syntax_data: {"ast_node_type":"variable","tokens":[{"end":68,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:             let mut obligations = self.collect_predicates_for_types(
context_before:             let cause = obligation.derived_cause(ObligationCauseCode::BuiltinDerived);
context_after:                 obligation.param_env,