IDEA-87652

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

@@ -540,7 +540,7 @@ public class DfaMemoryStateImpl implements DfaMemoryState {
     DfaTypeValue dfaType = (DfaTypeValue)dfaCond.getRightOperand();
 
     final DfaVariableState varState = getVariableState(dfaVar);
-    varState.setNullable(dfaType.isNullable());
+    varState.setNullable(varState.isNullable() || dfaType.isNullable());
     return !isNotNull(dfaVar) || varState.setInstanceofValue(dfaType);
   }
 

java/java-tests/testData/inspection/dataFlow/NullableProblemThroughCast/expected.xml

@@ -0,0 +1,8 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<problems>
+  <problem>
+    <file>Npe.java</file>
+    <line>6</line>
+    <description>Method invocation &lt;code&gt;((SomeInterfaceImpl)x).bar()&lt;/code&gt; may produce &lt;code&gt;java.lang.NullPointerException&lt;/code&gt;</description>
+  </problem>
+</problems>

java/java-tests/testData/inspection/dataFlow/NullableProblemThroughCast/src/Npe.java

@@ -0,0 +1,18 @@
+import org.jetbrains.annotations.Nullable;
+
+public class Npe {
+  
+  void foo(@Nullable SomeInterface x) {
+    ((SomeInterfaceImpl)x).bar();
+  }
+
+  interface SomeInterface {
+    void bar();
+  }
+
+  class SomeInterfaceImpl implements SomeInterface {
+    @Override
+    public void bar() {
+    }
+  }
+}

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

@@ -96,6 +96,7 @@ public class DataFlowInspectionTest extends InspectionTestCase {
 
   public void testNullable() throws Exception { doTest15(); }
   public void testNullableThroughCast() throws Exception { doTest15(); }
+  public void testNullableProblemThroughCast() throws Exception { doTest15(); }
   public void testNullableThroughVariable() throws Exception { doTest15(); }
   public void testNullableThroughVariableShouldNotBeReported() throws Exception { doTest15(); }
   public void testNullableAssignment() throws Exception { doTest15(); }