syntax_data: {"ast_node_type":"function","tokens":[{"end":77,"kind":"keyword","start":0,"text":"pub"}]}
source_snippet:     pub fn within_macro(self, within: Span, sm: &SourceMap) -> Option<Span> {
context_before:     /// expr, then this will return the span of the `$ident` macro variable.
context_after:         match Span::prepare_to_combine(self, within) {