Attempt to add optional rustc-serialize

Fails because of rust-lang/rust#22250

Cargo.toml

@@ -11,3 +11,4 @@ description = "[incomplete yet] Matroska (mkv,webm) files parser and generator i
 [dependencies]
 byteorder = "0.3.5"
 log = "0.3"
+rustc-serialize = { version = "0.3", optional = true }

src/elements/database.rs

@@ -1,13 +1,17 @@
 use super::Type::*;
 
+
 macro_rules! elements_database {
     ($($cl:ident $t:ident $id:expr),*,) => {
         #[derive(Debug,Eq,PartialEq,Copy,Ord,PartialOrd,Clone)]
+        // XXX https://github.com/rust-lang/rust/issues/22250
+        #[cfg_attr(feature = "rustc-serialize", derive(RustcEncodable, RustcDecodable))]
         pub enum Class {
             $($cl),*
             ,Unknown
         }
 
+
         pub fn id_to_class(id:u64) -> Class {
             use self::Class::*;
 

src/elements/mod.rs

@@ -23,6 +23,7 @@ pub enum Type {
 // Element DOM
 
 #[derive(PartialEq,Debug,PartialOrd,Clone)]
+#[cfg_attr(feature = "rustc-serialize", derive(RustcEncodable, RustcDecodable))]
 pub enum ElementContent {
     Master(Vec<Rc<Element>>),
     Unsigned(u64),
@@ -35,6 +36,7 @@ pub enum ElementContent {
 }
 
 #[derive(PartialEq,Debug,PartialOrd,Clone)]
+#[cfg_attr(feature = "rustc-serialize", derive(RustcEncodable, RustcDecodable))]
 pub struct Element {
     class : database::Class,
     content : ElementContent,

src/lib.rs

@@ -11,9 +11,12 @@
 #![feature(slice_patterns)]
 #![feature(vec_push_all)]
 #![feature(append)]
+#![cfg_attr(feature = "rustc-serialize", feature(custom_derive))]
 
 
 #[macro_use]
 extern crate log;
 
+#[cfg(feature = "rustc-serialize")] extern crate rustc_serialize;
+
 pub mod elements;