class InserterBase {
public:
    virtual void InsertHelper(void *instr, void *insertPoint) const = 0;
};

class SomeInserter final : public InserterBase {
public:
    void InsertHelper(void *instr, void *insertPoint) const override;
};

// This class intentionally has no member variables. It only provides the
// various CreateXxx methods.
template<typename BuilderT>
class IRBuilderImpl {
    void Insert(void *instr) const {
        const BuilderT *builder = static_cast<const BuilderT *>(this);
        builder->Insert(instr);
    }

public:
    void CreateFoo() {
        Insert(nullptr);
    }
};

class IRBuilder : public IRBuilderImpl<IRBuilder> {
    void *m_insertPoint;
    InserterBase &m_inserter;

public:
    IRBuilder(void *insertPoint, InserterBase &inserter)
        : m_insertPoint(insertPoint), m_inserter(inserter) {}

    void *GetInsertPoint() const { return m_insertPoint; }

    void Insert(void *foo) const {
        m_inserter.InsertHelper(foo, GetInsertPoint());
    }
};

class SomeIRBuilder : public IRBuilderImpl<SomeIRBuilder> {
    SomeInserter m_inserter;
    IRBuilder m_genericBuilder;

public:
    SomeIRBuilder(void *insertPoint) : m_genericBuilder(insertPoint, m_inserter) {}

    void *GetInsertPoint() const { return m_genericBuilder.GetInsertPoint(); }

    void Insert(void *foo) const {
        m_inserter.InsertHelper(foo, GetInsertPoint());
    }

    IRBuilder &GetGenericBuilder() { return m_genericBuilder; }
};

void instantiateHelper(IRBuilder &builder) {
    builder.CreateFoo();
}

void instantiate(void *insertPoint) {
    SomeIRBuilder some(insertPoint);
    some.CreateFoo();
    instantiateHelper(some.GetGenericBuilder());
}