syntax_data: {"ast_node_type":"variable","tokens":[{"end":58,"kind":"keyword","start":0,"text":"while"}]}
source_snippet:         while let Some(pred) = self.base_iterator.next() {
context_before:     fn next(&mut self) -> Option<ty::Binder<I, ty::TraitRef<I>>> {
context_after:             if let Some(data) = pred.as_trait_clause() {