What is the ruling regarding a man saying to a woman who is not his wife: "She is divorced if she does such-and-such," or "She is divorced if she does not do such-and-such," whether the wording is explicit or allusive, and what is the scholarly disagreement concerning this?

Divorce is not valid before the marriage contract, whether it is by an explicit statement or an implicit one, because the Prophet, peace and blessings be upon him, said: "Divorce is for him who takes hold of the leg (i.e., is married)" and: "There is no divorce before marriage." The phrases mentioned in the question do not constitute a divorce, even if uttered by someone who is married, because they are neither explicit nor implicit in divorce.