public class Bug307 {
    public void main() {
        IVisitor v = new Visitor();
        Impl2 f = new Impl2();
        Impl1 g = new Impl1();

        f.accept(v);
        g.accept(v);
    }
}

interface IVisitor {
    void visit(Impl1 f);
    void visit(Impl2 fb);
}

interface IAcceptor {
    void accept(IVisitor v);
}

class Visitor implements IVisitor {

    @Override
    public void visit(Impl1 f) {
    }

    @Override
    public void visit(Impl2 fb) {
    }
}

class Impl1 implements IAcceptor {

    @Override
    public void accept(IVisitor v) {
        v.visit(this);
    }
}

class Impl2 implements IAcceptor {

    @Override
    public void accept(IVisitor v) {
        v.visit(this);
    }
}