∀ {A : Type u_4} [inst : CommRing A] {K : Type u_5} [inst_1 : Field K] [inst_2 : Algebra A K] [IsFractionRing A K]
  {L : Type u_8} [inst_4 : Field L] {g : A →+* L} {f : K →+* L},
  f.comp (algebraMap A K) = g → f.fieldRange = Subfield.closure ↑g.range