fact: Fixpoint tsize_flat(T: ty) := match T with | TTop => 1 | TAll T1 T2 => S (tsize_flat T1 + tsize_flat T2) | TSel _ U => 1 + tsize_flat U end.
imports: Lia Equations(Equations) Coq.Relations.Relation_Operators Coq.Wellfounded.Lexicographic_Product