@@ -1540,6 +1540,8 @@ namespace views
template<input_range _Vp, copy_constructible _Fp>
requires view<_Vp> && is_object_v<_Fp>
&& regular_invocable<_Fp&, range_reference_t<_Vp>>
+ && std::__detail::__can_reference<invoke_result_t<_Fp&,
+ range_reference_t<_Vp>>>
class transform_view : public view_interface<transform_view<_Vp, _Fp>>
{
private:
new file mode 100644
@@ -0,0 +1,35 @@
+// 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 compile { target c++2a } }
+
+#include <ranges>
+
+namespace ranges = std::ranges;
+namespace views = std::views;
+
+void
+test01()
+{
+ auto f = [] (int x) { };
+ int x[] = {1};
+ auto v = ranges::transform_view{x, f}; // { dg-error "deduction failed|no match" }
+}
+
+// { dg-prune-output "constraint failure" }
+// { dg-prune-output "in requirements" }