∀ {𝕜 : Type u_1} [inst : RCLike 𝕜] (x y : 𝕜),
  ↑(RCLike.re (x + y)) + ↑(RCLike.im (x + y)) * Complex.I =
    ↑(RCLike.re x) + ↑(RCLike.im x) * Complex.I + (↑(RCLike.re y) + ↑(RCLike.im y) * Complex.I)