fact: Parameter eutt_inv_ret : forall (r1 r2 : R), Ret r1 ≈ Ret r2 -> r1 = r2.
imports: Coq(Setoid Morphisms) ITree(Eq.Shallow) ITree.Core.ITreeDefinition ITree.Basics.Basics ITree.Indexed.Sum ITree.Interp.Interp ITree.Interp.Recursion