syntax_data: {"ast_node_type":"variable","tokens":[{"end":77,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:         let (lo_or_index, len_with_tag_or_marker, ctxt_or_parent_or_marker) =
context_before:     fn span(index: u32) -> Span {
context_after:             (index, BASE_LEN_INTERNED_MARKER, CTXT_INTERNED_MARKER);