syntax_data: {"ast_node_type":"other","tokens":[{"end":88,"kind":"keyword","start":0,"text":"vars.push(ty::BoundVariableKind::Region(ty::BoundRegionKind::Anon));"}]}
source_snippet:                     vars.push(ty::BoundVariableKind::Region(ty::BoundRegionKind::Anon));
context_before:                     let var = ty::BoundVar::from_usize(vars.len());
context_after:                     ty::Region::new_bound(