apply congrArg
case cons.cons.inr.inl
α : Type u_1
inst✝ : DecidableEq α
x : α
xs : List α
ih :
  ∀ (acc : List (α × Nat)),
    length (foldl (fun acc v => incrCounts acc v) acc xs) = length (uniqueAux xs (map Prod.fst acc))
a : α × Nat
as : List (α × Nat)
hfalse : ¬a.fst = x
hin : x ∈ map Prod.fst as
this : x ∈ a.fst :: map Prod.fst as
⊢ length (uniqueAux xs (a.fst :: map Prod.fst (incrCounts as x))) = length (uniqueAux xs (a.fst :: map Prod.fst as))
case cons.cons.inr.inl.h
α : Type u_1
inst✝ : DecidableEq α
x : α
xs : List α
ih :
  ∀ (acc : List (α × Nat)),
    length (foldl (fun acc v => incrCounts acc v) acc xs) = length (uniqueAux xs (map Prod.fst acc))
a : α × Nat
as : List (α × Nat)
hfalse : ¬a.fst = x
hin : x ∈ map Prod.fst as
this : x ∈ a.fst :: map Prod.fst as
⊢ uniqueAux xs (a.fst :: map Prod.fst (incrCounts as x)) = uniqueAux xs (a.fst :: map Prod.fst as)