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commit_hash:2ec2671384dd8e604d41bc5c52c2f7858e4afea6

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diff --git a/contrib/libs/llvm14/include/llvm/Support/VirtualFileSystem.h b/contrib/libs/llvm14/include/llvm/Support/VirtualFileSystem.h
deleted file mode 100644
index b053fa41663..00000000000
--- a/contrib/libs/llvm14/include/llvm/Support/VirtualFileSystem.h
+++ /dev/null
@@ -1,992 +0,0 @@
-#pragma once
-
-#ifdef __GNUC__
-#pragma GCC diagnostic push
-#pragma GCC diagnostic ignored "-Wunused-parameter"
-#endif
-
-//===- VirtualFileSystem.h - Virtual File System Layer ----------*- C++ -*-===//
-//
-// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
-// See https://llvm.org/LICENSE.txt for license information.
-// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-//
-//===----------------------------------------------------------------------===//
-//
-/// \file
-/// Defines the virtual file system interface vfs::FileSystem.
-//
-//===----------------------------------------------------------------------===//
-
-#ifndef LLVM_SUPPORT_VIRTUALFILESYSTEM_H
-#define LLVM_SUPPORT_VIRTUALFILESYSTEM_H
-
-#include "llvm/ADT/IntrusiveRefCntPtr.h"
-#include "llvm/ADT/None.h"
-#include "llvm/ADT/Optional.h"
-#include "llvm/ADT/SmallVector.h"
-#include "llvm/ADT/StringRef.h"
-#include "llvm/ADT/StringMap.h"
-#include "llvm/ADT/STLFunctionalExtras.h"
-#include "llvm/Support/Chrono.h"
-#include "llvm/Support/ErrorOr.h"
-#include "llvm/Support/FileSystem.h"
-#include "llvm/Support/Path.h"
-#include "llvm/Support/SourceMgr.h"
-#include <cassert>
-#include <cstdint>
-#include <ctime>
-#include <memory>
-#include <stack>
-#include <string>
-#include <system_error>
-#include <utility>
-#include <vector>
-
-namespace llvm {
-
-class MemoryBuffer;
-class MemoryBufferRef;
-class Twine;
-
-namespace vfs {
-
-/// The result of a \p status operation.
-class Status {
-  std::string Name;
-  llvm::sys::fs::UniqueID UID;
-  llvm::sys::TimePoint<> MTime;
-  uint32_t User;
-  uint32_t Group;
-  uint64_t Size;
-  llvm::sys::fs::file_type Type = llvm::sys::fs::file_type::status_error;
-  llvm::sys::fs::perms Perms;
-
-public:
-  // FIXME: remove when files support multiple names
-  bool IsVFSMapped = false;
-
-  Status() = default;
-  Status(const llvm::sys::fs::file_status &Status);
-  Status(const Twine &Name, llvm::sys::fs::UniqueID UID,
-         llvm::sys::TimePoint<> MTime, uint32_t User, uint32_t Group,
-         uint64_t Size, llvm::sys::fs::file_type Type,
-         llvm::sys::fs::perms Perms);
-
-  /// Get a copy of a Status with a different size.
-  static Status copyWithNewSize(const Status &In, uint64_t NewSize);
-  /// Get a copy of a Status with a different name.
-  static Status copyWithNewName(const Status &In, const Twine &NewName);
-  static Status copyWithNewName(const llvm::sys::fs::file_status &In,
-                                const Twine &NewName);
-
-  /// Returns the name that should be used for this file or directory.
-  StringRef getName() const { return Name; }
-
-  /// @name Status interface from llvm::sys::fs
-  /// @{
-  llvm::sys::fs::file_type getType() const { return Type; }
-  llvm::sys::fs::perms getPermissions() const { return Perms; }
-  llvm::sys::TimePoint<> getLastModificationTime() const { return MTime; }
-  llvm::sys::fs::UniqueID getUniqueID() const { return UID; }
-  uint32_t getUser() const { return User; }
-  uint32_t getGroup() const { return Group; }
-  uint64_t getSize() const { return Size; }
-  /// @}
-  /// @name Status queries
-  /// These are static queries in llvm::sys::fs.
-  /// @{
-  bool equivalent(const Status &Other) const;
-  bool isDirectory() const;
-  bool isRegularFile() const;
-  bool isOther() const;
-  bool isSymlink() const;
-  bool isStatusKnown() const;
-  bool exists() const;
-  /// @}
-};
-
-/// Represents an open file.
-class File {
-public:
-  /// Destroy the file after closing it (if open).
-  /// Sub-classes should generally call close() inside their destructors.  We
-  /// cannot do that from the base class, since close is virtual.
-  virtual ~File();
-
-  /// Get the status of the file.
-  virtual llvm::ErrorOr<Status> status() = 0;
-
-  /// Get the name of the file
-  virtual llvm::ErrorOr<std::string> getName() {
-    if (auto Status = status())
-      return Status->getName().str();
-    else
-      return Status.getError();
-  }
-
-  /// Get the contents of the file as a \p MemoryBuffer.
-  virtual llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>>
-  getBuffer(const Twine &Name, int64_t FileSize = -1,
-            bool RequiresNullTerminator = true, bool IsVolatile = false) = 0;
-
-  /// Closes the file.
-  virtual std::error_code close() = 0;
-
-  // Get the same file with a different path.
-  static ErrorOr<std::unique_ptr<File>>
-  getWithPath(ErrorOr<std::unique_ptr<File>> Result, const Twine &P);
-
-protected:
-  // Set the file's underlying path.
-  virtual void setPath(const Twine &Path) {}
-};
-
-/// A member of a directory, yielded by a directory_iterator.
-/// Only information available on most platforms is included.
-class directory_entry {
-  std::string Path;
-  llvm::sys::fs::file_type Type = llvm::sys::fs::file_type::type_unknown;
-
-public:
-  directory_entry() = default;
-  directory_entry(std::string Path, llvm::sys::fs::file_type Type)
-      : Path(std::move(Path)), Type(Type) {}
-
-  llvm::StringRef path() const { return Path; }
-  llvm::sys::fs::file_type type() const { return Type; }
-};
-
-namespace detail {
-
-/// An interface for virtual file systems to provide an iterator over the
-/// (non-recursive) contents of a directory.
-struct DirIterImpl {
-  virtual ~DirIterImpl();
-
-  /// Sets \c CurrentEntry to the next entry in the directory on success,
-  /// to directory_entry() at end,  or returns a system-defined \c error_code.
-  virtual std::error_code increment() = 0;
-
-  directory_entry CurrentEntry;
-};
-
-} // namespace detail
-
-/// An input iterator over the entries in a virtual path, similar to
-/// llvm::sys::fs::directory_iterator.
-class directory_iterator {
-  std::shared_ptr<detail::DirIterImpl> Impl; // Input iterator semantics on copy
-
-public:
-  directory_iterator(std::shared_ptr<detail::DirIterImpl> I)
-      : Impl(std::move(I)) {
-    assert(Impl.get() != nullptr && "requires non-null implementation");
-    if (Impl->CurrentEntry.path().empty())
-      Impl.reset(); // Normalize the end iterator to Impl == nullptr.
-  }
-
-  /// Construct an 'end' iterator.
-  directory_iterator() = default;
-
-  /// Equivalent to operator++, with an error code.
-  directory_iterator &increment(std::error_code &EC) {
-    assert(Impl && "attempting to increment past end");
-    EC = Impl->increment();
-    if (Impl->CurrentEntry.path().empty())
-      Impl.reset(); // Normalize the end iterator to Impl == nullptr.
-    return *this;
-  }
-
-  const directory_entry &operator*() const { return Impl->CurrentEntry; }
-  const directory_entry *operator->() const { return &Impl->CurrentEntry; }
-
-  bool operator==(const directory_iterator &RHS) const {
-    if (Impl && RHS.Impl)
-      return Impl->CurrentEntry.path() == RHS.Impl->CurrentEntry.path();
-    return !Impl && !RHS.Impl;
-  }
-  bool operator!=(const directory_iterator &RHS) const {
-    return !(*this == RHS);
-  }
-};
-
-class FileSystem;
-
-namespace detail {
-
-/// Keeps state for the recursive_directory_iterator.
-struct RecDirIterState {
-  std::stack<directory_iterator, std::vector<directory_iterator>> Stack;
-  bool HasNoPushRequest = false;
-};
-
-} // end namespace detail
-
-/// An input iterator over the recursive contents of a virtual path,
-/// similar to llvm::sys::fs::recursive_directory_iterator.
-class recursive_directory_iterator {
-  FileSystem *FS;
-  std::shared_ptr<detail::RecDirIterState>
-      State; // Input iterator semantics on copy.
-
-public:
-  recursive_directory_iterator(FileSystem &FS, const Twine &Path,
-                               std::error_code &EC);
-
-  /// Construct an 'end' iterator.
-  recursive_directory_iterator() = default;
-
-  /// Equivalent to operator++, with an error code.
-  recursive_directory_iterator &increment(std::error_code &EC);
-
-  const directory_entry &operator*() const { return *State->Stack.top(); }
-  const directory_entry *operator->() const { return &*State->Stack.top(); }
-
-  bool operator==(const recursive_directory_iterator &Other) const {
-    return State == Other.State; // identity
-  }
-  bool operator!=(const recursive_directory_iterator &RHS) const {
-    return !(*this == RHS);
-  }
-
-  /// Gets the current level. Starting path is at level 0.
-  int level() const {
-    assert(!State->Stack.empty() &&
-           "Cannot get level without any iteration state");
-    return State->Stack.size() - 1;
-  }
-
-  void no_push() { State->HasNoPushRequest = true; }
-};
-
-/// The virtual file system interface.
-class FileSystem : public llvm::ThreadSafeRefCountedBase<FileSystem> {
-public:
-  virtual ~FileSystem();
-
-  /// Get the status of the entry at \p Path, if one exists.
-  virtual llvm::ErrorOr<Status> status(const Twine &Path) = 0;
-
-  /// Get a \p File object for the file at \p Path, if one exists.
-  virtual llvm::ErrorOr<std::unique_ptr<File>>
-  openFileForRead(const Twine &Path) = 0;
-
-  /// This is a convenience method that opens a file, gets its content and then
-  /// closes the file.
-  llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>>
-  getBufferForFile(const Twine &Name, int64_t FileSize = -1,
-                   bool RequiresNullTerminator = true, bool IsVolatile = false);
-
-  /// Get a directory_iterator for \p Dir.
-  /// \note The 'end' iterator is directory_iterator().
-  virtual directory_iterator dir_begin(const Twine &Dir,
-                                       std::error_code &EC) = 0;
-
-  /// Set the working directory. This will affect all following operations on
-  /// this file system and may propagate down for nested file systems.
-  virtual std::error_code setCurrentWorkingDirectory(const Twine &Path) = 0;
-
-  /// Get the working directory of this file system.
-  virtual llvm::ErrorOr<std::string> getCurrentWorkingDirectory() const = 0;
-
-  /// Gets real path of \p Path e.g. collapse all . and .. patterns, resolve
-  /// symlinks. For real file system, this uses `llvm::sys::fs::real_path`.
-  /// This returns errc::operation_not_permitted if not implemented by subclass.
-  virtual std::error_code getRealPath(const Twine &Path,
-                                      SmallVectorImpl<char> &Output) const;
-
-  /// Check whether a file exists. Provided for convenience.
-  bool exists(const Twine &Path);
-
-  /// Is the file mounted on a local filesystem?
-  virtual std::error_code isLocal(const Twine &Path, bool &Result);
-
-  /// Make \a Path an absolute path.
-  ///
-  /// Makes \a Path absolute using the current directory if it is not already.
-  /// An empty \a Path will result in the current directory.
-  ///
-  /// /absolute/path   => /absolute/path
-  /// relative/../path => <current-directory>/relative/../path
-  ///
-  /// \param Path A path that is modified to be an absolute path.
-  /// \returns success if \a path has been made absolute, otherwise a
-  ///          platform-specific error_code.
-  virtual std::error_code makeAbsolute(SmallVectorImpl<char> &Path) const;
-};
-
-/// Gets an \p vfs::FileSystem for the 'real' file system, as seen by
-/// the operating system.
-/// The working directory is linked to the process's working directory.
-/// (This is usually thread-hostile).
-IntrusiveRefCntPtr<FileSystem> getRealFileSystem();
-
-/// Create an \p vfs::FileSystem for the 'real' file system, as seen by
-/// the operating system.
-/// It has its own working directory, independent of (but initially equal to)
-/// that of the process.
-std::unique_ptr<FileSystem> createPhysicalFileSystem();
-
-/// A file system that allows overlaying one \p AbstractFileSystem on top
-/// of another.
-///
-/// Consists of a stack of >=1 \p FileSystem objects, which are treated as being
-/// one merged file system. When there is a directory that exists in more than
-/// one file system, the \p OverlayFileSystem contains a directory containing
-/// the union of their contents.  The attributes (permissions, etc.) of the
-/// top-most (most recently added) directory are used.  When there is a file
-/// that exists in more than one file system, the file in the top-most file
-/// system overrides the other(s).
-class OverlayFileSystem : public FileSystem {
-  using FileSystemList = SmallVector<IntrusiveRefCntPtr<FileSystem>, 1>;
-
-  /// The stack of file systems, implemented as a list in order of
-  /// their addition.
-  FileSystemList FSList;
-
-public:
-  OverlayFileSystem(IntrusiveRefCntPtr<FileSystem> Base);
-
-  /// Pushes a file system on top of the stack.
-  void pushOverlay(IntrusiveRefCntPtr<FileSystem> FS);
-
-  llvm::ErrorOr<Status> status(const Twine &Path) override;
-  llvm::ErrorOr<std::unique_ptr<File>>
-  openFileForRead(const Twine &Path) override;
-  directory_iterator dir_begin(const Twine &Dir, std::error_code &EC) override;
-  llvm::ErrorOr<std::string> getCurrentWorkingDirectory() const override;
-  std::error_code setCurrentWorkingDirectory(const Twine &Path) override;
-  std::error_code isLocal(const Twine &Path, bool &Result) override;
-  std::error_code getRealPath(const Twine &Path,
-                              SmallVectorImpl<char> &Output) const override;
-
-  using iterator = FileSystemList::reverse_iterator;
-  using const_iterator = FileSystemList::const_reverse_iterator;
-  using reverse_iterator = FileSystemList::iterator;
-  using const_reverse_iterator = FileSystemList::const_iterator;
-
-  /// Get an iterator pointing to the most recently added file system.
-  iterator overlays_begin() { return FSList.rbegin(); }
-  const_iterator overlays_begin() const { return FSList.rbegin(); }
-
-  /// Get an iterator pointing one-past the least recently added file system.
-  iterator overlays_end() { return FSList.rend(); }
-  const_iterator overlays_end() const { return FSList.rend(); }
-
-  /// Get an iterator pointing to the least recently added file system.
-  reverse_iterator overlays_rbegin() { return FSList.begin(); }
-  const_reverse_iterator overlays_rbegin() const { return FSList.begin(); }
-
-  /// Get an iterator pointing one-past the most recently added file system.
-  reverse_iterator overlays_rend() { return FSList.end(); }
-  const_reverse_iterator overlays_rend() const { return FSList.end(); }
-};
-
-class CaseInsensitiveFileSystem : public FileSystem {
-  IntrusiveRefCntPtr<FileSystem> Base;
-
-  /// Try to find Path by means of case-insensitive lookup. Stores the result in
-  /// FoundPath on success, or returns an error code otherwise.
-  std::error_code findCaseInsensitivePath(StringRef Path,
-                                          SmallVectorImpl<char> &FoundPath);
-
-  /// Attempt to exclude the possibility that File exists in Dir based on
-  /// previous information.
-  bool exclude(StringRef Dir, StringRef File);
-
-  /// Map from directory to map from lowercase to real-case filename.
-  llvm::StringMap<llvm::StringMap<std::string>> Maps;
-
-public:
-  CaseInsensitiveFileSystem(IntrusiveRefCntPtr<FileSystem> Base) : Base(Base) {}
-
-  llvm::ErrorOr<Status> status(const Twine &Path) override;
-  llvm::ErrorOr<std::unique_ptr<File>>
-  openFileForRead(const Twine &Path) override;
-  directory_iterator dir_begin(const Twine &Dir, std::error_code &EC) override;
-  llvm::ErrorOr<std::string> getCurrentWorkingDirectory() const override {
-    return Base->getCurrentWorkingDirectory();
-  }
-  std::error_code setCurrentWorkingDirectory(const Twine &Path) override {
-    Maps.clear();
-    return Base->setCurrentWorkingDirectory(Path);
-  }
-};
-
-/// By default, this delegates all calls to the underlying file system. This
-/// is useful when derived file systems want to override some calls and still
-/// proxy other calls.
-class ProxyFileSystem : public FileSystem {
-public:
-  explicit ProxyFileSystem(IntrusiveRefCntPtr<FileSystem> FS)
-      : FS(std::move(FS)) {}
-
-  llvm::ErrorOr<Status> status(const Twine &Path) override {
-    return FS->status(Path);
-  }
-  llvm::ErrorOr<std::unique_ptr<File>>
-  openFileForRead(const Twine &Path) override {
-    return FS->openFileForRead(Path);
-  }
-  directory_iterator dir_begin(const Twine &Dir, std::error_code &EC) override {
-    return FS->dir_begin(Dir, EC);
-  }
-  llvm::ErrorOr<std::string> getCurrentWorkingDirectory() const override {
-    return FS->getCurrentWorkingDirectory();
-  }
-  std::error_code setCurrentWorkingDirectory(const Twine &Path) override {
-    return FS->setCurrentWorkingDirectory(Path);
-  }
-  std::error_code getRealPath(const Twine &Path,
-                              SmallVectorImpl<char> &Output) const override {
-    return FS->getRealPath(Path, Output);
-  }
-  std::error_code isLocal(const Twine &Path, bool &Result) override {
-    return FS->isLocal(Path, Result);
-  }
-
-protected:
-  FileSystem &getUnderlyingFS() { return *FS; }
-
-private:
-  IntrusiveRefCntPtr<FileSystem> FS;
-
-  virtual void anchor();
-};
-
-namespace detail {
-
-class InMemoryDirectory;
-class InMemoryFile;
-class InMemoryNode;
-
-struct NewInMemoryNodeInfo {
-  llvm::sys::fs::UniqueID DirUID;
-  StringRef Path;
-  StringRef Name;
-  time_t ModificationTime;
-  std::unique_ptr<llvm::MemoryBuffer> Buffer;
-  uint32_t User;
-  uint32_t Group;
-  llvm::sys::fs::file_type Type;
-  llvm::sys::fs::perms Perms;
-
-  Status makeStatus() const;
-};
-
-} // namespace detail
-
-/// An in-memory file system.
-class InMemoryFileSystem : public FileSystem {
-  std::unique_ptr<detail::InMemoryDirectory> Root;
-  std::string WorkingDirectory;
-  bool UseNormalizedPaths = true;
-
-  using MakeNodeFn = llvm::function_ref<std::unique_ptr<detail::InMemoryNode>(
-      detail::NewInMemoryNodeInfo)>;
-
-  /// Create node with \p MakeNode and add it into this filesystem at \p Path.
-  bool addFile(const Twine &Path, time_t ModificationTime,
-               std::unique_ptr<llvm::MemoryBuffer> Buffer,
-               Optional<uint32_t> User, Optional<uint32_t> Group,
-               Optional<llvm::sys::fs::file_type> Type,
-               Optional<llvm::sys::fs::perms> Perms, MakeNodeFn MakeNode);
-
-public:
-  explicit InMemoryFileSystem(bool UseNormalizedPaths = true);
-  ~InMemoryFileSystem() override;
-
-  /// Add a file containing a buffer or a directory to the VFS with a
-  /// path. The VFS owns the buffer.  If present, User, Group, Type
-  /// and Perms apply to the newly-created file or directory.
-  /// \return true if the file or directory was successfully added,
-  /// false if the file or directory already exists in the file system with
-  /// different contents.
-  bool addFile(const Twine &Path, time_t ModificationTime,
-               std::unique_ptr<llvm::MemoryBuffer> Buffer,
-               Optional<uint32_t> User = None, Optional<uint32_t> Group = None,
-               Optional<llvm::sys::fs::file_type> Type = None,
-               Optional<llvm::sys::fs::perms> Perms = None);
-
-  /// Add a hard link to a file.
-  /// Here hard links are not intended to be fully equivalent to the classical
-  /// filesystem. Both the hard link and the file share the same buffer and
-  /// status (and thus have the same UniqueID). Because of this there is no way
-  /// to distinguish between the link and the file after the link has been
-  /// added.
-  ///
-  /// The To path must be an existing file or a hardlink. The From file must not
-  /// have been added before. The To Path must not be a directory. The From Node
-  /// is added as a hard link which points to the resolved file of To Node.
-  /// \return true if the above condition is satisfied and hardlink was
-  /// successfully created, false otherwise.
-  bool addHardLink(const Twine &From, const Twine &To);
-
-  /// Add a buffer to the VFS with a path. The VFS does not own the buffer.
-  /// If present, User, Group, Type and Perms apply to the newly-created file
-  /// or directory.
-  /// \return true if the file or directory was successfully added,
-  /// false if the file or directory already exists in the file system with
-  /// different contents.
-  bool addFileNoOwn(const Twine &Path, time_t ModificationTime,
-                    const llvm::MemoryBufferRef &Buffer,
-                    Optional<uint32_t> User = None,
-                    Optional<uint32_t> Group = None,
-                    Optional<llvm::sys::fs::file_type> Type = None,
-                    Optional<llvm::sys::fs::perms> Perms = None);
-
-  std::string toString() const;
-
-  /// Return true if this file system normalizes . and .. in paths.
-  bool useNormalizedPaths() const { return UseNormalizedPaths; }
-
-  llvm::ErrorOr<Status> status(const Twine &Path) override;
-  llvm::ErrorOr<std::unique_ptr<File>>
-  openFileForRead(const Twine &Path) override;
-  directory_iterator dir_begin(const Twine &Dir, std::error_code &EC) override;
-
-  llvm::ErrorOr<std::string> getCurrentWorkingDirectory() const override {
-    return WorkingDirectory;
-  }
-  /// Canonicalizes \p Path by combining with the current working
-  /// directory and normalizing the path (e.g. remove dots). If the current
-  /// working directory is not set, this returns errc::operation_not_permitted.
-  ///
-  /// This doesn't resolve symlinks as they are not supported in in-memory file
-  /// system.
-  std::error_code getRealPath(const Twine &Path,
-                              SmallVectorImpl<char> &Output) const override;
-  std::error_code isLocal(const Twine &Path, bool &Result) override;
-  std::error_code setCurrentWorkingDirectory(const Twine &Path) override;
-};
-
-/// Get a globally unique ID for a virtual file or directory.
-llvm::sys::fs::UniqueID getNextVirtualUniqueID();
-
-/// Gets a \p FileSystem for a virtual file system described in YAML
-/// format.
-std::unique_ptr<FileSystem>
-getVFSFromYAML(std::unique_ptr<llvm::MemoryBuffer> Buffer,
-               llvm::SourceMgr::DiagHandlerTy DiagHandler,
-               StringRef YAMLFilePath, void *DiagContext = nullptr,
-               IntrusiveRefCntPtr<FileSystem> ExternalFS = getRealFileSystem());
-
-struct YAMLVFSEntry {
-  template <typename T1, typename T2>
-  YAMLVFSEntry(T1 &&VPath, T2 &&RPath, bool IsDirectory = false)
-      : VPath(std::forward<T1>(VPath)), RPath(std::forward<T2>(RPath)),
-        IsDirectory(IsDirectory) {}
-  std::string VPath;
-  std::string RPath;
-  bool IsDirectory = false;
-};
-
-class RedirectingFSDirIterImpl;
-class RedirectingFileSystemParser;
-
-/// A virtual file system parsed from a YAML file.
-///
-/// Currently, this class allows creating virtual files and directories. Virtual
-/// files map to existing external files in \c ExternalFS, and virtual
-/// directories may either map to existing directories in \c ExternalFS or list
-/// their contents in the form of other virtual directories and/or files.
-///
-/// The basic structure of the parsed file is:
-/// \verbatim
-/// {
-///   'version': <version number>,
-///   <optional configuration>
-///   'roots': [
-///              <directory entries>
-///            ]
-/// }
-/// \endverbatim
-///
-/// The roots may be absolute or relative. If relative they will be made
-/// absolute against the current working directory.
-///
-/// All configuration options are optional.
-///   'case-sensitive': <boolean, default=(true for Posix, false for Windows)>
-///   'use-external-names': <boolean, default=true>
-///   'overlay-relative': <boolean, default=false>
-///   'fallthrough': <boolean, default=true>
-///
-/// Virtual directories that list their contents are represented as
-/// \verbatim
-/// {
-///   'type': 'directory',
-///   'name': <string>,
-///   'contents': [ <file or directory entries> ]
-/// }
-/// \endverbatim
-///
-/// The default attributes for such virtual directories are:
-/// \verbatim
-/// MTime = now() when created
-/// Perms = 0777
-/// User = Group = 0
-/// Size = 0
-/// UniqueID = unspecified unique value
-/// \endverbatim
-///
-/// When a path prefix matches such a directory, the next component in the path
-/// is matched against the entries in the 'contents' array.
-///
-/// Re-mapped directories, on the other hand, are represented as
-/// /// \verbatim
-/// {
-///   'type': 'directory-remap',
-///   'name': <string>,
-///   'use-external-name': <boolean>, # Optional
-///   'external-contents': <path to external directory>
-/// }
-/// \endverbatim
-///
-/// and inherit their attributes from the external directory. When a path
-/// prefix matches such an entry, the unmatched components are appended to the
-/// 'external-contents' path, and the resulting path is looked up in the
-/// external file system instead.
-///
-/// Re-mapped files are represented as
-/// \verbatim
-/// {
-///   'type': 'file',
-///   'name': <string>,
-///   'use-external-name': <boolean>, # Optional
-///   'external-contents': <path to external file>
-/// }
-/// \endverbatim
-///
-/// Their attributes and file contents are determined by looking up the file at
-/// their 'external-contents' path in the external file system.
-///
-/// For 'file', 'directory' and 'directory-remap' entries the 'name' field may
-/// contain multiple path components (e.g. /path/to/file). However, any
-/// directory in such a path that contains more than one child must be uniquely
-/// represented by a 'directory' entry.
-///
-/// When the 'use-external-name' field is set, calls to \a vfs::File::status()
-/// give the external (remapped) filesystem name instead of the name the file
-/// was accessed by. This is an intentional leak through the \a
-/// RedirectingFileSystem abstraction layer. It enables clients to discover
-/// (and use) the external file location when communicating with users or tools
-/// that don't use the same VFS overlay.
-///
-/// FIXME: 'use-external-name' causes behaviour that's inconsistent with how
-/// "real" filesystems behave. Maybe there should be a separate channel for
-/// this information.
-class RedirectingFileSystem : public vfs::FileSystem {
-public:
-  enum EntryKind { EK_Directory, EK_DirectoryRemap, EK_File };
-  enum NameKind { NK_NotSet, NK_External, NK_Virtual };
-
-  /// A single file or directory in the VFS.
-  class Entry {
-    EntryKind Kind;
-    std::string Name;
-
-  public:
-    Entry(EntryKind K, StringRef Name) : Kind(K), Name(Name) {}
-    virtual ~Entry() = default;
-
-    StringRef getName() const { return Name; }
-    EntryKind getKind() const { return Kind; }
-  };
-
-  /// A directory in the vfs with explicitly specified contents.
-  class DirectoryEntry : public Entry {
-    std::vector<std::unique_ptr<Entry>> Contents;
-    Status S;
-
-  public:
-    /// Constructs a directory entry with explicitly specified contents.
-    DirectoryEntry(StringRef Name, std::vector<std::unique_ptr<Entry>> Contents,
-                   Status S)
-        : Entry(EK_Directory, Name), Contents(std::move(Contents)),
-          S(std::move(S)) {}
-
-    /// Constructs an empty directory entry.
-    DirectoryEntry(StringRef Name, Status S)
-        : Entry(EK_Directory, Name), S(std::move(S)) {}
-
-    Status getStatus() { return S; }
-
-    void addContent(std::unique_ptr<Entry> Content) {
-      Contents.push_back(std::move(Content));
-    }
-
-    Entry *getLastContent() const { return Contents.back().get(); }
-
-    using iterator = decltype(Contents)::iterator;
-
-    iterator contents_begin() { return Contents.begin(); }
-    iterator contents_end() { return Contents.end(); }
-
-    static bool classof(const Entry *E) { return E->getKind() == EK_Directory; }
-  };
-
-  /// A file or directory in the vfs that is mapped to a file or directory in
-  /// the external filesystem.
-  class RemapEntry : public Entry {
-    std::string ExternalContentsPath;
-    NameKind UseName;
-
-  protected:
-    RemapEntry(EntryKind K, StringRef Name, StringRef ExternalContentsPath,
-               NameKind UseName)
-        : Entry(K, Name), ExternalContentsPath(ExternalContentsPath),
-          UseName(UseName) {}
-
-  public:
-    StringRef getExternalContentsPath() const { return ExternalContentsPath; }
-
-    /// Whether to use the external path as the name for this file or directory.
-    bool useExternalName(bool GlobalUseExternalName) const {
-      return UseName == NK_NotSet ? GlobalUseExternalName
-                                  : (UseName == NK_External);
-    }
-
-    NameKind getUseName() const { return UseName; }
-
-    static bool classof(const Entry *E) {
-      switch (E->getKind()) {
-      case EK_DirectoryRemap:
-        LLVM_FALLTHROUGH;
-      case EK_File:
-        return true;
-      case EK_Directory:
-        return false;
-      }
-      llvm_unreachable("invalid entry kind");
-    }
-  };
-
-  /// A directory in the vfs that maps to a directory in the external file
-  /// system.
-  class DirectoryRemapEntry : public RemapEntry {
-  public:
-    DirectoryRemapEntry(StringRef Name, StringRef ExternalContentsPath,
-                        NameKind UseName)
-        : RemapEntry(EK_DirectoryRemap, Name, ExternalContentsPath, UseName) {}
-
-    static bool classof(const Entry *E) {
-      return E->getKind() == EK_DirectoryRemap;
-    }
-  };
-
-  /// A file in the vfs that maps to a file in the external file system.
-  class FileEntry : public RemapEntry {
-  public:
-    FileEntry(StringRef Name, StringRef ExternalContentsPath, NameKind UseName)
-        : RemapEntry(EK_File, Name, ExternalContentsPath, UseName) {}
-
-    static bool classof(const Entry *E) { return E->getKind() == EK_File; }
-  };
-
-  /// Represents the result of a path lookup into the RedirectingFileSystem.
-  struct LookupResult {
-    /// The entry the looked-up path corresponds to.
-    Entry *E;
-
-  private:
-    /// When the found Entry is a DirectoryRemapEntry, stores the path in the
-    /// external file system that the looked-up path in the virtual file system
-    //  corresponds to.
-    Optional<std::string> ExternalRedirect;
-
-  public:
-    LookupResult(Entry *E, sys::path::const_iterator Start,
-                 sys::path::const_iterator End);
-
-    /// If the found Entry maps the the input path to a path in the external
-    /// file system (i.e. it is a FileEntry or DirectoryRemapEntry), returns
-    /// that path.
-    Optional<StringRef> getExternalRedirect() const {
-      if (isa<DirectoryRemapEntry>(E))
-        return StringRef(*ExternalRedirect);
-      if (auto *FE = dyn_cast<FileEntry>(E))
-        return FE->getExternalContentsPath();
-      return None;
-    }
-  };
-
-private:
-  friend class RedirectingFSDirIterImpl;
-  friend class RedirectingFileSystemParser;
-
-  bool shouldUseExternalFS() const { return IsFallthrough; }
-
-  /// Canonicalize path by removing ".", "..", "./", components. This is
-  /// a VFS request, do not bother about symlinks in the path components
-  /// but canonicalize in order to perform the correct entry search.
-  std::error_code makeCanonical(SmallVectorImpl<char> &Path) const;
-
-  /// Whether to fall back to the external file system when an operation fails
-  /// with the given error code on a path associated with the provided Entry.
-  bool shouldFallBackToExternalFS(std::error_code EC, Entry *E = nullptr) const;
-
-  /// Get the File status, or error, from the underlying external file system.
-  /// This returns the status with the originally requested name, while looking
-  /// up the entry using the canonical path.
-  ErrorOr<Status> getExternalStatus(const Twine &CanonicalPath,
-                                    const Twine &OriginalPath) const;
-
-  // In a RedirectingFileSystem, keys can be specified in Posix or Windows
-  // style (or even a mixture of both), so this comparison helper allows
-  // slashes (representing a root) to match backslashes (and vice versa).  Note
-  // that, other than the root, path components should not contain slashes or
-  // backslashes.
-  bool pathComponentMatches(llvm::StringRef lhs, llvm::StringRef rhs) const {
-    if ((CaseSensitive ? lhs.equals(rhs) : lhs.equals_insensitive(rhs)))
-      return true;
-    return (lhs == "/" && rhs == "\\") || (lhs == "\\" && rhs == "/");
-  }
-
-  /// The root(s) of the virtual file system.
-  std::vector<std::unique_ptr<Entry>> Roots;
-
-  /// The current working directory of the file system.
-  std::string WorkingDirectory;
-
-  /// The file system to use for external references.
-  IntrusiveRefCntPtr<FileSystem> ExternalFS;
-
-  /// If IsRelativeOverlay is set, this represents the directory
-  /// path that should be prefixed to each 'external-contents' entry
-  /// when reading from YAML files.
-  std::string ExternalContentsPrefixDir;
-
-  /// @name Configuration
-  /// @{
-
-  /// Whether to perform case-sensitive comparisons.
-  ///
-  /// Currently, case-insensitive matching only works correctly with ASCII.
-  bool CaseSensitive = is_style_posix(sys::path::Style::native);
-
-  /// IsRelativeOverlay marks whether a ExternalContentsPrefixDir path must
-  /// be prefixed in every 'external-contents' when reading from YAML files.
-  bool IsRelativeOverlay = false;
-
-  /// Whether to use to use the value of 'external-contents' for the
-  /// names of files.  This global value is overridable on a per-file basis.
-  bool UseExternalNames = true;
-
-  /// Whether to attempt a file lookup in external file system after it wasn't
-  /// found in VFS.
-  bool IsFallthrough = true;
-  /// @}
-
-  RedirectingFileSystem(IntrusiveRefCntPtr<FileSystem> ExternalFS);
-
-  /// Looks up the path <tt>[Start, End)</tt> in \p From, possibly recursing
-  /// into the contents of \p From if it is a directory. Returns a LookupResult
-  /// giving the matched entry and, if that entry is a FileEntry or
-  /// DirectoryRemapEntry, the path it redirects to in the external file system.
-  ErrorOr<LookupResult> lookupPathImpl(llvm::sys::path::const_iterator Start,
-                                       llvm::sys::path::const_iterator End,
-                                       Entry *From) const;
-
-  /// Get the status for a path with the provided \c LookupResult.
-  ErrorOr<Status> status(const Twine &CanonicalPath, const Twine &OriginalPath,
-                         const LookupResult &Result);
-
-public:
-  /// Looks up \p Path in \c Roots and returns a LookupResult giving the
-  /// matched entry and, if the entry was a FileEntry or DirectoryRemapEntry,
-  /// the path it redirects to in the external file system.
-  ErrorOr<LookupResult> lookupPath(StringRef Path) const;
-
-  /// Parses \p Buffer, which is expected to be in YAML format and
-  /// returns a virtual file system representing its contents.
-  static std::unique_ptr<RedirectingFileSystem>
-  create(std::unique_ptr<MemoryBuffer> Buffer,
-         SourceMgr::DiagHandlerTy DiagHandler, StringRef YAMLFilePath,
-         void *DiagContext, IntrusiveRefCntPtr<FileSystem> ExternalFS);
-
-  /// Redirect each of the remapped files from first to second.
-  static std::unique_ptr<RedirectingFileSystem>
-  create(ArrayRef<std::pair<std::string, std::string>> RemappedFiles,
-         bool UseExternalNames, FileSystem &ExternalFS);
-
-  ErrorOr<Status> status(const Twine &Path) override;
-  ErrorOr<std::unique_ptr<File>> openFileForRead(const Twine &Path) override;
-
-  std::error_code getRealPath(const Twine &Path,
-                              SmallVectorImpl<char> &Output) const override;
-
-  llvm::ErrorOr<std::string> getCurrentWorkingDirectory() const override;
-
-  std::error_code setCurrentWorkingDirectory(const Twine &Path) override;
-
-  std::error_code isLocal(const Twine &Path, bool &Result) override;
-
-  std::error_code makeAbsolute(SmallVectorImpl<char> &Path) const override;
-
-  directory_iterator dir_begin(const Twine &Dir, std::error_code &EC) override;
-
-  void setExternalContentsPrefixDir(StringRef PrefixDir);
-
-  StringRef getExternalContentsPrefixDir() const;
-
-  void setFallthrough(bool Fallthrough);
-
-  std::vector<llvm::StringRef> getRoots() const;
-
-  void dump(raw_ostream &OS) const;
-  void dumpEntry(raw_ostream &OS, Entry *E, int NumSpaces = 0) const;
-#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
-  LLVM_DUMP_METHOD void dump() const;
-#endif
-};
-
-/// Collect all pairs of <virtual path, real path> entries from the
-/// \p YAMLFilePath. This is used by the module dependency collector to forward
-/// the entries into the reproducer output VFS YAML file.
-void collectVFSFromYAML(
-    std::unique_ptr<llvm::MemoryBuffer> Buffer,
-    llvm::SourceMgr::DiagHandlerTy DiagHandler, StringRef YAMLFilePath,
-    SmallVectorImpl<YAMLVFSEntry> &CollectedEntries,
-    void *DiagContext = nullptr,
-    IntrusiveRefCntPtr<FileSystem> ExternalFS = getRealFileSystem());
-
-class YAMLVFSWriter {
-  std::vector<YAMLVFSEntry> Mappings;
-  Optional<bool> IsCaseSensitive;
-  Optional<bool> IsOverlayRelative;
-  Optional<bool> UseExternalNames;
-  std::string OverlayDir;
-
-  void addEntry(StringRef VirtualPath, StringRef RealPath, bool IsDirectory);
-
-public:
-  YAMLVFSWriter() = default;
-
-  void addFileMapping(StringRef VirtualPath, StringRef RealPath);
-  void addDirectoryMapping(StringRef VirtualPath, StringRef RealPath);
-
-  void setCaseSensitivity(bool CaseSensitive) {
-    IsCaseSensitive = CaseSensitive;
-  }
-
-  void setUseExternalNames(bool UseExtNames) { UseExternalNames = UseExtNames; }
-
-  void setOverlayDir(StringRef OverlayDirectory) {
-    IsOverlayRelative = true;
-    OverlayDir.assign(OverlayDirectory.str());
-  }
-
-  const std::vector<YAMLVFSEntry> &getMappings() const { return Mappings; }
-
-  void write(llvm::raw_ostream &OS);
-};
-
-} // namespace vfs
-} // namespace llvm
-
-#endif // LLVM_SUPPORT_VIRTUALFILESYSTEM_H
-
-#ifdef __GNUC__
-#pragma GCC diagnostic pop
-#endif