[libcxx-commits] [libcxx] [libc++] Fix value category issues in `mdspan::operator[]` bounds checking (PR #192269)

[via libcxx-commits]

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@@ -191,11 +191,15 @@ class mdspan {
              (is_nothrow_constructible_v<index_type, _OtherIndexTypes> && ...) &&
              (sizeof...(_OtherIndexTypes) == rank()))
   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr reference operator[](_OtherIndexTypes... __indices) const {
-    // Note the standard layouts would also check this, but user provided ones may not, so we
-    // check the precondition here
-    _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__mdspan_detail::__is_multidimensional_index_in(extents(), __indices...),
-                                        "mdspan: operator[] out of bounds access");
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eiytoq wrote:

The root cause is that the hardening check misses `std::move` on the indices.

https://github.com/llvm/llvm-project/pull/192269