Theorem: ASCII.String.append_assoc (ASCII/Lemmas.lean)

State before:
s t u : ASCII.String
⊢ s ++ t ++ u = s ++ (t ++ u)
Tactic:
ext
State after:
case a.a
s t u : ASCII.String
⊢ (s ++ t ++ u).toByteArray.data = (s ++ (t ++ u)).toByteArray.data

State before:
case a.a
s t u : ASCII.String
⊢ (s ++ t ++ u).toByteArray.data = (s ++ (t ++ u)).toByteArray.data
Tactic:
simp [Array.append_assoc]
State after:
no goals