Section FuncEq.
Variables (A1 A2 A3 A4 A5 A6 A7 B : Type).
Proof using. intros. subst. auto. Qed.
Proof using. intros. subst. auto. Qed.
Proof using. intros. subst. auto. Qed.

Lemma args_eq_4 : forall (f:A1->A2->A3->A4->B) x1 y1 x2 y2 x3 y3 x4 y4,
x1 = y1 -> x2 = y2 -> x3 = y3 -> x4 = y4 ->
f x1 x2 x3 x4 = f y1 y2 y3 y4.