libstdc++: Implement P3137R3 views::to_input for C++26

libstdc++-v3/ChangeLog:

	* include/bits/version.def (ranges_to_input): Define.
	* include/bits/version.h: Regenerate.
	* include/std/ranges (ranges::to_input_view): Define for C++26.
	(views::__detail::__can_to_input): Likewise.
	(views::_ToInput, views::to_input): Likewise.
	* testsuite/std/ranges/adaptors/to_input/1.cc: New test.

Reviewed-by: Tomasz Kamiński <tkaminsk@redhat.com>
Reviewed-by: Jonathan Wakely <jwakely@redhat.com>

1 files changed, 59 insertions, 0 deletions

diff --git a/libstdc++-v3/testsuite/std/ranges/adaptors/to_input/1.cc b/libstdc++-v3/testsuite/std/ranges/adaptors/to_input/1.cc
new file mode 100644
index 0000000..cde368a
--- /dev/null
+++ b/libstdc++-v3/testsuite/std/ranges/adaptors/to_input/1.cc
@@ -0,0 +1,59 @@
+// { dg-do run { target c++26 } }
+
+#include <ranges>
+
+#if __cpp_lib_ranges_to_input != 202502L
+# error "Feature-test macro __cpp_lib_ranges_to_input has wrong value in <ranges>"
+#endif
+
+#include <algorithm>
+#include <vector>
+#include <testsuite_hooks.h>
+#include <testsuite_iterators.h>
+
+namespace ranges = std::ranges;
+namespace views = std::views;
+
+void
+test01()
+{
+  std::vector<int> r{1,2,3};
+  auto v = r | views::to_input;
+  using type = decltype(v);
+  static_assert( ranges::input_range<type> && !ranges::forward_range<type> );
+
+  VERIFY( ranges::equal(v.base(), r) );
+  VERIFY( v.size() == r.size() );
+  VERIFY( v.end() == r.end() );
+  auto it = v.begin();
+  VERIFY( it != r.end() );
+  *it = 42;
+  ++it;
+  *it = 43;
+  it++;
+  ranges::iter_swap(v.begin(), it);
+  VERIFY( ranges::equal(r, (int[]){3,43,42}) );
+  *it = ranges::iter_move(it);
+  VERIFY( it == r.begin() + 2 );
+  VERIFY( r.end() - it == 1 );
+  VERIFY( it - r.end() == -1 );
+}
+
+void
+test02()
+{
+  int x[] = {1,2,3};
+  __gnu_test::test_input_range<int> rx(x);
+  static_assert( !ranges::common_range<decltype(rx)> );
+  auto v = rx | views::to_input;
+  static_assert( std::same_as<decltype(v), decltype(views::all(rx))> );
+  static_assert( std::same_as<decltype(x | views::to_input),
+			      decltype(x | views::to_input | views::to_input)> );
+}
+
+int
+main()
+{
+  test01();
+  test02();
+}