Variable assignment in return statement is not correctly processed

[flack]

Describe the bug
The following functions are identical:

function a() {
    static $cache = null;

    if ($cache === null) {
        $cache = true;
    }
    return $cache;
}

function b() {
    static $cache = null;

    return $cache ??= true;
}

In function b() PDT marks the $cache variable as unused.

Describe the eclipse environment
Eclipse 2023-06, PDT 8.1.0.202307051059

Describe your system

• macOS 12.6

To Reproduce
see above

Expected behavior
There should be no warning

Screenshots