syntax_data: {"ast_node_type":"variable","tokens":[{"end":75,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:         let mut buf = BorrowedBuf::from(Arc::get_mut(&mut bytes).unwrap());
context_before:         let mut bytes = Arc::new_uninit_slice(len as usize);
context_after:         match file.read_buf_exact(buf.unfilled()) {