diff --git 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 @@ void AvoidCStyleCastsCheck::check(const MatchFinder::MatchResult &Result) {
   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
@@ -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 @@ void AvoidNSObjectNewCheck::check(const MatchFinder::MatchResult &Result) {
   }
 }
 
-} // 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
@@ -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 @@ void AvoidThrowingObjCExceptionCheck::check(
        "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
@@ -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 @@ void AvoidUnderscoreInGoogletestNameCheck::registerPPCallbacks(
       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
@@ -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 @@ void DefaultArgumentsCheck::check(const MatchFinder::MatchResult &Result) {
        "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
@@ -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 @@ void ExplicitConstructorCheck::check(const MatchFinder::MatchResult &Result) {
       << 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
@@ -20,9 +20,7 @@ AST_MATCHER(DeclRefExpr, hasExplicitTemplateArgs) {
 }
 } // namespace
 
-namespace tidy {
-namespace google {
-namespace build {
+namespace tidy::google::build {
 
 void ExplicitMakePairCheck::registerMatchers(
     ast_matchers::MatchFinder *Finder) {
@@ -66,7 +64,5 @@ void ExplicitMakePairCheck::check(const MatchFinder::MatchResult &Result) {
   }
 }
 
-} // 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
@@ -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 @@ void FunctionNamingCheck::check(const MatchFinder::MatchResult &Result) {
       << 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
@@ -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 @@ void GlobalNamesInHeadersCheck::check(const MatchFinder::MatchResult &Result) {
        "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
@@ -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 @@ void GlobalVariableDeclarationCheck::check(
   }
 }
 
-}  // 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
@@ -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 @@ static ClangTidyModuleRegistry::Add<GoogleModule> X("google-module",
 // 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
@@ -36,9 +36,7 @@ static Token getTokenAtLoc(SourceLocation Loc,
   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 @@ void IntegerTypesCheck::check(const MatchFinder::MatchResult &Result) {
                                                << 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
@@ -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 @@ void OverloadedUnaryAndCheck::check(const MatchFinder::MatchResult &Result) {
        "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
@@ -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 @@ void TodoCommentCheck::registerPPCallbacks(const SourceManager &SM,
   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
@@ -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 @@ void UnnamedNamespaceInHeaderCheck::check(
     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
@@ -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 @@ void UpgradeGoogletestCaseCheck::check(const MatchFinder::MatchResult &Result) {
   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
@@ -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 @@ bool UsingNamespaceDirectiveCheck::isStdLiteralsNamespace(
   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
@@ -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 @@ void ExceptionBaseclassCheck::check(const MatchFinder::MatchResult &Result) {
     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
@@ -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 @@ static ClangTidyModuleRegistry::Add<HICPPModule>
 // 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
@@ -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 @@ void MultiwayPathsCoveredCheck::handleSwitchWithoutDefault(
          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
@@ -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 @@ void NoAssemblerCheck::check(const MatchFinder::MatchResult &Result) {
   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
@@ -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 @@ void SignedBitwiseCheck::check(const MatchFinder::MatchResult &Result) {
       << 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
@@ -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 @@ static ClangTidyModuleRegistry::Add<LinuxKernelModule>
 // 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
@@ -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 @@ void MustCheckErrsCheck::check(const MatchFinder::MatchResult &Result) {
   }
 }
 
-} // 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
@@ -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 @@ std::string LLVMHeaderGuardCheck::getHeaderGuard(StringRef Filename,
   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
@@ -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 @@ void IncludeOrderPPCallbacks::EndOfMainFile() {
   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
@@ -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 @@ static ClangTidyModuleRegistry::Add<LLVMModule> X("llvm-module",
 // 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
@@ -19,8 +19,7 @@ namespace ast_matchers {
 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 @@ void PreferIsaOrDynCastInConditionalsCheck::check(
   }
 }
 
-} // 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
@@ -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 @@ void PreferRegisterOverUnsignedCheck::check(
              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
@@ -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 @@ void TwineLocalCheck::check(const MatchFinder::MatchResult &Result) {
   }
 }
 
-} // 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
@@ -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 @@ void CalleeNamespaceCheck::check(const MatchFinder::MatchResult &Result) {
        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
@@ -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 @@ void ImplementationInNamespaceCheck::check(
       << 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
@@ -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 @@ static ClangTidyModuleRegistry::Add<LLVMLibcModule>
 // 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
@@ -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 @@ void RestrictSystemLibcHeadersCheck::registerPPCallbacks(
       *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
@@ -21,9 +21,7 @@ namespace {
 #include "Confusables.inc"
 } // namespace
 
-namespace clang {
-namespace tidy {
-namespace misc {
+namespace clang::tidy::misc {
 
 ConfusableIdentifierCheck::ConfusableIdentifierCheck(StringRef Name,
                                                      ClangTidyContext *Context)
@@ -169,6 +167,4 @@ void ConfusableIdentifierCheck::registerMatchers(
   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
@@ -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 @@ void ConstCorrectnessCheck::registerScope(const CompoundStmt *LocalScope,
     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
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace misc {
+namespace clang::tidy::misc {
 
 namespace {
 
@@ -160,6 +158,4 @@ void DefinitionsInHeadersCheck::check(const MatchFinder::MatchResult &Result) {
   }
 }
 
-} // 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
@@ -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 @@ static ClangTidyModuleRegistry::Add<misc::MiscModule>
 // 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
@@ -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 @@ void MisleadingIdentifierCheck::registerMatchers(
   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
@@ -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 @@ void MisplacedConstCheck::check(const MatchFinder::MatchResult &Result) {
   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
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace misc {
+namespace clang::tidy::misc {
 
 namespace {
 
@@ -204,6 +202,4 @@ void NewDeleteOverloadsCheck::onEndOfTranslationUnit() {
         << 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
@@ -15,9 +15,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace misc {
+namespace clang::tidy::misc {
 
 namespace {
 
@@ -270,6 +268,4 @@ void NoRecursionCheck::check(const MatchFinder::MatchResult &Result) {
   }
 }
 
-} // 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
@@ -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 @@ void NonCopyableObjectsCheck::check(const MatchFinder::MatchResult &Result) {
         << 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
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace misc {
+namespace clang::tidy::misc {
 
 namespace {
 
@@ -92,6 +90,4 @@ void NonPrivateMemberVariablesInClassesCheck::check(
       << 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
@@ -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 @@ void RedundantExpressionCheck::check(const MatchFinder::MatchResult &Result) {
   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
@@ -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 @@ SourceLocation StaticAssertCheck::getLastParenLoc(const ASTContext *ASTCtx,
   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
@@ -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 @@ void ThrowByValueCatchByReferenceCheck::diagnoseCatchLocations(
   }
 }
 
-} // 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
@@ -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 @@ void UnconventionalAssignOperatorCheck::check(
   }
 }
 
-} // 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
@@ -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 @@ void UniqueptrResetReleaseCheck::check(const MatchFinder::MatchResult &Result) {
         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
@@ -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 @@ void UnusedAliasDeclsCheck::onEndOfTranslationUnit() {
   }
 }
 
-} // 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
@@ -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 @@ void UnusedParametersCheck::check(const MatchFinder::MatchResult &Result) {
   }
 }
 
-} // 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
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace misc {
+namespace clang::tidy::misc {
 
 namespace {
 
@@ -201,6 +199,4 @@ void UnusedUsingDeclsCheck::onEndOfTranslationUnit() {
   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
@@ -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 @@ void UseAnonymousNamespaceCheck::check(const MatchFinder::MatchResult &Result) {
   }
 }
 
-} // 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
@@ -29,9 +29,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 namespace {
 
@@ -717,6 +715,4 @@ void AvoidBindCheck::check(const MatchFinder::MatchResult &Result) {
                                        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
@@ -38,9 +38,7 @@ AST_MATCHER(clang::ParmVarDecl, isArgvOfMain) {
 
 } // namespace
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 void AvoidCArraysCheck::registerMatchers(MatchFinder *Finder) {
   Finder->addMatcher(
@@ -63,6 +61,4 @@ void AvoidCArraysCheck::check(const MatchFinder::MatchResult &Result) {
       << 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
@@ -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 @@ void ConcatNestedNamespacesCheck::check(
   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
@@ -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 @@ void IncludeModernizePPCallbacks::InclusionDirective(
   }
 }
 
-} // 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
@@ -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 @@ void DeprecatedIosBaseAliasesCheck::check(
     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
@@ -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 @@ LiteralSize IntegralLiteralExpressionMatcher::largestLiteralSize() const {
   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
@@ -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 @@ llvm::StringRef LoopConvertCheck::getReverseHeader() const {
 }
 
 } // 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
@@ -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 @@ bool VariableNamer::declarationExists(StringRef Symbol) {
   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
@@ -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 @@ void MacroToEnumCheck::check(
     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
@@ -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 @@ MakeSharedCheck::getSmartPointerTypeMatcher() const {
                                      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
@@ -14,9 +14,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 namespace {
 
@@ -439,6 +437,4 @@ void MakeSmartPtrCheck::insertHeader(DiagnosticBuilder &Diag, FileID FD) {
   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
@@ -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 @@ bool MakeUniqueCheck::isLanguageVersionSupported(
 
 // 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
@@ -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 @@ static ClangTidyModuleRegistry::Add<ModernizeModule> X("modernize-module",
 // 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
@@ -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 @@ void PassByValueCheck::check(const MatchFinder::MatchResult &Result) {
               "<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
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 namespace {
 
@@ -147,6 +145,4 @@ void RawStringLiteralCheck::replaceWithRawStringLiteral(
       << 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
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 namespace {
 
@@ -287,6 +285,4 @@ void RedundantVoidArgCheck::processLambdaExpr(
   }
 }
 
-} // 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
@@ -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 @@ void ReplaceAutoPtrCheck::check(const MatchFinder::MatchResult &Result) {
                                       "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
@@ -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 @@ void ReplaceDisallowCopyAndAssignMacroCheck::storeOptions(
   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
@@ -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 @@ void ReplaceRandomShuffleCheck::check(const MatchFinder::MatchResult &Result) {
       "<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
@@ -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 @@ void ReturnBracedInitListCheck::check(const MatchFinder::MatchResult &Result) {
        << 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
@@ -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 @@ void ShrinkToFitCheck::check(const MatchFinder::MatchResult &Result) {
       << 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
@@ -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 @@ void UnaryStaticAssertCheck::check(const MatchFinder::MatchResult &Result) {
       << 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
@@ -17,9 +17,7 @@ using namespace clang;
 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 @@ void UseAutoCheck::check(const MatchFinder::MatchResult &Result) {
   }
 }
 
-} // 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
@@ -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 @@ void UseBoolLiteralsCheck::check(const MatchFinder::MatchResult &Result) {
         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
@@ -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 @@ void UseDefaultMemberInitCheck::checkExistingInit(
       << 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
@@ -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 @@ void UseEmplaceCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {
                 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
@@ -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 @@ void UseEqualsDefaultCheck::check(const MatchFinder::MatchResult &Result) {
   }
 }
 
-} // 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
@@ -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 @@ void UseEqualsDeleteCheck::check(const MatchFinder::MatchResult &Result) {
   }
 }
 
-} // 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
@@ -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 @@ bool UseNodiscardCheck::isLanguageVersionSupported(
   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
@@ -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 @@ void UseNoexceptCheck::check(const MatchFinder::MatchResult &Result) {
       << 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
@@ -16,9 +16,7 @@ using namespace clang;
 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 @@ void UseNullptrCheck::check(const MatchFinder::MatchResult &Result) {
       .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
@@ -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 @@ void UseOverrideCheck::check(const MatchFinder::MatchResult &Result) {
   }
 }
 
-} // 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
@@ -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 @@ void UseTrailingReturnTypeCheck::check(const MatchFinder::MatchResult &Result) {
       << 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
@@ -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 @@ void UseTransparentFunctorsCheck::check(
                                   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
@@ -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 @@ void UseUncaughtExceptionsCheck::check(const MatchFinder::MatchResult &Result) {
   }
 }
 
-} // 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
@@ -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 @@ void UseUsingCheck::check(const MatchFinder::MatchResult &Result) {
   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
@@ -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::checkBuffers(ArrayRef<const Type *> BufferTypes,
 }
 
 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
@@ -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 @@ static ClangTidyModuleRegistry::Add<mpi::MPIModule>
 // 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
@@ -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::checkArguments(ArrayRef<const Type *> BufferTypes,
 }
 
 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
@@ -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 @@ void AssertEquals::check(const ast_matchers::MatchFinder::MatchResult &result) {
   }
 }
 
-} // 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
@@ -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 @@ void AvoidNSErrorInitCheck::check(const MatchFinder::MatchResult &Result) {
        "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
@@ -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 @@ void DeallocInCategoryCheck::check(const MatchFinder::MatchResult &Result) {
       << 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
@@ -15,9 +15,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace objc {
+namespace clang::tidy::objc {
 
 namespace {
 
@@ -80,6 +78,4 @@ void ForbiddenSubclassingCheck::storeOptions(
       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
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace objc {
+namespace clang::tidy::objc {
 
 namespace {
 
@@ -53,6 +51,4 @@ void MissingHashCheck::check(const MatchFinder::MatchResult &Result) {
       << 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
@@ -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 @@ void NSDateFormatterCheck::check(const MatchFinder::MatchResult &Result) {
   }
 }
 
-} // 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
@@ -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 @@ void NSInvocationArgumentLifetimeCheck::check(
     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
@@ -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 @@ static ClangTidyModuleRegistry::Add<ObjCModule> X(
 // 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
@@ -18,9 +18,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace objc {
+namespace clang::tidy::objc {
 
 namespace {
 
@@ -133,6 +131,4 @@ void PropertyDeclarationCheck::check(const MatchFinder::MatchResult &Result) {
       << 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
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace objc {
+namespace clang::tidy::objc {
 
 namespace {
 
@@ -104,6 +102,4 @@ void SuperSelfCheck::check(const MatchFinder::MatchResult &Result) {
                                        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
@@ -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 @@ void ExceptionEscapeCheck::check(const MatchFinder::MatchResult &Result) {
       << 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
@@ -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 @@ static ClangTidyModuleRegistry::Add<OpenMPModule>
 // 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
@@ -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 @@ void UseDefaultNoneCheck::check(const MatchFinder::MatchResult &Result) {
       << 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
@@ -15,9 +15,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace performance {
+namespace clang::tidy::performance {
 
 namespace {
 
@@ -95,6 +93,4 @@ void FasterStringFindCheck::check(const MatchFinder::MatchResult &Result) {
              *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
@@ -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 @@ bool ForRangeCopyCheck::handleCopyIsOnlyConstReferenced(
   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
@@ -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 @@ void ImplicitConversionInLoopCheck::reportAndFix(const ASTContext *Context,
   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
@@ -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 @@ void InefficientAlgorithmCheck::check(const MatchFinder::MatchResult &Result) {
       << 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
@@ -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 @@ void InefficientStringConcatenationCheck::check(
     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
@@ -15,9 +15,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace performance {
+namespace clang::tidy::performance {
 
 namespace {
 
@@ -273,6 +271,4 @@ void InefficientVectorOperationCheck::check(
   }
 }
 
-} // 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
@@ -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 @@ void MoveConstArgCheck::check(const MatchFinder::MatchResult &Result) {
   }
 }
 
-} // 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
@@ -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 @@ void MoveConstructorInitCheck::check(const MatchFinder::MatchResult &Result) {
   }
 }
 
-} // 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
@@ -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 @@ void NoAutomaticMoveCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {
                 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
@@ -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 @@ void NoIntToPtrCheck::check(const MatchFinder::MatchResult &Result) {
        "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
@@ -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 @@ void NoexceptMoveConstructorCheck::check(
   }
 }
 
-} // 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
@@ -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 @@ static ClangTidyModuleRegistry::Add<PerformanceModule>
 // 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
@@ -16,9 +16,7 @@ using namespace clang::ast_matchers;
 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 @@ void TriviallyDestructibleCheck::check(const MatchFinder::MatchResult &Result) {
        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
@@ -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 @@ void TypePromotionInMathFnCheck::check(const MatchFinder::MatchResult &Result) {
         "<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
@@ -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 @@ void UnnecessaryCopyInitialization::storeOptions(
                 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
@@ -20,9 +20,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace performance {
+namespace clang::tidy::performance {
 
 namespace {
 
@@ -193,6 +191,4 @@ void UnnecessaryValueParamCheck::handleMoveFix(const ParmVarDecl &Var,
               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
@@ -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 @@ class ClangTidyPluginAction : public PluginASTAction {
 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
@@ -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 @@ static ClangTidyModuleRegistry::Add<PortabilityModule>
 // 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
@@ -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 @@ void RestrictSystemIncludesCheck::storeOptions(
   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
@@ -17,9 +17,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace portability {
+namespace clang::tidy::portability {
 
 namespace {
 
@@ -146,6 +144,4 @@ void SIMDIntrinsicsCheck::check(const MatchFinder::MatchResult &Result) {
   }
 }
 
-} // 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
@@ -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 @@ void StdAllocatorConstCheck::check(const MatchFinder::MatchResult &Result) {
        "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
@@ -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 @@ void AvoidConstParamsInDecls::check(const MatchFinder::MatchResult &Result) {
       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
@@ -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 @@ void BracesAroundStatementsCheck::onEndOfTranslationUnit() {
   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
@@ -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 @@ void ConstReturnTypeCheck::check(const MatchFinder::MatchResult &Result) {
     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
@@ -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 @@ void ContainerContainsCheck::check(const MatchFinder::MatchResult &Result) {
       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
@@ -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 @@ void ContainerDataPointerCheck::check(const MatchFinder::MatchResult &Result) {
        "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
@@ -90,8 +90,7 @@ AST_MATCHER(QualType, isIntegralType) {
   return Node->isIntegralType(Finder->getASTContext());
 }
 } // namespace ast_matchers
-namespace tidy {
-namespace readability {
+namespace tidy::readability {
 
 using utils::isBinaryOrTernary;
 
@@ -328,6 +327,5 @@ void ContainerSizeEmptyCheck::check(const MatchFinder::MatchResult &Result) {
       << 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
@@ -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 @@ void ConvertMemberFunctionsToStatic::check(
   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
@@ -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 @@ void DeleteNullPointerCheck::check(const MatchFinder::MatchResult &Result) {
   }
 }
 
-} // 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
@@ -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 @@ void DuplicateIncludeCheck::registerPPCallbacks(
   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
@@ -16,9 +16,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 namespace {
 
@@ -324,6 +322,4 @@ void ElseAfterReturnCheck::check(const MatchFinder::MatchResult &Result) {
   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
@@ -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 @@ void FunctionCognitiveComplexityCheck::check(
   }
 }
 
-} // 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
@@ -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 @@ void FunctionSizeCheck::check(const MatchFinder::MatchResult &Result) {
   }
 }
 
-} // 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
@@ -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 @@ void IdentifierLengthCheck::check(const MatchFinder::MatchResult &Result) {
   }
 }
 
-} // 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
@@ -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 @@ IdentifierNamingCheck::getStyleForFile(StringRef FileName) const {
 }
 
 } // 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
@@ -15,9 +15,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 namespace {
 
@@ -391,6 +389,4 @@ void ImplicitBoolConversionCheck::handleCastFromBool(
   }
 }
 
-} // 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
@@ -15,9 +15,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 namespace {
 
@@ -350,6 +348,4 @@ void InconsistentDeclarationParameterNameCheck::markRedeclarationsAsVisited(
   }
 }
 
-} // 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
@@ -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 @@ void IsolateDeclarationCheck::check(const MatchFinder::MatchResult &Result) {
   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
@@ -54,8 +54,7 @@ static bool isUsedToDefineABitField(const MatchFinder::MatchResult &Result,
                       });
 }
 
-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 @@ bool MagicNumbersCheck::isBitFieldWidth(
                       });
 }
 
-} // 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
@@ -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 @@ void MakeMemberFunctionConstCheck::check(
   }
 }
 
-} // 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
@@ -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 @@ void MisleadingIndentationCheck::check(const MatchFinder::MatchResult &Result) {
     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
@@ -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 @@ void MisplacedArrayIndexCheck::check(const MatchFinder::MatchResult &Result) {
       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
@@ -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 @@ void NamedParameterCheck::check(const MatchFinder::MatchResult &Result) {
   }
 }
 
-} // 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
@@ -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 @@ void NamespaceCommentCheck::check(const MatchFinder::MatchResult &Result) {
       << 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
@@ -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 @@ void NonConstParameterCheck::markCanNotBeConst(const Expr *E,
   }
 }
 
-} // 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
@@ -14,9 +14,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 namespace {
 
@@ -286,6 +284,4 @@ void QualifiedAutoCheck::check(const MatchFinder::MatchResult &Result) {
   }
 }
 
-} // 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
@@ -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 @@ static ClangTidyModuleRegistry::Add<ReadabilityModule>
 // 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
@@ -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 @@ void RedundantAccessSpecifiersCheck::check(
   }
 }
 
-} // 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
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 namespace {
 
@@ -91,6 +89,4 @@ void RedundantControlFlowCheck::issueDiagnostic(
   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
@@ -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 @@ void RedundantDeclarationCheck::check(const MatchFinder::MatchResult &Result) {
   }
   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
@@ -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 @@ void RedundantFunctionPtrDereferenceCheck::check(const MatchFinder::MatchResult
       << 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
@@ -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 @@ void RedundantMemberInitCheck::check(const MatchFinder::MatchResult &Result) {
   }
 }
 
-} // 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
@@ -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 @@ void RedundantPreprocessorCheck::registerPPCallbacks(
       ::std::make_unique<RedundantPreprocessorCallbacks>(*this, *PP));
 }
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability