// semantics-unified: check + for plugin strings and integers

static box Main {
    main() {
        // plugin StringBox concat (both sides)
        local a = new StringBox("12")
        local b = new StringBox("30")
        print(a + b)         // expect 1230

        // mixed concat (host string + plugin string)
        print("x = " + a)    // expect x = 12

        // plugin IntegerBox add
        local i = new IntegerBox(10)
        local j = new IntegerBox(5)
        print(i + j)         // expect 15

        return 0
    }
}