Add more test cases

semantic/array-access-on-returned-value.mj

+class Main {
+    public static void main(String[] arguments) {
+        Main main = new Main();
+        main.getArray()[0] = 1;
+        
+        new Main().getArray()[0] = 2;
+    }
+
+    public int[] getArray() {
+        return new int[0];
+    }
+}

semantic/assign-system-out.invalid.mj

+class Main {
+    public static void main(String[] arguments) {
+        System.out = null;
+    }
+}

semantic/assign-system.invalid.mj

+class Main {
+    public static void main(String[] arguments) {
+        System = null;
+    }
+}

semantic/field-access-on-returned-value.mj

+class Main {
+    public static void main(String[] arguments) {
+        Main main = new Main();
+        main.getX().x = null;
+
+        new Main().getX().x = null;
+    }
+
+    public X getX() {
+        return new X();
+    }
+}
+
+class X {
+    public X x;
+}

semantic/too-much-array-access.invalid.mj

+class TooMuchArrayAccess {
+    public static void main(String[] args) {
+        int[] array = new int[3];
+        array[2][1] = 42;
+    }
+}