[LLVMSupport] Drop remaining dependencies on APSInt.h, Error.h, DataTypes.h and STLForwardCompat.h

Most cases can drop the #includes without any changes, in some cases there are
straighforward replacements (climits, cstdint). For STLForwardCompat.h, we need
to bring in parts of STLForwardCompat.h from llvm-project.

Author: kubamracek

include/swift/AST/LayoutConstraintKind.h

@@ -14,7 +14,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "llvm/Support/DataTypes.h"
+#include <cstdint>
 
 #ifndef SWIFT_LAYOUT_CONSTRAINTKIND_H
 #define SWIFT_LAYOUT_CONSTRAINTKIND_H

stdlib/include/llvm/ADT/Optional.h

@@ -17,7 +17,6 @@
 
 #include "llvm/ADT/Hashing.h"
 #include "llvm/ADT/None.h"
-#include "llvm/ADT/STLForwardCompat.h"
 #include "llvm/Support/Compiler.h"
 #include "llvm/Support/type_traits.h"
 #include <cassert>
@@ -28,6 +27,19 @@
 inline namespace __swift { inline namespace __runtime {
 namespace llvm {
 
+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;
+};
+
 class raw_ostream;
 
 namespace optional_detail {

stdlib/include/llvm/ADT/STLExtras.h

@@ -17,7 +17,6 @@
 #define LLVM_ADT_STLEXTRAS_H
 
 #include "llvm/ADT/Optional.h"
-#include "llvm/ADT/STLForwardCompat.h"
 #include "llvm/ADT/iterator.h"
 #include "llvm/ADT/iterator_range.h"
 #include "llvm/Support/ErrorHandling.h"
@@ -42,6 +41,32 @@
 inline namespace __swift { inline namespace __runtime {
 namespace llvm {
 
+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 {};
+
+template <typename T>
+struct remove_cvref // NOLINT(readability-identifier-naming)
+{
+  using type = std::remove_cv_t<std::remove_reference_t<T>>;
+};
+
+template <typename T>
+using remove_cvref_t // NOLINT(readability-identifier-naming)
+    = typename llvm::remove_cvref<T>::type;
+
 // Only used by compiler if both template types are the same.  Useful when
 // using SFINAE to test for the existence of member functions.
 template <typename T, T> struct SameType;

stdlib/include/llvm/ADT/StringExtras.h

@@ -13,7 +13,6 @@
 #ifndef LLVM_ADT_STRINGEXTRAS_H
 #define LLVM_ADT_STRINGEXTRAS_H
 
-#include "llvm/ADT/APSInt.h"
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/StringRef.h"

stdlib/include/llvm/Support/raw_ostream.h

@@ -15,7 +15,6 @@
 
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringRef.h"
-#include "llvm/Support/DataTypes.h"
 #include <cassert>
 #include <chrono>
 #include <cstddef>

stdlib/public/LLVMSupport/StringRef.cpp

@@ -6,10 +6,11 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "llvm/ADT/StringExtras.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/ADT/Hashing.h"
-#include "llvm/Support/Error.h"
 #include <bitset>
+#include <climits>
 
 using namespace llvm;