From 8328f29e7b6682fb5ba83be951b5ed0a360bb465 Mon Sep 17 00:00:00 2001
From: Christian Trott <crtrott@sandia.gov>
Date: Mon, 23 Oct 2023 12:57:17 -0600
Subject: [PATCH] Fix layout_stride convertibility

---
 compilation_tests/ctest_layout_convertible.cpp            | 4 +++-
 include/experimental/__p0009_bits/layout_stride.hpp       | 8 ++++----
 .../layout_stride.ctor.strided_mapping.pass.cpp           | 2 +-
 3 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/compilation_tests/ctest_layout_convertible.cpp b/compilation_tests/ctest_layout_convertible.cpp
index 8f866fce..2da8b84e 100644
--- a/compilation_tests/ctest_layout_convertible.cpp
+++ b/compilation_tests/ctest_layout_convertible.cpp
@@ -80,10 +80,12 @@ MDSPAN_STATIC_TEST(
   !std::is_convertible<AStridedLayout<false>::mapping<E2>, LS1>::value
 );
 
+#if !MDSPAN_HAS_CXX_14 && !MDSPAN_HAS_CXX_20
 MDSPAN_STATIC_TEST(
   std::is_constructible<LS2, AStridedLayout<true>::mapping<E1>>::value &&
-  std::is_convertible<AStridedLayout<true>::mapping<E1>, LS2>::value
+  !std::is_convertible<AStridedLayout<true>::mapping<E1>, LS2>::value
 );
+#endif
 
 MDSPAN_STATIC_TEST(
   !std::is_constructible<LS1, NotARealLayout::mapping<E2>>::value
diff --git a/include/experimental/__p0009_bits/layout_stride.hpp b/include/experimental/__p0009_bits/layout_stride.hpp
index 4883f07b..ffb8054a 100644
--- a/include/experimental/__p0009_bits/layout_stride.hpp
+++ b/include/experimental/__p0009_bits/layout_stride.hpp
@@ -363,10 +363,10 @@ struct layout_stride {
     )
 #endif
     MDSPAN_CONDITIONAL_EXPLICIT(
-      (!std::is_convertible<typename StridedLayoutMapping::extents_type, extents_type>::value) &&
-      (detail::__is_mapping_of<layout_left, StridedLayoutMapping> ||
-       detail::__is_mapping_of<layout_right, StridedLayoutMapping> ||
-       detail::__is_mapping_of<layout_stride, StridedLayoutMapping>)
+      !(std::is_convertible<typename StridedLayoutMapping::extents_type, extents_type>::value &&
+       (detail::__is_mapping_of<layout_left, StridedLayoutMapping> ||
+        detail::__is_mapping_of<layout_right, StridedLayoutMapping> ||
+        detail::__is_mapping_of<layout_stride, StridedLayoutMapping>))
     ) // needs two () due to comma
     MDSPAN_INLINE_FUNCTION _MDSPAN_CONSTEXPR_14
     mapping(StridedLayoutMapping const& other) noexcept // NOLINT(google-explicit-constructor)
diff --git a/tests/libcxx-backports/layout_stride/layout_stride.ctor.strided_mapping.pass.cpp b/tests/libcxx-backports/layout_stride/layout_stride.ctor.strided_mapping.pass.cpp
index c044b96e..7772cbe2 100644
--- a/tests/libcxx-backports/layout_stride/layout_stride.ctor.strided_mapping.pass.cpp
+++ b/tests/libcxx-backports/layout_stride/layout_stride.ctor.strided_mapping.pass.cpp
@@ -182,7 +182,7 @@ constexpr bool test() {
   test_layout<std::layout_right>();
   test_layout<std::layout_left>();
   test_layout<std::layout_stride>();
-  //test_layout<always_convertible_layout>(); //FIXME
+  test_layout<always_convertible_layout>();
   return true;
 }