Java: Add a couple of difficult condition correlation tests.

Author: aschackmull

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

@@ -436,4 +436,39 @@ public void corrCondLoop2(boolean a[]) {
       }
     }
   }
+
+  public void loopCorrTest1(int[] a) {
+    boolean ready = a.length > 7;
+    Object x = new Object();
+    for (int i = 0; i < a.length; i++) {
+      // condition correlates with itself through iterations when ready isn't updated
+      if (!ready) {
+        x = null;
+      } else {
+        x.hashCode(); // Spurious NPE - false positive
+      }
+      if ((a[i] & 1) != 0) {
+        ready = (a[i] & 2) != 0;
+        x = new Object();
+      }
+    }
+  }
+
+  public void loopCorrTest2(boolean[] a) {
+    Object x = new Object();
+    boolean cur = a[0];
+    for (int i = 1; i < a.length; i++) {
+      boolean prev = cur;
+      cur = a[i];
+      if (!prev) {
+        // correctly guarded by !cur from the _previous_ iteration
+        x.hashCode(); // Spurious NPE - false positive
+      } else {
+        x = new Object();
+      }
+      if (cur) {
+        x = null;
+      }
+    }
+  }
 }

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

@@ -18,6 +18,8 @@
 | B.java:279:7:279:7 | a | Variable $@ may be null at this access 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 at this access because of $@ assignment. | B.java:287:5:287:44 | int[] b | b | B.java:287:11:287:43 | b | this |
 | B.java:408:7:408:7 | x | Variable $@ may be null at this access as suggested by $@ null guard. | B.java:374:23:374:30 | x | x | B.java:375:23:375:31 | ... != ... | this |
+| B.java:448:9:448:9 | x | Variable $@ may be null at this access because of $@ assignment. | B.java:442:5:442:28 | Object x | x | B.java:446:9:446:16 | ...=... | this |
+| B.java:465:9:465:9 | x | Variable $@ may be null at this access because of $@ assignment. | B.java:458:5:458:28 | Object x | x | B.java:470:9:470:16 | ...=... | this |
 | C.java:9:44:9:45 | a2 | Variable $@ may be null at this access 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 at this access 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 at this access as suggested by $@ null guard. | C.java:8:5:8:21 | long[] a3 | a3 | C.java:9:38:9:58 | ... != ... | this |