128     stack: Vec<(&'a Ast, Frame<'a>)>,
137 enum Frame<'a> {  enum
237                     if let Frame::Alternation { .. } = x {  in visit()
260     ) -> Result<Option<Frame<'a>>, V::Err> {  in induct()
266             Ast::Repetition(ref x) => Some(Frame::Repetition(x)),  in induct()
267             Ast::Group(ref x) => Some(Frame::Group(x)),  in induct()
270                 Some(Frame::Concat { head: &x.asts[0], tail: &x.asts[1..] })  in induct()
273             Ast::Alternation(ref x) => Some(Frame::Alternation {  in induct()
283     fn pop(&self, induct: Frame<'a>) -> Option<Frame<'a>> {  in pop()
285             Frame::Repetition(_) => None,  in pop()
286             Frame::Group(_) => None,  in pop()
287             Frame::Concat { tail, .. } => {  in pop()
291                     Some(Frame::Concat { head: &tail[0], tail: &tail[1..] })  in pop()
294             Frame::Alternation { tail, .. } => {  in pop()
298                     Some(Frame::Alternation {  in pop()
437 impl<'a> Frame<'a> {  impl
442             Frame::Repetition(rep) => &rep.ast,  in child()
443             Frame::Group(group) => &group.ast,  in child()
444             Frame::Concat { head, .. } => head,  in child()
445             Frame::Alternation { head, .. } => head,  in child()