IDEA-42948 Idea fails to recognize "non-nullness" after unchecked cast

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

@@ -28,13 +28,11 @@ import com.intellij.psi.*;
 import com.intellij.psi.tree.IElementType;
 import com.intellij.psi.util.PsiTreeUtil;
 import com.intellij.psi.util.PsiUtil;
-import com.intellij.psi.util.RedundantCastUtil;
 import com.intellij.psi.util.TypeConversionUtil;
 import com.intellij.refactoring.psi.PropertyUtils;
 import com.intellij.util.IncorrectOperationException;
 import com.intellij.util.containers.Stack;
 import org.jetbrains.annotations.NonNls;
-import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
 import java.util.ArrayList;
@@ -1596,33 +1594,14 @@ class ControlFlowAnalyzer extends JavaElementVisitor {
       pushTypeOrUnknown(castExpression);
     }
 
-    addInstruction(createCastInstruction(castExpression));
+    final PsiTypeElement typeElement = castExpression.getCastType();
+    if (typeElement != null && operand != null) {
+      addInstruction(new TypeCastInstruction(castExpression, operand, typeElement.getType()));
+    }
     finishElement(castExpression);
   }
 
   @Override public void visitClass(PsiClass aClass) {
   }
 
-  @NotNull
-  private static Instruction createCastInstruction(PsiTypeCastExpression castExpression) {
-    PsiExpression expr = castExpression.getOperand();
-    final PsiTypeElement typeElement = castExpression.getCastType();
-    if (typeElement != null && !RedundantCastUtil.isTypeCastSemantical(castExpression)) {
-      PsiType castType = typeElement.getType();
-      if (expr != null) {
-        return new TypeCastInstruction(castExpression, expr, castType);
-      }
-    }
-    return new Instruction() {
-
-      @Override
-      public DfaInstructionState[] accept(DataFlowRunner runner, DfaMemoryState stateBefore, InstructionVisitor visitor) {
-        stateBefore.pop();
-        stateBefore.push(DfaUnknownValue.getInstance());
-        return nextInstruction(runner, stateBefore);
-      }
-    };
-  }
-
-
 }

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

@@ -0,0 +1,16 @@
+import org.jetbrains.annotations.NotNull;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.List;
+
+public class BrokenAlignment {
+  void t() {
+    @NotNull Collection list = new ArrayList();
+    List<String> strings = (List<String>) list;
+    if (<warning descr="Condition 'strings != null' is always 'true'">strings != null</warning>) {
+      int foo = 42;
+    }
+  }
+
+}

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

@@ -90,5 +90,6 @@ public class DataFlowInspectionFixtureTest extends JavaCodeInsightFixtureTestCas
   public void testReturningNullFromVoidMethod() throws Throwable { doTest(); }
 
   public void testCatchRuntimeException() throws Throwable { doTest(); }
+  public void testPreserveNullableOnUncheckedCast() throws Throwable { doTest(); }
 
 }