don't let null checks affect 'unchecked cast' analysis

java/java-tests/testData/inspection/dataFlow/fixture/NullCheckDoesntAffectUncheckedCast.java

@@ -0,0 +1,15 @@
+public class DataFlowBug {
+
+  public int add2(Object left, Object right) {
+    if (left != null && !(left instanceof String)) {
+      return ((<warning descr="Casting 'left' to 'String' may produce 'java.lang.ClassCastException'">String</warning>) left).length();
+
+    }
+    if (!(right instanceof String)) {
+      return ((<warning descr="Casting 'right' to 'String' may produce 'java.lang.ClassCastException'">String</warning>) right).length();
+
+    }
+    return 2;
+  }
+
+}