[SYCL] Add value_type alias to sycl::vec class (#12960)

This PR adds the value_type alias for the data type of a sycl::vec
object as described in the spec.

---------

Co-authored-by: Alexey Bader <[email protected]>

Author: lbushi25

sycl/include/sycl/detail/generic_type_traits.hpp

@@ -518,7 +518,9 @@ template <typename T, typename Enable = void> struct RelConverter {
 template <typename T> class TryToGetElementType {
   static T check(...);
   template <typename A> static typename A::element_type check(const A &);
-  template <typename A> static typename A::value_type check(const A &);
+  template <typename A, typename = std::enable_if_t<!std::is_same_v<
+                            typename A::element_type, typename A::value_type>>>
+  static typename A::value_type check(const A &);
 
 public:
   using type = decltype(check(T()));

sycl/include/sycl/types.hpp

@@ -546,8 +546,8 @@ template <typename Type, int NumElements> class vec {
 
 public:
   using element_type = DataT;
+  using value_type = DataT;
   using rel_t = detail::rel_t<DataT>;
-
 #ifdef __SYCL_DEVICE_ONLY__
 #if defined(__INTEL_PREVIEW_BREAKING_CHANGES)
   using vector_t =

sycl/test/regression/vec_value_type.cpp

@@ -0,0 +1,11 @@
+// RUN: %clangxx -fsycl -fsyntax-only %s
+#include <sycl/sycl.hpp>
+#include <type_traits>
+using namespace std;
+int main() {
+  static_assert(is_same_v<sycl::vec<int, 1>::value_type, int>);
+  static_assert(is_same_v<sycl::vec<float, 2>::value_type, float>);
+  static_assert(is_same_v<sycl::vec<double, 3>::value_type, double>);
+  static_assert(is_same_v<sycl::vec<sycl::half, 4>::value_type, sycl::half>);
+  return 0;
+}