syntax_data: {"ast_node_type":"other","tokens":[{"end":45,"kind":"keyword","start":0,"text":"match"}]}
source_snippet:                 match self.ambient_variance {
context_before:             (ty::Infer(ty::TyVar(a_id)), ty::Infer(ty::TyVar(b_id))) => {
context_after:                     ty::Covariant => {