syntax_data: {"ast_node_type":"function","tokens":[{"end":51,"kind":"keyword","start":0,"text":"fn"}]}
source_snippet:     fn span(lo: u32, len: u16, ctxt: u16) -> Span {
context_before:     #[inline]
context_after:         Span { lo_or_index: lo, len_with_tag_or_marker: len, ctxt_or_parent_or_marker: ctxt }