intros.
pattern c in |- *; elim c; auto.
Qed.
(************************************************************************)
Definition ifProp (C : Type) (b : bool) (x y : C) : C :=
match b return C with
| true => x
| false => y
end.

Lemma ifProp_or : forall (b : bool) (P Q : Prop), ifProp Prop b P Q -> P \/ Q.
simple induction b; auto.