constructor
L : Type u
ν : Type v
inst✝¹ : LitVar L ν
inst✝ : LawfulLitVar L ν
l1 l2 : L
⊢ l1 = l2 ↔ toVar l1 = toVar l2 ∧ polarity l1 = polarity l2
case mp
L : Type u
ν : Type v
inst✝¹ : LitVar L ν
inst✝ : LawfulLitVar L ν
l1 l2 : L
⊢ l1 = l2 → toVar l1 = toVar l2 ∧ polarity l1 = polarity l2

case mpr
L : Type u
ν : Type v
inst✝¹ : LitVar L ν
inst✝ : LawfulLitVar L ν
l1 l2 : L
⊢ toVar l1 = toVar l2 ∧ polarity l1 = polarity l2 → l1 = l2