Lean4
/-- Redo the `Nonneg.semifield` instance, because this will get unfolded a lot,
and ends up inserting the non-reducible defeq `ℝ≥0 = { x // x ≥ 0 }` in places where
it needs to be reducible(-with-instances).
-/
noncomputable instance : Semifield ℝ≥0 :=
fast_instance%Function.Injective.semifield toReal Subtype.val_injective rfl rfl (fun _ _ => rfl) (fun _ _ => rfl)
(fun _ => rfl) (fun _ _ => rfl) (fun _ _ => rfl) (fun _ _ => rfl) (fun _ _ => rfl) (fun _ _ => rfl) (fun _ => rfl)
(fun _ => rfl)