#![feature(generators, generator_trait)]

use std::{
    ops::{Generator, GeneratorState},
    pin::Pin,
};

fn firstn() -> impl Generator<Yield = u64, Return = ()> {
    static move || {
        let mut num = 0;
        let num = &mut num;

        yield *num;
        *num += 1; //~ ERROR dangling pointer was dereferenced
    }
}

struct GeneratorIteratorAdapter<G>(G);

impl<G> Iterator for GeneratorIteratorAdapter<G>
where
    G: Generator<Return = ()>,
{
    type Item = G::Yield;

    fn next(&mut self) -> Option<Self::Item> {
        let me = unsafe { Pin::new_unchecked(&mut self.0) };
        match me.resume() {
            GeneratorState::Yielded(x) => Some(x),
            GeneratorState::Complete(_) => None,
        }
    }
}

fn main() {
    let mut generator_iterator_2 = {
        let mut generator_iterator = GeneratorIteratorAdapter(firstn());
        generator_iterator.next(); // pin it

        generator_iterator // move it
    }; // *deallocate* generator_iterator

    generator_iterator_2.next(); // and use moved value
}