[ADT] Remove STLForwardCompat.h's C++17 equivalents

As a follow-up of e857896 which replaced the
callers to use the C++17 equivalents, remove the equivalents from
`STLForwardCompat.h` entirely and their corresponding tests.

Differential Revision: https://reviews.llvm.org/D131769

Author: JoeLoser

llvm/include/llvm/ADT/STLForwardCompat.h

@@ -21,49 +21,6 @@
 
 namespace llvm {
 
-//===----------------------------------------------------------------------===//
-//     Features from C++17
-//===----------------------------------------------------------------------===//
-
-template <typename T>
-struct negation // NOLINT(readability-identifier-naming)
-    : std::integral_constant<bool, !bool(T::value)> {};
-
-template <typename...>
-struct conjunction // NOLINT(readability-identifier-naming)
-    : std::true_type {};
-template <typename B1> struct conjunction<B1> : B1 {};
-template <typename B1, typename... Bn>
-struct conjunction<B1, Bn...>
-    : std::conditional<bool(B1::value), conjunction<Bn...>, B1>::type {};
-
-template <typename...>
-struct disjunction // NOLINT(readability-identifier-naming)
-    : std::false_type {};
-template <typename B1> struct disjunction<B1> : B1 {};
-template <typename B1, typename... Bn>
-struct disjunction<B1, Bn...>
-    : std::conditional<bool(B1::value), B1, disjunction<Bn...>>::type {};
-
-struct in_place_t // NOLINT(readability-identifier-naming)
-{
-  explicit in_place_t() = default;
-};
-/// \warning This must not be odr-used, as it cannot be made \c inline in C++14.
-constexpr in_place_t in_place; // NOLINT(readability-identifier-naming)
-
-template <typename T>
-struct in_place_type_t // NOLINT(readability-identifier-naming)
-{
-  explicit in_place_type_t() = default;
-};
-
-template <std::size_t I>
-struct in_place_index_t // NOLINT(readability-identifier-naming)
-{
-  explicit in_place_index_t() = default;
-};
-
 //===----------------------------------------------------------------------===//
 //     Features from C++20
 //===----------------------------------------------------------------------===//

llvm/unittests/ADT/STLForwardCompatTest.cpp

@@ -11,37 +11,6 @@
 
 namespace {
 
-TEST(STLForwardCompatTest, NegationTest) {
-  EXPECT_TRUE((llvm::negation<std::false_type>::value));
-  EXPECT_FALSE((llvm::negation<std::true_type>::value));
-}
-
-struct incomplete_type;
-
-TEST(STLForwardCompatTest, ConjunctionTest) {
-  EXPECT_TRUE((llvm::conjunction<>::value));
-  EXPECT_FALSE((llvm::conjunction<std::false_type>::value));
-  EXPECT_TRUE((llvm::conjunction<std::true_type>::value));
-  EXPECT_FALSE((llvm::conjunction<std::false_type, incomplete_type>::value));
-  EXPECT_FALSE((llvm::conjunction<std::false_type, std::true_type>::value));
-  EXPECT_FALSE((llvm::conjunction<std::true_type, std::false_type>::value));
-  EXPECT_TRUE((llvm::conjunction<std::true_type, std::true_type>::value));
-  EXPECT_TRUE((llvm::conjunction<std::true_type, std::true_type,
-                                 std::true_type>::value));
-}
-
-TEST(STLForwardCompatTest, DisjunctionTest) {
-  EXPECT_FALSE((llvm::disjunction<>::value));
-  EXPECT_FALSE((llvm::disjunction<std::false_type>::value));
-  EXPECT_TRUE((llvm::disjunction<std::true_type>::value));
-  EXPECT_TRUE((llvm::disjunction<std::true_type, incomplete_type>::value));
-  EXPECT_TRUE((llvm::disjunction<std::false_type, std::true_type>::value));
-  EXPECT_TRUE((llvm::disjunction<std::true_type, std::false_type>::value));
-  EXPECT_TRUE((llvm::disjunction<std::true_type, std::true_type>::value));
-  EXPECT_TRUE((llvm::disjunction<std::true_type, std::true_type,
-                                 std::true_type>::value));
-}
-
 template <typename T>
 class STLForwardCompatRemoveCVRefTest : public ::testing::Test {};