Consider:
template<typename T> struct X; extern X<int> *p; void *q = +p; // #1, complete type affects semantics via ADL template<typename T> struct X {}; X<int> x; // #2, ill-formed, X<int> is incomplete
According to the wording of issue 212, this program is ill-formed, because the single point of instantiation for X<int> is at #1, thus X<int> is an incomplete type even at #2 after the primary template has been completed.