syntax_data: {"ast_node_type":"other","tokens":[{"end":53,"kind":"keyword","start":0,"text":"self.span_to_source(sp,"}]}
source_snippet:         self.span_to_source(sp, |src, _, end_index| {
context_before:     pub fn span_to_next_source(&self, sp: Span) -> Result<String, SpanSnippetError> {
context_after:             src.get(end_index..).map(|s| s.to_string()).ok_or(SpanSnippetError::IllFormedSpan(sp))