Utilities for working with impl Traits in Rust.

Important

This fork of rust-lang/impl-trait-utils includes the merged PRs rust-lang#20 and rust-lang#30. Once these PRs are merged and the official release is available, you should switch to using that release.

trait_variant

trait_variant generates a specialized version of a base trait that uses async fn and/or -> impl Trait.

For example, if you want a Sendable version of your trait, you'd write:

#[trait_variant::make(IntFactory: Send)]
trait LocalIntFactory {
    async fn make(&self) -> i32;
    fn stream(&self) -> impl Iterator<Item = i32>;
    fn call(&self) -> u32;
}

The trait_variant::make would generate an additional trait called IntFactory:

use core::future::Future;

trait IntFactory: Send {
   fn make(&self) -> impl Future<Output = i32> + Send;
   fn stream(&self) -> impl Iterator<Item = i32> + Send;
   fn call(&self) -> u32;
}

Implementers can choose to implement either LocalIntFactory or IntFactory as appropriate.

If a non-Send variant of the trait is not needed, the name of the new variant can simply be omitted. E.g., this generates a single (rather than an additional) trait whose definition matches that in the expansion above:

#[trait_variant::make(Send)]
trait IntFactory {
    async fn make(&self) -> i32;
    fn stream(&self) -> impl Iterator<Item = i32>;
    fn call(&self) -> u32;
}

For more details, see the docs for trait_variant::make.

License and usage notes

Licensed under either of Apache License, Version 2.0 or MIT license at your option.