rw [List.count, List.countp, List.countp.go, List.countp]
case inr
α : Type
inst✝ : BEq α
x a : α
as : List α
hx : ¬(a == x) = true
⊢ List.count x (a :: as) = (bif a == x then 1 else 0) + List.count x as
case inr
α : Type
inst✝ : BEq α
x a : α
as : List α
hx : ¬(a == x) = true
⊢ (bif a == x then List.countp.go (fun x_1 => x_1 == x) as (0 + 1) else List.countp.go (fun x_1 => x_1 == x) as 0) =
    (bif a == x then 1 else 0) + List.countp.go (fun x_1 => x_1 == x) as 0