Assume the following class:
struct X : A, B, C{};
What problems might appear if I change it to the following?
struct indirect_C : C{};
struct indirect_BC : B, indirect_C{};
struct X : A, indirect_BC{};
The example may seem contrived, but it happens when you to inherit a variable number of bases through variadic templates, and also want functionality from those bases made available (or not) in the derived class.
template<class... List>
struct X : List...{
using List::something...; // ill-formed in C++11
};
As such, you need a work-around, which is inheriting "recursively" and bringing the functionality into scope at every recursive step:
template<class Head, class... Tail>
struct inherit_indirect
: Head
, inherit_indirect<Tail...>
{
using Head::something;
using inherit_indirect<Tail...>::something;
};
template<class T>
struct inherit_indirect<T>
: T
{
using T::something;
};
(See for example this answer of mine, where I used this technique.)
