Improve lifetimes for get_property_numeric.

src/compare/diff.rs

@@ -2118,7 +2118,7 @@ fn compare_timestamp<'b, 's>(
     _source: &'s str,
     emacs: &'b Token<'s>,
     rust: &'b Timestamp<'s>,
-) -> Result<DiffEntry<'b, 's>, Box<dyn std::error::Error>> {
+) -> Result<DiffEntry<'b, 's>, Box<dyn std::error::Error + 's>> {
     let mut this_status = DiffStatus::Good;
     let mut message = None;