syntax_data: {"ast_node_type":"variable","tokens":[{"end":28,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:         let mut guar = None;
context_before:     fn check_miri_unleashed_features(&self) -> Option<ErrorGuaranteed> {
context_after:         let unleashed_features = self.miri_unleashed_features.lock();