impl-trait-utils

Utilities for working with impl traits in Rust.

make_variant

make_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_variant(SendIntFactory: Send)]
trait IntFactory {
    async fn make(&self) -> i32;
    // ..or..
    fn stream(&self) -> impl Iterator<Item = i32>;
    fn call(&self) -> u32;
}

Which creates a new SendIntFactory: IntFactory + Send trait and additionally bounds SendIntFactory::make(): Send and SendIntFactory::stream(): Send. Ordinary methods are not affected.

Implementers of the trait can choose to implement the variant instead of the original trait. The macro creates a blanket impl which ensures that any type which implements the variant also implements the original trait.

trait_transformer

trait_transformer does the same thing as make_variant, but using experimental nightly-only syntax that depends on the return_type_notation feature. It may be used to experiment with new kinds of trait transformations in the future.

License and usage notes

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