half-finish backend macro

i cannot figure out how procedural macros work actually

src/backend/macros.rs

@@ -42,39 +42,6 @@ macro_rules! impl_backend_constants {
     };
 }
 
-// #[macro_export]
-// macro_rules! register_backends {
-//     ($first:ident, $($name:ident),*) => {
-//         #[derive(Debug, Hash, PartialEq, Eq)]
-//         pub(crate) enum Backends {
-//             $first,
-//             $(
-//                 $name,
-//             )*
-//         }
-//
-//         impl Backends {
-//             pub fn iter() -> BackendIter {
-//                 BackendIter {
-//                     next: Some(Backends::$first),
-//                 }
-//             }
-//             fn next(&self) -> Option<Self> {
-//                 match self {
-//                     $(
-//                         Self::$name => match $name {
-//                             $(
-//                                 _ => Some(Self::$name),
-//                             )*
-//                             _ => None
-//                         },
-//                     )*
-//                 }
-//             }
-//         }
-//     }
-// }
-
 #[macro_export]
 macro_rules! register_backends {
     ($first:ident, $($name:ident),*) => {
@@ -93,14 +60,6 @@ macro_rules! register_backends {
                 }
             }
 
-            fn next(&self) -> Option<Self> {
-                println!("Some({:?})", Self::$first);
-                $(
-                    println!("{:?}", Self::$name);
-                 )*
-                None
-            }
-
             fn get_backend(&self) -> Box<dyn Backend> {
                 match self {
                     Self::$first => Box::new($first::new()),