Replace as_const/void_t/no_fn type traits with their c++17 variants

webrtc own implementaions are no longer needed since webrtc uses c++17

Bug: None
Change-Id: I38bb295334182b73d333a453001d256e6df172d9
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/270924
Commit-Queue: Danil Chapovalov <danilchap@webrtc.org>
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#37716}

rtc_base/containers/BUILD.gn

@@ -10,14 +10,11 @@ import("../../webrtc.gni")
 
 rtc_library("flat_containers_internal") {
   sources = [
-    "as_const.h",
     "flat_tree.cc",
     "flat_tree.h",
     "identity.h",
     "invoke.h",
     "move_only_int.h",
-    "not_fn.h",
-    "void_t.h",
   ]
   deps = [
     "..:checks",

rtc_base/containers/as_const.h

@@ -1,32 +0,0 @@
-/*
- *  Copyright (c) 2021 The WebRTC project authors. All Rights Reserved.
- *
- *  Use of this source code is governed by a BSD-style license
- *  that can be found in the LICENSE file in the root of the source
- *  tree. An additional intellectual property rights grant can be found
- *  in the file PATENTS.  All contributing project authors may
- *  be found in the AUTHORS file in the root of the source tree.
- */
-
-// This implementation is borrowed from Chromium.
-
-#ifndef RTC_BASE_CONTAINERS_AS_CONST_H_
-#define RTC_BASE_CONTAINERS_AS_CONST_H_
-
-#include <type_traits>
-
-namespace webrtc {
-
-// C++14 implementation of C++17's std::as_const():
-// https://en.cppreference.com/w/cpp/utility/as_const
-template <typename T>
-constexpr std::add_const_t<T>& as_const(T& t) noexcept {
-  return t;
-}
-
-template <typename T>
-void as_const(const T&& t) = delete;
-
-}  // namespace webrtc
-
-#endif  // RTC_BASE_CONTAINERS_AS_CONST_H_

rtc_base/containers/flat_map_unittest.cc

@@ -14,6 +14,7 @@
 
 #include <algorithm>
 #include <string>
+#include <type_traits>
 #include <vector>
 
 #include "rtc_base/containers/move_only_int.h"
@@ -220,7 +221,7 @@ TEST(FlatMap, AtFunction) {
   EXPECT_EQ("b", m.at(2));
 
   // Const reference works.
-  const std::string& const_ref = webrtc::as_const(m).at(1);
+  const std::string& const_ref = std::as_const(m).at(1);
   EXPECT_EQ("a", const_ref);
 
   // Reference works, can operate on the string.
@@ -234,7 +235,7 @@ TEST(FlatMap, AtFunction) {
   // Heterogeneous look-up works.
   flat_map<std::string, int> m2 = {{"a", 1}, {"b", 2}};
   EXPECT_EQ(1, m2.at(absl::string_view("a")));
-  EXPECT_EQ(2, webrtc::as_const(m2).at(absl::string_view("b")));
+  EXPECT_EQ(2, std::as_const(m2).at(absl::string_view("b")));
 }
 
 // insert_or_assign(K&&, M&&)

rtc_base/containers/flat_tree.h

@@ -21,9 +21,6 @@
 
 #include "absl/algorithm/container.h"
 #include "rtc_base/checks.h"
-#include "rtc_base/containers/as_const.h"
-#include "rtc_base/containers/not_fn.h"
-#include "rtc_base/containers/void_t.h"
 #include "rtc_base/system/no_unique_address.h"
 
 namespace webrtc {
@@ -44,7 +41,7 @@ constexpr bool is_sorted_and_unique(const Range& range, Comp comp) {
   // Being unique implies that there are no adjacent elements that
   // compare equal. So this checks that each element is strictly less
   // than the element after it.
-  return absl::c_adjacent_find(range, webrtc::not_fn(comp)) == std::end(range);
+  return absl::c_adjacent_find(range, std::not_fn(comp)) == std::end(range);
 }
 
 // This is a convenience trait inheriting from std::true_type if Iterator is at
@@ -58,7 +55,7 @@ using is_multipass =
 template <typename T, typename = void>
 struct IsTransparentCompare : std::false_type {};
 template <typename T>
-struct IsTransparentCompare<T, void_t<typename T::is_transparent>>
+struct IsTransparentCompare<T, std::void_t<typename T::is_transparent>>
     : std::true_type {};
 
 // Helper inspired by C++20's std::to_array to convert a C-style array to a
@@ -543,7 +540,7 @@ class flat_tree {
     std::stable_sort(first, last, value_comp());
 
     // lhs is already <= rhs due to sort, therefore !(lhs < rhs) <=> lhs == rhs.
-    auto equal_comp = webrtc::not_fn(value_comp());
+    auto equal_comp = std::not_fn(value_comp());
     erase(std::unique(first, last, equal_comp), last);
   }
 
@@ -946,7 +943,7 @@ template <class Key, class GetKeyFromValue, class KeyCompare, class Container>
 template <typename K>
 auto flat_tree<Key, GetKeyFromValue, KeyCompare, Container>::find(const K& key)
     -> iterator {
-  return const_cast_it(webrtc::as_const(*this).find(key));
+  return const_cast_it(std::as_const(*this).find(key));
 }
 
 template <class Key, class GetKeyFromValue, class KeyCompare, class Container>
@@ -969,7 +966,7 @@ template <class Key, class GetKeyFromValue, class KeyCompare, class Container>
 template <typename K>
 auto flat_tree<Key, GetKeyFromValue, KeyCompare, Container>::equal_range(
     const K& key) -> std::pair<iterator, iterator> {
-  auto res = webrtc::as_const(*this).equal_range(key);
+  auto res = std::as_const(*this).equal_range(key);
   return {const_cast_it(res.first), const_cast_it(res.second)};
 }
 
@@ -990,7 +987,7 @@ template <class Key, class GetKeyFromValue, class KeyCompare, class Container>
 template <typename K>
 auto flat_tree<Key, GetKeyFromValue, KeyCompare, Container>::lower_bound(
     const K& key) -> iterator {
-  return const_cast_it(webrtc::as_const(*this).lower_bound(key));
+  return const_cast_it(std::as_const(*this).lower_bound(key));
 }
 
 template <class Key, class GetKeyFromValue, class KeyCompare, class Container>
@@ -1011,7 +1008,7 @@ template <class Key, class GetKeyFromValue, class KeyCompare, class Container>
 template <typename K>
 auto flat_tree<Key, GetKeyFromValue, KeyCompare, Container>::upper_bound(
     const K& key) -> iterator {
-  return const_cast_it(webrtc::as_const(*this).upper_bound(key));
+  return const_cast_it(std::as_const(*this).upper_bound(key));
 }
 
 template <class Key, class GetKeyFromValue, class KeyCompare, class Container>

rtc_base/containers/not_fn.h

@@ -1,64 +0,0 @@
-/*
- *  Copyright (c) 2021 The WebRTC project authors. All Rights Reserved.
- *
- *  Use of this source code is governed by a BSD-style license
- *  that can be found in the LICENSE file in the root of the source
- *  tree. An additional intellectual property rights grant can be found
- *  in the file PATENTS.  All contributing project authors may
- *  be found in the AUTHORS file in the root of the source tree.
- */
-
-// This implementation is borrowed from Chromium.
-
-#ifndef RTC_BASE_CONTAINERS_NOT_FN_H_
-#define RTC_BASE_CONTAINERS_NOT_FN_H_
-
-#include <type_traits>
-#include <utility>
-
-#include "rtc_base/containers/invoke.h"
-
-namespace webrtc {
-
-namespace not_fn_internal {
-
-template <typename F>
-struct NotFnImpl {
-  F f;
-
-  template <typename... Args>
-  constexpr decltype(auto) operator()(Args&&... args) & noexcept {
-    return !webrtc::invoke(f, std::forward<Args>(args)...);
-  }
-
-  template <typename... Args>
-  constexpr decltype(auto) operator()(Args&&... args) const& noexcept {
-    return !webrtc::invoke(f, std::forward<Args>(args)...);
-  }
-
-  template <typename... Args>
-  constexpr decltype(auto) operator()(Args&&... args) && noexcept {
-    return !webrtc::invoke(std::move(f), std::forward<Args>(args)...);
-  }
-
-  template <typename... Args>
-  constexpr decltype(auto) operator()(Args&&... args) const&& noexcept {
-    return !webrtc::invoke(std::move(f), std::forward<Args>(args)...);
-  }
-};
-
-}  // namespace not_fn_internal
-
-// Implementation of C++17's std::not_fn.
-//
-// Reference:
-// - https://en.cppreference.com/w/cpp/utility/functional/not_fn
-// - https://wg21.link/func.not.fn
-template <typename F>
-constexpr not_fn_internal::NotFnImpl<std::decay_t<F>> not_fn(F&& f) {
-  return {std::forward<F>(f)};
-}
-
-}  // namespace webrtc
-
-#endif  // RTC_BASE_CONTAINERS_NOT_FN_H_

rtc_base/containers/void_t.h

@@ -1,36 +0,0 @@
-/*
- *  Copyright (c) 2021 The WebRTC project authors. All Rights Reserved.
- *
- *  Use of this source code is governed by a BSD-style license
- *  that can be found in the LICENSE file in the root of the source
- *  tree. An additional intellectual property rights grant can be found
- *  in the file PATENTS.  All contributing project authors may
- *  be found in the AUTHORS file in the root of the source tree.
- */
-
-// This implementation is borrowed from Chromium.
-
-#ifndef RTC_BASE_CONTAINERS_VOID_T_H_
-#define RTC_BASE_CONTAINERS_VOID_T_H_
-
-namespace webrtc {
-namespace void_t_internal {
-// Implementation detail of webrtc::void_t below.
-template <typename...>
-struct make_void {
-  using type = void;
-};
-
-}  // namespace void_t_internal
-
-// webrtc::void_t is an implementation of std::void_t from C++17.
-//
-// We use `webrtc::void_t_internal::make_void` as a helper struct to avoid a
-// C++14 defect:
-//   http://en.cppreference.com/w/cpp/types/void_t
-//   http://open-std.org/JTC1/SC22/WG21/docs/cwg_defects.html#1558
-template <typename... Ts>
-using void_t = typename ::webrtc::void_t_internal::make_void<Ts...>::type;
-}  // namespace webrtc
-
-#endif  // RTC_BASE_CONTAINERS_VOID_T_H_