From 5da7c040030c4af72dcc21220f579098469c554e Mon Sep 17 00:00:00 2001
From: Salman Javed <mail@salmanjaved.org>
Date: Thu, 27 Jan 2022 01:02:35 +1300
Subject: [PATCH] Re-land "Cache the locations of NOLINTBEGIN/END blocks" with
 fix for build bot

---
 clang-tools-extra/clang-tidy/CMakeLists.txt   |   1 +
 .../ClangTidyDiagnosticConsumer.cpp           | 230 +---------
 .../clang-tidy/ClangTidyDiagnosticConsumer.h  |  47 +-
 .../clang-tidy/NoLintDirectiveHandler.cpp     | 415 ++++++++++++++++++
 .../clang-tidy/NoLintDirectiveHandler.h       |  51 +++
 clang-tools-extra/clangd/ParsedAST.cpp        |  12 +-
 .../nolintbeginend/1st-translation-unit.cpp   |   5 +
 .../nolintbeginend/2nd-translation-unit.cpp   |   6 +
 .../test/clang-tidy/infrastructure/nolint.cpp |  51 ++-
 .../infrastructure/nolintbeginend-LIFO.cpp    |  19 +
 .../nolintbeginend-begin-all-end-glob.cpp     |  16 +
 .../nolintbeginend-begin-all-end-specific.cpp |  16 +
 .../nolintbeginend-begin-glob-end-all.cpp     |  16 +
 ...nolintbeginend-begin-glob-end-specific.cpp |  16 +
 ...lintbeginend-begin-global-end-specific.cpp |  25 --
 ...lintbeginend-begin-multiple-end-single.cpp |  22 +
 ...lintbeginend-begin-single-end-multiple.cpp |  22 +
 .../nolintbeginend-begin-specific-end-all.cpp |  16 +
 ...nolintbeginend-begin-specific-end-glob.cpp |  16 +
 ...lintbeginend-begin-specific-end-global.cpp |  25 --
 .../nolintbeginend-mismatched-check-names.cpp |  21 -
 .../nolintbeginend-mismatched-delims.cpp      |   1 -
 .../nolintbeginend-multiple-TUs.cpp           |   6 +
 .../nolintbeginend-typo-in-check-name.cpp     |   3 +
 .../infrastructure/nolintbeginend.cpp         |  28 +-
 25 files changed, 752 insertions(+), 334 deletions(-)
 create mode 100644 clang-tools-extra/clang-tidy/NoLintDirectiveHandler.cpp
 create mode 100644 clang-tools-extra/clang-tidy/NoLintDirectiveHandler.h
 create mode 100644 clang-tools-extra/test/clang-tidy/infrastructure/Inputs/nolintbeginend/1st-translation-unit.cpp
 create mode 100644 clang-tools-extra/test/clang-tidy/infrastructure/Inputs/nolintbeginend/2nd-translation-unit.cpp
 create mode 100644 clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend-LIFO.cpp
 create mode 100644 clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend-begin-all-end-glob.cpp
 create mode 100644 clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend-begin-all-end-specific.cpp
 create mode 100644 clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend-begin-glob-end-all.cpp
 create mode 100644 clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend-begin-glob-end-specific.cpp
 delete mode 100644 clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend-begin-global-end-specific.cpp
 create mode 100644 clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend-begin-multiple-end-single.cpp
 create mode 100644 clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend-begin-single-end-multiple.cpp
 create mode 100644 clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend-begin-specific-end-all.cpp
 create mode 100644 clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend-begin-specific-end-glob.cpp
 delete mode 100644 clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend-begin-specific-end-global.cpp
 create mode 100644 clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend-multiple-TUs.cpp

diff --git a/clang-tools-extra/clang-tidy/CMakeLists.txt b/clang-tools-extra/clang-tidy/CMakeLists.txt
index 075e9f9909d6..8a953eeea275 100644
--- a/clang-tools-extra/clang-tidy/CMakeLists.txt
+++ b/clang-tools-extra/clang-tidy/CMakeLists.txt
@@ -17,6 +17,7 @@ add_clang_library(clangTidy
   ClangTidyProfiling.cpp
   ExpandModularHeadersPPCallbacks.cpp
   GlobList.cpp
+  NoLintDirectiveHandler.cpp
 
   DEPENDS
   ClangSACheckers
diff --git a/clang-tools-extra/clang-tidy/ClangTidyDiagnosticConsumer.cpp b/clang-tools-extra/clang-tidy/ClangTidyDiagnosticConsumer.cpp
index 66f60ec60b60..04721a2d3a02 100644
--- a/clang-tools-extra/clang-tidy/ClangTidyDiagnosticConsumer.cpp
+++ b/clang-tools-extra/clang-tidy/ClangTidyDiagnosticConsumer.cpp
@@ -18,6 +18,7 @@
 #include "ClangTidyDiagnosticConsumer.h"
 #include "ClangTidyOptions.h"
 #include "GlobList.h"
+#include "NoLintDirectiveHandler.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/ASTDiagnostic.h"
 #include "clang/AST/Attr.h"
@@ -188,7 +189,7 @@ DiagnosticBuilder ClangTidyContext::diag(
   return DiagEngine->Report(ID);
 }
 
-DiagnosticBuilder ClangTidyContext::diag(const ClangTidyError &Error) {
+DiagnosticBuilder ClangTidyContext::diag(const tooling::Diagnostic &Error) {
   SourceManager &SM = DiagEngine->getSourceManager();
   llvm::ErrorOr<const FileEntry *> File =
       SM.getFileManager().getFile(Error.Message.FilePath);
@@ -206,6 +207,15 @@ DiagnosticBuilder ClangTidyContext::configurationDiag(
   return diag("clang-tidy-config", Message, Level);
 }
 
+bool ClangTidyContext::shouldSuppressDiagnostic(
+    DiagnosticsEngine::Level DiagLevel, const Diagnostic &Info,
+    SmallVectorImpl<tooling::Diagnostic> &NoLintErrors, bool AllowIO,
+    bool EnableNoLintBlocks) {
+  std::string CheckName = getCheckName(Info.getID());
+  return NoLintHandler.shouldSuppress(DiagLevel, Info, CheckName, NoLintErrors,
+                                      AllowIO, EnableNoLintBlocks);
+}
+
 void ClangTidyContext::setSourceManager(SourceManager *SourceMgr) {
   DiagEngine->setSourceManager(SourceMgr);
 }
@@ -307,218 +317,9 @@ void ClangTidyDiagnosticConsumer::finalizeLastError() {
   LastErrorPassesLineFilter = false;
 }
 
-static bool isNOLINTFound(StringRef NolintDirectiveText, StringRef CheckName,
-                          StringRef Line, size_t *FoundNolintIndex = nullptr,
-                          StringRef *FoundNolintChecksStr = nullptr) {
-  if (FoundNolintIndex)
-    *FoundNolintIndex = StringRef::npos;
-  if (FoundNolintChecksStr)
-    *FoundNolintChecksStr = StringRef();
-
-  size_t NolintIndex = Line.find(NolintDirectiveText);
-  if (NolintIndex == StringRef::npos)
-    return false;
-
-  size_t BracketIndex = NolintIndex + NolintDirectiveText.size();
-  if (BracketIndex < Line.size() && isalnum(Line[BracketIndex])) {
-    // Reject this search result, otherwise it will cause false positives when
-    // NOLINT is found as a substring of NOLINT(NEXTLINE/BEGIN/END).
-    return false;
-  }
-
-  // Check if specific checks are specified in brackets.
-  if (BracketIndex < Line.size() && Line[BracketIndex] == '(') {
-    ++BracketIndex;
-    const size_t BracketEndIndex = Line.find(')', BracketIndex);
-    if (BracketEndIndex != StringRef::npos) {
-      StringRef ChecksStr =
-          Line.substr(BracketIndex, BracketEndIndex - BracketIndex);
-      if (FoundNolintChecksStr)
-        *FoundNolintChecksStr = ChecksStr;
-      // Allow specifying a few checks with a glob expression, ignoring
-      // negative globs (which would effectively disable the suppression).
-      GlobList Globs(ChecksStr, /*KeepNegativeGlobs=*/false);
-      if (!Globs.contains(CheckName))
-        return false;
-    }
-  }
-
-  if (FoundNolintIndex)
-    *FoundNolintIndex = NolintIndex;
-
-  return true;
-}
-
-static llvm::Optional<StringRef> getBuffer(const SourceManager &SM, FileID File,
-                                           bool AllowIO) {
-  return AllowIO ? SM.getBufferDataOrNone(File)
-                 : SM.getBufferDataIfLoaded(File);
-}
-
-static ClangTidyError createNolintError(const ClangTidyContext &Context,
-                                        const SourceManager &SM,
-                                        SourceLocation Loc,
-                                        bool IsNolintBegin) {
-  ClangTidyError Error("clang-tidy-nolint", ClangTidyError::Error,
-                       Context.getCurrentBuildDirectory(), false);
-  StringRef Message =
-      IsNolintBegin
-          ? ("unmatched 'NOLINTBEGIN' comment without a subsequent 'NOLINT"
-             "END' comment")
-          : ("unmatched 'NOLINTEND' comment without a previous 'NOLINT"
-             "BEGIN' comment");
-  Error.Message = tooling::DiagnosticMessage(Message, SM, Loc);
-  return Error;
-}
-
-static Optional<ClangTidyError> tallyNolintBegins(
-    const ClangTidyContext &Context, const SourceManager &SM,
-    StringRef CheckName, SmallVector<StringRef> Lines, SourceLocation LinesLoc,
-    SmallVector<std::pair<SourceLocation, StringRef>> &NolintBegins) {
-  // Keep a running total of how many NOLINT(BEGIN...END) blocks are active, as
-  // well as the bracket expression (if any) that was used in the NOLINT
-  // expression.
-  size_t NolintIndex;
-  StringRef NolintChecksStr;
-  for (const auto &Line : Lines) {
-    if (isNOLINTFound("NOLINTBEGIN", CheckName, Line, &NolintIndex,
-                      &NolintChecksStr)) {
-      // Check if a new block is being started.
-      NolintBegins.emplace_back(std::make_pair(
-          LinesLoc.getLocWithOffset(NolintIndex), NolintChecksStr));
-    } else if (isNOLINTFound("NOLINTEND", CheckName, Line, &NolintIndex,
-                             &NolintChecksStr)) {
-      // Check if the previous block is being closed.
-      if (!NolintBegins.empty() &&
-          NolintBegins.back().second == NolintChecksStr) {
-        NolintBegins.pop_back();
-      } else {
-        // Trying to close a nonexistent block. Return a diagnostic about this
-        // misuse that can be displayed along with the original clang-tidy check
-        // that the user was attempting to suppress.
-        return createNolintError(Context, SM,
-                                 LinesLoc.getLocWithOffset(NolintIndex), false);
-      }
-    }
-    // Advance source location to the next line.
-    LinesLoc = LinesLoc.getLocWithOffset(Line.size() + sizeof('\n'));
-  }
-  return None; // All NOLINT(BEGIN/END) use has been consistent so far.
-}
-
-static bool
-lineIsWithinNolintBegin(const ClangTidyContext &Context,
-                        SmallVectorImpl<ClangTidyError> &SuppressionErrors,
-                        const SourceManager &SM, SourceLocation Loc,
-                        StringRef CheckName, StringRef TextBeforeDiag,
-                        StringRef TextAfterDiag) {
-  Loc = SM.getExpansionRange(Loc).getBegin();
-  SourceLocation FileStartLoc = SM.getLocForStartOfFile(SM.getFileID(Loc));
-  SmallVector<std::pair<SourceLocation, StringRef>> NolintBegins;
-
-  // Check if there's an open NOLINT(BEGIN...END) block on the previous lines.
-  SmallVector<StringRef> PrevLines;
-  TextBeforeDiag.split(PrevLines, '\n');
-  auto Error = tallyNolintBegins(Context, SM, CheckName, PrevLines,
-                                 FileStartLoc, NolintBegins);
-  if (Error) {
-    SuppressionErrors.emplace_back(Error.getValue());
-  }
-  bool WithinNolintBegin = !NolintBegins.empty();
-
-  // Check that every block is terminated correctly on the following lines.
-  SmallVector<StringRef> FollowingLines;
-  TextAfterDiag.split(FollowingLines, '\n');
-  Error = tallyNolintBegins(Context, SM, CheckName, FollowingLines, Loc,
-                            NolintBegins);
-  if (Error) {
-    SuppressionErrors.emplace_back(Error.getValue());
-  }
-
-  // The following blocks were never closed. Return diagnostics for each
-  // instance that can be displayed along with the original clang-tidy check
-  // that the user was attempting to suppress.
-  for (const auto &NolintBegin : NolintBegins) {
-    SuppressionErrors.emplace_back(
-        createNolintError(Context, SM, NolintBegin.first, true));
-  }
-
-  return WithinNolintBegin && SuppressionErrors.empty();
-}
-
-static bool
-lineIsMarkedWithNOLINT(const ClangTidyContext &Context,
-                       SmallVectorImpl<ClangTidyError> &SuppressionErrors,
-                       bool AllowIO, const SourceManager &SM,
-                       SourceLocation Loc, StringRef CheckName,
-                       bool EnableNolintBlocks) {
-  // Get source code for this location.
-  FileID File;
-  unsigned Offset;
-  std::tie(File, Offset) = SM.getDecomposedSpellingLoc(Loc);
-  Optional<StringRef> Buffer = getBuffer(SM, File, AllowIO);
-  if (!Buffer)
-    return false;
-
-  // Check if there's a NOLINT on this line.
-  StringRef TextAfterDiag = Buffer->substr(Offset);
-  StringRef RestOfThisLine, FollowingLines;
-  std::tie(RestOfThisLine, FollowingLines) = TextAfterDiag.split('\n');
-  if (isNOLINTFound("NOLINT", CheckName, RestOfThisLine))
-    return true;
-
-  // Check if there's a NOLINTNEXTLINE on the previous line.
-  StringRef TextBeforeDiag = Buffer->substr(0, Offset);
-  size_t LastNewLinePos = TextBeforeDiag.rfind('\n');
-  StringRef PrevLines = (LastNewLinePos == StringRef::npos)
-                            ? StringRef()
-                            : TextBeforeDiag.slice(0, LastNewLinePos);
-  LastNewLinePos = PrevLines.rfind('\n');
-  StringRef PrevLine = (LastNewLinePos == StringRef::npos)
-                           ? PrevLines
-                           : PrevLines.substr(LastNewLinePos + 1);
-  if (isNOLINTFound("NOLINTNEXTLINE", CheckName, PrevLine))
-    return true;
-
-  // Check if this line is within a NOLINT(BEGIN...END) block.
-  return EnableNolintBlocks &&
-         lineIsWithinNolintBegin(Context, SuppressionErrors, SM, Loc, CheckName,
-                                 TextBeforeDiag, TextAfterDiag);
-}
-
-static bool lineIsMarkedWithNOLINTinMacro(
-    const Diagnostic &Info, const ClangTidyContext &Context,
-    SmallVectorImpl<ClangTidyError> &SuppressionErrors, bool AllowIO,
-    bool EnableNolintBlocks) {
-  const SourceManager &SM = Info.getSourceManager();
-  SourceLocation Loc = Info.getLocation();
-  std::string CheckName = Context.getCheckName(Info.getID());
-  while (true) {
-    if (lineIsMarkedWithNOLINT(Context, SuppressionErrors, AllowIO, SM, Loc,
-                               CheckName, EnableNolintBlocks))
-      return true;
-    if (!Loc.isMacroID())
-      return false;
-    Loc = SM.getImmediateExpansionRange(Loc).getBegin();
-  }
-  return false;
-}
-
 namespace clang {
 namespace tidy {
 
-bool shouldSuppressDiagnostic(
-    DiagnosticsEngine::Level DiagLevel, const Diagnostic &Info,
-    ClangTidyContext &Context,
-    SmallVectorImpl<ClangTidyError> &SuppressionErrors, bool AllowIO,
-    bool EnableNolintBlocks) {
-  return Info.getLocation().isValid() &&
-         DiagLevel != DiagnosticsEngine::Error &&
-         DiagLevel != DiagnosticsEngine::Fatal &&
-         lineIsMarkedWithNOLINTinMacro(Info, Context, SuppressionErrors,
-                                       AllowIO, EnableNolintBlocks);
-}
-
 const llvm::StringMap<tooling::Replacements> *
 getFixIt(const tooling::Diagnostic &Diagnostic, bool GetFixFromNotes) {
   if (!Diagnostic.Message.Fix.empty())
@@ -545,12 +346,15 @@ void ClangTidyDiagnosticConsumer::HandleDiagnostic(
   if (LastErrorWasIgnored && DiagLevel == DiagnosticsEngine::Note)
     return;
 
-  SmallVector<ClangTidyError, 1> SuppressionErrors;
-  if (shouldSuppressDiagnostic(DiagLevel, Info, Context, SuppressionErrors,
-                               EnableNolintBlocks)) {
+  SmallVector<tooling::Diagnostic, 1> SuppressionErrors;
+  if (Context.shouldSuppressDiagnostic(DiagLevel, Info, SuppressionErrors,
+                                       EnableNolintBlocks)) {
     ++Context.Stats.ErrorsIgnoredNOLINT;
     // Ignored a warning, should ignore related notes as well
     LastErrorWasIgnored = true;
+    Context.DiagEngine->Clear();
+    for (const auto &Error : SuppressionErrors)
+      Context.diag(Error);
     return;
   }
 
diff --git a/clang-tools-extra/clang-tidy/ClangTidyDiagnosticConsumer.h b/clang-tools-extra/clang-tidy/ClangTidyDiagnosticConsumer.h
index 69f1ceddd9bd..e41003262ccc 100644
--- a/clang-tools-extra/clang-tidy/ClangTidyDiagnosticConsumer.h
+++ b/clang-tools-extra/clang-tidy/ClangTidyDiagnosticConsumer.h
@@ -11,6 +11,7 @@
 
 #include "ClangTidyOptions.h"
 #include "ClangTidyProfiling.h"
+#include "NoLintDirectiveHandler.h"
 #include "clang/Basic/Diagnostic.h"
 #include "clang/Tooling/Core/Diagnostic.h"
 #include "llvm/ADT/DenseMap.h"
@@ -95,13 +96,33 @@ public:
   DiagnosticBuilder diag(StringRef CheckName, StringRef Message,
                          DiagnosticIDs::Level Level = DiagnosticIDs::Warning);
 
-  DiagnosticBuilder diag(const ClangTidyError &Error);
+  DiagnosticBuilder diag(const tooling::Diagnostic &Error);
 
   /// Report any errors to do with reading the configuration using this method.
   DiagnosticBuilder
   configurationDiag(StringRef Message,
                     DiagnosticIDs::Level Level = DiagnosticIDs::Warning);
 
+  /// Check whether a given diagnostic should be suppressed due to the presence
+  /// of a "NOLINT" suppression comment.
+  /// This is exposed so that other tools that present clang-tidy diagnostics
+  /// (such as clangd) can respect the same suppression rules as clang-tidy.
+  /// This does not handle suppression of notes following a suppressed
+  /// diagnostic; that is left to the caller as it requires maintaining state in
+  /// between calls to this function.
+  /// If any NOLINT is malformed, e.g. a BEGIN without a subsequent END, an
+  /// error about it will be returned in output \param NoLintErrors.
+  /// If \param AllowIO is false, the function does not attempt to read source
+  /// files from disk which are not already mapped into memory; such files are
+  /// treated as not containing a suppression comment.
+  /// \param EnableNoLintBlocks controls whether to honor NOLINTBEGIN/NOLINTEND
+  /// blocks; if false, only considers line-level disabling.
+  bool
+  shouldSuppressDiagnostic(DiagnosticsEngine::Level DiagLevel,
+                           const Diagnostic &Info,
+                           SmallVectorImpl<tooling::Diagnostic> &NoLintErrors,
+                           bool AllowIO = true, bool EnableNoLintBlocks = true);
+
   /// Sets the \c SourceManager of the used \c DiagnosticsEngine.
   ///
   /// This is called from the \c ClangTidyCheck base class.
@@ -208,29 +229,9 @@ private:
   std::string ProfilePrefix;
 
   bool AllowEnablingAnalyzerAlphaCheckers;
-};
 
-/// Check whether a given diagnostic should be suppressed due to the presence
-/// of a "NOLINT" suppression comment.
-/// This is exposed so that other tools that present clang-tidy diagnostics
-/// (such as clangd) can respect the same suppression rules as clang-tidy.
-/// This does not handle suppression of notes following a suppressed diagnostic;
-/// that is left to the caller as it requires maintaining state in between calls
-/// to this function.
-/// If `AllowIO` is false, the function does not attempt to read source files
-/// from disk which are not already mapped into memory; such files are treated
-/// as not containing a suppression comment.
-/// \param EnableNolintBlocks controls whether to honor NOLINTBEGIN/NOLINTEND
-/// blocks; if false, only considers line-level disabling.
-/// If suppression is not possible due to improper use of "NOLINT" comments -
-/// for example, the use of a "NOLINTBEGIN" comment that is not followed by a
-/// "NOLINTEND" comment - a diagnostic regarding the improper use is returned
-/// via the output argument `SuppressionErrors`.
-bool shouldSuppressDiagnostic(
-    DiagnosticsEngine::Level DiagLevel, const Diagnostic &Info,
-    ClangTidyContext &Context,
-    SmallVectorImpl<ClangTidyError> &SuppressionErrors, bool AllowIO = true,
-    bool EnableNolintBlocks = true);
+  NoLintDirectiveHandler NoLintHandler;
+};
 
 /// Gets the Fix attached to \p Diagnostic.
 /// If there isn't a Fix attached to the diagnostic and \p AnyFix is true, Check
diff --git a/clang-tools-extra/clang-tidy/NoLintDirectiveHandler.cpp b/clang-tools-extra/clang-tidy/NoLintDirectiveHandler.cpp
new file mode 100644
index 000000000000..667ffdb5fab6
--- /dev/null
+++ b/clang-tools-extra/clang-tidy/NoLintDirectiveHandler.cpp
@@ -0,0 +1,415 @@
+//===-- clang-tools-extra/clang-tidy/NoLintDirectiveHandler.cpp -----------===//
+//
+// 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 This file implements the NoLintDirectiveHandler class, which is used
+///  to locate NOLINT comments in the file being analyzed, to decide whether a
+///  diagnostic should be suppressed.
+///
+//===----------------------------------------------------------------------===//
+
+#include "NoLintDirectiveHandler.h"
+#include "GlobList.h"
+#include "clang/Basic/LLVM.h"
+#include "clang/Basic/SourceLocation.h"
+#include "clang/Basic/SourceManager.h"
+#include "clang/Tooling/Core/Diagnostic.h"
+#include "llvm/ADT/ArrayRef.h"
+#include "llvm/ADT/None.h"
+#include "llvm/ADT/Optional.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/StringExtras.h"
+#include "llvm/ADT/StringMap.h"
+#include "llvm/ADT/StringSwitch.h"
+#include <cassert>
+#include <cstddef>
+#include <iterator>
+#include <string>
+#include <tuple>
+#include <type_traits>
+#include <utility>
+
+namespace clang {
+namespace tidy {
+
+//===----------------------------------------------------------------------===//
+// NoLintType
+//===----------------------------------------------------------------------===//
+
+// The type - one of NOLINT[NEXTLINE/BEGIN/END].
+enum class NoLintType { NoLint, NoLintNextLine, NoLintBegin, NoLintEnd };
+
+// Convert a string like "NOLINTNEXTLINE" to its enum `Type::NoLintNextLine`.
+// Return `None` if the string is unrecognized.
+static Optional<NoLintType> strToNoLintType(StringRef Str) {
+  auto Type = llvm::StringSwitch<Optional<NoLintType>>(Str)
+                  .Case("NOLINT", NoLintType::NoLint)
+                  .Case("NOLINTNEXTLINE", NoLintType::NoLintNextLine)
+                  .Case("NOLINTBEGIN", NoLintType::NoLintBegin)
+                  .Case("NOLINTEND", NoLintType::NoLintEnd)
+                  .Default(None);
+  return Type;
+}
+
+//===----------------------------------------------------------------------===//
+// NoLintToken
+//===----------------------------------------------------------------------===//
+
+// Whitespace within a NOLINT's check list shall be ignored.
+// "NOLINT( check1, check2 )" is equivalent to "NOLINT(check1,check2)".
+// Return the check list with all extraneous whitespace removed.
+static std::string trimWhitespace(StringRef Checks) {
+  SmallVector<StringRef> Split;
+  Checks.split(Split, ',');
+  for (StringRef &Check : Split)
+    Check = Check.trim();
+  return llvm::join(Split, ",");
+}
+
+namespace {
+
+// Record the presence of a NOLINT comment - its type, location, checks -
+// as parsed from the file's character contents.
+class NoLintToken {
+public:
+  // \param Checks:
+  // - If unspecified (i.e. `None`) then ALL checks are suppressed - equivalent
+  //   to NOLINT(*).
+  // - An empty string means nothing is suppressed - equivalent to NOLINT().
+  // - Negative globs ignored (which would effectively disable the suppression).
+  NoLintToken(NoLintType Type, size_t Pos, const Optional<std::string> &Checks)
+      : Type(Type), Pos(Pos), ChecksGlob(std::make_unique<CachedGlobList>(
+                                  Checks.getValueOr("*"),
+                                  /*KeepNegativeGlobs=*/false)) {
+    if (Checks)
+      this->Checks = trimWhitespace(*Checks);
+  }
+
+  // The type - one of NOLINT[NEXTLINE/BEGIN/END].
+  NoLintType Type;
+
+  // The location of the first character, "N", in "NOLINT".
+  size_t Pos;
+
+  // If this NOLINT specifies checks, return the checks.
+  Optional<std::string> checks() const { return Checks; }
+
+  // Whether this NOLINT applies to the provided check.
+  bool suppresses(StringRef Check) const { return ChecksGlob->contains(Check); }
+
+private:
+  Optional<std::string> Checks;
+  std::unique_ptr<CachedGlobList> ChecksGlob;
+};
+
+} // namespace
+
+// Consume the entire buffer and return all `NoLintToken`s that were found.
+static SmallVector<NoLintToken> getNoLints(StringRef Buffer) {
+  static constexpr llvm::StringLiteral NOLINT = "NOLINT";
+  SmallVector<NoLintToken> NoLints;
+
+  size_t Pos = 0;
+  while (Pos < Buffer.size()) {
+    // Find NOLINT:
+    const size_t NoLintPos = Buffer.find(NOLINT, Pos);
+    if (NoLintPos == StringRef::npos)
+      break; // Buffer exhausted
+
+    // Read [A-Z] characters immediately after "NOLINT", e.g. the "NEXTLINE" in
+    // "NOLINTNEXTLINE".
+    Pos = NoLintPos + NOLINT.size();
+    while (Pos < Buffer.size() && llvm::isAlpha(Buffer[Pos]))
+      ++Pos;
+
+    // Is this a recognized NOLINT type?
+    const Optional<NoLintType> NoLintType =
+        strToNoLintType(Buffer.slice(NoLintPos, Pos));
+    if (!NoLintType)
+      continue;
+
+    // Get checks, if specified.
+    Optional<std::string> Checks;
+    if (Pos < Buffer.size() && Buffer[Pos] == '(') {
+      size_t ClosingBracket = Buffer.find_first_of("\n)", ++Pos);
+      if (ClosingBracket != StringRef::npos && Buffer[ClosingBracket] == ')') {
+        Checks = Buffer.slice(Pos, ClosingBracket).str();
+        Pos = ClosingBracket + 1;
+      }
+    }
+
+    NoLints.emplace_back(*NoLintType, NoLintPos, Checks);
+  }
+
+  return NoLints;
+}
+
+//===----------------------------------------------------------------------===//
+// NoLintBlockToken
+//===----------------------------------------------------------------------===//
+
+namespace {
+
+// Represents a source range within a pair of NOLINT(BEGIN/END) comments.
+class NoLintBlockToken {
+public:
+  NoLintBlockToken(NoLintToken Begin, const NoLintToken &End)
+      : Begin(std::move(Begin)), EndPos(End.Pos) {
+    assert(this->Begin.Type == NoLintType::NoLintBegin);
+    assert(End.Type == NoLintType::NoLintEnd);
+    assert(this->Begin.Pos < End.Pos);
+    assert(this->Begin.checks() == End.checks());
+  }
+
+  // Whether the provided diagnostic is within and is suppressible by this block
+  // of NOLINT(BEGIN/END) comments.
+  bool suppresses(size_t DiagPos, StringRef DiagName) const {
+    return (Begin.Pos < DiagPos) && (DiagPos < EndPos) &&
+           Begin.suppresses(DiagName);
+  }
+
+private:
+  NoLintToken Begin;
+  size_t EndPos;
+};
+
+} // namespace
+
+// Match NOLINTBEGINs with their corresponding NOLINTENDs and move them into
+// `NoLintBlockToken`s. If any BEGINs or ENDs are left over, they are moved to
+// `UnmatchedTokens`.
+static SmallVector<NoLintBlockToken>
+formNoLintBlocks(SmallVector<NoLintToken> NoLints,
+                 SmallVectorImpl<NoLintToken> &UnmatchedTokens) {
+  SmallVector<NoLintBlockToken> CompletedBlocks;
+  SmallVector<NoLintToken> Stack;
+
+  // Nested blocks must be fully contained within their parent block. What this
+  // means is that when you have a series of nested BEGIN tokens, the END tokens
+  // shall appear in the reverse order, starting with the closing of the
+  // inner-most block first, then the next level up, and so on. This is
+  // essentially a last-in-first-out/stack system.
+  for (NoLintToken &NoLint : NoLints) {
+    if (NoLint.Type == NoLintType::NoLintBegin)
+      // A new block is being started. Add it to the stack.
+      Stack.emplace_back(std::move(NoLint));
+    else if (NoLint.Type == NoLintType::NoLintEnd) {
+      if (!Stack.empty() && Stack.back().checks() == NoLint.checks())
+        // The previous block is being closed. Pop one element off the stack.
+        CompletedBlocks.emplace_back(Stack.pop_back_val(), NoLint);
+      else
+        // Trying to close the wrong block.
+        UnmatchedTokens.emplace_back(std::move(NoLint));
+    }
+  }
+
+  llvm::move(Stack, std::back_inserter(UnmatchedTokens));
+  return CompletedBlocks;
+}
+
+//===----------------------------------------------------------------------===//
+// NoLintDirectiveHandler::Impl
+//===----------------------------------------------------------------------===//
+
+class NoLintDirectiveHandler::Impl {
+public:
+  bool shouldSuppress(DiagnosticsEngine::Level DiagLevel,
+                      const Diagnostic &Diag, StringRef DiagName,
+                      SmallVectorImpl<tooling::Diagnostic> &NoLintErrors,
+                      bool AllowIO, bool EnableNoLintBlocks);
+
+private:
+  bool diagHasNoLintInMacro(const Diagnostic &Diag, StringRef DiagName,
+                            SmallVectorImpl<tooling::Diagnostic> &NoLintErrors,
+                            bool AllowIO, bool EnableNoLintBlocks);
+
+  bool diagHasNoLint(StringRef DiagName, SourceLocation DiagLoc,
+                     const SourceManager &SrcMgr,
+                     SmallVectorImpl<tooling::Diagnostic> &NoLintErrors,
+                     bool AllowIO, bool EnableNoLintBlocks);
+
+  void generateCache(const SourceManager &SrcMgr, StringRef FileName,
+                     FileID File, StringRef Buffer,
+                     SmallVectorImpl<tooling::Diagnostic> &NoLintErrors);
+
+  llvm::StringMap<SmallVector<NoLintBlockToken>> Cache;
+};
+
+bool NoLintDirectiveHandler::Impl::shouldSuppress(
+    DiagnosticsEngine::Level DiagLevel, const Diagnostic &Diag,
+    StringRef DiagName, SmallVectorImpl<tooling::Diagnostic> &NoLintErrors,
+    bool AllowIO, bool EnableNoLintBlocks) {
+  if (DiagLevel >= DiagnosticsEngine::Error)
+    return false;
+  return diagHasNoLintInMacro(Diag, DiagName, NoLintErrors, AllowIO,
+                              EnableNoLintBlocks);
+}
+
+// Look at the macro's spelling location for a NOLINT. If none is found, keep
+// looking up the call stack.
+bool NoLintDirectiveHandler::Impl::diagHasNoLintInMacro(
+    const Diagnostic &Diag, StringRef DiagName,
+    SmallVectorImpl<tooling::Diagnostic> &NoLintErrors, bool AllowIO,
+    bool EnableNoLintBlocks) {
+  SourceLocation DiagLoc = Diag.getLocation();
+  if (DiagLoc.isInvalid())
+    return false;
+  const SourceManager &SrcMgr = Diag.getSourceManager();
+  while (true) {
+    if (diagHasNoLint(DiagName, DiagLoc, SrcMgr, NoLintErrors, AllowIO,
+                      EnableNoLintBlocks))
+      return true;
+    if (!DiagLoc.isMacroID())
+      return false;
+    DiagLoc = SrcMgr.getImmediateMacroCallerLoc(DiagLoc);
+  }
+  return false;
+}
+
+// Look behind and ahead for '\n' characters. These mark the start and end of
+// this line.
+static std::pair<size_t, size_t> getLineStartAndEnd(StringRef Buffer,
+                                                    size_t From) {
+  size_t StartPos = Buffer.find_last_of('\n', From) + 1;
+  size_t EndPos = std::min(Buffer.find('\n', From), Buffer.size());
+  return std::make_pair(StartPos, EndPos);
+}
+
+// Whether the line has a NOLINT of type = `Type` that can suppress the
+// diagnostic `DiagName`.
+static bool lineHasNoLint(StringRef Buffer,
+                          std::pair<size_t, size_t> LineStartAndEnd,
+                          NoLintType Type, StringRef DiagName) {
+  // Get all NOLINTs on the line.
+  Buffer = Buffer.slice(LineStartAndEnd.first, LineStartAndEnd.second);
+  SmallVector<NoLintToken> NoLints = getNoLints(Buffer);
+
+  // Do any of these NOLINTs match the desired type and diag name?
+  return llvm::any_of(NoLints, [&](const NoLintToken &NoLint) {
+    return NoLint.Type == Type && NoLint.suppresses(DiagName);
+  });
+}
+
+// Whether the provided diagnostic is located within and is suppressible by a
+// block of NOLINT(BEGIN/END) comments.
+static bool withinNoLintBlock(ArrayRef<NoLintBlockToken> NoLintBlocks,
+                              size_t DiagPos, StringRef DiagName) {
+  return llvm::any_of(NoLintBlocks, [&](const NoLintBlockToken &NoLintBlock) {
+    return NoLintBlock.suppresses(DiagPos, DiagName);
+  });
+}
+
+// Get the file contents as a string.
+static Optional<StringRef> getBuffer(const SourceManager &SrcMgr, FileID File,
+                                     bool AllowIO) {
+  return AllowIO ? SrcMgr.getBufferDataOrNone(File)
+                 : SrcMgr.getBufferDataIfLoaded(File);
+}
+
+// We will check for NOLINTs and NOLINTNEXTLINEs first. Checking for these is
+// not so expensive (just need to parse the current and previous lines). Only if
+// that fails do we look for NOLINT(BEGIN/END) blocks (which requires reading
+// the entire file).
+bool NoLintDirectiveHandler::Impl::diagHasNoLint(
+    StringRef DiagName, SourceLocation DiagLoc, const SourceManager &SrcMgr,
+    SmallVectorImpl<tooling::Diagnostic> &NoLintErrors, bool AllowIO,
+    bool EnableNoLintBlocks) {
+  // Translate the diagnostic's SourceLocation to a raw file + offset pair.
+  FileID File;
+  unsigned int Pos = 0;
+  std::tie(File, Pos) = SrcMgr.getDecomposedSpellingLoc(DiagLoc);
+
+  // We will only see NOLINTs in user-authored sources. No point reading the
+  // file if it is a <built-in>.
+  Optional<StringRef> FileName = SrcMgr.getNonBuiltinFilenameForID(File);
+  if (!FileName)
+    return false;
+
+  // Get file contents.
+  Optional<StringRef> Buffer = getBuffer(SrcMgr, File, AllowIO);
+  if (!Buffer)
+    return false;
+
+  // Check if there's a NOLINT on this line.
+  auto ThisLine = getLineStartAndEnd(*Buffer, Pos);
+  if (lineHasNoLint(*Buffer, ThisLine, NoLintType::NoLint, DiagName))
+    return true;
+
+  // Check if there's a NOLINTNEXTLINE on the previous line.
+  if (ThisLine.first > 0) {
+    auto PrevLine = getLineStartAndEnd(*Buffer, ThisLine.first - 1);
+    if (lineHasNoLint(*Buffer, PrevLine, NoLintType::NoLintNextLine, DiagName))
+      return true;
+  }
+
+  // Check if this line is within a NOLINT(BEGIN/END) block.
+  if (!EnableNoLintBlocks)
+    return false;
+
+  // Do we have cached NOLINT block locations for this file?
+  if (Cache.count(*FileName) == 0)
+    // Warning: heavy operation - need to read entire file.
+    generateCache(SrcMgr, *FileName, File, *Buffer, NoLintErrors);
+
+  return withinNoLintBlock(Cache[*FileName], Pos, DiagName);
+}
+
+// Construct a [clang-tidy-nolint] diagnostic to do with the unmatched
+// NOLINT(BEGIN/END) pair.
+static tooling::Diagnostic makeNoLintError(const SourceManager &SrcMgr,
+                                           FileID File,
+                                           const NoLintToken &NoLint) {
+  tooling::Diagnostic Error;
+  Error.DiagLevel = tooling::Diagnostic::Error;
+  Error.DiagnosticName = "clang-tidy-nolint";
+  StringRef Message =
+      (NoLint.Type == NoLintType::NoLintBegin)
+          ? ("unmatched 'NOLINTBEGIN' comment without a subsequent 'NOLINT"
+             "END' comment")
+          : ("unmatched 'NOLINTEND' comment without a previous 'NOLINT"
+             "BEGIN' comment");
+  SourceLocation Loc = SrcMgr.getComposedLoc(File, NoLint.Pos);
+  Error.Message = tooling::DiagnosticMessage(Message, SrcMgr, Loc);
+  return Error;
+}
+
+// Find all NOLINT(BEGIN/END) blocks in a file and store in the cache.
+void NoLintDirectiveHandler::Impl::generateCache(
+    const SourceManager &SrcMgr, StringRef FileName, FileID File,
+    StringRef Buffer, SmallVectorImpl<tooling::Diagnostic> &NoLintErrors) {
+  // Read entire file to get all NOLINTs.
+  SmallVector<NoLintToken> NoLints = getNoLints(Buffer);
+
+  // Match each BEGIN with its corresponding END.
+  SmallVector<NoLintToken> UnmatchedTokens;
+  Cache[FileName] = formNoLintBlocks(std::move(NoLints), UnmatchedTokens);
+
+  // Raise error for any BEGIN/END left over.
+  for (const NoLintToken &NoLint : UnmatchedTokens)
+    NoLintErrors.emplace_back(makeNoLintError(SrcMgr, File, NoLint));
+}
+
+//===----------------------------------------------------------------------===//
+// NoLintDirectiveHandler
+//===----------------------------------------------------------------------===//
+
+NoLintDirectiveHandler::NoLintDirectiveHandler()
+    : PImpl(std::make_unique<Impl>()) {}
+
+NoLintDirectiveHandler::~NoLintDirectiveHandler() = default;
+
+bool NoLintDirectiveHandler::shouldSuppress(
+    DiagnosticsEngine::Level DiagLevel, const Diagnostic &Diag,
+    StringRef DiagName, SmallVectorImpl<tooling::Diagnostic> &NoLintErrors,
+    bool AllowIO, bool EnableNoLintBlocks) {
+  return PImpl->shouldSuppress(DiagLevel, Diag, DiagName, NoLintErrors, AllowIO,
+                               EnableNoLintBlocks);
+}
+
+} // namespace tidy
+} // namespace clang
diff --git a/clang-tools-extra/clang-tidy/NoLintDirectiveHandler.h b/clang-tools-extra/clang-tidy/NoLintDirectiveHandler.h
new file mode 100644
index 000000000000..db9fd593283c
--- /dev/null
+++ b/clang-tools-extra/clang-tidy/NoLintDirectiveHandler.h
@@ -0,0 +1,51 @@
+//===-- clang-tools-extra/clang-tidy/NoLintDirectiveHandler.h ----*- 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_NOLINTDIRECTIVEHANDLER_H
+#define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_NOLINTDIRECTIVEHANDLER_H
+
+#include "clang/Basic/Diagnostic.h"
+#include "llvm/ADT/StringRef.h"
+#include <memory>
+
+namespace clang {
+namespace tooling {
+struct Diagnostic;
+} // namespace tooling
+} // namespace clang
+
+namespace llvm {
+template <typename T> class SmallVectorImpl;
+} // namespace llvm
+
+namespace clang {
+namespace tidy {
+
+/// This class is used to locate NOLINT comments in the file being analyzed, to
+/// decide whether a diagnostic should be suppressed.
+/// This class keeps a cache of every NOLINT comment found so that files do not
+/// have to be repeatedly parsed each time a new diagnostic is raised.
+class NoLintDirectiveHandler {
+public:
+  NoLintDirectiveHandler();
+  ~NoLintDirectiveHandler();
+
+  bool shouldSuppress(DiagnosticsEngine::Level DiagLevel,
+                      const Diagnostic &Diag, llvm::StringRef DiagName,
+                      llvm::SmallVectorImpl<tooling::Diagnostic> &NoLintErrors,
+                      bool AllowIO, bool EnableNoLintBlocks);
+
+private:
+  class Impl;
+  std::unique_ptr<Impl> PImpl;
+};
+
+} // namespace tidy
+} // namespace clang
+
+#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_NOLINTDIRECTIVEHANDLER_H
diff --git a/clang-tools-extra/clangd/ParsedAST.cpp b/clang-tools-extra/clangd/ParsedAST.cpp
index 9c64c645130b..86c4b2151243 100644
--- a/clang-tools-extra/clangd/ParsedAST.cpp
+++ b/clang-tools-extra/clangd/ParsedAST.cpp
@@ -10,6 +10,7 @@
 #include "../clang-tidy/ClangTidyCheck.h"
 #include "../clang-tidy/ClangTidyDiagnosticConsumer.h"
 #include "../clang-tidy/ClangTidyModuleRegistry.h"
+#include "../clang-tidy/NoLintDirectiveHandler.h"
 #include "AST.h"
 #include "Compiler.h"
 #include "Config.h"
@@ -468,12 +469,11 @@ ParsedAST::build(llvm::StringRef Filename, const ParseInputs &Inputs,
           bool IsInsideMainFile =
               Info.hasSourceManager() &&
               isInsideMainFile(Info.getLocation(), Info.getSourceManager());
-          SmallVector<tidy::ClangTidyError, 1> TidySuppressedErrors;
-          if (IsInsideMainFile &&
-              tidy::shouldSuppressDiagnostic(DiagLevel, Info, *CTContext,
-                                             TidySuppressedErrors,
-                                             /*AllowIO=*/false,
-                                             /*EnableNolintBlocks=*/false)) {
+          SmallVector<tooling::Diagnostic, 1> TidySuppressedErrors;
+          if (IsInsideMainFile && CTContext->shouldSuppressDiagnostic(
+                                      DiagLevel, Info, TidySuppressedErrors,
+                                      /*AllowIO=*/false,
+                                      /*EnableNolintBlocks=*/false)) {
             // FIXME: should we expose the suppression error (invalid use of
             // NOLINT comments)?
             return DiagnosticsEngine::Ignored;
diff --git a/clang-tools-extra/test/clang-tidy/infrastructure/Inputs/nolintbeginend/1st-translation-unit.cpp b/clang-tools-extra/test/clang-tidy/infrastructure/Inputs/nolintbeginend/1st-translation-unit.cpp
new file mode 100644
index 000000000000..d90fc069c978
--- /dev/null
+++ b/clang-tools-extra/test/clang-tidy/infrastructure/Inputs/nolintbeginend/1st-translation-unit.cpp
@@ -0,0 +1,5 @@
+// NOLINTBEGIN
+class A { A(int i); };
+// NOLINTEND
+
+class B { B(int i); };
diff --git a/clang-tools-extra/test/clang-tidy/infrastructure/Inputs/nolintbeginend/2nd-translation-unit.cpp b/clang-tools-extra/test/clang-tidy/infrastructure/Inputs/nolintbeginend/2nd-translation-unit.cpp
new file mode 100644
index 000000000000..0497037d31b8
--- /dev/null
+++ b/clang-tools-extra/test/clang-tidy/infrastructure/Inputs/nolintbeginend/2nd-translation-unit.cpp
@@ -0,0 +1,6 @@
+
+class A { A(int i); };
+
+// NOLINTBEGIN
+class B { B(int i); };
+// NOLINTEND
diff --git a/clang-tools-extra/test/clang-tidy/infrastructure/nolint.cpp b/clang-tools-extra/test/clang-tidy/infrastructure/nolint.cpp
index 4b80bbe4eb3c..9ef194232b6b 100644
--- a/clang-tools-extra/test/clang-tidy/infrastructure/nolint.cpp
+++ b/clang-tools-extra/test/clang-tidy/infrastructure/nolint.cpp
@@ -28,11 +28,56 @@ class C4 { C4(int i); }; // NOLINT(google-explicit-constructor)
 
 class C5 { C5(int i); }; // NOLINT(some-check, google-explicit-constructor)
 
-class C6 { C6(int i); }; // NOLINT without-brackets-skip-all, another-check
+class C6 { C6(int i); }; // NOLINT without-brackets-skip-all
 
-class C7 { C7(int i); }; // NOLINTNEXTLINE doesn't get misconstrued as a NOLINT
+// Other NOLINT* types (e.g. NEXTLINE) should not be misconstrued as a NOLINT:
+class C7 { C7(int i); }; // NOLINTNEXTLINE
 // CHECK-MESSAGES: :[[@LINE-1]]:12: warning: single-argument constructors must be marked explicit
 
+// NOLINT must be UPPERCASE:
+// NOLINTnextline
+class C8 { C8(int i); }; // nolint
+// CHECK-MESSAGES: :[[@LINE-1]]:12: warning: single-argument constructors must be marked explicit
+
+// Unrecognized marker:
+// NOLINTNEXTLINEXYZ
+class C9 { C9(int i); }; // NOLINTXYZ
+// CHECK-MESSAGES: :[[@LINE-1]]:12: warning: single-argument constructors must be marked explicit
+
+// C-style comments are supported:
+class C10 { C10(int i); }; /* NOLINT */
+/* NOLINT */ class C11 { C11(int i); };
+
+// Multiple NOLINTs in the same comment:
+class C12 { C12(int i); }; // NOLINT(some-other-check) NOLINT(google-explicit-constructor)
+class C13 { C13(int i); }; // NOLINT(google-explicit-constructor) NOLINT(some-other-check)
+class C14 { C14(int i); }; // NOLINTNEXTLINE(some-other-check) NOLINT(google-explicit-constructor)
+
+// NOLINTNEXTLINE(google-explicit-constructor) NOLINT(some-other-check)
+class C15 { C15(int i); }; 
+
+// Any text after a NOLINT expression is treated as a comment:
+class C16 { C16(int i); }; // NOLINT: suppress check because <reason>
+class C17 { C17(int i); }; // NOLINT(google-explicit-constructor): suppress check because <reason>
+
+// NOLINT must appear in its entirety on one line:
+class C18 { C18(int i); }; /* NOL
+INT */
+// CHECK-MESSAGES: :[[@LINE-2]]:13: warning: single-argument constructors must be marked explicit
+
+/* NO
+LINT */ class C19 { C19(int i); };
+// CHECK-MESSAGES: :[[@LINE-1]]:21: warning: single-argument constructors must be marked explicit
+
+// Spaces between items in the comma-separated check list are ignroed:
+class C20 { C20(int i); }; // NOLINT( google-explicit-constructor )
+class C21 { C21(int i); }; // NOLINT( google-explicit-constructor , some-other-check )
+class C22 { C22(int i); }; // NOLINT(google-explicit- constructor)
+// CHECK-MESSAGES: :[[@LINE-1]]:13: warning: single-argument constructors must be marked explicit
+
+// If there is a space between "NOLINT" and the bracket, it is treated as a regular NOLINT: 
+class C23 { C23(int i); }; // NOLINT (some-other-check)
+
 void f() {
   int i;
 // CHECK-MESSAGES: :[[@LINE-1]]:7: warning: unused variable 'i' [clang-diagnostic-unused-variable]
@@ -71,4 +116,4 @@ int array2[10];  // NOLINT(cppcoreguidelines-avoid-c-arrays)
 int array3[10];  // NOLINT(cppcoreguidelines-avoid-c-arrays,modernize-avoid-c-arrays)
 int array4[10];  // NOLINT(*-avoid-c-arrays)
 
-// CHECK-MESSAGES: Suppressed 23 warnings (23 NOLINT)
+// CHECK-MESSAGES: Suppressed 34 warnings (34 NOLINT)
diff --git a/clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend-LIFO.cpp b/clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend-LIFO.cpp
new file mode 100644
index 000000000000..ee5b1cca755a
--- /dev/null
+++ b/clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend-LIFO.cpp
@@ -0,0 +1,19 @@
+// RUN: not clang-tidy %s --checks='-*,google-explicit-constructor,google-readability-casting' 2>&1 | FileCheck %s
+
+// NOLINTBEGIN(google-explicit-constructor)
+// NOLINTBEGIN(google-readability-casting)
+class A { A(int i); };
+auto Num = (unsigned int)(-1);
+// NOLINTEND(google-explicit-constructor)
+// NOLINTEND(google-readability-casting)
+
+// Note: the expected output has been split over several lines so that clang-tidy
+//       does not see the "no lint" suppression comment and mistakenly assume it
+//       is meant for itself.
+// CHECK: :[[@LINE-10]]:4: error: unmatched 'NOLIN
+// CHECK: TBEGIN' comment without a subsequent 'NOLIN
+// CHECK: TEND' comment [clang-tidy-nolint]
+// CHECK: :[[@LINE-11]]:11: warning: single-argument constructors must be marked explicit
+// CHECK: :[[@LINE-10]]:4: error: unmatched 'NOLIN
+// CHECK: TEND' comment without a previous 'NOLIN
+// CHECK: TBEGIN' comment [clang-tidy-nolint]
diff --git a/clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend-begin-all-end-glob.cpp b/clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend-begin-all-end-glob.cpp
new file mode 100644
index 000000000000..90b9fa988302
--- /dev/null
+++ b/clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend-begin-all-end-glob.cpp
@@ -0,0 +1,16 @@
+// RUN: not clang-tidy %s --checks='-*,google-explicit-constructor' 2>&1 | FileCheck %s
+
+// NOLINTBEGIN
+class B { B(int i); };
+// NOLINTEND(*)
+
+// Note: the expected output has been split over several lines so that clang-tidy
+//       does not see the "no lint" suppression comment and mistakenly assume it
+//       is meant for itself.
+// CHECK: :[[@LINE-7]]:4: error: unmatched 'NOLIN
+// CHECK: TBEGIN' comment without a subsequent 'NOLIN
+// CHECK: TEND' comment [clang-tidy-nolint]
+// CHECK: :[[@LINE-9]]:11: warning: single-argument constructors must be marked explicit
+// CHECK: :[[@LINE-9]]:4: error: unmatched 'NOLIN
+// CHECK: TEND' comment without a previous 'NOLIN
+// CHECK: TBEGIN' comment [clang-tidy-nolint]
diff --git a/clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend-begin-all-end-specific.cpp b/clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend-begin-all-end-specific.cpp
new file mode 100644
index 000000000000..6ffa914e4ef0
--- /dev/null
+++ b/clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend-begin-all-end-specific.cpp
@@ -0,0 +1,16 @@
+// RUN: not clang-tidy %s --checks='-*,google-explicit-constructor' 2>&1 | FileCheck %s
+
+// NOLINTBEGIN
+class A { A(int i); };
+// NOLINTEND(google-explicit-constructor)
+
+// Note: the expected output has been split over several lines so that clang-tidy
+//       does not see the "no lint" suppression comment and mistakenly assume it
+//       is meant for itself.
+// CHECK: :[[@LINE-7]]:4: error: unmatched 'NOLIN
+// CHECK: TBEGIN' comment without a subsequent 'NOLIN
+// CHECK: TEND' comment [clang-tidy-nolint]
+// CHECK: :[[@LINE-9]]:11: warning: single-argument constructors must be marked explicit
+// CHECK: :[[@LINE-9]]:4: error: unmatched 'NOLIN
+// CHECK: TEND' comment without a previous 'NOLIN
+// CHECK: TBEGIN' comment [clang-tidy-nolint]
diff --git a/clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend-begin-glob-end-all.cpp b/clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend-begin-glob-end-all.cpp
new file mode 100644
index 000000000000..3697d5c11e2e
--- /dev/null
+++ b/clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend-begin-glob-end-all.cpp
@@ -0,0 +1,16 @@
+// RUN: not clang-tidy %s --checks="-*,google-explicit-constructor" 2>&1 | FileCheck %s
+
+// NOLINTBEGIN(*)
+class B { B(int i); };
+// NOLINTEND
+
+// Note: the expected output has been split over several lines so that clang-tidy
+//       does not see the "no lint" suppression comment and mistakenly assume it
+//       is meant for itself.
+// CHECK: :[[@LINE-7]]:4: error: unmatched 'NOLIN
+// CHECK: TBEGIN' comment without a subsequent 'NOLIN
+// CHECK: TEND' comment [clang-tidy-nolint]
+// CHECK: :[[@LINE-9]]:11: warning: single-argument constructors must be marked explicit
+// CHECK: :[[@LINE-9]]:4: error: unmatched 'NOLIN
+// CHECK: TEND' comment without a previous 'NOLIN
+// CHECK: TBEGIN' comment [clang-tidy-nolint]
diff --git a/clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend-begin-glob-end-specific.cpp b/clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend-begin-glob-end-specific.cpp
new file mode 100644
index 000000000000..5bdb117f2024
--- /dev/null
+++ b/clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend-begin-glob-end-specific.cpp
@@ -0,0 +1,16 @@
+// RUN: not clang-tidy %s --checks="-*,google-explicit-constructor" 2>&1 | FileCheck %s
+
+// NOLINTBEGIN(*)
+class B { B(int i); };
+// NOLINTEND(google-explicit-constructor)
+
+// Note: the expected output has been split over several lines so that clang-tidy
+//       does not see the "no lint" suppression comment and mistakenly assume it
+//       is meant for itself.
+// CHECK: :[[@LINE-7]]:4: error: unmatched 'NOLIN
+// CHECK: TBEGIN' comment without a subsequent 'NOLIN
+// CHECK: TEND' comment [clang-tidy-nolint]
+// CHECK: :[[@LINE-9]]:11: warning: single-argument constructors must be marked explicit
+// CHECK: :[[@LINE-9]]:4: error: unmatched 'NOLIN
+// CHECK: TEND' comment without a previous 'NOLIN
+// CHECK: TBEGIN' comment [clang-tidy-nolint]
diff --git a/clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend-begin-global-end-specific.cpp b/clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend-begin-global-end-specific.cpp
deleted file mode 100644
index 01e69ddf6352..000000000000
--- a/clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend-begin-global-end-specific.cpp
+++ /dev/null
@@ -1,25 +0,0 @@
-// RUN: not clang-tidy %s --checks='-*,google-explicit-constructor' 2>&1 | FileCheck %s
-
-// NOLINTBEGIN
-class A { A(int i); };
-// NOLINTEND(google-explicit-constructor)
-
-// Note: the expected output has been split over several lines so that clang-tidy
-//       does not see the "no lint" suppression comment and mistakenly assume it
-//       is meant for itself.
-// CHECK: :[[@LINE-6]]:11: warning: single-argument constructors must be marked explicit
-// CHECK: :[[@LINE-6]]:4: error: unmatched 'NOLIN
-// CHECK: TEND' comment without a previous 'NOLIN
-// CHECK: TBEGIN' comment [clang-tidy-nolint]
-
-// NOLINTBEGIN
-class B { B(int i); };
-// NOLINTEND(*)
-
-// Note: the expected output has been split over several lines so that clang-tidy
-//       does not see the "no lint" suppression comment and mistakenly assume it
-//       is meant for itself.
-// CHECK: :[[@LINE-6]]:11: warning: single-argument constructors must be marked explicit
-// CHECK: :[[@LINE-6]]:4: error: unmatched 'NOLIN
-// CHECK: TEND' comment without a previous 'NOLIN
-// CHECK: TBEGIN' comment [clang-tidy-nolint]
diff --git a/clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend-begin-multiple-end-single.cpp b/clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend-begin-multiple-end-single.cpp
new file mode 100644
index 000000000000..150913ce0ec6
--- /dev/null
+++ b/clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend-begin-multiple-end-single.cpp
@@ -0,0 +1,22 @@
+// RUN: not clang-tidy %s --checks='-*,google-explicit-constructor,google-readability-casting' 2>&1 | FileCheck %s
+
+// NOLINTBEGIN(google-explicit-constructor,google-readability-casting)
+class B { B(int i); };
+// NOLINTEND(google-explicit-constructor)
+auto Num2 = (unsigned int)(-1);
+// NOLINTEND(google-readability-casting)
+
+// Note: the expected output has been split over several lines so that clang-tidy
+//       does not see the "no lint" suppression comment and mistakenly assume it
+//       is meant for itself.
+// CHECK: :[[@LINE-9]]:4: error: unmatched 'NOLIN
+// CHECK: TBEGIN' comment without a subsequent 'NOLIN
+// CHECK: TEND' comment [clang-tidy-nolint]
+// CHECK: :[[@LINE-11]]:11: warning: single-argument constructors must be marked explicit
+// CHECK: :[[@LINE-11]]:4: error: unmatched 'NOLIN
+// CHECK: TEND' comment without a previous 'NOLIN
+// CHECK: TBEGIN' comment [clang-tidy-nolint]
+// CHECK: :[[@LINE-13]]:13: warning: C-style casts are discouraged; use static_cast
+// CHECK: :[[@LINE-13]]:4: error: unmatched 'NOLIN
+// CHECK: TEND' comment without a previous 'NOLIN
+// CHECK: TBEGIN' comment [clang-tidy-nolint]
diff --git a/clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend-begin-single-end-multiple.cpp b/clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend-begin-single-end-multiple.cpp
new file mode 100644
index 000000000000..f9a915c890cb
--- /dev/null
+++ b/clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend-begin-single-end-multiple.cpp
@@ -0,0 +1,22 @@
+// RUN: not clang-tidy %s --checks='-*,google-explicit-constructor,google-readability-casting' 2>&1 | FileCheck %s
+
+// NOLINTBEGIN(google-explicit-constructor)
+// NOLINTBEGIN(google-readability-casting)
+class B { B(int i); };
+auto Num2 = (unsigned int)(-1);
+// NOLINTEND(google-explicit-constructor,google-readability-casting)
+
+// Note: the expected output has been split over several lines so that clang-tidy
+//       does not see the "no lint" suppression comment and mistakenly assume it
+//       is meant for itself.
+// CHECK: :[[@LINE-9]]:4: error: unmatched 'NOLIN
+// CHECK: TBEGIN' comment without a subsequent 'NOLIN
+// CHECK: TEND' comment [clang-tidy-nolint]
+// CHECK: :[[@LINE-11]]:4: error: unmatched 'NOLIN
+// CHECK: TBEGIN' comment without a subsequent 'NOLIN
+// CHECK: TEND' comment [clang-tidy-nolint]
+// CHECK: :[[@LINE-13]]:11: warning: single-argument constructors must be marked explicit
+// CHECK: :[[@LINE-13]]:13: warning: C-style casts are discouraged; use static_cast
+// CHECK: :[[@LINE-13]]:4: error: unmatched 'NOLIN
+// CHECK: TEND' comment without a previous 'NOLIN
+// CHECK: TBEGIN' comment [clang-tidy-nolint]
diff --git a/clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend-begin-specific-end-all.cpp b/clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend-begin-specific-end-all.cpp
new file mode 100644
index 000000000000..decfe2dd5a4c
--- /dev/null
+++ b/clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend-begin-specific-end-all.cpp
@@ -0,0 +1,16 @@
+// RUN: not clang-tidy %s --checks="-*,google-explicit-constructor" 2>&1 | FileCheck %s
+
+// NOLINTBEGIN(google-explicit-constructor)
+class A { A(int i); };
+// NOLINTEND
+
+// Note: the expected output has been split over several lines so that clang-tidy
+//       does not see the "no lint" suppression comment and mistakenly assume it
+//       is meant for itself.
+// CHECK: :[[@LINE-7]]:4: error: unmatched 'NOLIN
+// CHECK: TBEGIN' comment without a subsequent 'NOLIN
+// CHECK: TEND' comment [clang-tidy-nolint]
+// CHECK: :[[@LINE-9]]:11: warning: single-argument constructors must be marked explicit
+// CHECK: :[[@LINE-9]]:4: error: unmatched 'NOLIN
+// CHECK: TEND' comment without a previous 'NOLIN
+// CHECK: TBEGIN' comment [clang-tidy-nolint]
diff --git a/clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend-begin-specific-end-glob.cpp b/clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend-begin-specific-end-glob.cpp
new file mode 100644
index 000000000000..a9f904ccce13
--- /dev/null
+++ b/clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend-begin-specific-end-glob.cpp
@@ -0,0 +1,16 @@
+// RUN: not clang-tidy %s --checks="-*,google-explicit-constructor" 2>&1 | FileCheck %s
+
+// NOLINTBEGIN(google-explicit-constructor)
+class A { A(int i); };
+// NOLINTEND(*)
+
+// Note: the expected output has been split over several lines so that clang-tidy
+//       does not see the "no lint" suppression comment and mistakenly assume it
+//       is meant for itself.
+// CHECK: :[[@LINE-7]]:4: error: unmatched 'NOLIN
+// CHECK: TBEGIN' comment without a subsequent 'NOLIN
+// CHECK: TEND' comment [clang-tidy-nolint]
+// CHECK: :[[@LINE-9]]:11: warning: single-argument constructors must be marked explicit
+// CHECK: :[[@LINE-9]]:4: error: unmatched 'NOLIN
+// CHECK: TEND' comment without a previous 'NOLIN
+// CHECK: TBEGIN' comment [clang-tidy-nolint]
diff --git a/clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend-begin-specific-end-global.cpp b/clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend-begin-specific-end-global.cpp
deleted file mode 100644
index c6fcfddd09ba..000000000000
--- a/clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend-begin-specific-end-global.cpp
+++ /dev/null
@@ -1,25 +0,0 @@
-// RUN: not clang-tidy %s --checks="-*,google-explicit-constructor" 2>&1 | FileCheck %s
-
-// NOLINTBEGIN(google-explicit-constructor)
-class A { A(int i); };
-// NOLINTEND
-
-// Note: the expected output has been split over several lines so that clang-tidy
-//       does not see the "no lint" suppression comment and mistakenly assume it
-//       is meant for itself.
-// CHECK: :[[@LINE-6]]:11: warning: single-argument constructors must be marked explicit
-// CHECK: :[[@LINE-6]]:4: error: unmatched 'NOLIN
-// CHECK: TEND' comment without a previous 'NOLIN
-// CHECK: TBEGIN' comment [clang-tidy-nolint]
-
-// NOLINTBEGIN(*)
-class B { B(int i); };
-// NOLINTEND
-
-// Note: the expected output has been split over several lines so that clang-tidy
-//       does not see the "no lint" suppression comment and mistakenly assume it
-//       is meant for itself.
-// CHECK: :[[@LINE-6]]:11: warning: single-argument constructors must be marked explicit
-// CHECK: :[[@LINE-6]]:4: error: unmatched 'NOLIN
-// CHECK: TEND' comment without a previous 'NOLIN
-// CHECK: TBEGIN' comment [clang-tidy-nolint]
diff --git a/clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend-mismatched-check-names.cpp b/clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend-mismatched-check-names.cpp
index 957b0b341a3c..8d7786fb8c71 100644
--- a/clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend-mismatched-check-names.cpp
+++ b/clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend-mismatched-check-names.cpp
@@ -16,24 +16,3 @@ auto Num = (unsigned int)(-1);
 // CHECK: :[[@LINE-10]]:4: error: unmatched 'NOLIN
 // CHECK: TEND' comment without a previous 'NOLIN
 // CHECK: TBEGIN' comment [clang-tidy-nolint]
-
-// NOLINTBEGIN(google-explicit-constructor,google-readability-casting)
-class B { B(int i); };
-// NOLINTEND(google-explicit-constructor)
-auto Num2 = (unsigned int)(-1);
-// NOLINTEND(google-readability-casting)
-
-// Note: the expected output has been split over several lines so that clang-tidy
-//       does not see the "no lint" suppression comment and mistakenly assume it
-//       is meant for itself.
-// CHECK: :[[@LINE-9]]:4: error: unmatched 'NOLIN
-// CHECK: TBEGIN' comment without a subsequent 'NOLIN
-// CHECK: TEND' comment [clang-tidy-nolint]
-// CHECK: :[[@LINE-11]]:11: warning: single-argument constructors must be marked explicit
-// CHECK: :[[@LINE-11]]:4: error: unmatched 'NOLIN
-// CHECK: TEND' comment without a previous 'NOLIN
-// CHECK: TBEGIN' comment [clang-tidy-nolint]
-// CHECK: :[[@LINE-13]]:13: warning: C-style casts are discouraged; use static_cast
-// CHECK: :[[@LINE-13]]:4: error: unmatched 'NOLIN
-// CHECK: TEND' comment without a previous 'NOLIN
-// CHECK: TBEGIN' comment [clang-tidy-nolint]
diff --git a/clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend-mismatched-delims.cpp b/clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend-mismatched-delims.cpp
index 7ed5fb820e50..4b8947e369f9 100644
--- a/clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend-mismatched-delims.cpp
+++ b/clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend-mismatched-delims.cpp
@@ -11,4 +11,3 @@ class A { A(int i); };
 // CHECK: :[[@LINE-8]]:4: error: unmatched 'NOLIN
 // CHECK: TBEGIN' comment without a subsequent 'NOLIN
 // CHECK: TEND' comment [clang-tidy-nolint]
-// CHECK: :[[@LINE-9]]:11: warning: single-argument constructors must be marked explicit
diff --git a/clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend-multiple-TUs.cpp b/clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend-multiple-TUs.cpp
new file mode 100644
index 000000000000..773e023cb22c
--- /dev/null
+++ b/clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend-multiple-TUs.cpp
@@ -0,0 +1,6 @@
+// RUN: clang-tidy %S/Inputs/nolintbeginend/1st-translation-unit.cpp %S/Inputs/nolintbeginend/2nd-translation-unit.cpp --checks='-*,google-explicit-constructor' 2>&1 | FileCheck %s
+
+// CHECK-NOT: 1st-translation-unit.cpp:2:11: warning: single-argument constructors must be marked explicit
+// CHECK: 1st-translation-unit.cpp:5:11: warning: single-argument constructors must be marked explicit
+// CHECK: 2nd-translation-unit.cpp:2:11: warning: single-argument constructors must be marked explicit
+// CHECK-NOT: 2nd-translation-unit.cpp:5:11: warning: single-argument constructors must be marked explicit
diff --git a/clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend-typo-in-check-name.cpp b/clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend-typo-in-check-name.cpp
index 0f2f9994c1fa..57e1ff331c8b 100644
--- a/clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend-typo-in-check-name.cpp
+++ b/clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend-typo-in-check-name.cpp
@@ -11,3 +11,6 @@ class A { A(int i); };
 // CHECK: TBEGIN' comment without a subsequent 'NOLIN
 // CHECK: TEND' comment [clang-tidy-nolint]
 // CHECK: :[[@LINE-9]]:11: warning: single-argument constructors must be marked explicit
+// CHECK: :[[@LINE-9]]:4: error: unmatched 'NOLIN
+// CHECK: TEND' comment without a previous 'NOLIN
+// CHECK: TBEGIN' comment [clang-tidy-nolint]
diff --git a/clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend.cpp b/clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend.cpp
index 837912853018..ae97bc5b5144 100644
--- a/clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend.cpp
+++ b/clang-tools-extra/test/clang-tidy/infrastructure/nolintbeginend.cpp
@@ -58,30 +58,24 @@ class C6 { C6(int i); };
 // NOLINTEND(some-other-check)
 // NOLINTEND(google-explicit-constructor)
 
-// NOLINTBEGIN(google-explicit-constructor)
-// NOLINTBEGIN(some-other-check)
-class C7 { C7(int i); };
-// NOLINTEND(google-explicit-constructor)
-// NOLINTEND(some-other-check)
-
 // NOLINTBEGIN(google-explicit-constructor)
 // NOLINTBEGIN
-class C8 { C8(int i); };
+class C7 { C7(int i); };
 // NOLINTEND
 // NOLINTEND(google-explicit-constructor)
 
 // NOLINTBEGIN
 // NOLINTBEGIN(google-explicit-constructor)
-class C9 { C9(int i); };
+class C8 { C8(int i); };
 // NOLINTEND(google-explicit-constructor)
 // NOLINTEND
 
 // NOLINTBEGIN(not-closed-bracket-is-treated-as-skip-all
-class C10 { C10(int i); };
+class C9 { C9(int i); };
 // NOLINTEND(not-closed-bracket-is-treated-as-skip-all
 
 // NOLINTBEGIN without-brackets-skip-all, another-check
-class C11 { C11(int i); };
+class C10 { C10(int i); };
 // NOLINTEND without-brackets-skip-all, another-check
 
 #define MACRO(X) class X { X(int i); };
@@ -114,28 +108,28 @@ MACRO_WRAPPED_WITH_NO_LINT
 MACRO_NO_LINT_INSIDE_MACRO
 
 // NOLINTBEGIN(google*)
-class C12 { C12(int i); };
+class C11 { C11(int i); };
 // NOLINTEND(google*)
 
 // NOLINTBEGIN(*explicit-constructor)
-class C15 { C15(int i); };
+class C12 { C12(int i); };
 // NOLINTEND(*explicit-constructor)
 
 // NOLINTBEGIN(*explicit*)
-class C16 { C16(int i); };
+class C13 { C13(int i); };
 // NOLINTEND(*explicit*)
 
 // NOLINTBEGIN(-explicit-constructor)
-class C17 { C17(int x); };
+class C14 { C14(int x); };
 // CHECK-MESSAGES: :[[@LINE-1]]:13: warning: single-argument constructors must be marked explicit
 // NOLINTEND(-explicit-constructor)
 
 // NOLINTBEGIN(google*,-google*)
-class C18 { C18(int x); };
+class C15 { C15(int x); };
 // NOLINTEND(google*,-google*)
 
 // NOLINTBEGIN(*,-google*)
-class C19 { C19(int x); };
+class C16 { C16(int x); };
 // NOLINTEND(*,-google*)
 
 int array1[10];
@@ -154,4 +148,4 @@ int array3[10];
 int array4[10];
 // NOLINTEND(*-avoid-c-arrays)
 
-// CHECK-MESSAGES: Suppressed 27 warnings (27 NOLINT).
+// CHECK-MESSAGES: Suppressed 26 warnings (26 NOLINT).