IDEA-125194 Strange control-flow inspection

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

@@ -118,6 +118,12 @@ public class StandardInstructionVisitor extends InstructionVisitor {
 
     if (dfaDest instanceof DfaVariableValue) {
       DfaVariableValue var = (DfaVariableValue) dfaDest;
+
+      DfaValueFactory factory = runner.getFactory();
+      if (dfaSource instanceof DfaVariableValue && factory.getVarFactory().getAllQualifiedBy(var).contains(dfaSource)) {
+        dfaSource = factory.createTypeValue(((DfaVariableValue)dfaSource).getVariableType(), ((DfaVariableValue)dfaSource).getInherentNullability());
+      }
+
       if (var.getInherentNullability() == Nullness.NOT_NULL) {
         checkNotNullable(memState, dfaSource, NullabilityProblem.assigningToNotNull, instruction.getRExpression());
       }

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

@@ -0,0 +1,12 @@
+class Doo {
+
+  void foo(Throwable e) {
+    Throwable t = e;
+
+    while (t.getCause() != null) t = t.getCause();
+    if (e != t) {
+      System.out.println();
+    }
+  }
+
+}

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

@@ -322,6 +322,7 @@ public class DataFlowInspectionTest extends LightCodeInsightFixtureTestCase {
   public void testNullableBoolean() { doTest(); }
 
   public void testSameComparisonTwice() { doTest(); }
+  public void testRootThrowableCause() { doTest(); }
 
   public void testParametersAreNonnullByDefault() {
     myFixture.addClass("package javax.annotation; public @interface ParametersAreNonnullByDefault {}");