False Negative: EqualsArray.ql misses array identity comparisons once the array is widened to `Object` or routed through helper APIs.

# False Negative: EqualsArray.ql misses array identity comparisons once the array is widened to `Object` or routed through helper APIs.

Version
codeql 2.24.3

## Checker
- Checker id: `Likely Bugs/Comparison/EqualsArray.ql`
- Checker description: Detects calls to equals or hashCode methods on array objects, which compare object identity rather than array contents.

## Description of the false negative
These samples still use array identity operations where content comparison was almost certainly intended. The difference is only that the array is first widened to `Object` or compared through `Objects.equals(...)`, which still ends up using reference equality for arrays.

## Affected test cases
### `PosCase1_Var2.java`
Widening the array to `Object` does not change the fact that `equals` still performs identity comparison.

```java
// Calling hashCode() on an array should be flagged as comparing object identity.
package scensct.var.pos;

public class PosCase1_Var2 {
public static void main(String[] args) {
// Variant 2: Intra-procedural refactoring - using a temporary reference
int[] arr = {1, 2, 3};
Object objRef = arr;
int hash = objRef.hashCode(); // Still calling hashCode on the array object
System.out.println(hash);
}
}
```

### `PosCase2_Var1.java`
Calling `equals(Object)` on the array still compares object identity rather than contents.

```java
// Calling equals(Object) on an array with compatible array argument should be flagged as comparing object identity.
package scensct.var.pos;

public class PosCase2_Var1 {
public static void main(String[] args) {
Integer[] a = {1, 2, 3};
Integer[] b = {1, 2, 3};
// Using a temporary variable to alias the array
Object obj1 = a;
Object obj2 = b;
boolean same = obj1.equals(obj2);
System.out.println(same);
}
}
```

### `PosCase2_Var2.java`
The helper API does not change the semantics of array `equals`; it is still an identity comparison.

```java
// Calling equals(Object) on an array with compatible array argument should be flagged as comparing object identity.
package scensct.var.pos;

import java.util.Objects;

public class PosCase2_Var2 {
public static void main(String[] args) {
String[] arr1 = {"x", "y"};
String[] arr2 = {"x", "y"};
// Using Objects.equals which internally calls equals on the first argument
boolean result = Objects.equals(arr1, arr2);
System.out.println(result);
}
}
```

## Cause analysis
The query appears to recognize only direct `array.equals(...)` or `array.hashCode()` calls on obviously array-typed expressions. Once the array is widened to `Object` or the call is wrapped by a library helper like `Objects.equals(...)`, the identity-based behavior is no longer modeled.

That is a real usability gap. Developers often pass arrays through generic APIs before comparing them, and the bug remains the same.

## References
None known.

Start with the Likely Bugs/Comparison/EqualsArray.ql checker and review the affected cases PosCase1_Var2.java, PosCase2_Var1.java, and PosCase2_Var2.java. Trace how widened Object references and Objects.equals(...) are modeled. Done means these identity comparisons are detected without losing the existing direct-call coverage.

Scritto dal modello di indicizzazione a partire dal testo della issue.