diff --git a/clang-tools-extra/clang-tidy/ClangTidy.cpp b/clang-tools-extra/clang-tidy/ClangTidy.cpp
--- a/clang-tools-extra/clang-tidy/ClangTidy.cpp
+++ b/clang-tools-extra/clang-tidy/ClangTidy.cpp
@@ -55,8 +55,7 @@
 
 LLVM_INSTANTIATE_REGISTRY(clang::tidy::ClangTidyModuleRegistry)
 
-namespace clang {
-namespace tidy {
+namespace clang::tidy {
 
 namespace {
 #if CLANG_TIDY_ENABLE_STATIC_ANALYZER
@@ -658,5 +657,4 @@
 
   return Result;
 }
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy
diff --git a/clang-tools-extra/clang-tidy/ClangTidyCheck.cpp b/clang-tools-extra/clang-tidy/ClangTidyCheck.cpp
--- a/clang-tools-extra/clang-tidy/ClangTidyCheck.cpp
+++ b/clang-tools-extra/clang-tidy/ClangTidyCheck.cpp
@@ -13,8 +13,7 @@
 #include "llvm/Support/YAMLParser.h"
 #include <optional>
 
-namespace clang {
-namespace tidy {
+namespace clang::tidy {
 
 ClangTidyCheck::ClangTidyCheck(StringRef CheckName, ClangTidyContext *Context)
     : CheckName(CheckName), Context(Context),
@@ -225,5 +224,4 @@
                                               StringRef Default) const {
   return getLocalOrGlobal(LocalName).value_or(Default);
 }
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy
diff --git a/clang-tools-extra/clang-tidy/ClangTidyDiagnosticConsumer.cpp b/clang-tools-extra/clang-tidy/ClangTidyDiagnosticConsumer.cpp
--- a/clang-tools-extra/clang-tidy/ClangTidyDiagnosticConsumer.cpp
+++ b/clang-tools-extra/clang-tidy/ClangTidyDiagnosticConsumer.cpp
@@ -319,8 +319,7 @@
   LastErrorPassesLineFilter = false;
 }
 
-namespace clang {
-namespace tidy {
+namespace clang::tidy {
 
 const llvm::StringMap<tooling::Replacements> *
 getFixIt(const tooling::Diagnostic &Diagnostic, bool GetFixFromNotes) {
@@ -340,8 +339,7 @@
   return Result;
 }
 
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy
 
 void ClangTidyDiagnosticConsumer::HandleDiagnostic(
     DiagnosticsEngine::Level DiagLevel, const Diagnostic &Info) {
diff --git a/clang-tools-extra/clang-tidy/ClangTidyModule.cpp b/clang-tools-extra/clang-tidy/ClangTidyModule.cpp
--- a/clang-tools-extra/clang-tidy/ClangTidyModule.cpp
+++ b/clang-tools-extra/clang-tidy/ClangTidyModule.cpp
@@ -13,8 +13,7 @@
 #include "ClangTidyModule.h"
 #include "ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
+namespace clang::tidy {
 
 void ClangTidyCheckFactories::registerCheckFactory(StringRef Name,
                                                    CheckFactory Factory) {
@@ -51,5 +50,4 @@
   return ClangTidyOptions();
 }
 
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy
diff --git a/clang-tools-extra/clang-tidy/ClangTidyOptions.cpp b/clang-tools-extra/clang-tidy/ClangTidyOptions.cpp
--- a/clang-tools-extra/clang-tidy/ClangTidyOptions.cpp
+++ b/clang-tools-extra/clang-tidy/ClangTidyOptions.cpp
@@ -28,8 +28,7 @@
 LLVM_YAML_IS_FLOW_SEQUENCE_VECTOR(FileFilter)
 LLVM_YAML_IS_FLOW_SEQUENCE_VECTOR(FileFilter::LineRange)
 
-namespace llvm {
-namespace yaml {
+namespace llvm::yaml {
 
 // Map std::pair<int, int> to a JSON array of size 2.
 template <> struct SequenceTraits<FileFilter::LineRange> {
@@ -135,11 +134,9 @@
   }
 };
 
-} // namespace yaml
-} // namespace llvm
+} // namespace llvm::yaml
 
-namespace clang {
-namespace tidy {
+namespace clang::tidy {
 
 ClangTidyOptions ClangTidyOptions::getDefaults() {
   ClangTidyOptions Options;
@@ -452,5 +449,4 @@
   return Stream.str();
 }
 
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy
diff --git a/clang-tools-extra/clang-tidy/ClangTidyProfiling.cpp b/clang-tools-extra/clang-tidy/ClangTidyProfiling.cpp
--- a/clang-tools-extra/clang-tidy/ClangTidyProfiling.cpp
+++ b/clang-tools-extra/clang-tidy/ClangTidyProfiling.cpp
@@ -17,8 +17,7 @@
 
 #define DEBUG_TYPE "clang-tidy-profiling"
 
-namespace clang {
-namespace tidy {
+namespace clang::tidy {
 
 ClangTidyProfiling::StorageParams::StorageParams(llvm::StringRef ProfilePrefix,
                                                  llvm::StringRef SourceFile)
@@ -87,5 +86,4 @@
     storeProfileData();
 }
 
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy
diff --git a/clang-tools-extra/clang-tidy/ExpandModularHeadersPPCallbacks.cpp b/clang-tools-extra/clang-tidy/ExpandModularHeadersPPCallbacks.cpp
--- a/clang-tools-extra/clang-tidy/ExpandModularHeadersPPCallbacks.cpp
+++ b/clang-tools-extra/clang-tidy/ExpandModularHeadersPPCallbacks.cpp
@@ -16,8 +16,7 @@
 
 #define DEBUG_TYPE "clang-tidy"
 
-namespace clang {
-namespace tooling {
+namespace clang::tooling {
 
 class ExpandModularHeadersPPCallbacks::FileRecorder {
 public:
@@ -306,5 +305,4 @@
   parseToLocation(Loc);
 }
 
-} // namespace tooling
-} // namespace clang
+} // namespace clang::tooling
diff --git a/clang-tools-extra/clang-tidy/GlobList.cpp b/clang-tools-extra/clang-tidy/GlobList.cpp
--- a/clang-tools-extra/clang-tidy/GlobList.cpp
+++ b/clang-tools-extra/clang-tidy/GlobList.cpp
@@ -10,8 +10,7 @@
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SmallString.h"
 
-namespace clang {
-namespace tidy {
+namespace clang::tidy {
 
 // Returns true if GlobList starts with the negative indicator ('-'), removes it
 // from the GlobList.
@@ -73,5 +72,4 @@
   return Value;
 }
 
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy
diff --git a/clang-tools-extra/clang-tidy/NoLintDirectiveHandler.cpp b/clang-tools-extra/clang-tidy/NoLintDirectiveHandler.cpp
--- a/clang-tools-extra/clang-tidy/NoLintDirectiveHandler.cpp
+++ b/clang-tools-extra/clang-tidy/NoLintDirectiveHandler.cpp
@@ -33,8 +33,7 @@
 #include <type_traits>
 #include <utility>
 
-namespace clang {
-namespace tidy {
+namespace clang::tidy {
 
 //===----------------------------------------------------------------------===//
 // NoLintType
@@ -411,5 +410,4 @@
                                EnableNoLintBlocks);
 }
 
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy
diff --git a/clang-tools-extra/clang-tidy/abseil/AbseilTidyModule.cpp b/clang-tools-extra/clang-tidy/abseil/AbseilTidyModule.cpp
--- a/clang-tools-extra/clang-tidy/abseil/AbseilTidyModule.cpp
+++ b/clang-tools-extra/clang-tidy/abseil/AbseilTidyModule.cpp
@@ -29,8 +29,7 @@
 #include "TimeSubtractionCheck.h"
 #include "UpgradeDurationConversionsCheck.h"
 
-namespace clang {
-namespace tidy {
+namespace clang::tidy {
 namespace abseil {
 
 class AbseilModule : public ClangTidyModule {
@@ -85,5 +84,4 @@
 // and thus register the AbseilModule.
 volatile int AbseilModuleAnchorSource = 0;
 
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy
diff --git a/clang-tools-extra/clang-tidy/abseil/CleanupCtadCheck.cpp b/clang-tools-extra/clang-tidy/abseil/CleanupCtadCheck.cpp
--- a/clang-tools-extra/clang-tidy/abseil/CleanupCtadCheck.cpp
+++ b/clang-tools-extra/clang-tidy/abseil/CleanupCtadCheck.cpp
@@ -19,9 +19,7 @@
 using namespace ::clang::ast_matchers;
 using namespace ::clang::transformer;
 
-namespace clang {
-namespace tidy {
-namespace abseil {
+namespace clang::tidy::abseil {
 
 RewriteRuleWith<std::string> CleanupCtadCheckImpl() {
   auto warning_message = cat("prefer absl::Cleanup's class template argument "
@@ -42,6 +40,4 @@
 CleanupCtadCheck::CleanupCtadCheck(StringRef Name, ClangTidyContext *Context)
     : utils::TransformerClangTidyCheck(CleanupCtadCheckImpl(), Name, Context) {}
 
-} // namespace abseil
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::abseil
diff --git a/clang-tools-extra/clang-tidy/abseil/DurationAdditionCheck.cpp b/clang-tools-extra/clang-tidy/abseil/DurationAdditionCheck.cpp
--- a/clang-tools-extra/clang-tidy/abseil/DurationAdditionCheck.cpp
+++ b/clang-tools-extra/clang-tidy/abseil/DurationAdditionCheck.cpp
@@ -15,9 +15,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace abseil {
+namespace clang::tidy::abseil {
 
 void DurationAdditionCheck::registerMatchers(MatchFinder *Finder) {
   Finder->addMatcher(
@@ -69,6 +67,4 @@
   diag(Binop->getBeginLoc(), "perform addition in the duration domain") << Hint;
 }
 
-} // namespace abseil
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::abseil
diff --git a/clang-tools-extra/clang-tidy/abseil/DurationComparisonCheck.cpp b/clang-tools-extra/clang-tidy/abseil/DurationComparisonCheck.cpp
--- a/clang-tools-extra/clang-tidy/abseil/DurationComparisonCheck.cpp
+++ b/clang-tools-extra/clang-tidy/abseil/DurationComparisonCheck.cpp
@@ -15,9 +15,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace abseil {
+namespace clang::tidy::abseil {
 
 void DurationComparisonCheck::registerMatchers(MatchFinder *Finder) {
   auto Matcher = expr(comparisonOperatorWithCallee(functionDecl(
@@ -55,6 +53,4 @@
                                           .str());
 }
 
-} // namespace abseil
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::abseil
diff --git a/clang-tools-extra/clang-tidy/abseil/DurationConversionCastCheck.cpp b/clang-tools-extra/clang-tidy/abseil/DurationConversionCastCheck.cpp
--- a/clang-tools-extra/clang-tidy/abseil/DurationConversionCastCheck.cpp
+++ b/clang-tools-extra/clang-tidy/abseil/DurationConversionCastCheck.cpp
@@ -15,9 +15,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace abseil {
+namespace clang::tidy::abseil {
 
 void DurationConversionCastCheck::registerMatchers(MatchFinder *Finder) {
   auto CallMatcher = ignoringImpCasts(callExpr(
@@ -81,6 +79,4 @@
   }
 }
 
-} // namespace abseil
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::abseil
diff --git a/clang-tools-extra/clang-tidy/abseil/DurationDivisionCheck.cpp b/clang-tools-extra/clang-tidy/abseil/DurationDivisionCheck.cpp
--- a/clang-tools-extra/clang-tidy/abseil/DurationDivisionCheck.cpp
+++ b/clang-tools-extra/clang-tidy/abseil/DurationDivisionCheck.cpp
@@ -11,9 +11,7 @@
 #include "clang/ASTMatchers/ASTMatchFinder.h"
 #include "clang/Lex/Lexer.h"
 
-namespace clang {
-namespace tidy {
-namespace abseil {
+namespace clang::tidy::abseil {
 
 using namespace clang::ast_matchers;
 
@@ -52,6 +50,4 @@
              ")");
 }
 
-} // namespace abseil
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::abseil
diff --git a/clang-tools-extra/clang-tidy/abseil/DurationFactoryFloatCheck.cpp b/clang-tools-extra/clang-tidy/abseil/DurationFactoryFloatCheck.cpp
--- a/clang-tools-extra/clang-tidy/abseil/DurationFactoryFloatCheck.cpp
+++ b/clang-tools-extra/clang-tidy/abseil/DurationFactoryFloatCheck.cpp
@@ -16,9 +16,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace abseil {
+namespace clang::tidy::abseil {
 
 // Returns `true` if `Range` is inside a macro definition.
 static bool insideMacroDefinition(const MatchFinder::MatchResult &Result,
@@ -66,6 +64,4 @@
   }
 }
 
-} // namespace abseil
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::abseil
diff --git a/clang-tools-extra/clang-tidy/abseil/DurationFactoryScaleCheck.cpp b/clang-tools-extra/clang-tidy/abseil/DurationFactoryScaleCheck.cpp
--- a/clang-tools-extra/clang-tidy/abseil/DurationFactoryScaleCheck.cpp
+++ b/clang-tools-extra/clang-tidy/abseil/DurationFactoryScaleCheck.cpp
@@ -15,9 +15,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace abseil {
+namespace clang::tidy::abseil {
 
 // Given the name of a duration factory function, return the appropriate
 // `DurationScale` for that factory.  If no factory can be found for
@@ -224,6 +222,4 @@
   }
 }
 
-} // namespace abseil
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::abseil
diff --git a/clang-tools-extra/clang-tidy/abseil/DurationRewriter.cpp b/clang-tools-extra/clang-tidy/abseil/DurationRewriter.cpp
--- a/clang-tools-extra/clang-tidy/abseil/DurationRewriter.cpp
+++ b/clang-tools-extra/clang-tidy/abseil/DurationRewriter.cpp
@@ -15,9 +15,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace abseil {
+namespace clang::tidy::abseil {
 
 struct DurationScale2IndexFunctor {
   using argument_type = DurationScale;
@@ -322,6 +320,4 @@
   return Loc.isMacroID();
 }
 
-} // namespace abseil
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::abseil
diff --git a/clang-tools-extra/clang-tidy/abseil/DurationSubtractionCheck.cpp b/clang-tools-extra/clang-tidy/abseil/DurationSubtractionCheck.cpp
--- a/clang-tools-extra/clang-tidy/abseil/DurationSubtractionCheck.cpp
+++ b/clang-tools-extra/clang-tidy/abseil/DurationSubtractionCheck.cpp
@@ -15,9 +15,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace abseil {
+namespace clang::tidy::abseil {
 
 void DurationSubtractionCheck::registerMatchers(MatchFinder *Finder) {
   Finder->addMatcher(
@@ -57,6 +55,4 @@
                  .str());
 }
 
-} // namespace abseil
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::abseil
diff --git a/clang-tools-extra/clang-tidy/abseil/DurationUnnecessaryConversionCheck.cpp b/clang-tools-extra/clang-tidy/abseil/DurationUnnecessaryConversionCheck.cpp
--- a/clang-tools-extra/clang-tidy/abseil/DurationUnnecessaryConversionCheck.cpp
+++ b/clang-tools-extra/clang-tidy/abseil/DurationUnnecessaryConversionCheck.cpp
@@ -15,9 +15,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace abseil {
+namespace clang::tidy::abseil {
 
 void DurationUnnecessaryConversionCheck::registerMatchers(MatchFinder *Finder) {
   for (const auto &Scale : {"Hours", "Minutes", "Seconds", "Milliseconds",
@@ -113,6 +111,4 @@
       << Hint;
 }
 
-} // namespace abseil
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::abseil
diff --git a/clang-tools-extra/clang-tidy/abseil/FasterStrsplitDelimiterCheck.cpp b/clang-tools-extra/clang-tidy/abseil/FasterStrsplitDelimiterCheck.cpp
--- a/clang-tools-extra/clang-tidy/abseil/FasterStrsplitDelimiterCheck.cpp
+++ b/clang-tools-extra/clang-tidy/abseil/FasterStrsplitDelimiterCheck.cpp
@@ -14,9 +14,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace abseil {
+namespace clang::tidy::abseil {
 
 namespace {
 
@@ -125,6 +123,4 @@
                                       *Replacement);
 }
 
-} // namespace abseil
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::abseil
diff --git a/clang-tools-extra/clang-tidy/abseil/NoInternalDependenciesCheck.cpp b/clang-tools-extra/clang-tidy/abseil/NoInternalDependenciesCheck.cpp
--- a/clang-tools-extra/clang-tidy/abseil/NoInternalDependenciesCheck.cpp
+++ b/clang-tools-extra/clang-tidy/abseil/NoInternalDependenciesCheck.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace abseil {
+namespace clang::tidy::abseil {
 
 void NoInternalDependenciesCheck::registerMatchers(MatchFinder *Finder) {
   // TODO: refactor matcher to be configurable or just match on any internal
@@ -45,6 +43,4 @@
        "details are reserved to Abseil");
 }
 
-} // namespace abseil
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::abseil
diff --git a/clang-tools-extra/clang-tidy/abseil/NoNamespaceCheck.cpp b/clang-tools-extra/clang-tidy/abseil/NoNamespaceCheck.cpp
--- a/clang-tools-extra/clang-tidy/abseil/NoNamespaceCheck.cpp
+++ b/clang-tools-extra/clang-tidy/abseil/NoNamespaceCheck.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace abseil {
+namespace clang::tidy::abseil {
 
 void NoNamespaceCheck::registerMatchers(MatchFinder *Finder) {
   Finder->addMatcher(
@@ -33,6 +31,4 @@
        "and should not be opened in user code");
 }
 
-} // namespace abseil
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::abseil
diff --git a/clang-tools-extra/clang-tidy/abseil/RedundantStrcatCallsCheck.cpp b/clang-tools-extra/clang-tidy/abseil/RedundantStrcatCallsCheck.cpp
--- a/clang-tools-extra/clang-tidy/abseil/RedundantStrcatCallsCheck.cpp
+++ b/clang-tools-extra/clang-tidy/abseil/RedundantStrcatCallsCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace abseil {
+namespace clang::tidy::abseil {
 
 // TODO: Features to add to the check:
 //  - Make it work if num_args > 26.
@@ -134,6 +132,4 @@
       << CheckResult.Hints;
 }
 
-}  // namespace abseil
-}  // namespace tidy
-}  // namespace clang
+} // namespace clang::tidy::abseil
diff --git a/clang-tools-extra/clang-tidy/abseil/StrCatAppendCheck.cpp b/clang-tools-extra/clang-tidy/abseil/StrCatAppendCheck.cpp
--- a/clang-tools-extra/clang-tidy/abseil/StrCatAppendCheck.cpp
+++ b/clang-tools-extra/clang-tidy/abseil/StrCatAppendCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace abseil {
+namespace clang::tidy::abseil {
 
 namespace {
 // Skips any combination of temporary materialization, temporary binding and
@@ -97,6 +95,4 @@
       << FixItHint::CreateInsertion(Call->getArg(0)->getBeginLoc(), "&");
 }
 
-}  // namespace abseil
-}  // namespace tidy
-}  // namespace clang
+} // namespace clang::tidy::abseil
diff --git a/clang-tools-extra/clang-tidy/abseil/StringFindStartswithCheck.cpp b/clang-tools-extra/clang-tidy/abseil/StringFindStartswithCheck.cpp
--- a/clang-tools-extra/clang-tidy/abseil/StringFindStartswithCheck.cpp
+++ b/clang-tools-extra/clang-tidy/abseil/StringFindStartswithCheck.cpp
@@ -17,9 +17,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace abseil {
+namespace clang::tidy::abseil {
 
 StringFindStartswithCheck::StringFindStartswithCheck(StringRef Name,
                                                      ClangTidyContext *Context)
@@ -142,6 +140,4 @@
   Options.store(Opts, "AbseilStringsMatchHeader", AbseilStringsMatchHeader);
 }
 
-} // namespace abseil
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::abseil
diff --git a/clang-tools-extra/clang-tidy/abseil/StringFindStrContainsCheck.cpp b/clang-tools-extra/clang-tidy/abseil/StringFindStrContainsCheck.cpp
--- a/clang-tools-extra/clang-tidy/abseil/StringFindStrContainsCheck.cpp
+++ b/clang-tools-extra/clang-tidy/abseil/StringFindStrContainsCheck.cpp
@@ -20,9 +20,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace abseil {
+namespace clang::tidy::abseil {
 
 using ::clang::transformer::addInclude;
 using ::clang::transformer::applyFirst;
@@ -107,6 +105,4 @@
                 AbseilStringsMatchHeaderOption);
 }
 
-} // namespace abseil
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::abseil
diff --git a/clang-tools-extra/clang-tidy/abseil/TimeComparisonCheck.cpp b/clang-tools-extra/clang-tidy/abseil/TimeComparisonCheck.cpp
--- a/clang-tools-extra/clang-tidy/abseil/TimeComparisonCheck.cpp
+++ b/clang-tools-extra/clang-tidy/abseil/TimeComparisonCheck.cpp
@@ -16,9 +16,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace abseil {
+namespace clang::tidy::abseil {
 
 void TimeComparisonCheck::registerMatchers(MatchFinder *Finder) {
   auto Matcher =
@@ -57,6 +55,4 @@
                                           .str());
 }
 
-} // namespace abseil
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::abseil
diff --git a/clang-tools-extra/clang-tidy/abseil/TimeSubtractionCheck.cpp b/clang-tools-extra/clang-tidy/abseil/TimeSubtractionCheck.cpp
--- a/clang-tools-extra/clang-tidy/abseil/TimeSubtractionCheck.cpp
+++ b/clang-tools-extra/clang-tidy/abseil/TimeSubtractionCheck.cpp
@@ -16,9 +16,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace abseil {
+namespace clang::tidy::abseil {
 
 // Returns `true` if `Range` is inside a macro definition.
 static bool insideMacroDefinition(const MatchFinder::MatchResult &Result,
@@ -197,6 +195,4 @@
   }
 }
 
-} // namespace abseil
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::abseil
diff --git a/clang-tools-extra/clang-tidy/abseil/UpgradeDurationConversionsCheck.cpp b/clang-tools-extra/clang-tidy/abseil/UpgradeDurationConversionsCheck.cpp
--- a/clang-tools-extra/clang-tidy/abseil/UpgradeDurationConversionsCheck.cpp
+++ b/clang-tools-extra/clang-tidy/abseil/UpgradeDurationConversionsCheck.cpp
@@ -14,9 +14,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace abseil {
+namespace clang::tidy::abseil {
 
 void UpgradeDurationConversionsCheck::registerMatchers(MatchFinder *Finder) {
   // For the arithmetic calls, we match only the uses of the templated operators
@@ -160,6 +158,4 @@
        << FixItHint::CreateInsertion(SourceRange.getEnd(), ")");
 }
 
-} // namespace abseil
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::abseil
diff --git a/clang-tools-extra/clang-tidy/add_new_check.py b/clang-tools-extra/clang-tidy/add_new_check.py
--- a/clang-tools-extra/clang-tidy/add_new_check.py
+++ b/clang-tools-extra/clang-tidy/add_new_check.py
@@ -77,9 +77,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace %(namespace)s {
+namespace clang::tidy::%(namespace)s {
 
 /// FIXME: Write a short description.
 ///
@@ -93,9 +91,7 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace %(namespace)s
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::%(namespace)s
 
 #endif // %(header_guard)s
 """ % {'header_guard': header_guard,
@@ -129,9 +125,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace %(namespace)s {
+namespace clang::tidy::%(namespace)s {
 
 void %(check_name)s::registerMatchers(MatchFinder *Finder) {
   // FIXME: Add matchers.
@@ -149,9 +143,7 @@
       << FixItHint::CreateInsertion(MatchedDecl->getLocation(), "awesome_");
 }
 
-} // namespace %(namespace)s
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::%(namespace)s
 """ % {'check_name': check_name_camel,
        'module': module,
        'namespace': namespace})
diff --git a/clang-tools-extra/clang-tidy/altera/AlteraTidyModule.cpp b/clang-tools-extra/clang-tidy/altera/AlteraTidyModule.cpp
--- a/clang-tools-extra/clang-tidy/altera/AlteraTidyModule.cpp
+++ b/clang-tools-extra/clang-tidy/altera/AlteraTidyModule.cpp
@@ -17,8 +17,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
+namespace clang::tidy {
 namespace altera {
 
 class AlteraModule : public ClangTidyModule {
@@ -46,5 +45,4 @@
 // and thus register the AlteraModule.
 volatile int AlteraModuleAnchorSource = 0;
 
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy
diff --git a/clang-tools-extra/clang-tidy/altera/IdDependentBackwardBranchCheck.cpp b/clang-tools-extra/clang-tidy/altera/IdDependentBackwardBranchCheck.cpp
--- a/clang-tools-extra/clang-tidy/altera/IdDependentBackwardBranchCheck.cpp
+++ b/clang-tools-extra/clang-tidy/altera/IdDependentBackwardBranchCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace altera {
+namespace clang::tidy::altera {
 
 void IdDependentBackwardBranchCheck::registerMatchers(MatchFinder *Finder) {
   // Prototype to identify all variables which hold a thread-variant ID.
@@ -259,6 +257,4 @@
   }
 }
 
-} // namespace altera
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::altera
diff --git a/clang-tools-extra/clang-tidy/altera/KernelNameRestrictionCheck.cpp b/clang-tools-extra/clang-tidy/altera/KernelNameRestrictionCheck.cpp
--- a/clang-tools-extra/clang-tidy/altera/KernelNameRestrictionCheck.cpp
+++ b/clang-tools-extra/clang-tidy/altera/KernelNameRestrictionCheck.cpp
@@ -15,9 +15,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace altera {
+namespace clang::tidy::altera {
 
 namespace {
 
@@ -102,6 +100,4 @@
   }
 }
 
-} // namespace altera
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::altera
diff --git a/clang-tools-extra/clang-tidy/altera/SingleWorkItemBarrierCheck.cpp b/clang-tools-extra/clang-tidy/altera/SingleWorkItemBarrierCheck.cpp
--- a/clang-tools-extra/clang-tidy/altera/SingleWorkItemBarrierCheck.cpp
+++ b/clang-tools-extra/clang-tidy/altera/SingleWorkItemBarrierCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace altera {
+namespace clang::tidy::altera {
 
 void SingleWorkItemBarrierCheck::registerMatchers(MatchFinder *Finder) {
   // Find any function that calls barrier but does not call an ID function.
@@ -79,6 +77,4 @@
   Options.store(Opts, "AOCVersion", AOCVersion);
 }
 
-} // namespace altera
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::altera
diff --git a/clang-tools-extra/clang-tidy/altera/StructPackAlignCheck.cpp b/clang-tools-extra/clang-tidy/altera/StructPackAlignCheck.cpp
--- a/clang-tools-extra/clang-tidy/altera/StructPackAlignCheck.cpp
+++ b/clang-tools-extra/clang-tidy/altera/StructPackAlignCheck.cpp
@@ -14,9 +14,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace altera {
+namespace clang::tidy::altera {
 
 void StructPackAlignCheck::registerMatchers(MatchFinder *Finder) {
   Finder->addMatcher(recordDecl(isStruct(), isDefinition(),
@@ -143,6 +141,4 @@
   Options.store(Opts, "MaxConfiguredAlignment", MaxConfiguredAlignment);
 }
 
-} // namespace altera
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::altera
diff --git a/clang-tools-extra/clang-tidy/altera/UnrollLoopsCheck.cpp b/clang-tools-extra/clang-tidy/altera/UnrollLoopsCheck.cpp
--- a/clang-tools-extra/clang-tidy/altera/UnrollLoopsCheck.cpp
+++ b/clang-tools-extra/clang-tidy/altera/UnrollLoopsCheck.cpp
@@ -17,9 +17,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace altera {
+namespace clang::tidy::altera {
 
 UnrollLoopsCheck::UnrollLoopsCheck(StringRef Name, ClangTidyContext *Context)
     : ClangTidyCheck(Name, Context),
@@ -267,6 +265,4 @@
   Options.store(Opts, "MaxLoopIterations", MaxLoopIterations);
 }
 
-} // namespace altera
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::altera
diff --git a/clang-tools-extra/clang-tidy/android/AndroidTidyModule.cpp b/clang-tools-extra/clang-tidy/android/AndroidTidyModule.cpp
--- a/clang-tools-extra/clang-tidy/android/AndroidTidyModule.cpp
+++ b/clang-tools-extra/clang-tidy/android/AndroidTidyModule.cpp
@@ -27,8 +27,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
+namespace clang::tidy {
 namespace android {
 
 /// This module is for Android specific checks.
@@ -69,5 +68,4 @@
 // and thus register the AndroidModule.
 volatile int AndroidModuleAnchorSource = 0;
 
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy
diff --git a/clang-tools-extra/clang-tidy/android/CloexecAccept4Check.cpp b/clang-tools-extra/clang-tidy/android/CloexecAccept4Check.cpp
--- a/clang-tools-extra/clang-tidy/android/CloexecAccept4Check.cpp
+++ b/clang-tools-extra/clang-tidy/android/CloexecAccept4Check.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace android {
+namespace clang::tidy::android {
 
 void CloexecAccept4Check::registerMatchers(MatchFinder *Finder) {
   auto SockAddrPointerType =
@@ -34,6 +32,4 @@
   insertMacroFlag(Result, /*MacroFlag=*/"SOCK_CLOEXEC", /*ArgPos=*/3);
 }
 
-} // namespace android
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::android
diff --git a/clang-tools-extra/clang-tidy/android/CloexecAcceptCheck.cpp b/clang-tools-extra/clang-tidy/android/CloexecAcceptCheck.cpp
--- a/clang-tools-extra/clang-tidy/android/CloexecAcceptCheck.cpp
+++ b/clang-tools-extra/clang-tidy/android/CloexecAcceptCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace android {
+namespace clang::tidy::android {
 
 void CloexecAcceptCheck::registerMatchers(MatchFinder *Finder) {
   auto SockAddrPointerType =
@@ -41,6 +39,4 @@
       ReplacementText);
 }
 
-} // namespace android
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::android
diff --git a/clang-tools-extra/clang-tidy/android/CloexecCheck.cpp b/clang-tools-extra/clang-tidy/android/CloexecCheck.cpp
--- a/clang-tools-extra/clang-tidy/android/CloexecCheck.cpp
+++ b/clang-tools-extra/clang-tidy/android/CloexecCheck.cpp
@@ -14,9 +14,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace android {
+namespace clang::tidy::android {
 
 namespace {
 // Helper function to form the correct string mode for Type3.
@@ -108,6 +106,4 @@
       SM, Result.Context->getLangOpts());
 }
 
-} // namespace android
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::android
diff --git a/clang-tools-extra/clang-tidy/android/CloexecCreatCheck.cpp b/clang-tools-extra/clang-tidy/android/CloexecCreatCheck.cpp
--- a/clang-tools-extra/clang-tidy/android/CloexecCreatCheck.cpp
+++ b/clang-tools-extra/clang-tidy/android/CloexecCreatCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace android {
+namespace clang::tidy::android {
 
 void CloexecCreatCheck::registerMatchers(MatchFinder *Finder) {
   auto CharPointerType = hasType(pointerType(pointee(isAnyCharacter())));
@@ -37,6 +35,4 @@
               ReplacementText);
 }
 
-} // namespace android
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::android
diff --git a/clang-tools-extra/clang-tidy/android/CloexecDupCheck.cpp b/clang-tools-extra/clang-tidy/android/CloexecDupCheck.cpp
--- a/clang-tools-extra/clang-tidy/android/CloexecDupCheck.cpp
+++ b/clang-tools-extra/clang-tidy/android/CloexecDupCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace android {
+namespace clang::tidy::android {
 
 void CloexecDupCheck::registerMatchers(MatchFinder *Finder) {
   registerMatchersImpl(Finder,
@@ -32,6 +30,4 @@
               ReplacementText);
 }
 
-} // namespace android
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::android
diff --git a/clang-tools-extra/clang-tidy/android/CloexecEpollCreate1Check.cpp b/clang-tools-extra/clang-tidy/android/CloexecEpollCreate1Check.cpp
--- a/clang-tools-extra/clang-tidy/android/CloexecEpollCreate1Check.cpp
+++ b/clang-tools-extra/clang-tidy/android/CloexecEpollCreate1Check.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace android {
+namespace clang::tidy::android {
 
 void CloexecEpollCreate1Check::registerMatchers(MatchFinder *Finder) {
   registerMatchersImpl(
@@ -27,6 +25,4 @@
   insertMacroFlag(Result, /*MacroFlag=*/"EPOLL_CLOEXEC", /*ArgPos=*/0);
 }
 
-} // namespace android
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::android
diff --git a/clang-tools-extra/clang-tidy/android/CloexecEpollCreateCheck.cpp b/clang-tools-extra/clang-tidy/android/CloexecEpollCreateCheck.cpp
--- a/clang-tools-extra/clang-tidy/android/CloexecEpollCreateCheck.cpp
+++ b/clang-tools-extra/clang-tidy/android/CloexecEpollCreateCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace android {
+namespace clang::tidy::android {
 
 void CloexecEpollCreateCheck::registerMatchers(MatchFinder *Finder) {
   registerMatchersImpl(
@@ -30,6 +28,4 @@
               "epoll_create1(EPOLL_CLOEXEC)");
 }
 
-} // namespace android
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::android
diff --git a/clang-tools-extra/clang-tidy/android/CloexecFopenCheck.cpp b/clang-tools-extra/clang-tidy/android/CloexecFopenCheck.cpp
--- a/clang-tools-extra/clang-tidy/android/CloexecFopenCheck.cpp
+++ b/clang-tools-extra/clang-tidy/android/CloexecFopenCheck.cpp
@@ -14,9 +14,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace android {
+namespace clang::tidy::android {
 
 void CloexecFopenCheck::registerMatchers(MatchFinder *Finder) {
   auto CharPointerType = hasType(pointerType(pointee(isAnyCharacter())));
@@ -31,6 +29,4 @@
   insertStringFlag(Result, /*Mode=*/'e', /*ArgPos=*/1);
 }
 
-} // namespace android
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::android
diff --git a/clang-tools-extra/clang-tidy/android/CloexecInotifyInit1Check.cpp b/clang-tools-extra/clang-tidy/android/CloexecInotifyInit1Check.cpp
--- a/clang-tools-extra/clang-tidy/android/CloexecInotifyInit1Check.cpp
+++ b/clang-tools-extra/clang-tidy/android/CloexecInotifyInit1Check.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace android {
+namespace clang::tidy::android {
 
 void CloexecInotifyInit1Check::registerMatchers(MatchFinder *Finder) {
   registerMatchersImpl(
@@ -27,6 +25,4 @@
   insertMacroFlag(Result, /*MacroFlag=*/"IN_CLOEXEC", /*ArgPos=*/0);
 }
 
-} // namespace android
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::android
diff --git a/clang-tools-extra/clang-tidy/android/CloexecInotifyInitCheck.cpp b/clang-tools-extra/clang-tidy/android/CloexecInotifyInitCheck.cpp
--- a/clang-tools-extra/clang-tidy/android/CloexecInotifyInitCheck.cpp
+++ b/clang-tools-extra/clang-tidy/android/CloexecInotifyInitCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace android {
+namespace clang::tidy::android {
 
 void CloexecInotifyInitCheck::registerMatchers(MatchFinder *Finder) {
   registerMatchersImpl(
@@ -28,6 +26,4 @@
               /*FixMsg=*/"inotify_init1(IN_CLOEXEC)");
 }
 
-} // namespace android
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::android
diff --git a/clang-tools-extra/clang-tidy/android/CloexecMemfdCreateCheck.cpp b/clang-tools-extra/clang-tidy/android/CloexecMemfdCreateCheck.cpp
--- a/clang-tools-extra/clang-tidy/android/CloexecMemfdCreateCheck.cpp
+++ b/clang-tools-extra/clang-tidy/android/CloexecMemfdCreateCheck.cpp
@@ -10,9 +10,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace android {
+namespace clang::tidy::android {
 
 void CloexecMemfdCreateCheck::registerMatchers(MatchFinder *Finder) {
   auto CharPointerType = hasType(pointerType(pointee(isAnyCharacter())));
@@ -26,6 +24,4 @@
   insertMacroFlag(Result, "MFD_CLOEXEC", /*ArgPos=*/1);
 }
 
-} // namespace android
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::android
diff --git a/clang-tools-extra/clang-tidy/android/CloexecOpenCheck.cpp b/clang-tools-extra/clang-tidy/android/CloexecOpenCheck.cpp
--- a/clang-tools-extra/clang-tidy/android/CloexecOpenCheck.cpp
+++ b/clang-tools-extra/clang-tidy/android/CloexecOpenCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace android {
+namespace clang::tidy::android {
 
 void CloexecOpenCheck::registerMatchers(MatchFinder *Finder) {
   auto CharPointerType = hasType(pointerType(pointee(isAnyCharacter())));
@@ -38,6 +36,4 @@
   insertMacroFlag(Result, /*MacroFlag=*/"O_CLOEXEC", ArgPos);
 }
 
-} // namespace android
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::android
diff --git a/clang-tools-extra/clang-tidy/android/CloexecPipe2Check.cpp b/clang-tools-extra/clang-tidy/android/CloexecPipe2Check.cpp
--- a/clang-tools-extra/clang-tidy/android/CloexecPipe2Check.cpp
+++ b/clang-tools-extra/clang-tidy/android/CloexecPipe2Check.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace android {
+namespace clang::tidy::android {
 
 void CloexecPipe2Check::registerMatchers(MatchFinder *Finder) {
   registerMatchersImpl(Finder,
@@ -28,6 +26,4 @@
   insertMacroFlag(Result, /*MacroFlag=*/"O_CLOEXEC", /*ArgPos=*/1);
 }
 
-} // namespace android
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::android
diff --git a/clang-tools-extra/clang-tidy/android/CloexecPipeCheck.cpp b/clang-tools-extra/clang-tidy/android/CloexecPipeCheck.cpp
--- a/clang-tools-extra/clang-tidy/android/CloexecPipeCheck.cpp
+++ b/clang-tools-extra/clang-tidy/android/CloexecPipeCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace android {
+namespace clang::tidy::android {
 
 void CloexecPipeCheck::registerMatchers(MatchFinder *Finder) {
   registerMatchersImpl(Finder,
@@ -32,6 +30,4 @@
       ReplacementText);
 }
 
-} // namespace android
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::android
diff --git a/clang-tools-extra/clang-tidy/android/CloexecSocketCheck.cpp b/clang-tools-extra/clang-tidy/android/CloexecSocketCheck.cpp
--- a/clang-tools-extra/clang-tidy/android/CloexecSocketCheck.cpp
+++ b/clang-tools-extra/clang-tidy/android/CloexecSocketCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace android {
+namespace clang::tidy::android {
 
 void CloexecSocketCheck::registerMatchers(MatchFinder *Finder) {
   registerMatchersImpl(Finder,
@@ -29,6 +27,4 @@
   insertMacroFlag(Result, /*MacroFlag=*/"SOCK_CLOEXEC", /*ArgPos=*/1);
 }
 
-} // namespace android
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::android
diff --git a/clang-tools-extra/clang-tidy/android/ComparisonInTempFailureRetryCheck.cpp b/clang-tools-extra/clang-tidy/android/ComparisonInTempFailureRetryCheck.cpp
--- a/clang-tools-extra/clang-tidy/android/ComparisonInTempFailureRetryCheck.cpp
+++ b/clang-tools-extra/clang-tidy/android/ComparisonInTempFailureRetryCheck.cpp
@@ -14,9 +14,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace android {
+namespace clang::tidy::android {
 
 ComparisonInTempFailureRetryCheck::ComparisonInTempFailureRetryCheck(
     StringRef Name, ClangTidyContext *Context)
@@ -90,6 +88,4 @@
   // happen, e.g. `TEMP_FAILURE_RETRY(IS_ZERO(foo()))`
 }
 
-} // namespace android
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::android
diff --git a/clang-tools-extra/clang-tidy/boost/BoostTidyModule.cpp b/clang-tools-extra/clang-tidy/boost/BoostTidyModule.cpp
--- a/clang-tools-extra/clang-tidy/boost/BoostTidyModule.cpp
+++ b/clang-tools-extra/clang-tidy/boost/BoostTidyModule.cpp
@@ -12,8 +12,7 @@
 #include "UseToStringCheck.h"
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
+namespace clang::tidy {
 namespace boost {
 
 class BoostModule : public ClangTidyModule {
@@ -33,5 +32,4 @@
 // and thus register the BoostModule.
 volatile int BoostModuleAnchorSource = 0;
 
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy
diff --git a/clang-tools-extra/clang-tidy/boost/UseToStringCheck.cpp b/clang-tools-extra/clang-tidy/boost/UseToStringCheck.cpp
--- a/clang-tools-extra/clang-tidy/boost/UseToStringCheck.cpp
+++ b/clang-tools-extra/clang-tidy/boost/UseToStringCheck.cpp
@@ -10,9 +10,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace boost {
+namespace clang::tidy::boost {
 
 namespace {
 AST_MATCHER(Type, isStrictlyInteger) {
@@ -66,6 +64,4 @@
       (llvm::Twine("std::to_") + StringType + "(").str());
 }
 
-} // namespace boost
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::boost
diff --git a/clang-tools-extra/clang-tidy/bugprone/ArgumentCommentCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/ArgumentCommentCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/ArgumentCommentCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/ArgumentCommentCheck.cpp
@@ -16,9 +16,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 namespace {
 AST_MATCHER(Decl, isFromStdNamespaceOrSystemHeader) {
   if (const auto *D = Node.getDeclContext()->getEnclosingNamespaceContext())
@@ -368,6 +366,4 @@
   }
 }
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/AssertSideEffectCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/AssertSideEffectCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/AssertSideEffectCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/AssertSideEffectCheck.cpp
@@ -21,9 +21,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 namespace {
 
@@ -134,6 +132,4 @@
       << AssertMacroName;
 }
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/AssignmentInIfConditionCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/AssignmentInIfConditionCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/AssignmentInIfConditionCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/AssignmentInIfConditionCheck.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 void AssignmentInIfConditionCheck::registerMatchers(MatchFinder *Finder) {
   Finder->addMatcher(translationUnitDecl(), this);
@@ -76,6 +74,4 @@
        DiagnosticIDs::Note);
 }
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/BadSignalToKillThreadCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/BadSignalToKillThreadCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/BadSignalToKillThreadCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/BadSignalToKillThreadCheck.cpp
@@ -14,9 +14,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 void BadSignalToKillThreadCheck::registerMatchers(MatchFinder *Finder) {
   Finder->addMatcher(
@@ -70,6 +68,4 @@
   PP = Pp;
 }
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/BoolPointerImplicitConversionCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/BoolPointerImplicitConversionCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/BoolPointerImplicitConversionCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/BoolPointerImplicitConversionCheck.cpp
@@ -10,9 +10,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 void BoolPointerImplicitConversionCheck::registerMatchers(MatchFinder *Finder) {
   // Look for ifs that have an implicit bool* to bool conversion in the
@@ -84,6 +82,4 @@
   }
 }
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/BranchCloneCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/BranchCloneCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/BranchCloneCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/BranchCloneCheck.cpp
@@ -64,9 +64,7 @@
   return true;
 }
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 void BranchCloneCheck::registerMatchers(MatchFinder *Finder) {
   Finder->addMatcher(
@@ -238,6 +236,4 @@
   llvm_unreachable("No if statement and no switch statement.");
 }
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/BugproneTidyModule.cpp b/clang-tools-extra/clang-tidy/bugprone/BugproneTidyModule.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/BugproneTidyModule.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/BugproneTidyModule.cpp
@@ -76,8 +76,7 @@
 #include "UseAfterMoveCheck.h"
 #include "VirtualNearMissCheck.h"
 
-namespace clang {
-namespace tidy {
+namespace clang::tidy {
 namespace bugprone {
 
 class BugproneModule : public ClangTidyModule {
@@ -220,5 +219,4 @@
 // and thus register the BugproneModule.
 volatile int BugproneModuleAnchorSource = 0;
 
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy
diff --git a/clang-tools-extra/clang-tidy/bugprone/CopyConstructorInitCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/CopyConstructorInitCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/CopyConstructorInitCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/CopyConstructorInitCheck.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 void CopyConstructorInitCheck::registerMatchers(MatchFinder *Finder) {
   // In the future this might be extended to move constructors?
@@ -112,6 +110,4 @@
   Diag << FixItHint::CreateInsertion(FixItLoc, FixItMsg);
 }
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/DanglingHandleCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/DanglingHandleCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/DanglingHandleCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/DanglingHandleCheck.cpp
@@ -15,9 +15,7 @@
 using namespace clang::ast_matchers;
 using namespace clang::tidy::matchers;
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 namespace {
 
@@ -187,6 +185,4 @@
       << Handle->getQualifiedNameAsString();
 }
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/DynamicStaticInitializersCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/DynamicStaticInitializersCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/DynamicStaticInitializersCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/DynamicStaticInitializersCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 AST_MATCHER(clang::VarDecl, hasConstantDeclaration) {
   const Expr *Init = Node.getInit();
@@ -62,6 +60,4 @@
     << Var;
 }
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/EasilySwappableParametersCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/EasilySwappableParametersCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/EasilySwappableParametersCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/EasilySwappableParametersCheck.cpp
@@ -89,9 +89,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 using TheCheck = EasilySwappableParametersCheck;
 
@@ -2311,6 +2309,4 @@
   }
 }
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/ExceptionEscapeCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/ExceptionEscapeCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/ExceptionEscapeCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/ExceptionEscapeCheck.cpp
@@ -23,8 +23,7 @@
 }
 } // namespace
 
-namespace tidy {
-namespace bugprone {
+namespace tidy::bugprone {
 ExceptionEscapeCheck::ExceptionEscapeCheck(StringRef Name,
                                            ClangTidyContext *Context)
     : ClangTidyCheck(Name, Context), RawFunctionsThatShouldNotThrow(Options.get(
@@ -77,6 +76,5 @@
         << MatchedDecl;
 }
 
-} // namespace bugprone
-} // namespace tidy
+} // namespace tidy::bugprone
 } // namespace clang
diff --git a/clang-tools-extra/clang-tidy/bugprone/FoldInitTypeCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/FoldInitTypeCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/FoldInitTypeCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/FoldInitTypeCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 void FoldInitTypeCheck::registerMatchers(MatchFinder *Finder) {
   // We match functions of interest and bind the iterator and init value types.
@@ -134,6 +132,4 @@
     doCheck(*Iter2ValueType, *InitType, *Result.Context, *CallNode);
 }
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/ForwardDeclarationNamespaceCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/ForwardDeclarationNamespaceCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/ForwardDeclarationNamespaceCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/ForwardDeclarationNamespaceCheck.cpp
@@ -16,9 +16,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 void ForwardDeclarationNamespaceCheck::registerMatchers(MatchFinder *Finder) {
   // Match all class declarations/definitions *EXCEPT*
@@ -168,6 +166,4 @@
   }
 }
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/ForwardingReferenceOverloadCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/ForwardingReferenceOverloadCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/ForwardingReferenceOverloadCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/ForwardingReferenceOverloadCheck.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 namespace {
 // Check if the given type is related to std::enable_if.
@@ -145,6 +143,4 @@
   }
 }
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/ImplicitWideningOfMultiplicationResultCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/ImplicitWideningOfMultiplicationResultCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/ImplicitWideningOfMultiplicationResultCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/ImplicitWideningOfMultiplicationResultCheck.cpp
@@ -21,9 +21,7 @@
 } // namespace
 } // namespace clang
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 static const Expr *getLHSOfMulBinOp(const Expr *E) {
   assert(E == E->IgnoreParens() && "Already skipped all parens!");
@@ -273,6 +271,4 @@
     handlePointerOffsetting(MatchedDecl);
 }
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/InaccurateEraseCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/InaccurateEraseCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/InaccurateEraseCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/InaccurateEraseCheck.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 void InaccurateEraseCheck::registerMatchers(MatchFinder *Finder) {
   const auto EndCall =
@@ -61,6 +59,4 @@
       << Hint;
 }
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/IncorrectRoundingsCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/IncorrectRoundingsCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/IncorrectRoundingsCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/IncorrectRoundingsCheck.cpp
@@ -15,9 +15,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 namespace {
 AST_MATCHER(FloatingLiteral, floatHalf) {
@@ -66,6 +64,4 @@
        "consider using lround (#include <cmath>) instead");
 }
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/InfiniteLoopCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/InfiniteLoopCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/InfiniteLoopCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/InfiniteLoopCheck.cpp
@@ -31,8 +31,7 @@
   return Node.getNoReturnAttr();
 }
 } // namespace ast_matchers
-namespace tidy {
-namespace bugprone {
+namespace tidy::bugprone {
 
 static internal::Matcher<Stmt>
 loopEndingStmt(internal::Matcher<Stmt> Internal) {
@@ -329,6 +328,5 @@
   }
 }
 
-} // namespace bugprone
-} // namespace tidy
+} // namespace tidy::bugprone
 } // namespace clang
diff --git a/clang-tools-extra/clang-tidy/bugprone/IntegerDivisionCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/IntegerDivisionCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/IntegerDivisionCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/IntegerDivisionCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 void IntegerDivisionCheck::registerMatchers(MatchFinder *Finder) {
   const auto IntType = hasType(isInteger());
@@ -49,6 +47,4 @@
                               "point context; possible loss of precision");
 }
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/LambdaFunctionNameCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/LambdaFunctionNameCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/LambdaFunctionNameCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/LambdaFunctionNameCheck.cpp
@@ -15,9 +15,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 namespace {
 
@@ -93,6 +91,4 @@
       << PredefinedExpr::getIdentKindName(E->getIdentKind());
 }
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/MacroParenthesesCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/MacroParenthesesCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/MacroParenthesesCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/MacroParenthesesCheck.cpp
@@ -11,9 +11,7 @@
 #include "clang/Lex/PPCallbacks.h"
 #include "clang/Lex/Preprocessor.h"
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 namespace {
 class MacroParenthesesPPCallbacks : public PPCallbacks {
@@ -268,6 +266,4 @@
   PP->addPPCallbacks(std::make_unique<MacroParenthesesPPCallbacks>(PP, this));
 }
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/MacroRepeatedSideEffectsCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/MacroRepeatedSideEffectsCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/MacroRepeatedSideEffectsCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/MacroRepeatedSideEffectsCheck.cpp
@@ -13,9 +13,7 @@
 #include "clang/Lex/PPCallbacks.h"
 #include "clang/Lex/Preprocessor.h"
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 namespace {
 class MacroRepeatedPPCallbacks : public PPCallbacks {
@@ -175,6 +173,4 @@
   PP->addPPCallbacks(::std::make_unique<MacroRepeatedPPCallbacks>(*this, *PP));
 }
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/MisplacedOperatorInStrlenInAllocCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/MisplacedOperatorInStrlenInAllocCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/MisplacedOperatorInStrlenInAllocCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/MisplacedOperatorInStrlenInAllocCheck.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 void MisplacedOperatorInStrlenInAllocCheck::registerMatchers(
     MatchFinder *Finder) {
@@ -108,6 +106,4 @@
       << StrLen->getDirectCallee()->getName() << Hint;
 }
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/MisplacedPointerArithmeticInAllocCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/MisplacedPointerArithmeticInAllocCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/MisplacedPointerArithmeticInAllocCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/MisplacedPointerArithmeticInAllocCheck.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 void MisplacedPointerArithmeticInAllocCheck::registerMatchers(
     MatchFinder *Finder) {
@@ -99,6 +97,4 @@
       << FixItHint::CreateInsertion(NewRParen, RParen);
 }
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/MisplacedWideningCastCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/MisplacedWideningCastCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/MisplacedWideningCastCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/MisplacedWideningCastCheck.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 MisplacedWideningCastCheck::MisplacedWideningCastCheck(
     StringRef Name, ClangTidyContext *Context)
@@ -226,6 +224,4 @@
       << CalcType << CastType;
 }
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/MoveForwardingReferenceCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/MoveForwardingReferenceCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/MoveForwardingReferenceCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/MoveForwardingReferenceCheck.cpp
@@ -14,9 +14,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 static void replaceMoveWithForward(const UnresolvedLookupExpr *Callee,
                                    const ParmVarDecl *ParmVar,
@@ -124,6 +122,4 @@
                          *Result.Context);
 }
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/MultipleStatementMacroCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/MultipleStatementMacroCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/MultipleStatementMacroCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/MultipleStatementMacroCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 namespace {
 
@@ -101,6 +99,4 @@
                                       "unconditionally executed");
 }
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/NoEscapeCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/NoEscapeCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/NoEscapeCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/NoEscapeCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 void NoEscapeCheck::registerMatchers(MatchFinder *Finder) {
   Finder->addMatcher(callExpr(callee(functionDecl(hasName("::dispatch_async"))),
@@ -46,6 +44,4 @@
   }
 }
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/NotNullTerminatedResultCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/NotNullTerminatedResultCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/NotNullTerminatedResultCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/NotNullTerminatedResultCheck.cpp
@@ -17,9 +17,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 constexpr llvm::StringLiteral FunctionExprName = "FunctionExpr";
 constexpr llvm::StringLiteral CastExprName = "CastExpr";
@@ -1010,6 +1008,4 @@
   lengthArgHandle(LengthHandleKind::Increase, Result, Diag);
 }
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/ParentVirtualCallCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/ParentVirtualCallCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/ParentVirtualCallCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/ParentVirtualCallCheck.cpp
@@ -17,9 +17,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 using BasesVector = llvm::SmallVector<const CXXRecordDecl *, 5>;
 
@@ -147,6 +145,4 @@
         getNameAsString(Parents.front()) + "::");
 }
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/PosixReturnCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/PosixReturnCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/PosixReturnCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/PosixReturnCheck.cpp
@@ -14,9 +14,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 static StringRef getFunctionSpelling(const MatchFinder::MatchResult &Result,
                                      const char *BindingStr) {
@@ -82,6 +80,4 @@
       << getFunctionSpelling(Result, "binop");
 }
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/RedundantBranchConditionCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/RedundantBranchConditionCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/RedundantBranchConditionCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/RedundantBranchConditionCheck.cpp
@@ -16,9 +16,7 @@
 using namespace clang::ast_matchers;
 using clang::tidy::utils::hasPtrOrReferenceInFunc;
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 static const char CondVarStr[] = "cond_var";
 static const char OuterIfStr[] = "outer_if";
@@ -177,6 +175,4 @@
   }
 }
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/ReservedIdentifierCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/ReservedIdentifierCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/ReservedIdentifierCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/ReservedIdentifierCheck.cpp
@@ -20,9 +20,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 static const char DoubleUnderscoreTag[] = "du";
 static const char UnderscoreCapitalTag[] = "uc";
@@ -180,6 +178,4 @@
                   }};
 }
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/SharedPtrArrayMismatchCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/SharedPtrArrayMismatchCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/SharedPtrArrayMismatchCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/SharedPtrArrayMismatchCheck.cpp
@@ -10,9 +10,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 SharedPtrArrayMismatchCheck::SharedPtrArrayMismatchCheck(
     StringRef Name, ClangTidyContext *Context)
@@ -26,6 +24,4 @@
           0, templateArgument(refersToType(qualType().bind(PointerTypeN)))));
 }
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/SignalHandlerCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/SignalHandlerCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/SignalHandlerCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/SignalHandlerCheck.cpp
@@ -219,8 +219,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
+namespace clang::tidy {
 
 template <>
 struct OptionEnumMapping<
@@ -560,5 +559,4 @@
 }
 
 } // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy
diff --git a/clang-tools-extra/clang-tidy/bugprone/SignedCharMisuseCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/SignedCharMisuseCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/SignedCharMisuseCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/SignedCharMisuseCheck.cpp
@@ -14,9 +14,7 @@
 using namespace clang::ast_matchers;
 using namespace clang::ast_matchers::internal;
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 static constexpr int UnsignedASCIIUpperBound = 127;
 
@@ -168,6 +166,4 @@
   }
 }
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/SizeofContainerCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/SizeofContainerCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/SizeofContainerCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/SizeofContainerCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 void SizeofContainerCheck::registerMatchers(MatchFinder *Finder) {
   Finder->addMatcher(
@@ -43,6 +41,4 @@
                                   "container; did you mean .size()?");
 }
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/SizeofExpressionCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/SizeofExpressionCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/SizeofExpressionCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/SizeofExpressionCheck.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 namespace {
 
@@ -360,6 +358,4 @@
   }
 }
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/SmartPtrArrayMismatchCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/SmartPtrArrayMismatchCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/SmartPtrArrayMismatchCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/SmartPtrArrayMismatchCheck.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 namespace {
 
@@ -117,6 +115,4 @@
   }
 }
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/SpuriouslyWakeUpFunctionsCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/SpuriouslyWakeUpFunctionsCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/SpuriouslyWakeUpFunctionsCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/SpuriouslyWakeUpFunctionsCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 void SpuriouslyWakeUpFunctionsCheck::registerMatchers(MatchFinder *Finder) {
 
@@ -86,6 +84,4 @@
        "conditional parameter}1")
       << WaitName << (WaitName != "cnd_wait" && WaitName != "cnd_timedwait");
 }
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/StandaloneEmptyCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/StandaloneEmptyCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/StandaloneEmptyCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/StandaloneEmptyCheck.cpp
@@ -24,9 +24,7 @@
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/Support/Casting.h"
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 using ast_matchers::BoundNodes;
 using ast_matchers::callee;
@@ -207,6 +205,4 @@
   }
 }
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/StringConstructorCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/StringConstructorCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/StringConstructorCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/StringConstructorCheck.cpp
@@ -14,9 +14,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 namespace {
 AST_MATCHER_P(IntegerLiteral, isBiggerThan, unsigned, N) {
@@ -183,6 +181,4 @@
   }
 }
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/StringIntegerAssignmentCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/StringIntegerAssignmentCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/StringIntegerAssignmentCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/StringIntegerAssignmentCheck.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 void StringIntegerAssignmentCheck::registerMatchers(MatchFinder *Finder) {
   Finder->addMatcher(
@@ -177,6 +175,4 @@
   }
 }
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/StringLiteralWithEmbeddedNulCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/StringLiteralWithEmbeddedNulCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/StringLiteralWithEmbeddedNulCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/StringLiteralWithEmbeddedNulCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 namespace {
 AST_MATCHER(StringLiteral, containsNul) {
@@ -79,6 +77,4 @@
   }
 }
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/StringviewNullptrCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/StringviewNullptrCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/StringviewNullptrCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/StringviewNullptrCheck.cpp
@@ -18,9 +18,7 @@
 #include "clang/Tooling/Transformer/Stencil.h"
 #include "llvm/ADT/StringRef.h"
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 using namespace ::clang::ast_matchers;
 using namespace ::clang::transformer;
@@ -302,6 +300,4 @@
     : utils::TransformerClangTidyCheck(StringviewNullptrCheckImpl(), Name,
                                        Context) {}
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/SuspiciousEnumUsageCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/SuspiciousEnumUsageCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/SuspiciousEnumUsageCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/SuspiciousEnumUsageCheck.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 static const char DifferentEnumErrorMessage[] =
     "enum values are from different enum types";
@@ -208,6 +206,4 @@
   checkSuspiciousBitmaskUsage(RhsExpr, EnumDec);
 }
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/SuspiciousIncludeCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/SuspiciousIncludeCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/SuspiciousIncludeCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/SuspiciousIncludeCheck.cpp
@@ -11,9 +11,7 @@
 #include "clang/Lex/Preprocessor.h"
 #include <optional>
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 namespace {
 class SuspiciousIncludePPCallbacks : public PPCallbacks {
@@ -104,6 +102,4 @@
   }
 }
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/SuspiciousMemoryComparisonCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/SuspiciousMemoryComparisonCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/SuspiciousMemoryComparisonCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/SuspiciousMemoryComparisonCheck.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 static std::optional<uint64_t> tryEvaluateSizeExpr(const Expr *SizeExpr,
                                                    const ASTContext &Ctx) {
@@ -81,6 +79,4 @@
   }
 }
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/SuspiciousMemsetUsageCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/SuspiciousMemsetUsageCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/SuspiciousMemsetUsageCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/SuspiciousMemsetUsageCheck.cpp
@@ -15,9 +15,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 void SuspiciousMemsetUsageCheck::registerMatchers(MatchFinder *Finder) {
   // Match the standard memset:
@@ -133,6 +131,4 @@
   }
 }
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/SuspiciousMissingCommaCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/SuspiciousMissingCommaCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/SuspiciousMissingCommaCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/SuspiciousMissingCommaCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 namespace {
 
@@ -125,6 +123,4 @@
        "suspicious string literal, probably missing a comma");
 }
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/SuspiciousReallocUsageCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/SuspiciousReallocUsageCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/SuspiciousReallocUsageCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/SuspiciousReallocUsageCheck.cpp
@@ -103,9 +103,7 @@
 
 } // namespace
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 void SuspiciousReallocUsageCheck::registerMatchers(MatchFinder *Finder) {
   // void *realloc(void *ptr, size_t size);
@@ -158,6 +156,4 @@
       << PtrResultExpr->getSourceRange();
 }
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/SuspiciousSemicolonCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/SuspiciousSemicolonCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/SuspiciousSemicolonCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/SuspiciousSemicolonCheck.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 void SuspiciousSemicolonCheck::registerMatchers(MatchFinder *Finder) {
   Finder->addMatcher(
@@ -73,6 +71,4 @@
       << FixItHint::CreateRemoval(SourceRange(LocStart, LocEnd));
 }
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/SuspiciousStringCompareCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/SuspiciousStringCompareCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/SuspiciousStringCompareCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/SuspiciousStringCompareCheck.cpp
@@ -15,9 +15,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 // Semicolon separated list of known string compare-like functions. The list
 // must ends with a semicolon.
@@ -207,6 +205,4 @@
   }
 }
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/SwappedArgumentsCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/SwappedArgumentsCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/SwappedArgumentsCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/SwappedArgumentsCheck.cpp
@@ -14,9 +14,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 void SwappedArgumentsCheck::registerMatchers(MatchFinder *Finder) {
   Finder->addMatcher(callExpr().bind("call"), this);
@@ -96,6 +94,4 @@
   }
 }
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/TerminatingContinueCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/TerminatingContinueCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/TerminatingContinueCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/TerminatingContinueCheck.cpp
@@ -14,9 +14,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 void TerminatingContinueCheck::registerMatchers(MatchFinder *Finder) {
   const auto DoWithFalse =
@@ -44,6 +42,4 @@
       << tooling::fixit::createReplacement(*ContStmt, "break");
 }
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/ThrowKeywordMissingCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/ThrowKeywordMissingCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/ThrowKeywordMissingCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/ThrowKeywordMissingCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 void ThrowKeywordMissingCheck::registerMatchers(MatchFinder *Finder) {
   auto CtorInitializerList =
@@ -44,6 +42,4 @@
       << TemporaryExpr->getType().getBaseTypeIdentifier()->getName();
 }
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/TooSmallLoopVariableCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/TooSmallLoopVariableCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/TooSmallLoopVariableCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/TooSmallLoopVariableCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 static constexpr llvm::StringLiteral LoopName =
     llvm::StringLiteral("forLoopName");
@@ -175,6 +173,4 @@
         << LoopVarType << UpperBoundType;
 }
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/UncheckedOptionalAccessCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/UncheckedOptionalAccessCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/UncheckedOptionalAccessCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/UncheckedOptionalAccessCheck.cpp
@@ -24,9 +24,7 @@
 #include <optional>
 #include <vector>
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 using ast_matchers::MatchFinder;
 using dataflow::UncheckedOptionalAccessDiagnoser;
 using dataflow::UncheckedOptionalAccessModel;
@@ -101,6 +99,4 @@
       diag(Loc, "unchecked access to optional value");
 }
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/UndefinedMemoryManipulationCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/UndefinedMemoryManipulationCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/UndefinedMemoryManipulationCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/UndefinedMemoryManipulationCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 namespace {
 AST_MATCHER(CXXRecordDecl, isNotTriviallyCopyable) {
@@ -65,6 +63,4 @@
   }
 }
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/UndelegatedConstructorCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/UndelegatedConstructorCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/UndelegatedConstructorCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/UndelegatedConstructorCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 namespace {
 AST_MATCHER_P(Stmt, ignoringTemporaryExpr,
@@ -75,6 +73,4 @@
                          "A temporary object is created here instead");
 }
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/UnhandledExceptionAtNewCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/UnhandledExceptionAtNewCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/UnhandledExceptionAtNewCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/UnhandledExceptionAtNewCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 AST_MATCHER_P(CXXTryStmt, hasHandlerFor,
               ast_matchers::internal::Matcher<QualType>, InnerMatcher) {
@@ -73,6 +71,4 @@
          "missing exception handler for allocation failure at 'new'");
 }
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/UnhandledSelfAssignmentCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/UnhandledSelfAssignmentCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/UnhandledSelfAssignmentCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/UnhandledSelfAssignmentCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 UnhandledSelfAssignmentCheck::UnhandledSelfAssignmentCheck(
     StringRef Name, ClangTidyContext *Context)
@@ -107,6 +105,4 @@
        "operator=() does not handle self-assignment properly");
 }
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/UnusedRaiiCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/UnusedRaiiCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/UnusedRaiiCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/UnusedRaiiCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 namespace {
 AST_MATCHER(CXXRecordDecl, hasNonTrivialDestructor) {
@@ -96,6 +94,4 @@
   }
 }
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/UnusedReturnValueCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/UnusedReturnValueCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/UnusedReturnValueCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/UnusedReturnValueCheck.cpp
@@ -14,9 +14,7 @@
 using namespace clang::ast_matchers;
 using namespace clang::ast_matchers::internal;
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 namespace {
 
@@ -176,6 +174,4 @@
   }
 }
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/UseAfterMoveCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/UseAfterMoveCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/UseAfterMoveCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/UseAfterMoveCheck.cpp
@@ -22,10 +22,7 @@
 using namespace clang::ast_matchers;
 using namespace clang::tidy::utils;
 
-
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 namespace {
 
@@ -467,6 +464,4 @@
     emitDiagnostic(MovingCall, Arg, Use, this, Result.Context);
 }
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/VirtualNearMissCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/VirtualNearMissCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/VirtualNearMissCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/VirtualNearMissCheck.cpp
@@ -14,9 +14,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 namespace {
 AST_MATCHER(CXXMethodDecl, isStatic) { return Node.isStatic(); }
@@ -267,6 +265,4 @@
   }
 }
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/cert/CERTTidyModule.cpp b/clang-tools-extra/clang-tidy/cert/CERTTidyModule.cpp
--- a/clang-tools-extra/clang-tidy/cert/CERTTidyModule.cpp
+++ b/clang-tools-extra/clang-tidy/cert/CERTTidyModule.cpp
@@ -227,8 +227,7 @@
 
 } // namespace
 
-namespace clang {
-namespace tidy {
+namespace clang::tidy {
 namespace cert {
 
 class CERTModule : public ClangTidyModule {
@@ -341,5 +340,4 @@
 // and thus register the CERTModule.
 volatile int CERTModuleAnchorSource = 0;
 
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy
diff --git a/clang-tools-extra/clang-tidy/cert/CommandProcessorCheck.cpp b/clang-tools-extra/clang-tidy/cert/CommandProcessorCheck.cpp
--- a/clang-tools-extra/clang-tidy/cert/CommandProcessorCheck.cpp
+++ b/clang-tools-extra/clang-tidy/cert/CommandProcessorCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace cert {
+namespace clang::tidy::cert {
 
 void CommandProcessorCheck::registerMatchers(MatchFinder *Finder) {
   Finder->addMatcher(
@@ -38,6 +36,4 @@
   diag(E->getExprLoc(), "calling %0 uses a command processor") << Fn;
 }
 
-} // namespace cert
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cert
diff --git a/clang-tools-extra/clang-tidy/cert/DefaultOperatorNewAlignmentCheck.cpp b/clang-tools-extra/clang-tidy/cert/DefaultOperatorNewAlignmentCheck.cpp
--- a/clang-tools-extra/clang-tidy/cert/DefaultOperatorNewAlignmentCheck.cpp
+++ b/clang-tools-extra/clang-tidy/cert/DefaultOperatorNewAlignmentCheck.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace cert {
+namespace clang::tidy::cert {
 
 void DefaultOperatorNewAlignmentCheck::registerMatchers(MatchFinder *Finder) {
   Finder->addMatcher(
@@ -63,6 +61,4 @@
         << (SpecifiedAlignment / CharWidth);
 }
 
-} // namespace cert
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cert
diff --git a/clang-tools-extra/clang-tidy/cert/DontModifyStdNamespaceCheck.cpp b/clang-tools-extra/clang-tidy/cert/DontModifyStdNamespaceCheck.cpp
--- a/clang-tools-extra/clang-tidy/cert/DontModifyStdNamespaceCheck.cpp
+++ b/clang-tools-extra/clang-tidy/cert/DontModifyStdNamespaceCheck.cpp
@@ -37,9 +37,7 @@
 
 } // namespace
 
-namespace clang {
-namespace tidy {
-namespace cert {
+namespace clang::tidy::cert {
 
 void DontModifyStdNamespaceCheck::registerMatchers(MatchFinder *Finder) {
   auto HasStdParent =
@@ -99,9 +97,7 @@
                          .bind("decl"),
                      this);
 }
-} // namespace cert
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cert
 
 static const NamespaceDecl *getTopLevelLexicalNamespaceDecl(const Decl *D) {
   const NamespaceDecl *LastNS = nullptr;
diff --git a/clang-tools-extra/clang-tidy/cert/FloatLoopCounter.cpp b/clang-tools-extra/clang-tidy/cert/FloatLoopCounter.cpp
--- a/clang-tools-extra/clang-tidy/cert/FloatLoopCounter.cpp
+++ b/clang-tools-extra/clang-tidy/cert/FloatLoopCounter.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace cert {
+namespace clang::tidy::cert {
 
 void FloatLoopCounter::registerMatchers(MatchFinder *Finder) {
   Finder->addMatcher(
@@ -29,6 +27,4 @@
                                    "floating-point type");
 }
 
-} // namespace cert
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cert
diff --git a/clang-tools-extra/clang-tidy/cert/LimitedRandomnessCheck.cpp b/clang-tools-extra/clang-tidy/cert/LimitedRandomnessCheck.cpp
--- a/clang-tools-extra/clang-tidy/cert/LimitedRandomnessCheck.cpp
+++ b/clang-tools-extra/clang-tidy/cert/LimitedRandomnessCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace cert {
+namespace clang::tidy::cert {
 
 void LimitedRandomnessCheck::registerMatchers(MatchFinder *Finder) {
   Finder->addMatcher(callExpr(callee(functionDecl(namedDecl(hasName("::rand")),
@@ -32,6 +30,4 @@
   diag(MatchedDecl->getBeginLoc(), "rand() has limited randomness" + Msg);
 }
 
-} // namespace cert
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cert
diff --git a/clang-tools-extra/clang-tidy/cert/MutatingCopyCheck.cpp b/clang-tools-extra/clang-tidy/cert/MutatingCopyCheck.cpp
--- a/clang-tools-extra/clang-tidy/cert/MutatingCopyCheck.cpp
+++ b/clang-tools-extra/clang-tidy/cert/MutatingCopyCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace cert {
+namespace clang::tidy::cert {
 
 static constexpr llvm::StringLiteral SourceDeclName = "ChangedPVD";
 static constexpr llvm::StringLiteral MutatingOperatorName = "MutatingOp";
@@ -71,6 +69,4 @@
     diag(Assignment->getBeginLoc(), "mutating copied object");
 }
 
-} // namespace cert
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cert
diff --git a/clang-tools-extra/clang-tidy/cert/NonTrivialTypesLibcMemoryCallsCheck.cpp b/clang-tools-extra/clang-tidy/cert/NonTrivialTypesLibcMemoryCallsCheck.cpp
--- a/clang-tools-extra/clang-tidy/cert/NonTrivialTypesLibcMemoryCallsCheck.cpp
+++ b/clang-tools-extra/clang-tidy/cert/NonTrivialTypesLibcMemoryCallsCheck.cpp
@@ -19,9 +19,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace cert {
+namespace clang::tidy::cert {
 
 namespace {
 AST_MATCHER(CXXRecordDecl, isTriviallyDefaultConstructible) {
@@ -126,6 +124,4 @@
   }
 }
 
-} // namespace cert
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cert
diff --git a/clang-tools-extra/clang-tidy/cert/PostfixOperatorCheck.cpp b/clang-tools-extra/clang-tidy/cert/PostfixOperatorCheck.cpp
--- a/clang-tools-extra/clang-tidy/cert/PostfixOperatorCheck.cpp
+++ b/clang-tools-extra/clang-tidy/cert/PostfixOperatorCheck.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace cert {
+namespace clang::tidy::cert {
 
 void PostfixOperatorCheck::registerMatchers(MatchFinder *Finder) {
   Finder->addMatcher(functionDecl(hasAnyOverloadedOperatorName("++", "--"),
@@ -79,6 +77,4 @@
     Diag << FixItHint::CreateInsertion(Location, "const ");
 }
 
-} // namespace cert
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cert
diff --git a/clang-tools-extra/clang-tidy/cert/ProperlySeededRandomGeneratorCheck.cpp b/clang-tools-extra/clang-tidy/cert/ProperlySeededRandomGeneratorCheck.cpp
--- a/clang-tools-extra/clang-tidy/cert/ProperlySeededRandomGeneratorCheck.cpp
+++ b/clang-tools-extra/clang-tidy/cert/ProperlySeededRandomGeneratorCheck.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace cert {
+namespace clang::tidy::cert {
 
 ProperlySeededRandomGeneratorCheck::ProperlySeededRandomGeneratorCheck(
     StringRef Name, ClangTidyContext *Context)
@@ -120,6 +118,4 @@
   }
 }
 
-} // namespace cert
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cert
diff --git a/clang-tools-extra/clang-tidy/cert/SetLongJmpCheck.cpp b/clang-tools-extra/clang-tidy/cert/SetLongJmpCheck.cpp
--- a/clang-tools-extra/clang-tidy/cert/SetLongJmpCheck.cpp
+++ b/clang-tools-extra/clang-tidy/cert/SetLongJmpCheck.cpp
@@ -15,9 +15,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace cert {
+namespace clang::tidy::cert {
 
 namespace {
 const char DiagWording[] =
@@ -64,6 +62,4 @@
   diag(E->getExprLoc(), DiagWording) << cast<NamedDecl>(E->getCalleeDecl());
 }
 
-} // namespace cert
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cert
diff --git a/clang-tools-extra/clang-tidy/cert/StaticObjectExceptionCheck.cpp b/clang-tools-extra/clang-tidy/cert/StaticObjectExceptionCheck.cpp
--- a/clang-tools-extra/clang-tidy/cert/StaticObjectExceptionCheck.cpp
+++ b/clang-tools-extra/clang-tidy/cert/StaticObjectExceptionCheck.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace cert {
+namespace clang::tidy::cert {
 
 void StaticObjectExceptionCheck::registerMatchers(MatchFinder *Finder) {
   // Match any static or thread_local variable declaration that has an
@@ -55,6 +53,4 @@
   }
 }
 
-} // namespace cert
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cert
diff --git a/clang-tools-extra/clang-tidy/cert/StrToNumCheck.cpp b/clang-tools-extra/clang-tidy/cert/StrToNumCheck.cpp
--- a/clang-tools-extra/clang-tidy/cert/StrToNumCheck.cpp
+++ b/clang-tools-extra/clang-tidy/cert/StrToNumCheck.cpp
@@ -15,9 +15,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace cert {
+namespace clang::tidy::cert {
 
 void StrToNumCheck::registerMatchers(MatchFinder *Finder) {
   // Match any function call to the C standard library string conversion
@@ -229,6 +227,4 @@
       << classifyReplacement(Conversion);
 }
 
-} // namespace cert
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cert
diff --git a/clang-tools-extra/clang-tidy/cert/ThrownExceptionTypeCheck.cpp b/clang-tools-extra/clang-tidy/cert/ThrownExceptionTypeCheck.cpp
--- a/clang-tools-extra/clang-tidy/cert/ThrownExceptionTypeCheck.cpp
+++ b/clang-tools-extra/clang-tidy/cert/ThrownExceptionTypeCheck.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace cert {
+namespace clang::tidy::cert {
 
 void ThrownExceptionTypeCheck::registerMatchers(MatchFinder *Finder) {
   Finder->addMatcher(
@@ -34,6 +32,4 @@
        "thrown exception type is not nothrow copy constructible");
 }
 
-} // namespace cert
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cert
diff --git a/clang-tools-extra/clang-tidy/cert/VariadicFunctionDefCheck.cpp b/clang-tools-extra/clang-tidy/cert/VariadicFunctionDefCheck.cpp
--- a/clang-tools-extra/clang-tidy/cert/VariadicFunctionDefCheck.cpp
+++ b/clang-tools-extra/clang-tidy/cert/VariadicFunctionDefCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace cert {
+namespace clang::tidy::cert {
 
 void VariadicFunctionDefCheck::registerMatchers(MatchFinder *Finder) {
   // We only care about function *definitions* that are variadic, and do not
@@ -33,6 +31,4 @@
        "parameter pack or currying instead");
 }
 
-} // namespace cert
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cert
diff --git a/clang-tools-extra/clang-tidy/concurrency/ConcurrencyTidyModule.cpp b/clang-tools-extra/clang-tidy/concurrency/ConcurrencyTidyModule.cpp
--- a/clang-tools-extra/clang-tidy/concurrency/ConcurrencyTidyModule.cpp
+++ b/clang-tools-extra/clang-tidy/concurrency/ConcurrencyTidyModule.cpp
@@ -12,8 +12,7 @@
 #include "MtUnsafeCheck.h"
 #include "ThreadCanceltypeAsynchronousCheck.h"
 
-namespace clang {
-namespace tidy {
+namespace clang::tidy {
 namespace concurrency {
 
 class ConcurrencyModule : public ClangTidyModule {
@@ -36,5 +35,4 @@
 // and thus register the ConcurrencyModule.
 volatile int ConcurrencyModuleAnchorSource = 0;
 
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy
diff --git a/clang-tools-extra/clang-tidy/concurrency/MtUnsafeCheck.cpp b/clang-tools-extra/clang-tidy/concurrency/MtUnsafeCheck.cpp
--- a/clang-tools-extra/clang-tidy/concurrency/MtUnsafeCheck.cpp
+++ b/clang-tools-extra/clang-tidy/concurrency/MtUnsafeCheck.cpp
@@ -258,8 +258,7 @@
     "::wctomb",
 };
 
-namespace clang {
-namespace tidy {
+namespace clang::tidy {
 
 template <> struct OptionEnumMapping<concurrency::MtUnsafeCheck::FunctionSet> {
   static llvm::ArrayRef<
@@ -312,5 +311,4 @@
 }
 
 } // namespace concurrency
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy
diff --git a/clang-tools-extra/clang-tidy/concurrency/ThreadCanceltypeAsynchronousCheck.cpp b/clang-tools-extra/clang-tidy/concurrency/ThreadCanceltypeAsynchronousCheck.cpp
--- a/clang-tools-extra/clang-tidy/concurrency/ThreadCanceltypeAsynchronousCheck.cpp
+++ b/clang-tools-extra/clang-tidy/concurrency/ThreadCanceltypeAsynchronousCheck.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace concurrency {
+namespace clang::tidy::concurrency {
 
 void ThreadCanceltypeAsynchronousCheck::registerMatchers(MatchFinder *Finder) {
   Finder->addMatcher(
@@ -34,6 +32,4 @@
                                    "be 'PTHREAD_CANCEL_ASYNCHRONOUS'");
 }
 
-} // namespace concurrency
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::concurrency
diff --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/AvoidConstOrRefDataMembersCheck.cpp b/clang-tools-extra/clang-tidy/cppcoreguidelines/AvoidConstOrRefDataMembersCheck.cpp
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/AvoidConstOrRefDataMembersCheck.cpp
+++ b/clang-tools-extra/clang-tidy/cppcoreguidelines/AvoidConstOrRefDataMembersCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace cppcoreguidelines {
+namespace clang::tidy::cppcoreguidelines {
 namespace {
 
 AST_MATCHER(FieldDecl, isMemberOfLambda) {
@@ -44,6 +42,4 @@
         << MatchedDecl << MatchedDecl->getType();
 }
 
-} // namespace cppcoreguidelines
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cppcoreguidelines
diff --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/AvoidDoWhileCheck.cpp b/clang-tools-extra/clang-tidy/cppcoreguidelines/AvoidDoWhileCheck.cpp
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/AvoidDoWhileCheck.cpp
+++ b/clang-tools-extra/clang-tidy/cppcoreguidelines/AvoidDoWhileCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace cppcoreguidelines {
+namespace clang::tidy::cppcoreguidelines {
 
 AvoidDoWhileCheck::AvoidDoWhileCheck(StringRef Name, ClangTidyContext *Context)
     : ClangTidyCheck(Name, Context),
@@ -36,6 +34,4 @@
   }
 }
 
-} // namespace cppcoreguidelines
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cppcoreguidelines
diff --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/AvoidGotoCheck.cpp b/clang-tools-extra/clang-tidy/cppcoreguidelines/AvoidGotoCheck.cpp
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/AvoidGotoCheck.cpp
+++ b/clang-tools-extra/clang-tidy/cppcoreguidelines/AvoidGotoCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace cppcoreguidelines {
+namespace clang::tidy::cppcoreguidelines {
 
 namespace {
 AST_MATCHER(GotoStmt, isForwardJumping) {
@@ -46,6 +44,4 @@
   diag(Goto->getLabel()->getBeginLoc(), "label defined here",
        DiagnosticIDs::Note);
 }
-} // namespace cppcoreguidelines
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cppcoreguidelines
diff --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/AvoidNonConstGlobalVariablesCheck.cpp b/clang-tools-extra/clang-tidy/cppcoreguidelines/AvoidNonConstGlobalVariablesCheck.cpp
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/AvoidNonConstGlobalVariablesCheck.cpp
+++ b/clang-tools-extra/clang-tidy/cppcoreguidelines/AvoidNonConstGlobalVariablesCheck.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace cppcoreguidelines {
+namespace clang::tidy::cppcoreguidelines {
 
 namespace {
 AST_MATCHER(VarDecl, isLocalVarDecl) { return Node.isLocalVarDecl(); }
@@ -66,6 +64,4 @@
   }
 }
 
-} // namespace cppcoreguidelines
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cppcoreguidelines
diff --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/AvoidReferenceCoroutineParametersCheck.cpp b/clang-tools-extra/clang-tidy/cppcoreguidelines/AvoidReferenceCoroutineParametersCheck.cpp
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/AvoidReferenceCoroutineParametersCheck.cpp
+++ b/clang-tools-extra/clang-tidy/cppcoreguidelines/AvoidReferenceCoroutineParametersCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace cppcoreguidelines {
+namespace clang::tidy::cppcoreguidelines {
 
 void AvoidReferenceCoroutineParametersCheck::registerMatchers(
     MatchFinder *Finder) {
@@ -33,6 +31,4 @@
   }
 }
 
-} // namespace cppcoreguidelines
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cppcoreguidelines
diff --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/CppCoreGuidelinesTidyModule.cpp b/clang-tools-extra/clang-tidy/cppcoreguidelines/CppCoreGuidelinesTidyModule.cpp
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/CppCoreGuidelinesTidyModule.cpp
+++ b/clang-tools-extra/clang-tidy/cppcoreguidelines/CppCoreGuidelinesTidyModule.cpp
@@ -40,8 +40,7 @@
 #include "SpecialMemberFunctionsCheck.h"
 #include "VirtualClassDestructorCheck.h"
 
-namespace clang {
-namespace tidy {
+namespace clang::tidy {
 namespace cppcoreguidelines {
 
 /// A module containing checks of the C++ Core Guidelines
@@ -129,5 +128,4 @@
 // and thus register the CppCoreGuidelinesModule.
 volatile int CppCoreGuidelinesModuleAnchorSource = 0;
 
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy
diff --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/InitVariablesCheck.cpp b/clang-tools-extra/clang-tidy/cppcoreguidelines/InitVariablesCheck.cpp
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/InitVariablesCheck.cpp
+++ b/clang-tools-extra/clang-tidy/cppcoreguidelines/InitVariablesCheck.cpp
@@ -16,9 +16,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace cppcoreguidelines {
+namespace clang::tidy::cppcoreguidelines {
 
 namespace {
 AST_MATCHER(VarDecl, isLocalVarDecl) { return Node.isLocalVarDecl(); }
@@ -114,6 +112,4 @@
     }
   }
 }
-} // namespace cppcoreguidelines
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cppcoreguidelines
diff --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/InterfacesGlobalInitCheck.cpp b/clang-tools-extra/clang-tidy/cppcoreguidelines/InterfacesGlobalInitCheck.cpp
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/InterfacesGlobalInitCheck.cpp
+++ b/clang-tools-extra/clang-tidy/cppcoreguidelines/InterfacesGlobalInitCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace cppcoreguidelines {
+namespace clang::tidy::cppcoreguidelines {
 
 void InterfacesGlobalInitCheck::registerMatchers(MatchFinder *Finder) {
   const auto GlobalVarDecl =
@@ -54,6 +52,4 @@
       << Referencee;
 }
 
-} // namespace cppcoreguidelines
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cppcoreguidelines
diff --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/MacroUsageCheck.cpp b/clang-tools-extra/clang-tidy/cppcoreguidelines/MacroUsageCheck.cpp
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/MacroUsageCheck.cpp
+++ b/clang-tools-extra/clang-tidy/cppcoreguidelines/MacroUsageCheck.cpp
@@ -16,9 +16,7 @@
 #include <cctype>
 #include <functional>
 
-namespace clang {
-namespace tidy {
-namespace cppcoreguidelines {
+namespace clang::tidy::cppcoreguidelines {
 
 static bool isCapsOnly(StringRef Name) {
   return llvm::all_of(Name, [](const char C) {
@@ -106,6 +104,4 @@
       << MacroName;
 }
 
-} // namespace cppcoreguidelines
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cppcoreguidelines
diff --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/NarrowingConversionsCheck.cpp b/clang-tools-extra/clang-tidy/cppcoreguidelines/NarrowingConversionsCheck.cpp
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/NarrowingConversionsCheck.cpp
+++ b/clang-tools-extra/clang-tidy/cppcoreguidelines/NarrowingConversionsCheck.cpp
@@ -21,9 +21,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace cppcoreguidelines {
+namespace clang::tidy::cppcoreguidelines {
 
 NarrowingConversionsCheck::NarrowingConversionsCheck(StringRef Name,
                                                      ClangTidyContext *Context)
@@ -594,6 +592,4 @@
     return handleImplicitCast(*Result.Context, *Cast);
   llvm_unreachable("must be binary operator or cast expression");
 }
-} // namespace cppcoreguidelines
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cppcoreguidelines
diff --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/NoMallocCheck.cpp b/clang-tools-extra/clang-tidy/cppcoreguidelines/NoMallocCheck.cpp
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/NoMallocCheck.cpp
+++ b/clang-tools-extra/clang-tidy/cppcoreguidelines/NoMallocCheck.cpp
@@ -18,9 +18,7 @@
 using namespace clang::ast_matchers;
 using namespace clang::ast_matchers::internal;
 
-namespace clang {
-namespace tidy {
-namespace cppcoreguidelines {
+namespace clang::tidy::cppcoreguidelines {
 
 void NoMallocCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {
   Options.store(Opts, "Allocations", AllocList);
@@ -67,6 +65,4 @@
       << Recommendation << SourceRange(Call->getBeginLoc(), Call->getEndLoc());
 }
 
-} // namespace cppcoreguidelines
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cppcoreguidelines
diff --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/OwningMemoryCheck.cpp b/clang-tools-extra/clang-tidy/cppcoreguidelines/OwningMemoryCheck.cpp
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/OwningMemoryCheck.cpp
+++ b/clang-tools-extra/clang-tidy/cppcoreguidelines/OwningMemoryCheck.cpp
@@ -17,9 +17,7 @@
 using namespace clang::ast_matchers;
 using namespace clang::ast_matchers::internal;
 
-namespace clang {
-namespace tidy {
-namespace cppcoreguidelines {
+namespace clang::tidy::cppcoreguidelines {
 
 void OwningMemoryCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {
   Options.store(Opts, "LegacyResourceProducers", LegacyResourceProducers);
@@ -370,6 +368,4 @@
   return false;
 }
 
-} // namespace cppcoreguidelines
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cppcoreguidelines
diff --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/PreferMemberInitializerCheck.cpp b/clang-tools-extra/clang-tidy/cppcoreguidelines/PreferMemberInitializerCheck.cpp
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/PreferMemberInitializerCheck.cpp
+++ b/clang-tools-extra/clang-tidy/cppcoreguidelines/PreferMemberInitializerCheck.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace cppcoreguidelines {
+namespace clang::tidy::cppcoreguidelines {
 
 static bool isControlStatement(const Stmt *S) {
   return isa<IfStmt, SwitchStmt, ForStmt, WhileStmt, DoStmt, ReturnStmt,
@@ -315,6 +313,4 @@
   }
 }
 
-} // namespace cppcoreguidelines
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cppcoreguidelines
diff --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/ProBoundsArrayToPointerDecayCheck.cpp b/clang-tools-extra/clang-tidy/cppcoreguidelines/ProBoundsArrayToPointerDecayCheck.cpp
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/ProBoundsArrayToPointerDecayCheck.cpp
+++ b/clang-tools-extra/clang-tidy/cppcoreguidelines/ProBoundsArrayToPointerDecayCheck.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace cppcoreguidelines {
+namespace clang::tidy::cppcoreguidelines {
 
 namespace {
 AST_MATCHER_P(CXXForRangeStmt, hasRangeBeginEndStmt,
@@ -79,6 +77,4 @@
                                   "an explicit cast instead");
 }
 
-} // namespace cppcoreguidelines
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cppcoreguidelines
diff --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/ProBoundsConstantArrayIndexCheck.cpp b/clang-tools-extra/clang-tidy/cppcoreguidelines/ProBoundsConstantArrayIndexCheck.cpp
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/ProBoundsConstantArrayIndexCheck.cpp
+++ b/clang-tools-extra/clang-tidy/cppcoreguidelines/ProBoundsConstantArrayIndexCheck.cpp
@@ -15,9 +15,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace cppcoreguidelines {
+namespace clang::tidy::cppcoreguidelines {
 
 ProBoundsConstantArrayIndexCheck::ProBoundsConstantArrayIndexCheck(
     StringRef Name, ClangTidyContext *Context)
@@ -129,6 +127,4 @@
   }
 }
 
-} // namespace cppcoreguidelines
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cppcoreguidelines
diff --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/ProBoundsPointerArithmeticCheck.cpp b/clang-tools-extra/clang-tidy/cppcoreguidelines/ProBoundsPointerArithmeticCheck.cpp
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/ProBoundsPointerArithmeticCheck.cpp
+++ b/clang-tools-extra/clang-tidy/cppcoreguidelines/ProBoundsPointerArithmeticCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace cppcoreguidelines {
+namespace clang::tidy::cppcoreguidelines {
 
 void ProBoundsPointerArithmeticCheck::registerMatchers(MatchFinder *Finder) {
   if (!getLangOpts().CPlusPlus)
@@ -56,6 +54,4 @@
   diag(MatchedExpr->getExprLoc(), "do not use pointer arithmetic");
 }
 
-} // namespace cppcoreguidelines
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cppcoreguidelines
diff --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeConstCastCheck.cpp b/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeConstCastCheck.cpp
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeConstCastCheck.cpp
+++ b/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeConstCastCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace cppcoreguidelines {
+namespace clang::tidy::cppcoreguidelines {
 
 void ProTypeConstCastCheck::registerMatchers(MatchFinder *Finder) {
   Finder->addMatcher(cxxConstCastExpr().bind("cast"), this);
@@ -25,6 +23,4 @@
   diag(MatchedCast->getOperatorLoc(), "do not use const_cast");
 }
 
-} // namespace cppcoreguidelines
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cppcoreguidelines
diff --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeCstyleCastCheck.cpp b/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeCstyleCastCheck.cpp
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeCstyleCastCheck.cpp
+++ b/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeCstyleCastCheck.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace cppcoreguidelines {
+namespace clang::tidy::cppcoreguidelines {
 
 static bool needsConstCast(QualType SourceType, QualType DestType) {
   SourceType = SourceType.getNonReferenceType();
@@ -99,6 +97,4 @@
   }
 }
 
-} // namespace cppcoreguidelines
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cppcoreguidelines
diff --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeMemberInitCheck.cpp b/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeMemberInitCheck.cpp
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeMemberInitCheck.cpp
+++ b/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeMemberInitCheck.cpp
@@ -20,9 +20,7 @@
 using llvm::SmallPtrSet;
 using llvm::SmallPtrSetImpl;
 
-namespace clang {
-namespace tidy {
-namespace cppcoreguidelines {
+namespace clang::tidy::cppcoreguidelines {
 
 namespace {
 
@@ -579,6 +577,4 @@
       Context.getLangOpts().CPlusPlus11 ? "{}" : " = {}");
 }
 
-} // namespace cppcoreguidelines
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cppcoreguidelines
diff --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeReinterpretCastCheck.cpp b/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeReinterpretCastCheck.cpp
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeReinterpretCastCheck.cpp
+++ b/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeReinterpretCastCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace cppcoreguidelines {
+namespace clang::tidy::cppcoreguidelines {
 
 void ProTypeReinterpretCastCheck::registerMatchers(MatchFinder *Finder) {
   Finder->addMatcher(cxxReinterpretCastExpr().bind("cast"), this);
@@ -27,6 +25,4 @@
   diag(MatchedCast->getOperatorLoc(), "do not use reinterpret_cast");
 }
 
-} // namespace cppcoreguidelines
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cppcoreguidelines
diff --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeStaticCastDowncastCheck.cpp b/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeStaticCastDowncastCheck.cpp
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeStaticCastDowncastCheck.cpp
+++ b/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeStaticCastDowncastCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace cppcoreguidelines {
+namespace clang::tidy::cppcoreguidelines {
 
 void ProTypeStaticCastDowncastCheck::registerMatchers(MatchFinder *Finder) {
   Finder->addMatcher(
@@ -46,6 +44,4 @@
          "do not use static_cast to downcast from a base to a derived class");
 }
 
-} // namespace cppcoreguidelines
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cppcoreguidelines
diff --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeUnionAccessCheck.cpp b/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeUnionAccessCheck.cpp
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeUnionAccessCheck.cpp
+++ b/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeUnionAccessCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace cppcoreguidelines {
+namespace clang::tidy::cppcoreguidelines {
 
 void ProTypeUnionAccessCheck::registerMatchers(MatchFinder *Finder) {
   Finder->addMatcher(
@@ -29,6 +27,4 @@
        "do not access members of unions; use (boost::)variant instead");
 }
 
-} // namespace cppcoreguidelines
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cppcoreguidelines
diff --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeVarargCheck.cpp b/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeVarargCheck.cpp
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeVarargCheck.cpp
+++ b/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeVarargCheck.cpp
@@ -17,9 +17,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace cppcoreguidelines {
+namespace clang::tidy::cppcoreguidelines {
 
 const internal::VariadicDynCastAllOfMatcher<Stmt, VAArgExpr> VAArgExpr;
 
@@ -193,6 +191,4 @@
   }
 }
 
-} // namespace cppcoreguidelines
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cppcoreguidelines
diff --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/SlicingCheck.cpp b/clang-tools-extra/clang-tidy/cppcoreguidelines/SlicingCheck.cpp
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/SlicingCheck.cpp
+++ b/clang-tools-extra/clang-tidy/cppcoreguidelines/SlicingCheck.cpp
@@ -14,9 +14,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace cppcoreguidelines {
+namespace clang::tidy::cppcoreguidelines {
 
 void SlicingCheck::registerMatchers(MatchFinder *Finder) {
   // When we see:
@@ -131,6 +129,4 @@
   }
 }
 
-} // namespace cppcoreguidelines
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cppcoreguidelines
diff --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/SpecialMemberFunctionsCheck.cpp b/clang-tools-extra/clang-tidy/cppcoreguidelines/SpecialMemberFunctionsCheck.cpp
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/SpecialMemberFunctionsCheck.cpp
+++ b/clang-tools-extra/clang-tidy/cppcoreguidelines/SpecialMemberFunctionsCheck.cpp
@@ -17,9 +17,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace cppcoreguidelines {
+namespace clang::tidy::cppcoreguidelines {
 
 SpecialMemberFunctionsCheck::SpecialMemberFunctionsCheck(
     StringRef Name, ClangTidyContext *Context)
@@ -199,6 +197,4 @@
   }
 }
 
-} // namespace cppcoreguidelines
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cppcoreguidelines
diff --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/VirtualClassDestructorCheck.cpp b/clang-tools-extra/clang-tidy/cppcoreguidelines/VirtualClassDestructorCheck.cpp
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/VirtualClassDestructorCheck.cpp
+++ b/clang-tools-extra/clang-tidy/cppcoreguidelines/VirtualClassDestructorCheck.cpp
@@ -16,9 +16,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace cppcoreguidelines {
+namespace clang::tidy::cppcoreguidelines {
 
 AST_MATCHER(CXXRecordDecl, hasPublicVirtualOrProtectedNonVirtualDestructor) {
   // We need to call Node.getDestructor() instead of matching a
@@ -218,6 +216,4 @@
       << ProtectedAndVirtual << Fix;
 }
 
-} // namespace cppcoreguidelines
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cppcoreguidelines
diff --git a/clang-tools-extra/clang-tidy/darwin/AvoidSpinlockCheck.cpp b/clang-tools-extra/clang-tidy/darwin/AvoidSpinlockCheck.cpp
--- a/clang-tools-extra/clang-tidy/darwin/AvoidSpinlockCheck.cpp
+++ b/clang-tools-extra/clang-tidy/darwin/AvoidSpinlockCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace darwin {
+namespace clang::tidy::darwin {
 
 void AvoidSpinlockCheck::registerMatchers(MatchFinder *Finder) {
   Finder->addMatcher(
@@ -31,6 +29,4 @@
        "deprecated OSSpinLock");
 }
 
-}  // namespace darwin
-}  // namespace tidy
-}  // namespace clang
+} // namespace clang::tidy::darwin
diff --git a/clang-tools-extra/clang-tidy/darwin/DarwinTidyModule.cpp b/clang-tools-extra/clang-tidy/darwin/DarwinTidyModule.cpp
--- a/clang-tools-extra/clang-tidy/darwin/DarwinTidyModule.cpp
+++ b/clang-tools-extra/clang-tidy/darwin/DarwinTidyModule.cpp
@@ -12,8 +12,7 @@
 #include "AvoidSpinlockCheck.h"
 #include "DispatchOnceNonstaticCheck.h"
 
-namespace clang {
-namespace tidy {
+namespace clang::tidy {
 namespace darwin {
 
 class DarwinModule : public ClangTidyModule {
@@ -36,5 +35,4 @@
 // and thus register the DarwinModule.
 volatile int DarwinModuleAnchorSource = 0;
 
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy
diff --git a/clang-tools-extra/clang-tidy/darwin/DispatchOnceNonstaticCheck.cpp b/clang-tools-extra/clang-tidy/darwin/DispatchOnceNonstaticCheck.cpp
--- a/clang-tools-extra/clang-tidy/darwin/DispatchOnceNonstaticCheck.cpp
+++ b/clang-tools-extra/clang-tidy/darwin/DispatchOnceNonstaticCheck.cpp
@@ -16,9 +16,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace darwin {
+namespace clang::tidy::darwin {
 
 void DispatchOnceNonstaticCheck::registerMatchers(MatchFinder *Finder) {
   // Find variables without static or global storage. VarDecls do not include
@@ -57,6 +55,4 @@
   }
 }
 
-} // namespace darwin
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::darwin
diff --git a/clang-tools-extra/clang-tidy/fuchsia/DefaultArgumentsCallsCheck.cpp b/clang-tools-extra/clang-tidy/fuchsia/DefaultArgumentsCallsCheck.cpp
--- a/clang-tools-extra/clang-tidy/fuchsia/DefaultArgumentsCallsCheck.cpp
+++ b/clang-tools-extra/clang-tidy/fuchsia/DefaultArgumentsCallsCheck.cpp
@@ -10,9 +10,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace fuchsia {
+namespace clang::tidy::fuchsia {
 
 void DefaultArgumentsCallsCheck::registerMatchers(MatchFinder *Finder) {
   // Calling a function which uses default arguments is disallowed.
@@ -30,6 +28,4 @@
        DiagnosticIDs::Note);
 }
 
-} // namespace fuchsia
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::fuchsia
diff --git a/clang-tools-extra/clang-tidy/fuchsia/DefaultArgumentsDeclarationsCheck.cpp b/clang-tools-extra/clang-tidy/fuchsia/DefaultArgumentsDeclarationsCheck.cpp
--- a/clang-tools-extra/clang-tidy/fuchsia/DefaultArgumentsDeclarationsCheck.cpp
+++ b/clang-tools-extra/clang-tidy/fuchsia/DefaultArgumentsDeclarationsCheck.cpp
@@ -11,9 +11,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace fuchsia {
+namespace clang::tidy::fuchsia {
 
 void DefaultArgumentsDeclarationsCheck::registerMatchers(MatchFinder *Finder) {
   // Declaring default parameters is disallowed.
@@ -50,6 +48,4 @@
       << D << FixItHint::CreateRemoval(RemovalRange);
 }
 
-} // namespace fuchsia
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::fuchsia
diff --git a/clang-tools-extra/clang-tidy/fuchsia/FuchsiaTidyModule.cpp b/clang-tools-extra/clang-tidy/fuchsia/FuchsiaTidyModule.cpp
--- a/clang-tools-extra/clang-tidy/fuchsia/FuchsiaTidyModule.cpp
+++ b/clang-tools-extra/clang-tidy/fuchsia/FuchsiaTidyModule.cpp
@@ -20,8 +20,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
+namespace clang::tidy {
 namespace fuchsia {
 
 /// This module is for Fuchsia-specific checks.
@@ -55,5 +54,4 @@
 // and thus register the FuchsiaModule.
 volatile int FuchsiaModuleAnchorSource = 0;
 
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy
diff --git a/clang-tools-extra/clang-tidy/fuchsia/MultipleInheritanceCheck.cpp b/clang-tools-extra/clang-tidy/fuchsia/MultipleInheritanceCheck.cpp
--- a/clang-tools-extra/clang-tidy/fuchsia/MultipleInheritanceCheck.cpp
+++ b/clang-tools-extra/clang-tidy/fuchsia/MultipleInheritanceCheck.cpp
@@ -13,9 +13,7 @@
 using namespace clang;
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace fuchsia {
+namespace clang::tidy::fuchsia {
 
 namespace {
 AST_MATCHER(CXXRecordDecl, hasBases) {
@@ -122,6 +120,4 @@
   }
 }
 
-}  // namespace fuchsia
-}  // namespace tidy
-}  // namespace clang
+} // namespace clang::tidy::fuchsia
diff --git a/clang-tools-extra/clang-tidy/fuchsia/OverloadedOperatorCheck.cpp b/clang-tools-extra/clang-tidy/fuchsia/OverloadedOperatorCheck.cpp
--- a/clang-tools-extra/clang-tidy/fuchsia/OverloadedOperatorCheck.cpp
+++ b/clang-tools-extra/clang-tidy/fuchsia/OverloadedOperatorCheck.cpp
@@ -10,9 +10,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace fuchsia {
+namespace clang::tidy::fuchsia {
 
 namespace {
 AST_MATCHER(FunctionDecl, isFuchsiaOverloadedOperator) {
@@ -41,6 +39,4 @@
     diag(Loc, "overloading %0 is disallowed") << D;
 }
 
-} // namespace fuchsia
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::fuchsia
diff --git a/clang-tools-extra/clang-tidy/fuchsia/StaticallyConstructedObjectsCheck.cpp b/clang-tools-extra/clang-tidy/fuchsia/StaticallyConstructedObjectsCheck.cpp
--- a/clang-tools-extra/clang-tidy/fuchsia/StaticallyConstructedObjectsCheck.cpp
+++ b/clang-tools-extra/clang-tidy/fuchsia/StaticallyConstructedObjectsCheck.cpp
@@ -10,9 +10,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace fuchsia {
+namespace clang::tidy::fuchsia {
 
 namespace {
 AST_MATCHER(Expr, isConstantInitializer) {
@@ -50,6 +48,4 @@
                            "constexpr constructor instead");
 }
 
-} // namespace fuchsia
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::fuchsia
diff --git a/clang-tools-extra/clang-tidy/fuchsia/TrailingReturnCheck.cpp b/clang-tools-extra/clang-tidy/fuchsia/TrailingReturnCheck.cpp
--- a/clang-tools-extra/clang-tidy/fuchsia/TrailingReturnCheck.cpp
+++ b/clang-tools-extra/clang-tidy/fuchsia/TrailingReturnCheck.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace fuchsia {
+namespace clang::tidy::fuchsia {
 
 void TrailingReturnCheck::registerMatchers(MatchFinder *Finder) {
   // Functions that have trailing returns are disallowed, except for those
@@ -36,6 +34,4 @@
          "a trailing return type is disallowed for this function declaration");
 }
 
-} // namespace fuchsia
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::fuchsia
diff --git a/clang-tools-extra/clang-tidy/fuchsia/VirtualInheritanceCheck.cpp b/clang-tools-extra/clang-tidy/fuchsia/VirtualInheritanceCheck.cpp
--- a/clang-tools-extra/clang-tidy/fuchsia/VirtualInheritanceCheck.cpp
+++ b/clang-tools-extra/clang-tidy/fuchsia/VirtualInheritanceCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace fuchsia {
+namespace clang::tidy::fuchsia {
 
 namespace {
 AST_MATCHER(CXXRecordDecl, hasDirectVirtualBaseClass) {
@@ -37,6 +35,4 @@
     diag(D->getBeginLoc(), "direct virtual inheritance is disallowed");
 }
 
-}  // namespace fuchsia
-}  // namespace tidy
-}  // namespace clang
+} // namespace clang::tidy::fuchsia
diff --git a/clang-tools-extra/clang-tidy/google/AvoidCStyleCastsCheck.cpp b/clang-tools-extra/clang-tidy/google/AvoidCStyleCastsCheck.cpp
--- a/clang-tools-extra/clang-tidy/google/AvoidCStyleCastsCheck.cpp
+++ b/clang-tools-extra/clang-tidy/google/AvoidCStyleCastsCheck.cpp
@@ -14,10 +14,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace google {
-namespace readability {
+namespace clang::tidy::google::readability {
 
 void AvoidCStyleCastsCheck::registerMatchers(
     ast_matchers::MatchFinder *Finder) {
@@ -258,7 +255,4 @@
   Diag << "static_cast/const_cast/reinterpret_cast";
 }
 
-} // namespace readability
-} // namespace google
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::google::readability
diff --git a/clang-tools-extra/clang-tidy/google/AvoidNSObjectNewCheck.cpp b/clang-tools-extra/clang-tidy/google/AvoidNSObjectNewCheck.cpp
--- a/clang-tools-extra/clang-tidy/google/AvoidNSObjectNewCheck.cpp
+++ b/clang-tools-extra/clang-tidy/google/AvoidNSObjectNewCheck.cpp
@@ -19,10 +19,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace google {
-namespace objc {
+namespace clang::tidy::google::objc {
 
 static bool isMessageExpressionInsideMacro(const ObjCMessageExpr *Expr) {
   SourceLocation ReceiverLocation = Expr->getReceiverRange().getBegin();
@@ -123,7 +120,4 @@
   }
 }
 
-} // namespace objc
-} // namespace google
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::google::objc
diff --git a/clang-tools-extra/clang-tidy/google/AvoidThrowingObjCExceptionCheck.cpp b/clang-tools-extra/clang-tidy/google/AvoidThrowingObjCExceptionCheck.cpp
--- a/clang-tools-extra/clang-tidy/google/AvoidThrowingObjCExceptionCheck.cpp
+++ b/clang-tools-extra/clang-tidy/google/AvoidThrowingObjCExceptionCheck.cpp
@@ -12,10 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace google {
-namespace objc {
+namespace clang::tidy::google::objc {
 
 void AvoidThrowingObjCExceptionCheck::registerMatchers(MatchFinder *Finder) {
 
@@ -57,7 +54,4 @@
        "Objective-C errors");
 }
 
-}  // namespace objc
-}  // namespace google
-}  // namespace tidy
-}  // namespace clang
+} // namespace clang::tidy::google::objc
diff --git a/clang-tools-extra/clang-tidy/google/AvoidUnderscoreInGoogletestNameCheck.cpp b/clang-tools-extra/clang-tidy/google/AvoidUnderscoreInGoogletestNameCheck.cpp
--- a/clang-tools-extra/clang-tidy/google/AvoidUnderscoreInGoogletestNameCheck.cpp
+++ b/clang-tools-extra/clang-tidy/google/AvoidUnderscoreInGoogletestNameCheck.cpp
@@ -16,10 +16,7 @@
 #include "clang/Lex/PPCallbacks.h"
 #include "clang/Lex/Preprocessor.h"
 
-namespace clang {
-namespace tidy {
-namespace google {
-namespace readability {
+namespace clang::tidy::google::readability {
 
 constexpr llvm::StringLiteral KDisabledTestPrefix = "DISABLED_";
 
@@ -84,7 +81,4 @@
       std::make_unique<AvoidUnderscoreInGoogletestNameCallback>(PP, this));
 }
 
-} // namespace readability
-} // namespace google
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::google::readability
diff --git a/clang-tools-extra/clang-tidy/google/DefaultArgumentsCheck.cpp b/clang-tools-extra/clang-tidy/google/DefaultArgumentsCheck.cpp
--- a/clang-tools-extra/clang-tidy/google/DefaultArgumentsCheck.cpp
+++ b/clang-tools-extra/clang-tidy/google/DefaultArgumentsCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace google {
+namespace clang::tidy::google {
 
 void DefaultArgumentsCheck::registerMatchers(MatchFinder *Finder) {
   Finder->addMatcher(
@@ -30,6 +28,4 @@
        "default arguments on virtual or override methods are prohibited");
 }
 
-} // namespace google
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::google
diff --git a/clang-tools-extra/clang-tidy/google/ExplicitConstructorCheck.cpp b/clang-tools-extra/clang-tidy/google/ExplicitConstructorCheck.cpp
--- a/clang-tools-extra/clang-tidy/google/ExplicitConstructorCheck.cpp
+++ b/clang-tools-extra/clang-tidy/google/ExplicitConstructorCheck.cpp
@@ -14,9 +14,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace google {
+namespace clang::tidy::google {
 
 void ExplicitConstructorCheck::registerMatchers(MatchFinder *Finder) {
   Finder->addMatcher(
@@ -146,6 +144,4 @@
       << FixItHint::CreateInsertion(Loc, "explicit ");
 }
 
-} // namespace google
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::google
diff --git a/clang-tools-extra/clang-tidy/google/ExplicitMakePairCheck.cpp b/clang-tools-extra/clang-tidy/google/ExplicitMakePairCheck.cpp
--- a/clang-tools-extra/clang-tidy/google/ExplicitMakePairCheck.cpp
+++ b/clang-tools-extra/clang-tidy/google/ExplicitMakePairCheck.cpp
@@ -20,9 +20,7 @@
 }
 } // namespace
 
-namespace tidy {
-namespace google {
-namespace build {
+namespace tidy::google::build {
 
 void ExplicitMakePairCheck::registerMatchers(
     ast_matchers::MatchFinder *Finder) {
@@ -66,7 +64,5 @@
   }
 }
 
-} // namespace build
-} // namespace google
-} // namespace tidy
+} // namespace tidy::google::build
 } // namespace clang
diff --git a/clang-tools-extra/clang-tidy/google/FunctionNamingCheck.cpp b/clang-tools-extra/clang-tidy/google/FunctionNamingCheck.cpp
--- a/clang-tools-extra/clang-tidy/google/FunctionNamingCheck.cpp
+++ b/clang-tools-extra/clang-tidy/google/FunctionNamingCheck.cpp
@@ -13,10 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace google {
-namespace objc {
+namespace clang::tidy::google::objc {
 
 namespace {
 
@@ -117,7 +114,4 @@
       << MatchedDecl << IsGlobal << generateFixItHint(MatchedDecl);
 }
 
-} // namespace objc
-} // namespace google
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::google::objc
diff --git a/clang-tools-extra/clang-tidy/google/GlobalNamesInHeadersCheck.cpp b/clang-tools-extra/clang-tidy/google/GlobalNamesInHeadersCheck.cpp
--- a/clang-tools-extra/clang-tidy/google/GlobalNamesInHeadersCheck.cpp
+++ b/clang-tools-extra/clang-tidy/google/GlobalNamesInHeadersCheck.cpp
@@ -14,10 +14,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace google {
-namespace readability {
+namespace clang::tidy::google::readability {
 
 GlobalNamesInHeadersCheck::GlobalNamesInHeadersCheck(StringRef Name,
                                                      ClangTidyContext *Context)
@@ -74,7 +71,4 @@
        "using declarations in the global namespace in headers are prohibited");
 }
 
-} // namespace readability
-} // namespace google
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::google::readability
diff --git a/clang-tools-extra/clang-tidy/google/GlobalVariableDeclarationCheck.cpp b/clang-tools-extra/clang-tidy/google/GlobalVariableDeclarationCheck.cpp
--- a/clang-tools-extra/clang-tidy/google/GlobalVariableDeclarationCheck.cpp
+++ b/clang-tools-extra/clang-tidy/google/GlobalVariableDeclarationCheck.cpp
@@ -16,10 +16,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace google {
-namespace objc {
+namespace clang::tidy::google::objc {
 
 namespace {
 
@@ -98,7 +95,4 @@
   }
 }
 
-}  // namespace objc
-}  // namespace google
-}  // namespace tidy
-}  // namespace clang
+} // namespace clang::tidy::google::objc
diff --git a/clang-tools-extra/clang-tidy/google/GoogleTidyModule.cpp b/clang-tools-extra/clang-tidy/google/GoogleTidyModule.cpp
--- a/clang-tools-extra/clang-tidy/google/GoogleTidyModule.cpp
+++ b/clang-tools-extra/clang-tidy/google/GoogleTidyModule.cpp
@@ -31,8 +31,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
+namespace clang::tidy {
 namespace google {
 
 class GoogleModule : public ClangTidyModule {
@@ -103,5 +102,4 @@
 // and thus register the GoogleModule.
 volatile int GoogleModuleAnchorSource = 0;
 
-}  // namespace tidy
-}  // namespace clang
+} // namespace clang::tidy
diff --git a/clang-tools-extra/clang-tidy/google/IntegerTypesCheck.cpp b/clang-tools-extra/clang-tidy/google/IntegerTypesCheck.cpp
--- a/clang-tools-extra/clang-tidy/google/IntegerTypesCheck.cpp
+++ b/clang-tools-extra/clang-tidy/google/IntegerTypesCheck.cpp
@@ -36,9 +36,7 @@
   return Tok;
 }
 
-namespace tidy {
-namespace google {
-namespace runtime {
+namespace tidy::google::runtime {
 
 IntegerTypesCheck::IntegerTypesCheck(StringRef Name, ClangTidyContext *Context)
     : ClangTidyCheck(Name, Context),
@@ -144,7 +142,5 @@
                                                << Replacement;
 }
 
-} // namespace runtime
-} // namespace google
-} // namespace tidy
+} // namespace tidy::google::runtime
 } // namespace clang
diff --git a/clang-tools-extra/clang-tidy/google/OverloadedUnaryAndCheck.cpp b/clang-tools-extra/clang-tidy/google/OverloadedUnaryAndCheck.cpp
--- a/clang-tools-extra/clang-tidy/google/OverloadedUnaryAndCheck.cpp
+++ b/clang-tools-extra/clang-tidy/google/OverloadedUnaryAndCheck.cpp
@@ -13,10 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace google {
-namespace runtime {
+namespace clang::tidy::google::runtime {
 
 void OverloadedUnaryAndCheck::registerMatchers(
     ast_matchers::MatchFinder *Finder) {
@@ -39,7 +36,4 @@
        "do not overload unary operator&, it is dangerous.");
 }
 
-} // namespace runtime
-} // namespace google
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::google::runtime
diff --git a/clang-tools-extra/clang-tidy/google/TodoCommentCheck.cpp b/clang-tools-extra/clang-tidy/google/TodoCommentCheck.cpp
--- a/clang-tools-extra/clang-tidy/google/TodoCommentCheck.cpp
+++ b/clang-tools-extra/clang-tidy/google/TodoCommentCheck.cpp
@@ -11,10 +11,7 @@
 #include "clang/Lex/Preprocessor.h"
 #include <optional>
 
-namespace clang {
-namespace tidy {
-namespace google {
-namespace readability {
+namespace clang::tidy::google::readability {
 
 class TodoCommentCheck::TodoCommentHandler : public CommentHandler {
 public:
@@ -64,7 +61,4 @@
   PP->addCommentHandler(Handler.get());
 }
 
-} // namespace readability
-} // namespace google
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::google::readability
diff --git a/clang-tools-extra/clang-tidy/google/UnnamedNamespaceInHeaderCheck.cpp b/clang-tools-extra/clang-tidy/google/UnnamedNamespaceInHeaderCheck.cpp
--- a/clang-tools-extra/clang-tidy/google/UnnamedNamespaceInHeaderCheck.cpp
+++ b/clang-tools-extra/clang-tidy/google/UnnamedNamespaceInHeaderCheck.cpp
@@ -13,10 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace google {
-namespace build {
+namespace clang::tidy::google::build {
 
 UnnamedNamespaceInHeaderCheck::UnnamedNamespaceInHeaderCheck(
     StringRef Name, ClangTidyContext *Context)
@@ -54,7 +51,4 @@
     diag(Loc, "do not use unnamed namespaces in header files");
 }
 
-} // namespace build
-} // namespace google
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::google::build
diff --git a/clang-tools-extra/clang-tidy/google/UpgradeGoogletestCaseCheck.cpp b/clang-tools-extra/clang-tidy/google/UpgradeGoogletestCaseCheck.cpp
--- a/clang-tools-extra/clang-tidy/google/UpgradeGoogletestCaseCheck.cpp
+++ b/clang-tools-extra/clang-tidy/google/UpgradeGoogletestCaseCheck.cpp
@@ -15,9 +15,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace google {
+namespace clang::tidy::google {
 
 static const llvm::StringRef RenameCaseToSuiteMessage =
     "Google Test APIs named with 'case' are deprecated; use equivalent APIs "
@@ -350,6 +348,4 @@
   Diag << FixItHint::CreateReplacement(ReplacementRange, ReplacementText);
 }
 
-} // namespace google
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::google
diff --git a/clang-tools-extra/clang-tidy/google/UsingNamespaceDirectiveCheck.cpp b/clang-tools-extra/clang-tidy/google/UsingNamespaceDirectiveCheck.cpp
--- a/clang-tools-extra/clang-tidy/google/UsingNamespaceDirectiveCheck.cpp
+++ b/clang-tools-extra/clang-tidy/google/UsingNamespaceDirectiveCheck.cpp
@@ -13,10 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace google {
-namespace build {
+namespace clang::tidy::google::build {
 
 void UsingNamespaceDirectiveCheck::registerMatchers(
     ast_matchers::MatchFinder *Finder) {
@@ -56,7 +53,4 @@
   return Parent->getName() == "literals" && Parent->getParent() &&
          Parent->getParent()->isStdNamespace();
 }
-} // namespace build
-} // namespace google
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::google::build
diff --git a/clang-tools-extra/clang-tidy/hicpp/ExceptionBaseclassCheck.cpp b/clang-tools-extra/clang-tidy/hicpp/ExceptionBaseclassCheck.cpp
--- a/clang-tools-extra/clang-tidy/hicpp/ExceptionBaseclassCheck.cpp
+++ b/clang-tools-extra/clang-tidy/hicpp/ExceptionBaseclassCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace hicpp {
+namespace clang::tidy::hicpp {
 
 void ExceptionBaseclassCheck::registerMatchers(MatchFinder *Finder) {
   Finder->addMatcher(
@@ -58,6 +56,4 @@
     diag(TypeDecl->getBeginLoc(), "type defined here", DiagnosticIDs::Note);
 }
 
-} // namespace hicpp
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::hicpp
diff --git a/clang-tools-extra/clang-tidy/hicpp/HICPPTidyModule.cpp b/clang-tools-extra/clang-tidy/hicpp/HICPPTidyModule.cpp
--- a/clang-tools-extra/clang-tidy/hicpp/HICPPTidyModule.cpp
+++ b/clang-tools-extra/clang-tidy/hicpp/HICPPTidyModule.cpp
@@ -41,8 +41,7 @@
 #include "NoAssemblerCheck.h"
 #include "SignedBitwiseCheck.h"
 
-namespace clang {
-namespace tidy {
+namespace clang::tidy {
 namespace hicpp {
 
 class HICPPModule : public ClangTidyModule {
@@ -120,5 +119,4 @@
 // and thus register the HICPPModule.
 volatile int HICPPModuleAnchorSource = 0;
 
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy
diff --git a/clang-tools-extra/clang-tidy/hicpp/MultiwayPathsCoveredCheck.cpp b/clang-tools-extra/clang-tidy/hicpp/MultiwayPathsCoveredCheck.cpp
--- a/clang-tools-extra/clang-tidy/hicpp/MultiwayPathsCoveredCheck.cpp
+++ b/clang-tools-extra/clang-tidy/hicpp/MultiwayPathsCoveredCheck.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace hicpp {
+namespace clang::tidy::hicpp {
 
 void MultiwayPathsCoveredCheck::storeOptions(
     ClangTidyOptions::OptionMap &Opts) {
@@ -174,6 +172,4 @@
          CaseCount == 1 ? "switch with only one case; use an if statement"
                         : "potential uncovered code path; add a default label");
 }
-} // namespace hicpp
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::hicpp
diff --git a/clang-tools-extra/clang-tidy/hicpp/NoAssemblerCheck.cpp b/clang-tools-extra/clang-tidy/hicpp/NoAssemblerCheck.cpp
--- a/clang-tools-extra/clang-tidy/hicpp/NoAssemblerCheck.cpp
+++ b/clang-tools-extra/clang-tidy/hicpp/NoAssemblerCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace hicpp {
+namespace clang::tidy::hicpp {
 
 namespace {
 AST_MATCHER(VarDecl, isAsm) { return Node.hasAttr<clang::AsmLabelAttr>(); }
@@ -44,6 +42,4 @@
   diag(ASMLocation, "do not use inline assembler in safety-critical code");
 }
 
-} // namespace hicpp
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::hicpp
diff --git a/clang-tools-extra/clang-tidy/hicpp/SignedBitwiseCheck.cpp b/clang-tools-extra/clang-tidy/hicpp/SignedBitwiseCheck.cpp
--- a/clang-tools-extra/clang-tidy/hicpp/SignedBitwiseCheck.cpp
+++ b/clang-tools-extra/clang-tidy/hicpp/SignedBitwiseCheck.cpp
@@ -13,9 +13,7 @@
 using namespace clang::ast_matchers;
 using namespace clang::ast_matchers::internal;
 
-namespace clang {
-namespace tidy {
-namespace hicpp {
+namespace clang::tidy::hicpp {
 
 SignedBitwiseCheck::SignedBitwiseCheck(StringRef Name,
                                        ClangTidyContext *Context)
@@ -100,6 +98,4 @@
       << IsUnary << SignedOperand->getSourceRange() << OperatorLoc;
 }
 
-} // namespace hicpp
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::hicpp
diff --git a/clang-tools-extra/clang-tidy/linuxkernel/LinuxKernelTidyModule.cpp b/clang-tools-extra/clang-tidy/linuxkernel/LinuxKernelTidyModule.cpp
--- a/clang-tools-extra/clang-tidy/linuxkernel/LinuxKernelTidyModule.cpp
+++ b/clang-tools-extra/clang-tidy/linuxkernel/LinuxKernelTidyModule.cpp
@@ -11,8 +11,7 @@
 #include "../ClangTidyModuleRegistry.h"
 #include "MustCheckErrsCheck.h"
 
-namespace clang {
-namespace tidy {
+namespace clang::tidy {
 namespace linuxkernel {
 
 /// This module is for checks specific to the Linux kernel.
@@ -33,5 +32,4 @@
 // and thus register the LinuxKernelModule.
 volatile int LinuxKernelModuleAnchorSource = 0;
 
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy
diff --git a/clang-tools-extra/clang-tidy/linuxkernel/MustCheckErrsCheck.cpp b/clang-tools-extra/clang-tidy/linuxkernel/MustCheckErrsCheck.cpp
--- a/clang-tools-extra/clang-tidy/linuxkernel/MustCheckErrsCheck.cpp
+++ b/clang-tools-extra/clang-tidy/linuxkernel/MustCheckErrsCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace linuxkernel {
+namespace clang::tidy::linuxkernel {
 
 void MustCheckErrsCheck::registerMatchers(MatchFinder *Finder) {
   auto ErrFn =
@@ -48,6 +46,4 @@
   }
 }
 
-} // namespace linuxkernel
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::linuxkernel
diff --git a/clang-tools-extra/clang-tidy/llvm/HeaderGuardCheck.cpp b/clang-tools-extra/clang-tidy/llvm/HeaderGuardCheck.cpp
--- a/clang-tools-extra/clang-tidy/llvm/HeaderGuardCheck.cpp
+++ b/clang-tools-extra/clang-tidy/llvm/HeaderGuardCheck.cpp
@@ -10,9 +10,7 @@
 #include "clang/Tooling/Tooling.h"
 #include "llvm/Support/Path.h"
 
-namespace clang {
-namespace tidy {
-namespace llvm_check {
+namespace clang::tidy::llvm_check {
 
 LLVMHeaderGuardCheck::LLVMHeaderGuardCheck(StringRef Name,
                                            ClangTidyContext *Context)
@@ -66,6 +64,4 @@
   return StringRef(Guard).upper();
 }
 
-} // namespace llvm_check
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::llvm_check
diff --git a/clang-tools-extra/clang-tidy/llvm/IncludeOrderCheck.cpp b/clang-tools-extra/clang-tidy/llvm/IncludeOrderCheck.cpp
--- a/clang-tools-extra/clang-tidy/llvm/IncludeOrderCheck.cpp
+++ b/clang-tools-extra/clang-tidy/llvm/IncludeOrderCheck.cpp
@@ -14,9 +14,7 @@
 
 #include <map>
 
-namespace clang {
-namespace tidy {
-namespace llvm_check {
+namespace clang::tidy::llvm_check {
 
 namespace {
 class IncludeOrderPPCallbacks : public PPCallbacks {
@@ -183,6 +181,4 @@
   IncludeDirectives.clear();
 }
 
-} // namespace llvm_check
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::llvm_check
diff --git a/clang-tools-extra/clang-tidy/llvm/LLVMTidyModule.cpp b/clang-tools-extra/clang-tidy/llvm/LLVMTidyModule.cpp
--- a/clang-tools-extra/clang-tidy/llvm/LLVMTidyModule.cpp
+++ b/clang-tools-extra/clang-tidy/llvm/LLVMTidyModule.cpp
@@ -18,8 +18,7 @@
 #include "PreferRegisterOverUnsignedCheck.h"
 #include "TwineLocalCheck.h"
 
-namespace clang {
-namespace tidy {
+namespace clang::tidy {
 namespace llvm_check {
 
 class LLVMModule : public ClangTidyModule {
@@ -60,5 +59,4 @@
 // and thus register the LLVMModule.
 volatile int LLVMModuleAnchorSource = 0;
 
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy
diff --git a/clang-tools-extra/clang-tidy/llvm/PreferIsaOrDynCastInConditionalsCheck.cpp b/clang-tools-extra/clang-tidy/llvm/PreferIsaOrDynCastInConditionalsCheck.cpp
--- a/clang-tools-extra/clang-tidy/llvm/PreferIsaOrDynCastInConditionalsCheck.cpp
+++ b/clang-tools-extra/clang-tidy/llvm/PreferIsaOrDynCastInConditionalsCheck.cpp
@@ -19,8 +19,7 @@
 AST_MATCHER(Expr, isMacroID) { return Node.getExprLoc().isMacroID(); }
 } // namespace ast_matchers
 
-namespace tidy {
-namespace llvm_check {
+namespace tidy::llvm_check {
 
 void PreferIsaOrDynCastInConditionalsCheck::registerMatchers(
     MatchFinder *Finder) {
@@ -130,6 +129,5 @@
   }
 }
 
-} // namespace llvm_check
-} // namespace tidy
+} // namespace tidy::llvm_check
 } // namespace clang
diff --git a/clang-tools-extra/clang-tidy/llvm/PreferRegisterOverUnsignedCheck.cpp b/clang-tools-extra/clang-tidy/llvm/PreferRegisterOverUnsignedCheck.cpp
--- a/clang-tools-extra/clang-tidy/llvm/PreferRegisterOverUnsignedCheck.cpp
+++ b/clang-tools-extra/clang-tidy/llvm/PreferRegisterOverUnsignedCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace llvm_check {
+namespace clang::tidy::llvm_check {
 
 void PreferRegisterOverUnsignedCheck::registerMatchers(MatchFinder *Finder) {
   auto RegisterClassMatch = hasType(
@@ -61,6 +59,4 @@
              NeedsQualification ? "llvm::Register" : "Register");
 }
 
-} // namespace llvm_check
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::llvm_check
diff --git a/clang-tools-extra/clang-tidy/llvm/TwineLocalCheck.cpp b/clang-tools-extra/clang-tidy/llvm/TwineLocalCheck.cpp
--- a/clang-tools-extra/clang-tidy/llvm/TwineLocalCheck.cpp
+++ b/clang-tools-extra/clang-tidy/llvm/TwineLocalCheck.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace llvm_check {
+namespace clang::tidy::llvm_check {
 
 void TwineLocalCheck::registerMatchers(MatchFinder *Finder) {
   auto TwineType =
@@ -62,6 +60,4 @@
   }
 }
 
-} // namespace llvm_check
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::llvm_check
diff --git a/clang-tools-extra/clang-tidy/llvmlibc/CalleeNamespaceCheck.cpp b/clang-tools-extra/clang-tidy/llvmlibc/CalleeNamespaceCheck.cpp
--- a/clang-tools-extra/clang-tidy/llvmlibc/CalleeNamespaceCheck.cpp
+++ b/clang-tools-extra/clang-tidy/llvmlibc/CalleeNamespaceCheck.cpp
@@ -14,9 +14,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace llvm_libc {
+namespace clang::tidy::llvm_libc {
 
 // Gets the outermost namespace of a DeclContext, right under the Translation
 // Unit.
@@ -65,6 +63,4 @@
        clang::DiagnosticIDs::Note);
 }
 
-} // namespace llvm_libc
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::llvm_libc
diff --git a/clang-tools-extra/clang-tidy/llvmlibc/ImplementationInNamespaceCheck.cpp b/clang-tools-extra/clang-tidy/llvmlibc/ImplementationInNamespaceCheck.cpp
--- a/clang-tools-extra/clang-tidy/llvmlibc/ImplementationInNamespaceCheck.cpp
+++ b/clang-tools-extra/clang-tidy/llvmlibc/ImplementationInNamespaceCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace llvm_libc {
+namespace clang::tidy::llvm_libc {
 
 const static StringRef RequiredNamespace = "__llvm_libc";
 void ImplementationInNamespaceCheck::registerMatchers(MatchFinder *Finder) {
@@ -43,6 +41,4 @@
       << RequiredNamespace;
 }
 
-} // namespace llvm_libc
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::llvm_libc
diff --git a/clang-tools-extra/clang-tidy/llvmlibc/LLVMLibcTidyModule.cpp b/clang-tools-extra/clang-tidy/llvmlibc/LLVMLibcTidyModule.cpp
--- a/clang-tools-extra/clang-tidy/llvmlibc/LLVMLibcTidyModule.cpp
+++ b/clang-tools-extra/clang-tidy/llvmlibc/LLVMLibcTidyModule.cpp
@@ -13,8 +13,7 @@
 #include "ImplementationInNamespaceCheck.h"
 #include "RestrictSystemLibcHeadersCheck.h"
 
-namespace clang {
-namespace tidy {
+namespace clang::tidy {
 namespace llvm_libc {
 
 class LLVMLibcModule : public ClangTidyModule {
@@ -39,5 +38,4 @@
 // and thus register the LLVMLibcModule.
 volatile int LLVMLibcModuleAnchorSource = 0;
 
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy
diff --git a/clang-tools-extra/clang-tidy/llvmlibc/RestrictSystemLibcHeadersCheck.cpp b/clang-tools-extra/clang-tidy/llvmlibc/RestrictSystemLibcHeadersCheck.cpp
--- a/clang-tools-extra/clang-tidy/llvmlibc/RestrictSystemLibcHeadersCheck.cpp
+++ b/clang-tools-extra/clang-tidy/llvmlibc/RestrictSystemLibcHeadersCheck.cpp
@@ -16,9 +16,7 @@
 // FixItHint - Hint to check documentation script to mark this check as
 // providing a FixIt.
 
-namespace clang {
-namespace tidy {
-namespace llvm_libc {
+namespace clang::tidy::llvm_libc {
 
 namespace {
 
@@ -66,6 +64,4 @@
       *this, SM, CompilerIncudeDir));
 }
 
-} // namespace llvm_libc
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::llvm_libc
diff --git a/clang-tools-extra/clang-tidy/misc/ConfusableIdentifierCheck.cpp b/clang-tools-extra/clang-tidy/misc/ConfusableIdentifierCheck.cpp
--- a/clang-tools-extra/clang-tidy/misc/ConfusableIdentifierCheck.cpp
+++ b/clang-tools-extra/clang-tidy/misc/ConfusableIdentifierCheck.cpp
@@ -21,9 +21,7 @@
 #include "Confusables.inc"
 } // namespace
 
-namespace clang {
-namespace tidy {
-namespace misc {
+namespace clang::tidy::misc {
 
 ConfusableIdentifierCheck::ConfusableIdentifierCheck(StringRef Name,
                                                      ClangTidyContext *Context)
@@ -169,6 +167,4 @@
   Finder->addMatcher(ast_matchers::namedDecl().bind("nameddecl"), this);
 }
 
-} // namespace misc
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::misc
diff --git a/clang-tools-extra/clang-tidy/misc/ConstCorrectnessCheck.cpp b/clang-tools-extra/clang-tidy/misc/ConstCorrectnessCheck.cpp
--- a/clang-tools-extra/clang-tidy/misc/ConstCorrectnessCheck.cpp
+++ b/clang-tools-extra/clang-tidy/misc/ConstCorrectnessCheck.cpp
@@ -14,9 +14,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace misc {
+namespace clang::tidy::misc {
 
 namespace {
 // FIXME: This matcher exists in some other code-review as well.
@@ -207,6 +205,4 @@
     Analyzer = std::make_unique<ExprMutationAnalyzer>(*LocalScope, *Context);
 }
 
-} // namespace misc
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::misc
diff --git a/clang-tools-extra/clang-tidy/misc/DefinitionsInHeadersCheck.cpp b/clang-tools-extra/clang-tidy/misc/DefinitionsInHeadersCheck.cpp
--- a/clang-tools-extra/clang-tidy/misc/DefinitionsInHeadersCheck.cpp
+++ b/clang-tools-extra/clang-tidy/misc/DefinitionsInHeadersCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace misc {
+namespace clang::tidy::misc {
 
 namespace {
 
@@ -160,6 +158,4 @@
   }
 }
 
-} // namespace misc
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::misc
diff --git a/clang-tools-extra/clang-tidy/misc/MiscTidyModule.cpp b/clang-tools-extra/clang-tidy/misc/MiscTidyModule.cpp
--- a/clang-tools-extra/clang-tidy/misc/MiscTidyModule.cpp
+++ b/clang-tools-extra/clang-tidy/misc/MiscTidyModule.cpp
@@ -29,8 +29,7 @@
 #include "UnusedUsingDeclsCheck.h"
 #include "UseAnonymousNamespaceCheck.h"
 
-namespace clang {
-namespace tidy {
+namespace clang::tidy {
 namespace misc {
 
 class MiscModule : public ClangTidyModule {
@@ -84,5 +83,4 @@
 // and thus register the MiscModule.
 volatile int MiscModuleAnchorSource = 0;
 
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy
diff --git a/clang-tools-extra/clang-tidy/misc/MisleadingIdentifier.cpp b/clang-tools-extra/clang-tidy/misc/MisleadingIdentifier.cpp
--- a/clang-tools-extra/clang-tidy/misc/MisleadingIdentifier.cpp
+++ b/clang-tools-extra/clang-tidy/misc/MisleadingIdentifier.cpp
@@ -11,9 +11,7 @@
 #include "clang/Frontend/CompilerInstance.h"
 #include "llvm/Support/ConvertUTF.h"
 
-namespace clang {
-namespace tidy {
-namespace misc {
+namespace clang::tidy::misc {
 
 // See https://www.unicode.org/Public/14.0.0/ucd/extracted/DerivedBidiClass.txt
 static bool isUnassignedAL(llvm::UTF32 CP) {
@@ -161,6 +159,4 @@
   Finder->addMatcher(ast_matchers::namedDecl().bind("nameddecl"), this);
 }
 
-} // namespace misc
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::misc
diff --git a/clang-tools-extra/clang-tidy/misc/MisplacedConstCheck.cpp b/clang-tools-extra/clang-tidy/misc/MisplacedConstCheck.cpp
--- a/clang-tools-extra/clang-tidy/misc/MisplacedConstCheck.cpp
+++ b/clang-tools-extra/clang-tidy/misc/MisplacedConstCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace misc {
+namespace clang::tidy::misc {
 
 void MisplacedConstCheck::registerMatchers(MatchFinder *Finder) {
   auto NonConstAndNonFunctionPointerType = hasType(pointerType(unless(
@@ -74,6 +72,4 @@
   diag(AliasLoc, "%0 declared here", DiagnosticIDs::Note) << AliasType;
 }
 
-} // namespace misc
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::misc
diff --git a/clang-tools-extra/clang-tidy/misc/NewDeleteOverloadsCheck.cpp b/clang-tools-extra/clang-tidy/misc/NewDeleteOverloadsCheck.cpp
--- a/clang-tools-extra/clang-tidy/misc/NewDeleteOverloadsCheck.cpp
+++ b/clang-tools-extra/clang-tidy/misc/NewDeleteOverloadsCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace misc {
+namespace clang::tidy::misc {
 
 namespace {
 
@@ -204,6 +202,4 @@
         << FD << getOperatorName(getCorrespondingOverload(FD));
 }
 
-} // namespace misc
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::misc
diff --git a/clang-tools-extra/clang-tidy/misc/NoRecursionCheck.cpp b/clang-tools-extra/clang-tidy/misc/NoRecursionCheck.cpp
--- a/clang-tools-extra/clang-tidy/misc/NoRecursionCheck.cpp
+++ b/clang-tools-extra/clang-tidy/misc/NoRecursionCheck.cpp
@@ -15,9 +15,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace misc {
+namespace clang::tidy::misc {
 
 namespace {
 
@@ -270,6 +268,4 @@
   }
 }
 
-} // namespace misc
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::misc
diff --git a/clang-tools-extra/clang-tidy/misc/NonCopyableObjects.cpp b/clang-tools-extra/clang-tidy/misc/NonCopyableObjects.cpp
--- a/clang-tools-extra/clang-tidy/misc/NonCopyableObjects.cpp
+++ b/clang-tools-extra/clang-tidy/misc/NonCopyableObjects.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace misc {
+namespace clang::tidy::misc {
 
 void NonCopyableObjectsCheck::registerMatchers(MatchFinder *Finder) {
   // There are two ways to get into trouble with objects like FILE *:
@@ -67,7 +65,4 @@
         << BD;
 }
 
-} // namespace misc
-} // namespace tidy
-} // namespace clang
-
+} // namespace clang::tidy::misc
diff --git a/clang-tools-extra/clang-tidy/misc/NonPrivateMemberVariablesInClassesCheck.cpp b/clang-tools-extra/clang-tidy/misc/NonPrivateMemberVariablesInClassesCheck.cpp
--- a/clang-tools-extra/clang-tidy/misc/NonPrivateMemberVariablesInClassesCheck.cpp
+++ b/clang-tools-extra/clang-tidy/misc/NonPrivateMemberVariablesInClassesCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace misc {
+namespace clang::tidy::misc {
 
 namespace {
 
@@ -92,6 +90,4 @@
       << Field << Field->getAccess();
 }
 
-} // namespace misc
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::misc
diff --git a/clang-tools-extra/clang-tidy/misc/RedundantExpressionCheck.cpp b/clang-tools-extra/clang-tidy/misc/RedundantExpressionCheck.cpp
--- a/clang-tools-extra/clang-tidy/misc/RedundantExpressionCheck.cpp
+++ b/clang-tools-extra/clang-tidy/misc/RedundantExpressionCheck.cpp
@@ -32,9 +32,7 @@
 using namespace clang::ast_matchers;
 using namespace clang::tidy::matchers;
 
-namespace clang {
-namespace tidy {
-namespace misc {
+namespace clang::tidy::misc {
 namespace {
 using llvm::APSInt;
 
@@ -1357,6 +1355,4 @@
   checkRelationalExpr(Result);
 }
 
-} // namespace misc
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::misc
diff --git a/clang-tools-extra/clang-tidy/misc/StaticAssertCheck.cpp b/clang-tools-extra/clang-tidy/misc/StaticAssertCheck.cpp
--- a/clang-tools-extra/clang-tidy/misc/StaticAssertCheck.cpp
+++ b/clang-tools-extra/clang-tidy/misc/StaticAssertCheck.cpp
@@ -20,9 +20,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace misc {
+namespace clang::tidy::misc {
 
 StaticAssertCheck::StaticAssertCheck(StringRef Name, ClangTidyContext *Context)
     : ClangTidyCheck(Name, Context) {}
@@ -167,6 +165,4 @@
   return Token.getLocation();
 }
 
-} // namespace misc
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::misc
diff --git a/clang-tools-extra/clang-tidy/misc/ThrowByValueCatchByReferenceCheck.cpp b/clang-tools-extra/clang-tidy/misc/ThrowByValueCatchByReferenceCheck.cpp
--- a/clang-tools-extra/clang-tidy/misc/ThrowByValueCatchByReferenceCheck.cpp
+++ b/clang-tools-extra/clang-tidy/misc/ThrowByValueCatchByReferenceCheck.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace misc {
+namespace clang::tidy::misc {
 
 ThrowByValueCatchByReferenceCheck::ThrowByValueCatchByReferenceCheck(
     StringRef Name, ClangTidyContext *Context)
@@ -170,6 +168,4 @@
   }
 }
 
-} // namespace misc
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::misc
diff --git a/clang-tools-extra/clang-tidy/misc/UnconventionalAssignOperatorCheck.cpp b/clang-tools-extra/clang-tidy/misc/UnconventionalAssignOperatorCheck.cpp
--- a/clang-tools-extra/clang-tidy/misc/UnconventionalAssignOperatorCheck.cpp
+++ b/clang-tools-extra/clang-tidy/misc/UnconventionalAssignOperatorCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace misc {
+namespace clang::tidy::misc {
 
 void UnconventionalAssignOperatorCheck::registerMatchers(
     ast_matchers::MatchFinder *Finder) {
@@ -89,6 +87,4 @@
   }
 }
 
-} // namespace misc
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::misc
diff --git a/clang-tools-extra/clang-tidy/misc/UniqueptrResetReleaseCheck.cpp b/clang-tools-extra/clang-tidy/misc/UniqueptrResetReleaseCheck.cpp
--- a/clang-tools-extra/clang-tidy/misc/UniqueptrResetReleaseCheck.cpp
+++ b/clang-tools-extra/clang-tidy/misc/UniqueptrResetReleaseCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace misc {
+namespace clang::tidy::misc {
 
 UniqueptrResetReleaseCheck::UniqueptrResetReleaseCheck(
     StringRef Name, ClangTidyContext *Context)
@@ -148,6 +146,4 @@
         Result.SourceManager->getFileID(ResetMember->getBeginLoc()),
         "<utility>");
 }
-} // namespace misc
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::misc
diff --git a/clang-tools-extra/clang-tidy/misc/UnusedAliasDeclsCheck.cpp b/clang-tools-extra/clang-tidy/misc/UnusedAliasDeclsCheck.cpp
--- a/clang-tools-extra/clang-tidy/misc/UnusedAliasDeclsCheck.cpp
+++ b/clang-tools-extra/clang-tidy/misc/UnusedAliasDeclsCheck.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace misc {
+namespace clang::tidy::misc {
 
 void UnusedAliasDeclsCheck::registerMatchers(MatchFinder *Finder) {
   // We cannot do anything about headers (yet), as the alias declarations
@@ -53,6 +51,4 @@
   }
 }
 
-} // namespace misc
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::misc
diff --git a/clang-tools-extra/clang-tidy/misc/UnusedParametersCheck.cpp b/clang-tools-extra/clang-tidy/misc/UnusedParametersCheck.cpp
--- a/clang-tools-extra/clang-tidy/misc/UnusedParametersCheck.cpp
+++ b/clang-tools-extra/clang-tidy/misc/UnusedParametersCheck.cpp
@@ -18,9 +18,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace misc {
+namespace clang::tidy::misc {
 
 namespace {
 bool isOverrideMethod(const FunctionDecl *Function) {
@@ -198,6 +196,4 @@
   }
 }
 
-} // namespace misc
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::misc
diff --git a/clang-tools-extra/clang-tidy/misc/UnusedUsingDeclsCheck.cpp b/clang-tools-extra/clang-tidy/misc/UnusedUsingDeclsCheck.cpp
--- a/clang-tools-extra/clang-tidy/misc/UnusedUsingDeclsCheck.cpp
+++ b/clang-tools-extra/clang-tidy/misc/UnusedUsingDeclsCheck.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace misc {
+namespace clang::tidy::misc {
 
 namespace {
 
@@ -201,6 +199,4 @@
   Contexts.clear();
 }
 
-} // namespace misc
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::misc
diff --git a/clang-tools-extra/clang-tidy/misc/UseAnonymousNamespaceCheck.cpp b/clang-tools-extra/clang-tidy/misc/UseAnonymousNamespaceCheck.cpp
--- a/clang-tools-extra/clang-tidy/misc/UseAnonymousNamespaceCheck.cpp
+++ b/clang-tools-extra/clang-tidy/misc/UseAnonymousNamespaceCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace misc {
+namespace clang::tidy::misc {
 namespace {
 AST_POLYMORPHIC_MATCHER_P(isInHeaderFile,
                           AST_POLYMORPHIC_SUPPORTED_TYPES(FunctionDecl,
@@ -74,6 +72,4 @@
   }
 }
 
-} // namespace misc
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::misc
diff --git a/clang-tools-extra/clang-tidy/modernize/AvoidBindCheck.cpp b/clang-tools-extra/clang-tidy/modernize/AvoidBindCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/AvoidBindCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/AvoidBindCheck.cpp
@@ -29,9 +29,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 namespace {
 
@@ -717,6 +715,4 @@
                                        Stream.str());
 }
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
diff --git a/clang-tools-extra/clang-tidy/modernize/AvoidCArraysCheck.cpp b/clang-tools-extra/clang-tidy/modernize/AvoidCArraysCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/AvoidCArraysCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/AvoidCArraysCheck.cpp
@@ -38,9 +38,7 @@
 
 } // namespace
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 void AvoidCArraysCheck::registerMatchers(MatchFinder *Finder) {
   Finder->addMatcher(
@@ -63,6 +61,4 @@
       << ArrayType->getTypePtr()->isVariableArrayType();
 }
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
diff --git a/clang-tools-extra/clang-tidy/modernize/ConcatNestedNamespacesCheck.cpp b/clang-tools-extra/clang-tidy/modernize/ConcatNestedNamespacesCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/ConcatNestedNamespacesCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/ConcatNestedNamespacesCheck.cpp
@@ -12,9 +12,7 @@
 #include "clang/Lex/Lexer.h"
 #include <algorithm>
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 static bool locationsInSameFile(const SourceManager &Sources,
                                 SourceLocation Loc1, SourceLocation Loc2) {
@@ -102,6 +100,4 @@
   Namespaces.clear();
 }
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
diff --git a/clang-tools-extra/clang-tidy/modernize/DeprecatedHeadersCheck.cpp b/clang-tools-extra/clang-tidy/modernize/DeprecatedHeadersCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/DeprecatedHeadersCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/DeprecatedHeadersCheck.cpp
@@ -19,9 +19,7 @@
 
 using IncludeMarker =
     clang::tidy::modernize::DeprecatedHeadersCheck::IncludeMarker;
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 namespace {
 
 class IncludeModernizePPCallbacks : public PPCallbacks {
@@ -211,6 +209,4 @@
   }
 }
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
diff --git a/clang-tools-extra/clang-tidy/modernize/DeprecatedIosBaseAliasesCheck.cpp b/clang-tools-extra/clang-tidy/modernize/DeprecatedIosBaseAliasesCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/DeprecatedIosBaseAliasesCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/DeprecatedIosBaseAliasesCheck.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 static constexpr std::array<StringRef, 5> DeprecatedTypes = {
     "::std::ios_base::io_state", "::std::ios_base::open_mode",
@@ -72,6 +70,4 @@
     diag(IoStateLoc, "'std::ios_base::%0' is deprecated") << TypeName;
 }
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
diff --git a/clang-tools-extra/clang-tidy/modernize/IntegralLiteralExpressionMatcher.cpp b/clang-tools-extra/clang-tidy/modernize/IntegralLiteralExpressionMatcher.cpp
--- a/clang-tools-extra/clang-tidy/modernize/IntegralLiteralExpressionMatcher.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/IntegralLiteralExpressionMatcher.cpp
@@ -12,9 +12,7 @@
 #include <cctype>
 #include <stdexcept>
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 // Validate that this literal token is a valid integer literal.  A literal token
 // could be a floating-point token, which isn't acceptable as a value for an
@@ -285,6 +283,4 @@
   return LargestSize;
 }
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
diff --git a/clang-tools-extra/clang-tidy/modernize/LoopConvertCheck.cpp b/clang-tools-extra/clang-tidy/modernize/LoopConvertCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/LoopConvertCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/LoopConvertCheck.cpp
@@ -27,8 +27,7 @@
 using namespace clang::ast_matchers;
 using namespace llvm;
 
-namespace clang {
-namespace tidy {
+namespace clang::tidy {
 
 template <> struct OptionEnumMapping<modernize::Confidence::Level> {
   static llvm::ArrayRef<std::pair<modernize::Confidence::Level, StringRef>>
@@ -970,5 +969,4 @@
 }
 
 } // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy
diff --git a/clang-tools-extra/clang-tidy/modernize/LoopConvertUtils.cpp b/clang-tools-extra/clang-tidy/modernize/LoopConvertUtils.cpp
--- a/clang-tools-extra/clang-tidy/modernize/LoopConvertUtils.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/LoopConvertUtils.cpp
@@ -27,9 +27,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 /// Tracks a stack of parent statements during traversal.
 ///
@@ -911,6 +909,4 @@
   return DeclFinder.findUsages(SourceStmt);
 }
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
diff --git a/clang-tools-extra/clang-tidy/modernize/MacroToEnumCheck.cpp b/clang-tools-extra/clang-tidy/modernize/MacroToEnumCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/MacroToEnumCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/MacroToEnumCheck.cpp
@@ -18,9 +18,7 @@
 #include <cctype>
 #include <string>
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 static bool hasOnlyComments(SourceLocation Loc, const LangOptions &Options,
                             StringRef Text) {
@@ -556,6 +554,4 @@
     PPCallback->invalidateRange(Range);
 }
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
diff --git a/clang-tools-extra/clang-tidy/modernize/MakeSharedCheck.cpp b/clang-tools-extra/clang-tidy/modernize/MakeSharedCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/MakeSharedCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/MakeSharedCheck.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 MakeSharedCheck::MakeSharedCheck(StringRef Name, ClangTidyContext *Context)
     : MakeSmartPtrCheck(Name, Context, "std::make_shared") {}
@@ -29,6 +27,4 @@
                                      qualType().bind(PointerType)))))))));
 }
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
diff --git a/clang-tools-extra/clang-tidy/modernize/MakeSmartPtrCheck.cpp b/clang-tools-extra/clang-tidy/modernize/MakeSmartPtrCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/MakeSmartPtrCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/MakeSmartPtrCheck.cpp
@@ -14,9 +14,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 namespace {
 
@@ -439,6 +437,4 @@
   Diag << Inserter.createIncludeInsertion(FD, MakeSmartPtrFunctionHeader);
 }
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
diff --git a/clang-tools-extra/clang-tidy/modernize/MakeUniqueCheck.cpp b/clang-tools-extra/clang-tidy/modernize/MakeUniqueCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/MakeUniqueCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/MakeUniqueCheck.cpp
@@ -10,9 +10,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 MakeUniqueCheck::MakeUniqueCheck(StringRef Name,
                                  clang::tidy::ClangTidyContext *Context)
@@ -43,6 +41,4 @@
 
 // FixItHint is done by MakeSmartPtrCheck
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
diff --git a/clang-tools-extra/clang-tidy/modernize/ModernizeTidyModule.cpp b/clang-tools-extra/clang-tidy/modernize/ModernizeTidyModule.cpp
--- a/clang-tools-extra/clang-tidy/modernize/ModernizeTidyModule.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/ModernizeTidyModule.cpp
@@ -44,8 +44,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
+namespace clang::tidy {
 namespace modernize {
 
 class ModernizeModule : public ClangTidyModule {
@@ -130,5 +129,4 @@
 // and thus register the ModernizeModule.
 volatile int ModernizeModuleAnchorSource = 0;
 
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy
diff --git a/clang-tools-extra/clang-tidy/modernize/PassByValueCheck.cpp b/clang-tools-extra/clang-tidy/modernize/PassByValueCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/PassByValueCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/PassByValueCheck.cpp
@@ -18,9 +18,7 @@
 using namespace clang::ast_matchers;
 using namespace llvm;
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 namespace {
 /// Matches move-constructible classes.
@@ -305,6 +303,4 @@
               "<utility>");
 }
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
diff --git a/clang-tools-extra/clang-tidy/modernize/RawStringLiteralCheck.cpp b/clang-tools-extra/clang-tidy/modernize/RawStringLiteralCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/RawStringLiteralCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/RawStringLiteralCheck.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 namespace {
 
@@ -147,6 +145,4 @@
       << FixItHint::CreateReplacement(CharRange, Replacement);
 }
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
diff --git a/clang-tools-extra/clang-tidy/modernize/RedundantVoidArgCheck.cpp b/clang-tools-extra/clang-tidy/modernize/RedundantVoidArgCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/RedundantVoidArgCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/RedundantVoidArgCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 namespace {
 
@@ -287,6 +285,4 @@
   }
 }
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
diff --git a/clang-tools-extra/clang-tidy/modernize/ReplaceAutoPtrCheck.cpp b/clang-tools-extra/clang-tidy/modernize/ReplaceAutoPtrCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/ReplaceAutoPtrCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/ReplaceAutoPtrCheck.cpp
@@ -16,9 +16,7 @@
 using namespace clang;
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 namespace {
 static const char AutoPtrTokenId[] = "AutoPrTokenId";
@@ -150,6 +148,4 @@
                                       "unique_ptr");
 }
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
diff --git a/clang-tools-extra/clang-tidy/modernize/ReplaceDisallowCopyAndAssignMacroCheck.cpp b/clang-tools-extra/clang-tidy/modernize/ReplaceDisallowCopyAndAssignMacroCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/ReplaceDisallowCopyAndAssignMacroCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/ReplaceDisallowCopyAndAssignMacroCheck.cpp
@@ -14,9 +14,7 @@
 #include "llvm/Support/FormatVariadic.h"
 #include <optional>
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 namespace {
 
@@ -88,6 +86,4 @@
   Options.store(Opts, "MacroName", MacroName);
 }
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
diff --git a/clang-tools-extra/clang-tidy/modernize/ReplaceRandomShuffleCheck.cpp b/clang-tools-extra/clang-tidy/modernize/ReplaceRandomShuffleCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/ReplaceRandomShuffleCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/ReplaceRandomShuffleCheck.cpp
@@ -16,9 +16,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 ReplaceRandomShuffleCheck::ReplaceRandomShuffleCheck(StringRef Name,
                                                      ClangTidyContext *Context)
@@ -96,6 +94,4 @@
       "<random>");
 }
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
diff --git a/clang-tools-extra/clang-tidy/modernize/ReturnBracedInitListCheck.cpp b/clang-tools-extra/clang-tidy/modernize/ReturnBracedInitListCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/ReturnBracedInitListCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/ReturnBracedInitListCheck.cpp
@@ -14,9 +14,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 void ReturnBracedInitListCheck::registerMatchers(MatchFinder *Finder) {
   // Skip list initialization and constructors with an initializer list.
@@ -82,6 +80,4 @@
        << FixItHint::CreateReplacement(CallParensRange.getEnd(), "}");
 }
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
diff --git a/clang-tools-extra/clang-tidy/modernize/ShrinkToFitCheck.cpp b/clang-tools-extra/clang-tidy/modernize/ShrinkToFitCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/ShrinkToFitCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/ShrinkToFitCheck.cpp
@@ -14,9 +14,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 void ShrinkToFitCheck::registerMatchers(MatchFinder *Finder) {
   // Swap as a function need not to be considered, because rvalue can not
@@ -75,6 +73,4 @@
       << Hint;
 }
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
diff --git a/clang-tools-extra/clang-tidy/modernize/UnaryStaticAssertCheck.cpp b/clang-tools-extra/clang-tidy/modernize/UnaryStaticAssertCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/UnaryStaticAssertCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/UnaryStaticAssertCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 void UnaryStaticAssertCheck::registerMatchers(MatchFinder *Finder) {
   Finder->addMatcher(staticAssertDecl().bind("static_assert"), this);
@@ -36,6 +34,4 @@
       << FixItHint::CreateRemoval(AssertMessage->getSourceRange());
 }
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
diff --git a/clang-tools-extra/clang-tidy/modernize/UseAutoCheck.cpp b/clang-tools-extra/clang-tidy/modernize/UseAutoCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/UseAutoCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/UseAutoCheck.cpp
@@ -17,9 +17,7 @@
 using namespace clang::ast_matchers;
 using namespace clang::ast_matchers::internal;
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 namespace {
 
 const char IteratorDeclStmtId[] = "iterator_decl";
@@ -449,6 +447,4 @@
   }
 }
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
diff --git a/clang-tools-extra/clang-tidy/modernize/UseBoolLiteralsCheck.cpp b/clang-tools-extra/clang-tidy/modernize/UseBoolLiteralsCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/UseBoolLiteralsCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/UseBoolLiteralsCheck.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 UseBoolLiteralsCheck::UseBoolLiteralsCheck(StringRef Name,
                                            ClangTidyContext *Context)
@@ -74,6 +72,4 @@
         Expression->getSourceRange(), LiteralBooleanValue ? "true" : "false");
 }
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
diff --git a/clang-tools-extra/clang-tidy/modernize/UseDefaultMemberInitCheck.cpp b/clang-tools-extra/clang-tidy/modernize/UseDefaultMemberInitCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/UseDefaultMemberInitCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/UseDefaultMemberInitCheck.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 namespace {
 AST_MATCHER_P(InitListExpr, initCountIs, unsigned, N) {
@@ -296,6 +294,4 @@
       << FixItHint::CreateRemoval(Init->getSourceRange());
 }
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
diff --git a/clang-tools-extra/clang-tidy/modernize/UseEmplaceCheck.cpp b/clang-tools-extra/clang-tidy/modernize/UseEmplaceCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/UseEmplaceCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/UseEmplaceCheck.cpp
@@ -10,9 +10,7 @@
 #include "../utils/OptionsUtils.h"
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 namespace {
 // Identical to hasAnyName, except it does not take template specifiers into
@@ -374,6 +372,4 @@
                 utils::options::serializeStringList(EmplacyFunctions));
 }
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
diff --git a/clang-tools-extra/clang-tidy/modernize/UseEqualsDefaultCheck.cpp b/clang-tools-extra/clang-tidy/modernize/UseEqualsDefaultCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/UseEqualsDefaultCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/UseEqualsDefaultCheck.cpp
@@ -16,9 +16,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 static const char SpecialFunction[] = "SpecialFunction";
 
@@ -355,6 +353,4 @@
   }
 }
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
diff --git a/clang-tools-extra/clang-tidy/modernize/UseEqualsDeleteCheck.cpp b/clang-tools-extra/clang-tidy/modernize/UseEqualsDeleteCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/UseEqualsDeleteCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/UseEqualsDeleteCheck.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 static const char SpecialFunction[] = "SpecialFunction";
 static const char DeletedNotPublic[] = "DeletedNotPublic";
@@ -75,6 +73,4 @@
   }
 }
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
diff --git a/clang-tools-extra/clang-tidy/modernize/UseNodiscardCheck.cpp b/clang-tools-extra/clang-tidy/modernize/UseNodiscardCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/UseNodiscardCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/UseNodiscardCheck.cpp
@@ -14,9 +14,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 static bool doesNoDiscardMacroExist(ASTContext &Context,
                                     const llvm::StringRef &MacroId) {
@@ -146,6 +144,4 @@
   return LangOpts.CPlusPlus;
 }
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
diff --git a/clang-tools-extra/clang-tidy/modernize/UseNoexceptCheck.cpp b/clang-tools-extra/clang-tidy/modernize/UseNoexceptCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/UseNoexceptCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/UseNoexceptCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 namespace {
 AST_MATCHER(NamedDecl, isValid) { return !Node.isInvalidDecl(); }
@@ -105,6 +103,4 @@
       << ReplacementStr.empty() << ReplacementStr << FixIt;
 }
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
diff --git a/clang-tools-extra/clang-tidy/modernize/UseNullptrCheck.cpp b/clang-tools-extra/clang-tidy/modernize/UseNullptrCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/UseNullptrCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/UseNullptrCheck.cpp
@@ -16,9 +16,7 @@
 using namespace clang::ast_matchers;
 using namespace llvm;
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 namespace {
 
 const char CastSequence[] = "sequence";
@@ -510,6 +508,4 @@
       .TraverseStmt(const_cast<CastExpr *>(NullCast));
 }
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
diff --git a/clang-tools-extra/clang-tidy/modernize/UseOverrideCheck.cpp b/clang-tools-extra/clang-tidy/modernize/UseOverrideCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/UseOverrideCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/UseOverrideCheck.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 UseOverrideCheck::UseOverrideCheck(StringRef Name, ClangTidyContext *Context)
     : ClangTidyCheck(Name, Context),
@@ -228,6 +226,4 @@
   }
 }
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
diff --git a/clang-tools-extra/clang-tidy/modernize/UseTrailingReturnTypeCheck.cpp b/clang-tools-extra/clang-tidy/modernize/UseTrailingReturnTypeCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/UseTrailingReturnTypeCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/UseTrailingReturnTypeCheck.cpp
@@ -19,9 +19,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 namespace {
 struct UnqualNameVisitor : public RecursiveASTVisitor<UnqualNameVisitor> {
 public:
@@ -496,6 +494,4 @@
       << FixItHint::CreateInsertion(InsertionLoc, " -> " + ReturnType);
 }
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
diff --git a/clang-tools-extra/clang-tidy/modernize/UseTransparentFunctorsCheck.cpp b/clang-tools-extra/clang-tidy/modernize/UseTransparentFunctorsCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/UseTransparentFunctorsCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/UseTransparentFunctorsCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 UseTransparentFunctorsCheck::UseTransparentFunctorsCheck(
     StringRef Name, ClangTidyContext *Context)
@@ -124,6 +122,4 @@
                                   FunctorTypeLoc.getArgLoc(0).getSourceRange());
 }
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
diff --git a/clang-tools-extra/clang-tidy/modernize/UseUncaughtExceptionsCheck.cpp b/clang-tools-extra/clang-tidy/modernize/UseUncaughtExceptionsCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/UseUncaughtExceptionsCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/UseUncaughtExceptionsCheck.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 void UseUncaughtExceptionsCheck::registerMatchers(MatchFinder *Finder) {
   std::string MatchText = "::std::uncaught_exception";
@@ -97,6 +95,4 @@
   }
 }
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
diff --git a/clang-tools-extra/clang-tidy/modernize/UseUsingCheck.cpp b/clang-tools-extra/clang-tidy/modernize/UseUsingCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/UseUsingCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/UseUsingCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 static constexpr llvm::StringLiteral ParentDeclName = "parent-decl";
 static constexpr llvm::StringLiteral TagDeclName = "tag-decl";
@@ -142,6 +140,4 @@
   std::string Replacement = Using + Name + " = " + Type;
   Diag << FixItHint::CreateReplacement(ReplaceRange, Replacement);
 }
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
diff --git a/clang-tools-extra/clang-tidy/mpi/BufferDerefCheck.cpp b/clang-tools-extra/clang-tidy/mpi/BufferDerefCheck.cpp
--- a/clang-tools-extra/clang-tidy/mpi/BufferDerefCheck.cpp
+++ b/clang-tools-extra/clang-tidy/mpi/BufferDerefCheck.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace mpi {
+namespace clang::tidy::mpi {
 
 void BufferDerefCheck::registerMatchers(MatchFinder *Finder) {
   Finder->addMatcher(callExpr().bind("CE"), this);
@@ -128,6 +126,4 @@
 }
 
 void BufferDerefCheck::onEndOfTranslationUnit() { FuncClassifier.reset(); }
-} // namespace mpi
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::mpi
diff --git a/clang-tools-extra/clang-tidy/mpi/MPITidyModule.cpp b/clang-tools-extra/clang-tidy/mpi/MPITidyModule.cpp
--- a/clang-tools-extra/clang-tidy/mpi/MPITidyModule.cpp
+++ b/clang-tools-extra/clang-tidy/mpi/MPITidyModule.cpp
@@ -12,8 +12,7 @@
 #include "BufferDerefCheck.h"
 #include "TypeMismatchCheck.h"
 
-namespace clang {
-namespace tidy {
+namespace clang::tidy {
 namespace mpi {
 
 class MPIModule : public ClangTidyModule {
@@ -34,5 +33,4 @@
 // and thus register the MPIModule.
 volatile int MPIModuleAnchorSource = 0;
 
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy
diff --git a/clang-tools-extra/clang-tidy/mpi/TypeMismatchCheck.cpp b/clang-tools-extra/clang-tidy/mpi/TypeMismatchCheck.cpp
--- a/clang-tools-extra/clang-tidy/mpi/TypeMismatchCheck.cpp
+++ b/clang-tools-extra/clang-tidy/mpi/TypeMismatchCheck.cpp
@@ -14,9 +14,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace mpi {
+namespace clang::tidy::mpi {
 
 /// Check if a BuiltinType::Kind matches the MPI datatype.
 ///
@@ -330,6 +328,4 @@
 }
 
 void TypeMismatchCheck::onEndOfTranslationUnit() { FuncClassifier.reset(); }
-} // namespace mpi
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::mpi
diff --git a/clang-tools-extra/clang-tidy/objc/AssertEquals.cpp b/clang-tools-extra/clang-tidy/objc/AssertEquals.cpp
--- a/clang-tools-extra/clang-tidy/objc/AssertEquals.cpp
+++ b/clang-tools-extra/clang-tidy/objc/AssertEquals.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace objc {
+namespace clang::tidy::objc {
 
 // Mapping from `XCTAssert*Equal` to `XCTAssert*EqualObjects` name.
 static const std::map<std::string, std::string> &NameMap() {
@@ -60,6 +58,4 @@
   }
 }
 
-} // namespace objc
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::objc
diff --git a/clang-tools-extra/clang-tidy/objc/AvoidNSErrorInitCheck.cpp b/clang-tools-extra/clang-tidy/objc/AvoidNSErrorInitCheck.cpp
--- a/clang-tools-extra/clang-tidy/objc/AvoidNSErrorInitCheck.cpp
+++ b/clang-tools-extra/clang-tidy/objc/AvoidNSErrorInitCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace objc {
+namespace clang::tidy::objc {
 
 void AvoidNSErrorInitCheck::registerMatchers(MatchFinder *Finder) {
   Finder->addMatcher(objcMessageExpr(hasSelector("init"),
@@ -31,6 +29,4 @@
        "create a new NSError");
 }
 
-}  // namespace objc
-}  // namespace tidy
-}  // namespace clang
+} // namespace clang::tidy::objc
diff --git a/clang-tools-extra/clang-tidy/objc/DeallocInCategoryCheck.cpp b/clang-tools-extra/clang-tidy/objc/DeallocInCategoryCheck.cpp
--- a/clang-tools-extra/clang-tidy/objc/DeallocInCategoryCheck.cpp
+++ b/clang-tools-extra/clang-tidy/objc/DeallocInCategoryCheck.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace objc {
+namespace clang::tidy::objc {
 
 void DeallocInCategoryCheck::registerMatchers(MatchFinder *Finder) {
   // Non-NSObject/NSProxy-derived objects may not have -dealloc as a special
@@ -37,6 +35,4 @@
       << CID;
 }
 
-} // namespace objc
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::objc
diff --git a/clang-tools-extra/clang-tidy/objc/ForbiddenSubclassingCheck.cpp b/clang-tools-extra/clang-tidy/objc/ForbiddenSubclassingCheck.cpp
--- a/clang-tools-extra/clang-tidy/objc/ForbiddenSubclassingCheck.cpp
+++ b/clang-tools-extra/clang-tidy/objc/ForbiddenSubclassingCheck.cpp
@@ -15,9 +15,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace objc {
+namespace clang::tidy::objc {
 
 namespace {
 
@@ -80,6 +78,4 @@
       utils::options::serializeStringList(ForbiddenSuperClassNames));
 }
 
-} // namespace objc
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::objc
diff --git a/clang-tools-extra/clang-tidy/objc/MissingHashCheck.cpp b/clang-tools-extra/clang-tidy/objc/MissingHashCheck.cpp
--- a/clang-tools-extra/clang-tidy/objc/MissingHashCheck.cpp
+++ b/clang-tools-extra/clang-tidy/objc/MissingHashCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace objc {
+namespace clang::tidy::objc {
 
 namespace {
 
@@ -53,6 +51,4 @@
       << ID;
 }
 
-} // namespace objc
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::objc
diff --git a/clang-tools-extra/clang-tidy/objc/NSDateFormatterCheck.cpp b/clang-tools-extra/clang-tidy/objc/NSDateFormatterCheck.cpp
--- a/clang-tools-extra/clang-tidy/objc/NSDateFormatterCheck.cpp
+++ b/clang-tools-extra/clang-tidy/objc/NSDateFormatterCheck.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace objc {
+namespace clang::tidy::objc {
 
 void NSDateFormatterCheck::registerMatchers(MatchFinder *Finder) {
   // Adding matchers.
@@ -105,6 +103,4 @@
   }
 }
 
-} // namespace objc
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::objc
diff --git a/clang-tools-extra/clang-tidy/objc/NSInvocationArgumentLifetimeCheck.cpp b/clang-tools-extra/clang-tidy/objc/NSInvocationArgumentLifetimeCheck.cpp
--- a/clang-tools-extra/clang-tidy/objc/NSInvocationArgumentLifetimeCheck.cpp
+++ b/clang-tools-extra/clang-tidy/objc/NSInvocationArgumentLifetimeCheck.cpp
@@ -28,9 +28,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace objc {
+namespace clang::tidy::objc {
 namespace {
 
 static constexpr StringRef WeakText = "__weak";
@@ -142,6 +140,4 @@
     Diag << *Hint;
 }
 
-} // namespace objc
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::objc
diff --git a/clang-tools-extra/clang-tidy/objc/ObjCTidyModule.cpp b/clang-tools-extra/clang-tidy/objc/ObjCTidyModule.cpp
--- a/clang-tools-extra/clang-tidy/objc/ObjCTidyModule.cpp
+++ b/clang-tools-extra/clang-tidy/objc/ObjCTidyModule.cpp
@@ -21,8 +21,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
+namespace clang::tidy {
 namespace objc {
 
 class ObjCModule : public ClangTidyModule {
@@ -59,5 +58,4 @@
 // and thus register the ObjCModule.
 volatile int ObjCModuleAnchorSource = 0;
 
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy
diff --git a/clang-tools-extra/clang-tidy/objc/PropertyDeclarationCheck.cpp b/clang-tools-extra/clang-tidy/objc/PropertyDeclarationCheck.cpp
--- a/clang-tools-extra/clang-tidy/objc/PropertyDeclarationCheck.cpp
+++ b/clang-tools-extra/clang-tidy/objc/PropertyDeclarationCheck.cpp
@@ -18,9 +18,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace objc {
+namespace clang::tidy::objc {
 
 namespace {
 
@@ -133,6 +131,4 @@
       << generateFixItHint(MatchedDecl, StandardProperty);
 }
 
-}  // namespace objc
-}  // namespace tidy
-}  // namespace clang
+} // namespace clang::tidy::objc
diff --git a/clang-tools-extra/clang-tidy/objc/SuperSelfCheck.cpp b/clang-tools-extra/clang-tidy/objc/SuperSelfCheck.cpp
--- a/clang-tools-extra/clang-tidy/objc/SuperSelfCheck.cpp
+++ b/clang-tools-extra/clang-tidy/objc/SuperSelfCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace objc {
+namespace clang::tidy::objc {
 
 namespace {
 
@@ -104,6 +102,4 @@
                                        StringRef("[super init]"));
 }
 
-} // namespace objc
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::objc
diff --git a/clang-tools-extra/clang-tidy/openmp/ExceptionEscapeCheck.cpp b/clang-tools-extra/clang-tidy/openmp/ExceptionEscapeCheck.cpp
--- a/clang-tools-extra/clang-tidy/openmp/ExceptionEscapeCheck.cpp
+++ b/clang-tools-extra/clang-tidy/openmp/ExceptionEscapeCheck.cpp
@@ -17,9 +17,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace openmp {
+namespace clang::tidy::openmp {
 
 ExceptionEscapeCheck::ExceptionEscapeCheck(StringRef Name,
                                            ClangTidyContext *Context)
@@ -71,6 +69,4 @@
       << getOpenMPDirectiveName(Directive->getDirectiveKind());
 }
 
-} // namespace openmp
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::openmp
diff --git a/clang-tools-extra/clang-tidy/openmp/OpenMPTidyModule.cpp b/clang-tools-extra/clang-tidy/openmp/OpenMPTidyModule.cpp
--- a/clang-tools-extra/clang-tidy/openmp/OpenMPTidyModule.cpp
+++ b/clang-tools-extra/clang-tidy/openmp/OpenMPTidyModule.cpp
@@ -12,8 +12,7 @@
 #include "ExceptionEscapeCheck.h"
 #include "UseDefaultNoneCheck.h"
 
-namespace clang {
-namespace tidy {
+namespace clang::tidy {
 namespace openmp {
 
 /// This module is for OpenMP-specific checks.
@@ -37,5 +36,4 @@
 // and thus register the OpenMPModule.
 volatile int OpenMPModuleAnchorSource = 0;
 
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy
diff --git a/clang-tools-extra/clang-tidy/openmp/UseDefaultNoneCheck.cpp b/clang-tools-extra/clang-tidy/openmp/UseDefaultNoneCheck.cpp
--- a/clang-tools-extra/clang-tidy/openmp/UseDefaultNoneCheck.cpp
+++ b/clang-tools-extra/clang-tidy/openmp/UseDefaultNoneCheck.cpp
@@ -17,9 +17,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace openmp {
+namespace clang::tidy::openmp {
 
 void UseDefaultNoneCheck::registerMatchers(MatchFinder *Finder) {
   Finder->addMatcher(
@@ -55,6 +53,4 @@
       << getOpenMPDirectiveName(Directive->getDirectiveKind());
 }
 
-} // namespace openmp
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::openmp
diff --git a/clang-tools-extra/clang-tidy/performance/FasterStringFindCheck.cpp b/clang-tools-extra/clang-tidy/performance/FasterStringFindCheck.cpp
--- a/clang-tools-extra/clang-tidy/performance/FasterStringFindCheck.cpp
+++ b/clang-tools-extra/clang-tidy/performance/FasterStringFindCheck.cpp
@@ -15,9 +15,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace performance {
+namespace clang::tidy::performance {
 
 namespace {
 
@@ -95,6 +93,4 @@
              *Replacement);
 }
 
-} // namespace performance
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::performance
diff --git a/clang-tools-extra/clang-tidy/performance/ForRangeCopyCheck.cpp b/clang-tools-extra/clang-tidy/performance/ForRangeCopyCheck.cpp
--- a/clang-tools-extra/clang-tidy/performance/ForRangeCopyCheck.cpp
+++ b/clang-tools-extra/clang-tidy/performance/ForRangeCopyCheck.cpp
@@ -18,9 +18,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace performance {
+namespace clang::tidy::performance {
 
 ForRangeCopyCheck::ForRangeCopyCheck(StringRef Name, ClangTidyContext *Context)
     : ClangTidyCheck(Name, Context),
@@ -132,6 +130,4 @@
   return false;
 }
 
-} // namespace performance
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::performance
diff --git a/clang-tools-extra/clang-tidy/performance/ImplicitConversionInLoopCheck.cpp b/clang-tools-extra/clang-tidy/performance/ImplicitConversionInLoopCheck.cpp
--- a/clang-tools-extra/clang-tidy/performance/ImplicitConversionInLoopCheck.cpp
+++ b/clang-tools-extra/clang-tidy/performance/ImplicitConversionInLoopCheck.cpp
@@ -16,9 +16,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace performance {
+namespace clang::tidy::performance {
 
 // Checks if the stmt is a ImplicitCastExpr with a CastKind that is not a NoOp.
 // The subtlety is that in some cases (user defined conversions), we can
@@ -101,6 +99,4 @@
   diag(VD->getBeginLoc(), Message) << VD << ConstRefType;
 }
 
-} // namespace performance
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::performance
diff --git a/clang-tools-extra/clang-tidy/performance/InefficientAlgorithmCheck.cpp b/clang-tools-extra/clang-tidy/performance/InefficientAlgorithmCheck.cpp
--- a/clang-tools-extra/clang-tidy/performance/InefficientAlgorithmCheck.cpp
+++ b/clang-tools-extra/clang-tidy/performance/InefficientAlgorithmCheck.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace performance {
+namespace clang::tidy::performance {
 
 static bool areTypesCompatible(QualType Left, QualType Right) {
   if (const auto *LeftRefType = Left->getAs<ReferenceType>())
@@ -148,6 +146,4 @@
       << Hint;
 }
 
-} // namespace performance
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::performance
diff --git a/clang-tools-extra/clang-tidy/performance/InefficientStringConcatenationCheck.cpp b/clang-tools-extra/clang-tidy/performance/InefficientStringConcatenationCheck.cpp
--- a/clang-tools-extra/clang-tidy/performance/InefficientStringConcatenationCheck.cpp
+++ b/clang-tools-extra/clang-tidy/performance/InefficientStringConcatenationCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace performance {
+namespace clang::tidy::performance {
 
 void InefficientStringConcatenationCheck::storeOptions(
     ClangTidyOptions::OptionMap &Opts) {
@@ -79,6 +77,4 @@
     diag(PlusOperator->getExprLoc(), DiagMsg);
 }
 
-} // namespace performance
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::performance
diff --git a/clang-tools-extra/clang-tidy/performance/InefficientVectorOperationCheck.cpp b/clang-tools-extra/clang-tidy/performance/InefficientVectorOperationCheck.cpp
--- a/clang-tools-extra/clang-tidy/performance/InefficientVectorOperationCheck.cpp
+++ b/clang-tools-extra/clang-tidy/performance/InefficientVectorOperationCheck.cpp
@@ -15,9 +15,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace performance {
+namespace clang::tidy::performance {
 
 namespace {
 
@@ -273,6 +271,4 @@
   }
 }
 
-} // namespace performance
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::performance
diff --git a/clang-tools-extra/clang-tidy/performance/MoveConstArgCheck.cpp b/clang-tools-extra/clang-tidy/performance/MoveConstArgCheck.cpp
--- a/clang-tools-extra/clang-tidy/performance/MoveConstArgCheck.cpp
+++ b/clang-tools-extra/clang-tidy/performance/MoveConstArgCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace performance {
+namespace clang::tidy::performance {
 
 static void replaceCallWithArg(const CallExpr *Call, DiagnosticBuilder &Diag,
                                const SourceManager &SM,
@@ -206,6 +204,4 @@
   }
 }
 
-} // namespace performance
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::performance
diff --git a/clang-tools-extra/clang-tidy/performance/MoveConstructorInitCheck.cpp b/clang-tools-extra/clang-tidy/performance/MoveConstructorInitCheck.cpp
--- a/clang-tools-extra/clang-tidy/performance/MoveConstructorInitCheck.cpp
+++ b/clang-tools-extra/clang-tidy/performance/MoveConstructorInitCheck.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace performance {
+namespace clang::tidy::performance {
 
 MoveConstructorInitCheck::MoveConstructorInitCheck(StringRef Name,
                                                    ClangTidyContext *Context)
@@ -84,6 +82,4 @@
   }
 }
 
-} // namespace performance
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::performance
diff --git a/clang-tools-extra/clang-tidy/performance/NoAutomaticMoveCheck.cpp b/clang-tools-extra/clang-tidy/performance/NoAutomaticMoveCheck.cpp
--- a/clang-tools-extra/clang-tidy/performance/NoAutomaticMoveCheck.cpp
+++ b/clang-tools-extra/clang-tidy/performance/NoAutomaticMoveCheck.cpp
@@ -14,9 +14,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace performance {
+namespace clang::tidy::performance {
 
 NoAutomaticMoveCheck::NoAutomaticMoveCheck(StringRef Name,
                                            ClangTidyContext *Context)
@@ -67,6 +65,4 @@
                 utils::options::serializeStringList(AllowedTypes));
 }
 
-} // namespace performance
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::performance
diff --git a/clang-tools-extra/clang-tidy/performance/NoIntToPtrCheck.cpp b/clang-tools-extra/clang-tidy/performance/NoIntToPtrCheck.cpp
--- a/clang-tools-extra/clang-tidy/performance/NoIntToPtrCheck.cpp
+++ b/clang-tools-extra/clang-tidy/performance/NoIntToPtrCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace performance {
+namespace clang::tidy::performance {
 
 void NoIntToPtrCheck::registerMatchers(MatchFinder *Finder) {
   Finder->addMatcher(castExpr(hasCastKind(CK_IntegralToPointer),
@@ -29,6 +27,4 @@
        "integer to pointer cast pessimizes optimization opportunities");
 }
 
-} // namespace performance
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::performance
diff --git a/clang-tools-extra/clang-tidy/performance/NoexceptMoveConstructorCheck.cpp b/clang-tools-extra/clang-tidy/performance/NoexceptMoveConstructorCheck.cpp
--- a/clang-tools-extra/clang-tidy/performance/NoexceptMoveConstructorCheck.cpp
+++ b/clang-tools-extra/clang-tidy/performance/NoexceptMoveConstructorCheck.cpp
@@ -14,9 +14,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace performance {
+namespace clang::tidy::performance {
 
 void NoexceptMoveConstructorCheck::registerMatchers(MatchFinder *Finder) {
   Finder->addMatcher(
@@ -77,6 +75,4 @@
   }
 }
 
-} // namespace performance
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::performance
diff --git a/clang-tools-extra/clang-tidy/performance/PerformanceTidyModule.cpp b/clang-tools-extra/clang-tidy/performance/PerformanceTidyModule.cpp
--- a/clang-tools-extra/clang-tidy/performance/PerformanceTidyModule.cpp
+++ b/clang-tools-extra/clang-tidy/performance/PerformanceTidyModule.cpp
@@ -25,8 +25,7 @@
 #include "UnnecessaryCopyInitialization.h"
 #include "UnnecessaryValueParamCheck.h"
 
-namespace clang {
-namespace tidy {
+namespace clang::tidy {
 namespace performance {
 
 class PerformanceModule : public ClangTidyModule {
@@ -74,5 +73,4 @@
 // and thus register the PerformanceModule.
 volatile int PerformanceModuleAnchorSource = 0;
 
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy
diff --git a/clang-tools-extra/clang-tidy/performance/TriviallyDestructibleCheck.cpp b/clang-tools-extra/clang-tidy/performance/TriviallyDestructibleCheck.cpp
--- a/clang-tools-extra/clang-tidy/performance/TriviallyDestructibleCheck.cpp
+++ b/clang-tools-extra/clang-tidy/performance/TriviallyDestructibleCheck.cpp
@@ -16,9 +16,7 @@
 using namespace clang::ast_matchers::internal;
 using namespace clang::tidy::matchers;
 
-namespace clang {
-namespace tidy {
-namespace performance {
+namespace clang::tidy::performance {
 
 namespace {
 
@@ -74,6 +72,4 @@
        DiagnosticIDs::Note);
 }
 
-} // namespace performance
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::performance
diff --git a/clang-tools-extra/clang-tidy/performance/TypePromotionInMathFnCheck.cpp b/clang-tools-extra/clang-tidy/performance/TypePromotionInMathFnCheck.cpp
--- a/clang-tools-extra/clang-tidy/performance/TypePromotionInMathFnCheck.cpp
+++ b/clang-tools-extra/clang-tidy/performance/TypePromotionInMathFnCheck.cpp
@@ -15,9 +15,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace performance {
+namespace clang::tidy::performance {
 
 namespace {
 AST_MATCHER_P(Type, isBuiltinType, BuiltinType::Kind, Kind) {
@@ -195,6 +193,4 @@
         "<cmath>");
 }
 
-} // namespace performance
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::performance
diff --git a/clang-tools-extra/clang-tidy/performance/UnnecessaryCopyInitialization.cpp b/clang-tools-extra/clang-tidy/performance/UnnecessaryCopyInitialization.cpp
--- a/clang-tools-extra/clang-tidy/performance/UnnecessaryCopyInitialization.cpp
+++ b/clang-tools-extra/clang-tidy/performance/UnnecessaryCopyInitialization.cpp
@@ -16,9 +16,7 @@
 #include "clang/Basic/Diagnostic.h"
 #include <optional>
 
-namespace clang {
-namespace tidy {
-namespace performance {
+namespace clang::tidy::performance {
 namespace {
 
 using namespace ::clang::ast_matchers;
@@ -370,6 +368,4 @@
                 utils::options::serializeStringList(ExcludedContainerTypes));
 }
 
-} // namespace performance
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::performance
diff --git a/clang-tools-extra/clang-tidy/performance/UnnecessaryValueParamCheck.cpp b/clang-tools-extra/clang-tidy/performance/UnnecessaryValueParamCheck.cpp
--- a/clang-tools-extra/clang-tidy/performance/UnnecessaryValueParamCheck.cpp
+++ b/clang-tools-extra/clang-tidy/performance/UnnecessaryValueParamCheck.cpp
@@ -20,9 +20,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace performance {
+namespace clang::tidy::performance {
 
 namespace {
 
@@ -193,6 +191,4 @@
               SM.getFileID(CopyArgument.getBeginLoc()), "<utility>");
 }
 
-} // namespace performance
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::performance
diff --git a/clang-tools-extra/clang-tidy/plugin/ClangTidyPlugin.cpp b/clang-tools-extra/clang-tidy/plugin/ClangTidyPlugin.cpp
--- a/clang-tools-extra/clang-tidy/plugin/ClangTidyPlugin.cpp
+++ b/clang-tools-extra/clang-tidy/plugin/ClangTidyPlugin.cpp
@@ -14,8 +14,7 @@
 #include "clang/Frontend/FrontendPluginRegistry.h"
 #include "clang/Frontend/MultiplexConsumer.h"
 
-namespace clang {
-namespace tidy {
+namespace clang::tidy {
 
 /// The core clang tidy plugin action. This just provides the AST consumer and
 /// command line flag parsing for using clang-tidy as a clang plugin.
@@ -75,8 +74,7 @@
 private:
   std::unique_ptr<ClangTidyContext> Context;
 };
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy
 
 // This anchor is used to force the linker to link in the generated object file
 // and thus register the clang-tidy plugin.
diff --git a/clang-tools-extra/clang-tidy/portability/PortabilityTidyModule.cpp b/clang-tools-extra/clang-tidy/portability/PortabilityTidyModule.cpp
--- a/clang-tools-extra/clang-tidy/portability/PortabilityTidyModule.cpp
+++ b/clang-tools-extra/clang-tidy/portability/PortabilityTidyModule.cpp
@@ -13,8 +13,7 @@
 #include "SIMDIntrinsicsCheck.h"
 #include "StdAllocatorConstCheck.h"
 
-namespace clang {
-namespace tidy {
+namespace clang::tidy {
 namespace portability {
 
 class PortabilityModule : public ClangTidyModule {
@@ -39,5 +38,4 @@
 // and thus register the PortabilityModule.
 volatile int PortabilityModuleAnchorSource = 0;
 
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy
diff --git a/clang-tools-extra/clang-tidy/portability/RestrictSystemIncludesCheck.cpp b/clang-tools-extra/clang-tidy/portability/RestrictSystemIncludesCheck.cpp
--- a/clang-tools-extra/clang-tidy/portability/RestrictSystemIncludesCheck.cpp
+++ b/clang-tools-extra/clang-tidy/portability/RestrictSystemIncludesCheck.cpp
@@ -16,9 +16,7 @@
 #include "llvm/Support/Path.h"
 #include <cstring>
 
-namespace clang {
-namespace tidy {
-namespace portability {
+namespace clang::tidy::portability {
 
 void RestrictedIncludesPPCallbacks::InclusionDirective(
     SourceLocation HashLoc, const Token &IncludeTok, StringRef FileName,
@@ -75,6 +73,4 @@
   Options.store(Opts, "Includes", AllowedIncludes);
 }
 
-} // namespace portability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::portability
diff --git a/clang-tools-extra/clang-tidy/portability/SIMDIntrinsicsCheck.cpp b/clang-tools-extra/clang-tidy/portability/SIMDIntrinsicsCheck.cpp
--- a/clang-tools-extra/clang-tidy/portability/SIMDIntrinsicsCheck.cpp
+++ b/clang-tools-extra/clang-tidy/portability/SIMDIntrinsicsCheck.cpp
@@ -17,9 +17,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace portability {
+namespace clang::tidy::portability {
 
 namespace {
 
@@ -146,6 +144,4 @@
   }
 }
 
-} // namespace portability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::portability
diff --git a/clang-tools-extra/clang-tidy/portability/StdAllocatorConstCheck.cpp b/clang-tools-extra/clang-tidy/portability/StdAllocatorConstCheck.cpp
--- a/clang-tools-extra/clang-tidy/portability/StdAllocatorConstCheck.cpp
+++ b/clang-tools-extra/clang-tidy/portability/StdAllocatorConstCheck.cpp
@@ -11,9 +11,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace portability {
+namespace clang::tidy::portability {
 
 void StdAllocatorConstCheck::registerMatchers(MatchFinder *Finder) {
   // Match std::allocator<const T>.
@@ -66,6 +64,4 @@
        "libraries");
 }
 
-} // namespace portability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::portability
diff --git a/clang-tools-extra/clang-tidy/readability/AvoidConstParamsInDecls.cpp b/clang-tools-extra/clang-tidy/readability/AvoidConstParamsInDecls.cpp
--- a/clang-tools-extra/clang-tidy/readability/AvoidConstParamsInDecls.cpp
+++ b/clang-tools-extra/clang-tidy/readability/AvoidConstParamsInDecls.cpp
@@ -14,9 +14,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 namespace {
 
 SourceRange getTypeRange(const ParmVarDecl &Param) {
@@ -89,6 +87,4 @@
       CharSourceRange::getTokenRange(Tok->getLocation(), Tok->getLocation()));
 }
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
diff --git a/clang-tools-extra/clang-tidy/readability/BracesAroundStatementsCheck.cpp b/clang-tools-extra/clang-tidy/readability/BracesAroundStatementsCheck.cpp
--- a/clang-tools-extra/clang-tidy/readability/BracesAroundStatementsCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/BracesAroundStatementsCheck.cpp
@@ -14,9 +14,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 static tok::TokenKind getTokenKind(SourceLocation Loc, const SourceManager &SM,
                                    const ASTContext *Context) {
@@ -269,6 +267,4 @@
   ForceBracesStmts.clear();
 }
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
diff --git a/clang-tools-extra/clang-tidy/readability/ConstReturnTypeCheck.cpp b/clang-tools-extra/clang-tidy/readability/ConstReturnTypeCheck.cpp
--- a/clang-tools-extra/clang-tidy/readability/ConstReturnTypeCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/ConstReturnTypeCheck.cpp
@@ -16,9 +16,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 // Finds the location of the qualifying `const` token in the `FunctionDecl`'s
 // return type. Returns `std::nullopt` when the return type is not
@@ -157,6 +155,4 @@
     diag(Loc, "could not transform this declaration", DiagnosticIDs::Note);
 }
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
diff --git a/clang-tools-extra/clang-tidy/readability/ContainerContainsCheck.cpp b/clang-tools-extra/clang-tidy/readability/ContainerContainsCheck.cpp
--- a/clang-tools-extra/clang-tidy/readability/ContainerContainsCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/ContainerContainsCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 void ContainerContainsCheck::registerMatchers(MatchFinder *Finder) {
   const auto SupportedContainers = hasType(
@@ -137,6 +135,4 @@
       CallEnd.getLocWithOffset(1), ComparisonEnd.getLocWithOffset(1)));
 }
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
diff --git a/clang-tools-extra/clang-tidy/readability/ContainerDataPointerCheck.cpp b/clang-tools-extra/clang-tidy/readability/ContainerDataPointerCheck.cpp
--- a/clang-tools-extra/clang-tidy/readability/ContainerDataPointerCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/ContainerDataPointerCheck.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 constexpr llvm::StringLiteral ContainerExprName = "container-expr";
 constexpr llvm::StringLiteral DerefContainerExprName = "deref-container-expr";
@@ -114,6 +112,4 @@
        "the address of the 0-th element")
       << Hint;
 }
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
diff --git a/clang-tools-extra/clang-tidy/readability/ContainerSizeEmptyCheck.cpp b/clang-tools-extra/clang-tidy/readability/ContainerSizeEmptyCheck.cpp
--- a/clang-tools-extra/clang-tidy/readability/ContainerSizeEmptyCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/ContainerSizeEmptyCheck.cpp
@@ -90,8 +90,7 @@
   return Node->isIntegralType(Finder->getASTContext());
 }
 } // namespace ast_matchers
-namespace tidy {
-namespace readability {
+namespace tidy::readability {
 
 using utils::isBinaryOrTernary;
 
@@ -328,6 +327,5 @@
       << Container;
 }
 
-} // namespace readability
-} // namespace tidy
+} // namespace tidy::readability
 } // namespace clang
diff --git a/clang-tools-extra/clang-tidy/readability/ConvertMemberFunctionsToStatic.cpp b/clang-tools-extra/clang-tidy/readability/ConvertMemberFunctionsToStatic.cpp
--- a/clang-tools-extra/clang-tidy/readability/ConvertMemberFunctionsToStatic.cpp
+++ b/clang-tools-extra/clang-tidy/readability/ConvertMemberFunctionsToStatic.cpp
@@ -16,9 +16,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 AST_MATCHER(CXXMethodDecl, isStatic) { return Node.isStatic(); }
 
@@ -167,6 +165,4 @@
   Diag << FixItHint::CreateInsertion(Declaration->getBeginLoc(), "static ");
 }
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
diff --git a/clang-tools-extra/clang-tidy/readability/DeleteNullPointerCheck.cpp b/clang-tools-extra/clang-tidy/readability/DeleteNullPointerCheck.cpp
--- a/clang-tools-extra/clang-tidy/readability/DeleteNullPointerCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/DeleteNullPointerCheck.cpp
@@ -14,9 +14,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 void DeleteNullPointerCheck::registerMatchers(MatchFinder *Finder) {
   const auto DeleteExpr =
@@ -73,6 +71,4 @@
   }
 }
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
diff --git a/clang-tools-extra/clang-tidy/readability/DuplicateIncludeCheck.cpp b/clang-tools-extra/clang-tidy/readability/DuplicateIncludeCheck.cpp
--- a/clang-tools-extra/clang-tidy/readability/DuplicateIncludeCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/DuplicateIncludeCheck.cpp
@@ -13,9 +13,7 @@
 #include "llvm/ADT/SmallVector.h"
 #include <memory>
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 static SourceLocation advanceBeyondCurrentLine(const SourceManager &SM,
                                                SourceLocation Start,
@@ -111,6 +109,4 @@
   PP->addPPCallbacks(std::make_unique<DuplicateIncludeCallbacks>(*this, SM));
 }
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
diff --git a/clang-tools-extra/clang-tidy/readability/ElseAfterReturnCheck.cpp b/clang-tools-extra/clang-tidy/readability/ElseAfterReturnCheck.cpp
--- a/clang-tools-extra/clang-tidy/readability/ElseAfterReturnCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/ElseAfterReturnCheck.cpp
@@ -16,9 +16,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 namespace {
 
@@ -324,6 +322,4 @@
   removeElseAndBrackets(Diag, *Result.Context, Else, ElseLoc);
 }
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
diff --git a/clang-tools-extra/clang-tidy/readability/FunctionCognitiveComplexityCheck.cpp b/clang-tools-extra/clang-tidy/readability/FunctionCognitiveComplexityCheck.cpp
--- a/clang-tools-extra/clang-tidy/readability/FunctionCognitiveComplexityCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/FunctionCognitiveComplexityCheck.cpp
@@ -33,9 +33,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 namespace {
 
 struct CognitiveComplexity final {
@@ -562,6 +560,4 @@
   }
 }
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
diff --git a/clang-tools-extra/clang-tidy/readability/FunctionSizeCheck.cpp b/clang-tools-extra/clang-tidy/readability/FunctionSizeCheck.cpp
--- a/clang-tools-extra/clang-tidy/readability/FunctionSizeCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/FunctionSizeCheck.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 namespace {
 
 class FunctionASTVisitor : public RecursiveASTVisitor<FunctionASTVisitor> {
@@ -221,6 +219,4 @@
   }
 }
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
diff --git a/clang-tools-extra/clang-tidy/readability/IdentifierLengthCheck.cpp b/clang-tools-extra/clang-tidy/readability/IdentifierLengthCheck.cpp
--- a/clang-tools-extra/clang-tidy/readability/IdentifierLengthCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/IdentifierLengthCheck.cpp
@@ -14,9 +14,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 const unsigned DefaultMinimumVariableNameLength = 3;
 const unsigned DefaultMinimumLoopCounterNameLength = 2;
@@ -151,6 +149,4 @@
   }
 }
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
diff --git a/clang-tools-extra/clang-tidy/readability/IdentifierNamingCheck.cpp b/clang-tools-extra/clang-tidy/readability/IdentifierNamingCheck.cpp
--- a/clang-tools-extra/clang-tidy/readability/IdentifierNamingCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/IdentifierNamingCheck.cpp
@@ -28,8 +28,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
+namespace clang::tidy {
 
 llvm::ArrayRef<
     std::pair<readability::IdentifierNamingCheck::CaseType, StringRef>>
@@ -1451,5 +1450,4 @@
 }
 
 } // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy
diff --git a/clang-tools-extra/clang-tidy/readability/ImplicitBoolConversionCheck.cpp b/clang-tools-extra/clang-tidy/readability/ImplicitBoolConversionCheck.cpp
--- a/clang-tools-extra/clang-tidy/readability/ImplicitBoolConversionCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/ImplicitBoolConversionCheck.cpp
@@ -15,9 +15,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 namespace {
 
@@ -391,6 +389,4 @@
   }
 }
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
diff --git a/clang-tools-extra/clang-tidy/readability/InconsistentDeclarationParameterNameCheck.cpp b/clang-tools-extra/clang-tidy/readability/InconsistentDeclarationParameterNameCheck.cpp
--- a/clang-tools-extra/clang-tidy/readability/InconsistentDeclarationParameterNameCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/InconsistentDeclarationParameterNameCheck.cpp
@@ -15,9 +15,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 namespace {
 
@@ -350,6 +348,4 @@
   }
 }
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
diff --git a/clang-tools-extra/clang-tidy/readability/IsolateDeclarationCheck.cpp b/clang-tools-extra/clang-tidy/readability/IsolateDeclarationCheck.cpp
--- a/clang-tools-extra/clang-tidy/readability/IsolateDeclarationCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/IsolateDeclarationCheck.cpp
@@ -14,9 +14,7 @@
 using namespace clang::ast_matchers;
 using namespace clang::tidy::utils::lexer;
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 namespace {
 AST_MATCHER(DeclStmt, isSingleDecl) { return Node.isSingleDecl(); }
@@ -273,6 +271,4 @@
   Diag << FixItHint::CreateReplacement(WholeDecl->getSourceRange(),
                                        Replacement);
 }
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
diff --git a/clang-tools-extra/clang-tidy/readability/MagicNumbersCheck.cpp b/clang-tools-extra/clang-tidy/readability/MagicNumbersCheck.cpp
--- a/clang-tools-extra/clang-tidy/readability/MagicNumbersCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/MagicNumbersCheck.cpp
@@ -54,8 +54,7 @@
                       });
 }
 
-namespace tidy {
-namespace readability {
+namespace tidy::readability {
 
 const char DefaultIgnoredIntegerValues[] = "1;2;3;4;";
 const char DefaultIgnoredFloatingPointValues[] = "1.0;100.0;";
@@ -225,6 +224,5 @@
                       });
 }
 
-} // namespace readability
-} // namespace tidy
+} // namespace tidy::readability
 } // namespace clang
diff --git a/clang-tools-extra/clang-tidy/readability/MakeMemberFunctionConstCheck.cpp b/clang-tools-extra/clang-tidy/readability/MakeMemberFunctionConstCheck.cpp
--- a/clang-tools-extra/clang-tidy/readability/MakeMemberFunctionConstCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/MakeMemberFunctionConstCheck.cpp
@@ -15,9 +15,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 AST_MATCHER(CXXMethodDecl, isStatic) { return Node.isStatic(); }
 
@@ -267,6 +265,4 @@
   }
 }
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
diff --git a/clang-tools-extra/clang-tidy/readability/MisleadingIndentationCheck.cpp b/clang-tools-extra/clang-tidy/readability/MisleadingIndentationCheck.cpp
--- a/clang-tools-extra/clang-tidy/readability/MisleadingIndentationCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/MisleadingIndentationCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 static const IfStmt *getPrecedingIf(const SourceManager &SM,
                                     ASTContext *Context, const IfStmt *If) {
@@ -121,6 +119,4 @@
     missingBracesCheck(*Result.SourceManager, CStmt);
 }
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
diff --git a/clang-tools-extra/clang-tidy/readability/MisplacedArrayIndexCheck.cpp b/clang-tools-extra/clang-tidy/readability/MisplacedArrayIndexCheck.cpp
--- a/clang-tools-extra/clang-tidy/readability/MisplacedArrayIndexCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/MisplacedArrayIndexCheck.cpp
@@ -14,9 +14,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 void MisplacedArrayIndexCheck::registerMatchers(MatchFinder *Finder) {
   Finder->addMatcher(
@@ -52,6 +50,4 @@
       ArraySubscriptE->getRHS()->getSourceRange(), LText);
 }
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
diff --git a/clang-tools-extra/clang-tidy/readability/NamedParameterCheck.cpp b/clang-tools-extra/clang-tidy/readability/NamedParameterCheck.cpp
--- a/clang-tools-extra/clang-tidy/readability/NamedParameterCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/NamedParameterCheck.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 void NamedParameterCheck::registerMatchers(ast_matchers::MatchFinder *Finder) {
   Finder->addMatcher(functionDecl().bind("decl"), this);
@@ -117,6 +115,4 @@
   }
 }
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
diff --git a/clang-tools-extra/clang-tidy/readability/NamespaceCommentCheck.cpp b/clang-tools-extra/clang-tidy/readability/NamespaceCommentCheck.cpp
--- a/clang-tools-extra/clang-tidy/readability/NamespaceCommentCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/NamespaceCommentCheck.cpp
@@ -18,9 +18,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 NamespaceCommentCheck::NamespaceCommentCheck(StringRef Name,
                                              ClangTidyContext *Context)
@@ -204,6 +202,4 @@
       << NamespaceNameForDiag;
 }
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
diff --git a/clang-tools-extra/clang-tidy/readability/NonConstParameterCheck.cpp b/clang-tools-extra/clang-tidy/readability/NonConstParameterCheck.cpp
--- a/clang-tools-extra/clang-tidy/readability/NonConstParameterCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/NonConstParameterCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 void NonConstParameterCheck::registerMatchers(MatchFinder *Finder) {
   // Add parameters to Parameters.
@@ -233,6 +231,4 @@
   }
 }
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
diff --git a/clang-tools-extra/clang-tidy/readability/QualifiedAutoCheck.cpp b/clang-tools-extra/clang-tidy/readability/QualifiedAutoCheck.cpp
--- a/clang-tools-extra/clang-tidy/readability/QualifiedAutoCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/QualifiedAutoCheck.cpp
@@ -14,9 +14,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 namespace {
 
@@ -286,6 +284,4 @@
   }
 }
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
diff --git a/clang-tools-extra/clang-tidy/readability/ReadabilityTidyModule.cpp b/clang-tools-extra/clang-tidy/readability/ReadabilityTidyModule.cpp
--- a/clang-tools-extra/clang-tidy/readability/ReadabilityTidyModule.cpp
+++ b/clang-tools-extra/clang-tidy/readability/ReadabilityTidyModule.cpp
@@ -52,8 +52,7 @@
 #include "UppercaseLiteralSuffixCheck.h"
 #include "UseAnyOfAllOfCheck.h"
 
-namespace clang {
-namespace tidy {
+namespace clang::tidy {
 namespace readability {
 
 class ReadabilityModule : public ClangTidyModule {
@@ -156,5 +155,4 @@
 // and thus register the ReadabilityModule.
 volatile int ReadabilityModuleAnchorSource = 0;
 
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy
diff --git a/clang-tools-extra/clang-tidy/readability/RedundantAccessSpecifiersCheck.cpp b/clang-tools-extra/clang-tidy/readability/RedundantAccessSpecifiersCheck.cpp
--- a/clang-tools-extra/clang-tidy/readability/RedundantAccessSpecifiersCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/RedundantAccessSpecifiersCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 void RedundantAccessSpecifiersCheck::registerMatchers(MatchFinder *Finder) {
   Finder->addMatcher(
@@ -77,6 +75,4 @@
   }
 }
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
diff --git a/clang-tools-extra/clang-tidy/readability/RedundantControlFlowCheck.cpp b/clang-tools-extra/clang-tidy/readability/RedundantControlFlowCheck.cpp
--- a/clang-tools-extra/clang-tidy/readability/RedundantControlFlowCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/RedundantControlFlowCheck.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 namespace {
 
@@ -91,6 +89,4 @@
   diag(StmtRange.getBegin(), Diag) << FixItHint::CreateRemoval(RemovedRange);
 }
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
diff --git a/clang-tools-extra/clang-tidy/readability/RedundantDeclarationCheck.cpp b/clang-tools-extra/clang-tidy/readability/RedundantDeclarationCheck.cpp
--- a/clang-tools-extra/clang-tidy/readability/RedundantDeclarationCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/RedundantDeclarationCheck.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 AST_MATCHER(FunctionDecl, doesDeclarationForceExternallyVisibleDefinition) {
   return Node.doesDeclarationForceExternallyVisibleDefinition();
@@ -86,6 +84,4 @@
   }
   diag(Prev->getLocation(), "previously declared here", DiagnosticIDs::Note);
 }
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
diff --git a/clang-tools-extra/clang-tidy/readability/RedundantFunctionPtrDereferenceCheck.cpp b/clang-tools-extra/clang-tidy/readability/RedundantFunctionPtrDereferenceCheck.cpp
--- a/clang-tools-extra/clang-tidy/readability/RedundantFunctionPtrDereferenceCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/RedundantFunctionPtrDereferenceCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 void RedundantFunctionPtrDereferenceCheck::registerMatchers(MatchFinder *Finder) {
   Finder->addMatcher(
@@ -32,6 +30,4 @@
       << FixItHint::CreateRemoval(Operator->getOperatorLoc());
 }
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
diff --git a/clang-tools-extra/clang-tidy/readability/RedundantMemberInitCheck.cpp b/clang-tools-extra/clang-tidy/readability/RedundantMemberInitCheck.cpp
--- a/clang-tools-extra/clang-tidy/readability/RedundantMemberInitCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/RedundantMemberInitCheck.cpp
@@ -16,9 +16,7 @@
 using namespace clang::ast_matchers;
 using namespace clang::tidy::matchers;
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 void RedundantMemberInitCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {
   Options.store(Opts, "IgnoreBaseInCopyConstructors",
@@ -69,6 +67,4 @@
   }
 }
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
diff --git a/clang-tools-extra/clang-tidy/readability/RedundantPreprocessorCheck.cpp b/clang-tools-extra/clang-tidy/readability/RedundantPreprocessorCheck.cpp
--- a/clang-tools-extra/clang-tidy/readability/RedundantPreprocessorCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/RedundantPreprocessorCheck.cpp
@@ -12,9 +12,7 @@
 #include "clang/Lex/PPCallbacks.h"
 #include "clang/Lex/Preprocessor.h"
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 namespace {
 /// Information about an opening preprocessor directive.
@@ -104,6 +102,4 @@
       ::std::make_unique<RedundantPreprocessorCallbacks>(*this, *PP));
 }
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
diff --git a/clang-tools-extra/clang-tidy/readability/RedundantSmartptrGetCheck.cpp b/clang-tools-extra/clang-tidy/readability/RedundantSmartptrGetCheck.cpp
--- a/clang-tools-extra/clang-tidy/readability/RedundantSmartptrGetCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/RedundantSmartptrGetCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 namespace {
 internal::Matcher<Expr> callToGet(const internal::Matcher<Decl> &OnClass) {
@@ -172,6 +170,4 @@
       << FixItHint::CreateReplacement(SR, Replacement);
 }
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
diff --git a/clang-tools-extra/clang-tidy/readability/RedundantStringCStrCheck.cpp b/clang-tools-extra/clang-tidy/readability/RedundantStringCStrCheck.cpp
--- a/clang-tools-extra/clang-tidy/readability/RedundantStringCStrCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/RedundantStringCStrCheck.cpp
@@ -16,9 +16,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 namespace {
 
@@ -200,6 +198,4 @@
       << FixItHint::CreateReplacement(Call->getSourceRange(), ArgText);
 }
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
diff --git a/clang-tools-extra/clang-tidy/readability/RedundantStringInitCheck.cpp b/clang-tools-extra/clang-tidy/readability/RedundantStringInitCheck.cpp
--- a/clang-tools-extra/clang-tidy/readability/RedundantStringInitCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/RedundantStringInitCheck.cpp
@@ -15,9 +15,7 @@
 using namespace clang::ast_matchers;
 using namespace clang::tidy::matchers;
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 const char DefaultStringNames[] =
     "::std::basic_string_view;::std::basic_string";
@@ -162,6 +160,4 @@
   }
 }
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
diff --git a/clang-tools-extra/clang-tidy/readability/SimplifyBooleanExprCheck.cpp b/clang-tools-extra/clang-tidy/readability/SimplifyBooleanExprCheck.cpp
--- a/clang-tools-extra/clang-tidy/readability/SimplifyBooleanExprCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/SimplifyBooleanExprCheck.cpp
@@ -17,9 +17,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 namespace {
 
@@ -957,6 +955,4 @@
   Diag << Fixes;
   return true;
 }
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
diff --git a/clang-tools-extra/clang-tidy/readability/SimplifySubscriptExprCheck.cpp b/clang-tools-extra/clang-tidy/readability/SimplifySubscriptExprCheck.cpp
--- a/clang-tools-extra/clang-tidy/readability/SimplifySubscriptExprCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/SimplifySubscriptExprCheck.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 static const char KDefaultTypes[] =
     "::std::basic_string;::std::basic_string_view;::std::vector;::std::array";
@@ -66,6 +64,4 @@
   Options.store(Opts, "Types", utils::options::serializeStringList(Types));
 }
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
diff --git a/clang-tools-extra/clang-tidy/readability/StaticAccessedThroughInstanceCheck.cpp b/clang-tools-extra/clang-tidy/readability/StaticAccessedThroughInstanceCheck.cpp
--- a/clang-tools-extra/clang-tidy/readability/StaticAccessedThroughInstanceCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/StaticAccessedThroughInstanceCheck.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 static unsigned getNameSpecifierNestingLevel(const QualType &QType) {
   if (const ElaboratedType *ElType = QType->getAs<ElaboratedType>()) {
@@ -94,6 +92,4 @@
       BaseTypeName + "::");
 }
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
diff --git a/clang-tools-extra/clang-tidy/readability/StaticDefinitionInAnonymousNamespaceCheck.cpp b/clang-tools-extra/clang-tidy/readability/StaticDefinitionInAnonymousNamespaceCheck.cpp
--- a/clang-tools-extra/clang-tidy/readability/StaticDefinitionInAnonymousNamespaceCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/StaticDefinitionInAnonymousNamespaceCheck.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 void StaticDefinitionInAnonymousNamespaceCheck::registerMatchers(
     MatchFinder *Finder) {
@@ -60,6 +58,4 @@
   }
 }
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
diff --git a/clang-tools-extra/clang-tidy/readability/StringCompareCheck.cpp b/clang-tools-extra/clang-tidy/readability/StringCompareCheck.cpp
--- a/clang-tools-extra/clang-tidy/readability/StringCompareCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/StringCompareCheck.cpp
@@ -14,9 +14,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 static const StringRef CompareMessage = "do not use 'compare' to test equality "
                                         "of strings; use the string equality "
@@ -75,6 +73,4 @@
   // FIXME: Add fixit to fix the code for case one and two (match1).
 }
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
diff --git a/clang-tools-extra/clang-tidy/readability/SuspiciousCallArgumentCheck.cpp b/clang-tools-extra/clang-tidy/readability/SuspiciousCallArgumentCheck.cpp
--- a/clang-tools-extra/clang-tidy/readability/SuspiciousCallArgumentCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/SuspiciousCallArgumentCheck.cpp
@@ -17,9 +17,7 @@
 using namespace clang::ast_matchers;
 namespace optutils = clang::tidy::utils::options;
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 namespace {
 struct DefaultHeuristicConfiguration {
@@ -807,6 +805,4 @@
   llvm_unreachable("Unhandled heuristic kind");
 }
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
diff --git a/clang-tools-extra/clang-tidy/readability/UniqueptrDeleteReleaseCheck.cpp b/clang-tools-extra/clang-tidy/readability/UniqueptrDeleteReleaseCheck.cpp
--- a/clang-tools-extra/clang-tidy/readability/UniqueptrDeleteReleaseCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/UniqueptrDeleteReleaseCheck.cpp
@@ -15,9 +15,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 void UniqueptrDeleteReleaseCheck::storeOptions(
     ClangTidyOptions::OptionMap &Opts) {
@@ -81,6 +79,4 @@
   }
 }
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
diff --git a/clang-tools-extra/clang-tidy/readability/UppercaseLiteralSuffixCheck.cpp b/clang-tools-extra/clang-tidy/readability/UppercaseLiteralSuffixCheck.cpp
--- a/clang-tools-extra/clang-tidy/readability/UppercaseLiteralSuffixCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/UppercaseLiteralSuffixCheck.cpp
@@ -17,9 +17,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 namespace {
 
@@ -241,6 +239,4 @@
   checkBoundMatch<FloatingLiteralCheck>(Result);
 }
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
diff --git a/clang-tools-extra/clang-tidy/readability/UseAnyOfAllOfCheck.cpp b/clang-tools-extra/clang-tidy/readability/UseAnyOfAllOfCheck.cpp
--- a/clang-tools-extra/clang-tidy/readability/UseAnyOfAllOfCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/UseAnyOfAllOfCheck.cpp
@@ -37,8 +37,7 @@
 }
 } // namespace
 
-namespace tidy {
-namespace readability {
+namespace tidy::readability {
 
 void UseAnyOfAllOfCheck::registerMatchers(MatchFinder *Finder) {
   auto Returns = [](bool V) {
@@ -104,6 +103,5 @@
   }
 }
 
-} // namespace readability
-} // namespace tidy
+} // namespace tidy::readability
 } // namespace clang
diff --git a/clang-tools-extra/clang-tidy/rename_check.py b/clang-tools-extra/clang-tidy/rename_check.py
--- a/clang-tools-extra/clang-tidy/rename_check.py
+++ b/clang-tools-extra/clang-tidy/rename_check.py
@@ -308,8 +308,9 @@
     for filename in check_implementation_files:
       # Move check implementation to the directory of the new module.
       filename = fileRename(filename, old_module_path, new_module_path)
-      replaceInFileRegex(filename, 'namespace ' + old_module + '[^ \n]*',
-                         'namespace ' + new_namespace)
+      replaceInFileRegex(filename,
+                         'namespace clang::tidy::' + old_module + '[^ \n]*',
+                         'namespace clang::tidy::' + new_namespace)
 
   if (args.old_check_name == args.new_check_name):
     return
diff --git a/clang-tools-extra/clang-tidy/tool/ClangTidyMain.cpp b/clang-tools-extra/clang-tidy/tool/ClangTidyMain.cpp
--- a/clang-tools-extra/clang-tidy/tool/ClangTidyMain.cpp
+++ b/clang-tools-extra/clang-tidy/tool/ClangTidyMain.cpp
@@ -263,8 +263,7 @@
 )"),
                                   cl::init(false), cl::cat(ClangTidyCategory));
 
-namespace clang {
-namespace tidy {
+namespace clang::tidy {
 
 static void printStats(const ClangTidyStats &Stats) {
   if (Stats.errorsIgnored()) {
@@ -660,5 +659,4 @@
   return 0;
 }
 
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy
diff --git a/clang-tools-extra/clang-tidy/utils/ASTUtils.cpp b/clang-tools-extra/clang-tidy/utils/ASTUtils.cpp
--- a/clang-tools-extra/clang-tidy/utils/ASTUtils.cpp
+++ b/clang-tools-extra/clang-tidy/utils/ASTUtils.cpp
@@ -12,9 +12,7 @@
 #include "clang/ASTMatchers/ASTMatchers.h"
 #include "clang/Lex/Lexer.h"
 
-namespace clang {
-namespace tidy {
-namespace utils {
+namespace clang::tidy::utils {
 using namespace ast_matchers;
 
 const FunctionDecl *getSurroundingFunction(ASTContext &Context,
@@ -90,6 +88,4 @@
          !utils::rangeContainsMacroExpansion(Range, SM);
 }
 
-} // namespace utils
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::utils
diff --git a/clang-tools-extra/clang-tidy/utils/Aliasing.cpp b/clang-tools-extra/clang-tidy/utils/Aliasing.cpp
--- a/clang-tools-extra/clang-tidy/utils/Aliasing.cpp
+++ b/clang-tools-extra/clang-tidy/utils/Aliasing.cpp
@@ -11,9 +11,7 @@
 #include "clang/AST/Expr.h"
 #include "clang/AST/ExprCXX.h"
 
-namespace clang {
-namespace tidy {
-namespace utils {
+namespace clang::tidy::utils {
 
 /// Return whether \p S is a reference to the declaration of \p Var.
 static bool isAccessForVar(const Stmt *S, const VarDecl *Var) {
@@ -96,6 +94,4 @@
          refersToEnclosingLambdaCaptureByRef(Func, Var);
 }
 
-} // namespace utils
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::utils
diff --git a/clang-tools-extra/clang-tidy/utils/DeclRefExprUtils.cpp b/clang-tools-extra/clang-tidy/utils/DeclRefExprUtils.cpp
--- a/clang-tools-extra/clang-tidy/utils/DeclRefExprUtils.cpp
+++ b/clang-tools-extra/clang-tidy/utils/DeclRefExprUtils.cpp
@@ -12,10 +12,7 @@
 #include "clang/AST/DeclCXX.h"
 #include "clang/ASTMatchers/ASTMatchFinder.h"
 
-namespace clang {
-namespace tidy {
-namespace utils {
-namespace decl_ref_expr {
+namespace clang::tidy::utils::decl_ref_expr {
 
 using namespace ::clang::ast_matchers;
 using llvm::SmallPtrSet;
@@ -146,7 +143,4 @@
   return !Matches.empty();
 }
 
-} // namespace decl_ref_expr
-} // namespace utils
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::utils::decl_ref_expr
diff --git a/clang-tools-extra/clang-tidy/utils/ExceptionAnalyzer.cpp b/clang-tools-extra/clang-tidy/utils/ExceptionAnalyzer.cpp
--- a/clang-tools-extra/clang-tidy/utils/ExceptionAnalyzer.cpp
+++ b/clang-tools-extra/clang-tidy/utils/ExceptionAnalyzer.cpp
@@ -8,9 +8,7 @@
 
 #include "ExceptionAnalyzer.h"
 
-namespace clang {
-namespace tidy {
-namespace utils {
+namespace clang::tidy::utils {
 
 void ExceptionAnalyzer::ExceptionInfo::registerException(
     const Type *ExceptionType) {
@@ -274,7 +272,4 @@
   return analyzeDispatch(Stmt);
 }
 
-} // namespace utils
-} // namespace tidy
-
-} // namespace clang
+} // namespace clang::tidy::utils
diff --git a/clang-tools-extra/clang-tidy/utils/ExprSequence.cpp b/clang-tools-extra/clang-tidy/utils/ExprSequence.cpp
--- a/clang-tools-extra/clang-tidy/utils/ExprSequence.cpp
+++ b/clang-tools-extra/clang-tidy/utils/ExprSequence.cpp
@@ -10,9 +10,7 @@
 #include "clang/AST/ParentMapContext.h"
 #include <optional>
 
-namespace clang {
-namespace tidy {
-namespace utils {
+namespace clang::tidy::utils {
 
 // Returns the Stmt nodes that are parents of 'S', skipping any potential
 // intermediate non-Stmt nodes.
@@ -206,6 +204,4 @@
   return Map.lookup(S);
 }
 
-} // namespace utils
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::utils
diff --git a/clang-tools-extra/clang-tidy/utils/FileExtensionsUtils.cpp b/clang-tools-extra/clang-tidy/utils/FileExtensionsUtils.cpp
--- a/clang-tools-extra/clang-tidy/utils/FileExtensionsUtils.cpp
+++ b/clang-tools-extra/clang-tidy/utils/FileExtensionsUtils.cpp
@@ -11,9 +11,7 @@
 #include "llvm/Support/Path.h"
 #include <optional>
 
-namespace clang {
-namespace tidy {
-namespace utils {
+namespace clang::tidy::utils {
 
 bool isExpansionLocInHeaderFile(SourceLocation Loc, const SourceManager &SM,
                                 const FileExtensionsSet &HeaderFileExtensions) {
@@ -70,6 +68,4 @@
   return getFileExtension(FileName, FileExtensions).has_value();
 }
 
-} // namespace utils
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::utils
diff --git a/clang-tools-extra/clang-tidy/utils/FixItHintUtils.cpp b/clang-tools-extra/clang-tidy/utils/FixItHintUtils.cpp
--- a/clang-tools-extra/clang-tidy/utils/FixItHintUtils.cpp
+++ b/clang-tools-extra/clang-tidy/utils/FixItHintUtils.cpp
@@ -12,10 +12,7 @@
 #include "clang/AST/Type.h"
 #include <optional>
 
-namespace clang {
-namespace tidy {
-namespace utils {
-namespace fixit {
+namespace clang::tidy::utils::fixit {
 
 FixItHint changeVarDeclToReference(const VarDecl &Var, ASTContext &Context) {
   SourceLocation AmpLocation = Var.getLocation();
@@ -224,7 +221,4 @@
 
   return std::nullopt;
 }
-} // namespace fixit
-} // namespace utils
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::utils::fixit
diff --git a/clang-tools-extra/clang-tidy/utils/HeaderGuard.cpp b/clang-tools-extra/clang-tidy/utils/HeaderGuard.cpp
--- a/clang-tools-extra/clang-tidy/utils/HeaderGuard.cpp
+++ b/clang-tools-extra/clang-tidy/utils/HeaderGuard.cpp
@@ -13,9 +13,7 @@
 #include "clang/Tooling/Tooling.h"
 #include "llvm/Support/Path.h"
 
-namespace clang {
-namespace tidy {
-namespace utils {
+namespace clang::tidy::utils {
 
 /// canonicalize a path by removing ./ and ../ components.
 static std::string cleanPath(StringRef Path) {
@@ -298,6 +296,4 @@
 std::string HeaderGuardCheck::formatEndIf(StringRef HeaderGuard) {
   return "endif // " + HeaderGuard.str();
 }
-} // namespace utils
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::utils
diff --git a/clang-tools-extra/clang-tidy/utils/IncludeInserter.cpp b/clang-tools-extra/clang-tidy/utils/IncludeInserter.cpp
--- a/clang-tools-extra/clang-tidy/utils/IncludeInserter.cpp
+++ b/clang-tools-extra/clang-tidy/utils/IncludeInserter.cpp
@@ -12,9 +12,7 @@
 #include "clang/Lex/Token.h"
 #include <optional>
 
-namespace clang {
-namespace tidy {
-namespace utils {
+namespace clang::tidy::utils {
 
 class IncludeInserterCallback : public PPCallbacks {
 public:
@@ -99,6 +97,4 @@
   getOrCreate(FileID).addInclude(FileName, IsAngled, HashLocation, EndLocation);
 }
 
-} // namespace utils
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::utils
diff --git a/clang-tools-extra/clang-tidy/utils/IncludeSorter.cpp b/clang-tools-extra/clang-tidy/utils/IncludeSorter.cpp
--- a/clang-tools-extra/clang-tidy/utils/IncludeSorter.cpp
+++ b/clang-tools-extra/clang-tidy/utils/IncludeSorter.cpp
@@ -12,8 +12,7 @@
 #include <algorithm>
 #include <optional>
 
-namespace clang {
-namespace tidy {
+namespace clang::tidy {
 namespace utils {
 
 namespace {
@@ -233,5 +232,4 @@
                    {utils::IncludeSorter::IS_Google_ObjC, "google-objc"}};
   return ArrayRef(Mapping);
 }
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy
diff --git a/clang-tools-extra/clang-tidy/utils/LexerUtils.cpp b/clang-tools-extra/clang-tidy/utils/LexerUtils.cpp
--- a/clang-tools-extra/clang-tidy/utils/LexerUtils.cpp
+++ b/clang-tools-extra/clang-tidy/utils/LexerUtils.cpp
@@ -11,10 +11,7 @@
 #include "clang/Basic/SourceManager.h"
 #include <optional>
 
-namespace clang {
-namespace tidy {
-namespace utils {
-namespace lexer {
+namespace clang::tidy::utils::lexer {
 
 Token getPreviousToken(SourceLocation Location, const SourceManager &SM,
                        const LangOptions &LangOpts, bool SkipComments) {
@@ -215,7 +212,4 @@
   return S.getEndLoc();
 }
 
-} // namespace lexer
-} // namespace utils
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::utils::lexer
diff --git a/clang-tools-extra/clang-tidy/utils/NamespaceAliaser.cpp b/clang-tools-extra/clang-tidy/utils/NamespaceAliaser.cpp
--- a/clang-tools-extra/clang-tidy/utils/NamespaceAliaser.cpp
+++ b/clang-tools-extra/clang-tidy/utils/NamespaceAliaser.cpp
@@ -13,9 +13,7 @@
 #include "clang/ASTMatchers/ASTMatchers.h"
 #include "clang/Lex/Lexer.h"
 #include <optional>
-namespace clang {
-namespace tidy {
-namespace utils {
+namespace clang::tidy::utils {
 
 using namespace ast_matchers;
 
@@ -92,6 +90,4 @@
   return Namespace.str();
 }
 
-} // namespace utils
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::utils
diff --git a/clang-tools-extra/clang-tidy/utils/OptionsUtils.cpp b/clang-tools-extra/clang-tidy/utils/OptionsUtils.cpp
--- a/clang-tools-extra/clang-tidy/utils/OptionsUtils.cpp
+++ b/clang-tools-extra/clang-tidy/utils/OptionsUtils.cpp
@@ -9,10 +9,7 @@
 #include "OptionsUtils.h"
 #include "llvm/ADT/StringExtras.h"
 
-namespace clang {
-namespace tidy {
-namespace utils {
-namespace options {
+namespace clang::tidy::utils::options {
 
 static const char StringsDelimiter[] = ";";
 
@@ -63,7 +60,4 @@
   return llvm::join(Strings, StringsDelimiter);
 }
 
-} // namespace options
-} // namespace utils
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::utils::options
diff --git a/clang-tools-extra/clang-tidy/utils/RenamerClangTidyCheck.cpp b/clang-tools-extra/clang-tidy/utils/RenamerClangTidyCheck.cpp
--- a/clang-tools-extra/clang-tidy/utils/RenamerClangTidyCheck.cpp
+++ b/clang-tools-extra/clang-tidy/utils/RenamerClangTidyCheck.cpp
@@ -59,8 +59,7 @@
 
 } // namespace llvm
 
-namespace clang {
-namespace tidy {
+namespace clang::tidy {
 
 namespace {
 
@@ -563,5 +562,4 @@
   }
 }
 
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy
diff --git a/clang-tools-extra/clang-tidy/utils/TransformerClangTidyCheck.cpp b/clang-tools-extra/clang-tidy/utils/TransformerClangTidyCheck.cpp
--- a/clang-tools-extra/clang-tidy/utils/TransformerClangTidyCheck.cpp
+++ b/clang-tools-extra/clang-tidy/utils/TransformerClangTidyCheck.cpp
@@ -12,9 +12,7 @@
 #include "llvm/ADT/STLExtras.h"
 #include <optional>
 
-namespace clang {
-namespace tidy {
-namespace utils {
+namespace clang::tidy::utils {
 using transformer::RewriteRuleWith;
 
 #ifndef NDEBUG
@@ -157,6 +155,4 @@
   Options.store(Opts, "IncludeStyle", Inserter.getStyle());
 }
 
-} // namespace utils
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::utils
diff --git a/clang-tools-extra/clang-tidy/utils/TypeTraits.cpp b/clang-tools-extra/clang-tidy/utils/TypeTraits.cpp
--- a/clang-tools-extra/clang-tidy/utils/TypeTraits.cpp
+++ b/clang-tools-extra/clang-tidy/utils/TypeTraits.cpp
@@ -12,10 +12,7 @@
 #include "clang/ASTMatchers/ASTMatchFinder.h"
 #include <optional>
 
-namespace clang {
-namespace tidy {
-namespace utils {
-namespace type_traits {
+namespace clang::tidy::utils::type_traits {
 
 namespace {
 
@@ -162,7 +159,4 @@
          Record->hasNonTrivialMoveAssignment();
 }
 
-} // namespace type_traits
-} // namespace utils
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::utils::type_traits
diff --git a/clang-tools-extra/clang-tidy/utils/UsingInserter.cpp b/clang-tools-extra/clang-tidy/utils/UsingInserter.cpp
--- a/clang-tools-extra/clang-tidy/utils/UsingInserter.cpp
+++ b/clang-tools-extra/clang-tidy/utils/UsingInserter.cpp
@@ -14,9 +14,7 @@
 #include "clang/Lex/Lexer.h"
 #include <optional>
 
-namespace clang {
-namespace tidy {
-namespace utils {
+namespace clang::tidy::utils {
 
 using namespace ast_matchers;
 
@@ -84,6 +82,4 @@
   return QualifiedName;
 }
 
-} // namespace utils
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::utils
diff --git a/clang-tools-extra/clang-tidy/zircon/TemporaryObjectsCheck.cpp b/clang-tools-extra/clang-tidy/zircon/TemporaryObjectsCheck.cpp
--- a/clang-tools-extra/clang-tidy/zircon/TemporaryObjectsCheck.cpp
+++ b/clang-tools-extra/clang-tidy/zircon/TemporaryObjectsCheck.cpp
@@ -16,9 +16,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace zircon {
+namespace clang::tidy::zircon {
 
 AST_MATCHER_P(CXXRecordDecl, matchesAnyName, ArrayRef<StringRef>, Names) {
   std::string QualifiedName = Node.getQualifiedNameAsString();
@@ -54,6 +52,4 @@
   Options.store(Opts, "Names", utils::options::serializeStringList(Names));
 }
 
-} // namespace zircon
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::zircon
diff --git a/clang-tools-extra/clang-tidy/zircon/ZirconTidyModule.cpp b/clang-tools-extra/clang-tidy/zircon/ZirconTidyModule.cpp
--- a/clang-tools-extra/clang-tidy/zircon/ZirconTidyModule.cpp
+++ b/clang-tools-extra/clang-tidy/zircon/ZirconTidyModule.cpp
@@ -13,8 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
+namespace clang::tidy {
 namespace zircon {
 
 /// This module is for Zircon-specific checks.
@@ -35,5 +34,4 @@
 // and thus register the ZirconModule.
 volatile int ZirconModuleAnchorSource = 0;
 
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy