[java-dfa] getArrayElementValue: fix unboxing Object[] arrays

Fixes IDEA-288566 Wrong warning at array element instanceof when it was autoboxed

GitOrigin-RevId: f4c1a4bceca84db8842541ed0468af8785a839c7

java/java-analysis-impl/src/com/intellij/codeInspection/dataFlow/jvm/descriptors/ArrayElementDescriptor.java

@@ -97,6 +97,12 @@ public final class ArrayElementDescriptor extends JvmVariableDescriptor {
     if (arrayPsiVar != null) {
       PsiExpression constantArrayElement = ExpressionUtils.getConstantArrayElement(arrayPsiVar, index);
       if (constantArrayElement != null) {
+        PsiType elementType = constantArrayElement.getType();
+        if (componentType instanceof DfReferenceType && elementType instanceof PsiPrimitiveType &&
+            !TypeConstraint.fromDfType(componentType).isPrimitiveWrapper()) {
+          componentType = DfTypes.typedObject(((PsiPrimitiveType)elementType).getBoxedType(constantArrayElement), Nullability.UNKNOWN)
+            .meet(componentType);
+        }
         return getAdvancedExpressionDfaValue(factory, constantArrayElement, componentType);
       }
     }

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

@@ -0,0 +1,7 @@
+public class BoxingInArrayDeclaration {
+
+  public static void main(String[] args) {
+    Object[] arr = {1, 2};
+    System.out.println(<warning descr="Condition 'arr[0] instanceof Integer' is always 'true'">arr[0] instanceof Integer</warning>);
+  }
+}

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

@@ -718,4 +718,5 @@ public class DataFlowInspectionTest extends DataFlowInspectionTestCase {
   public void testEqualsTwoFields() { doTest();}
   public void testPureMethodReadsMutableArray() { doTest(); }
   public void testBoxingInConstructorArguments() { doTest(); }
+  public void testBoxingInArrayDeclaration() { doTest(); }
 }