libstdc++: Add missing bits of P0896R4 pertaining to [back|front]_insert_iterator

This adds some missing pieces of the Ranges TS that make back_insert_iterator and
front_insert_iterator conform to the new output_iterator requirements.

It also fixes a bug in ranges::__copy_or_move and
ranges::__copy_or_move_backward in which we were inspecting the iter_value_t of
the output iterator, but iterators such as back_insert_iterator and
front_insert_iterator whose value_type is defined to be void do not have an
iter_value_t according to [readable.traits] p4.  The entire __use_memmove
condition can probably be refactored, but the simplest fix for now is to inspect
the iterator_traits of the output iterator instead.

libstdc++-v3/ChangeLog:

	PR libstdc++/93884
	* include/bits/ranges_algobase.h (__copy_or_move,
	__copy_or_move_backward): Don't inspect the iter_value_t of the output
	iterator, instead inspect its iterator_traits directly.
	* include/bits/stl_iterator.h (back_insert_iterator::container):
	Conditionally initialize.
	(back_insert_iterator::difference_type): Conditionally define.
	(back_insert_iterator::back_insert_iterator): Conditionally define this
	default constructor.
	(front_insert_iterator::container): Conditionally initialize.
	(front_insert_iterator::difference_type): Conditionally define.
	(front_insert_iterator::front_insert_iterator): Conditionally define
	this default constructor.
---
 libstdc++-v3/include/bits/ranges_algobase.h   |  4 +-
 libstdc++-v3/include/bits/stl_iterator.h      | 22 ++++++++++
 .../back_insert_iterator/pr93884.C            | 44 +++++++++++++++++++
 .../front_insert_iterator/pr93884.C           | 44 +++++++++++++++++++
 4 files changed, 112 insertions(+), 2 deletions(-)
 create mode 100644 libstdc++-v3/testsuite/24_iterators/back_insert_iterator/pr93884.C
 create mode 100644 libstdc++-v3/testsuite/24_iterators/front_insert_iterator/pr93884.C

ZOn Mon, 24 Feb 2020, Patrick Palka wrote:

> This adds some missing pieces of the Ranges TS that make back_insert_iterator and
> front_insert_iterator conform to the new output_iterator requirements.
> 
> It also fixes a bug in ranges::__copy_or_move and
> ranges::__copy_or_move_backward in which we were inspecting the iter_value_t of
> the output iterator, but iterators such as back_insert_iterator and
> front_insert_iterator whose value_type is defined to be void do not have an
> iter_value_t according to [readable.traits] p4.  The entire __use_memmove
> condition can probably be refactored, but the simplest fix for now is to inspect
> the iterator_traits of the output iterator instead.
> 
> libstdc++-v3/ChangeLog:
> 
> 	PR libstdc++/93884
> 	* include/bits/ranges_algobase.h (__copy_or_move,
> 	__copy_or_move_backward): Don't inspect the iter_value_t of the output
> 	iterator, instead inspect its iterator_traits directly.
> 	* include/bits/stl_iterator.h (back_insert_iterator::container):
> 	Conditionally initialize.
> 	(back_insert_iterator::difference_type): Conditionally define.
> 	(back_insert_iterator::back_insert_iterator): Conditionally define this
> 	default constructor.
> 	(front_insert_iterator::container): Conditionally initialize.
> 	(front_insert_iterator::difference_type): Conditionally define.
> 	(front_insert_iterator::front_insert_iterator): Conditionally define
> 	this default constructor.
> ---
>  libstdc++-v3/include/bits/ranges_algobase.h   |  4 +-
>  libstdc++-v3/include/bits/stl_iterator.h      | 22 ++++++++++
>  .../back_insert_iterator/pr93884.C            | 44 +++++++++++++++++++
>  .../front_insert_iterator/pr93884.C           | 44 +++++++++++++++++++
>  4 files changed, 112 insertions(+), 2 deletions(-)
>  create mode 100644 libstdc++-v3/testsuite/24_iterators/back_insert_iterator/pr93884.C
>  create mode 100644 libstdc++-v3/testsuite/24_iterators/front_insert_iterator/pr93884.C
> 
> diff --git a/libstdc++-v3/include/bits/ranges_algobase.h b/libstdc++-v3/include/bits/ranges_algobase.h
> index 807822e99c8..739424e1a2d 100644
> --- a/libstdc++-v3/include/bits/ranges_algobase.h
> +++ b/libstdc++-v3/include/bits/ranges_algobase.h
> @@ -249,7 +249,7 @@ namespace ranges
>        else if constexpr (sized_sentinel_for<_Sent, _Iter>)
>  	{
>  	  using _ValueTypeI = iter_value_t<_Iter>;
> -	  using _ValueTypeO = iter_value_t<_Out>;
> +	  using _ValueTypeO = iterator_traits<_Out>::value_type;
>  	  constexpr bool __use_memmove
>  	    = (is_trivially_copyable_v<_ValueTypeI>
>  	       && is_same_v<_ValueTypeI, _ValueTypeO>
> @@ -386,7 +386,7 @@ namespace ranges
>        else if constexpr (sized_sentinel_for<_Sent, _Iter>)
>  	{
>  	  using _ValueTypeI = iter_value_t<_Iter>;
> -	  using _ValueTypeO = iter_value_t<_Out>;
> +	  using _ValueTypeO = iterator_traits<_Out>::value_type;
>  	  constexpr bool __use_memmove
>  	    = (is_trivially_copyable_v<_ValueTypeI>
>  	       && is_same_v<_ValueTypeI, _ValueTypeO>
> diff --git a/libstdc++-v3/include/bits/stl_iterator.h b/libstdc++-v3/include/bits/stl_iterator.h
> index 372df223113..0f2742ae4cf 100644
> --- a/libstdc++-v3/include/bits/stl_iterator.h
> +++ b/libstdc++-v3/include/bits/stl_iterator.h
> @@ -496,11 +496,22 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>      : public iterator<output_iterator_tag, void, void, void, void>
>      {
>      protected:
> +#if __cplusplus > 201703L
> +      _Container* container = nullptr;
> +#else
>        _Container* container;
> +#endif

Just noticed the order of this conditional is inconsistent with ...

>  
>      public:
>        /// A nested typedef for the type of whatever container you used.
>        typedef _Container          container_type;
> +#if __cplusplus > 201703L
> +      using difference_type = ptrdiff_t;
> +#endif
> +
> +#if __cplusplus > 201703L
> +      constexpr back_insert_iterator() noexcept = default;
> +#endif
>  
>        /// The only way to create this %iterator is with a container.
>        explicit
> @@ -588,11 +599,22 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>      : public iterator<output_iterator_tag, void, void, void, void>
>      {
>      protected:
> +#if __cplusplus <= 201703L
>        _Container* container;
> +#else
> +      _Container* container = nullptr;
> +#endif

... this one.  Consider this fixed so that both conditionals are
__cplusplus <= 201703L, specifying the pre-C++20 version of the code
first.

On 24/02/20 08:29 -0500, Patrick Palka wrote:
>This adds some missing pieces of the Ranges TS that make back_insert_iterator and
>front_insert_iterator conform to the new output_iterator requirements.
>
>It also fixes a bug in ranges::__copy_or_move and
>ranges::__copy_or_move_backward in which we were inspecting the iter_value_t of
>the output iterator, but iterators such as back_insert_iterator and
>front_insert_iterator whose value_type is defined to be void do not have an
>iter_value_t according to [readable.traits] p4.  The entire __use_memmove
>condition can probably be refactored, but the simplest fix for now is to inspect
>the iterator_traits of the output iterator instead.
>
>libstdc++-v3/ChangeLog:
>
>	PR libstdc++/93884
>	* include/bits/ranges_algobase.h (__copy_or_move,
>	__copy_or_move_backward): Don't inspect the iter_value_t of the output
>	iterator, instead inspect its iterator_traits directly.
>	* include/bits/stl_iterator.h (back_insert_iterator::container):
>	Conditionally initialize.
>	(back_insert_iterator::difference_type): Conditionally define.
>	(back_insert_iterator::back_insert_iterator): Conditionally define this
>	default constructor.
>	(front_insert_iterator::container): Conditionally initialize.
>	(front_insert_iterator::difference_type): Conditionally define.
>	(front_insert_iterator::front_insert_iterator): Conditionally define
>	this default constructor.
>---
> libstdc++-v3/include/bits/ranges_algobase.h   |  4 +-
> libstdc++-v3/include/bits/stl_iterator.h      | 22 ++++++++++
> .../back_insert_iterator/pr93884.C            | 44 +++++++++++++++++++
> .../front_insert_iterator/pr93884.C           | 44 +++++++++++++++++++
> 4 files changed, 112 insertions(+), 2 deletions(-)
> create mode 100644 libstdc++-v3/testsuite/24_iterators/back_insert_iterator/pr93884.C
> create mode 100644 libstdc++-v3/testsuite/24_iterators/front_insert_iterator/pr93884.C
>
>diff --git a/libstdc++-v3/include/bits/ranges_algobase.h b/libstdc++-v3/include/bits/ranges_algobase.h
>index 807822e99c8..739424e1a2d 100644
>--- a/libstdc++-v3/include/bits/ranges_algobase.h
>+++ b/libstdc++-v3/include/bits/ranges_algobase.h
>@@ -249,7 +249,7 @@ namespace ranges
>       else if constexpr (sized_sentinel_for<_Sent, _Iter>)
> 	{
> 	  using _ValueTypeI = iter_value_t<_Iter>;
>-	  using _ValueTypeO = iter_value_t<_Out>;
>+	  using _ValueTypeO = iterator_traits<_Out>::value_type;

I think this will fail to compile with Clang, because it needs
'typename' there.

> 	  constexpr bool __use_memmove
> 	    = (is_trivially_copyable_v<_ValueTypeI>
> 	       && is_same_v<_ValueTypeI, _ValueTypeO>
>@@ -386,7 +386,7 @@ namespace ranges
>       else if constexpr (sized_sentinel_for<_Sent, _Iter>)
> 	{
> 	  using _ValueTypeI = iter_value_t<_Iter>;
>-	  using _ValueTypeO = iter_value_t<_Out>;
>+	  using _ValueTypeO = iterator_traits<_Out>::value_type;

Same here.

On Mon, 24 Feb 2020, Jonathan Wakely wrote:

> On 24/02/20 08:29 -0500, Patrick Palka wrote:
> > This adds some missing pieces of the Ranges TS that make
> > back_insert_iterator and
> > front_insert_iterator conform to the new output_iterator requirements.
> > 
> > It also fixes a bug in ranges::__copy_or_move and
> > ranges::__copy_or_move_backward in which we were inspecting the iter_value_t
> > of
> > the output iterator, but iterators such as back_insert_iterator and
> > front_insert_iterator whose value_type is defined to be void do not have an
> > iter_value_t according to [readable.traits] p4.  The entire __use_memmove
> > condition can probably be refactored, but the simplest fix for now is to
> > inspect
> > the iterator_traits of the output iterator instead.
> > 
> > libstdc++-v3/ChangeLog:
> > 
> > 	PR libstdc++/93884
> > 	* include/bits/ranges_algobase.h (__copy_or_move,
> > 	__copy_or_move_backward): Don't inspect the iter_value_t of the output
> > 	iterator, instead inspect its iterator_traits directly.
> > 	* include/bits/stl_iterator.h (back_insert_iterator::container):
> > 	Conditionally initialize.
> > 	(back_insert_iterator::difference_type): Conditionally define.
> > 	(back_insert_iterator::back_insert_iterator): Conditionally define
> > this
> > 	default constructor.
> > 	(front_insert_iterator::container): Conditionally initialize.
> > 	(front_insert_iterator::difference_type): Conditionally define.
> > 	(front_insert_iterator::front_insert_iterator): Conditionally define
> > 	this default constructor.
> > ---
> > libstdc++-v3/include/bits/ranges_algobase.h   |  4 +-
> > libstdc++-v3/include/bits/stl_iterator.h      | 22 ++++++++++
> > .../back_insert_iterator/pr93884.C            | 44 +++++++++++++++++++
> > .../front_insert_iterator/pr93884.C           | 44 +++++++++++++++++++
> > 4 files changed, 112 insertions(+), 2 deletions(-)
> > create mode 100644
> > libstdc++-v3/testsuite/24_iterators/back_insert_iterator/pr93884.C
> > create mode 100644
> > libstdc++-v3/testsuite/24_iterators/front_insert_iterator/pr93884.C
> > 
> > diff --git a/libstdc++-v3/include/bits/ranges_algobase.h
> > b/libstdc++-v3/include/bits/ranges_algobase.h
> > index 807822e99c8..739424e1a2d 100644
> > --- a/libstdc++-v3/include/bits/ranges_algobase.h
> > +++ b/libstdc++-v3/include/bits/ranges_algobase.h
> > @@ -249,7 +249,7 @@ namespace ranges
> >       else if constexpr (sized_sentinel_for<_Sent, _Iter>)
> > 	{
> > 	  using _ValueTypeI = iter_value_t<_Iter>;
> > -	  using _ValueTypeO = iter_value_t<_Out>;
> > +	  using _ValueTypeO = iterator_traits<_Out>::value_type;
> 
> I think this will fail to compile with Clang, because it needs
> 'typename' there.
> 
> > 	  constexpr bool __use_memmove
> > 	    = (is_trivially_copyable_v<_ValueTypeI>
> > 	       && is_same_v<_ValueTypeI, _ValueTypeO>
> > @@ -386,7 +386,7 @@ namespace ranges
> >       else if constexpr (sized_sentinel_for<_Sent, _Iter>)
> > 	{
> > 	  using _ValueTypeI = iter_value_t<_Iter>;
> > -	  using _ValueTypeO = iter_value_t<_Out>;
> > +	  using _ValueTypeO = iterator_traits<_Out>::value_type;
> 
> Same here.

Ah right... Here's v2 of the patch that adds typename to those two
aliases and fixes the file extensions on the tests.

-- >8 --

libstdc++-v3/ChangeLog:

	PR libstdc++/93884
	* include/bits/ranges_algobase.h (__copy_or_move,
	__copy_or_move_backward): Don't inspect the iter_value_t of the output
	iterator, instead inspect its iterator_traits directly.
	* include/bits/stl_iterator.h (back_insert_iterator::container):
	Conditionally initialize.
	(back_insert_iterator::difference_type): Conditionally define.
	(back_insert_iterator::back_insert_iterator): Conditionally define this
	default constructor.
	(front_insert_iterator::container): Conditionally initialize.
	(front_insert_iterator::difference_type): Conditionally define.
	(front_insert_iterator::front_insert_iterator): Conditionally define
	this default constructor.
	* 24_iterators/back_insert_iterator/pr93884.cc: New test.
	* 24_iterators/front_insert_iterator/pr93884.cc: New test.
---
 libstdc++-v3/include/bits/ranges_algobase.h   |  4 +-
 libstdc++-v3/include/bits/stl_iterator.h      | 22 ++++++++++
 .../back_insert_iterator/pr93884.cc           | 44 +++++++++++++++++++
 .../front_insert_iterator/pr93884.cc          | 44 +++++++++++++++++++
 4 files changed, 112 insertions(+), 2 deletions(-)
 create mode 100644 libstdc++-v3/testsuite/24_iterators/back_insert_iterator/pr93884.cc
 create mode 100644 libstdc++-v3/testsuite/24_iterators/front_insert_iterator/pr93884.cc

diff --git a/libstdc++-v3/include/bits/ranges_algobase.h b/libstdc++-v3/include/bits/ranges_algobase.h
index 807822e99c8..73f0205ba7f 100644
--- a/libstdc++-v3/include/bits/ranges_algobase.h
+++ b/libstdc++-v3/include/bits/ranges_algobase.h
@@ -249,7 +249,7 @@ namespace ranges
       else if constexpr (sized_sentinel_for<_Sent, _Iter>)
 	{
 	  using _ValueTypeI = iter_value_t<_Iter>;
-	  using _ValueTypeO = iter_value_t<_Out>;
+	  using _ValueTypeO = typename iterator_traits<_Out>::value_type;
 	  constexpr bool __use_memmove
 	    = (is_trivially_copyable_v<_ValueTypeI>
 	       && is_same_v<_ValueTypeI, _ValueTypeO>
@@ -386,7 +386,7 @@ namespace ranges
       else if constexpr (sized_sentinel_for<_Sent, _Iter>)
 	{
 	  using _ValueTypeI = iter_value_t<_Iter>;
-	  using _ValueTypeO = iter_value_t<_Out>;
+	  using _ValueTypeO = typename iterator_traits<_Out>::value_type;
 	  constexpr bool __use_memmove
 	    = (is_trivially_copyable_v<_ValueTypeI>
 	       && is_same_v<_ValueTypeI, _ValueTypeO>
diff --git a/libstdc++-v3/include/bits/stl_iterator.h b/libstdc++-v3/include/bits/stl_iterator.h
index 372df223113..caaa8c483b8 100644
--- a/libstdc++-v3/include/bits/stl_iterator.h
+++ b/libstdc++-v3/include/bits/stl_iterator.h
@@ -496,11 +496,22 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     : public iterator<output_iterator_tag, void, void, void, void>
     {
     protected:
+#if __cplusplus <= 201703L
       _Container* container;
+#else
+      _Container* container = nullptr;
+#endif
 
     public:
       /// A nested typedef for the type of whatever container you used.
       typedef _Container          container_type;
+#if __cplusplus > 201703L
+      using difference_type = ptrdiff_t;
+#endif
+
+#if __cplusplus > 201703L
+      constexpr back_insert_iterator() noexcept = default;
+#endif
 
       /// The only way to create this %iterator is with a container.
       explicit
@@ -588,11 +599,22 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     : public iterator<output_iterator_tag, void, void, void, void>
     {
     protected:
+#if __cplusplus <= 201703L
       _Container* container;
+#else
+      _Container* container = nullptr;
+#endif
 
     public:
       /// A nested typedef for the type of whatever container you used.
       typedef _Container          container_type;
+#if __cplusplus > 201703L
+      using difference_type = ptrdiff_t;
+#endif
+
+#if __cplusplus > 201703L
+      constexpr front_insert_iterator() noexcept = default;
+#endif
 
       /// The only way to create this %iterator is with a container.
       explicit front_insert_iterator(_Container& __x)
diff --git a/libstdc++-v3/testsuite/24_iterators/back_insert_iterator/pr93884.cc b/libstdc++-v3/testsuite/24_iterators/back_insert_iterator/pr93884.cc
new file mode 100644
index 00000000000..5a6287ddd40
--- /dev/null
+++ b/libstdc++-v3/testsuite/24_iterators/back_insert_iterator/pr93884.cc
@@ -0,0 +1,44 @@
+// Copyright (C) 2020 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-std=gnu++2a" }
+// { dg-do run { target c++2a } }
+
+#include <iterator>
+#include <algorithm>
+#include <vector>
+#include <testsuite_hooks.h>
+
+namespace ranges = std::ranges;
+namespace views = std::views;
+
+void
+test01()
+{
+  auto v = std::vector<int>{};
+  auto i = views::iota(0, 10);
+  auto o = std::back_inserter(v);
+  static_assert(std::output_iterator<decltype(o), int>);
+  ranges::copy(i, o);
+  VERIFY( ranges::equal(v, i) );
+}
+
+int
+main()
+{
+  test01();
+}
diff --git a/libstdc++-v3/testsuite/24_iterators/front_insert_iterator/pr93884.cc b/libstdc++-v3/testsuite/24_iterators/front_insert_iterator/pr93884.cc
new file mode 100644
index 00000000000..eaf4e9a187f
--- /dev/null
+++ b/libstdc++-v3/testsuite/24_iterators/front_insert_iterator/pr93884.cc
@@ -0,0 +1,44 @@
+// Copyright (C) 2020 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-std=gnu++2a" }
+// { dg-do run { target c++2a } }
+
+#include <iterator>
+#include <algorithm>
+#include <deque>
+#include <testsuite_hooks.h>
+
+namespace ranges = std::ranges;
+namespace views = std::views;
+
+void
+test01()
+{
+  auto v = std::deque<int>{};
+  auto i = views::iota(0, 10);
+  auto o = std::front_inserter(v);
+  static_assert(std::output_iterator<decltype(o), int>);
+  ranges::copy(i, o);
+  VERIFY( ranges::equal(v | views::reverse, i) );
+}
+
+int
+main()
+{
+  test01();
+}

On 24/02/20 08:53 -0500, Patrick Palka wrote:
>On Mon, 24 Feb 2020, Jonathan Wakely wrote:
>
>> On 24/02/20 08:29 -0500, Patrick Palka wrote:
>> > This adds some missing pieces of the Ranges TS that make
>> > back_insert_iterator and
>> > front_insert_iterator conform to the new output_iterator requirements.
>> >
>> > It also fixes a bug in ranges::__copy_or_move and
>> > ranges::__copy_or_move_backward in which we were inspecting the iter_value_t
>> > of
>> > the output iterator, but iterators such as back_insert_iterator and
>> > front_insert_iterator whose value_type is defined to be void do not have an
>> > iter_value_t according to [readable.traits] p4.  The entire __use_memmove
>> > condition can probably be refactored, but the simplest fix for now is to
>> > inspect
>> > the iterator_traits of the output iterator instead.
>> >
>> > libstdc++-v3/ChangeLog:
>> >
>> > 	PR libstdc++/93884
>> > 	* include/bits/ranges_algobase.h (__copy_or_move,
>> > 	__copy_or_move_backward): Don't inspect the iter_value_t of the output
>> > 	iterator, instead inspect its iterator_traits directly.
>> > 	* include/bits/stl_iterator.h (back_insert_iterator::container):
>> > 	Conditionally initialize.
>> > 	(back_insert_iterator::difference_type): Conditionally define.
>> > 	(back_insert_iterator::back_insert_iterator): Conditionally define
>> > this
>> > 	default constructor.
>> > 	(front_insert_iterator::container): Conditionally initialize.
>> > 	(front_insert_iterator::difference_type): Conditionally define.
>> > 	(front_insert_iterator::front_insert_iterator): Conditionally define
>> > 	this default constructor.
>> > ---
>> > libstdc++-v3/include/bits/ranges_algobase.h   |  4 +-
>> > libstdc++-v3/include/bits/stl_iterator.h      | 22 ++++++++++
>> > .../back_insert_iterator/pr93884.C            | 44 +++++++++++++++++++
>> > .../front_insert_iterator/pr93884.C           | 44 +++++++++++++++++++
>> > 4 files changed, 112 insertions(+), 2 deletions(-)
>> > create mode 100644
>> > libstdc++-v3/testsuite/24_iterators/back_insert_iterator/pr93884.C
>> > create mode 100644
>> > libstdc++-v3/testsuite/24_iterators/front_insert_iterator/pr93884.C
>> >
>> > diff --git a/libstdc++-v3/include/bits/ranges_algobase.h
>> > b/libstdc++-v3/include/bits/ranges_algobase.h
>> > index 807822e99c8..739424e1a2d 100644
>> > --- a/libstdc++-v3/include/bits/ranges_algobase.h
>> > +++ b/libstdc++-v3/include/bits/ranges_algobase.h
>> > @@ -249,7 +249,7 @@ namespace ranges
>> >       else if constexpr (sized_sentinel_for<_Sent, _Iter>)
>> > 	{
>> > 	  using _ValueTypeI = iter_value_t<_Iter>;
>> > -	  using _ValueTypeO = iter_value_t<_Out>;
>> > +	  using _ValueTypeO = iterator_traits<_Out>::value_type;
>>
>> I think this will fail to compile with Clang, because it needs
>> 'typename' there.
>>
>> > 	  constexpr bool __use_memmove
>> > 	    = (is_trivially_copyable_v<_ValueTypeI>
>> > 	       && is_same_v<_ValueTypeI, _ValueTypeO>
>> > @@ -386,7 +386,7 @@ namespace ranges
>> >       else if constexpr (sized_sentinel_for<_Sent, _Iter>)
>> > 	{
>> > 	  using _ValueTypeI = iter_value_t<_Iter>;
>> > -	  using _ValueTypeO = iter_value_t<_Out>;
>> > +	  using _ValueTypeO = iterator_traits<_Out>::value_type;
>>
>> Same here.
>
>Ah right... Here's v2 of the patch that adds typename to those two
>aliases and fixes the file extensions on the tests.

OK for master, thanks.

This should do the same changes for std::insert_iterator, but it
currently crashes the compiler (PR 93907). I am not committing this
yet.