IDEA-183217 Nullability problem is not reported for field when it's marked as unknown after loading on stack

java/java-analysis-impl/src/com/intellij/codeInspection/dataFlow/DfaMemoryStateImpl.java

@@ -1305,6 +1305,9 @@ public class DfaMemoryStateImpl implements DfaMemoryState {
   }
 
   void doFlush(@NotNull DfaVariableValue varPlain, boolean markUnknown) {
+    if(isNull(varPlain)) {
+      myStack.replaceAll(val -> val == varPlain ? myFactory.getConstFactory().getNull() : val);
+    }
     DfaVariableValue varNegated = varPlain.getNegatedValue();
 
     removeEquivalenceRelations(varPlain);

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

@@ -0,0 +1,13 @@
+import java.util.*;
+import java.util.concurrent.atomic.*;
+
+// IDEA-183217
+class Test {
+  private AtomicLong timeStamp;
+
+  private void method() {
+    if (timeStamp == null) {
+      timeStamp.<warning descr="Method invocation 'set' may produce 'java.lang.NullPointerException'">set</warning>(Calendar.getInstance().getTimeInMillis()); // not reported
+    }
+  }
+}

java/java-tests/testSrc/com/intellij/java/codeInspection/DataFlowInspection8Test.java

@@ -218,4 +218,5 @@ public class DataFlowInspection8Test extends DataFlowInspectionTestCase {
   }
 
   public void testPrimitiveGetters() { doTest(); }
+  public void testUnknownOnStack() { doTest(); }
 }