simpa [Evalm, Matrix.fun_eq_vec₂, Empty.eq_elim] using
  eval_mk (H := H) (e := ![a, b]) (ε := Empty.elim) (p := Semiformula.Operator.Eq.eq.sentence)
case a.a
L : Language
μ : Type u_1
inst✝² : Operator.Eq L
M : Type u
inst✝¹ : Nonempty M
inst✝ : Structure L M
H : M ⊧ₘ* 𝐄𝐐
a b : M
⊢ (Eval struc ![⟦a⟧, ⟦b⟧] Empty.elim) op(=).sentence ↔ (Eval inst✝ ![a, b] Empty.elim) op(=).sentence
no goals