[iter] Add hb_iter_with_fallback_t instead

src/hb-array.hh

@@ -37,10 +37,7 @@ template <typename Type>
 struct hb_sorted_array_t;
 
 template <typename Type>
-struct hb_array_t :
+struct hb_array_t : hb_iter_with_fallback_t<hb_array_t<Type>, Type&>
-  hb_iter_with_mixin_t<hb_iter_fallback_mixin_t,
-		       hb_array_t<Type>,
-		       Type&>
 {
   /*
    * Constructors.

src/hb-iter.hh

@@ -132,19 +132,6 @@ template <typename Type, unsigned int length> hb_array_t<Type>
 hb_iter (Type (&array)[length]) { return hb_iter (array, length); }
 
 
-template <template<typename iter_t, typename item_t> class mixin_t,
-	  typename iter_t,
-	  typename item_t = typename iter_t::__item_t__>
-struct hb_iter_with_mixin_t :
-  hb_iter_t<iter_t, item_t>,
-  mixin_t<iter_t, item_t>
-{
-  protected:
-  hb_iter_with_mixin_t () {}
-  hb_iter_with_mixin_t (const hb_iter_with_mixin_t &o HB_UNUSED) {}
-  void operator = (const hb_iter_with_mixin_t &o HB_UNUSED) {}
-};
-
 /* Mixin to fill in what the subclass doesn't provide. */
 template <typename iter_t, typename item_t = typename iter_t::__item_t__>
 struct hb_iter_fallback_mixin_t
@@ -178,6 +165,17 @@ struct hb_iter_fallback_mixin_t
   void operator = (const hb_iter_fallback_mixin_t &o HB_UNUSED) {}
 };
 
+template <typename iter_t, typename item_t = typename iter_t::__item_t__>
+struct hb_iter_with_fallback_t :
+  hb_iter_t<iter_t, item_t>,
+  hb_iter_fallback_mixin_t<iter_t, item_t>
+{
+  protected:
+  hb_iter_with_fallback_t () {}
+  hb_iter_with_fallback_t (const hb_iter_with_fallback_t &o HB_UNUSED) {}
+  void operator = (const hb_iter_with_fallback_t &o HB_UNUSED) {}
+};
+
 /*
  * Meta-programming predicates.
  */
@@ -283,9 +281,8 @@ hb_map (Proj&& f)
 template <typename Iter, typename Pred, typename Proj,
 	 hb_enable_if (hb_is_iterator (Iter))>
 struct hb_filter_iter_t :
-  hb_iter_with_mixin_t<hb_iter_fallback_mixin_t,
+  hb_iter_with_fallback_t<hb_filter_iter_t<Iter, Pred, Proj>,
-		       hb_filter_iter_t<Iter, Pred, Proj>,
+			  typename Iter::item_t>
-		       typename Iter::item_t>
 {
   hb_filter_iter_t (const Iter& it_, Pred&& p, Proj&& f) : it (it_), p (p), f (f)
   { while (it && !p (f (*it))) ++it; }

src/hb-ot-layout-common.hh

@@ -1120,10 +1120,7 @@ struct Coverage
     }
   }
 
-  struct iter_t :
+  struct iter_t : hb_iter_with_fallback_t<iter_t, hb_codepoint_t>
-    hb_iter_with_mixin_t<hb_iter_fallback_mixin_t,
-			 iter_t,
-			 hb_codepoint_t>
   {
     static constexpr bool is_sorted_iterator = true;
     iter_t (const Coverage &c_ = Null(Coverage))

src/hb-set.hh

@@ -682,10 +682,7 @@ struct hb_set_t
   /*
    * Iterator implementation.
    */
-  struct iter_t :
+  struct iter_t : hb_iter_with_fallback_t<iter_t, hb_codepoint_t>
-    hb_iter_with_mixin_t<hb_iter_fallback_mixin_t,
-			 iter_t,
-			 hb_codepoint_t>
   {
     static constexpr bool is_sorted_iterator = true;
     iter_t (const hb_set_t &s_ = Null(hb_set_t)) :

src/test-iter.cc

@@ -33,10 +33,7 @@
 
 
 template <typename T>
-struct array_iter_t :
+struct array_iter_t : hb_iter_with_fallback_t<array_iter_t<T>, T&>
-  hb_iter_with_mixin_t<hb_iter_fallback_mixin_t,
-		       array_iter_t<T>,
-		       T&>
 {
   array_iter_t (hb_array_t<T> arr_) : arr (arr_) {}