Qt Creator is not able to list the members of classes which are inherited from their template parameters, like:
template<typename T> class X: public T{};.

The code completion of an instance X<QString> should list all members of QString.

Or another, more complex example:
template<typename T> class C

;
namespace ns{
template<typename T> class B

;
}
template<typename T> class A: public ns::B<T>::type{};

(This latter case (distributed over several include files) is the structure of the Eigen 3 library (eigen.tuxfamily.org), which is (probably) the best c++ library for linear algebra, because it overloads the normal math operators and then optimizes the order and number of function calls during compile time; so it has absolutely no overhead )