impl From variadic like :D

playground.rs

#[derive(Debug)]
struct CM {
    id: i32,
    topic_id: i32,
}

#[derive(Debug)]
struct TM {
    id: i32,
}

#[derive(Debug)]
struct RM {
    id: i32,
}

#[derive(Debug)]
struct Count(i32);

#[derive(Default, Debug)]
struct Cluster {
    id: i32,
    topic: Option<Topic>,
    count: Option<i32>,
    resource: Option<Resource>
}

#[derive(Default, Debug)]
struct Topic {
    id: i32,
}

#[derive(Default, Debug)]
struct Resource {
    id: i32,
}

impl From<CM> for Cluster {
    fn from(cluster: CM) -> Self {
        Self {
            id: cluster.id,
            ..Default::default()
        }
    }
}

impl From<TM> for Topic {
    fn from(topic: TM) -> Self {
        Self {
            id: topic.id,
        }
    }
}

impl From<RM> for Resource {
    fn from(resource: RM) -> Self {
        Self {
            id: resource.id,
        }
    }
}
 
impl<T> From<(T, TM)> for Cluster
where
    T: Into<Cluster>
{
    fn from(data: (T, TM)) -> Self {
        let (base, topic) = data;
        Self {
            topic: Some(Topic::from(topic)),
            ..base.into()
        }
    }
}

impl<T> From<(T, Count)> for Cluster
where
    T: Into<Cluster>
{
    fn from(data: (T, Count)) -> Self {
        let (base, count) = data;
        Self {
            count: Some(count.0),
            ..base.into()
        }
    }
}

impl<T> From<(T, RM)> for Cluster
where
    T: Into<Cluster>
{
    fn from(data: (T, RM)) -> Self {
        let (base, resource) = data;
        Self {
            resource: Some(Resource::from(resource)),
            ..base.into()
        }
    }
}

macro_rules! paired {
    ($base:expr,) => ($base);
    ($base:expr, $other:expr,) => (($base, $other));
    ($base:expr, $other:expr, $($tail:expr,)+) => (
        (paired!(($base, $other), $($tail,)+))
    );
}

macro_rules! tpaired {
    ($base:ty,) => ($base);
    ($base:ty, $other:ty,) => (($base, $other));
    ($base:ty, $other:ty, $($tail:ty,)+) => (
        tpaired!(($base, $other), $($tail,)+)
    );
}

macro_rules! peel {
    ($name:ident, $($other:ident,)*) => (impl_paired! { $($other,)* })
}

macro_rules! impl_paired {
    () => ();
    ( $($name:ident,)+ ) => (
        impl<$($name),+> Paired for ($($name,)+) {
            type Output = tpaired!($($name,)+);
            
            #[allow(non_snake_case, unused_assignments)]
            fn paired(self) -> Self::Output {
                let ($($name,)+) = self;
                paired!($($name,)+)
            }
        }
        peel! { $($name,)+ }
    )
}

impl_paired! { T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, }

trait Paired {
    type Output;
    
    fn paired(self) -> Self::Output;
}

/*impl<T1, T2, T3> Paired for (T1, T2, T3) {
    type Output = tpaired!(T1, T2, T3,);
    
    #[allow(non_snake_case, unused_assignments)]
    fn paired(self) -> Self::Output {
        let (T1, T2, T3) = self;
        paired!(T1, T2, T3)
    }
}

impl<T1, T2, T3, T4> Paired for (T1, T2, T3, T4) {
    type Output = tpaired!(T1, T2, T3, T4,);
    
    fn paired(self) -> Self::Output {
        paired!(self.0, self.1, self.2, self.3)
    }
}*/


fn main() {
    let t = (4, 5, "t");
    dbg!(t.paired());

    /*dbg!(paired!(1));
    dbg!(paired!(1, 2));
    dbg!(paired!(1, 2, 3, 4));*/
    /* 
    let c = CM { id: 42, topic_id: 28 };
    let cluster = Cluster::from(paired!(c));
    dbg!(cluster);
    
    let c = CM { id: 42, topic_id: 28 };
    let t = TM { id: 142 };
    let cluster = Cluster::from(paired!(c, t));
    dbg!(cluster);
    
    let c = CM { id: 42, topic_id: 28 };
    let cnt = Count(28);
    let cluster = Cluster::from(paired!(c, cnt));
    dbg!(cluster);
    
    let c = CM { id: 42, topic_id: 28 };
    let t = TM { id: 142 };
    let cnt = Count(28);
    let cluster = Cluster::from(paired!(c, t, cnt));
    dbg!(cluster);
    */
    
    // let t = (42, "42", 'x', 4, 5, 6, 7, 8, 9, 10, 11, 12, 13);
    // dbg!(tup!(t));
    
    let c = CM { id: 42, topic_id: 28 };
    let t = TM { id: 142 };
    let r = RM { id: 128 };
    let cnt = Count(28);
    // let cluster = Cluster::from((((c, t), r), cnt));
    let tp = (c, cnt, r, t);
    //let l = paired!(tp.0, tp.1, tp.2, tp.3);
    // let l = paired!(tp);
    // let (c2, cnt2, r2, t2) = tp;
    // let l = paired!(c2, cnt2, t2, r2);
    // dbg!(&l);
    let cluster = Cluster::from(tp.paired());
    dbg!(cluster);
    
    let test = (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11);
    assert_eq!(test.paired(), 
        ((((((((((1, 2), 3), 4), 5), 6), 7), 8), 9), 10), 11));
}