syntax_data: {"ast_node_type":"other","tokens":[{"end":78,"kind":"keyword","start":0,"text":"///"}]}
source_snippet:     /// Returns the "principal `DefId`" of this set of existential predicates.
context_before: impl<'tcx> ty::List<ty::PolyExistentialPredicate<'tcx>> {
context_after:     ///