auto_enums

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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:

Usage

Add this to your Cargo.toml:

toml [dependencies] auto_enums = "0.6.0-alpha.1"

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 autoenums::autoenum;

[auto_enum(Iterator)]

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

#[auto_enum] generates code in two stages.

First, #[auto_enum] will do the following.

Code like this will be generated:

```rust fn foo(x: i32) -> impl Iterator { #[::autoenums::enumderive(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

See API Documentation 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 autoenums::enumderive;

// #[enum_derive] implements Iterator, and #[derive] implements Clone.

[enum_derive(Iterator, Clone)]

enum Foo { A(A), B(B), } ```

[std|core] libraries

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

[std|core]::iter

[std|core]::future

std::io

[std|core]::ops

[std|core]::convert

[std|core]::fmt

std::error

External libraries

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

futures(v0.3) (requires "futures" crate feature)

futures(v0.1) (requires "futures01" crate feature)

quote (requires "proc_macro" crate feature)

rayon (requires "rayon" crate feature)

serde (requires "serde" crate feature)

License

Licensed under either of

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.