next l' heq => simp [heq]
case h_1
n : Nat
c : DefaultClause n
l : Literal (PosFin n)
x✝ : List (Literal (PosFin n))
l✝ : Literal (PosFin n)
heq✝ : c.clause = [l✝]
⊢ some l✝ = some l ↔ c.clause = [l]
no goals