Future incompatibility report: Future breakage diagnostic: warning: use of unstable library feature 'rustc_encodable_decodable': derive macro for `rustc-serialize`; should not be used in new code --> $DIR/rustc-decodable-issue-123156.rs:10:10 | LL | #[derive(RustcDecodable)] | ^^^^^^^^^^^^^^ | = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release! = note: for more information, see issue #64266