Index: clang-tidy/ClangTidy.cpp
===================================================================
--- clang-tidy/ClangTidy.cpp
+++ clang-tidy/ClangTidy.cpp
@@ -104,31 +104,28 @@
     DiagPrinter->BeginSourceFile(LangOpts);
   }
 
-  void reportDiagnostic(const ClangTidyMessage &Message,
-                        DiagnosticsEngine::Level Level,
-                        const tooling::Replacements *Fixes = nullptr) {
+  void reportDiagnostic(const ClangTidyError &Error) {
+    const ClangTidyMessage &Message = Error.Message;
     SourceLocation Loc = getLocation(Message.FilePath, Message.FileOffset);
     // Contains a pair for each attempted fix: location and whether the fix was
     // applied successfully.
     SmallVector<std::pair<SourceLocation, bool>, 4> FixLocations;
     {
+      auto Level = static_cast<DiagnosticsEngine::Level>(Error.DiagLevel);
       DiagnosticBuilder Diag =
-          Diags.Report(Loc, Diags.getCustomDiagID(Level, "%0"))
-          << Message.Message;
-      if (Fixes != nullptr) {
-        for (const tooling::Replacement &Fix : *Fixes) {
-          SourceLocation FixLoc =
-              getLocation(Fix.getFilePath(), Fix.getOffset());
-          SourceLocation FixEndLoc = FixLoc.getLocWithOffset(Fix.getLength());
-          Diag << FixItHint::CreateReplacement(SourceRange(FixLoc, FixEndLoc),
-                                               Fix.getReplacementText());
-          ++TotalFixes;
-          if (ApplyFixes) {
-            bool Success = Fix.isApplicable() && Fix.apply(Rewrite);
-            if (Success)
-              ++AppliedFixes;
-            FixLocations.push_back(std::make_pair(FixLoc, Success));
-          }
+          Diags.Report(Loc, Diags.getCustomDiagID(Level, "%0 [%1]"))
+          << Message.Message << Error.CheckName;
+      for (const tooling::Replacement &Fix : Error.Fix) {
+        SourceLocation FixLoc = getLocation(Fix.getFilePath(), Fix.getOffset());
+        SourceLocation FixEndLoc = FixLoc.getLocWithOffset(Fix.getLength());
+        Diag << FixItHint::CreateReplacement(SourceRange(FixLoc, FixEndLoc),
+                                             Fix.getReplacementText());
+        ++TotalFixes;
+        if (ApplyFixes) {
+          bool Success = Fix.isApplicable() && Fix.apply(Rewrite);
+          if (Success)
+            ++AppliedFixes;
+          FixLocations.push_back(std::make_pair(FixLoc, Success));
         }
       }
     }
@@ -136,6 +133,8 @@
       Diags.Report(Fix.first, Fix.second ? diag::note_fixit_applied
                                          : diag::note_fixit_failed);
     }
+    for (const ClangTidyMessage &Note : Error.Notes)
+      reportNote(Note);
   }
 
   void Finish() {
@@ -157,6 +156,13 @@
     return SourceMgr.getLocForStartOfFile(ID).getLocWithOffset(Offset);
   }
 
+  void reportNote(const ClangTidyMessage &Message) {
+    SourceLocation Loc = getLocation(Message.FilePath, Message.FileOffset);
+    DiagnosticBuilder Diag =
+        Diags.Report(Loc, Diags.getCustomDiagID(DiagnosticsEngine::Note, "%0"))
+        << Message.Message;
+  }
+
   FileManager Files;
   LangOptions LangOpts; // FIXME: use langopts from each original file
   IntrusiveRefCntPtr<DiagnosticOptions> DiagOpts;
@@ -349,13 +355,8 @@
 
 void handleErrors(const std::vector<ClangTidyError> &Errors, bool Fix) {
   ErrorReporter Reporter(Fix);
-  for (const ClangTidyError &Error : Errors) {
-    Reporter.reportDiagnostic(
-        Error.Message, static_cast<DiagnosticsEngine::Level>(Error.DiagLevel),
-        &Error.Fix);
-    for (const ClangTidyMessage &Note : Error.Notes)
-      Reporter.reportDiagnostic(Note, DiagnosticsEngine::Note);
-  }
+  for (const ClangTidyError &Error : Errors)
+    Reporter.reportDiagnostic(Error);
   Reporter.Finish();
 }
 
Index: clang-tidy/ClangTidyDiagnosticConsumer.cpp
===================================================================
--- clang-tidy/ClangTidyDiagnosticConsumer.cpp
+++ clang-tidy/ClangTidyDiagnosticConsumer.cpp
@@ -40,6 +40,14 @@
                              ArrayRef<CharSourceRange> Ranges,
                              const SourceManager *SM,
                              DiagOrStoredDiag Info) override {
+    // Remove check name from the message.
+    // FIXME: Remove this once there's a better way to pass check names than
+    // appending the check name to the message in ClangTidyContext::diag and
+    // using getCustomDiagID.
+    std::string CheckNameInMessage = " [" + Error.CheckName + "]";
+    if (Message.endswith(CheckNameInMessage))
+      Message = Message.substr(0, Message.size() - CheckNameInMessage.size());
+
     ClangTidyMessage TidyMessage = Loc.isValid()
                                        ? ClangTidyMessage(Message, *SM, Loc)
                                        : ClangTidyMessage(Message);
@@ -259,7 +267,6 @@
     assert(!Errors.empty() &&
            "A diagnostic note can only be appended to a message.");
   } else {
-    // FIXME: Pass all errors here regardless of filters and non-user code.
     finalizeLastError();
     StringRef WarningOption =
         Context.DiagEngine->getDiagnosticIDs()->getWarningOptionForDiag(
@@ -268,9 +275,28 @@
                                 ? ("clang-diagnostic-" + WarningOption).str()
                                 : Context.getCheckName(Info.getID()).str();
 
+    if (CheckName.empty()) {
+      // This is a compiler diagnostic without a warning option. Assign check
+      // name based on its level.
+      switch (DiagLevel) {
+        case DiagnosticsEngine::Error:
+        case DiagnosticsEngine::Fatal:
+          CheckName = "clang-diagnostic-error";
+          break;
+        case DiagnosticsEngine::Warning:
+          CheckName = "clang-diagnostic-warning";
+          break;
+        default:
+          CheckName = "clang-diagnostic-unknown";
+          break;
+      }
+    }
+
     ClangTidyError::Level Level = ClangTidyError::Warning;
     if (DiagLevel == DiagnosticsEngine::Error ||
         DiagLevel == DiagnosticsEngine::Fatal) {
+      // Force reporting of Clang errors regardless of filters and non-user
+      // code.
       Level = ClangTidyError::Error;
       LastErrorRelatesToUserCode = true;
       LastErrorPassesLineFilter = true;
Index: test/clang-tidy/diagnostic.cpp
===================================================================
--- test/clang-tidy/diagnostic.cpp
+++ test/clang-tidy/diagnostic.cpp
@@ -7,8 +7,8 @@
 // CHECK2-NOT: warning
 // CHECK3-NOT: warning
 
-// CHECK1: error: error reading '{{.*}}.nonexistent.cpp'
-// CHECK2: error: unknown argument: '-fan-unknown-option'
+// CHECK1: error: error reading '{{.*}}.nonexistent.cpp' [clang-diagnostic-error]
+// CHECK2: error: unknown argument: '-fan-unknown-option' [clang-diagnostic-error]
 
 // CHECK2: :[[@LINE+2]]:9: warning: implicit conversion from 'double' to 'int' changes value
 // CHECK3: :[[@LINE+1]]:9: warning: implicit conversion from 'double' to 'int' changes value