#![feature(generators, generator_trait)]
use std::ops::{Generator, GeneratorState};

macro_rules! yield_from {

    ($g:expr) => (
        unsafe {
            loop {
                match $g.resume() {
                    GeneratorState::Yielded(y) => yield y,
                    GeneratorState::Complete(ret) => break ret,
                }
            }
        }
    );
}


fn generate() -> impl Generator<Yield = u8, Return = u8>  {
    || {
        yield_from!(|| {
            for i in 0..5u8 {
                yield i;
            }
        });
        return 99
    }
}

fn main() {
    crash();
}

fn generate_without_compiler_error() -> impl Generator<Yield = u8, Return = u8> {
    || {
        let mut inner = || {
            for i in 0..5u8 {
                yield i;
            }
        };

        yield_from!(inner);
        return 99
    }
}