pub(crate) fn span_to_first_line_string(&self, span: Span) -> String {
let file_lines = self.parse_sess.source_map().span_to_lines(span).ok();
pub(crate) fn span_to_first_line_string(&self, span: Span) -> String {
let file_lines = self.parse_sess.source_map().span_to_lines(span).ok();