[libc++] Revert temporary attempt to implement LWG 4110 (#95263)

When I filed LWG4110 after the discussion in #93071, I thought it was
going to be a straightforward fix. It turns out that it isn't, so we
should stay in the state where libc++ is Standards conforming even if
that state leads to some reasonable code being rejected by the library.
Once WG21 figures out what to do with this issue and votes on it, we'll
implement it through our normal means.

This reverts f638f7b and 16f2aa1.

libcxx/docs/Status/Cxx2cIssues.csv

@@ -65,5 +65,4 @@
 "`3343 <https://wg21.link/LWG3343>`__","Ordering of calls to ``unlock()`` and ``notify_all()`` in Effects element of ``notify_all_at_thread_exit()`` should be reversed","Not Yet Adopted","|Complete|","16.0",""
 "XXXX","","The sys_info range should be affected by save","Not Yet Adopted","|Complete|","19.0"
 "`4071 <https://wg21.link/LWG4071>`__","","``reference_wrapper`` comparisons are not SFINAE-friendly","Not Yet Adopted","|Complete|","19.0"
-"`4110 <https://wg21.link/LWG4110>`__","","``shared_ptr(nullptr_t, Deleter)`` is overconstrained, breaking some sensible deleters","Not Yet Adopted","|Complete|","19.0"
 "","","","","",""

libcxx/include/__memory/shared_ptr.h

@@ -404,7 +404,7 @@ struct __shared_ptr_deleter_ctor_reqs {
 };
 
 template <class _Dp, class _Tp>
-using __shared_ptr_nullptr_deleter_ctor_reqs = _And<is_move_constructible<_Dp>, __well_formed_deleter<_Dp, _Tp*> >;
+using __shared_ptr_nullptr_deleter_ctor_reqs = _And<is_move_constructible<_Dp>, __well_formed_deleter<_Dp, nullptr_t> >;
 
 #if defined(_LIBCPP_ABI_ENABLE_SHARED_PTR_TRIVIAL_ABI)
 #  define _LIBCPP_SHARED_PTR_TRIVIAL_ABI __attribute__((__trivial_abi__))

libcxx/test/std/utilities/memory/util.smartptr/util.smartptr.shared/util.smartptr.shared.const/nullptr_t_deleter.pass.cpp

@@ -32,16 +32,17 @@ int A::count = 0;
 // LWG 3233. Broken requirements for shared_ptr converting constructors
 // https://cplusplus.github.io/LWG/issue3233
 static_assert( std::is_constructible<std::shared_ptr<int>,  std::nullptr_t, test_deleter<int> >::value, "");
-static_assert(!std::is_constructible<std::shared_ptr<int>, std::nullptr_t, bad_deleter>::value, "");
+static_assert(!std::is_constructible<std::shared_ptr<int>,  std::nullptr_t, bad_deleter>::value, "");
+static_assert(!std::is_constructible<std::shared_ptr<int>,  std::nullptr_t, no_nullptr_deleter>::value, "");
 static_assert(!std::is_constructible<std::shared_ptr<int>,  std::nullptr_t, no_move_deleter>::value, "");
 
 #if TEST_STD_VER >= 17
-static_assert(std::is_constructible<std::shared_ptr<int[]>, std::nullptr_t, test_deleter<int[]> >::value, "");
+static_assert( std::is_constructible<std::shared_ptr<int[]>,  std::nullptr_t, test_deleter<int> >::value, "");
 static_assert(!std::is_constructible<std::shared_ptr<int[]>,  std::nullptr_t, bad_deleter>::value, "");
 static_assert(!std::is_constructible<std::shared_ptr<int[]>,  std::nullptr_t, no_nullptr_deleter>::value, "");
 static_assert(!std::is_constructible<std::shared_ptr<int[]>,  std::nullptr_t, no_move_deleter>::value, "");
 
-static_assert(std::is_constructible<std::shared_ptr<int[5]>, std::nullptr_t, test_deleter<int[5]> >::value, "");
+static_assert( std::is_constructible<std::shared_ptr<int[5]>,  std::nullptr_t, test_deleter<int> >::value, "");
 static_assert(!std::is_constructible<std::shared_ptr<int[5]>,  std::nullptr_t, bad_deleter>::value, "");
 static_assert(!std::is_constructible<std::shared_ptr<int[5]>,  std::nullptr_t, no_nullptr_deleter>::value, "");
 static_assert(!std::is_constructible<std::shared_ptr<int[5]>,  std::nullptr_t, no_move_deleter>::value, "");

libcxx/test/std/utilities/memory/util.smartptr/util.smartptr.shared/util.smartptr.shared.const/nullptr_t_deleter_allocator.pass.cpp

@@ -33,21 +33,17 @@ int A::count = 0;
 // LWG 3233. Broken requirements for shared_ptr converting constructors
 // https://cplusplus.github.io/LWG/issue3233
 static_assert( std::is_constructible<std::shared_ptr<int>,  std::nullptr_t, test_deleter<int>, test_allocator<int> >::value, "");
-static_assert(!std::is_constructible<std::shared_ptr<int>, std::nullptr_t, bad_deleter, test_allocator<int> >::value,
-              "");
+static_assert(!std::is_constructible<std::shared_ptr<int>,  std::nullptr_t, bad_deleter, test_allocator<int> >::value, "");
+static_assert(!std::is_constructible<std::shared_ptr<int>,  std::nullptr_t, no_nullptr_deleter, test_allocator<int> >::value, "");
 static_assert(!std::is_constructible<std::shared_ptr<int>,  std::nullptr_t, no_move_deleter, test_allocator<int> >::value, "");
 
 #if TEST_STD_VER >= 17
-static_assert(
-    std::is_constructible<std::shared_ptr<int[]>, std::nullptr_t, test_deleter<int[]>, test_allocator<int> >::value,
-    "");
+static_assert( std::is_constructible<std::shared_ptr<int[]>,  std::nullptr_t, test_deleter<int>, test_allocator<int> >::value, "");
 static_assert(!std::is_constructible<std::shared_ptr<int[]>,  std::nullptr_t, bad_deleter, test_allocator<int> >::value, "");
 static_assert(!std::is_constructible<std::shared_ptr<int[]>,  std::nullptr_t, no_nullptr_deleter, test_allocator<int> >::value, "");
 static_assert(!std::is_constructible<std::shared_ptr<int[]>,  std::nullptr_t, no_move_deleter, test_allocator<int> >::value, "");
 
-static_assert(
-    std::is_constructible<std::shared_ptr<int[5]>, std::nullptr_t, test_deleter<int[5]>, test_allocator<int> >::value,
-    "");
+static_assert( std::is_constructible<std::shared_ptr<int[5]>,  std::nullptr_t, test_deleter<int>, test_allocator<int> >::value, "");
 static_assert(!std::is_constructible<std::shared_ptr<int[5]>,  std::nullptr_t, bad_deleter, test_allocator<int> >::value, "");
 static_assert(!std::is_constructible<std::shared_ptr<int[5]>,  std::nullptr_t, no_nullptr_deleter, test_allocator<int> >::value, "");
 static_assert(!std::is_constructible<std::shared_ptr<int[5]>,  std::nullptr_t, no_move_deleter, test_allocator<int> >::value, "");

libcxx/test/std/utilities/memory/util.smartptr/util.smartptr.shared/util.smartptr.shared.const/pointer_deleter.pass.cpp

@@ -115,14 +115,6 @@ int main(int, char**)
     }
 #endif // TEST_STD_VER >= 11
 
-#if TEST_STD_VER >= 14
-    {
-      // LWG 4110
-      auto deleter = [](auto pointer) { delete pointer; };
-      std::shared_ptr<int> p(new int, deleter);
-    }
-#endif
-
   test_function_type();
   return 0;
 }

libcxx/test/std/utilities/memory/util.smartptr/util.smartptr.shared/util.smartptr.shared.const/pointer_deleter_allocator.pass.cpp

@@ -165,13 +165,5 @@ int main(int, char**)
                                              test_allocator<Derived[4]> >::value, "");
     }
 
-#if TEST_STD_VER >= 14
-    {
-      // LWG 4110
-      auto deleter = [](auto pointer) { delete pointer; };
-      std::shared_ptr<int> p(new int, deleter, std::allocator<int>());
-    }
-#endif
-
   return 0;
 }