[SYCL] Fix sycl::vec constructor ambiguity (#8608)

Recent changes to the sycl::vec class added a private constructor taking
and array. This resulted in constructor ambiguity when passing an
initializer list, despite the constructor being private. This commit
removes the constructor, making the implementation use the constructor
taking both an array and an index sequence directly.

---------

Signed-off-by: Larsen, Steffen <steffen.larsen@intel.com>
Co-authored-by: Alexey Sachkov <alexey.sachkov@intel.com>

Author: Steffen Larsen

sycl/include/sycl/types.hpp

@@ -729,9 +729,6 @@ template <typename Type, int NumElements> class vec {
                 std::index_sequence<Is...>)
       : m_Data{Arr[Is]...} {}
 
-  constexpr vec(const std::array<vec_data_t<DataT>, NumElements> &Arr)
-      : vec{Arr, std::make_index_sequence<NumElements>()} {}
-
 public:
   using element_type = DataT;
   using rel_t = detail::rel_t<DataT>;
@@ -796,7 +793,8 @@ template <typename Type, int NumElements> class vec {
   template <typename Ty = DataT>
   explicit constexpr vec(const EnableIfHostHalf<Ty> &arg)
       : vec{detail::RepeatValue<NumElements>(
-            static_cast<vec_data_t<DataT>>(arg))} {}
+                static_cast<vec_data_t<DataT>>(arg)),
+            std::make_index_sequence<NumElements>()} {}
 
   template <typename Ty = DataT>
   typename detail::enable_if_t<
@@ -812,7 +810,8 @@ template <typename Type, int NumElements> class vec {
 #else
   explicit constexpr vec(const DataT &arg)
       : vec{detail::RepeatValue<NumElements>(
-            static_cast<vec_data_t<DataT>>(arg))} {}
+                static_cast<vec_data_t<DataT>>(arg)),
+            std::make_index_sequence<NumElements>()} {}
 
   template <typename Ty = DataT>
   typename detail::enable_if_t<
@@ -883,7 +882,8 @@ template <typename Type, int NumElements> class vec {
   template <typename... argTN, typename = EnableIfSuitableTypes<argTN...>,
             typename = EnableIfSuitableNumElements<argTN...>>
   constexpr vec(const argTN &...args)
-      : vec{VecArgArrayCreator<vec_data_t<DataT>, argTN...>::Create(args...)} {}
+      : vec{VecArgArrayCreator<vec_data_t<DataT>, argTN...>::Create(args...),
+            std::make_index_sequence<NumElements>()} {}
 
   // TODO: Remove, for debug purposes only.
   void dump() {

sycl/test/regression/vec_init_list_ctor.cpp

@@ -0,0 +1,12 @@
+// RUN: %clang -fsycl -fsyntax-only -Xclang -verify %s
+// expected-no-diagnostics
+
+// Regression test checking that the vector ctor taking an initializer list
+// doesn't cause warnings or errors.
+
+#include <sycl/sycl.hpp>
+
+int main() {
+  sycl::vec<int, 2> V({1, 2});
+  return 0;
+}