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static class Tab<N extends Number> {
    }

    static class FooTab<N extends Number> extends Tab<N> {
    }

    static class BarTab extends Tab<Double> {
    }

    static class Controller<F extends Tab<? extends Number>> {
        void use(F f) {
        }
    }

    static {
        new Controller<Tab<Double>>().use(new FooTab<Double>());
        new Controller<Tab<Double>>().use(new BarTab());
    }