{"ast_node_type":"function","tokens":[{"end":55,"kind":"keyword","start":0,"text":"fn"}]}
    fn encode(&self, s: &mut EncodeContext<'a, 'tcx>) {
impl<'a, 'tcx> Encodable<EncodeContext<'a, 'tcx>> for ExpnIndex {
        s.emit_u32(self.as_u32());