c++ - How to avoid errors while using CRTP?

Question

Using CRTP sometimes I write a code like this:

// this was written first
struct Foo : Base<Foo, ...>
{
   ...
};

// this was copy-pasted from Foo some days later
struct Bar : Base<Foo, ...>
{
   ...
};

And it's very difficult to understand what goes wrong, until I trace code in debugger and see that Bar's members aren't used in Base.

How to reveal this error at compile time?

(I use MSVC2010, so I can use some C++0x features and MSVC language extensions)

Answer 1

In C++0x you have a simple solution. I don't know whether it is implemented in MSVC10 however.

template <typename T>
struct base
{
private:
    ~base() {}
    friend T;
};

// Doesn't compile (base class destructor is private)
struct foo : base<bar> { ... };