Fix #1030 (related to #982)

Author: cprudhom

solver/src/main/java/org/chocosolver/util/objects/setDataStructures/iterable/IntIterableSetUtils.java

@@ -425,9 +425,11 @@ public static void union(IntIterableRangeSet setr, IntIterableRangeSet set1, Int
         int s2 = set2.SIZE >> 1;
         if(s1 == 0){
             setr.addAll(set2);
+            return;
         }
         if (s2 == 0) {
             setr.addAll(set1);
+            return;
         }
         if (s1 > 0 && s2 > 0) {
             setr.grow(set1.SIZE);
@@ -494,7 +496,10 @@ public static boolean unionOf(IntIterableRangeSet set1, IntIterableRangeSet set2
         if(s1 == 0){
             return set1.addAll(set2);
         }
-        if (s1 > 0 && s2 >= 0) {
+        if(s2 == 0){
+            return false;
+        }
+        if (s1 > 0 && s2 > 0) {
             int i = 0, j = 0;
             int s = 0, c = 0;
             int[] e = new int[set1.SIZE];

solver/src/test/java/org/chocosolver/util/objects/setDataStructures/iterable/IntIterableRangeSetTest.java

@@ -704,6 +704,15 @@ public void testUnion5() {
         Assert.assertEquals(set.size(), 1);
     }
 
+    @Test(groups = "1s", timeOut = 60000)
+    public void testUnion6() {
+        IntIterableRangeSet set = new IntIterableRangeSet(1, 2);
+        IntIterableSetUtils.unionOf(set, new IntIterableRangeSet());
+        Assert.assertEquals(set.size(), 2);
+    }
+
+
+
     @Test(groups = "1s", timeOut = 60000)
     public void testIncludedIn1() {
         Assert.assertTrue(IntIterableSetUtils.includedIn(new IntIterableRangeSet(), new IntIterableRangeSet(0)));