. contradiction
case zero
x : Nat
h : x < 0
⊢ (Array.range 0)[x] = x

case succ
x n✝ : Nat
a✝ : ∀ (h : x < n✝), (Array.range n✝)[x] = x
h : x < n✝ + 1
⊢ (Array.range (n✝ + 1))[x] = x
case succ
x n✝ : Nat
a✝ : ∀ (h : x < n✝), (Array.range n✝)[x] = x
h : x < n✝ + 1
⊢ (Array.range (n✝ + 1))[x] = x