While compiling:

template<typename T>
struct Type2Type {
   typedef T Type;
};

template<class T>
inline void foo(Type2Type<T> const&) {
   int x = NOT_HERE;
}

int main(int, char *) {
 //  std::cout << "Hello world!" << std::endl;
}

g++ gives an error about NOT_HERE being declared.  Rightly so, but the function `foo' is never called or explicity instantiated, so `foo' should never be compiled.

From "14.7.1 Implicit instantiation" of the ISO C++ standard:
 9. An implementation shall not implicitly instantiate a function template,
    a member template, a non-virtual member function, a member class or a
    static data member of a class template that does not require instantia-
    tion.