Merge branch 'issue/mdarray-to-mdspan' into 'master'

Fix mdspan converting constructor

See merge request !1522

(cherry picked from commit a7da5ef8)

2c0dda20 Fix mdspan converting constructor
7c72f546 Add test for the converting constructor

Co-authored-by: Christoph Grüninger <gruenich@dune-project.org>

dune/common/std/mdspan.hh

@@ -167,10 +167,10 @@ public:
 
   /// \brief Converting constructor
   template <class OtherElementType, class OtherExtends, class OtherLayoutPolicy, class OtherAccessor,
-    std::enable_if_t<std::is_constructible_v<mapping_type, const typename OtherElementType::template mapping<OtherExtends>&>, int> = 0,
+    std::enable_if_t<std::is_constructible_v<mapping_type, const typename OtherLayoutPolicy::template mapping<OtherExtends>&>, int> = 0,
     std::enable_if_t<std::is_constructible_v<accessor_type, const OtherAccessor&>, int> = 0>
   #if __cpp_conditional_explicit >= 201806L
-  explicit(!std::is_convertible_v<const typename OtherElementType::template mapping<OtherExtends>&, mapping_type>
+  explicit(!std::is_convertible_v<const typename OtherLayoutPolicy::template mapping<OtherExtends>&, mapping_type>
     || !std::is_convertible_v<const OtherAccessor&, accessor_type>)
   #endif
   constexpr mdspan (const mdspan<OtherElementType,OtherExtends,OtherLayoutPolicy,OtherAccessor>& other) noexcept

dune/common/std/test/mdspantest.cc

@@ -83,6 +83,11 @@ void test_accessor (Dune::TestSuite& testSuite, std::string name, const M& mappi
   else if constexpr(Span::rank() == 3)
     Span span5{dh, e.extent(0), e.extent(1), e.extent(2)};
 
+  // converting constructor
+  using OtherExtents = Dune::Std::dextents<std::size_t, Span::rank()>;
+  using OtherSpan = Dune::Std::mdspan<typename A::element_type, OtherExtents, typename M::layout_type, A>;
+  OtherSpan otherSpan(span4);
+
   checkAccess(subTestSuite, span2);
   testSuite.subTest(subTestSuite);
 }