syntax_data: {"ast_node_type":"other","tokens":[{"end":62,"kind":"keyword","start":0,"text":"source_len:"}]}
source_snippet:             source_len: RelativeBytePos::from_u32(source_len),
context_before:             start_pos: BytePos::from_u32(0),
context_after:             lines: FreezeLock::frozen(SourceFileLines::Lines(lines)),