Open Scope Z_scope.
(** bug 4132: omega was using "simpl" either on whole equations, or on delimited but wrong spots. This was leading to unexpected reductions when one atom (here [b]) is an evaluable reference instead of a variable. *)
omega. (* Pierre L: according to a comment of bug report #4132,
this might have triggered "index out of bounds" in the past,
but I never managed to reproduce that in any version,
even before my fix. *)
Qed.

Lemma foo3 x y (b := 0) (H1 : x <= y) (H2 : y <= b) : x <= b.