🐛 Fix SequenceSet#slice when starting at "*"

When the starting index points to "*", the `min <= max` comparison
fails and an exception is raised.

Without changing the basic `#slice_range` structure and algorithm, the
simplest fix is to use the internal integers for `min` and `max`, which
will always be comparable.

Author: nevans

lib/net/imap/sequence_set.rb

@@ -2434,11 +2434,9 @@ def slice_range(range)
         end
         if (first * last).positive? && last < first
           remain_frozen_empty
-        elsif (min = at(first))
-          max = at(last)
-          max = :* if max.nil?
-          if    max == :*  then self & (min..)
-          elsif min <= max then self & (min..max)
+        elsif (min = sorted_set_num_at(first))
+          max = sorted_set_num_at(last) || STAR_INT
+          if    min <= max then intersection export_minmax_entry [min, max]
           else                  remain_frozen_empty
           end
         end

test/net/imap/test_sequence_set.rb

@@ -496,15 +496,6 @@ def pend_slice_lomax(set, start, actual)
     assert_equal set[start..], actual
   end
 
-  def pend_slice_star(expected, &)
-    pend_slice_bug "don't crash when min == :*" do
-      assert_same expected, yield
-    end
-    assert_raise_with_message(ArgumentError,
-                              /\Acomparison of Symbol with \d+ /,
-                              &)
-  end
-
   def pend_slice_nil(actual)
     pend_slice_bug "return nil for invalid slice start index" do
       assert_nil actual
@@ -616,7 +607,7 @@ def pend_slice_zero_len(&)
     assert_same SequenceSet.empty, set[-100..   99]  # i.e: 100..  99
     assert_same SequenceSet.empty, set[  -1... 199]  # i.e: 199...199
     assert_same SequenceSet.empty, set[  -1..  198]  # i.e: 199...198
-    pend_slice_star SequenceSet.empty do SequenceSet.full[-1..0] end
+    assert_same SequenceSet.empty, SequenceSet.full[-1..0]
     assert_same SequenceSet.empty, SequenceSet.full[-1...0]
   end