[libc++][NFC] Refactor enable_ifs in defaulted arguments to defaulted template arguments

[philnik]

Summary

This brings most of the enable_ifs in libc++ to the same style. It also has the nice side-effect of reducing the size of names of these symbols, since the arguments don't get mangled anymore.

[philnik]

Rebased

[philnik]

Rebased

[Mordante]

Thanks for the cleanup! When the CI is happy I'm happy.

[philnik]

Fix formatting

libcxx/include/__chrono/duration.h

 public:
 
 #ifndef _LIBCPP_CXX03_LANG
         constexpr duration() = default;
 #else
         _LIBCPP_HIDE_FROM_ABI duration() {}
 #endif
 
-    template <class _Rep2>
-        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
-        explicit duration(const _Rep2& __r,
-            typename enable_if
-            <
-               is_convertible<const _Rep2&, rep>::value &&
+    template <class _Rep2, __enable_if_t<is_convertible<const _Rep2&, rep>::value &&
                                          (treat_as_floating_point<rep>::value ||
-               !treat_as_floating_point<_Rep2>::value)
-            >::type* = nullptr)
+                                          !treat_as_floating_point<_Rep2>::value), int> = 0>
+        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
+        explicit duration(const _Rep2& __r)
                 : __rep_(__r) {}
 
     // conversions
-    template <class _Rep2, class _Period2>
-        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
-        duration(const duration<_Rep2, _Period2>& __d,
-            typename enable_if
-            <
-                __no_overflow<_Period2, period>::value && (
+    template <class _Rep2, class _Period2, __enable_if_t<__no_overflow<_Period2, period>::value && (
                                                             treat_as_floating_point<rep>::value ||
                                                             (__no_overflow<_Period2, period>::type::den == 1 &&
-                 !treat_as_floating_point<_Rep2>::value))
-            >::type* = nullptr)
+                                                             !treat_as_floating_point<_Rep2>::value)), int> = 0>
+        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
+        duration(const duration<_Rep2, _Period2>& __d)
                 : __rep_(chrono::duration_cast<duration>(__d).count()) {}
 
     // observer
 
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR rep count() const {return __rep_;}
 
     // arithmetic
 

libcxx/include/__chrono/time_point.h

 private:
     duration __d_;
 
 public:
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX14 time_point() : __d_(duration::zero()) {}
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX14 explicit time_point(const duration& __d) : __d_(__d) {}
 
     // conversions
-    template <class _Duration2>
+    template <class _Duration2, __enable_if_t<is_convertible<_Duration2, duration>::value, int> = 0>
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX14
-    time_point(const time_point<clock, _Duration2>& __t,
-        typename enable_if
-        <
-            is_convertible<_Duration2, duration>::value
-        >::type* = nullptr)
+    time_point(const time_point<clock, _Duration2>& __t)
             : __d_(__t.time_since_epoch()) {}
 
     // observer
 
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX14 duration time_since_epoch() const {return __d_;}
 
     // arithmetic
 

libcxx/include/__iterator/wrap_iter.h

 
 private:
     iterator_type __i_;
 public:
     _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 __wrap_iter() _NOEXCEPT
                 : __i_()
     {
     }
-    template <class _Up> _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14
-        __wrap_iter(const __wrap_iter<_Up>& __u,
-            typename enable_if<is_convertible<_Up, iterator_type>::value>::type* = nullptr) _NOEXCEPT
+    template <class _Up, __enable_if_t<is_convertible<_Up, iterator_type>::value, int> = 0>
+    _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 __wrap_iter(const __wrap_iter<_Up>& __u) _NOEXCEPT
             : __i_(__u.base())
     {
     }
     _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 reference operator*() const _NOEXCEPT
     {
         return *__i_;
     }
     _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pointer operator->() const _NOEXCEPT

libcxx/include/__memory/shared_ptr.h

 
 private:
     element_type*        __ptr_;
     __shared_weak_count* __cntrl_;
 
 public:
     _LIBCPP_INLINE_VISIBILITY
     _LIBCPP_CONSTEXPR weak_ptr() _NOEXCEPT;
-    template<class _Yp> _LIBCPP_INLINE_VISIBILITY weak_ptr(shared_ptr<_Yp> const& __r,
-                   typename enable_if<__compatible_with<_Yp, _Tp>::value, __nat*>::type = 0)
-                        _NOEXCEPT;
+
+    template<class _Yp, __enable_if_t<__compatible_with<_Yp, _Tp>::value, int> = 0>
+    _LIBCPP_INLINE_VISIBILITY weak_ptr(shared_ptr<_Yp> const& __r) _NOEXCEPT;
+
     _LIBCPP_INLINE_VISIBILITY
     weak_ptr(weak_ptr const& __r) _NOEXCEPT;
-    template<class _Yp> _LIBCPP_INLINE_VISIBILITY weak_ptr(weak_ptr<_Yp> const& __r,
-                   typename enable_if<__compatible_with<_Yp, _Tp>::value, __nat*>::type = 0)
-                         _NOEXCEPT;
+
+    template<class _Yp, __enable_if_t<__compatible_with<_Yp, _Tp>::value, int> = 0>
+    _LIBCPP_INLINE_VISIBILITY weak_ptr(weak_ptr<_Yp> const& __r) _NOEXCEPT;
 
     _LIBCPP_INLINE_VISIBILITY
     weak_ptr(weak_ptr&& __r) _NOEXCEPT;
-    template<class _Yp> _LIBCPP_INLINE_VISIBILITY weak_ptr(weak_ptr<_Yp>&& __r,
-                   typename enable_if<__compatible_with<_Yp, _Tp>::value, __nat*>::type = 0)
-                         _NOEXCEPT;
+
+    template<class _Yp, __enable_if_t<__compatible_with<_Yp, _Tp>::value, int> = 0>
+    _LIBCPP_INLINE_VISIBILITY weak_ptr(weak_ptr<_Yp>&& __r) _NOEXCEPT;
+
     _LIBCPP_HIDE_FROM_ABI ~weak_ptr();
 
     _LIBCPP_INLINE_VISIBILITY
     weak_ptr& operator=(weak_ptr const& __r) _NOEXCEPT;
     template<class _Yp, __enable_if_t<__compatible_with<_Yp, _Tp>::value, int> = 0>
         weak_ptr&
         _LIBCPP_INLINE_VISIBILITY
         operator=(weak_ptr<_Yp> const& __r) _NOEXCEPT;
weak_ptr<_Tp>::weak_ptr(weak_ptr const& __r) _NOEXCEPT
     : __ptr_(__r.__ptr_),
       __cntrl_(__r.__cntrl_)
 {
     if (__cntrl_)
         __cntrl_->__add_weak();
 }
 
 template<class _Tp>
-template<class _Yp>
+template<class _Yp, __enable_if_t<__compatible_with<_Yp, _Tp>::value, int> >
 inline
-weak_ptr<_Tp>::weak_ptr(shared_ptr<_Yp> const& __r,
-                        typename enable_if<__compatible_with<_Yp, _Tp>::value, __nat*>::type)
+weak_ptr<_Tp>::weak_ptr(shared_ptr<_Yp> const& __r)
                          _NOEXCEPT
     : __ptr_(__r.__ptr_),
       __cntrl_(__r.__cntrl_)
 {
     if (__cntrl_)
         __cntrl_->__add_weak();
 }
 
 template<class _Tp>
-template<class _Yp>
+template<class _Yp, __enable_if_t<__compatible_with<_Yp, _Tp>::value, int> >
 inline
-weak_ptr<_Tp>::weak_ptr(weak_ptr<_Yp> const& __r,
-                        typename enable_if<__compatible_with<_Yp, _Tp>::value, __nat*>::type)
+weak_ptr<_Tp>::weak_ptr(weak_ptr<_Yp> const& __r)
          _NOEXCEPT
     : __ptr_(__r.__ptr_),
       __cntrl_(__r.__cntrl_)
 {
     if (__cntrl_)
         __cntrl_->__add_weak();
 }
 
 template<class _Tp>
 inline
 weak_ptr<_Tp>::weak_ptr(weak_ptr&& __r) _NOEXCEPT
     : __ptr_(__r.__ptr_),
       __cntrl_(__r.__cntrl_)
 {
     __r.__ptr_ = nullptr;
     __r.__cntrl_ = nullptr;
 }
 
 template<class _Tp>
-template<class _Yp>
+template<class _Yp, __enable_if_t<__compatible_with<_Yp, _Tp>::value, int> >
 inline
-weak_ptr<_Tp>::weak_ptr(weak_ptr<_Yp>&& __r,
-                        typename enable_if<__compatible_with<_Yp, _Tp>::value, __nat*>::type)
+weak_ptr<_Tp>::weak_ptr(weak_ptr<_Yp>&& __r)
          _NOEXCEPT
     : __ptr_(__r.__ptr_),
       __cntrl_(__r.__cntrl_)
 {
     __r.__ptr_ = nullptr;
     __r.__cntrl_ = nullptr;
 }
 

libcxx/include/__memory/unique_ptr.h

 struct _LIBCPP_TEMPLATE_VIS default_delete {
     static_assert(!is_function<_Tp>::value,
                   "default_delete cannot be instantiated for function types");
 #ifndef _LIBCPP_CXX03_LANG
   _LIBCPP_INLINE_VISIBILITY constexpr default_delete() _NOEXCEPT = default;
 #else
   _LIBCPP_INLINE_VISIBILITY default_delete() {}
 #endif
-  template <class _Up>
+  template <class _Up, __enable_if_t<is_convertible<_Up*, _Tp*>::value, int> = 0>
   _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX23 default_delete(
-      const default_delete<_Up>&, typename enable_if<is_convertible<_Up*, _Tp*>::value>::type* = 0) _NOEXCEPT {}
+      const default_delete<_Up>&) _NOEXCEPT {}
 
   _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX23 void operator()(_Tp* __ptr) const _NOEXCEPT {
     static_assert(sizeof(_Tp) >= 0, "cannot delete an incomplete type");
     static_assert(!is_void<_Tp>::value, "cannot delete an incomplete type");
     delete __ptr;
   }
 };
 
public:
   template <class _Up,
             class _Ep,
             class = _EnableIfMoveConvertible<unique_ptr<_Up, _Ep>, _Up>,
             class = _EnableIfDeleterConvertible<_Ep> >
   _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX23 unique_ptr(unique_ptr<_Up, _Ep>&& __u) _NOEXCEPT
       : __ptr_(__u.release(), _VSTD::forward<_Ep>(__u.get_deleter())) {}
 
 #if _LIBCPP_STD_VER <= 14 || defined(_LIBCPP_ENABLE_CXX17_REMOVED_AUTO_PTR)
-  template <class _Up>
+  template <class _Up, __enable_if_t<is_convertible<_Up*, _Tp*>::value &&
+                                     is_same<_Dp, default_delete<_Tp> >::value, int> = 0>
   _LIBCPP_INLINE_VISIBILITY
-  unique_ptr(auto_ptr<_Up>&& __p,
-             typename enable_if<is_convertible<_Up*, _Tp*>::value &&
-                                    is_same<_Dp, default_delete<_Tp> >::value,
-                                __nat>::type = __nat()) _NOEXCEPT
+  unique_ptr(auto_ptr<_Up>&& __p) _NOEXCEPT
       : __ptr_(__p.release(), __value_init_tag()) {}
 #endif
 
   _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX23 unique_ptr& operator=(unique_ptr&& __u) _NOEXCEPT {
     reset(__u.release());
     __ptr_.second() = _VSTD::forward<deleter_type>(__u.get_deleter());
     return *this;
   }

libcxx/include/__random/discard_block_engine.h

explicit discard_block_engine(const _Engine& __e)
         : __e_(__e), __n_(0) {}
 #ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     explicit discard_block_engine(_Engine&& __e)
         : __e_(_VSTD::move(__e)), __n_(0) {}
 #endif // _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     explicit discard_block_engine(result_type __sd) : __e_(__sd), __n_(0) {}
-    template<class _Sseq>
+    template<class _Sseq, __enable_if_t<__is_seed_sequence<_Sseq, discard_block_engine>::value &&
+                                        !is_convertible<_Sseq, _Engine>::value, int> = 0>
         _LIBCPP_INLINE_VISIBILITY
-        explicit discard_block_engine(_Sseq& __q,
-        typename enable_if<__is_seed_sequence<_Sseq, discard_block_engine>::value &&
-                           !is_convertible<_Sseq, _Engine>::value>::type* = 0)
+        explicit discard_block_engine(_Sseq& __q)
         : __e_(__q), __n_(0) {}
     _LIBCPP_INLINE_VISIBILITY
     void seed() {__e_.seed(); __n_ = 0;}
     _LIBCPP_INLINE_VISIBILITY
     void seed(result_type __sd) {__e_.seed(__sd); __n_ = 0;}
     template<class _Sseq, __enable_if_t<__is_seed_sequence<_Sseq, discard_block_engine>::value, int> = 0>
         _LIBCPP_INLINE_VISIBILITY
         void

libcxx/include/__random/independent_bits_engine.h

explicit independent_bits_engine(const _Engine& __e)
         : __e_(__e) {}
 #ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     explicit independent_bits_engine(_Engine&& __e)
         : __e_(_VSTD::move(__e)) {}
 #endif // _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     explicit independent_bits_engine(result_type __sd) : __e_(__sd) {}
-    template<class _Sseq>
+    template<class _Sseq, __enable_if_t<__is_seed_sequence<_Sseq, independent_bits_engine>::value &&
+                                        !is_convertible<_Sseq, _Engine>::value, int> = 0>
         _LIBCPP_INLINE_VISIBILITY
-        explicit independent_bits_engine(_Sseq& __q,
-        typename enable_if<__is_seed_sequence<_Sseq, independent_bits_engine>::value &&
-                           !is_convertible<_Sseq, _Engine>::value>::type* = 0)
+        explicit independent_bits_engine(_Sseq& __q)
          : __e_(__q) {}
     _LIBCPP_INLINE_VISIBILITY
     void seed() {__e_.seed();}
     _LIBCPP_INLINE_VISIBILITY
     void seed(result_type __sd) {__e_.seed(__sd);}
     template<class _Sseq, __enable_if_t<__is_seed_sequence<_Sseq, independent_bits_engine>::value, int> = 0>
         _LIBCPP_INLINE_VISIBILITY
         void

libcxx/include/__random/linear_congruential_engine.h

#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     explicit linear_congruential_engine(result_type __s) { seed(__s); }
 #else
     _LIBCPP_INLINE_VISIBILITY
     explicit linear_congruential_engine(result_type __s = default_seed) {
       seed(__s);
     }
 #endif
-    template<class _Sseq>
+    template<class _Sseq, __enable_if_t<__is_seed_sequence<_Sseq, linear_congruential_engine>::value, int> = 0>
         _LIBCPP_INLINE_VISIBILITY
-        explicit linear_congruential_engine(_Sseq& __q,
-        typename enable_if<__is_seed_sequence<_Sseq, linear_congruential_engine>::value>::type* = 0)
+        explicit linear_congruential_engine(_Sseq& __q)
         {seed(__q);}
     _LIBCPP_INLINE_VISIBILITY
     void seed(result_type __s = default_seed)
         {seed(integral_constant<bool, __m == 0>(),
               integral_constant<bool, __c == 0>(), __s);}
     template<class _Sseq, __enable_if_t<__is_seed_sequence<_Sseq, linear_congruential_engine>::value, int> = 0>
         _LIBCPP_INLINE_VISIBILITY
         void

libcxx/include/__random/mersenne_twister_engine.h

#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     explicit mersenne_twister_engine(result_type __sd) { seed(__sd); }
 #else
     _LIBCPP_INLINE_VISIBILITY
     explicit mersenne_twister_engine(result_type __sd = default_seed) {
       seed(__sd);
     }
 #endif
-    template<class _Sseq>
+    template<class _Sseq, __enable_if_t<__is_seed_sequence<_Sseq, mersenne_twister_engine>::value, int> = 0>
         _LIBCPP_INLINE_VISIBILITY
-        explicit mersenne_twister_engine(_Sseq& __q,
-        typename enable_if<__is_seed_sequence<_Sseq, mersenne_twister_engine>::value>::type* = 0)
+        explicit mersenne_twister_engine(_Sseq& __q)
         {seed(__q);}
     _LIBCPP_HIDE_FROM_ABI void seed(result_type __sd = default_seed);
     template<class _Sseq, __enable_if_t<__is_seed_sequence<_Sseq, mersenne_twister_engine>::value, int> = 0>
         _LIBCPP_INLINE_VISIBILITY
         void
         seed(_Sseq& __q)
             {__seed(__q, integral_constant<unsigned, 1 + (__w - 1) / 32>());}
 

libcxx/include/__random/shuffle_order_engine.h

explicit shuffle_order_engine(const _Engine& __e)
         : __e_(__e) {__init();}
 #ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     explicit shuffle_order_engine(_Engine&& __e)
         : __e_(_VSTD::move(__e)) {__init();}
 #endif // _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     explicit shuffle_order_engine(result_type __sd) : __e_(__sd) {__init();}
-    template<class _Sseq>
+    template<class _Sseq, __enable_if_t<__is_seed_sequence<_Sseq, shuffle_order_engine>::value &&
+                                        !is_convertible<_Sseq, _Engine>::value, int> = 0>
         _LIBCPP_INLINE_VISIBILITY
-        explicit shuffle_order_engine(_Sseq& __q,
-        typename enable_if<__is_seed_sequence<_Sseq, shuffle_order_engine>::value &&
-                           !is_convertible<_Sseq, _Engine>::value>::type* = 0)
+        explicit shuffle_order_engine(_Sseq& __q)
          : __e_(__q) {__init();}
     _LIBCPP_INLINE_VISIBILITY
     void seed() {__e_.seed(); __init();}
     _LIBCPP_INLINE_VISIBILITY
     void seed(result_type __sd) {__e_.seed(__sd); __init();}
     template<class _Sseq, __enable_if_t<__is_seed_sequence<_Sseq, shuffle_order_engine>::value, int> = 0>
         _LIBCPP_INLINE_VISIBILITY
         void

libcxx/include/__random/subtract_with_carry_engine.h

#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     explicit subtract_with_carry_engine(result_type __sd) { seed(__sd); }
 #else
     _LIBCPP_INLINE_VISIBILITY
     explicit subtract_with_carry_engine(result_type __sd = default_seed) {
       seed(__sd);
     }
 #endif
-    template<class _Sseq>
+    template<class _Sseq, __enable_if_t<__is_seed_sequence<_Sseq, subtract_with_carry_engine>::value, int> = 0>
         _LIBCPP_INLINE_VISIBILITY
-        explicit subtract_with_carry_engine(_Sseq& __q,
-        typename enable_if<__is_seed_sequence<_Sseq, subtract_with_carry_engine>::value>::type* = 0)
+        explicit subtract_with_carry_engine(_Sseq& __q)
         {seed(__q);}
     _LIBCPP_INLINE_VISIBILITY
     void seed(result_type __sd = default_seed)
         {seed(__sd, integral_constant<unsigned, 1 + (__w - 1) / 32>());}
     template<class _Sseq, __enable_if_t<__is_seed_sequence<_Sseq, subtract_with_carry_engine>::value, int> = 0>
         _LIBCPP_INLINE_VISIBILITY
         void
         seed(_Sseq& __q)

libcxx/include/__system_error/error_code.h

class _LIBCPP_EXPORTED_FROM_ABI error_code {
   int __val_;
   const error_category* __cat_;
 
 public:
   _LIBCPP_HIDE_FROM_ABI error_code() _NOEXCEPT : __val_(0), __cat_(&system_category()) {}
 
   _LIBCPP_HIDE_FROM_ABI error_code(int __val, const error_category& __cat) _NOEXCEPT : __val_(__val), __cat_(&__cat) {}
 
-  template <class _Ep>
+  template <class _Ep, __enable_if_t<is_error_code_enum<_Ep>::value, int> = 0>
   _LIBCPP_HIDE_FROM_ABI
-  error_code(_Ep __e, typename enable_if<is_error_code_enum<_Ep>::value>::type* = nullptr) _NOEXCEPT {
+  error_code(_Ep __e) _NOEXCEPT {
     using __adl_only::make_error_code;
     *this = make_error_code(__e);
   }
 
   _LIBCPP_HIDE_FROM_ABI void assign(int __val, const error_category& __cat) _NOEXCEPT {
     __val_ = __val;
     __cat_ = &__cat;
   }

libcxx/include/__system_error/error_condition.h

 
 public:
   _LIBCPP_HIDE_FROM_ABI error_condition() _NOEXCEPT : __val_(0), __cat_(&generic_category()) {}
 
   _LIBCPP_HIDE_FROM_ABI error_condition(int __val, const error_category& __cat) _NOEXCEPT
       : __val_(__val),
         __cat_(&__cat) {}
 
-  template <class _Ep>
+  template <class _Ep, __enable_if_t<is_error_condition_enum<_Ep>::value, int> = 0>
   _LIBCPP_HIDE_FROM_ABI
-  error_condition(_Ep __e, typename enable_if<is_error_condition_enum<_Ep>::value>::type* = nullptr) _NOEXCEPT {
+  error_condition(_Ep __e) _NOEXCEPT {
     using __adl_only::make_error_condition;
     *this = make_error_condition(__e);
   }
 
   _LIBCPP_HIDE_FROM_ABI void assign(int __val, const error_category& __cat) _NOEXCEPT {
     __val_ = __val;
     __cat_ = &__cat;
   }

libcxx/include/deque

public:
     typedef _Reference                  reference;
 
     _LIBCPP_HIDE_FROM_ABI __deque_iterator() _NOEXCEPT
 #if _LIBCPP_STD_VER >= 14
      : __m_iter_(nullptr), __ptr_(nullptr)
 #endif
      {}
 
-    template <class _Pp, class _Rp, class _MP>
+    template <class _Pp, class _Rp, class _MP, __enable_if_t<is_convertible<_Pp, pointer>::value, int> = 0>
     _LIBCPP_HIDE_FROM_ABI
-    __deque_iterator(const __deque_iterator<value_type, _Pp, _Rp, _MP, difference_type, _BS>& __it,
-                typename enable_if<is_convertible<_Pp, pointer>::value>::type* = 0) _NOEXCEPT
+    __deque_iterator(const __deque_iterator<value_type, _Pp, _Rp, _MP, difference_type, _BS>& __it) _NOEXCEPT
         : __m_iter_(__it.__m_iter_), __ptr_(__it.__ptr_) {}
 
     _LIBCPP_HIDE_FROM_ABI reference operator*() const {return *__ptr_;}
     _LIBCPP_HIDE_FROM_ABI pointer operator->() const {return __ptr_;}
 
     _LIBCPP_HIDE_FROM_ABI __deque_iterator& operator++()
     {
         if (++__ptr_ - *__m_iter_ == __block_size)
#endif
     _LIBCPP_HIDE_FROM_ABI deque(size_type __n, const value_type& __v, const allocator_type& __a)
         : __map_(__pointer_allocator(__a)), __start_(0), __size_(0, __a)
     {
         __annotate_new(0);
         if (__n > 0)
             __append(__n, __v);
     }
 
-    template <class _InputIter>
-    _LIBCPP_HIDE_FROM_ABI deque(_InputIter __f, _InputIter __l,
-              typename enable_if<__has_input_iterator_category<_InputIter>::value>::type* = 0);
-    template <class _InputIter>
-    _LIBCPP_HIDE_FROM_ABI deque(_InputIter __f, _InputIter __l, const allocator_type& __a,
-              typename enable_if<__has_input_iterator_category<_InputIter>::value>::type* = 0);
+    template <class _InputIter, __enable_if_t<__has_input_iterator_category<_InputIter>::value, int> = 0>
+    _LIBCPP_HIDE_FROM_ABI deque(_InputIter __f, _InputIter __l);
+    template <class _InputIter, __enable_if_t<__has_input_iterator_category<_InputIter>::value, int> = 0>
+    _LIBCPP_HIDE_FROM_ABI deque(_InputIter __f, _InputIter __l, const allocator_type& __a);
 
 #if _LIBCPP_STD_VER >= 23
   template <_ContainerCompatibleRange<_Tp> _Range>
   _LIBCPP_HIDE_FROM_ABI deque(from_range_t, _Range&& __range,
       const allocator_type& __a = allocator_type())
     : __map_(__pointer_allocator(__a)), __start_(0), __size_(0, __a) {
     if constexpr (ranges::forward_range<_Range> || ranges::sized_range<_Range>) {
       __append_with_size(ranges::begin(__range), ranges::distance(__range));
#ifndef _LIBCPP_CXX03_LANG
     deque& operator=(deque&& __c)
         _NOEXCEPT_(__alloc_traits::propagate_on_container_move_assignment::value &&
                    is_nothrow_move_assignable<allocator_type>::value);
 
     _LIBCPP_HIDE_FROM_ABI
     void assign(initializer_list<value_type> __il) {assign(__il.begin(), __il.end());}
 #endif // _LIBCPP_CXX03_LANG
 
-    template <class _InputIter>
-    _LIBCPP_HIDE_FROM_ABI void assign(_InputIter __f, _InputIter __l,
-                    typename enable_if<__has_input_iterator_category<_InputIter>::value &&
-                                      !__has_random_access_iterator_category<_InputIter>::value>::type* = 0);
-    template <class _RAIter>
-    _LIBCPP_HIDE_FROM_ABI void assign(_RAIter __f, _RAIter __l,
-                    typename enable_if<__has_random_access_iterator_category<_RAIter>::value>::type* = 0);
+    template <class _InputIter, __enable_if_t<__has_input_iterator_category<_InputIter>::value &&
+                                              !__has_random_access_iterator_category<_InputIter>::value, int> = 0>
+    _LIBCPP_HIDE_FROM_ABI void assign(_InputIter __f, _InputIter __l);
+    template <class _RAIter, __enable_if_t<__has_random_access_iterator_category<_RAIter>::value, int> = 0>
+    _LIBCPP_HIDE_FROM_ABI void assign(_RAIter __f, _RAIter __l);
 
 #if _LIBCPP_STD_VER >= 23
     template <_ContainerCompatibleRange<_Tp> _Range>
     _LIBCPP_HIDE_FROM_ABI
     void assign_range(_Range&& __range) {
       if constexpr (ranges::random_access_range<_Range>) {
         auto __n = static_cast<size_type>(ranges::distance(__range));
         __assign_with_size_random_access(ranges::begin(__range), __n);
#endif
     _LIBCPP_HIDE_FROM_ABI iterator insert(const_iterator __p, value_type&& __v);
 
     _LIBCPP_HIDE_FROM_ABI
     iterator insert(const_iterator __p, initializer_list<value_type> __il)
         {return insert(__p, __il.begin(), __il.end());}
 #endif // _LIBCPP_CXX03_LANG
     _LIBCPP_HIDE_FROM_ABI iterator insert(const_iterator __p, const value_type& __v);
     _LIBCPP_HIDE_FROM_ABI iterator insert(const_iterator __p, size_type __n, const value_type& __v);
-    template <class _InputIter>
-    _LIBCPP_HIDE_FROM_ABI iterator insert(const_iterator __p, _InputIter __f, _InputIter __l,
-                         typename enable_if<__has_exactly_input_iterator_category<_InputIter>::value>::type* = 0);
-    template <class _ForwardIterator>
-    _LIBCPP_HIDE_FROM_ABI iterator insert(const_iterator __p, _ForwardIterator __f, _ForwardIterator __l,
-                        typename enable_if<__has_exactly_forward_iterator_category<_ForwardIterator>::value>::type* = 0);
-    template <class _BiIter>
-    _LIBCPP_HIDE_FROM_ABI iterator insert(const_iterator __p, _BiIter __f, _BiIter __l,
-                         typename enable_if<__has_bidirectional_iterator_category<_BiIter>::value>::type* = 0);
+    template <class _InputIter, __enable_if_t<__has_exactly_input_iterator_category<_InputIter>::value, int> = 0>
+    _LIBCPP_HIDE_FROM_ABI iterator insert(const_iterator __p, _InputIter __f, _InputIter __l);
+    template <class _ForwardIterator, __enable_if_t<__has_exactly_forward_iterator_category<_ForwardIterator>::value, int> = 0>
+    _LIBCPP_HIDE_FROM_ABI iterator insert(const_iterator __p, _ForwardIterator __f, _ForwardIterator __l);
+    template <class _BiIter, __enable_if_t<__has_bidirectional_iterator_category<_BiIter>::value, int> = 0>
+    _LIBCPP_HIDE_FROM_ABI iterator insert(const_iterator __p, _BiIter __f, _BiIter __l);
 
 #if _LIBCPP_STD_VER >= 23
     template <_ContainerCompatibleRange<_Tp> _Range>
     _LIBCPP_HIDE_FROM_ABI
     iterator insert_range(const_iterator __position, _Range&& __range) {
       if constexpr (ranges::bidirectional_range<_Range>) {
         auto __n = static_cast<size_type>(ranges::distance(__range));
         return __insert_bidirectional(__position, ranges::begin(__range), ranges::end(__range), __n);
#endif // _LIBCPP_VERIFY_ASAN_DEQUE_ANNOTATIONS
 
     template <class _BiIter, class _Sentinel>
     _LIBCPP_HIDE_FROM_ABI
     iterator __insert_bidirectional(const_iterator __p, _BiIter __f, _Sentinel __sent, size_type __n);
     template <class _BiIter>
     _LIBCPP_HIDE_FROM_ABI
     iterator __insert_bidirectional(const_iterator __p, _BiIter __f, _BiIter __l, size_type __n);
 
-    template <class _InpIter>
-    _LIBCPP_HIDE_FROM_ABI void __append(_InpIter __f, _InpIter __l,
-                 typename enable_if<__has_exactly_input_iterator_category<_InpIter>::value>::type* = 0);
-    template <class _ForIter>
-    _LIBCPP_HIDE_FROM_ABI void __append(_ForIter __f, _ForIter __l,
-                      typename enable_if<__has_forward_iterator_category<_ForIter>::value>::type* = 0);
+    template <class _InpIter, __enable_if_t<__has_exactly_input_iterator_category<_InpIter>::value, int> = 0>
+    _LIBCPP_HIDE_FROM_ABI void __append(_InpIter __f, _InpIter __l);
+    template <class _ForIter, __enable_if_t<__has_forward_iterator_category<_ForIter>::value, int> = 0>
+    _LIBCPP_HIDE_FROM_ABI void __append(_ForIter __f, _ForIter __l);
 
     template <class _InputIterator>
     _LIBCPP_HIDE_FROM_ABI void __append_with_size(_InputIterator __from, size_type __n);
     template <class _InputIterator, class _Sentinel>
     _LIBCPP_HIDE_FROM_ABI void __append_with_sentinel(_InputIterator __f, _Sentinel __l);
 
     _LIBCPP_HIDE_FROM_ABI void __append(size_type __n);
     _LIBCPP_HIDE_FROM_ABI void __append(size_type __n, const value_type& __v);
deque<_Tp, _Allocator>::deque(size_type __n, const value_type& __v)
     : __start_(0), __size_(0, __default_init_tag())
 {
     __annotate_new(0);
     if (__n > 0)
         __append(__n, __v);
 }
 
 template <class _Tp, class _Allocator>
-template <class _InputIter>
-deque<_Tp, _Allocator>::deque(_InputIter __f, _InputIter __l,
-              typename enable_if<__has_input_iterator_category<_InputIter>::value>::type*)
+template <class _InputIter, __enable_if_t<__has_input_iterator_category<_InputIter>::value, int> >
+deque<_Tp, _Allocator>::deque(_InputIter __f, _InputIter __l)
     : __start_(0), __size_(0, __default_init_tag())
 {
     __annotate_new(0);
     __append(__f, __l);
 }
 
 template <class _Tp, class _Allocator>
-template <class _InputIter>
-deque<_Tp, _Allocator>::deque(_InputIter __f, _InputIter __l, const allocator_type& __a,
-              typename enable_if<__has_input_iterator_category<_InputIter>::value>::type*)
+template <class _InputIter, __enable_if_t<__has_input_iterator_category<_InputIter>::value, int> >
+deque<_Tp, _Allocator>::deque(_InputIter __f, _InputIter __l, const allocator_type& __a)
     : __map_(__pointer_allocator(__a)), __start_(0), __size_(0, __a)
 {
     __annotate_new(0);
     __append(__f, __l);
 }
 
 template <class _Tp, class _Allocator>
 deque<_Tp, _Allocator>::deque(const deque& __c)
deque<_Tp, _Allocator>::__move_assign(deque& __c, true_type)
     clear();
     shrink_to_fit();
     __move_assign(__c);
 }
 
 #endif // _LIBCPP_CXX03_LANG
 
 template <class _Tp, class _Allocator>
-template <class _InputIter>
+template <class _InputIter, __enable_if_t<__has_input_iterator_category<_InputIter>::value &&
+                                          !__has_random_access_iterator_category<_InputIter>::value, int> >
 void
-deque<_Tp, _Allocator>::assign(_InputIter __f, _InputIter __l,
-                               typename enable_if<__has_input_iterator_category<_InputIter>::value &&
-                                                 !__has_random_access_iterator_category<_InputIter>::value>::type*)
+deque<_Tp, _Allocator>::assign(_InputIter __f, _InputIter __l)
 {
   __assign_with_sentinel(__f, __l);
 }
 
 template <class _Tp, class _Allocator>
 template <class _Iterator, class _Sentinel>
 _LIBCPP_HIDE_FROM_ABI
 void deque<_Tp, _Allocator>::__assign_with_sentinel(_Iterator __f, _Sentinel __l) {
     iterator __i = begin();
     iterator __e = end();
     for (; __f != __l && __i != __e; ++__f, (void) ++__i)
         *__i = *__f;
     if (__f != __l)
         __append_with_sentinel(std::move(__f), std::move(__l));
     else
         __erase_to_end(__i);
 }
 
 template <class _Tp, class _Allocator>
-template <class _RAIter>
+template <class _RAIter, __enable_if_t<__has_random_access_iterator_category<_RAIter>::value, int> >
 void
-deque<_Tp, _Allocator>::assign(_RAIter __f, _RAIter __l,
-                               typename enable_if<__has_random_access_iterator_category<_RAIter>::value>::type*)
+deque<_Tp, _Allocator>::assign(_RAIter __f, _RAIter __l)
 {
   __assign_with_size_random_access(__f, __l - __f);
 }
 
 template <class _Tp, class _Allocator>
 template <class _RandomAccessIterator>
 _LIBCPP_HIDE_FROM_ABI
 void deque<_Tp, _Allocator>::__assign_with_size_random_access(_RandomAccessIterator __f, difference_type __n) {
else
                 __old_end = __move_backward_and_check(__old_end - __de, __oen, __old_end, __vt);
             _VSTD::fill_n(__old_end - __n, __n, *__vt);
         }
     }
     return begin() + __pos;
 }
 
 template <class _Tp, class _Allocator>
-template <class _InputIter>
+template <class _InputIter, __enable_if_t<__has_exactly_input_iterator_category<_InputIter>::value, int> >
 typename deque<_Tp, _Allocator>::iterator
-deque<_Tp, _Allocator>::insert(const_iterator __p, _InputIter __f, _InputIter __l,
-                               typename enable_if<__has_exactly_input_iterator_category<_InputIter>::value>::type*)
+deque<_Tp, _Allocator>::insert(const_iterator __p, _InputIter __f, _InputIter __l)
 {
   return __insert_with_sentinel(__p, __f, __l);
 }
 
 template <class _Tp, class _Allocator>
 template <class _Iterator, class _Sentinel>
 _LIBCPP_HIDE_FROM_ABI
 typename deque<_Tp, _Allocator>::iterator
 deque<_Tp, _Allocator>::__insert_with_sentinel(const_iterator __p, _Iterator __f, _Sentinel __l) {
     __split_buffer<value_type, allocator_type&> __buf(__alloc());
     __buf.__construct_at_end_with_sentinel(std::move(__f), std::move(__l));
     typedef typename __split_buffer<value_type, allocator_type&>::iterator __bi;
     return insert(__p, move_iterator<__bi>(__buf.begin()), move_iterator<__bi>(__buf.end()));
 }
 
 template <class _Tp, class _Allocator>
-template <class _ForwardIterator>
+template <class _ForwardIterator, __enable_if_t<__has_exactly_forward_iterator_category<_ForwardIterator>::value, int> >
 typename deque<_Tp, _Allocator>::iterator
-deque<_Tp, _Allocator>::insert(const_iterator __p, _ForwardIterator __f, _ForwardIterator __l,
-                               typename enable_if<__has_exactly_forward_iterator_category<_ForwardIterator>::value>::type*)
+deque<_Tp, _Allocator>::insert(const_iterator __p, _ForwardIterator __f, _ForwardIterator __l)
 {
   return __insert_with_size(__p, __f, std::distance(__f, __l));
 }
 
 template <class _Tp, class _Allocator>
 template <class _Iterator>
 _LIBCPP_HIDE_FROM_ABI
 typename deque<_Tp, _Allocator>::iterator
 deque<_Tp, _Allocator>::__insert_with_size(const_iterator __p, _Iterator __f, size_type __n) {
     __split_buffer<value_type, allocator_type&> __buf(__n, 0, __alloc());
     __buf.__construct_at_end_with_size(__f, __n);
     typedef typename __split_buffer<value_type, allocator_type&>::iterator __fwd;
     return insert(__p, move_iterator<__fwd>(__buf.begin()), move_iterator<__fwd>(__buf.end()));
 }
 
 template <class _Tp, class _Allocator>
-template <class _BiIter>
+template <class _BiIter, __enable_if_t<__has_bidirectional_iterator_category<_BiIter>::value, int> >
 typename deque<_Tp, _Allocator>::iterator
-deque<_Tp, _Allocator>::insert(const_iterator __p, _BiIter __f, _BiIter __l,
-                               typename enable_if<__has_bidirectional_iterator_category<_BiIter>::value>::type*)
+deque<_Tp, _Allocator>::insert(const_iterator __p, _BiIter __f, _BiIter __l)
 {
   return __insert_bidirectional(__p, __f, __l, std::distance(__f, __l));
 }
 
 template <class _Tp, class _Allocator>
 template <class _BiIter, class _Sentinel>
 _LIBCPP_HIDE_FROM_ABI
 typename deque<_Tp, _Allocator>::iterator
else
                 __old_end = _VSTD::move_backward(__old_end - __de, __oen, __old_end);
             _VSTD::copy_backward(__f, __m, __old_end);
         }
     }
     return begin() + __pos;
 }
 
 template <class _Tp, class _Allocator>
-template <class _InpIter>
+template <class _InpIter, __enable_if_t<__has_exactly_input_iterator_category<_InpIter>::value, int> >
 void
-deque<_Tp, _Allocator>::__append(_InpIter __f, _InpIter __l,
-                                 typename enable_if<__has_exactly_input_iterator_category<_InpIter>::value>::type*)
+deque<_Tp, _Allocator>::__append(_InpIter __f, _InpIter __l)
 {
   __append_with_sentinel(__f, __l);
 }
 
 template <class _Tp, class _Allocator>
 template <class _InputIterator, class _Sentinel>
 _LIBCPP_HIDE_FROM_ABI
 void deque<_Tp, _Allocator>::__append_with_sentinel(_InputIterator __f, _Sentinel __l) {
     for (; __f != __l; ++__f)
 #ifdef _LIBCPP_CXX03_LANG
         push_back(*__f);
 #else
         emplace_back(*__f);
 #endif
 }
 
 template <class _Tp, class _Allocator>
-template <class _ForIter>
+template <class _ForIter, __enable_if_t<__has_forward_iterator_category<_ForIter>::value, int> >
 void
-deque<_Tp, _Allocator>::__append(_ForIter __f, _ForIter __l,
-                                 typename enable_if<__has_forward_iterator_category<_ForIter>::value>::type*)
+deque<_Tp, _Allocator>::__append(_ForIter __f, _ForIter __l)
 {
     __append_with_size(__f, std::distance(__f, __l));
 }
 
 template <class _Tp, class _Allocator>
 template <class _InputIterator>
 _LIBCPP_HIDE_FROM_ABI
 void deque<_Tp, _Allocator>::__append_with_size(_InputIterator __f, size_type __n) {

libcxx/include/vector

public:
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 ~vector() { __destroy_vector(*this)(); }
 
     _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 explicit vector(size_type __n);
 #if _LIBCPP_STD_VER >= 14
     _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 explicit vector(size_type __n, const allocator_type& __a);
 #endif
     _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 vector(size_type __n, const value_type& __v);
     _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 vector(size_type __n, const value_type& __v, const allocator_type& __a);
-    template <class _InputIterator>
-    _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 vector(_InputIterator __first, _InputIterator __last,
-               typename enable_if<__has_exactly_input_iterator_category<_InputIterator>::value>::type* = 0);
-    template <class _InputIterator>
-    _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 vector(_InputIterator __first, _InputIterator __last, const allocator_type& __a,
-               typename enable_if<__has_exactly_input_iterator_category<_InputIterator>::value>::type* = 0);
-    template <class _ForwardIterator>
-    _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 vector(_ForwardIterator __first, _ForwardIterator __last,
-               typename enable_if<__has_forward_iterator_category<_ForwardIterator>::value>::type* = 0);
-    template <class _ForwardIterator>
-    _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 vector(_ForwardIterator __first, _ForwardIterator __last, const allocator_type& __a,
-               typename enable_if<__has_forward_iterator_category<_ForwardIterator>::value>::type* = 0);
+    template <class _InputIterator, __enable_if_t<__has_exactly_input_iterator_category<_InputIterator>::value, int> = 0>
+    _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 vector(_InputIterator __first, _InputIterator __last);
+    template <class _InputIterator, __enable_if_t<__has_exactly_input_iterator_category<_InputIterator>::value, int> = 0>
+    _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 vector(_InputIterator __first, _InputIterator __last, const allocator_type& __a);
+    template <class _ForwardIterator, __enable_if_t<__has_forward_iterator_category<_ForwardIterator>::value, int> = 0>
+    _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 vector(_ForwardIterator __first, _ForwardIterator __last);
+    template <class _ForwardIterator, __enable_if_t<__has_forward_iterator_category<_ForwardIterator>::value, int> = 0>
+    _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 vector(_ForwardIterator __first, _ForwardIterator __last, const allocator_type& __a);
 
 #if _LIBCPP_STD_VER >= 23
     template <_ContainerCompatibleRange<bool> _Range>
     _LIBCPP_HIDE_FROM_ABI constexpr
     vector(from_range_t, _Range&& __range, const allocator_type& __a = allocator_type())
     : __begin_(nullptr),
       __size_(0),
       __cap_alloc_(0, static_cast<__storage_allocator>(__a)) {
vector<bool, _Allocator>::vector(size_type __n, const value_type& __x, const allocator_type& __a)
     if (__n > 0)
     {
         __vallocate(__n);
         __construct_at_end(__n, __x);
     }
 }
 
 template <class _Allocator>
-template <class _InputIterator>
+template <class _InputIterator, __enable_if_t<__has_exactly_input_iterator_category<_InputIterator>::value, int> >
 _LIBCPP_CONSTEXPR_SINCE_CXX20
-vector<bool, _Allocator>::vector(_InputIterator __first, _InputIterator __last,
-       typename enable_if<__has_exactly_input_iterator_category<_InputIterator>::value>::type*)
+vector<bool, _Allocator>::vector(_InputIterator __first, _InputIterator __last)
     : __begin_(nullptr),
       __size_(0),
       __cap_alloc_(0, __default_init_tag())
 {
   __init_with_sentinel(__first, __last);
 }
 
 template <class _Allocator>
-template <class _InputIterator>
+template <class _InputIterator, __enable_if_t<__has_exactly_input_iterator_category<_InputIterator>::value, int> >
 _LIBCPP_CONSTEXPR_SINCE_CXX20
-vector<bool, _Allocator>::vector(_InputIterator __first, _InputIterator __last, const allocator_type& __a,
-       typename enable_if<__has_exactly_input_iterator_category<_InputIterator>::value>::type*)
+vector<bool, _Allocator>::vector(_InputIterator __first, _InputIterator __last, const allocator_type& __a)
     : __begin_(nullptr),
       __size_(0),
       __cap_alloc_(0, static_cast<__storage_allocator>(__a))
 {
   __init_with_sentinel(__first, __last);
 }
 
 template <class _Allocator>
-template <class _ForwardIterator>
+template <class _ForwardIterator, __enable_if_t<__has_forward_iterator_category<_ForwardIterator>::value, int> >
 _LIBCPP_CONSTEXPR_SINCE_CXX20
-vector<bool, _Allocator>::vector(_ForwardIterator __first, _ForwardIterator __last,
-                                typename enable_if<__has_forward_iterator_category<_ForwardIterator>::value>::type*)
+vector<bool, _Allocator>::vector(_ForwardIterator __first, _ForwardIterator __last)
     : __begin_(nullptr),
       __size_(0),
       __cap_alloc_(0, __default_init_tag())
 {
   auto __n = static_cast<size_type>(std::distance(__first, __last));
   __init_with_size(__first, __last, __n);
 }
 
 template <class _Allocator>
-template <class _ForwardIterator>
+template <class _ForwardIterator, __enable_if_t<__has_forward_iterator_category<_ForwardIterator>::value, int> >
 _LIBCPP_CONSTEXPR_SINCE_CXX20
-vector<bool, _Allocator>::vector(_ForwardIterator __first, _ForwardIterator __last, const allocator_type& __a,
-                                typename enable_if<__has_forward_iterator_category<_ForwardIterator>::value>::type*)
+vector<bool, _Allocator>::vector(_ForwardIterator __first, _ForwardIterator __last, const allocator_type& __a)
     : __begin_(nullptr),
       __size_(0),
       __cap_alloc_(0, static_cast<__storage_allocator>(__a))
 {
   auto __n = static_cast<size_type>(std::distance(__first, __last));
   __init_with_size(__first, __last, __n);
 }