stdlib fixes after merge

Author: MichaelRFairhurst

cpp/common/test/includes/standard-library/utility.h

@@ -1,6 +1,7 @@
 #include "type_traits.h"
 #ifndef _GHLIBCPP_UTILITY
 #define _GHLIBCPP_UTILITY
+#include "tuple.h"
 
 namespace std {
 template <class T> constexpr T &&forward(remove_reference_t<T> &t) noexcept;
@@ -11,11 +12,23 @@ template <class T> typename add_rvalue_reference<T>::type declval() noexcept;
 
 template <class T> void swap(T &a, T &b) noexcept;
 
-template <class T1, class T2> struct pair {
-  T1 first;
-  T2 second;
-  pair(const T1 &a, const T2 &b);
+template <class T, class U> struct pair : tuple<T, U> {
+    T first;
+    U second;
+    pair(T t, U u);
 };
+template <class T, class U> std::pair<T, U> make_pair(T &&x, U &&y);
+
+template<size_t N, class T, class U>
+constexpr auto get(const std::pair<T, U> &p) noexcept {
+    if constexpr (N == 0) {
+        return p.first;
+    } else if constexpr (N == 1) {
+        return p.second;
+    } else {
+        static_assert(N < 2, "Index out of bounds for pair");
+    }
+}
 
 } // namespace std