Section Wf_Disjoint_Union.
Variables A B : Type.
Variable leA : A -> A -> Prop.
Variable leB : B -> B -> Prop.
Notation Le_AsB := (le_AsB A B leA leB).

Lemma acc_B_sum :
well_founded leA -> forall x:B, Acc leB x -> Acc Le_AsB (inr A x).