syntax_data: {"ast_node_type":"other","tokens":[{"end":15,"kind":"keyword","start":0,"text":"self[0]"}]}
source_snippet:         self[0]
context_before:     pub fn principal(&self) -> Option<ty::Binder<'tcx, ExistentialTraitRef<'tcx>>> {
context_after:             .map_bound(|this| match this {