syntax_data: {"ast_node_type":"variable","tokens":[{"end":69,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:         let bound_vars = rustc_serialize::Decodable::decode(decoder);
context_before:     fn decode(decoder: &mut D) -> Self {
context_after:         UnsafeBinderInner(ty::Binder::bind_with_vars(