I've been blinded by too much logic - ugghhh, the PAIN; make it stop, make it STOP!!!This idea of "shadow functions" is just some fail theory that contradicts with the definition of what a functions are.
Basic functions are just T, S, F and N and there is objective and subjective aspects in them. When a function is oriented by the subjective aspect, the objective aspect gets repressed to the furthest degree due to mistrust in the objective aspect. This trust in the subjective and repressing the objective means introverted attitude of a function and it should be obvious to people that you cant really trust and enforce an subjective orientation, while also mistrusting and repressing its opposite as they are mutually exclusive. So while Ti dom cant have Te, he can still have Fe as Fe doesent contradict with Ti. You need to see it as one judging function(T or F) being favored by the subjective world and the other is pushed towards its opposite, the objective world. Same goes with perceiving functions. For example if someone prefers to focus on the things that sensations bring in him instead of just purely focusing on the sensation itself, he can still focus on the possibilities in the objective world(have Ne). You see there is just one truth to people and only schizophrenics can hold two contrary truths. For an INTP the "truth" comes from the subjective logic, possibilities that lie in the objective world, what the sensations release in him and values in the objective world. While logic of the objective world is met with mistrust, ideas without any relation to objective world seem just crazy, sensation itself doesent represent the real truths but are just representations of deeper truths and values without any relation to the external world makes no sense.
When jungians talk of the shadow(not those people who use the term shadow function, but those that invented typology and the term shadow), they are talking about things in yourself that you are not conscious of and are opposite to who you think you are. For example a humble person has a greedy shadow, king has a weak shadow etc etc
Too much Ti must make my brain hurt...