syntax_data: {"ast_node_type":"other","tokens":[{"end":60,"kind":"keyword","start":0,"text":"if"}]}
source_snippet:                 if self.infcx.can_define_opaque_ty(def_id) {
context_before:             ty::Alias(ty::Opaque, ty::AliasTy { def_id, args, .. }) => {
context_after:                     unreachable!()