JEP 482 spec states that

It is a compile-time error if a qualified `this` expression occurs in an
early construction context ([8.8.7.1]) of the class named by *TypeName*.

However, this code compiles with JDK-23 b 25:

static class Test {
    int a;
    Test() {}

    Test(int a) {
        Test.this.a = 1;
        this();
    }
}

    public static void main(String argv[]) {
        Test test = new Test(1);
    }

Per email discussion, the compiler implements a more sophisticated treatment of qualified this, thus the discrepancy. The specification should address this change.