Proposed resolution:

This wording is relative to N5008.

1. Modify [simd.syn], header <simd> synopsis, as indicated:

   namespace std::datapar {
     […]
     template<simd-size-typesize_t N, class T, class Abi>
       constexpr auto chunk(const basic_simd<T, Abi>& x) noexcept;
     template<simd-size-typesize_t N, size_t Bytes, class Abi>
       constexpr auto chunk(const basic_simd_mask<Bytes, Abi>& x) noexcept;
     […]
   }
   

2. Modify [simd.creation] as indicated:

   template<simd-size-typesize_t N, class T, class Abi>
     constexpr auto chunk(const basic_simd<T, Abi>& x) noexcept;
   

   -4- Effects: Equivalent to: return chunk<resize_t<N, basic_simd<T, Abi>>>(x);

   template<simd-size-typesize_t N, size_t Bytes, class Abi>
     constexpr auto chunk(const basic_simd_mask<Bytes, Abi>& x) noexcept;
   

   -5- Effects: Equivalent to: return chunk<resize_t<N, basic_simd_mask<Bytes, Abi>>>(x);

All index values and simd widths in subclause "Data-parallel types" use the type simd-size-type. Specifically, the NTTP of `std::datapar::resize` uses simd-size-type and `std::datapar::chunk` is "implemented" using `std::datapar::resize`.

For chunk<N>, N is of type `size_t` and needs to be converted to simd-size-type in the effects clause where it is passed to resize. The NTTP of chunk should use simd-size-type instead of `size_t`.