more advanced addition world

Game/Tactic/Apply.lean

@@ -20,3 +20,9 @@ example (A B C : Prop) (ha : A) (f : A → B) (g : B → C) : C := by
   apply f at ha
   apply g at ha
   exact ha
+
+-- failing test
+example (h1 : ∀ x, Nat.succ x = 4 → x = 3) (a : Nat) (h : Nat.succ a = 4) : a = 3 := by
+  -- apply h1 at h -- fails
+  replace h := h1 _ h -- works
+  exact h