Remove the polyfills for absl::apply and absl::make_from_tuple,

which were only needed prior to C++17. It is recommended that
clients simply use std::apply and std::make_from_tuple.

PiperOrigin-RevId: 731348450
Change-Id: I7711487c869e229f86304da43272fbade9f7301a

Author: derekmauro

absl/utility/BUILD.bazel

@@ -18,7 +18,6 @@ load(
     "//absl:copts/configure_copts.bzl",
     "ABSL_DEFAULT_COPTS",
     "ABSL_DEFAULT_LINKOPTS",
-    "ABSL_TEST_COPTS",
 )
 
 package(
@@ -40,23 +39,7 @@ cc_library(
     copts = ABSL_DEFAULT_COPTS,
     linkopts = ABSL_DEFAULT_LINKOPTS,
     deps = [
-        "//absl/base:base_internal",
         "//absl/base:config",
         "//absl/meta:type_traits",
     ],
 )
-
-cc_test(
-    name = "utility_test",
-    srcs = ["utility_test.cc"],
-    copts = ABSL_TEST_COPTS,
-    linkopts = ABSL_DEFAULT_LINKOPTS,
-    deps = [
-        ":utility",
-        "//absl/base:core_headers",
-        "//absl/memory",
-        "//absl/strings",
-        "@googletest//:gtest",
-        "@googletest//:gtest_main",
-    ],
-)

absl/utility/CMakeLists.txt

@@ -22,23 +22,7 @@ absl_cc_library(
   COPTS
     ${ABSL_DEFAULT_COPTS}
   DEPS
-    absl::base_internal
     absl::config
     absl::type_traits
   PUBLIC
 )
-
-absl_cc_test(
-  NAME
-    utility_test
-  SRCS
-    "utility_test.cc"
-  COPTS
-    ${ABSL_TEST_COPTS}
-  DEPS
-    absl::utility
-    absl::core_headers
-    absl::memory
-    absl::strings
-    GTest::gmock_main
-)

absl/utility/utility.h

@@ -11,21 +11,6 @@
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.
-//
-// This header file contains C++14 versions of standard <utility> header
-// abstractions available within C++17, and are designed to be drop-in
-// replacement for code compliant with C++14 and C++17.
-//
-// The following abstractions are defined:
-//
-//   * apply<Functor, Tuple>         == std::apply<Functor, Tuple>
-//   * exchange<T>                   == std::exchange<T>
-//   * make_from_tuple<T>            == std::make_from_tuple<T>
-//
-// References:
-//
-//  https://en.cppreference.com/w/cpp/utility/apply
-//  http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2013/n3658.html
 
 #ifndef ABSL_UTILITY_UTILITY_H_
 #define ABSL_UTILITY_UTILITY_H_
@@ -36,6 +21,8 @@
 #include <utility>
 
 #include "absl/base/config.h"
+
+// TODO(b/290784225): Include what you use cleanup required.
 #include "absl/meta/type_traits.h"
 
 namespace absl {
@@ -45,6 +32,7 @@ ABSL_NAMESPACE_BEGIN
 // abstractions for platforms that had not yet provided them. Those
 // platforms are no longer supported. New code should simply use the
 // the ones from std directly.
+using std::apply;
 using std::exchange;
 using std::forward;
 using std::in_place;
@@ -56,99 +44,11 @@ using std::in_place_type_t;
 using std::index_sequence;
 using std::index_sequence_for;
 using std::integer_sequence;
+using std::make_from_tuple;
 using std::make_index_sequence;
 using std::make_integer_sequence;
 using std::move;
 
-namespace utility_internal {
-// Helper method for expanding tuple into a called method.
-template <typename Functor, typename Tuple, std::size_t... Indexes>
-auto apply_helper(Functor&& functor, Tuple&& t, index_sequence<Indexes...>)
-    -> decltype(std::invoke(absl::forward<Functor>(functor),
-                            std::get<Indexes>(absl::forward<Tuple>(t))...)) {
-  return std::invoke(absl::forward<Functor>(functor),
-                     std::get<Indexes>(absl::forward<Tuple>(t))...);
-}
-}  // namespace utility_internal
-
-// apply
-//
-// Invokes a Callable using elements of a tuple as its arguments.
-// Each element of the tuple corresponds to an argument of the call (in order).
-// Both the Callable argument and the tuple argument are perfect-forwarded.
-// For member-function Callables, the first tuple element acts as the `this`
-// pointer. `absl::apply` is designed to be a drop-in replacement for C++17's
-// `std::apply`. Unlike C++17's `std::apply`, this is not currently `constexpr`.
-//
-// Example:
-//
-//   class Foo {
-//    public:
-//     void Bar(int);
-//   };
-//   void user_function1(int, std::string);
-//   void user_function2(std::unique_ptr<Foo>);
-//   auto user_lambda = [](int, int) {};
-//
-//   int main()
-//   {
-//       std::tuple<int, std::string> tuple1(42, "bar");
-//       // Invokes the first user function on int, std::string.
-//       absl::apply(&user_function1, tuple1);
-//
-//       std::tuple<std::unique_ptr<Foo>> tuple2(absl::make_unique<Foo>());
-//       // Invokes the user function that takes ownership of the unique
-//       // pointer.
-//       absl::apply(&user_function2, std::move(tuple2));
-//
-//       auto foo = absl::make_unique<Foo>();
-//       std::tuple<Foo*, int> tuple3(foo.get(), 42);
-//       // Invokes the method Bar on foo with one argument, 42.
-//       absl::apply(&Foo::Bar, tuple3);
-//
-//       std::tuple<int, int> tuple4(8, 9);
-//       // Invokes a lambda.
-//       absl::apply(user_lambda, tuple4);
-//   }
-template <typename Functor, typename Tuple>
-auto apply(Functor&& functor, Tuple&& t)
-    -> decltype(utility_internal::apply_helper(
-        absl::forward<Functor>(functor), absl::forward<Tuple>(t),
-        absl::make_index_sequence<std::tuple_size<
-            typename std::remove_reference<Tuple>::type>::value>{})) {
-  return utility_internal::apply_helper(
-      absl::forward<Functor>(functor), absl::forward<Tuple>(t),
-      absl::make_index_sequence<std::tuple_size<
-          typename std::remove_reference<Tuple>::type>::value>{});
-}
-
-namespace utility_internal {
-template <typename T, typename Tuple, size_t... I>
-T make_from_tuple_impl(Tuple&& tup, absl::index_sequence<I...>) {
-  return T(std::get<I>(std::forward<Tuple>(tup))...);
-}
-}  // namespace utility_internal
-
-// make_from_tuple
-//
-// Given the template parameter type `T` and a tuple of arguments
-// `std::tuple(arg0, arg1, ..., argN)` constructs an object of type `T` as if by
-// calling `T(arg0, arg1, ..., argN)`.
-//
-// Example:
-//
-//   std::tuple<const char*, size_t> args("hello world", 5);
-//   auto s = absl::make_from_tuple<std::string>(args);
-//   assert(s == "hello");
-//
-template <typename T, typename Tuple>
-constexpr T make_from_tuple(Tuple&& tup) {
-  return utility_internal::make_from_tuple_impl<T>(
-      std::forward<Tuple>(tup),
-      absl::make_index_sequence<
-          std::tuple_size<absl::decay_t<Tuple>>::value>{});
-}
-
 ABSL_NAMESPACE_END
 }  // namespace absl