message: Reserve appropriate number of tuple labels
  The upper bound of the range is exclusive, but the reserve function is
  inclusive.
diff: @@ -101,7 +101,7 @@ impl StringInterner {
  /// Get or intern a slice of strings in the form `_{index}` for each index in `range`.
  pub fn get_tuple_labels(&mut self, range: Range<usize>) -> &[StringId] {
  - self.reserve_tuple_labels(range.end);
  + self.reserve_tuple_labels(range.end.saturating_sub(1));
  &self.tuple_labels[range]
  }
  