unknown variables should not be nullable-enabled after instanceof

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

@@ -585,9 +585,13 @@ public class DfaMemoryStateImpl implements DfaMemoryState {
           }
           return applyCondition(compareToNull(dfaVar, false));
         }
+        boolean wasUnknown = getVariableState(dfaVar).getNullability() == Nullness.UNKNOWN;
         if (applyCondition(compareToNull(dfaVar, true))) {
           DfaVariableState newState = getVariableState(dfaVar).withInstanceofValue((DfaTypeValue)dfaRight);
           if (newState != null) {
+            if (wasUnknown) {
+              newState = newState.withNullability(Nullness.UNKNOWN);
+            }
             setVariableState(dfaVar, newState);
             return true;
           }

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

@@ -0,0 +1,11 @@
+class Some {
+  void foo(Object o) {
+    if (o instanceof String) {
+
+    }
+    o.hashCode();
+  }
+
+}
+
+

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

@@ -308,6 +308,7 @@ public class DataFlowInspectionTest extends LightCodeInsightFixtureTestCase {
   
   public void testVariablesDiverge() { doTest(); }
   public void testDontForgetInstanceofInfoWhenMerging() { doTest(); }
+  public void testDontMakeNullableAfterInstanceof() { doTest(); }
   
   public void _testNullCheckBeforeInstanceof() { doTest(); } // http://youtrack.jetbrains.com/issue/IDEA-113220
 }