Enum hierarchy through reflection

[danielopitz]

I wonder, is it possible to get names / values of enums given an enum hierarchy?

use facet::{Facet, Peek};

#[derive(Facet)]
#[repr(u8)]
enum A {
    EA(B),
}

#[derive(Facet)]
#[repr(u8)]
enum B {
    EB(C),
}

#[derive(Facet)]
#[repr(u8)]
enum C {
    EC
}

let x = A::EA(B::EB(C::EC)));
let peek = Peek::new(&x);

match peek {
    Peek::Enum(pe) => {
        let variant = pe.active_variant();
        println!("{}", variant.name);
        // how do I descdend further? I would like to get a vec in the end: ["A::EA", "B::EB", "C::EC"]
    }
}

[fasterthanlime]

Things are going to change in Facet Reflect, but you're looking for variant.fields which in turn has its own def.

[danielopitz]

Thanks a lot for the swift response! I can descend now in the hierarchy and see all of the variants of each enum, but is it possible to know which enum variant is selected?

Sorry if the questions are dumb, I'm quite the beginner in the Rust world and sometimes it's rather easy to miss things. Reflection works a little bit different in the programming languages I know, this doesn't make it easier!

Don't want to waste your time as well!

[danielopitz]

Here's the example I'm playing with:

use facet::Facet;
use facet_reflect::Peek;

#[derive(Facet)]
#[repr(u8)]
enum D {
    VD1,
    VD2,
    VD3,
}

#[derive(Facet)]
#[repr(u8)]
enum C {
    VC1,
}

#[derive(Facet)]
#[repr(u8)]
enum B {
    VB1(C),
    VB2(D),
}

#[derive(Facet)]
#[repr(u8)]
enum A {
    VA1(B),
}

fn main() {
    let e = A::VA1(B::VB2(D::VD3));

    let p = Peek::new(&e);
    match p {
        Peek::Enum(pe) => {
            let variant = pe.active_variant();

            println!("{}", variant.name);

            match variant.kind {
                facet::VariantKind::Tuple { fields } => {
                    for field in fields {
                        let d = field.shape.def;
                        println!("{:?}", d);
                    }
                }
                _ => todo!(),
            }
        }
        _ => todo!(),
    }
}

[fasterthanlime]

(See #188 for the facet-reflect changes — I'm sorry for the API churn, I'm trying to merge it as fast as I can to avoid a lot of people contributing on the old API. )

[danielopitz]

Thank you for the heads up! I don't mind API changes at all, will update when necessary! The library is <1.0.0 and it's a hard / difficult task as well.