/// Represents some struct that holds references inside
#[derive(Debug)]
struct MyValue<'a> {
    number: &'a u32,
}

/// There are many structs similar to `MyValue` and there is a
/// trait common to them all that can create them.
impl<'a> From<&'a u32> for MyValue<'a> {
    fn from(value: &'a u32) -> Self {
        MyValue {
            number: value,
        }
    }
}

/// This produces objects that hold references into it. So the
/// object must be dropped first before any new one is made.
trait Producer<'a, T: 'a> {
    fn make(&'a mut self) -> T;
}

struct MyProducer<'a, T: 'a + From<&'a u32>> {
    number: u32,
    _phantom: std::marker::PhantomData<&'a T>,
}

impl<'a, T: 'a + From<&'a u32>> MyProducer<'a, T> {
    fn new() -> Self {
        Self {
            number: 0,
            _phantom: std::marker::PhantomData::default(),
        }
    }
}

impl<'a, T: From<&'a u32>> Producer<'a, T> for MyProducer<'a, T> {
    fn make(&'a mut self) -> T {
        self.number += 1;
        T::from(&self.number)
    }
}

fn main() {
    let mut producer = MyProducer::<MyValue>::new();

    println!("made this: {:?}", producer.make());
    println!("made this: {:?}", producer.make());
}