getIntroducedTypePatterns

The following rules apply to a statement if (e) S: - A pattern variable is introduced by if (e) S iff (i) it is introduced by e when false and (ii) S cannot complete normally. The following rules apply to a statement if (e) S else T: - A pattern variable is introduced by if (e) S else T iff either: - It is introduced by e when true, and S can complete normally, and T cannot complete normally; or - It is introduced by e when false, and S cannot complete normally, and T can complete normally.