syntax_data: {"ast_node_type":"variable","tokens":[{"end":49,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:     let cause = traits::ObligationCause::dummy();
context_before:     let ocx = traits::ObligationCtxt::new(&infcx);
context_after:     let param_env = tcx.param_env(impl_def_id);