use (fun _ => true)
case refl
ν : Type u_1
inst✝ : DecidableEq ν
x : ν
⊢ ∃ τ, τ x = true ∧ ¬PropAssignment.set τ x (!τ x) x = true
case h
ν : Type u_1
inst✝ : DecidableEq ν
x : ν
⊢ true = true ∧ ¬PropAssignment.set (fun x => true) x (!true) x = true