syntax_data: {"ast_node_type":"variable","tokens":[{"end":83,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:         let hi = lower_endpoint(hi_expr)?.unwrap_or(PatRangeBoundary::PosInfinity);
context_before:         let lo = lower_endpoint(lo_expr)?.unwrap_or(PatRangeBoundary::NegInfinity);