∀ {R : Type uR} [inst : CommSemiring R] {ι : Type u_1} {A : ι → Type u_2} [inst_1 : (i : ι) → Semiring (A i)]
  [inst_2 : (i : ι) → Algebra R (A i)] {i j : ι} (h : i = j) (a : A i), (AlgEquiv.cast h) a = cast ⋯ a