syntax_data: {"ast_node_type":"other","tokens":[{"end":40,"kind":"keyword","start":0,"text":"assert_eq!(srcfbp1.pos,"}]}
source_snippet:     assert_eq!(srcfbp1.pos, BytePos(0));
context_before:     assert_eq!(srcfbp1.sf.name, PathBuf::from("empty.rs").into());