fact: Definition addEnvSubst : forall (Q: EnvSubst) (i: nat) (j: nat) (ok: envSub Q i j \/ (forall x, ~envSub Q i x /\ ~envSub Q x j)), EnvSubst.
imports: CoLoR(RelExtras ListPermutation TermsPos ListUtil ListExtras LogicUtil) Coq(Compare_dec Setoid Morphisms Lia PeanoNat)