Theorem: LambdaCalculi.LambdaTerm.replace'_fst (LambdaCalculi/LambdaCalculus.lean)

State before:
p : LambdaParams
U : Type u_1
C : Type u_2
f : ℕ → LambdaTerm p U C → Option (LambdaTerm p U C)
n : ℕ
h : p.prod = true
t : LambdaTerm p U C
⊢ replace' f n (fst h t) =
    match f n (fst h t) with
    | some u => u
    | none => fst h (replace' f n t)
Tactic:
simp only [replace']
State after:
no goals