[gcc r17-4829] libstdc++: Add enable_borrowed_range<as_input_view<V>> [PR125785]

[Jonathan Wakely]

https://gcc.gnu.org/g:b8a469b62d85dc9cf8b995e0eece8eaa7f9ba7aa

commit r17-4829-gb8a469b62d85dc9cf8b995e0eece8eaa7f9ba7aa
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Thu Oct 1 21:20:36 2026 +0100

    libstdc++: Add enable_borrowed_range<as_input_view<V>> [PR125785]
    
    Add the missing partial specialization, and test for it.
    
    Also add tests for the as_const_view and as_rvalue_view partial
    specializations that weren't being tested.
    
    libstdc++-v3/ChangeLog:
    
            PR libstdc++/125785
            * include/std/ranges (enable_borrowed_range<as_input_view<T>>):
            Define partial specialization.
            * testsuite/std/ranges/adaptors/as_input/1.cc: Test
            specialization for as_input_view.
            * testsuite/std/ranges/adaptors/as_const/1.cc: Test
            specialization for as_const_view.
            * testsuite/std/ranges/adaptors/as_rvalue/1.cc: Test
            specialization for as_rvalue_view.
    
    Reviewed-by: Tomasz Kamiński <tkaminsk@redhat.com>

Diff:
---
 libstdc++-v3/include/std/ranges                           | 4 ++++
 libstdc++-v3/testsuite/std/ranges/adaptors/as_const/1.cc  | 5 +++++
 libstdc++-v3/testsuite/std/ranges/adaptors/as_input/1.cc  | 6 ++++++
 libstdc++-v3/testsuite/std/ranges/adaptors/as_rvalue/1.cc | 6 ++++++
 4 files changed, 21 insertions(+)

diff --git a/libstdc++-v3/include/std/ranges b/libstdc++-v3/include/std/ranges
index dde4ed90080d..37f048e3d0d3 100644
--- a/libstdc++-v3/include/std/ranges
+++ b/libstdc++-v3/include/std/ranges
@@ -10581,6 +10581,10 @@ namespace ranges
   template<typename _Range>
     as_input_view(_Range&&) -> as_input_view<views::all_t<_Range>>;
 
+  template<typename _Vp>
+    inline constexpr bool enable_borrowed_range<as_input_view<_Vp>>
+      = enable_borrowed_range<_Vp>;
+
   template<input_range _Vp>
     requires view<_Vp>
   template<bool _Const>
diff --git a/libstdc++-v3/testsuite/std/ranges/adaptors/as_const/1.cc b/libstdc++-v3/testsuite/std/ranges/adaptors/as_const/1.cc
index 5ccf47d4d300..135cc2911e93 100644
--- a/libstdc++-v3/testsuite/std/ranges/adaptors/as_const/1.cc
+++ b/libstdc++-v3/testsuite/std/ranges/adaptors/as_const/1.cc
@@ -81,6 +81,11 @@ test04()
   VERIFY( ranges::equal(v, x) );
 }
 
+using Owning = ranges::single_view<int>;
+using Borrowed = std::span<int>;
+static_assert( ! ranges::enable_borrowed_range<ranges::as_const_view<Owning>> );
+static_assert( ranges::enable_borrowed_range<ranges::as_const_view<Borrowed>> );
+
 int
 main()
 {
diff --git a/libstdc++-v3/testsuite/std/ranges/adaptors/as_input/1.cc b/libstdc++-v3/testsuite/std/ranges/adaptors/as_input/1.cc
index 8bd1a82a7b7f..2d2b2dd15821 100644
--- a/libstdc++-v3/testsuite/std/ranges/adaptors/as_input/1.cc
+++ b/libstdc++-v3/testsuite/std/ranges/adaptors/as_input/1.cc
@@ -8,6 +8,7 @@
 
 #include <algorithm>
 #include <vector>
+#include <span>
 #include <testsuite_hooks.h>
 #include <testsuite_iterators.h>
 
@@ -51,6 +52,11 @@ test02()
 			      decltype(x | views::as_input | views::as_input)> );
 }
 
+using Owning = ranges::single_view<int>;
+using Borrowed = std::span<int>;
+static_assert( ! ranges::enable_borrowed_range<ranges::as_input_view<Owning>> );
+static_assert( ranges::enable_borrowed_range<ranges::as_input_view<Borrowed>> );
+
 int
 main()
 {
diff --git a/libstdc++-v3/testsuite/std/ranges/adaptors/as_rvalue/1.cc b/libstdc++-v3/testsuite/std/ranges/adaptors/as_rvalue/1.cc
index 487700773705..531560ad84af 100644
--- a/libstdc++-v3/testsuite/std/ranges/adaptors/as_rvalue/1.cc
+++ b/libstdc++-v3/testsuite/std/ranges/adaptors/as_rvalue/1.cc
@@ -9,6 +9,7 @@
 
 #include <algorithm>
 #include <memory>
+#include <span>
 #include <testsuite_hooks.h>
 #include <testsuite_iterators.h>
 
@@ -55,6 +56,11 @@ test02()
   VERIFY( *y == 42 );
 }
 
+using Owning = ranges::single_view<int>;
+using Borrowed = std::span<int>;
+static_assert( ! ranges::enable_borrowed_range<ranges::as_rvalue_view<Owning>> );
+static_assert( ranges::enable_borrowed_range<ranges::as_rvalue_view<Borrowed>> );
+
 int
 main()
 {