syntax_data: {"ast_node_type":"variable","tokens":[{"end":88,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:     let mut selcx = SelectionContext::with_query_mode(infcx, TraitQueryMode::Canonical);
context_after:     let obligation = Obligation::new(tcx, ObligationCause::dummy(), param_env, predicate);