syntax_data: {"ast_node_type":"other","tokens":[{"end":72,"kind":"keyword","start":0,"text":"ty::Alias(ty::Opaque,"}]}
source_snippet:             ty::Alias(ty::Opaque, ty::AliasTy { def_id, args, .. }) => {
context_after:                 if self.infcx.can_define_opaque_ty(def_id) {