Add tests for nullness tracking by comparing variables.

Author: criemen

java/ql/test/query-tests/Nullness/B.java

@@ -344,4 +344,31 @@ public void corrConds4(Object y) {
       x.hashCode(); // OK
     }
   }
+
+  public void corrConds5(Object y, Object z) {
+    Object x = null;
+    if(y == z) {
+      x = new Object();
+    }
+    if(y == z) {
+      x.hashCode(); // OK
+    }
+
+    Object x2 = null;
+    if(y != z) {
+      x2 = new Object();
+    }
+    if(y != z) {
+      x2.hashCode(); // OK
+    }
+
+    Object x3 = null;
+    if(y != z) {
+      x3 = new Object();
+    }
+    if(!(y == z)) {
+      x3.hashCode(); // OK
+    }
+  }
+
 }

java/ql/test/query-tests/Nullness/NullMaybe.expected

@@ -17,6 +17,9 @@
 | B.java:190:7:190:7 | o | Variable $@ may be null here because of $@ assignment. | B.java:178:5:178:20 | Object o | o | B.java:186:5:186:12 | ...=... | this |
 | B.java:279:7:279:7 | a | Variable $@ may be null here because of $@ assignment. | B.java:276:5:276:19 | int[] a | a | B.java:276:11:276:18 | a | this |
 | B.java:292:7:292:7 | b | Variable $@ may be null here because of $@ assignment. | B.java:287:5:287:44 | int[] b | b | B.java:287:11:287:43 | b | this |
+| B.java:354:7:354:7 | x | Variable $@ may be null here because of $@ assignment. | B.java:349:5:349:20 | Object x | x | B.java:349:12:349:19 | x | this |
+| B.java:362:7:362:8 | x2 | Variable $@ may be null here because of $@ assignment. | B.java:357:5:357:21 | Object x2 | x2 | B.java:357:12:357:20 | x2 | this |
+| B.java:370:7:370:8 | x3 | Variable $@ may be null here because of $@ assignment. | B.java:365:5:365:21 | Object x3 | x3 | B.java:365:12:365:20 | x3 | this |
 | C.java:9:44:9:45 | a2 | Variable $@ may be null here as suggested by $@ null guard. | C.java:6:5:6:23 | long[][] a2 | a2 | C.java:7:34:7:54 | ... != ... | this |
 | C.java:9:44:9:45 | a2 | Variable $@ may be null here because of $@ assignment. | C.java:6:5:6:23 | long[][] a2 | a2 | C.java:6:14:6:22 | a2 | this |
 | C.java:10:17:10:18 | a3 | Variable $@ may be null here as suggested by $@ null guard. | C.java:8:5:8:21 | long[] a3 | a3 | C.java:9:38:9:58 | ... != ... | this |