syntax_data: {"ast_node_type":"variable","tokens":[{"end":73,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:             let entry = self.provisional_cache.entry(input).or_default();
context_before:             debug_assert!(validate_cache.is_none(), "unexpected non-root: {input:?}");
context_after:             let EvaluationResult {