syntax_data: {"ast_node_type":"variable","tokens":[{"end":77,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:     let ParamEnvAnd { param_env, value: ProvePredicate { predicate } } = key;
context_before: ) {
context_after:     ocx.register_obligation(Obligation::new(ocx.infcx.tcx, cause, param_env, predicate));