Sorry, just one more question :) So if we have static ::std::foo<S> f; and foo indeed considers S to be complete... is it then permitted to reference S's members and call S's member functions (like dtor()) in foo's constructor? I guess a silly consideration would be foo's constructor where it would create a temporary S and destroy it (for no specific reason other than to illustrate a point)... e.g. foo::foo() { S tmp; } now... if S type had a member of vector with incomplete type and standard allows for vector itself to be instantiated but not its members when T is incomplete as per vector.overview] 4) ... then at a time of '~S' (tmp being destructed) would not vector's destructor also be called? ... and at that point in time will it not reference the members of vector? Perhaps I am confusing myself with 'instantiation' of template types vs 'creation' of variables... at a time of 'static ::std::foo<S> f', i.e. the 'f' variable being actually created... the S.v (our vector of incomplete type) would already be instantiated/type-complete (as in: concrete type inferred from template processing)? Sorry for all the naive questions here -- haven't dived into this thinking for a while... getting old :)