Undo an accidental change of namespace

src/data/set/function.lean

@@ -23,19 +23,15 @@ universes u v w x y
 
 variables {α : Type u} {β : Type v} {γ : Type w} {ι : Sort x}
 
-namespace function
+open function
+
+namespace set
 
 /-! ### Restrict -/
 
 lemma range_restrict (f : α → β) (s : set α) : set.range (restrict f s) = f '' s :=
 by { ext x, simp [restrict], refl }
 
-end function
-
-open function
-
-namespace set
-
 variables {s s₁ s₂ : set α} {t t₁ t₂ : set β} {p : set γ} {f f₁ f₂ f₃ : α → β} {g : β → γ}
   {f' f₁' f₂' : β → α} {g' : γ → β}