Attribute Macro generator 

#[generator]

Declare a standalone generator function.

This attribute macro transforms a function definition into a generator definition.

Parameters

• yield - The type that will be yielded from the generator. If not specified then () will be used instead.
• arg - The type of the argument that will be passed to the generator via resume. This can be accessed via the argument! and r#yield! macros within the generator.
• crate - A path at which the fauxgen crate can be accessed. If not specified then it will use ::fauxgen.

Interface

This attribute macro creates two regular macros that can only be used inside the generator definition itself:

r#yield!

This is the equivalent of the yield keyword. It takes a value to yield to the caller and returns the argument that was passed in on resume.

use fauxgen::{Generator, GeneratorState};

#[fauxgen::generator(yield = &'static str, arg = &'static str)]
fn example() -> &'static str {
    r#yield!("test")
}

let mut gen = std::pin::pin!(example());
assert!(matches!(gen.as_mut().resume("ignored"), GeneratorState::Yielded("test")));
assert!(matches!(gen.as_mut().resume("another"), GeneratorState::Complete("another")));

Note, however, that the first argument passed into the generator is ignored. In order to extract the first argument we need to use the argument! macro.

argument!

This macro extracts the argument passed to the very first resume call, the one that started the generator. It is only valid to call before the first yield, doing so after will result in a panic.

#[fauxgen::generator(arg = &'static str)]
fn example() {
    let first = argument!();
    let second = r#yield!();
    let third = r#yield!();
}

Using the yield keyword

This macro supports using the yield keyword in place of the r#yield! macro. Note that the keyword itself is unstable in rust and to just use it you will need to enable the nightly generators feature.

#![feature(coroutines)]

#[fauxgen::generator(yield = &'static str)]
fn generator() {
    yield "first";
    yield "second";
    yield "third";
}