Arguments eq_bigcupl [T U A] B F _ _.
Global Instance eq_bigcup T U : Proper (set_eq ==> pointwise_relation T (@set_eq U) ==> set_eq) bigcup.

Lemma curry_imset2r T U V (f : T -> U -> V) A1 A2 :
f @2: (A1, A2) <--> \bigcup_(x2 in A2) f^~ x2 @: A1.