matchUnknownFVarBug.lean:2:2-2:7: error: missing cases:
(some (Nat.succ _)), Eq.refl, (some _), Eq.refl
none, Eq.refl, none, Eq.refl
matchUnknownFVarBug.lean:3:18-3:19: error: unsolved goals
n? : Option Nat
h : n? = some 0
x✝ : Option Nat
h' : some 0 = x✝
⊢ False