

`std::error`

* [`Error`](https://doc.rust-lang.org/std/error/trait.Error.html) - [generated code](docs/supported_traits/std/error.md)

### External libraries

You can add support for external library by activating the each crate feature.

[`futures(v0.3)`](https://github.com/rust-lang/futures-rs) *(requires `"futures03"` or `"futures"` crate feature)*

* [`futures::Stream`](https://docs.rs/futures/0.3/futures/stream/trait.Stream.html) - [generated code](docs/supported_traits/external/futures/stream.md)
* [`futures::Sink`](https://docs.rs/futures/0.3/futures/sink/trait.Sink.html) - [generated code](docs/supported_traits/external/futures/sink.md)
* [`futures::AsyncRead`](https://docs.rs/futures/0.3/futures/io/trait.AsyncRead.html) - [generated code](docs/supported_traits/external/futures/AsyncRead.md)
* [`futures::AsyncWrite`](https://docs.rs/futures/0.3/futures/io/trait.AsyncWrite.html) - [generated code](docs/supported_traits/external/futures/AsyncWrite.md)
* [`futures::AsyncSeek`](https://docs.rs/futures/0.3/futures/io/trait.AsyncSeek.html) - [generated code](docs/supported_traits/external/futures/AsyncSeek.md)
* [`futures::AsyncBufRead`](https://docs.rs/futures/0.3/futures/io/trait.AsyncBufRead.html) - [generated code](docs/supported_traits/external/futures/AsyncBufRead.md)

*See also [futures-enum] crate.*

[`futures(v0.1)`](https://github.com/rust-lang/futures-rs/tree/0.1) *(requires `"futures01"` crate feature)*

* [`futures01::Future`](https://docs.rs/futures/0.1/futures/future/trait.Future.html)
* [`futures01::Stream`](https://docs.rs/futures/0.1/futures/stream/trait.Stream.html)
* [`futures01::Sink`](https://docs.rs/futures/0.1/futures/sink/trait.Sink.html)

[`rayon`](https://github.com/rayon-rs/rayon) *(requires `"rayon"` crate feature)*

* [`rayon::ParallelIterator`](https://docs.rs/rayon/1/rayon/iter/trait.ParallelIterator.html) - [generated code](docs/supported_traits/external/rayon/ParallelIterator.md)
* [`rayon::IndexedParallelIterator`](https://docs.rs/rayon/1/rayon/iter/trait.IndexedParallelIterator.html) - [generated code](docs/supported_traits/external/rayon/IndexedParallelIterator.md)
* [`rayon::ParallelExtend`](https://docs.rs/rayon/1/rayon/iter/trait.ParallelExtend.html) - [generated code](docs/supported_traits/external/rayon/ParallelExtend.md)

[`serde`](https://github.com/serde-rs/serde) *(requires `"serde"` crate feature)*

* [`serde::Serialize`](https://docs.serde.rs/serde/trait.Serialize.html) - [generated code](docs/supported_traits/external/serde/serialize.md)

[`tokio(v0.2)`](https://github.com/tokio-rs/tokio) *(requires `"tokio02"` crate feature)*

* [`tokio02::AsyncRead`](https://docs.rs/tokio/0.2/tokio/io/trait.AsyncRead.html)
* [`tokio02::AsyncWrite`](https://docs.rs/tokio/0.2/tokio/io/trait.AsyncWrite.html)
* [`tokio02::AsyncSeek`](https://docs.rs/tokio/0.2/tokio/io/trait.AsyncSeek.html)
* [`tokio02::AsyncBufRead`](https://docs.rs/tokio/0.2/tokio/io/trait.AsyncBufRead.html)

[`tokio(v0.1)`](https://github.com/tokio-rs/tokio/tree/v0.1.x) *(requires `"tokio01"` crate feature)*

* [`tokio01::AsyncRead`](https://docs.rs/tokio/0.1/tokio/io/trait.AsyncRead.html)
* [`tokio01::AsyncWrite`](https://docs.rs/tokio/0.1/tokio/io/trait.AsyncWrite.html)

## Related Projects

* [derive_utils]: A procedural macro helper for easily writing [derives macros][proc-macro-derive] for enums.
* [futures-enum]: \#\[derive(Future, Stream, Sink, AsyncRead, AsyncWrite, AsyncSeek, AsyncBufRead)\] for enums.
* [io-enum]: \#\[derive(Read, Write, Seek, BufRead)\] for enums.
* [iter-enum]: \#\[derive(Iterator, DoubleEndedIterator, ExactSizeIterator, Extend)\] for enums.

[derive_utils]: https://github.com/taiki-e/derive_utils
[futures-enum]: https://github.com/taiki-e/futures-enum
[io-enum]: https://github.com/taiki-e/io-enum
[iter-enum]: https://github.com/taiki-e/iter-enum
[proc-macro-derive]: https://doc.rust-lang.org/reference/procedural-macros.html#derive-macros

## License

Licensed under either of

* Apache License, Version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or <http://www.apache.org/licenses/LICENSE-2.0>)
* MIT license ([LICENSE-MIT](LICENSE-MIT) or <http://opensource.org/licenses/MIT>)

at your option.

### Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.