syntax_data: {"ast_node_type":"function","tokens":[{"end":62,"kind":"keyword","start":0,"text":"pub"}]}
source_snippet:     pub fn insert(&self, span: Span, var_span: Span) -> bool {
context_before: impl MetavarSpansMap {
context_after:         match self.0.write().try_insert(span, (var_span, false)) {