Index: include/clang/Tooling/Core/Diagnostic.h
===================================================================
--- include/clang/Tooling/Core/Diagnostic.h
+++ include/clang/Tooling/Core/Diagnostic.h
@@ -0,0 +1,78 @@
+//===--- Diagnostic.h - Framework for clang diagnostics tools --*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// \file
+//  Structures supporting diagnostics and refactorings that span multiple
+//  translation units. Indicate diagnostics reports and replacements
+//  suggestions for the analyzed sources.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_TOOLING_CORE_DIAGNOSTIC_H
+#define LLVM_CLANG_TOOLING_CORE_DIAGNOSTIC_H
+
+#include "Replacement.h"
+#include "clang/Basic/Diagnostic.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/StringMap.h"
+#include "llvm/ADT/StringRef.h"
+#include <string>
+
+namespace clang {
+namespace tooling {
+
+/// \brief Represents the diagnostic message with the error message associated
+/// and theinformation on the location of the problem.
+struct DiagnosticMessage {
+  DiagnosticMessage(llvm::StringRef Message = "");
+  DiagnosticMessage(llvm::StringRef Message, const SourceManager &Sources,
+                    SourceLocation Loc);
+  std::string Message;
+  std::string FilePath;
+  unsigned FileOffset;
+};
+
+/// \brief Represents the diagnostic with the level of severity and possible
+/// fixes to be applied.
+struct Diagnostic {
+  enum Level {
+    Warning = DiagnosticsEngine::Warning,
+    Error = DiagnosticsEngine::Error
+  };
+
+  Diagnostic() = default;
+
+  Diagnostic(llvm::StringRef CheckName, Level DiagLevel);
+
+  Diagnostic(llvm::StringRef CheckName, DiagnosticMessage &Message,
+             llvm::StringMap<tooling::Replacements> &Fix,
+             SmallVector<DiagnosticMessage, 1> &Notes, Level DiagLevel);
+
+  std::string CheckName;
+  DiagnosticMessage Message;
+  // Fixes grouped by file path.
+  llvm::StringMap<tooling::Replacements> Fix;
+  SmallVector<DiagnosticMessage, 1> Notes;
+  Level DiagLevel;
+};
+
+/// \brief Collection of Diagnostics generated from a single translation unit.
+struct TranslationUnitDiagnostics {
+  std::string MainSourceFile;
+  /// A freeform chunk of text to describe the context of the replacements.
+  /// Will be printed, for example, when detecting conflicts during replacement
+  /// deduplication.
+  std::string Context;
+
+  std::vector<Diagnostic> Diagnostics;
+};
+
+} // end namespace tooling
+} // end namespace clang
+#endif // LLVM_CLANG_TOOLING_CORE_DIAGNOSTIC_H
Index: include/clang/Tooling/DiagnosticsYaml.h
===================================================================
--- include/clang/Tooling/DiagnosticsYaml.h
+++ include/clang/Tooling/DiagnosticsYaml.h
@@ -0,0 +1,77 @@
+//===-- DiagnosticsYaml.h -- Serialiazation for Diagnosticss ---*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// \brief This file defines the structure of a YAML document for serializing
+/// diagnostics.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_TOOLING_DIAGNOSTICSYAML_H
+#define LLVM_CLANG_TOOLING_DIAGNOSTICSYAML_H
+
+#include "clang/Tooling/Core/Diagnostic.h"
+#include "clang/Tooling/ReplacementsYaml.h"
+#include "llvm/Support/YAMLTraits.h"
+#include <string>
+
+LLVM_YAML_IS_SEQUENCE_VECTOR(clang::tooling::Diagnostic)
+
+namespace llvm {
+namespace yaml {
+
+template <> struct MappingTraits<clang::tooling::Diagnostic> {
+  /// \brief Helper to (de)serialize a Diagnostic since we don't have direct
+  /// access to its data members.
+  class NormalizedDiagnostic {
+  public:
+    NormalizedDiagnostic(const IO &)
+        : CheckName(""), Message(), Fix(), Notes(), DiagLevel() {}
+
+    NormalizedDiagnostic(const IO &, const clang::tooling::Diagnostic &D)
+        : CheckName(D.CheckName), Message(Message), Fix(D.Fix), Notes(D.Notes),
+          DiagLevel(D.DiagLevel) {}
+
+    clang::tooling::Diagnostic denormalize(const IO &) {
+      return clang::tooling::Diagnostic(CheckName, Message, Fix, Notes,
+                                        DiagLevel);
+    }
+
+    std::string CheckName;
+    clang::tooling::DiagnosticMessage Message;
+    llvm::StringMap<clang::tooling::Replacements> Fix;
+    SmallVector<clang::tooling::DiagnosticMessage, 1> Notes;
+    clang::tooling::Diagnostic::Level DiagLevel;
+  };
+
+  static void mapping(IO &Io, clang::tooling::Diagnostic &D) {
+    MappingNormalization<NormalizedDiagnostic, clang::tooling::Diagnostic> Keys(
+        Io, D);
+    Io.mapRequired("CheckName", Keys->CheckName);
+    std::vector<clang::tooling::Replacement> Fixes;
+    Io.mapRequired("Replacements", Fixes);
+    for (auto &Fix : Fixes) {
+      Keys->Fix[Fix.getFilePath()].add(Fix);
+    }
+  }
+};
+
+/// \brief Specialized MappingTraits to describe how a
+/// TranslationUnitDiagnostics is (de)serialized.
+template <> struct MappingTraits<clang::tooling::TranslationUnitDiagnostics> {
+  static void mapping(IO &Io, clang::tooling::TranslationUnitDiagnostics &Doc) {
+    Io.mapRequired("MainSourceFile", Doc.MainSourceFile);
+    Io.mapOptional("Context", Doc.Context, std::string());
+    Io.mapRequired("Diagnostics", Doc.Diagnostics);
+  }
+};
+} // end namespace yaml
+} // end namespace llvm
+
+#endif // LLVM_CLANG_TOOLING_DIAGNOSTICSYAML_H
Index: lib/Tooling/Core/CMakeLists.txt
===================================================================
--- lib/Tooling/Core/CMakeLists.txt
+++ lib/Tooling/Core/CMakeLists.txt
@@ -4,6 +4,7 @@
   Lookup.cpp
   Replacement.cpp
   QualTypeNames.cpp
+  Diagnostic.cpp
 
   LINK_LIBS
   clangAST
Index: lib/Tooling/Core/Diagnostic.cpp
===================================================================
--- lib/Tooling/Core/Diagnostic.cpp
+++ lib/Tooling/Core/Diagnostic.cpp
@@ -0,0 +1,43 @@
+//===--- Diagnostic.cpp - Framework for clang diagnostics tools ----------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+//  Implements classes to support/store diagnostics refactoring.
+//
+//===----------------------------------------------------------------------===//
+
+#include "clang/Tooling/Core/Diagnostic.h"
+#include "clang/Basic/SourceManager.h"
+
+namespace clang {
+namespace tooling {
+
+DiagnosticMessage::DiagnosticMessage(llvm::StringRef Message)
+    : Message(Message), FileOffset(0) {}
+
+DiagnosticMessage::DiagnosticMessage(llvm::StringRef Message,
+                                     const SourceManager &Sources,
+                                     SourceLocation Loc)
+    : Message(Message) {
+  assert(Loc.isValid() && Loc.isFileID());
+  FilePath = Sources.getFilename(Loc);
+  FileOffset = Sources.getFileOffset(Loc);
+}
+
+Diagnostic::Diagnostic(llvm::StringRef CheckName, Diagnostic::Level DiagLevel)
+    : CheckName(CheckName), DiagLevel(DiagLevel) {}
+
+Diagnostic::Diagnostic(llvm::StringRef CheckName, DiagnosticMessage &Message,
+                       llvm::StringMap<tooling::Replacements> &Fix,
+                       SmallVector<DiagnosticMessage, 1> &Notes,
+                       Level DiagLevel)
+    : CheckName(CheckName), Message(Message), Fix(Fix), Notes(Notes),
+      DiagLevel(DiagLevel) {}
+
+} // end namespace tooling
+} // end namespace clang
Index: tools/extra/clang-apply-replacements/include/clang-apply-replacements/Tooling/ApplyReplacements.h
===================================================================
--- tools/extra/clang-apply-replacements/include/clang-apply-replacements/Tooling/ApplyReplacements.h
+++ tools/extra/clang-apply-replacements/include/clang-apply-replacements/Tooling/ApplyReplacements.h
@@ -16,6 +16,7 @@
 #ifndef LLVM_CLANG_APPLYREPLACEMENTS_H
 #define LLVM_CLANG_APPLYREPLACEMENTS_H
 
+#include "clang/Tooling/Core/Diagnostic.h"
 #include "clang/Tooling/Refactoring.h"
 #include "llvm/ADT/StringMap.h"
 #include "llvm/ADT/StringRef.h"
@@ -37,12 +38,12 @@
 /// \brief Collection of source ranges.
 typedef std::vector<clang::tooling::Range> RangeVector;
 
-/// \brief Collection of TranslationUnitReplacements.
-typedef std::vector<clang::tooling::TranslationUnitReplacements>
-TUReplacements;
+/// \brief Collection of TranslationUniDiagnostics.
+typedef std::vector<clang::tooling::TranslationUnitDiagnostics>
+TUDiagnostics;
 
-/// \brief Collection of TranslationUnitReplacement files.
-typedef std::vector<std::string> TUReplacementFiles;
+/// \brief Collection of TranslationUnitDiagnostic files.
+typedef std::vector<std::string> TUDiagnosticFiles;
 
 /// \brief Map mapping file name to Replacements targeting that file.
 typedef llvm::DenseMap<const clang::FileEntry *,
@@ -68,8 +69,8 @@
 /// directory structure.
 std::error_code
 collectReplacementsFromDirectory(const llvm::StringRef Directory,
-                                 TUReplacements &TUs,
-                                 TUReplacementFiles &TURFiles,
+                                 TUDiagnostics &TUs,
+                                 TUDiagnosticFiles &TURFiles,
                                  clang::DiagnosticsEngine &Diagnostics);
 
 /// \brief Deduplicate, check for conflicts, and apply all Replacements stored
@@ -87,7 +88,7 @@
 /// \returns \parblock
 ///          \li true If all changes were applied successfully.
 ///          \li false If there were conflicts.
-bool mergeAndDeduplicate(const TUReplacements &TUs,
+bool mergeAndDeduplicate(const TUDiagnostics &TUs,
                          FileToReplacementsMap &GroupedReplacements,
                          clang::SourceManager &SM);
 
@@ -127,16 +128,16 @@
 /// \param[in] Rewrites Rewriter containing written files to write to disk.
 bool writeFiles(const clang::Rewriter &Rewrites);
 
-/// \brief Delete the replacement files.
+/// \brief Delete the diagnostic files.
 ///
-/// \param[in] Files Replacement files to delete.
+/// \param[in] Files Diagnosic files to delete.
 /// \param[in] Diagnostics DiagnosticsEngine used for error output.
 ///
 /// \returns \parblock
 ///          \li true If all files have been deleted successfully.
 ///          \li false If at least one or more failures occur when deleting
 /// files.
-bool deleteReplacementFiles(const TUReplacementFiles &Files,
+bool deleteDiagnosticFiles(const TUDiagnosticFiles &Files,
                             clang::DiagnosticsEngine &Diagnostics);
 
 } // end namespace replace
Index: tools/extra/clang-apply-replacements/lib/Tooling/ApplyReplacements.cpp
===================================================================
--- tools/extra/clang-apply-replacements/lib/Tooling/ApplyReplacements.cpp
+++ tools/extra/clang-apply-replacements/lib/Tooling/ApplyReplacements.cpp
@@ -20,7 +20,7 @@
 #include "clang/Format/Format.h"
 #include "clang/Lex/Lexer.h"
 #include "clang/Rewrite/Core/Rewriter.h"
-#include "clang/Tooling/ReplacementsYaml.h"
+#include "clang/Tooling/DiagnosticsYaml.h"
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/MemoryBuffer.h"
@@ -38,8 +38,8 @@
 
 std::error_code
 collectReplacementsFromDirectory(const llvm::StringRef Directory,
-                                 TUReplacements &TUs,
-                                 TUReplacementFiles & TURFiles,
+                                 TUDiagnostics &TUs,
+                                 TUDiagnosticFiles & TURFiles,
                                  clang::DiagnosticsEngine &Diagnostics) {
   using namespace llvm::sys::fs;
   using namespace llvm::sys::path;
@@ -68,7 +68,7 @@
     }
 
     yaml::Input YIn(Out.get()->getBuffer(), nullptr, &eatDiagnostics);
-    tooling::TranslationUnitReplacements TU;
+    tooling::TranslationUnitDiagnostics TU;
     YIn >> TU;
     if (YIn.error()) {
       // File doesn't appear to be a header change description. Ignore it.
@@ -238,23 +238,27 @@
   return conflictsFound;
 }
 
-bool mergeAndDeduplicate(const TUReplacements &TUs,
+bool mergeAndDeduplicate(const TUDiagnostics &TUs,
                          FileToReplacementsMap &GroupedReplacements,
                          clang::SourceManager &SM) {
 
   // Group all replacements by target file.
   std::set<StringRef> Warned;
   for (const auto &TU : TUs) {
-    for (const tooling::Replacement &R : TU.Replacements) {
-      // Use the file manager to deduplicate paths. FileEntries are
-      // automatically canonicalized.
-      const FileEntry *Entry = SM.getFileManager().getFile(R.getFilePath());
-      if (!Entry && Warned.insert(R.getFilePath()).second) {
-        errs() << "Described file '" << R.getFilePath()
-               << "' doesn't exist. Ignoring...\n";
-        continue;
+    for (const auto &D : TU.Diagnostics) {
+      for (const auto &Fix : D.Fix) {
+        for (const tooling::Replacement &R : Fix.second) {
+          // Use the file manager to deduplicate paths. FileEntries are
+          // automatically canonicalized.
+          const FileEntry *Entry = SM.getFileManager().getFile(R.getFilePath());
+          if (!Entry && Warned.insert(R.getFilePath()).second) {
+            errs() << "Described file '" << R.getFilePath()
+                   << "' doesn't exist. Ignoring...\n";
+            continue;
+          }
+          GroupedReplacements[Entry].push_back(R);
+        }
       }
-      GroupedReplacements[Entry].push_back(R);
     }
   }
 
@@ -315,7 +319,7 @@
   return true;
 }
 
-bool deleteReplacementFiles(const TUReplacementFiles &Files,
+bool deleteDiagnosticFiles(const TUDiagnosticFiles &Files,
                             clang::DiagnosticsEngine &Diagnostics) {
   bool Success = true;
   for (const auto &Filename : Files) {
Index: tools/extra/clang-apply-replacements/tool/ClangApplyReplacementsMain.cpp
===================================================================
--- tools/extra/clang-apply-replacements/tool/ClangApplyReplacementsMain.cpp
+++ tools/extra/clang-apply-replacements/tool/ClangApplyReplacementsMain.cpp
@@ -37,7 +37,7 @@
 const cl::OptionCategory *VisibleCategories[] = {&ReplacementCategory,
                                                  &FormattingCategory};
 
-static cl::opt<bool> RemoveTUReplacementFiles(
+static cl::opt<bool> RemoveTUDiagnosticFiles(
     "remove-change-desc-files",
     cl::desc("Remove the change description files regardless of successful\n"
              "merging/replacing."),
@@ -71,16 +71,16 @@
 // "remove-change-desc-files" command line option) when exiting current scope.
 class ScopedFileRemover {
 public:
-  ScopedFileRemover(const TUReplacementFiles &Files,
+  ScopedFileRemover(const TUDiagnosticFiles &Files,
                     clang::DiagnosticsEngine &Diagnostics)
-      : TURFiles(Files), Diag(Diagnostics) {}
+      : TUDFiles(Files), Diag(Diagnostics) {}
 
   ~ScopedFileRemover() {
-    deleteReplacementFiles(TURFiles, Diag);
+    deleteDiagnosticFiles(TUDFiles, Diag);
   }
 
 private:
-  const TUReplacementFiles &TURFiles;
+  const TUDiagnosticFiles &TUDFiles;
   clang::DiagnosticsEngine &Diag;
 };
 } // namespace
@@ -214,11 +214,11 @@
   if (DoFormat)
     FormatStyle = format::getStyle(FormatStyleOpt, FormatStyleConfig, "LLVM");
 
-  TUReplacements TUs;
-  TUReplacementFiles TURFiles;
-
+  TUDiagnostics TUs;
+  TUDiagnosticFiles TUDFiles;
+  __debugbreak();
   std::error_code ErrorCode =
-      collectReplacementsFromDirectory(Directory, TUs, TURFiles, Diagnostics);
+      collectReplacementsFromDirectory(Directory, TUs, TUDFiles, Diagnostics);
 
   if (ErrorCode) {
     errs() << "Trouble iterating over directory '" << Directory
@@ -229,8 +229,8 @@
   // Remove the TUReplacementFiles (triggered by "remove-change-desc-files"
   // command line option) when exiting main().
   std::unique_ptr<ScopedFileRemover> Remover;
-  if (RemoveTUReplacementFiles)
-    Remover.reset(new ScopedFileRemover(TURFiles, Diagnostics));
+  if (RemoveTUDiagnosticFiles)
+    Remover.reset(new ScopedFileRemover(TUDFiles, Diagnostics));
 
   FileManager Files((FileSystemOptions()));
   SourceManager SM(Diagnostics, Files);
Index: tools/extra/clang-tidy/ClangTidy.cpp
===================================================================
--- tools/extra/clang-tidy/ClangTidy.cpp
+++ tools/extra/clang-tidy/ClangTidy.cpp
@@ -35,6 +35,7 @@
 #include "clang/Rewrite/Frontend/FrontendActions.h"
 #include "clang/StaticAnalyzer/Core/BugReporter/PathDiagnostic.h"
 #include "clang/StaticAnalyzer/Frontend/AnalysisConsumer.h"
+#include "clang/Tooling/DiagnosticsYaml.h"
 #include "clang/Tooling/Refactoring.h"
 #include "clang/Tooling/ReplacementsYaml.h"
 #include "clang/Tooling/Tooling.h"
@@ -574,16 +575,10 @@
 
 void exportReplacements(const std::vector<ClangTidyError> &Errors,
                         raw_ostream &OS) {
-  TranslationUnitReplacements TUR;
-  for (const ClangTidyError &Error : Errors) {
-    for (const auto &FileAndFixes : Error.Fix)
-      TUR.Replacements.insert(TUR.Replacements.end(),
-                              FileAndFixes.second.begin(),
-                              FileAndFixes.second.end());
-  }
-
+  TranslationUnitDiagnostics TUD;
+  TUD.Diagnostics.insert(TUD.Diagnostics.end(), Errors.begin(), Errors.end());
   yaml::Output YAML(OS);
-  YAML << TUR;
+  YAML << TUD;
 }
 
 } // namespace tidy
Index: tools/extra/clang-tidy/ClangTidyDiagnosticConsumer.h
===================================================================
--- tools/extra/clang-tidy/ClangTidyDiagnosticConsumer.h
+++ tools/extra/clang-tidy/ClangTidyDiagnosticConsumer.h
@@ -13,6 +13,7 @@
 #include "ClangTidyOptions.h"
 #include "clang/Basic/Diagnostic.h"
 #include "clang/Basic/SourceManager.h"
+#include "clang/Tooling/Core/Diagnostic.h"
 #include "clang/Tooling/Refactoring.h"
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/StringMap.h"
@@ -32,17 +33,7 @@
 
 namespace tidy {
 
-/// \brief A message from a clang-tidy check.
-///
-/// Note that this is independent of a \c SourceManager.
-struct ClangTidyMessage {
-  ClangTidyMessage(StringRef Message = "");
-  ClangTidyMessage(StringRef Message, const SourceManager &Sources,
-                   SourceLocation Loc);
-  std::string Message;
-  std::string FilePath;
-  unsigned FileOffset;
-};
+typedef clang::tooling::DiagnosticMessage ClangTidyMessage;
 
 /// \brief A detected error complete with information to display diagnostic and
 /// automatic fix.
@@ -51,21 +42,10 @@
 /// dependency on a SourceManager.
 ///
 /// FIXME: Make Diagnostics flexible enough to support this directly.
-struct ClangTidyError {
-  enum Level {
-    Warning = DiagnosticsEngine::Warning,
-    Error = DiagnosticsEngine::Error
-  };
-
+struct ClangTidyError : clang::tooling::Diagnostic {
   ClangTidyError(StringRef CheckName, Level DiagLevel, bool IsWarningAsError,
                  StringRef BuildDirectory);
 
-  std::string CheckName;
-  ClangTidyMessage Message;
-  // Fixes grouped by file path.
-  llvm::StringMap<tooling::Replacements> Fix;
-  SmallVector<ClangTidyMessage, 1> Notes;
-
   // A build directory of the diagnostic source file.
   //
   // It's an absolute path which is `directory` field of the source file in
@@ -75,7 +55,6 @@
   // Note: it is empty in unittest.
   std::string BuildDirectory;
 
-  Level DiagLevel;
   bool IsWarningAsError;
 };
 
Index: tools/extra/clang-tidy/ClangTidyDiagnosticConsumer.cpp
===================================================================
--- tools/extra/clang-tidy/ClangTidyDiagnosticConsumer.cpp
+++ tools/extra/clang-tidy/ClangTidyDiagnosticConsumer.cpp
@@ -110,24 +110,11 @@
 };
 } // end anonymous namespace
 
-ClangTidyMessage::ClangTidyMessage(StringRef Message)
-    : Message(Message), FileOffset(0) {}
-
-ClangTidyMessage::ClangTidyMessage(StringRef Message,
-                                   const SourceManager &Sources,
-                                   SourceLocation Loc)
-    : Message(Message) {
-  assert(Loc.isValid() && Loc.isFileID());
-  FilePath = Sources.getFilename(Loc);
-  FileOffset = Sources.getFileOffset(Loc);
-}
-
 ClangTidyError::ClangTidyError(StringRef CheckName,
                                ClangTidyError::Level DiagLevel,
-                               bool IsWarningAsError,
-                               StringRef BuildDirectory)
-    : CheckName(CheckName), BuildDirectory(BuildDirectory), DiagLevel(DiagLevel),
-      IsWarningAsError(IsWarningAsError) {}
+                               bool IsWarningAsError, StringRef BuildDirectory)
+    : clang::tooling::Diagnostic(CheckName, DiagLevel),
+      BuildDirectory(BuildDirectory), IsWarningAsError(IsWarningAsError) {}
 
 // Returns true if GlobList starts with the negative indicator ('-'), removes it
 // from the GlobList.