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