diff --git a/clang-tools-extra/clang-tidy/ClangTidyForceLinker.h b/clang-tools-extra/clang-tidy/ClangTidyForceLinker.h
--- a/clang-tools-extra/clang-tidy/ClangTidyForceLinker.h
+++ b/clang-tools-extra/clang-tidy/ClangTidyForceLinker.h
@@ -12,8 +12,7 @@
 #include "clang-tidy-config.h"
 #include "llvm/Support/Compiler.h"
 
-namespace clang {
-namespace tidy {
+namespace clang::tidy {
 
 // This anchor is used to force the linker to link the AbseilModule.
 extern volatile int AbseilModuleAnchorSource;
@@ -138,7 +137,6 @@
 static int LLVM_ATTRIBUTE_UNUSED ZirconModuleAnchorDestination =
     ZirconModuleAnchorSource;
 
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy
 
 #endif
diff --git a/clang-tools-extra/clang-tidy/ClangTidyModule.h b/clang-tools-extra/clang-tidy/ClangTidyModule.h
--- a/clang-tools-extra/clang-tidy/ClangTidyModule.h
+++ b/clang-tools-extra/clang-tidy/ClangTidyModule.h
@@ -15,8 +15,7 @@
 #include <functional>
 #include <memory>
 
-namespace clang {
-namespace tidy {
+namespace clang::tidy {
 
 class ClangTidyCheck;
 class ClangTidyContext;
@@ -94,7 +93,6 @@
   virtual ClangTidyOptions getModuleOptions();
 };
 
-} // end namespace tidy
-} // end namespace clang
+} // namespace clang::tidy
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_CLANGTIDYMODULE_H
diff --git a/clang-tools-extra/clang-tidy/ClangTidyModuleRegistry.h b/clang-tools-extra/clang-tidy/ClangTidyModuleRegistry.h
--- a/clang-tools-extra/clang-tidy/ClangTidyModuleRegistry.h
+++ b/clang-tools-extra/clang-tidy/ClangTidyModuleRegistry.h
@@ -12,12 +12,10 @@
 #include "ClangTidyModule.h"
 #include "llvm/Support/Registry.h"
 
-namespace clang {
-namespace tidy {
+namespace clang::tidy {
 
 typedef llvm::Registry<ClangTidyModule> ClangTidyModuleRegistry;
 
-} // end namespace tidy
-} // end namespace clang
+} // namespace clang::tidy
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_CLANGTIDYMODULEREGISTRY_H
diff --git a/clang-tools-extra/clang-tidy/ClangTidyOptions.h b/clang-tools-extra/clang-tidy/ClangTidyOptions.h
--- a/clang-tools-extra/clang-tidy/ClangTidyOptions.h
+++ b/clang-tools-extra/clang-tidy/ClangTidyOptions.h
@@ -22,8 +22,7 @@
 #include <utility>
 #include <vector>
 
-namespace clang {
-namespace tidy {
+namespace clang::tidy {
 
 /// Contains a list of line ranges in a single file.
 struct FileFilter {
@@ -328,7 +327,6 @@
 /// Serializes configuration to a YAML-encoded string.
 std::string configurationAsText(const ClangTidyOptions &Options);
 
-} // end namespace tidy
-} // end namespace clang
+} // namespace clang::tidy
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_CLANGTIDYOPTIONS_H
diff --git a/clang-tools-extra/clang-tidy/ClangTidyProfiling.h b/clang-tools-extra/clang-tidy/ClangTidyProfiling.h
--- a/clang-tools-extra/clang-tidy/ClangTidyProfiling.h
+++ b/clang-tools-extra/clang-tidy/ClangTidyProfiling.h
@@ -19,8 +19,7 @@
 class raw_ostream;
 } // namespace llvm
 
-namespace clang {
-namespace tidy {
+namespace clang::tidy {
 
 class ClangTidyProfiling {
 public:
@@ -54,7 +53,6 @@
   ~ClangTidyProfiling();
 };
 
-} // end namespace tidy
-} // end namespace clang
+} // namespace clang::tidy
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_CLANGTIDYPROFILING_H
diff --git a/clang-tools-extra/clang-tidy/ExpandModularHeadersPPCallbacks.h b/clang-tools-extra/clang-tidy/ExpandModularHeadersPPCallbacks.h
--- a/clang-tools-extra/clang-tidy/ExpandModularHeadersPPCallbacks.h
+++ b/clang-tools-extra/clang-tidy/ExpandModularHeadersPPCallbacks.h
@@ -13,12 +13,10 @@
 #include "clang/Lex/Preprocessor.h"
 #include "llvm/ADT/DenseSet.h"
 
-namespace llvm {
-namespace vfs {
+namespace llvm::vfs {
 class OverlayFileSystem;
 class InMemoryFileSystem;
-} // namespace vfs
-} // namespace llvm
+} // namespace llvm::vfs
 
 namespace clang {
 class CompilerInstance;
diff --git a/clang-tools-extra/clang-tidy/GlobList.h b/clang-tools-extra/clang-tidy/GlobList.h
--- a/clang-tools-extra/clang-tidy/GlobList.h
+++ b/clang-tools-extra/clang-tidy/GlobList.h
@@ -15,8 +15,7 @@
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Support/Regex.h"
 
-namespace clang {
-namespace tidy {
+namespace clang::tidy {
 
 /// Read-only set of strings represented as a list of positive and negative
 /// globs.
@@ -62,7 +61,6 @@
   mutable llvm::StringMap<bool> Cache;
 };
 
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_GLOBLIST_H
diff --git a/clang-tools-extra/clang-tidy/NoLintDirectiveHandler.h b/clang-tools-extra/clang-tidy/NoLintDirectiveHandler.h
--- a/clang-tools-extra/clang-tidy/NoLintDirectiveHandler.h
+++ b/clang-tools-extra/clang-tidy/NoLintDirectiveHandler.h
@@ -13,18 +13,15 @@
 #include "llvm/ADT/StringRef.h"
 #include <memory>
 
-namespace clang {
-namespace tooling {
+namespace clang::tooling {
 struct Diagnostic;
-} // namespace tooling
-} // namespace clang
+} // namespace clang::tooling
 
 namespace llvm {
 template <typename T> class SmallVectorImpl;
 } // namespace llvm
 
-namespace clang {
-namespace tidy {
+namespace clang::tidy {
 
 /// This class is used to locate NOLINT comments in the file being analyzed, to
 /// decide whether a diagnostic should be suppressed.
@@ -45,7 +42,6 @@
   std::unique_ptr<Impl> PImpl;
 };
 
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_NOLINTDIRECTIVEHANDLER_H
diff --git a/clang-tools-extra/clang-tidy/abseil/AbseilMatcher.h b/clang-tools-extra/clang-tidy/abseil/AbseilMatcher.h
--- a/clang-tools-extra/clang-tidy/abseil/AbseilMatcher.h
+++ b/clang-tools-extra/clang-tidy/abseil/AbseilMatcher.h
@@ -10,8 +10,7 @@
 #include "clang/ASTMatchers/ASTMatchFinder.h"
 #include <algorithm>
 
-namespace clang {
-namespace ast_matchers {
+namespace clang::ast_matchers {
 
 /// Matches AST nodes that were found within Abseil files.
 ///
@@ -57,5 +56,4 @@
   });
 }
 
-} // namespace ast_matchers
-} // namespace clang
+} // namespace clang::ast_matchers
diff --git a/clang-tools-extra/clang-tidy/abseil/CleanupCtadCheck.h b/clang-tools-extra/clang-tidy/abseil/CleanupCtadCheck.h
--- a/clang-tools-extra/clang-tidy/abseil/CleanupCtadCheck.h
+++ b/clang-tools-extra/clang-tidy/abseil/CleanupCtadCheck.h
@@ -11,9 +11,7 @@
 
 #include "../utils/TransformerClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace abseil {
+namespace clang::tidy::abseil {
 
 /// Suggests switching the initialization pattern of `absl::Cleanup`
 /// instances from the factory function to class template argument
@@ -30,8 +28,6 @@
   }
 };
 
-} // namespace abseil
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::abseil
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_ABSEIL_CLEANUPCTADCHECK_H
diff --git a/clang-tools-extra/clang-tidy/abseil/DurationAdditionCheck.h b/clang-tools-extra/clang-tidy/abseil/DurationAdditionCheck.h
--- a/clang-tools-extra/clang-tidy/abseil/DurationAdditionCheck.h
+++ b/clang-tools-extra/clang-tidy/abseil/DurationAdditionCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace abseil {
+namespace clang::tidy::abseil {
 
 /// Checks for cases where addition should be performed in the
 /// ``absl::Time`` domain.
@@ -28,8 +26,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace abseil
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::abseil
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_ABSEIL_TIMEADDITIONCHECK_H
diff --git a/clang-tools-extra/clang-tidy/abseil/DurationComparisonCheck.h b/clang-tools-extra/clang-tidy/abseil/DurationComparisonCheck.h
--- a/clang-tools-extra/clang-tidy/abseil/DurationComparisonCheck.h
+++ b/clang-tools-extra/clang-tidy/abseil/DurationComparisonCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace abseil {
+namespace clang::tidy::abseil {
 
 /// Prefer comparison in the absl::Duration domain instead of the numeric
 /// domain.
@@ -28,8 +26,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace abseil
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::abseil
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_ABSEIL_DURATIONCOMPARISONCHECK_H
diff --git a/clang-tools-extra/clang-tidy/abseil/DurationConversionCastCheck.h b/clang-tools-extra/clang-tidy/abseil/DurationConversionCastCheck.h
--- a/clang-tools-extra/clang-tidy/abseil/DurationConversionCastCheck.h
+++ b/clang-tools-extra/clang-tidy/abseil/DurationConversionCastCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace abseil {
+namespace clang::tidy::abseil {
 
 /// Checks for casts of ``absl::Duration`` conversion functions, and recommends
 /// the right conversion function instead.
@@ -28,8 +26,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace abseil
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::abseil
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_ABSEIL_DURATIONCONVERSIONCASTCHECK_H
diff --git a/clang-tools-extra/clang-tidy/abseil/DurationDivisionCheck.h b/clang-tools-extra/clang-tidy/abseil/DurationDivisionCheck.h
--- a/clang-tools-extra/clang-tidy/abseil/DurationDivisionCheck.h
+++ b/clang-tools-extra/clang-tidy/abseil/DurationDivisionCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace abseil {
+namespace clang::tidy::abseil {
 
 // Find potential incorrect uses of integer division of absl::Duration objects.
 //
@@ -30,8 +28,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace abseil
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::abseil
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_ABSEIL_DURATIONDIVISIONCHECK_H_
diff --git a/clang-tools-extra/clang-tidy/abseil/DurationFactoryFloatCheck.h b/clang-tools-extra/clang-tidy/abseil/DurationFactoryFloatCheck.h
--- a/clang-tools-extra/clang-tidy/abseil/DurationFactoryFloatCheck.h
+++ b/clang-tools-extra/clang-tidy/abseil/DurationFactoryFloatCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace abseil {
+namespace clang::tidy::abseil {
 
 /// This check finds cases where `Duration` factories are being called with
 /// floating point arguments, but could be called using integer arguments.
@@ -30,8 +28,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace abseil
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::abseil
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_ABSEIL_DURATIONFACTORYFLOATCHECK_H
diff --git a/clang-tools-extra/clang-tidy/abseil/DurationFactoryScaleCheck.h b/clang-tools-extra/clang-tidy/abseil/DurationFactoryScaleCheck.h
--- a/clang-tools-extra/clang-tidy/abseil/DurationFactoryScaleCheck.h
+++ b/clang-tools-extra/clang-tidy/abseil/DurationFactoryScaleCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace abseil {
+namespace clang::tidy::abseil {
 
 /// This check finds cases where the incorrect `Duration` factory function is
 /// being used by looking for scaling constants inside the factory argument
@@ -30,8 +28,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace abseil
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::abseil
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_ABSEIL_DURATIONFACTORYSCALECHECK_H
diff --git a/clang-tools-extra/clang-tidy/abseil/DurationRewriter.h b/clang-tools-extra/clang-tidy/abseil/DurationRewriter.h
--- a/clang-tools-extra/clang-tidy/abseil/DurationRewriter.h
+++ b/clang-tools-extra/clang-tidy/abseil/DurationRewriter.h
@@ -14,9 +14,7 @@
 #include <cinttypes>
 #include <optional>
 
-namespace clang {
-namespace tidy {
-namespace abseil {
+namespace clang::tidy::abseil {
 
 /// Duration factory and conversion scales
 enum class DurationScale : std::uint8_t {
@@ -135,8 +133,6 @@
       hasEitherOperand(ignoringImpCasts(callExpr(callee(funcDecl)))));
 }
 
-} // namespace abseil
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::abseil
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_ABSEIL_DURATIONREWRITER_H
diff --git a/clang-tools-extra/clang-tidy/abseil/DurationSubtractionCheck.h b/clang-tools-extra/clang-tidy/abseil/DurationSubtractionCheck.h
--- a/clang-tools-extra/clang-tidy/abseil/DurationSubtractionCheck.h
+++ b/clang-tools-extra/clang-tidy/abseil/DurationSubtractionCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace abseil {
+namespace clang::tidy::abseil {
 
 /// Checks for cases where subtraction should be performed in the
 /// `absl::Duration` domain.
@@ -28,8 +26,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace abseil
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::abseil
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_ABSEIL_DURATIONSUBTRACTIONCHECK_H
diff --git a/clang-tools-extra/clang-tidy/abseil/DurationUnnecessaryConversionCheck.h b/clang-tools-extra/clang-tidy/abseil/DurationUnnecessaryConversionCheck.h
--- a/clang-tools-extra/clang-tidy/abseil/DurationUnnecessaryConversionCheck.h
+++ b/clang-tools-extra/clang-tidy/abseil/DurationUnnecessaryConversionCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace abseil {
+namespace clang::tidy::abseil {
 
 /// Finds and fixes cases where ``absl::Duration`` values are being converted
 /// to numeric types and back again.
@@ -28,8 +26,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace abseil
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::abseil
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_ABSEIL_TIMEDOUBLECONVERSIONCHECK_H
diff --git a/clang-tools-extra/clang-tidy/abseil/FasterStrsplitDelimiterCheck.h b/clang-tools-extra/clang-tidy/abseil/FasterStrsplitDelimiterCheck.h
--- a/clang-tools-extra/clang-tidy/abseil/FasterStrsplitDelimiterCheck.h
+++ b/clang-tools-extra/clang-tidy/abseil/FasterStrsplitDelimiterCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace abseil {
+namespace clang::tidy::abseil {
 
 /// Finds instances of absl::StrSplit() or absl::MaxSplits() where the delimiter
 /// is a single character string literal and replaces it with a character.
@@ -31,8 +29,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace abseil
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::abseil
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_ABSEIL_FASTERSTRSPLITDELIMITERCHECK_H
diff --git a/clang-tools-extra/clang-tidy/abseil/NoInternalDependenciesCheck.h b/clang-tools-extra/clang-tidy/abseil/NoInternalDependenciesCheck.h
--- a/clang-tools-extra/clang-tidy/abseil/NoInternalDependenciesCheck.h
+++ b/clang-tools-extra/clang-tidy/abseil/NoInternalDependenciesCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace abseil {
+namespace clang::tidy::abseil {
 
 /// Finds instances where the user depends on internal details and warns them
 /// against doing so.
@@ -31,8 +29,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace abseil
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::abseil
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_ABSEIL_NOINTERNALDEPSCHECK_H
diff --git a/clang-tools-extra/clang-tidy/abseil/NoNamespaceCheck.h b/clang-tools-extra/clang-tidy/abseil/NoNamespaceCheck.h
--- a/clang-tools-extra/clang-tidy/abseil/NoNamespaceCheck.h
+++ b/clang-tools-extra/clang-tidy/abseil/NoNamespaceCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace abseil {
+namespace clang::tidy::abseil {
 
 /// This check ensures users don't open namespace absl, as that violates
 /// Abseil's compatibility guidelines.
@@ -31,8 +29,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace abseil
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::abseil
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_ABSEIL_NONAMESPACECHECK_H
diff --git a/clang-tools-extra/clang-tidy/abseil/RedundantStrcatCallsCheck.h b/clang-tools-extra/clang-tidy/abseil/RedundantStrcatCallsCheck.h
--- a/clang-tools-extra/clang-tidy/abseil/RedundantStrcatCallsCheck.h
+++ b/clang-tools-extra/clang-tidy/abseil/RedundantStrcatCallsCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace abseil {
+namespace clang::tidy::abseil {
 
 /// Flags redundant calls to absl::StrCat when the result is being passed to 
 ///	another call of absl::StrCat/absl::StrAppend. Also suggests a fix to 
@@ -34,8 +32,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace abseil
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::abseil
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_ABSEIL_REDUNDANTSTRCATCALLSCHECK_H
diff --git a/clang-tools-extra/clang-tidy/abseil/StrCatAppendCheck.h b/clang-tools-extra/clang-tidy/abseil/StrCatAppendCheck.h
--- a/clang-tools-extra/clang-tidy/abseil/StrCatAppendCheck.h
+++ b/clang-tools-extra/clang-tidy/abseil/StrCatAppendCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace abseil {
+namespace clang::tidy::abseil {
 
 /// Flags uses of absl::StrCat to append to a string. Suggests absl::StrAppend
 /// should be used instead. 
@@ -31,8 +29,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace abseil
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::abseil
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_ABSEIL_STRCATAPPENDCHECK_H
diff --git a/clang-tools-extra/clang-tidy/abseil/StringFindStartswithCheck.h b/clang-tools-extra/clang-tidy/abseil/StringFindStartswithCheck.h
--- a/clang-tools-extra/clang-tidy/abseil/StringFindStartswithCheck.h
+++ b/clang-tools-extra/clang-tidy/abseil/StringFindStartswithCheck.h
@@ -17,9 +17,7 @@
 #include <string>
 #include <vector>
 
-namespace clang {
-namespace tidy {
-namespace abseil {
+namespace clang::tidy::abseil {
 
 // Find string.find(...) == 0 comparisons and suggest replacing with StartsWith.
 // FIXME(niko): Add similar check for EndsWith
@@ -40,8 +38,6 @@
   const StringRef AbseilStringsMatchHeader;
 };
 
-} // namespace abseil
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::abseil
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_ABSEIL_STRINGFINDSTARTSWITHCHECK_H
diff --git a/clang-tools-extra/clang-tidy/abseil/StringFindStrContainsCheck.h b/clang-tools-extra/clang-tidy/abseil/StringFindStrContainsCheck.h
--- a/clang-tools-extra/clang-tidy/abseil/StringFindStrContainsCheck.h
+++ b/clang-tools-extra/clang-tidy/abseil/StringFindStrContainsCheck.h
@@ -12,9 +12,7 @@
 #include "../ClangTidyCheck.h"
 #include "../utils/TransformerClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace abseil {
+namespace clang::tidy::abseil {
 
 /// Finds s.find(...) == string::npos comparisons (for various string-like
 /// types) and suggests replacing with absl::StrContains.
@@ -32,8 +30,6 @@
   const StringRef AbseilStringsMatchHeaderOption;
 };
 
-} // namespace abseil
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::abseil
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_ABSEIL_STRINGFINDSTRCONTAINSCHECK_H
diff --git a/clang-tools-extra/clang-tidy/abseil/TimeComparisonCheck.h b/clang-tools-extra/clang-tidy/abseil/TimeComparisonCheck.h
--- a/clang-tools-extra/clang-tidy/abseil/TimeComparisonCheck.h
+++ b/clang-tools-extra/clang-tidy/abseil/TimeComparisonCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace abseil {
+namespace clang::tidy::abseil {
 
 /// Prefer comparison in the `absl::Time` domain instead of the numeric
 /// domain.
@@ -28,8 +26,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace abseil
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::abseil
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_ABSEIL_TIMECOMPARECHECK_H
diff --git a/clang-tools-extra/clang-tidy/abseil/TimeSubtractionCheck.h b/clang-tools-extra/clang-tidy/abseil/TimeSubtractionCheck.h
--- a/clang-tools-extra/clang-tidy/abseil/TimeSubtractionCheck.h
+++ b/clang-tools-extra/clang-tidy/abseil/TimeSubtractionCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace abseil {
+namespace clang::tidy::abseil {
 
 /// Finds and fixes `absl::Time` subtraction expressions to do subtraction
 /// in the time domain instead of the numeric domain.
@@ -31,8 +29,6 @@
   void emitDiagnostic(const Expr* Node, llvm::StringRef Replacement);
 };
 
-} // namespace abseil
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::abseil
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_ABSEIL_TIMESUBTRACTIONCHECK_H
diff --git a/clang-tools-extra/clang-tidy/abseil/UpgradeDurationConversionsCheck.h b/clang-tools-extra/clang-tidy/abseil/UpgradeDurationConversionsCheck.h
--- a/clang-tools-extra/clang-tidy/abseil/UpgradeDurationConversionsCheck.h
+++ b/clang-tools-extra/clang-tidy/abseil/UpgradeDurationConversionsCheck.h
@@ -14,9 +14,7 @@
 #include "clang/Basic/SourceLocation.h"
 #include "llvm/ADT/DenseSet.h"
 
-namespace clang {
-namespace tidy {
-namespace abseil {
+namespace clang::tidy::abseil {
 
 /// Finds deprecated uses of `absl::Duration` arithmetic operators and factories.
 ///
@@ -36,8 +34,6 @@
   llvm::DenseSet<SourceLocation> MatchedTemplateLocations;
 };
 
-} // namespace abseil
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::abseil
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_ABSEIL_UPGRADEDURATIONCONVERSIONSCHECK_H
diff --git a/clang-tools-extra/clang-tidy/altera/IdDependentBackwardBranchCheck.h b/clang-tools-extra/clang-tidy/altera/IdDependentBackwardBranchCheck.h
--- a/clang-tools-extra/clang-tidy/altera/IdDependentBackwardBranchCheck.h
+++ b/clang-tools-extra/clang-tidy/altera/IdDependentBackwardBranchCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace altera {
+namespace clang::tidy::altera {
 
 /// Finds ID-dependent variables and fields used within loops, and warns of
 /// their usage. Using these variables in loops can lead to performance
@@ -76,8 +74,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace altera
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::altera
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_ALTERA_IDDEPENDENTBACKWARDBRANCHCHECK_H
diff --git a/clang-tools-extra/clang-tidy/altera/KernelNameRestrictionCheck.h b/clang-tools-extra/clang-tidy/altera/KernelNameRestrictionCheck.h
--- a/clang-tools-extra/clang-tidy/altera/KernelNameRestrictionCheck.h
+++ b/clang-tools-extra/clang-tidy/altera/KernelNameRestrictionCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace altera {
+namespace clang::tidy::altera {
 
 /// Finds kernel files and include directives whose filename is `kernel.cl`,
 /// `Verilog.cl`, or `VHDL.cl`.
@@ -28,8 +26,6 @@
                            Preprocessor *) override;
 };
 
-} // namespace altera
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::altera
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_ALTERA_KERNEL_NAME_RESTRICTION_CHECK_H
diff --git a/clang-tools-extra/clang-tidy/altera/SingleWorkItemBarrierCheck.h b/clang-tools-extra/clang-tidy/altera/SingleWorkItemBarrierCheck.h
--- a/clang-tools-extra/clang-tidy/altera/SingleWorkItemBarrierCheck.h
+++ b/clang-tools-extra/clang-tidy/altera/SingleWorkItemBarrierCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace altera {
+namespace clang::tidy::altera {
 
 /// Detects OpenCL kernel functions that call a barrier but do not call an
 /// ID-function function. These functions will be treated as single work-item
@@ -33,8 +31,6 @@
   void storeOptions(ClangTidyOptions::OptionMap &Opts) override;
 };
 
-} // namespace altera
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::altera
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_ALTERA_SINGLE_WORK_ITEM_BARRIER_H
diff --git a/clang-tools-extra/clang-tidy/altera/StructPackAlignCheck.h b/clang-tools-extra/clang-tidy/altera/StructPackAlignCheck.h
--- a/clang-tools-extra/clang-tidy/altera/StructPackAlignCheck.h
+++ b/clang-tools-extra/clang-tidy/altera/StructPackAlignCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace altera {
+namespace clang::tidy::altera {
 
 /// Finds structs that are inefficiently packed or aligned, and recommends
 /// packing and/or aligning of said structs as needed.
@@ -34,8 +32,6 @@
   CharUnits computeRecommendedAlignment(CharUnits MinByteSize);
 };
 
-} // namespace altera
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::altera
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_ALTERA_STRUCTPACKALIGNCHECK_H
diff --git a/clang-tools-extra/clang-tidy/altera/UnrollLoopsCheck.h b/clang-tools-extra/clang-tidy/altera/UnrollLoopsCheck.h
--- a/clang-tools-extra/clang-tidy/altera/UnrollLoopsCheck.h
+++ b/clang-tools-extra/clang-tidy/altera/UnrollLoopsCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace altera {
+namespace clang::tidy::altera {
 
 /// Finds inner loops that have not been unrolled, as well as fully unrolled
 /// loops with unknown loop bounds or a large number of iterations.
@@ -71,8 +69,6 @@
   void storeOptions(ClangTidyOptions::OptionMap &Opts) override;
 };
 
-} // namespace altera
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::altera
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_ALTERA_UNROLLLOOPSCHECK_H
diff --git a/clang-tools-extra/clang-tidy/android/CloexecAccept4Check.h b/clang-tools-extra/clang-tidy/android/CloexecAccept4Check.h
--- a/clang-tools-extra/clang-tidy/android/CloexecAccept4Check.h
+++ b/clang-tools-extra/clang-tidy/android/CloexecAccept4Check.h
@@ -11,9 +11,7 @@
 
 #include "CloexecCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace android {
+namespace clang::tidy::android {
 
 /// Finds code that uses accept4() without using the SOCK_CLOEXEC flag.
 ///
@@ -27,8 +25,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace android
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::android
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_ANDROID_CLOEXEC_ACCEPT4_H
diff --git a/clang-tools-extra/clang-tidy/android/CloexecAcceptCheck.h b/clang-tools-extra/clang-tidy/android/CloexecAcceptCheck.h
--- a/clang-tools-extra/clang-tidy/android/CloexecAcceptCheck.h
+++ b/clang-tools-extra/clang-tidy/android/CloexecAcceptCheck.h
@@ -11,9 +11,7 @@
 
 #include "CloexecCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace android {
+namespace clang::tidy::android {
 
 /// accept() is better to be replaced by accept4().
 ///
@@ -27,8 +25,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace android
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::android
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_ANDROID_CLOEXEC_ACCEPT_H
diff --git a/clang-tools-extra/clang-tidy/android/CloexecCheck.h b/clang-tools-extra/clang-tidy/android/CloexecCheck.h
--- a/clang-tools-extra/clang-tidy/android/CloexecCheck.h
+++ b/clang-tools-extra/clang-tidy/android/CloexecCheck.h
@@ -17,9 +17,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace android {
+namespace clang::tidy::android {
 
 /// The base class for all close-on-exec checks in Android module.
 /// To be specific, there are some functions that need the close-on-exec flag to
@@ -97,8 +95,6 @@
   static const char *FuncBindingStr;
 };
 
-} // namespace android
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::android
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_ANDROID_CLOEXEC_H
diff --git a/clang-tools-extra/clang-tidy/android/CloexecCreatCheck.h b/clang-tools-extra/clang-tidy/android/CloexecCreatCheck.h
--- a/clang-tools-extra/clang-tidy/android/CloexecCreatCheck.h
+++ b/clang-tools-extra/clang-tidy/android/CloexecCreatCheck.h
@@ -11,9 +11,7 @@
 
 #include "CloexecCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace android {
+namespace clang::tidy::android {
 
 /// creat() is better to be replaced by open().
 /// Find the usage of creat() and redirect user to use open().
@@ -27,8 +25,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace android
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::android
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_ANDROID_CLOEXEC_CREAT_H
diff --git a/clang-tools-extra/clang-tidy/android/CloexecDupCheck.h b/clang-tools-extra/clang-tidy/android/CloexecDupCheck.h
--- a/clang-tools-extra/clang-tidy/android/CloexecDupCheck.h
+++ b/clang-tools-extra/clang-tidy/android/CloexecDupCheck.h
@@ -11,9 +11,7 @@
 
 #include "CloexecCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace android {
+namespace clang::tidy::android {
 
 /// dup() is better to be replaced by fcntl(), which has close-on-exec flag.
 /// Find the usage of dup() and redirect user to use fcntl().
@@ -28,8 +26,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace android
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::android
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_ANDROID_CLOEXEC_DUP_H
diff --git a/clang-tools-extra/clang-tidy/android/CloexecEpollCreate1Check.h b/clang-tools-extra/clang-tidy/android/CloexecEpollCreate1Check.h
--- a/clang-tools-extra/clang-tidy/android/CloexecEpollCreate1Check.h
+++ b/clang-tools-extra/clang-tidy/android/CloexecEpollCreate1Check.h
@@ -11,9 +11,7 @@
 
 #include "CloexecCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace android {
+namespace clang::tidy::android {
 
 /// Finds code that uses epoll_create1() without using the EPOLL_CLOEXEC flag.
 ///
@@ -27,8 +25,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace android
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::android
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_ANDROID_CLOEXEC_EPOLL_CREATE1_H
diff --git a/clang-tools-extra/clang-tidy/android/CloexecEpollCreateCheck.h b/clang-tools-extra/clang-tidy/android/CloexecEpollCreateCheck.h
--- a/clang-tools-extra/clang-tidy/android/CloexecEpollCreateCheck.h
+++ b/clang-tools-extra/clang-tidy/android/CloexecEpollCreateCheck.h
@@ -11,9 +11,7 @@
 
 #include "CloexecCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace android {
+namespace clang::tidy::android {
 
 /// epoll_create() is better to be replaced by epoll_create1().
 ///
@@ -27,8 +25,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace android
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::android
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_ANDROID_CLOEXEC_EPOLL_CREATE_H
diff --git a/clang-tools-extra/clang-tidy/android/CloexecFopenCheck.h b/clang-tools-extra/clang-tidy/android/CloexecFopenCheck.h
--- a/clang-tools-extra/clang-tidy/android/CloexecFopenCheck.h
+++ b/clang-tools-extra/clang-tidy/android/CloexecFopenCheck.h
@@ -11,9 +11,7 @@
 
 #include "CloexecCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace android {
+namespace clang::tidy::android {
 
 /// fopen() is suggested to include "e" in their mode string; like "re" would be
 /// better than "r".
@@ -30,8 +28,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace android
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::android
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_ANDROID_CLOEXEC_FOPEN_H
diff --git a/clang-tools-extra/clang-tidy/android/CloexecInotifyInit1Check.h b/clang-tools-extra/clang-tidy/android/CloexecInotifyInit1Check.h
--- a/clang-tools-extra/clang-tidy/android/CloexecInotifyInit1Check.h
+++ b/clang-tools-extra/clang-tidy/android/CloexecInotifyInit1Check.h
@@ -11,9 +11,7 @@
 
 #include "CloexecCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace android {
+namespace clang::tidy::android {
 
 /// Finds code that uses inotify_init1() without using the IN_CLOEXEC flag.
 ///
@@ -27,8 +25,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace android
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::android
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_ANDROID_CLOEXEC_INOTIFY_INIT1_H
diff --git a/clang-tools-extra/clang-tidy/android/CloexecInotifyInitCheck.h b/clang-tools-extra/clang-tidy/android/CloexecInotifyInitCheck.h
--- a/clang-tools-extra/clang-tidy/android/CloexecInotifyInitCheck.h
+++ b/clang-tools-extra/clang-tidy/android/CloexecInotifyInitCheck.h
@@ -11,9 +11,7 @@
 
 #include "CloexecCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace android {
+namespace clang::tidy::android {
 
 /// inotify_init() is better to be replaced by inotify_init1().
 ///
@@ -27,8 +25,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace android
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::android
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_ANDROID_CLOEXEC_INOTIFY_INIT_H
diff --git a/clang-tools-extra/clang-tidy/android/CloexecMemfdCreateCheck.h b/clang-tools-extra/clang-tidy/android/CloexecMemfdCreateCheck.h
--- a/clang-tools-extra/clang-tidy/android/CloexecMemfdCreateCheck.h
+++ b/clang-tools-extra/clang-tidy/android/CloexecMemfdCreateCheck.h
@@ -11,9 +11,7 @@
 
 #include "CloexecCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace android {
+namespace clang::tidy::android {
 
 /// Finds code that uses memfd_create() without using the MFD_CLOEXEC flag.
 ///
@@ -27,8 +25,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace android
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::android
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_ANDROID_CLOEXEC_MEMFD_CREATE_H
diff --git a/clang-tools-extra/clang-tidy/android/CloexecOpenCheck.h b/clang-tools-extra/clang-tidy/android/CloexecOpenCheck.h
--- a/clang-tools-extra/clang-tidy/android/CloexecOpenCheck.h
+++ b/clang-tools-extra/clang-tidy/android/CloexecOpenCheck.h
@@ -11,9 +11,7 @@
 
 #include "CloexecCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace android {
+namespace clang::tidy::android {
 
 /// Finds code that opens file without using the O_CLOEXEC flag.
 ///
@@ -32,8 +30,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace android
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::android
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_ANDROID_CLOEXEC_OPEN_H
diff --git a/clang-tools-extra/clang-tidy/android/CloexecPipe2Check.h b/clang-tools-extra/clang-tidy/android/CloexecPipe2Check.h
--- a/clang-tools-extra/clang-tidy/android/CloexecPipe2Check.h
+++ b/clang-tools-extra/clang-tidy/android/CloexecPipe2Check.h
@@ -11,9 +11,7 @@
 
 #include "CloexecCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace android {
+namespace clang::tidy::android {
 
 /// Finds code that uses pipe2() without using the O_CLOEXEC flag.
 ///
@@ -27,8 +25,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace android
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::android
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_ANDROID_CLOEXEC_PIPE2_H
diff --git a/clang-tools-extra/clang-tidy/android/CloexecPipeCheck.h b/clang-tools-extra/clang-tidy/android/CloexecPipeCheck.h
--- a/clang-tools-extra/clang-tidy/android/CloexecPipeCheck.h
+++ b/clang-tools-extra/clang-tidy/android/CloexecPipeCheck.h
@@ -11,9 +11,7 @@
 
 #include "CloexecCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace android {
+namespace clang::tidy::android {
 
 /// Suggests to replace calls to pipe() with calls to pipe2().
 ///
@@ -27,8 +25,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace android
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::android
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_ANDROID_CLOEXEC_PIPE_H
diff --git a/clang-tools-extra/clang-tidy/android/CloexecSocketCheck.h b/clang-tools-extra/clang-tidy/android/CloexecSocketCheck.h
--- a/clang-tools-extra/clang-tidy/android/CloexecSocketCheck.h
+++ b/clang-tools-extra/clang-tidy/android/CloexecSocketCheck.h
@@ -11,9 +11,7 @@
 
 #include "CloexecCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace android {
+namespace clang::tidy::android {
 
 /// Finds code that uses socket() without using the SOCK_CLOEXEC flag.
 ///
@@ -27,8 +25,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace android
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::android
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_ANDROID_CLOEXEC_SOCKET_H
diff --git a/clang-tools-extra/clang-tidy/android/ComparisonInTempFailureRetryCheck.h b/clang-tools-extra/clang-tidy/android/ComparisonInTempFailureRetryCheck.h
--- a/clang-tools-extra/clang-tidy/android/ComparisonInTempFailureRetryCheck.h
+++ b/clang-tools-extra/clang-tidy/android/ComparisonInTempFailureRetryCheck.h
@@ -14,9 +14,7 @@
 #include "llvm/ADT/StringRef.h"
 #include <string>
 
-namespace clang {
-namespace tidy {
-namespace android {
+namespace clang::tidy::android {
 
 /// Attempts to catch calls to TEMP_FAILURE_RETRY with a top-level comparison
 /// operation, like `TEMP_FAILURE_RETRY(read(...) != N)`. In these cases, the
@@ -35,8 +33,6 @@
   SmallVector<StringRef, 5> RetryMacros;
 };
 
-} // namespace android
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::android
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_ANDROID_COMPARISONINTEMPFAILURERETRYCHECK_H
diff --git a/clang-tools-extra/clang-tidy/boost/UseToStringCheck.h b/clang-tools-extra/clang-tidy/boost/UseToStringCheck.h
--- a/clang-tools-extra/clang-tidy/boost/UseToStringCheck.h
+++ b/clang-tools-extra/clang-tidy/boost/UseToStringCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace boost {
+namespace clang::tidy::boost {
 
 /// Finds calls to ``boost::lexical_cast<std::string>`` and
 /// ``boost::lexical_cast<std::wstring>`` and replaces them with
@@ -32,8 +30,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace boost
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::boost
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BOOST_USE_TO_STRING_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/ArgumentCommentCheck.h b/clang-tools-extra/clang-tidy/bugprone/ArgumentCommentCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/ArgumentCommentCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/ArgumentCommentCheck.h
@@ -12,9 +12,7 @@
 #include "../ClangTidyCheck.h"
 #include "llvm/Support/Regex.h"
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// Checks that argument comments match parameter names.
 ///
@@ -58,8 +56,6 @@
   bool shouldAddComment(const Expr *Arg) const;
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_ARGUMENTCOMMENTCHECK_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/AssertSideEffectCheck.h b/clang-tools-extra/clang-tidy/bugprone/AssertSideEffectCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/AssertSideEffectCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/AssertSideEffectCheck.h
@@ -14,9 +14,7 @@
 #include "llvm/ADT/StringRef.h"
 #include <string>
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// Finds `assert()` with side effect.
 ///
@@ -45,8 +43,6 @@
   const std::vector<StringRef> IgnoredFunctions;
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_ASSERTSIDEEFFECTCHECK_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/AssignmentInIfConditionCheck.h b/clang-tools-extra/clang-tidy/bugprone/AssignmentInIfConditionCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/AssignmentInIfConditionCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/AssignmentInIfConditionCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// Catches assignments within the condition clause of an if statement.
 ///
@@ -28,8 +26,6 @@
   void report(const Expr *AssignmentExpr);
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_ASSIGNMENTINIFCONDITIONCHECK_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/BadSignalToKillThreadCheck.h b/clang-tools-extra/clang-tidy/bugprone/BadSignalToKillThreadCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/BadSignalToKillThreadCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/BadSignalToKillThreadCheck.h
@@ -12,9 +12,7 @@
 #include "../ClangTidyCheck.h"
 #include <optional>
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// Finds ``pthread_kill`` function calls when thread is terminated by
 /// ``SIGTERM`` signal.
@@ -31,8 +29,6 @@
   std::optional<unsigned> SigtermValue;
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_BADSIGNALTOKILLTHREADCHECK_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/BoolPointerImplicitConversionCheck.h b/clang-tools-extra/clang-tidy/bugprone/BoolPointerImplicitConversionCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/BoolPointerImplicitConversionCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/BoolPointerImplicitConversionCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// Checks for conditions based on implicit conversion from a bool pointer to
 /// bool.
@@ -34,8 +32,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_BOOLPOINTERIMPLICITCONVERSIONCHECK_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/BranchCloneCheck.h b/clang-tools-extra/clang-tidy/bugprone/BranchCloneCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/BranchCloneCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/BranchCloneCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// A check for detecting if/else if/else chains where two or more branches are
 /// Type I clones of each other (that is, they contain identical code), for
@@ -31,8 +29,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_BRANCHCLONECHECK_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/CopyConstructorInitCheck.h b/clang-tools-extra/clang-tidy/bugprone/CopyConstructorInitCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/CopyConstructorInitCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/CopyConstructorInitCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// Finds copy constructors where the ctor don't call the copy constructor of
 /// the base class.
@@ -31,8 +29,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_COPY_CONSTRUCTOR_INIT_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/DanglingHandleCheck.h b/clang-tools-extra/clang-tidy/bugprone/DanglingHandleCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/DanglingHandleCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/DanglingHandleCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// Detect dangling references in value handlers like
 /// std::experimental::string_view.
@@ -35,8 +33,6 @@
   const ast_matchers::internal::Matcher<RecordDecl> IsAHandle;
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_DANGLING_HANDLE_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/DynamicStaticInitializersCheck.h b/clang-tools-extra/clang-tidy/bugprone/DynamicStaticInitializersCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/DynamicStaticInitializersCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/DynamicStaticInitializersCheck.h
@@ -12,9 +12,7 @@
 #include "../ClangTidyCheck.h"
 #include "../utils/FileExtensionsUtils.h"
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// Finds dynamically initialized static variables in header files.
 ///
@@ -40,8 +38,6 @@
   utils::FileExtensionsSet HeaderFileExtensions;
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_DYNAMIC_STATIC_INITIALIZERS_CHECK_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/EasilySwappableParametersCheck.h b/clang-tools-extra/clang-tidy/bugprone/EasilySwappableParametersCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/EasilySwappableParametersCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/EasilySwappableParametersCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// Finds function definitions where parameters of convertible types follow
 /// each other directly, making call sites prone to calling the function with
@@ -59,8 +57,6 @@
   const std::size_t NamePrefixSuffixSilenceDissimilarityTreshold;
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_EASILYSWAPPABLEPARAMETERSCHECK_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/ExceptionEscapeCheck.h b/clang-tools-extra/clang-tidy/bugprone/ExceptionEscapeCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/ExceptionEscapeCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/ExceptionEscapeCheck.h
@@ -13,9 +13,7 @@
 #include "../utils/ExceptionAnalyzer.h"
 #include "llvm/ADT/StringSet.h"
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// Finds functions which should not throw exceptions: Destructors, move
 /// constructors, move assignment operators, the main() function,
@@ -42,8 +40,6 @@
   utils::ExceptionAnalyzer Tracer;
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_EXCEPTION_ESCAPE_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/FoldInitTypeCheck.h b/clang-tools-extra/clang-tidy/bugprone/FoldInitTypeCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/FoldInitTypeCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/FoldInitTypeCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// Find and flag invalid initializer values in folds, e.g. std::accumulate.
 /// Example:
@@ -36,8 +34,6 @@
                const ASTContext &Context, const CallExpr &CallNode);
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_FOLD_INIT_TYPE_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/ForwardDeclarationNamespaceCheck.h b/clang-tools-extra/clang-tidy/bugprone/ForwardDeclarationNamespaceCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/ForwardDeclarationNamespaceCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/ForwardDeclarationNamespaceCheck.h
@@ -14,9 +14,7 @@
 #include <set>
 #include <vector>
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// Checks if an unused forward declaration is in a wrong namespace.
 ///
@@ -51,8 +49,6 @@
   llvm::SmallPtrSet<const Type *, 16> FriendTypes;
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_FORWARDDECLARATIONNAMESPACECHECK_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/ForwardingReferenceOverloadCheck.h b/clang-tools-extra/clang-tidy/bugprone/ForwardingReferenceOverloadCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/ForwardingReferenceOverloadCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/ForwardingReferenceOverloadCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// The checker looks for constructors that can act as copy or move constructors
 /// through their forwarding reference parameters. If a non const lvalue
@@ -37,8 +35,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_FORWARDINGREFERENCEOVERLOADCHECK_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/ImplicitWideningOfMultiplicationResultCheck.h b/clang-tools-extra/clang-tidy/bugprone/ImplicitWideningOfMultiplicationResultCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/ImplicitWideningOfMultiplicationResultCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/ImplicitWideningOfMultiplicationResultCheck.h
@@ -13,9 +13,7 @@
 #include "../utils/IncludeInserter.h"
 #include <optional>
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// Diagnoses instances of an implicit widening of multiplication result.
 ///
@@ -46,8 +44,6 @@
   utils::IncludeInserter IncludeInserter;
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_IMPLICITWIDENINGOFMULTIPLICATIONRESULTCHECK_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/InaccurateEraseCheck.h b/clang-tools-extra/clang-tidy/bugprone/InaccurateEraseCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/InaccurateEraseCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/InaccurateEraseCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// Checks for inaccurate use of the `erase()` method.
 ///
@@ -36,8 +34,6 @@
   }
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_INACCURATEERASECHECK_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/IncorrectRoundingsCheck.h b/clang-tools-extra/clang-tidy/bugprone/IncorrectRoundingsCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/IncorrectRoundingsCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/IncorrectRoundingsCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// Checks the usage of patterns known to produce incorrect rounding.
 /// Programmers often use
@@ -31,8 +29,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_INCORRECTROUNDINGSCHECK_H_
diff --git a/clang-tools-extra/clang-tidy/bugprone/InfiniteLoopCheck.h b/clang-tools-extra/clang-tidy/bugprone/InfiniteLoopCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/InfiniteLoopCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/InfiniteLoopCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// Finds obvious infinite loops (loops where the condition variable is
 /// not changed at all).
@@ -28,8 +26,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_INFINITELOOPCHECK_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/IntegerDivisionCheck.h b/clang-tools-extra/clang-tidy/bugprone/IntegerDivisionCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/IntegerDivisionCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/IntegerDivisionCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// Finds cases where integer division in a floating point context is likely to
 /// cause unintended loss of precision.
@@ -28,8 +26,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_INTEGER_DIVISION_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/LambdaFunctionNameCheck.h b/clang-tools-extra/clang-tidy/bugprone/LambdaFunctionNameCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/LambdaFunctionNameCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/LambdaFunctionNameCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// Detect when __func__ or __FUNCTION__ is being used from within a lambda. In
 /// that context, those expressions expand to the name of the call operator
@@ -44,8 +42,6 @@
   SourceRangeSet SuppressMacroExpansions;
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_LAMBDAFUNCTIONNAMECHECK_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/MacroParenthesesCheck.h b/clang-tools-extra/clang-tidy/bugprone/MacroParenthesesCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/MacroParenthesesCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/MacroParenthesesCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// Finds macros that can have unexpected behaviour due to missing parentheses.
 ///
@@ -36,8 +34,6 @@
                            Preprocessor *ModuleExpanderPP) override;
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_MACROPARENTHESESCHECK_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/MacroRepeatedSideEffectsCheck.h b/clang-tools-extra/clang-tidy/bugprone/MacroRepeatedSideEffectsCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/MacroRepeatedSideEffectsCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/MacroRepeatedSideEffectsCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// Checks for repeated argument with side effects in macros.
 class MacroRepeatedSideEffectsCheck : public ClangTidyCheck {
@@ -24,8 +22,6 @@
                            Preprocessor *ModuleExpanderPP) override;
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_MACROREPEATEDSIDEEFFECTSCHECK_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/MisplacedOperatorInStrlenInAllocCheck.h b/clang-tools-extra/clang-tidy/bugprone/MisplacedOperatorInStrlenInAllocCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/MisplacedOperatorInStrlenInAllocCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/MisplacedOperatorInStrlenInAllocCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// Finds cases where ``1`` is added to the string in the argument to a function
 /// in the ``strlen()`` family instead of the result and value is used as an
@@ -29,8 +27,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_MISPLACED_OPERATOR_IN_STRLEN_IN_ALLOC_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/MisplacedPointerArithmeticInAllocCheck.h b/clang-tools-extra/clang-tidy/bugprone/MisplacedPointerArithmeticInAllocCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/MisplacedPointerArithmeticInAllocCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/MisplacedPointerArithmeticInAllocCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// Finds cases where an integer is added to or subracted from the result of a
 /// memory allocation function instead of its argument.
@@ -29,8 +27,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_MISPLACED_OPERATOR_IN_ALLOC_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/MisplacedWideningCastCheck.h b/clang-tools-extra/clang-tidy/bugprone/MisplacedWideningCastCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/MisplacedWideningCastCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/MisplacedWideningCastCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// Find casts of calculation results to bigger type. Typically from int to
 /// long. If the intention of the cast is to avoid loss of precision then
@@ -38,8 +36,6 @@
   const bool CheckImplicitCasts;
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif
diff --git a/clang-tools-extra/clang-tidy/bugprone/MoveForwardingReferenceCheck.h b/clang-tools-extra/clang-tidy/bugprone/MoveForwardingReferenceCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/MoveForwardingReferenceCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/MoveForwardingReferenceCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// The check warns if std::move is applied to a forwarding reference (i.e. an
 /// rvalue reference of a function template argument type).
@@ -44,8 +42,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_MOVEFORWARDINGREFERENCECHECK_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/MultipleStatementMacroCheck.h b/clang-tools-extra/clang-tidy/bugprone/MultipleStatementMacroCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/MultipleStatementMacroCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/MultipleStatementMacroCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// Detect multiple statement macros that are used in unbraced conditionals.
 /// Only the first statement of the macro will be inside the conditional and the
@@ -29,8 +27,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_MULTIPLE_STATEMENT_MACRO_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/NoEscapeCheck.h b/clang-tools-extra/clang-tidy/bugprone/NoEscapeCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/NoEscapeCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/NoEscapeCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// Block arguments in `dispatch_async()` and `dispatch_after()` are guaranteed
 /// to escape. If those blocks capture any pointers with the `noescape`
@@ -32,8 +30,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_NOESCAPECHECK_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/NotNullTerminatedResultCheck.h b/clang-tools-extra/clang-tidy/bugprone/NotNullTerminatedResultCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/NotNullTerminatedResultCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/NotNullTerminatedResultCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// Finds function calls where it is possible to cause a not null-terminated
 /// result. Usually the proper length of a string is 'strlen(src) + 1' or
@@ -60,8 +58,6 @@
                const ast_matchers::MatchFinder::MatchResult &Result);
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_NOT_NULL_TERMINATED_RESULT_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/ParentVirtualCallCheck.h b/clang-tools-extra/clang-tidy/bugprone/ParentVirtualCallCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/ParentVirtualCallCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/ParentVirtualCallCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// Finds calls to grand..-parent virtual methods instead of parent's.
 ///
@@ -27,8 +25,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_PARENTVIRTUALCALLCHECK_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/PosixReturnCheck.h b/clang-tools-extra/clang-tidy/bugprone/PosixReturnCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/PosixReturnCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/PosixReturnCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 class PosixReturnCheck: public ClangTidyCheck {
 public:
@@ -23,8 +21,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_POSIX_RETURN_CHECK_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/RedundantBranchConditionCheck.h b/clang-tools-extra/clang-tidy/bugprone/RedundantBranchConditionCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/RedundantBranchConditionCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/RedundantBranchConditionCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// Finds condition variables in nested `if` statements that were also checked
 /// in the outer `if` statement and were not changed.
@@ -31,8 +29,6 @@
   }
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_REDUNDANTBRANCHCONDITIONCHECK_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/ReservedIdentifierCheck.h b/clang-tools-extra/clang-tidy/bugprone/ReservedIdentifierCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/ReservedIdentifierCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/ReservedIdentifierCheck.h
@@ -14,9 +14,7 @@
 #include <string>
 #include <vector>
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// Checks for usages of identifiers reserved for use by the implementation.
 ///
@@ -50,8 +48,6 @@
                        const NamingCheckFailure &Failure) const override;
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_RESERVEDIDENTIFIERCHECK_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/SharedPtrArrayMismatchCheck.h b/clang-tools-extra/clang-tidy/bugprone/SharedPtrArrayMismatchCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/SharedPtrArrayMismatchCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/SharedPtrArrayMismatchCheck.h
@@ -11,9 +11,7 @@
 
 #include "SmartPtrArrayMismatchCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// Find `std::shared_ptr<T>(new T[...])`, replace it (if applicable) with
 /// `std::shared_ptr<T[]>(new T[...])`.
@@ -31,8 +29,6 @@
   SmartPtrClassMatcher getSmartPointerClassMatcher() const override;
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_SHAREDPTRARRAYMISMATCHCHECK_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/SignalHandlerCheck.h b/clang-tools-extra/clang-tidy/bugprone/SignalHandlerCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/SignalHandlerCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/SignalHandlerCheck.h
@@ -14,9 +14,7 @@
 #include "llvm/ADT/DepthFirstIterator.h"
 #include "llvm/ADT/StringSet.h"
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// Checker for signal handler functions.
 ///
@@ -76,8 +74,6 @@
   llvm::StringSet<> ConformingFunctions;
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_SIGNALHANDLERCHECK_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/SignedCharMisuseCheck.h b/clang-tools-extra/clang-tidy/bugprone/SignedCharMisuseCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/SignedCharMisuseCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/SignedCharMisuseCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// Finds those ``signed char`` -> integer conversions which might indicate a
 /// programming error. The basic problem with the ``signed char``, that it might
@@ -41,8 +39,6 @@
   const bool DiagnoseSignedUnsignedCharComparisons;
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_SIGNEDCHARMISUSECHECK_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/SizeofContainerCheck.h b/clang-tools-extra/clang-tidy/bugprone/SizeofContainerCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/SizeofContainerCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/SizeofContainerCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// Find usages of sizeof on expressions of STL container types. Most likely the
 /// user wanted to use `.size()` instead.
@@ -28,8 +26,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_SIZEOFCONTAINERCHECK_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/SizeofExpressionCheck.h b/clang-tools-extra/clang-tidy/bugprone/SizeofExpressionCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/SizeofExpressionCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/SizeofExpressionCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// Find suspicious usages of sizeof expression.
 ///
@@ -34,8 +32,6 @@
   const bool WarnOnSizeOfPointerToAggregate;
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_SIZEOFEXPRESSIONCHECK_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/SmartPtrArrayMismatchCheck.h b/clang-tools-extra/clang-tidy/bugprone/SmartPtrArrayMismatchCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/SmartPtrArrayMismatchCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/SmartPtrArrayMismatchCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// Find constructions of smart (unique or shared) pointers where the pointer
 /// is declared with non-array target type and an array (created with a
@@ -45,8 +43,6 @@
   StringRef const SmartPointerName;
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_SMARTPTRARRAYMISMATCHCHECK_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/SpuriouslyWakeUpFunctionsCheck.h b/clang-tools-extra/clang-tidy/bugprone/SpuriouslyWakeUpFunctionsCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/SpuriouslyWakeUpFunctionsCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/SpuriouslyWakeUpFunctionsCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// Finds ``cnd_wait``, ``cnd_timedwait``, ``wait``, ``wait_for``, or 
 /// ``wait_until`` function calls when the function is not invoked from a loop 
@@ -30,8 +28,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_SPURIOUSLYWAKEUPFUNCTIONSCHECK_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/StandaloneEmptyCheck.h b/clang-tools-extra/clang-tidy/bugprone/StandaloneEmptyCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/StandaloneEmptyCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/StandaloneEmptyCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// Checks for ignored calls to `empty()` on a range and suggests `clear()`
 /// as an alternative if it is an existing member function.
@@ -31,8 +29,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_STANDALONEEMPTYCHECK_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/StringConstructorCheck.h b/clang-tools-extra/clang-tidy/bugprone/StringConstructorCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/StringConstructorCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/StringConstructorCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// Finds suspicious string constructor and check their parameters.
 ///
@@ -36,8 +34,6 @@
   std::vector<StringRef> StringNames;
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_STRING_CONSTRUCTOR_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/StringIntegerAssignmentCheck.h b/clang-tools-extra/clang-tidy/bugprone/StringIntegerAssignmentCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/StringIntegerAssignmentCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/StringIntegerAssignmentCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// Finds instances where an integer is assigned to a string.
 ///
@@ -30,8 +28,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_STRINGINTEGERASSIGNMENTCHECK_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/StringLiteralWithEmbeddedNulCheck.h b/clang-tools-extra/clang-tidy/bugprone/StringLiteralWithEmbeddedNulCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/StringLiteralWithEmbeddedNulCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/StringLiteralWithEmbeddedNulCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// Find suspicious string literals with embedded NUL characters.
 ///
@@ -27,8 +25,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_STRINGLITERALWITHEMBEDDEDNULCHECK_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/StringviewNullptrCheck.h b/clang-tools-extra/clang-tidy/bugprone/StringviewNullptrCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/StringviewNullptrCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/StringviewNullptrCheck.h
@@ -11,9 +11,7 @@
 
 #include "../utils/TransformerClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// Checks for various ways that the `const CharT*` constructor of
 /// `std::basic_string_view` can be passed a null argument and replaces them
@@ -42,8 +40,6 @@
   }
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_STRINGVIEWNULLPTRCHECK_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/SuspiciousEnumUsageCheck.h b/clang-tools-extra/clang-tidy/bugprone/SuspiciousEnumUsageCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/SuspiciousEnumUsageCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/SuspiciousEnumUsageCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// The checker detects various cases when an enum is probably misused (as a
 /// bitmask).
@@ -34,8 +32,6 @@
   const bool StrictMode;
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_SUSPICIOUSENUMUSAGECHECK_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/SuspiciousIncludeCheck.h b/clang-tools-extra/clang-tidy/bugprone/SuspiciousIncludeCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/SuspiciousIncludeCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/SuspiciousIncludeCheck.h
@@ -12,9 +12,7 @@
 #include "../ClangTidyCheck.h"
 #include "../utils/FileExtensionsUtils.h"
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// Warns on inclusion of files whose names suggest that they're implementation
 /// files, instead of headers. E.g:
@@ -50,8 +48,6 @@
   const StringRef RawStringImplementationFileExtensions;
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_SUSPICIOUSINCLUDECHECK_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/SuspiciousMemoryComparisonCheck.h b/clang-tools-extra/clang-tidy/bugprone/SuspiciousMemoryComparisonCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/SuspiciousMemoryComparisonCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/SuspiciousMemoryComparisonCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// Finds potentially incorrect calls to ``memcmp()`` based on properties of the
 /// arguments.
@@ -28,8 +26,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_SUSPICIOUSMEMORYCOMPARISONCHECK_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/SuspiciousMemsetUsageCheck.h b/clang-tools-extra/clang-tidy/bugprone/SuspiciousMemsetUsageCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/SuspiciousMemsetUsageCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/SuspiciousMemsetUsageCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// Finds memset calls with potential mistakes in their arguments.
 ///
@@ -30,8 +28,6 @@
   }
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_SUSPICIOUS_MEMSET_USAGE_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/SuspiciousMissingCommaCheck.h b/clang-tools-extra/clang-tidy/bugprone/SuspiciousMissingCommaCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/SuspiciousMissingCommaCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/SuspiciousMissingCommaCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// This check finds string literals which are probably concatenated
 /// accidentally.
@@ -36,8 +34,6 @@
   const unsigned MaxConcatenatedTokens;
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_SUSPICIOUSMISSINGCOMMACHECK_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/SuspiciousReallocUsageCheck.h b/clang-tools-extra/clang-tidy/bugprone/SuspiciousReallocUsageCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/SuspiciousReallocUsageCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/SuspiciousReallocUsageCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// Finds usages of ``realloc`` where the return value is assigned to the same
 /// variable as passed to the first argument.
@@ -29,8 +27,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_SUSPICIOUSREALLOCUSAGECHECK_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/SuspiciousSemicolonCheck.h b/clang-tools-extra/clang-tidy/bugprone/SuspiciousSemicolonCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/SuspiciousSemicolonCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/SuspiciousSemicolonCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// This check finds semicolon that modifies the meaning of the program
 /// unintendedly.
@@ -28,8 +26,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_SUSPICIOUSSEMICOLONCHECK_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/SuspiciousStringCompareCheck.h b/clang-tools-extra/clang-tidy/bugprone/SuspiciousStringCompareCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/SuspiciousStringCompareCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/SuspiciousStringCompareCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// Find suspicious calls to string compare functions.
 ///
@@ -32,8 +30,6 @@
   const StringRef StringCompareLikeFunctions;
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_SUSPICIOUSSTRINGCOMPARECHECK_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/SwappedArgumentsCheck.h b/clang-tools-extra/clang-tidy/bugprone/SwappedArgumentsCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/SwappedArgumentsCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/SwappedArgumentsCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// Finds potentially swapped arguments by looking at implicit conversions.
 class SwappedArgumentsCheck : public ClangTidyCheck {
@@ -24,8 +22,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_SWAPPEDARGUMENTSCHECK_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/TerminatingContinueCheck.h b/clang-tools-extra/clang-tidy/bugprone/TerminatingContinueCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/TerminatingContinueCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/TerminatingContinueCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// Checks if a 'continue' statement terminates the loop (i.e. the loop has
 ///	a condition which always evaluates to false).
@@ -28,8 +26,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_TERMINATINGCONTINUECHECK_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/ThrowKeywordMissingCheck.h b/clang-tools-extra/clang-tidy/bugprone/ThrowKeywordMissingCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/ThrowKeywordMissingCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/ThrowKeywordMissingCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// Emits a warning about temporary objects whose type is (or is derived from) a
 /// class that has 'EXCEPTION', 'Exception' or 'exception' in its name.
@@ -34,8 +32,6 @@
   }
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_THROWKEYWORDMISSINGCHECK_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/TooSmallLoopVariableCheck.h b/clang-tools-extra/clang-tidy/bugprone/TooSmallLoopVariableCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/TooSmallLoopVariableCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/TooSmallLoopVariableCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// This check gives a warning if a loop variable has a too small type which
 /// might not be able to represent all values which are part of the whole range
@@ -39,8 +37,6 @@
   const unsigned MagnitudeBitsUpperLimit;
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_TOOSMALLLOOPVARIABLECHECK_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/UncheckedOptionalAccessCheck.h b/clang-tools-extra/clang-tidy/bugprone/UncheckedOptionalAccessCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/UncheckedOptionalAccessCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/UncheckedOptionalAccessCheck.h
@@ -14,9 +14,7 @@
 #include "clang/Analysis/FlowSensitive/Models/UncheckedOptionalAccessModel.h"
 #include <optional>
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// Warns when the code is unwrapping a `std::optional<T>`, `absl::optional<T>`,
 /// or `base::std::optional<T>` object without assuring that it contains a
@@ -44,8 +42,6 @@
   dataflow::UncheckedOptionalAccessModelOptions ModelOptions;
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_UNCHECKEDOPTIONALACCESSCHECK_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/UndefinedMemoryManipulationCheck.h b/clang-tools-extra/clang-tidy/bugprone/UndefinedMemoryManipulationCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/UndefinedMemoryManipulationCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/UndefinedMemoryManipulationCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// Finds calls of memory manipulation functions ``memset()``, ``memcpy()`` and
 /// ``memmove()`` on not TriviallyCopyable objects resulting in undefined
@@ -29,8 +27,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_UNDEFINED_MEMORY_MANIPULATION_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/UndelegatedConstructorCheck.h b/clang-tools-extra/clang-tidy/bugprone/UndelegatedConstructorCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/UndelegatedConstructorCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/UndelegatedConstructorCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// Finds creation of temporary objects in constructors that look like a
 /// function call to another constructor of the same class.
@@ -31,8 +29,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MISC_UNDELEGATEDCONSTRUCTOR_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/UnhandledExceptionAtNewCheck.h b/clang-tools-extra/clang-tidy/bugprone/UnhandledExceptionAtNewCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/UnhandledExceptionAtNewCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/UnhandledExceptionAtNewCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// Finds calls to 'new' that may throw unhandled exception at allocation
 /// failure.
@@ -31,8 +29,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_UNHANDLEDEXCEPTIONATNEWCHECK_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/UnhandledSelfAssignmentCheck.h b/clang-tools-extra/clang-tidy/bugprone/UnhandledSelfAssignmentCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/UnhandledSelfAssignmentCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/UnhandledSelfAssignmentCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// Finds user-defined copy assignment operators which do not protect the code
 /// against self-assignment either by checking self-assignment explicitly or
@@ -36,8 +34,6 @@
   const bool WarnOnlyIfThisHasSuspiciousField;
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_UNHANDLEDSELFASSIGNMENTCHECK_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/UnusedRaiiCheck.h b/clang-tools-extra/clang-tidy/bugprone/UnusedRaiiCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/UnusedRaiiCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/UnusedRaiiCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// Finds temporaries that look like RAII objects.
 ///
@@ -33,8 +31,6 @@
   }
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_UNUSEDRAIICHECK_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/UnusedReturnValueCheck.h b/clang-tools-extra/clang-tidy/bugprone/UnusedReturnValueCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/UnusedReturnValueCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/UnusedReturnValueCheck.h
@@ -12,9 +12,7 @@
 #include "../ClangTidyCheck.h"
 #include <string>
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// Detects function calls where the return value is unused.
 ///
@@ -31,8 +29,6 @@
   std::string CheckedFunctions;
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_UNUSEDRETURNVALUECHECK_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/UseAfterMoveCheck.h b/clang-tools-extra/clang-tidy/bugprone/UseAfterMoveCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/UseAfterMoveCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/UseAfterMoveCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// The check warns if an object is used after it has been moved, without an
 /// intervening reinitialization.
@@ -31,8 +29,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_USEAFTERMOVECHECK_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/VirtualNearMissCheck.h b/clang-tools-extra/clang-tidy/bugprone/VirtualNearMissCheck.h
--- a/clang-tools-extra/clang-tidy/bugprone/VirtualNearMissCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/VirtualNearMissCheck.h
@@ -12,9 +12,7 @@
 #include "../ClangTidyCheck.h"
 #include "llvm/ADT/DenseMap.h"
 
-namespace clang {
-namespace tidy {
-namespace bugprone {
+namespace clang::tidy::bugprone {
 
 /// Checks for near miss of virtual methods.
 ///
@@ -60,8 +58,6 @@
   const unsigned EditDistanceThreshold = 1;
 };
 
-} // namespace bugprone
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::bugprone
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_VIRTUAL_NEAR_MISS_H
diff --git a/clang-tools-extra/clang-tidy/cert/CommandProcessorCheck.h b/clang-tools-extra/clang-tidy/cert/CommandProcessorCheck.h
--- a/clang-tools-extra/clang-tidy/cert/CommandProcessorCheck.h
+++ b/clang-tools-extra/clang-tidy/cert/CommandProcessorCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace cert {
+namespace clang::tidy::cert {
 
 /// Execution of a command processor can lead to security vulnerabilities,
 /// and is generally not required. Instead, prefer to launch executables
@@ -30,8 +28,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace cert
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cert
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_CERT_COMMAND_PROCESSOR_CHECK_H
diff --git a/clang-tools-extra/clang-tidy/cert/DefaultOperatorNewAlignmentCheck.h b/clang-tools-extra/clang-tidy/cert/DefaultOperatorNewAlignmentCheck.h
--- a/clang-tools-extra/clang-tidy/cert/DefaultOperatorNewAlignmentCheck.h
+++ b/clang-tools-extra/clang-tidy/cert/DefaultOperatorNewAlignmentCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace cert {
+namespace clang::tidy::cert {
 
 /// Checks if an object of type with extended alignment is allocated by using
 /// the default operator new.
@@ -31,8 +29,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace cert
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cert
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_CERT_DEFAULTOPERATORNEWALIGNMENTCHECK_H
diff --git a/clang-tools-extra/clang-tidy/cert/DontModifyStdNamespaceCheck.h b/clang-tools-extra/clang-tidy/cert/DontModifyStdNamespaceCheck.h
--- a/clang-tools-extra/clang-tidy/cert/DontModifyStdNamespaceCheck.h
+++ b/clang-tools-extra/clang-tidy/cert/DontModifyStdNamespaceCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace cert {
+namespace clang::tidy::cert {
 
 /// Modification of the std or posix namespace can result in undefined behavior.
 /// This check warns for such modifications.
@@ -31,8 +29,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace cert
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cert
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_CERT_DONT_MODIFY_STD_NAMESPACE_H
diff --git a/clang-tools-extra/clang-tidy/cert/FloatLoopCounter.h b/clang-tools-extra/clang-tidy/cert/FloatLoopCounter.h
--- a/clang-tools-extra/clang-tidy/cert/FloatLoopCounter.h
+++ b/clang-tools-extra/clang-tidy/cert/FloatLoopCounter.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace cert {
+namespace clang::tidy::cert {
 
 /// This check diagnoses when the loop induction expression of a for loop has
 /// floating-point type. The check corresponds to:
@@ -29,8 +27,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace cert
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cert
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_CERT_FLOAT_LOOP_COUNTER_H
diff --git a/clang-tools-extra/clang-tidy/cert/LimitedRandomnessCheck.h b/clang-tools-extra/clang-tidy/cert/LimitedRandomnessCheck.h
--- a/clang-tools-extra/clang-tidy/cert/LimitedRandomnessCheck.h
+++ b/clang-tools-extra/clang-tidy/cert/LimitedRandomnessCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace cert {
+namespace clang::tidy::cert {
 
 /// Pseudorandom number generators are not genuinely random. The result of the
 /// std::rand() function makes no guarantees as to the quality of the random
@@ -30,8 +28,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace cert
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cert
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_CERT_LIMITED_RANDOMNESS_H
diff --git a/clang-tools-extra/clang-tidy/cert/MutatingCopyCheck.h b/clang-tools-extra/clang-tidy/cert/MutatingCopyCheck.h
--- a/clang-tools-extra/clang-tidy/cert/MutatingCopyCheck.h
+++ b/clang-tools-extra/clang-tidy/cert/MutatingCopyCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace cert {
+namespace clang::tidy::cert {
 
 /// Finds assignments to the copied object and its direct or indirect members
 /// in copy constructors and copy assignment operators.
@@ -31,8 +29,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace cert
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cert
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_CERT_MUTATINGCOPYCHECK_H
diff --git a/clang-tools-extra/clang-tidy/cert/NonTrivialTypesLibcMemoryCallsCheck.h b/clang-tools-extra/clang-tidy/cert/NonTrivialTypesLibcMemoryCallsCheck.h
--- a/clang-tools-extra/clang-tidy/cert/NonTrivialTypesLibcMemoryCallsCheck.h
+++ b/clang-tools-extra/clang-tidy/cert/NonTrivialTypesLibcMemoryCallsCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace cert {
+namespace clang::tidy::cert {
 
 /// Flags use of the `C` standard library functions 'memset', 'memcpy' and
 /// 'memcmp' and similar derivatives on non-trivial types.
@@ -37,8 +35,6 @@
   const StringRef MemCmpNames;
 };
 
-} // namespace cert
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cert
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_CERT_NONTRIVIALTYPESLIBCMEMORYCALLSCHECK_H
diff --git a/clang-tools-extra/clang-tidy/cert/PostfixOperatorCheck.h b/clang-tools-extra/clang-tidy/cert/PostfixOperatorCheck.h
--- a/clang-tools-extra/clang-tidy/cert/PostfixOperatorCheck.h
+++ b/clang-tools-extra/clang-tidy/cert/PostfixOperatorCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace cert {
+namespace clang::tidy::cert {
 
 /// Checks if the overloaded postfix ++ and -- operator return a constant
 /// object.
@@ -31,8 +29,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace cert
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cert
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_CERT_POSTFIX_OPERATOR_H
diff --git a/clang-tools-extra/clang-tidy/cert/ProperlySeededRandomGeneratorCheck.h b/clang-tools-extra/clang-tidy/cert/ProperlySeededRandomGeneratorCheck.h
--- a/clang-tools-extra/clang-tidy/cert/ProperlySeededRandomGeneratorCheck.h
+++ b/clang-tools-extra/clang-tidy/cert/ProperlySeededRandomGeneratorCheck.h
@@ -12,9 +12,7 @@
 #include "../ClangTidyCheck.h"
 #include <string>
 
-namespace clang {
-namespace tidy {
-namespace cert {
+namespace clang::tidy::cert {
 
 /// Random number generator must be seeded properly.
 ///
@@ -39,8 +37,6 @@
   SmallVector<StringRef, 5> DisallowedSeedTypes;
 };
 
-} // namespace cert
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cert
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_CERT_PROPERLY_SEEDED_RANDOM_GENERATOR_H
diff --git a/clang-tools-extra/clang-tidy/cert/SetLongJmpCheck.h b/clang-tools-extra/clang-tidy/cert/SetLongJmpCheck.h
--- a/clang-tools-extra/clang-tidy/cert/SetLongJmpCheck.h
+++ b/clang-tools-extra/clang-tidy/cert/SetLongJmpCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace cert {
+namespace clang::tidy::cert {
 
 /// Guards against use of setjmp/longjmp in C++ code
 ///
@@ -32,8 +30,6 @@
                            Preprocessor *ModuleExpanderPP) override;
 };
 
-} // namespace cert
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cert
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_SETLONGJMPCHECK_H
diff --git a/clang-tools-extra/clang-tidy/cert/StaticObjectExceptionCheck.h b/clang-tools-extra/clang-tidy/cert/StaticObjectExceptionCheck.h
--- a/clang-tools-extra/clang-tidy/cert/StaticObjectExceptionCheck.h
+++ b/clang-tools-extra/clang-tidy/cert/StaticObjectExceptionCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace cert {
+namespace clang::tidy::cert {
 
 /// Checks whether the constructor for a static or thread_local object will
 /// throw.
@@ -31,8 +29,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace cert
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cert
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_CERT_ERR58_CPP_H
diff --git a/clang-tools-extra/clang-tidy/cert/StrToNumCheck.h b/clang-tools-extra/clang-tidy/cert/StrToNumCheck.h
--- a/clang-tools-extra/clang-tidy/cert/StrToNumCheck.h
+++ b/clang-tools-extra/clang-tidy/cert/StrToNumCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace cert {
+namespace clang::tidy::cert {
 
 /// Guards against use of string conversion functions that do not have
 /// reasonable error handling for conversion errors.
@@ -28,8 +26,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace cert
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cert
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_CERT_STRTONUMCHECK_H
diff --git a/clang-tools-extra/clang-tidy/cert/ThrownExceptionTypeCheck.h b/clang-tools-extra/clang-tidy/cert/ThrownExceptionTypeCheck.h
--- a/clang-tools-extra/clang-tidy/cert/ThrownExceptionTypeCheck.h
+++ b/clang-tools-extra/clang-tidy/cert/ThrownExceptionTypeCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace cert {
+namespace clang::tidy::cert {
 
 /// Checks whether a thrown object is nothrow copy constructible.
 ///
@@ -30,8 +28,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace cert
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cert
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_CERT_THROWNEXCEPTIONTYPECHECK_H
diff --git a/clang-tools-extra/clang-tidy/cert/VariadicFunctionDefCheck.h b/clang-tools-extra/clang-tidy/cert/VariadicFunctionDefCheck.h
--- a/clang-tools-extra/clang-tidy/cert/VariadicFunctionDefCheck.h
+++ b/clang-tools-extra/clang-tidy/cert/VariadicFunctionDefCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace cert {
+namespace clang::tidy::cert {
 
 /// Guards against any C-style variadic function definitions (not declarations).
 ///
@@ -30,8 +28,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace cert
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cert
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_CERT_VARIADICFUNCTIONDEF_H
diff --git a/clang-tools-extra/clang-tidy/concurrency/MtUnsafeCheck.h b/clang-tools-extra/clang-tidy/concurrency/MtUnsafeCheck.h
--- a/clang-tools-extra/clang-tidy/concurrency/MtUnsafeCheck.h
+++ b/clang-tools-extra/clang-tidy/concurrency/MtUnsafeCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace concurrency {
+namespace clang::tidy::concurrency {
 
 /// Checks that non-thread-safe functions are not used.
 ///
@@ -36,8 +34,6 @@
   const FunctionSet FuncSet;
 };
 
-} // namespace concurrency
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::concurrency
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_CONCURRENCY_MTUNSAFECHECK_H
diff --git a/clang-tools-extra/clang-tidy/concurrency/ThreadCanceltypeAsynchronousCheck.h b/clang-tools-extra/clang-tidy/concurrency/ThreadCanceltypeAsynchronousCheck.h
--- a/clang-tools-extra/clang-tidy/concurrency/ThreadCanceltypeAsynchronousCheck.h
+++ b/clang-tools-extra/clang-tidy/concurrency/ThreadCanceltypeAsynchronousCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace concurrency {
+namespace clang::tidy::concurrency {
 
 /// Finds ``pthread_setcanceltype`` function calls where a thread's
 /// cancellation type is set to asynchronous.
@@ -27,8 +25,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace concurrency
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::concurrency
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_CONCURRENCY_THREADCANCELTYPEASYNCHRONOUSCHECK_H
diff --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/AvoidConstOrRefDataMembersCheck.h b/clang-tools-extra/clang-tidy/cppcoreguidelines/AvoidConstOrRefDataMembersCheck.h
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/AvoidConstOrRefDataMembersCheck.h
+++ b/clang-tools-extra/clang-tidy/cppcoreguidelines/AvoidConstOrRefDataMembersCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace cppcoreguidelines {
+namespace clang::tidy::cppcoreguidelines {
 
 /// Const-qualified or reference data members in classes should be avoided, as
 /// they make the class non-copy-assignable.
@@ -31,8 +29,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace cppcoreguidelines
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cppcoreguidelines
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_CPPCOREGUIDELINES_AVOIDCONSTORREFDATAMEMBERSCHECK_H
diff --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/AvoidDoWhileCheck.h b/clang-tools-extra/clang-tidy/cppcoreguidelines/AvoidDoWhileCheck.h
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/AvoidDoWhileCheck.h
+++ b/clang-tools-extra/clang-tidy/cppcoreguidelines/AvoidDoWhileCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace cppcoreguidelines {
+namespace clang::tidy::cppcoreguidelines {
 
 /// do-while loops are less readable than plan while loops, and can lead to
 /// subtle bugs.
@@ -34,8 +32,6 @@
   bool IgnoreMacros;
 };
 
-} // namespace cppcoreguidelines
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cppcoreguidelines
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_CPPCOREGUIDELINES_AVOIDDOWHILECHECK_H
diff --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/AvoidGotoCheck.h b/clang-tools-extra/clang-tidy/cppcoreguidelines/AvoidGotoCheck.h
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/AvoidGotoCheck.h
+++ b/clang-tools-extra/clang-tidy/cppcoreguidelines/AvoidGotoCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace cppcoreguidelines {
+namespace clang::tidy::cppcoreguidelines {
 
 /// The usage of ``goto`` for control flow is error prone and should be replaced
 /// with looping constructs. Only forward jumps in nested loops are accepted.
@@ -31,8 +29,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace cppcoreguidelines
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cppcoreguidelines
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_CPPCOREGUIDELINES_AVOIDGOTOCHECK_H
diff --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/AvoidNonConstGlobalVariablesCheck.h b/clang-tools-extra/clang-tidy/cppcoreguidelines/AvoidNonConstGlobalVariablesCheck.h
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/AvoidNonConstGlobalVariablesCheck.h
+++ b/clang-tools-extra/clang-tidy/cppcoreguidelines/AvoidNonConstGlobalVariablesCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace cppcoreguidelines {
+namespace clang::tidy::cppcoreguidelines {
 
 /// Non-const global variables hide dependencies and make the dependencies
 /// subject to unpredictable changes.
@@ -28,8 +26,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace cppcoreguidelines
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cppcoreguidelines
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_CPPCOREGUIDELINES_AVOIDNONCONSTGLOBALVARIABLESCHECK_H
diff --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/AvoidReferenceCoroutineParametersCheck.h b/clang-tools-extra/clang-tidy/cppcoreguidelines/AvoidReferenceCoroutineParametersCheck.h
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/AvoidReferenceCoroutineParametersCheck.h
+++ b/clang-tools-extra/clang-tidy/cppcoreguidelines/AvoidReferenceCoroutineParametersCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace cppcoreguidelines {
+namespace clang::tidy::cppcoreguidelines {
 
 /// Warns on coroutines that accept reference parameters. Accessing a reference
 /// after a coroutine suspension point is not safe since the reference may no
@@ -33,8 +31,6 @@
   }
 };
 
-} // namespace cppcoreguidelines
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cppcoreguidelines
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_CPPCOREGUIDELINES_AVOIDREFERENCECOROUTINEPARAMETERSCHECK_H
diff --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/InitVariablesCheck.h b/clang-tools-extra/clang-tidy/cppcoreguidelines/InitVariablesCheck.h
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/InitVariablesCheck.h
+++ b/clang-tools-extra/clang-tidy/cppcoreguidelines/InitVariablesCheck.h
@@ -13,9 +13,7 @@
 #include "../utils/IncludeInserter.h"
 #include "../utils/OptionsUtils.h"
 
-namespace clang {
-namespace tidy {
-namespace cppcoreguidelines {
+namespace clang::tidy::cppcoreguidelines {
 
 /// Find uninitialized local variables.
 ///
@@ -35,8 +33,6 @@
   const StringRef MathHeader;
 };
 
-} // namespace cppcoreguidelines
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cppcoreguidelines
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_CPPCOREGUIDELINES_INITVARIABLESCHECK_H
diff --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/InterfacesGlobalInitCheck.h b/clang-tools-extra/clang-tidy/cppcoreguidelines/InterfacesGlobalInitCheck.h
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/InterfacesGlobalInitCheck.h
+++ b/clang-tools-extra/clang-tidy/cppcoreguidelines/InterfacesGlobalInitCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace cppcoreguidelines {
+namespace clang::tidy::cppcoreguidelines {
 
 /// Flags possible initialization order issues of static variables.
 ///
@@ -27,8 +25,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace cppcoreguidelines
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cppcoreguidelines
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_CPPCOREGUIDELINES_INTERFACES_GLOBAL_INIT_H
diff --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/MacroUsageCheck.h b/clang-tools-extra/clang-tidy/cppcoreguidelines/MacroUsageCheck.h
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/MacroUsageCheck.h
+++ b/clang-tools-extra/clang-tidy/cppcoreguidelines/MacroUsageCheck.h
@@ -15,8 +15,7 @@
 
 namespace clang {
 class MacroDirective;
-namespace tidy {
-namespace cppcoreguidelines {
+namespace tidy::cppcoreguidelines {
 
 /// Find macro usage that is considered problematic because better language
 /// constructs exist for the task.
@@ -48,8 +47,7 @@
   bool IgnoreCommandLineMacros;
 };
 
-} // namespace cppcoreguidelines
-} // namespace tidy
+} // namespace tidy::cppcoreguidelines
 } // namespace clang
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_CPPCOREGUIDELINES_MACROUSAGECHECK_H
diff --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/NarrowingConversionsCheck.h b/clang-tools-extra/clang-tidy/cppcoreguidelines/NarrowingConversionsCheck.h
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/NarrowingConversionsCheck.h
+++ b/clang-tools-extra/clang-tidy/cppcoreguidelines/NarrowingConversionsCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace cppcoreguidelines {
+namespace clang::tidy::cppcoreguidelines {
 
 /// Checks for narrowing conversions, e.g:
 ///   int i = 0;
@@ -106,8 +104,6 @@
   const bool PedanticMode;
 };
 
-} // namespace cppcoreguidelines
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cppcoreguidelines
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_CPPCOREGUIDELINES_NARROWING_CONVERSIONS_H
diff --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/NoMallocCheck.h b/clang-tools-extra/clang-tidy/cppcoreguidelines/NoMallocCheck.h
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/NoMallocCheck.h
+++ b/clang-tools-extra/clang-tidy/cppcoreguidelines/NoMallocCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace cppcoreguidelines {
+namespace clang::tidy::cppcoreguidelines {
 
 /// This checker is concerned with C-style memory management and suggest modern
 /// alternatives to it.
@@ -56,8 +54,6 @@
   const StringRef DeallocList;
 };
 
-} // namespace cppcoreguidelines
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cppcoreguidelines
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_CPPCOREGUIDELINES_NO_MALLOC_H
diff --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/OwningMemoryCheck.h b/clang-tools-extra/clang-tidy/cppcoreguidelines/OwningMemoryCheck.h
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/OwningMemoryCheck.h
+++ b/clang-tools-extra/clang-tidy/cppcoreguidelines/OwningMemoryCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace cppcoreguidelines {
+namespace clang::tidy::cppcoreguidelines {
 
 /// Checks for common use cases for gsl::owner and enforces the unique owner
 /// nature of it whenever possible.
@@ -58,8 +56,6 @@
   const StringRef LegacyResourceConsumers;
 };
 
-} // namespace cppcoreguidelines
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cppcoreguidelines
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_CPPCOREGUIDELINES_OWNING_MEMORY_H
diff --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/PreferMemberInitializerCheck.h b/clang-tools-extra/clang-tidy/cppcoreguidelines/PreferMemberInitializerCheck.h
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/PreferMemberInitializerCheck.h
+++ b/clang-tools-extra/clang-tidy/cppcoreguidelines/PreferMemberInitializerCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace cppcoreguidelines {
+namespace clang::tidy::cppcoreguidelines {
 
 /// Finds member initializations in the constructor body which can be placed
 /// into the initialization list instead.
@@ -34,8 +32,6 @@
   const bool UseAssignment;
 };
 
-} // namespace cppcoreguidelines
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cppcoreguidelines
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_CPPCOREGUIDELINES_PREFERMEMBERINITIALIZERCHECK_H
diff --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/ProBoundsArrayToPointerDecayCheck.h b/clang-tools-extra/clang-tidy/cppcoreguidelines/ProBoundsArrayToPointerDecayCheck.h
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/ProBoundsArrayToPointerDecayCheck.h
+++ b/clang-tools-extra/clang-tidy/cppcoreguidelines/ProBoundsArrayToPointerDecayCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace cppcoreguidelines {
+namespace clang::tidy::cppcoreguidelines {
 
 /// This check flags all array to pointer decays
 ///
@@ -30,8 +28,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace cppcoreguidelines
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cppcoreguidelines
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_CPPCOREGUIDELINES_PRO_BOUNDS_ARRAY_TO_POINTER_DECAY_H
diff --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/ProBoundsConstantArrayIndexCheck.h b/clang-tools-extra/clang-tidy/cppcoreguidelines/ProBoundsConstantArrayIndexCheck.h
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/ProBoundsConstantArrayIndexCheck.h
+++ b/clang-tools-extra/clang-tidy/cppcoreguidelines/ProBoundsConstantArrayIndexCheck.h
@@ -12,9 +12,7 @@
 #include "../ClangTidyCheck.h"
 #include "../utils/IncludeInserter.h"
 
-namespace clang {
-namespace tidy {
-namespace cppcoreguidelines {
+namespace clang::tidy::cppcoreguidelines {
 
 /// This checks that all array subscriptions on static arrays and std::arrays
 /// have a constant index and are within bounds
@@ -37,8 +35,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace cppcoreguidelines
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cppcoreguidelines
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_CPPCOREGUIDELINES_PRO_BOUNDS_CONSTANT_ARRAY_INDEX_H
diff --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/ProBoundsPointerArithmeticCheck.h b/clang-tools-extra/clang-tidy/cppcoreguidelines/ProBoundsPointerArithmeticCheck.h
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/ProBoundsPointerArithmeticCheck.h
+++ b/clang-tools-extra/clang-tidy/cppcoreguidelines/ProBoundsPointerArithmeticCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace cppcoreguidelines {
+namespace clang::tidy::cppcoreguidelines {
 
 /// Flags all kinds of pointer arithmetic that have result of pointer type, i.e.
 /// +, -, +=, -=, ++, --. In addition, the [] operator on pointers (not on
@@ -29,8 +27,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace cppcoreguidelines
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cppcoreguidelines
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_CPPCOREGUIDELINES_PRO_BOUNDS_POINTER_ARITHMETIC_H
diff --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeConstCastCheck.h b/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeConstCastCheck.h
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeConstCastCheck.h
+++ b/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeConstCastCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace cppcoreguidelines {
+namespace clang::tidy::cppcoreguidelines {
 
 /// This check flags all instances of const_cast
 ///
@@ -30,8 +28,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace cppcoreguidelines
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cppcoreguidelines
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_CPPCOREGUIDELINES_PRO_TYPE_CONST_CAST_H
diff --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeCstyleCastCheck.h b/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeCstyleCastCheck.h
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeCstyleCastCheck.h
+++ b/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeCstyleCastCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace cppcoreguidelines {
+namespace clang::tidy::cppcoreguidelines {
 
 /// This check flags all use of C-style casts that perform a static_cast
 /// downcast, const_cast, or reinterpret_cast.
@@ -31,8 +29,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace cppcoreguidelines
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cppcoreguidelines
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_CPPCOREGUIDELINES_PRO_TYPE_CSTYLE_CAST_H
diff --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeMemberInitCheck.h b/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeMemberInitCheck.h
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeMemberInitCheck.h
+++ b/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeMemberInitCheck.h
@@ -12,9 +12,7 @@
 #include "../ClangTidyCheck.h"
 #include "llvm/ADT/DenseSet.h"
 
-namespace clang {
-namespace tidy {
-namespace cppcoreguidelines {
+namespace clang::tidy::cppcoreguidelines {
 
 /// Implements C++ Core Guidelines Type.6.
 ///
@@ -79,8 +77,6 @@
   llvm::DenseSet<const FieldDecl *> HasRecordClassMemberSet;
 };
 
-} // namespace cppcoreguidelines
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cppcoreguidelines
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_CPPCOREGUIDELINES_PRO_TYPE_MEMBER_INIT_H
diff --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeReinterpretCastCheck.h b/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeReinterpretCastCheck.h
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeReinterpretCastCheck.h
+++ b/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeReinterpretCastCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace cppcoreguidelines {
+namespace clang::tidy::cppcoreguidelines {
 
 /// Flags all occurrences of reinterpret_cast
 ///
@@ -30,8 +28,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace cppcoreguidelines
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cppcoreguidelines
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_CPPCOREGUIDELINES_PRO_TYPE_REINTERPRETCAST_CHECK_H
diff --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeStaticCastDowncastCheck.h b/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeStaticCastDowncastCheck.h
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeStaticCastDowncastCheck.h
+++ b/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeStaticCastDowncastCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace cppcoreguidelines {
+namespace clang::tidy::cppcoreguidelines {
 
 /// Checks for usages of static_cast, where a base class is downcasted to a
 /// derived class.
@@ -31,8 +29,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace cppcoreguidelines
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cppcoreguidelines
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_CPPCOREGUIDELINES_PRO_TYPE_STATIC_CAST_DOWNCAST_H
diff --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeUnionAccessCheck.h b/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeUnionAccessCheck.h
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeUnionAccessCheck.h
+++ b/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeUnionAccessCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace cppcoreguidelines {
+namespace clang::tidy::cppcoreguidelines {
 
 /// This check flags all access to members of unions.
 /// Access to a union as a whole (e.g. passing to a function) is not flagged.
@@ -31,8 +29,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace cppcoreguidelines
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cppcoreguidelines
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_CPPCOREGUIDELINES_PRO_TYPE_UNION_ACCESS_H
diff --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeVarargCheck.h b/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeVarargCheck.h
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeVarargCheck.h
+++ b/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeVarargCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace cppcoreguidelines {
+namespace clang::tidy::cppcoreguidelines {
 
 /// This check flags all calls to c-style variadic functions and all use
 /// of va_arg.
@@ -33,8 +31,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace cppcoreguidelines
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cppcoreguidelines
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_CPPCOREGUIDELINES_PRO_TYPE_VARARG_H
diff --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/SlicingCheck.h b/clang-tools-extra/clang-tidy/cppcoreguidelines/SlicingCheck.h
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/SlicingCheck.h
+++ b/clang-tools-extra/clang-tidy/cppcoreguidelines/SlicingCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace cppcoreguidelines {
+namespace clang::tidy::cppcoreguidelines {
 
 /// Flags slicing (incomplete copying of an object's state) of member variables
 /// or vtable. See:
@@ -37,8 +35,6 @@
                                        const CXXRecordDecl &BaseDecl);
 };
 
-} // namespace cppcoreguidelines
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cppcoreguidelines
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_CPPCOREGUIDELINES_SLICING_H
diff --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/SpecialMemberFunctionsCheck.h b/clang-tools-extra/clang-tidy/cppcoreguidelines/SpecialMemberFunctionsCheck.h
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/SpecialMemberFunctionsCheck.h
+++ b/clang-tools-extra/clang-tidy/cppcoreguidelines/SpecialMemberFunctionsCheck.h
@@ -13,9 +13,7 @@
 
 #include "llvm/ADT/DenseMapInfo.h"
 
-namespace clang {
-namespace tidy {
-namespace cppcoreguidelines {
+namespace clang::tidy::cppcoreguidelines {
 
 /// Checks for classes where some, but not all, of the special member functions
 /// are defined.
@@ -72,9 +70,7 @@
   ClassDefiningSpecialMembersMap ClassWithSpecialMembers;
 };
 
-} // namespace cppcoreguidelines
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cppcoreguidelines
 
 namespace llvm {
 /// Specialization of DenseMapInfo to allow ClassDefId objects in DenseMaps
diff --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/VirtualClassDestructorCheck.h b/clang-tools-extra/clang-tidy/cppcoreguidelines/VirtualClassDestructorCheck.h
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/VirtualClassDestructorCheck.h
+++ b/clang-tools-extra/clang-tidy/cppcoreguidelines/VirtualClassDestructorCheck.h
@@ -12,9 +12,7 @@
 #include "../ClangTidyCheck.h"
 #include <string>
 
-namespace clang {
-namespace tidy {
-namespace cppcoreguidelines {
+namespace clang::tidy::cppcoreguidelines {
 
 /// Finds base classes whose destructor is neither public and virtual
 /// nor protected and non-virtual.
@@ -34,8 +32,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace cppcoreguidelines
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::cppcoreguidelines
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_CPPCOREGUIDELINES_VIRTUALCLASSDESTRUCTORCHECK_H
diff --git a/clang-tools-extra/clang-tidy/darwin/AvoidSpinlockCheck.h b/clang-tools-extra/clang-tidy/darwin/AvoidSpinlockCheck.h
--- a/clang-tools-extra/clang-tidy/darwin/AvoidSpinlockCheck.h
+++ b/clang-tools-extra/clang-tidy/darwin/AvoidSpinlockCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace darwin {
+namespace clang::tidy::darwin {
 
 /// Finds usages of OSSpinlock, which is deprecated due to potential livelock
 /// problems.
@@ -28,8 +26,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-}  // namespace darwin
-}  // namespace tidy
-}  // namespace clang
+} // namespace clang::tidy::darwin
 
 #endif  // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_DARWIN_AVOIDSPINLOCKCHECK_H
diff --git a/clang-tools-extra/clang-tidy/darwin/DispatchOnceNonstaticCheck.h b/clang-tools-extra/clang-tidy/darwin/DispatchOnceNonstaticCheck.h
--- a/clang-tools-extra/clang-tidy/darwin/DispatchOnceNonstaticCheck.h
+++ b/clang-tools-extra/clang-tidy/darwin/DispatchOnceNonstaticCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace darwin {
+namespace clang::tidy::darwin {
 
 /// Finds variables of type dispatch_once_t that do not have static or global
 /// storage duration, as required by the libdispatch documentation.
@@ -28,8 +26,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace darwin
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::darwin
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_DARWIN_DISPATCHONCENONSTATICCHECK_H
diff --git a/clang-tools-extra/clang-tidy/fuchsia/DefaultArgumentsCallsCheck.h b/clang-tools-extra/clang-tidy/fuchsia/DefaultArgumentsCallsCheck.h
--- a/clang-tools-extra/clang-tidy/fuchsia/DefaultArgumentsCallsCheck.h
+++ b/clang-tools-extra/clang-tidy/fuchsia/DefaultArgumentsCallsCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace fuchsia {
+namespace clang::tidy::fuchsia {
 
 /// Default arguments are not allowed in called functions.
 ///
@@ -27,8 +25,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace fuchsia
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::fuchsia
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_FUCHSIA_DEFAULT_ARGUMENTS_CALLS_H
diff --git a/clang-tools-extra/clang-tidy/fuchsia/DefaultArgumentsDeclarationsCheck.h b/clang-tools-extra/clang-tidy/fuchsia/DefaultArgumentsDeclarationsCheck.h
--- a/clang-tools-extra/clang-tidy/fuchsia/DefaultArgumentsDeclarationsCheck.h
+++ b/clang-tools-extra/clang-tidy/fuchsia/DefaultArgumentsDeclarationsCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace fuchsia {
+namespace clang::tidy::fuchsia {
 
 /// Default parameters are not allowed in declared functions.
 ///
@@ -27,8 +25,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace fuchsia
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::fuchsia
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_FUCHSIA_DEFAULT_ARGUMENTS_DECLARATIONS_H
diff --git a/clang-tools-extra/clang-tidy/fuchsia/MultipleInheritanceCheck.h b/clang-tools-extra/clang-tidy/fuchsia/MultipleInheritanceCheck.h
--- a/clang-tools-extra/clang-tidy/fuchsia/MultipleInheritanceCheck.h
+++ b/clang-tools-extra/clang-tidy/fuchsia/MultipleInheritanceCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace fuchsia {
+namespace clang::tidy::fuchsia {
 
 /// Multiple implementation inheritance is discouraged.
 ///
@@ -43,8 +41,6 @@
   llvm::StringMap<bool> InterfaceMap;
 };
 
-} // namespace fuchsia
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::fuchsia
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_FUCHSIA_MULTIPLE_INHERITANCE_H
diff --git a/clang-tools-extra/clang-tidy/fuchsia/OverloadedOperatorCheck.h b/clang-tools-extra/clang-tidy/fuchsia/OverloadedOperatorCheck.h
--- a/clang-tools-extra/clang-tidy/fuchsia/OverloadedOperatorCheck.h
+++ b/clang-tools-extra/clang-tidy/fuchsia/OverloadedOperatorCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace fuchsia {
+namespace clang::tidy::fuchsia {
 
 /// Overloading operators is disallowed by the Fuchsia coding standard.
 ///
@@ -27,8 +25,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace fuchsia
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::fuchsia
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_FUCHSIA_OVERLOADED_OPERATOR_H
diff --git a/clang-tools-extra/clang-tidy/fuchsia/StaticallyConstructedObjectsCheck.h b/clang-tools-extra/clang-tidy/fuchsia/StaticallyConstructedObjectsCheck.h
--- a/clang-tools-extra/clang-tidy/fuchsia/StaticallyConstructedObjectsCheck.h
+++ b/clang-tools-extra/clang-tidy/fuchsia/StaticallyConstructedObjectsCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace fuchsia {
+namespace clang::tidy::fuchsia {
 
 /// Constructing global, non-trivial objects with static storage is
 /// disallowed, unless the object is statically initialized with a constexpr 
@@ -32,8 +30,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace fuchsia
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::fuchsia
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_FUCHSIA_STATICALLY_CONSTRUCTED_OBJECTS_H
diff --git a/clang-tools-extra/clang-tidy/fuchsia/TrailingReturnCheck.h b/clang-tools-extra/clang-tidy/fuchsia/TrailingReturnCheck.h
--- a/clang-tools-extra/clang-tidy/fuchsia/TrailingReturnCheck.h
+++ b/clang-tools-extra/clang-tidy/fuchsia/TrailingReturnCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace fuchsia {
+namespace clang::tidy::fuchsia {
 
 /// Functions that have trailing returns are disallowed, except for those 
 /// using decltype specifiers and lambda with otherwise unutterable 
@@ -32,8 +30,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace fuchsia
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::fuchsia
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_FUCHSIA_TRAILING_RETURN_H
diff --git a/clang-tools-extra/clang-tidy/fuchsia/VirtualInheritanceCheck.h b/clang-tools-extra/clang-tidy/fuchsia/VirtualInheritanceCheck.h
--- a/clang-tools-extra/clang-tidy/fuchsia/VirtualInheritanceCheck.h
+++ b/clang-tools-extra/clang-tidy/fuchsia/VirtualInheritanceCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace fuchsia {
+namespace clang::tidy::fuchsia {
 
 /// Defining classes with virtual inheritance is disallowed.
 ///
@@ -27,8 +25,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-}  // namespace fuchsia
-}  // namespace tidy
-}  // namespace clang
+} // namespace clang::tidy::fuchsia
 
 #endif  // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_FUCHSIA_VIRTUAL_INHERITANCE_H
diff --git a/clang-tools-extra/clang-tidy/google/AvoidCStyleCastsCheck.h b/clang-tools-extra/clang-tidy/google/AvoidCStyleCastsCheck.h
--- a/clang-tools-extra/clang-tidy/google/AvoidCStyleCastsCheck.h
+++ b/clang-tools-extra/clang-tidy/google/AvoidCStyleCastsCheck.h
@@ -11,10 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace google {
-namespace readability {
+namespace clang::tidy::google::readability {
 
 /// Finds usages of C-style casts.
 ///
@@ -36,9 +33,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace readability
-} // namespace google
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::google::readability
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_GOOGLE_AVOIDCSTYLECASTSCHECK_H
diff --git a/clang-tools-extra/clang-tidy/google/AvoidNSObjectNewCheck.h b/clang-tools-extra/clang-tidy/google/AvoidNSObjectNewCheck.h
--- a/clang-tools-extra/clang-tidy/google/AvoidNSObjectNewCheck.h
+++ b/clang-tools-extra/clang-tidy/google/AvoidNSObjectNewCheck.h
@@ -11,10 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace google {
-namespace objc {
+namespace clang::tidy::google::objc {
 
 /// This check finds Objective-C code that uses +new to create object instances,
 /// or overrides +new in classes. Both are forbidden by Google's Objective-C
@@ -33,9 +30,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace objc
-} // namespace google
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::google::objc
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_GOOGLE_AVOIDNSOBJECTNEWCHECK_H
diff --git a/clang-tools-extra/clang-tidy/google/AvoidThrowingObjCExceptionCheck.h b/clang-tools-extra/clang-tidy/google/AvoidThrowingObjCExceptionCheck.h
--- a/clang-tools-extra/clang-tidy/google/AvoidThrowingObjCExceptionCheck.h
+++ b/clang-tools-extra/clang-tidy/google/AvoidThrowingObjCExceptionCheck.h
@@ -11,10 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace google {
-namespace objc {
+namespace clang::tidy::google::objc {
 
 /// The check is to find usage of @throw invocation in Objective-C code.
 /// We should avoid using @throw for Objective-C exceptions according to
@@ -33,9 +30,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-}  // namespace objc
-}  // namespace google
-}  // namespace tidy
-}  // namespace clang
+} // namespace clang::tidy::google::objc
 
 #endif  // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_GOOGLE_OBJC_AVOID_THROWING_EXCEPTION_H
diff --git a/clang-tools-extra/clang-tidy/google/AvoidUnderscoreInGoogletestNameCheck.h b/clang-tools-extra/clang-tidy/google/AvoidUnderscoreInGoogletestNameCheck.h
--- a/clang-tools-extra/clang-tidy/google/AvoidUnderscoreInGoogletestNameCheck.h
+++ b/clang-tools-extra/clang-tidy/google/AvoidUnderscoreInGoogletestNameCheck.h
@@ -11,10 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace google {
-namespace readability {
+namespace clang::tidy::google::readability {
 
 // Check for underscores in the names of googletest tests, per
 // https://google.github.io/googletest/faq.html#why-should-test-suite-names-and-test-names-not-contain-underscore
@@ -29,9 +26,6 @@
                            Preprocessor *ModuleExpanderPP) override;
 };
 
-} // namespace readability
-} // namespace google
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::google::readability
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_GOOGLE_AVOIDUNDERSCOREINGOOGLETESTNAMECHECK_H
diff --git a/clang-tools-extra/clang-tidy/google/DefaultArgumentsCheck.h b/clang-tools-extra/clang-tidy/google/DefaultArgumentsCheck.h
--- a/clang-tools-extra/clang-tidy/google/DefaultArgumentsCheck.h
+++ b/clang-tools-extra/clang-tidy/google/DefaultArgumentsCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace google {
+namespace clang::tidy::google {
 
 /// Checks that default parameters are not given for virtual methods.
 ///
@@ -29,8 +27,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace google
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::google
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_GOOGLE_DEFAULT_ARGUMENTS_H
diff --git a/clang-tools-extra/clang-tidy/google/ExplicitConstructorCheck.h b/clang-tools-extra/clang-tidy/google/ExplicitConstructorCheck.h
--- a/clang-tools-extra/clang-tidy/google/ExplicitConstructorCheck.h
+++ b/clang-tools-extra/clang-tidy/google/ExplicitConstructorCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace google {
+namespace clang::tidy::google {
 
 /// Checks that all single-argument constructors are explicit.
 ///
@@ -32,8 +30,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace google
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::google
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_GOOGLE_EXPLICITCONSTRUCTORCHECK_H
diff --git a/clang-tools-extra/clang-tidy/google/ExplicitMakePairCheck.h b/clang-tools-extra/clang-tidy/google/ExplicitMakePairCheck.h
--- a/clang-tools-extra/clang-tidy/google/ExplicitMakePairCheck.h
+++ b/clang-tools-extra/clang-tidy/google/ExplicitMakePairCheck.h
@@ -11,10 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace google {
-namespace build {
+namespace clang::tidy::google::build {
 
 /// Check that `make_pair`'s template arguments are deduced.
 ///
@@ -36,9 +33,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace build
-} // namespace google
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::google::build
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_GOOGLE_EXPLICITMAKEPAIRCHECK_H
diff --git a/clang-tools-extra/clang-tidy/google/FunctionNamingCheck.h b/clang-tools-extra/clang-tidy/google/FunctionNamingCheck.h
--- a/clang-tools-extra/clang-tidy/google/FunctionNamingCheck.h
+++ b/clang-tools-extra/clang-tidy/google/FunctionNamingCheck.h
@@ -12,10 +12,7 @@
 #include "../ClangTidyCheck.h"
 #include "llvm/ADT/StringRef.h"
 
-namespace clang {
-namespace tidy {
-namespace google {
-namespace objc {
+namespace clang::tidy::google::objc {
 
 /// Finds function names that do not conform to the recommendations of the
 /// Google Objective-C Style Guide. Function names should be in upper camel case
@@ -37,9 +34,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace objc
-} // namespace google
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::google::objc
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_GOOGLE_OBJC_FUNCTION_NAMING_CHECK_H
diff --git a/clang-tools-extra/clang-tidy/google/GlobalNamesInHeadersCheck.h b/clang-tools-extra/clang-tidy/google/GlobalNamesInHeadersCheck.h
--- a/clang-tools-extra/clang-tidy/google/GlobalNamesInHeadersCheck.h
+++ b/clang-tools-extra/clang-tidy/google/GlobalNamesInHeadersCheck.h
@@ -12,10 +12,7 @@
 #include "../ClangTidyCheck.h"
 #include "../utils/FileExtensionsUtils.h"
 
-namespace clang {
-namespace tidy {
-namespace google {
-namespace readability {
+namespace clang::tidy::google::readability {
 
 /// Flag global namespace pollution in header files.
 /// Right now it only triggers on using declarations and directives.
@@ -42,9 +39,6 @@
   utils::FileExtensionsSet HeaderFileExtensions;
 };
 
-} // namespace readability
-} // namespace google
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::google::readability
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_GOOGLE_GLOBALNAMESINHEADERSCHECK_H
diff --git a/clang-tools-extra/clang-tidy/google/GlobalVariableDeclarationCheck.h b/clang-tools-extra/clang-tidy/google/GlobalVariableDeclarationCheck.h
--- a/clang-tools-extra/clang-tidy/google/GlobalVariableDeclarationCheck.h
+++ b/clang-tools-extra/clang-tidy/google/GlobalVariableDeclarationCheck.h
@@ -11,10 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace google {
-namespace objc {
+namespace clang::tidy::google::objc {
 
 /// The check for Objective-C global variables and constants naming convention.
 /// The declaration should follow the patterns of 'k[A-Z].*' (constants) or
@@ -33,9 +30,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-}  // namespace objc
-}  // namespace google
-}  // namespace tidy
-}  // namespace clang
+} // namespace clang::tidy::google::objc
 
 #endif  // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_GOOGLE_OBJC_GLOBAL_VARIABLE_DECLARATION_H
diff --git a/clang-tools-extra/clang-tidy/google/IntegerTypesCheck.h b/clang-tools-extra/clang-tidy/google/IntegerTypesCheck.h
--- a/clang-tools-extra/clang-tidy/google/IntegerTypesCheck.h
+++ b/clang-tools-extra/clang-tidy/google/IntegerTypesCheck.h
@@ -17,9 +17,7 @@
 
 class IdentifierTable;
 
-namespace tidy {
-namespace google {
-namespace runtime {
+namespace tidy::google::runtime {
 
 /// Finds uses of `short`, `long` and `long long` and suggest replacing them
 /// with `u?intXX(_t)?`.
@@ -46,9 +44,7 @@
   std::unique_ptr<IdentifierTable> IdentTable;
 };
 
-} // namespace runtime
-} // namespace google
-} // namespace tidy
+} // namespace tidy::google::runtime
 } // namespace clang
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_GOOGLE_INTEGERTYPESCHECK_H
diff --git a/clang-tools-extra/clang-tidy/google/OverloadedUnaryAndCheck.h b/clang-tools-extra/clang-tidy/google/OverloadedUnaryAndCheck.h
--- a/clang-tools-extra/clang-tidy/google/OverloadedUnaryAndCheck.h
+++ b/clang-tools-extra/clang-tidy/google/OverloadedUnaryAndCheck.h
@@ -11,10 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace google {
-namespace runtime {
+namespace clang::tidy::google::runtime {
 
 /// Finds overloads of unary `operator &`.
 ///
@@ -35,9 +32,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace runtime
-} // namespace google
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::google::runtime
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_GOOGLE_OVERLOADEDUNARYANDCHECK_H
diff --git a/clang-tools-extra/clang-tidy/google/TodoCommentCheck.h b/clang-tools-extra/clang-tidy/google/TodoCommentCheck.h
--- a/clang-tools-extra/clang-tidy/google/TodoCommentCheck.h
+++ b/clang-tools-extra/clang-tidy/google/TodoCommentCheck.h
@@ -11,10 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace google {
-namespace readability {
+namespace clang::tidy::google::readability {
 
 /// Finds TODO comments without a username or bug number.
 ///
@@ -35,9 +32,6 @@
   std::unique_ptr<TodoCommentHandler> Handler;
 };
 
-} // namespace readability
-} // namespace google
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::google::readability
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_GOOGLE_TODOCOMMENTCHECK_H
diff --git a/clang-tools-extra/clang-tidy/google/UnnamedNamespaceInHeaderCheck.h b/clang-tools-extra/clang-tidy/google/UnnamedNamespaceInHeaderCheck.h
--- a/clang-tools-extra/clang-tidy/google/UnnamedNamespaceInHeaderCheck.h
+++ b/clang-tools-extra/clang-tidy/google/UnnamedNamespaceInHeaderCheck.h
@@ -12,10 +12,7 @@
 #include "../ClangTidyCheck.h"
 #include "../utils/FileExtensionsUtils.h"
 
-namespace clang {
-namespace tidy {
-namespace google {
-namespace build {
+namespace clang::tidy::google::build {
 
 /// Finds anonymous namespaces in headers.
 ///
@@ -48,9 +45,6 @@
   utils::FileExtensionsSet HeaderFileExtensions;
 };
 
-} // namespace build
-} // namespace google
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::google::build
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_GOOGLE_UNNAMEDNAMESPACEINHEADERCHECK_H
diff --git a/clang-tools-extra/clang-tidy/google/UpgradeGoogletestCaseCheck.h b/clang-tools-extra/clang-tidy/google/UpgradeGoogletestCaseCheck.h
--- a/clang-tools-extra/clang-tidy/google/UpgradeGoogletestCaseCheck.h
+++ b/clang-tools-extra/clang-tidy/google/UpgradeGoogletestCaseCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace google {
+namespace clang::tidy::google {
 
 /// Finds uses of deprecated Googletest APIs with names containing "case" and
 /// replaces them with equivalent names containing "suite".
@@ -36,8 +34,6 @@
   llvm::DenseSet<SourceLocation> MatchedTemplateLocations;
 };
 
-} // namespace google
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::google
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_GOOGLE_UPGRADEGOOGLETESTCASECHECK_H
diff --git a/clang-tools-extra/clang-tidy/google/UsingNamespaceDirectiveCheck.h b/clang-tools-extra/clang-tidy/google/UsingNamespaceDirectiveCheck.h
--- a/clang-tools-extra/clang-tidy/google/UsingNamespaceDirectiveCheck.h
+++ b/clang-tools-extra/clang-tidy/google/UsingNamespaceDirectiveCheck.h
@@ -11,10 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace google {
-namespace build {
+namespace clang::tidy::google::build {
 
 /// Finds using namespace directives.
 ///
@@ -48,9 +45,6 @@
   static bool isStdLiteralsNamespace(const NamespaceDecl *NS);
 };
 
-} // namespace build
-} // namespace google
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::google::build
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_GOOGLE_USINGNAMESPACEDIRECTIVECHECK_H
diff --git a/clang-tools-extra/clang-tidy/hicpp/ExceptionBaseclassCheck.h b/clang-tools-extra/clang-tidy/hicpp/ExceptionBaseclassCheck.h
--- a/clang-tools-extra/clang-tidy/hicpp/ExceptionBaseclassCheck.h
+++ b/clang-tools-extra/clang-tidy/hicpp/ExceptionBaseclassCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace hicpp {
+namespace clang::tidy::hicpp {
 
 /// Check for thrown exceptions and enforce they are all derived from std::exception.
 ///
@@ -30,8 +28,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace hicpp
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::hicpp
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_HICPP_EXCEPTION_BASECLASS_H
diff --git a/clang-tools-extra/clang-tidy/hicpp/MultiwayPathsCoveredCheck.h b/clang-tools-extra/clang-tidy/hicpp/MultiwayPathsCoveredCheck.h
--- a/clang-tools-extra/clang-tidy/hicpp/MultiwayPathsCoveredCheck.h
+++ b/clang-tools-extra/clang-tidy/hicpp/MultiwayPathsCoveredCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace hicpp {
+namespace clang::tidy::hicpp {
 
 /// Find occasions where not all codepaths are explicitly covered in code.
 /// This includes 'switch' without a 'default'-branch and 'if'-'else if'-chains
@@ -41,8 +39,6 @@
   const bool WarnOnMissingElse;
 };
 
-} // namespace hicpp
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::hicpp
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_HICPP_MULTIWAY_PATHS_COVERED_H
diff --git a/clang-tools-extra/clang-tidy/hicpp/NoAssemblerCheck.h b/clang-tools-extra/clang-tidy/hicpp/NoAssemblerCheck.h
--- a/clang-tools-extra/clang-tidy/hicpp/NoAssemblerCheck.h
+++ b/clang-tools-extra/clang-tidy/hicpp/NoAssemblerCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace hicpp {
+namespace clang::tidy::hicpp {
 
 /// Find assembler statements. No fix is offered.
 ///
@@ -27,8 +25,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace hicpp
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::hicpp
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_HICPP_NO_ASSEMBLER_H
diff --git a/clang-tools-extra/clang-tidy/hicpp/SignedBitwiseCheck.h b/clang-tools-extra/clang-tidy/hicpp/SignedBitwiseCheck.h
--- a/clang-tools-extra/clang-tidy/hicpp/SignedBitwiseCheck.h
+++ b/clang-tools-extra/clang-tidy/hicpp/SignedBitwiseCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace hicpp {
+namespace clang::tidy::hicpp {
 
 /// This check implements the rule 5.6.1 of the HICPP Standard, which disallows
 /// bitwise operations on signed integer types.
@@ -31,8 +29,6 @@
   bool IgnorePositiveIntegerLiterals;
 };
 
-} // namespace hicpp
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::hicpp
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_HICPP_SIGNED_BITWISE_H
diff --git a/clang-tools-extra/clang-tidy/linuxkernel/MustCheckErrsCheck.h b/clang-tools-extra/clang-tidy/linuxkernel/MustCheckErrsCheck.h
--- a/clang-tools-extra/clang-tidy/linuxkernel/MustCheckErrsCheck.h
+++ b/clang-tools-extra/clang-tidy/linuxkernel/MustCheckErrsCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace linuxkernel {
+namespace clang::tidy::linuxkernel {
 
 /// Checks Linux kernel code to see if it uses the results from the functions in
 /// linux/err.h. Also checks to see if code uses the results from functions that
@@ -36,8 +34,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace linuxkernel
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::linuxkernel
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_LINUXKERNEL_MUSTCHECKERRSCHECK_H
diff --git a/clang-tools-extra/clang-tidy/llvm/HeaderGuardCheck.h b/clang-tools-extra/clang-tidy/llvm/HeaderGuardCheck.h
--- a/clang-tools-extra/clang-tidy/llvm/HeaderGuardCheck.h
+++ b/clang-tools-extra/clang-tidy/llvm/HeaderGuardCheck.h
@@ -11,9 +11,7 @@
 
 #include "../utils/HeaderGuard.h"
 
-namespace clang {
-namespace tidy {
-namespace llvm_check {
+namespace clang::tidy::llvm_check {
 
 /// Finds and fixes header guards that do not adhere to LLVM style.
 /// For the user-facing documentation see:
@@ -33,8 +31,6 @@
   std::string getHeaderGuard(StringRef Filename, StringRef OldGuard) override;
 };
 
-} // namespace llvm_check
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::llvm_check
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_LLVM_HEADERGUARDCHECK_H
diff --git a/clang-tools-extra/clang-tidy/llvm/IncludeOrderCheck.h b/clang-tools-extra/clang-tidy/llvm/IncludeOrderCheck.h
--- a/clang-tools-extra/clang-tidy/llvm/IncludeOrderCheck.h
+++ b/clang-tools-extra/clang-tidy/llvm/IncludeOrderCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace llvm_check {
+namespace clang::tidy::llvm_check {
 
 /// Checks the correct order of `#includes`.
 ///
@@ -26,8 +24,6 @@
                            Preprocessor *ModuleExpanderPP) override;
 };
 
-} // namespace llvm_check
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::llvm_check
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_LLVM_INCLUDEORDERCHECK_H
diff --git a/clang-tools-extra/clang-tidy/llvm/PreferIsaOrDynCastInConditionalsCheck.h b/clang-tools-extra/clang-tidy/llvm/PreferIsaOrDynCastInConditionalsCheck.h
--- a/clang-tools-extra/clang-tidy/llvm/PreferIsaOrDynCastInConditionalsCheck.h
+++ b/clang-tools-extra/clang-tidy/llvm/PreferIsaOrDynCastInConditionalsCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace llvm_check {
+namespace clang::tidy::llvm_check {
 
 /// Looks at conditionals and finds and replaces cases of ``cast<>``, which will
 /// assert rather than return a null pointer, and ``dyn_cast<>`` where
@@ -60,8 +58,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace llvm_check
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::llvm_check
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_LLVM_PREFERISAORDYNCASTINCONDITIONALSCHECK_H
diff --git a/clang-tools-extra/clang-tidy/llvm/PreferRegisterOverUnsignedCheck.h b/clang-tools-extra/clang-tidy/llvm/PreferRegisterOverUnsignedCheck.h
--- a/clang-tools-extra/clang-tidy/llvm/PreferRegisterOverUnsignedCheck.h
+++ b/clang-tools-extra/clang-tidy/llvm/PreferRegisterOverUnsignedCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace llvm_check {
+namespace clang::tidy::llvm_check {
 
 /// Historically, LLVM has used `unsigned` to represent registers. Since then
 /// a `Register` object has been introduced for improved type-safety and make
@@ -29,8 +27,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace llvm_check
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::llvm_check
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_LLVM_PREFERREGISTEROVERUNSIGNEDCHECK_H
diff --git a/clang-tools-extra/clang-tidy/llvm/TwineLocalCheck.h b/clang-tools-extra/clang-tidy/llvm/TwineLocalCheck.h
--- a/clang-tools-extra/clang-tidy/llvm/TwineLocalCheck.h
+++ b/clang-tools-extra/clang-tidy/llvm/TwineLocalCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace llvm_check {
+namespace clang::tidy::llvm_check {
 
 /// Looks for local `Twine` variables which are prone to use after frees and
 /// should be generally avoided.
@@ -25,8 +23,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace llvm_check
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::llvm_check
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_LLVM_TWINELOCALCHECK_H
diff --git a/clang-tools-extra/clang-tidy/llvmlibc/CalleeNamespaceCheck.h b/clang-tools-extra/clang-tidy/llvmlibc/CalleeNamespaceCheck.h
--- a/clang-tools-extra/clang-tidy/llvmlibc/CalleeNamespaceCheck.h
+++ b/clang-tools-extra/clang-tidy/llvmlibc/CalleeNamespaceCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace llvm_libc {
+namespace clang::tidy::llvm_libc {
 
 /// Checks all calls resolve to functions within __llvm_libc namespace.
 ///
@@ -31,8 +29,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace llvm_libc
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::llvm_libc
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_LLVMLIBC_CALLEENAMESPACECHECK_H
diff --git a/clang-tools-extra/clang-tidy/llvmlibc/ImplementationInNamespaceCheck.h b/clang-tools-extra/clang-tidy/llvmlibc/ImplementationInNamespaceCheck.h
--- a/clang-tools-extra/clang-tidy/llvmlibc/ImplementationInNamespaceCheck.h
+++ b/clang-tools-extra/clang-tidy/llvmlibc/ImplementationInNamespaceCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace llvm_libc {
+namespace clang::tidy::llvm_libc {
 
 /// Checks all llvm-libc implementation is within the correct namespace.
 ///
@@ -31,8 +29,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace llvm_libc
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::llvm_libc
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_LLVMLIBC_IMPLEMENTATIONINNAMESPACECHECK_H
diff --git a/clang-tools-extra/clang-tidy/llvmlibc/RestrictSystemLibcHeadersCheck.h b/clang-tools-extra/clang-tidy/llvmlibc/RestrictSystemLibcHeadersCheck.h
--- a/clang-tools-extra/clang-tidy/llvmlibc/RestrictSystemLibcHeadersCheck.h
+++ b/clang-tools-extra/clang-tidy/llvmlibc/RestrictSystemLibcHeadersCheck.h
@@ -12,9 +12,7 @@
 #include "../ClangTidyCheck.h"
 #include "../portability/RestrictSystemIncludesCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace llvm_libc {
+namespace clang::tidy::llvm_libc {
 
 /// Warns of accidental inclusions of system libc headers that aren't
 /// compiler provided.
@@ -30,8 +28,6 @@
                            Preprocessor *ModuleExpanderPP) override;
 };
 
-} // namespace llvm_libc
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::llvm_libc
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_LLVMLIBC_RESTRICTSYSTEMLIBCHEADERSCHECK_H
diff --git a/clang-tools-extra/clang-tidy/misc/ConfusableIdentifierCheck.h b/clang-tools-extra/clang-tidy/misc/ConfusableIdentifierCheck.h
--- a/clang-tools-extra/clang-tidy/misc/ConfusableIdentifierCheck.h
+++ b/clang-tools-extra/clang-tidy/misc/ConfusableIdentifierCheck.h
@@ -12,9 +12,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace misc {
+namespace clang::tidy::misc {
 
 /// Finds symbol which have confusable identifiers, i.e. identifiers that look
 /// the same visually but have a different Unicode representation.
@@ -33,8 +31,6 @@
   llvm::StringMap<llvm::SmallVector<const NamedDecl *>> Mapper;
 };
 
-} // namespace misc
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::misc
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MISC_CONFUSABLE_IDENTIFIER_CHECK_H
diff --git a/clang-tools-extra/clang-tidy/misc/ConstCorrectnessCheck.h b/clang-tools-extra/clang-tidy/misc/ConstCorrectnessCheck.h
--- a/clang-tools-extra/clang-tidy/misc/ConstCorrectnessCheck.h
+++ b/clang-tools-extra/clang-tidy/misc/ConstCorrectnessCheck.h
@@ -13,10 +13,7 @@
 #include "clang/Analysis/Analyses/ExprMutationAnalyzer.h"
 #include "llvm/ADT/DenseSet.h"
 
-namespace clang {
-namespace tidy {
-
-namespace misc {
+namespace clang::tidy::misc {
 
 /// This check warns on variables which could be declared const but are not.
 ///
@@ -50,8 +47,6 @@
   const bool TransformPointersAsValues;
 };
 
-} // namespace misc
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::misc
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MISC_CONSTCORRECTNESSCHECK_H
diff --git a/clang-tools-extra/clang-tidy/misc/DefinitionsInHeadersCheck.h b/clang-tools-extra/clang-tidy/misc/DefinitionsInHeadersCheck.h
--- a/clang-tools-extra/clang-tidy/misc/DefinitionsInHeadersCheck.h
+++ b/clang-tools-extra/clang-tidy/misc/DefinitionsInHeadersCheck.h
@@ -12,9 +12,7 @@
 #include "../ClangTidyCheck.h"
 #include "../utils/FileExtensionsUtils.h"
 
-namespace clang {
-namespace tidy {
-namespace misc {
+namespace clang::tidy::misc {
 
 /// Finds non-extern non-inline function and variable definitions in header
 /// files, which can lead to potential ODR violations.
@@ -47,8 +45,6 @@
   utils::FileExtensionsSet HeaderFileExtensions;
 };
 
-} // namespace misc
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::misc
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MISC_DEFINITIONS_IN_HEADERS_H
diff --git a/clang-tools-extra/clang-tidy/misc/MisleadingBidirectional.h b/clang-tools-extra/clang-tidy/misc/MisleadingBidirectional.h
--- a/clang-tools-extra/clang-tidy/misc/MisleadingBidirectional.h
+++ b/clang-tools-extra/clang-tidy/misc/MisleadingBidirectional.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace misc {
+namespace clang::tidy::misc {
 
 class MisleadingBidirectionalCheck : public ClangTidyCheck {
 public:
@@ -31,8 +29,6 @@
   std::unique_ptr<MisleadingBidirectionalHandler> Handler;
 };
 
-} // namespace misc
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::misc
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MISC_MISLEADINGBIDIRECTIONALCHECK_H
diff --git a/clang-tools-extra/clang-tidy/misc/MisleadingIdentifier.h b/clang-tools-extra/clang-tidy/misc/MisleadingIdentifier.h
--- a/clang-tools-extra/clang-tidy/misc/MisleadingIdentifier.h
+++ b/clang-tools-extra/clang-tidy/misc/MisleadingIdentifier.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace misc {
+namespace clang::tidy::misc {
 
 class MisleadingIdentifierCheck : public ClangTidyCheck {
 public:
@@ -24,8 +22,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace misc
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::misc
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MISC_MISLEADINGIDENTIFIERCHECK_H
diff --git a/clang-tools-extra/clang-tidy/misc/MisplacedConstCheck.h b/clang-tools-extra/clang-tidy/misc/MisplacedConstCheck.h
--- a/clang-tools-extra/clang-tidy/misc/MisplacedConstCheck.h
+++ b/clang-tools-extra/clang-tidy/misc/MisplacedConstCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace misc {
+namespace clang::tidy::misc {
 
 /// This check diagnoses when a const qualifier is applied to a typedef to a
 /// pointer type rather than to the pointee.
@@ -28,8 +26,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace misc
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::misc
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MISC_MISPLACED_CONST_H
diff --git a/clang-tools-extra/clang-tidy/misc/NewDeleteOverloadsCheck.h b/clang-tools-extra/clang-tidy/misc/NewDeleteOverloadsCheck.h
--- a/clang-tools-extra/clang-tidy/misc/NewDeleteOverloadsCheck.h
+++ b/clang-tools-extra/clang-tidy/misc/NewDeleteOverloadsCheck.h
@@ -13,9 +13,7 @@
 #include "llvm/ADT/SmallVector.h"
 #include <map>
 
-namespace clang {
-namespace tidy {
-namespace misc {
+namespace clang::tidy::misc {
 
 class NewDeleteOverloadsCheck : public ClangTidyCheck {
   std::map<const clang::CXXRecordDecl *,
@@ -33,8 +31,6 @@
   void onEndOfTranslationUnit() override;
 };
 
-} // namespace misc
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::misc
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MISC_NEWDELETEOVERLOADS_H
diff --git a/clang-tools-extra/clang-tidy/misc/NoRecursionCheck.h b/clang-tools-extra/clang-tidy/misc/NoRecursionCheck.h
--- a/clang-tools-extra/clang-tidy/misc/NoRecursionCheck.h
+++ b/clang-tools-extra/clang-tidy/misc/NoRecursionCheck.h
@@ -15,8 +15,7 @@
 
 class CallGraphNode;
 
-namespace tidy {
-namespace misc {
+namespace tidy::misc {
 
 /// Finds strongly connected functions (by analyzing call graph for SCC's
 /// that are loops), diagnoses each function in the cycle,
@@ -35,8 +34,7 @@
   void handleSCC(ArrayRef<CallGraphNode *> SCC);
 };
 
-} // namespace misc
-} // namespace tidy
+} // namespace tidy::misc
 } // namespace clang
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MISC_NORECURSIONCHECK_H
diff --git a/clang-tools-extra/clang-tidy/misc/NonCopyableObjects.h b/clang-tools-extra/clang-tidy/misc/NonCopyableObjects.h
--- a/clang-tools-extra/clang-tidy/misc/NonCopyableObjects.h
+++ b/clang-tools-extra/clang-tidy/misc/NonCopyableObjects.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace misc {
+namespace clang::tidy::misc {
 
 /// The check flags dereferences and non-pointer declarations of objects that
 /// are not meant to be passed by value, such as C FILE objects.
@@ -25,8 +23,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace misc
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::misc
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MISC_NONCOPYABLEOBJECTS_H
diff --git a/clang-tools-extra/clang-tidy/misc/NonPrivateMemberVariablesInClassesCheck.h b/clang-tools-extra/clang-tidy/misc/NonPrivateMemberVariablesInClassesCheck.h
--- a/clang-tools-extra/clang-tidy/misc/NonPrivateMemberVariablesInClassesCheck.h
+++ b/clang-tools-extra/clang-tidy/misc/NonPrivateMemberVariablesInClassesCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace misc {
+namespace clang::tidy::misc {
 
 /// This checker finds classes that not only contain the data
 /// (non-static member variables), but also have logic (non-static member
@@ -42,8 +40,6 @@
   const bool IgnorePublicMemberVariables;
 };
 
-} // namespace misc
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::misc
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MISC_NONPRIVATEMEMBERVARIABLESINCLASSESCHECK_H
diff --git a/clang-tools-extra/clang-tidy/misc/RedundantExpressionCheck.h b/clang-tools-extra/clang-tidy/misc/RedundantExpressionCheck.h
--- a/clang-tools-extra/clang-tidy/misc/RedundantExpressionCheck.h
+++ b/clang-tools-extra/clang-tidy/misc/RedundantExpressionCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace misc {
+namespace clang::tidy::misc {
 
 /// The checker detects expressions that are redundant, because they contain
 /// ineffective, useless parts.
@@ -33,8 +31,6 @@
   void checkRelationalExpr(const ast_matchers::MatchFinder::MatchResult &R);
 };
 
-} // namespace misc
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::misc
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MISC_REDUNDANT_EXPRESSION_H
diff --git a/clang-tools-extra/clang-tidy/misc/StaticAssertCheck.h b/clang-tools-extra/clang-tidy/misc/StaticAssertCheck.h
--- a/clang-tools-extra/clang-tidy/misc/StaticAssertCheck.h
+++ b/clang-tools-extra/clang-tidy/misc/StaticAssertCheck.h
@@ -13,9 +13,7 @@
 #include "llvm/ADT/StringRef.h"
 #include <string>
 
-namespace clang {
-namespace tidy {
-namespace misc {
+namespace clang::tidy::misc {
 
 /// Replaces `assert()` with `static_assert()` if the condition is evaluatable
 /// at compile time.
@@ -36,8 +34,6 @@
                                  SourceLocation AssertLoc);
 };
 
-} // namespace misc
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::misc
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MISC_STATICASSERTCHECK_H
diff --git a/clang-tools-extra/clang-tidy/misc/ThrowByValueCatchByReferenceCheck.h b/clang-tools-extra/clang-tidy/misc/ThrowByValueCatchByReferenceCheck.h
--- a/clang-tools-extra/clang-tidy/misc/ThrowByValueCatchByReferenceCheck.h
+++ b/clang-tools-extra/clang-tidy/misc/ThrowByValueCatchByReferenceCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace misc {
+namespace clang::tidy::misc {
 
 ///checks for locations that do not throw by value
 // or catch by reference.
@@ -49,8 +47,6 @@
   uint64_t MaxSize; // No `const` because we have to set it in two steps.
 };
 
-} // namespace misc
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::misc
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MISC_THROW_BY_VALUE_CATCH_BY_REFERENCE_H
diff --git a/clang-tools-extra/clang-tidy/misc/UnconventionalAssignOperatorCheck.h b/clang-tools-extra/clang-tidy/misc/UnconventionalAssignOperatorCheck.h
--- a/clang-tools-extra/clang-tidy/misc/UnconventionalAssignOperatorCheck.h
+++ b/clang-tools-extra/clang-tidy/misc/UnconventionalAssignOperatorCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace misc {
+namespace clang::tidy::misc {
 
 /// Finds declarations of assignment operators with the wrong return and/or
 /// argument types and definitions with good return type but wrong return
@@ -37,8 +35,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace misc
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::misc
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MISC_ASSIGNOPERATORSIGNATURECHECK_H
diff --git a/clang-tools-extra/clang-tidy/misc/UniqueptrResetReleaseCheck.h b/clang-tools-extra/clang-tidy/misc/UniqueptrResetReleaseCheck.h
--- a/clang-tools-extra/clang-tidy/misc/UniqueptrResetReleaseCheck.h
+++ b/clang-tools-extra/clang-tidy/misc/UniqueptrResetReleaseCheck.h
@@ -12,9 +12,7 @@
 #include "../ClangTidyCheck.h"
 #include "../utils/IncludeInserter.h"
 
-namespace clang {
-namespace tidy {
-namespace misc {
+namespace clang::tidy::misc {
 
 /// Find and replace `unique_ptr::reset(release())` with `std::move()`.
 ///
@@ -47,8 +45,6 @@
   utils::IncludeInserter Inserter;
 };
 
-} // namespace misc
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::misc
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MISC_UNIQUEPTRRESETRELEASECHECK_H
diff --git a/clang-tools-extra/clang-tidy/misc/UnusedAliasDeclsCheck.h b/clang-tools-extra/clang-tidy/misc/UnusedAliasDeclsCheck.h
--- a/clang-tools-extra/clang-tidy/misc/UnusedAliasDeclsCheck.h
+++ b/clang-tools-extra/clang-tidy/misc/UnusedAliasDeclsCheck.h
@@ -12,9 +12,7 @@
 #include "../ClangTidyCheck.h"
 #include "llvm/ADT/DenseMap.h"
 
-namespace clang {
-namespace tidy {
-namespace misc {
+namespace clang::tidy::misc {
 
 /// Finds unused namespace alias declarations.
 class UnusedAliasDeclsCheck : public ClangTidyCheck {
@@ -32,8 +30,6 @@
   llvm::DenseMap<const NamedDecl *, CharSourceRange> FoundDecls;
 };
 
-} // namespace misc
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::misc
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MISC_UNUSED_ALIAS_DECLS_H
diff --git a/clang-tools-extra/clang-tidy/misc/UnusedParametersCheck.h b/clang-tools-extra/clang-tidy/misc/UnusedParametersCheck.h
--- a/clang-tools-extra/clang-tidy/misc/UnusedParametersCheck.h
+++ b/clang-tools-extra/clang-tidy/misc/UnusedParametersCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace misc {
+namespace clang::tidy::misc {
 
 /// Finds unused parameters and fixes them, so that `-Wunused-parameter` can be
 /// turned on.
@@ -35,8 +33,6 @@
                         const FunctionDecl *Function, unsigned ParamIndex);
 };
 
-} // namespace misc
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::misc
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MISC_UNUSED_PARAMETERS_H
diff --git a/clang-tools-extra/clang-tidy/misc/UnusedUsingDeclsCheck.h b/clang-tools-extra/clang-tidy/misc/UnusedUsingDeclsCheck.h
--- a/clang-tools-extra/clang-tidy/misc/UnusedUsingDeclsCheck.h
+++ b/clang-tools-extra/clang-tidy/misc/UnusedUsingDeclsCheck.h
@@ -14,9 +14,7 @@
 #include "llvm/ADT/SmallPtrSet.h"
 #include <vector>
 
-namespace clang {
-namespace tidy {
-namespace misc {
+namespace clang::tidy::misc {
 
 /// Finds unused using declarations.
 ///
@@ -53,8 +51,6 @@
   utils::FileExtensionsSet HeaderFileExtensions;
 };
 
-} // namespace misc
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::misc
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MISC_UNUSED_USING_DECLS_H
diff --git a/clang-tools-extra/clang-tidy/misc/UseAnonymousNamespaceCheck.h b/clang-tools-extra/clang-tidy/misc/UseAnonymousNamespaceCheck.h
--- a/clang-tools-extra/clang-tidy/misc/UseAnonymousNamespaceCheck.h
+++ b/clang-tools-extra/clang-tidy/misc/UseAnonymousNamespaceCheck.h
@@ -12,9 +12,7 @@
 #include "../ClangTidyCheck.h"
 #include "../utils/FileExtensionsUtils.h"
 
-namespace clang {
-namespace tidy {
-namespace misc {
+namespace clang::tidy::misc {
 
 /// Warns when using 'static' functions or variables at global scope, and
 /// suggests moving them to an anonymous namespace.
@@ -44,8 +42,6 @@
   utils::FileExtensionsSet HeaderFileExtensions;
 };
 
-} // namespace misc
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::misc
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MISC_USEANONYMOUSNAMESPACECHECK_H
diff --git a/clang-tools-extra/clang-tidy/modernize/AvoidBindCheck.h b/clang-tools-extra/clang-tidy/modernize/AvoidBindCheck.h
--- a/clang-tools-extra/clang-tidy/modernize/AvoidBindCheck.h
+++ b/clang-tools-extra/clang-tidy/modernize/AvoidBindCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 /// Replace simple uses of std::bind with a lambda.
 ///
@@ -34,8 +32,6 @@
 private:
   bool PermissiveParameterList = false;
 };
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_AVOID_BIND_H
diff --git a/clang-tools-extra/clang-tidy/modernize/AvoidCArraysCheck.h b/clang-tools-extra/clang-tidy/modernize/AvoidCArraysCheck.h
--- a/clang-tools-extra/clang-tidy/modernize/AvoidCArraysCheck.h
+++ b/clang-tools-extra/clang-tidy/modernize/AvoidCArraysCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 /// Find C-style array types and recommend to use std::array<> / std::vector<>.
 ///
@@ -30,8 +28,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_AVOIDCARRAYSCHECK_H
diff --git a/clang-tools-extra/clang-tidy/modernize/ConcatNestedNamespacesCheck.h b/clang-tools-extra/clang-tidy/modernize/ConcatNestedNamespacesCheck.h
--- a/clang-tools-extra/clang-tidy/modernize/ConcatNestedNamespacesCheck.h
+++ b/clang-tools-extra/clang-tidy/modernize/ConcatNestedNamespacesCheck.h
@@ -13,9 +13,7 @@
 #include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/SmallVector.h"
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 class ConcatNestedNamespacesCheck : public ClangTidyCheck {
 public:
@@ -36,8 +34,6 @@
   NamespaceString concatNamespaces();
   NamespaceContextVec Namespaces;
 };
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_CONCATNESTEDNAMESPACESCHECK_H
diff --git a/clang-tools-extra/clang-tidy/modernize/DeprecatedHeadersCheck.h b/clang-tools-extra/clang-tidy/modernize/DeprecatedHeadersCheck.h
--- a/clang-tools-extra/clang-tidy/modernize/DeprecatedHeadersCheck.h
+++ b/clang-tools-extra/clang-tidy/modernize/DeprecatedHeadersCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 /// This check replaces deprecated C library headers with their C++ STL
 /// alternatives.
@@ -57,8 +55,6 @@
   bool CheckHeaderFile;
 };
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_C_HEADERS_TO_CXX_H
diff --git a/clang-tools-extra/clang-tidy/modernize/DeprecatedIosBaseAliasesCheck.h b/clang-tools-extra/clang-tidy/modernize/DeprecatedIosBaseAliasesCheck.h
--- a/clang-tools-extra/clang-tidy/modernize/DeprecatedIosBaseAliasesCheck.h
+++ b/clang-tools-extra/clang-tidy/modernize/DeprecatedIosBaseAliasesCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 /// This check warns the uses of the deprecated member types of ``std::ios_base``
 /// and replaces those that have a non-deprecated equivalent.
@@ -31,8 +29,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_DEPRECATEDIOSBASEALIASESCHECK_H
diff --git a/clang-tools-extra/clang-tidy/modernize/IntegralLiteralExpressionMatcher.h b/clang-tools-extra/clang-tidy/modernize/IntegralLiteralExpressionMatcher.h
--- a/clang-tools-extra/clang-tidy/modernize/IntegralLiteralExpressionMatcher.h
+++ b/clang-tools-extra/clang-tidy/modernize/IntegralLiteralExpressionMatcher.h
@@ -12,9 +12,7 @@
 #include <clang/Lex/Token.h>
 #include <llvm/ADT/ArrayRef.h>
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 enum class LiteralSize {
   Unknown = 0,
@@ -80,8 +78,6 @@
   bool CommaAllowed;
 };
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
 
 #endif
diff --git a/clang-tools-extra/clang-tidy/modernize/LoopConvertCheck.h b/clang-tools-extra/clang-tidy/modernize/LoopConvertCheck.h
--- a/clang-tools-extra/clang-tidy/modernize/LoopConvertCheck.h
+++ b/clang-tools-extra/clang-tidy/modernize/LoopConvertCheck.h
@@ -13,9 +13,7 @@
 #include "../utils/IncludeInserter.h"
 #include "LoopConvertUtils.h"
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 class LoopConvertCheck : public ClangTidyCheck {
 public:
@@ -85,8 +83,6 @@
   std::string ReverseHeader;
 };
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_LOOP_CONVERT_H
diff --git a/clang-tools-extra/clang-tidy/modernize/LoopConvertUtils.h b/clang-tools-extra/clang-tidy/modernize/LoopConvertUtils.h
--- a/clang-tools-extra/clang-tidy/modernize/LoopConvertUtils.h
+++ b/clang-tools-extra/clang-tidy/modernize/LoopConvertUtils.h
@@ -22,9 +22,7 @@
 #include <string>
 #include <utility>
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 enum LoopFixerKind {
   LFK_Array,
@@ -464,8 +462,6 @@
   bool declarationExists(llvm::StringRef Symbol);
 };
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_LOOP_CONVERT_UTILS_H
diff --git a/clang-tools-extra/clang-tidy/modernize/MacroToEnumCheck.h b/clang-tools-extra/clang-tidy/modernize/MacroToEnumCheck.h
--- a/clang-tools-extra/clang-tidy/modernize/MacroToEnumCheck.h
+++ b/clang-tools-extra/clang-tidy/modernize/MacroToEnumCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 class MacroToEnumCallbacks;
 
@@ -34,8 +32,6 @@
   MacroToEnumCallbacks *PPCallback{};
 };
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_MACROTOENUMCHECK_H
diff --git a/clang-tools-extra/clang-tidy/modernize/MakeSharedCheck.h b/clang-tools-extra/clang-tidy/modernize/MakeSharedCheck.h
--- a/clang-tools-extra/clang-tidy/modernize/MakeSharedCheck.h
+++ b/clang-tools-extra/clang-tidy/modernize/MakeSharedCheck.h
@@ -11,9 +11,7 @@
 
 #include "MakeSmartPtrCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 /// Replace the pattern:
 /// \code
@@ -35,8 +33,6 @@
   SmartPtrTypeMatcher getSmartPointerTypeMatcher() const override;
 };
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_MAKE_SHARED_H
diff --git a/clang-tools-extra/clang-tidy/modernize/MakeSmartPtrCheck.h b/clang-tools-extra/clang-tidy/modernize/MakeSmartPtrCheck.h
--- a/clang-tools-extra/clang-tidy/modernize/MakeSmartPtrCheck.h
+++ b/clang-tools-extra/clang-tidy/modernize/MakeSmartPtrCheck.h
@@ -16,9 +16,7 @@
 #include "llvm/ADT/StringRef.h"
 #include <string>
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 /// Base class for MakeSharedCheck and MakeUniqueCheck.
 class MakeSmartPtrCheck : public ClangTidyCheck {
@@ -64,8 +62,6 @@
   void insertHeader(DiagnosticBuilder &Diag, FileID FD);
 };
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_MAKE_SMART_PTR_H
diff --git a/clang-tools-extra/clang-tidy/modernize/MakeUniqueCheck.h b/clang-tools-extra/clang-tidy/modernize/MakeUniqueCheck.h
--- a/clang-tools-extra/clang-tidy/modernize/MakeUniqueCheck.h
+++ b/clang-tools-extra/clang-tidy/modernize/MakeUniqueCheck.h
@@ -11,9 +11,7 @@
 
 #include "MakeSmartPtrCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 /// Replace the pattern:
 /// \code
@@ -37,8 +35,6 @@
   const bool RequireCPlusPlus14;
 };
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_MAKE_UNIQUE_H
diff --git a/clang-tools-extra/clang-tidy/modernize/PassByValueCheck.h b/clang-tools-extra/clang-tidy/modernize/PassByValueCheck.h
--- a/clang-tools-extra/clang-tidy/modernize/PassByValueCheck.h
+++ b/clang-tools-extra/clang-tidy/modernize/PassByValueCheck.h
@@ -14,9 +14,7 @@
 
 #include <memory>
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 class PassByValueCheck : public ClangTidyCheck {
 public:
@@ -35,8 +33,6 @@
   const bool ValuesOnly;
 };
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_PASS_BY_VALUE_H
diff --git a/clang-tools-extra/clang-tidy/modernize/RawStringLiteralCheck.h b/clang-tools-extra/clang-tidy/modernize/RawStringLiteralCheck.h
--- a/clang-tools-extra/clang-tidy/modernize/RawStringLiteralCheck.h
+++ b/clang-tools-extra/clang-tidy/modernize/RawStringLiteralCheck.h
@@ -12,9 +12,7 @@
 #include "../ClangTidyCheck.h"
 #include <bitset>
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 using CharsBitSet = std::bitset<1 << CHAR_BIT>;
 
@@ -44,8 +42,6 @@
   const bool ReplaceShorterLiterals;
 };
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_RAW_STRING_LITERAL_H
diff --git a/clang-tools-extra/clang-tidy/modernize/RedundantVoidArgCheck.h b/clang-tools-extra/clang-tidy/modernize/RedundantVoidArgCheck.h
--- a/clang-tools-extra/clang-tidy/modernize/RedundantVoidArgCheck.h
+++ b/clang-tools-extra/clang-tidy/modernize/RedundantVoidArgCheck.h
@@ -14,9 +14,7 @@
 
 #include <string>
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 /// Find and remove redundant void argument lists.
 ///
@@ -73,8 +71,6 @@
   void removeVoidToken(Token VoidToken, StringRef Diagnostic);
 };
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_REDUNDANT_VOID_ARG_CHECK_H
diff --git a/clang-tools-extra/clang-tidy/modernize/ReplaceAutoPtrCheck.h b/clang-tools-extra/clang-tidy/modernize/ReplaceAutoPtrCheck.h
--- a/clang-tools-extra/clang-tidy/modernize/ReplaceAutoPtrCheck.h
+++ b/clang-tools-extra/clang-tidy/modernize/ReplaceAutoPtrCheck.h
@@ -12,9 +12,7 @@
 #include "../ClangTidyCheck.h"
 #include "../utils/IncludeInserter.h"
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 /// Transforms the deprecated `std::auto_ptr` into the C++11 `std::unique_ptr`.
 ///
@@ -56,8 +54,6 @@
   utils::IncludeInserter Inserter;
 };
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_REPLACE_AUTO_PTR_H
diff --git a/clang-tools-extra/clang-tidy/modernize/ReplaceDisallowCopyAndAssignMacroCheck.h b/clang-tools-extra/clang-tidy/modernize/ReplaceDisallowCopyAndAssignMacroCheck.h
--- a/clang-tools-extra/clang-tidy/modernize/ReplaceDisallowCopyAndAssignMacroCheck.h
+++ b/clang-tools-extra/clang-tidy/modernize/ReplaceDisallowCopyAndAssignMacroCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 /// This check finds macro expansions of ``DISALLOW_COPY_AND_ASSIGN(Type)`` and
 /// replaces them with a deleted copy constructor and a deleted assignment
@@ -55,8 +53,6 @@
   const StringRef MacroName;
 };
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_REPLACEDISALLOWCOPYANDASSIGNMACROCHECK_H
diff --git a/clang-tools-extra/clang-tidy/modernize/ReplaceRandomShuffleCheck.h b/clang-tools-extra/clang-tidy/modernize/ReplaceRandomShuffleCheck.h
--- a/clang-tools-extra/clang-tidy/modernize/ReplaceRandomShuffleCheck.h
+++ b/clang-tools-extra/clang-tidy/modernize/ReplaceRandomShuffleCheck.h
@@ -12,9 +12,7 @@
 #include "../ClangTidyCheck.h"
 #include "../utils/IncludeInserter.h"
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 /// std::random_shuffle will be removed as of C++17. This check will find and
 /// replace all occurrences of std::random_shuffle with std::shuffle.
@@ -37,8 +35,6 @@
   utils::IncludeInserter IncludeInserter;
 };
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_REPLACE_RANDOM_SHUFFLE_H
diff --git a/clang-tools-extra/clang-tidy/modernize/ReturnBracedInitListCheck.h b/clang-tools-extra/clang-tidy/modernize/ReturnBracedInitListCheck.h
--- a/clang-tools-extra/clang-tidy/modernize/ReturnBracedInitListCheck.h
+++ b/clang-tools-extra/clang-tidy/modernize/ReturnBracedInitListCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 /// Use a braced init list for return statements rather than unnecessary
 /// repeating the return type name.
@@ -34,8 +32,6 @@
   }
 };
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_RETURN_BRACED_INIT_LIST_H
diff --git a/clang-tools-extra/clang-tidy/modernize/ShrinkToFitCheck.h b/clang-tools-extra/clang-tidy/modernize/ShrinkToFitCheck.h
--- a/clang-tools-extra/clang-tidy/modernize/ShrinkToFitCheck.h
+++ b/clang-tools-extra/clang-tidy/modernize/ShrinkToFitCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 /// Replace copy and swap tricks on shrinkable containers with the
 /// `shrink_to_fit()` method call.
@@ -35,8 +33,6 @@
   }
 };
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_SHRINKTOFITCHECK_H
diff --git a/clang-tools-extra/clang-tidy/modernize/UnaryStaticAssertCheck.h b/clang-tools-extra/clang-tidy/modernize/UnaryStaticAssertCheck.h
--- a/clang-tools-extra/clang-tidy/modernize/UnaryStaticAssertCheck.h
+++ b/clang-tools-extra/clang-tidy/modernize/UnaryStaticAssertCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 /// Replaces a static_assert declaration with an empty message
 /// with the unary version.
@@ -31,8 +29,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_UNARY_STATIC_ASSERT_H
diff --git a/clang-tools-extra/clang-tidy/modernize/UseAutoCheck.h b/clang-tools-extra/clang-tidy/modernize/UseAutoCheck.h
--- a/clang-tools-extra/clang-tidy/modernize/UseAutoCheck.h
+++ b/clang-tools-extra/clang-tidy/modernize/UseAutoCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 class UseAutoCheck : public ClangTidyCheck {
 public:
@@ -35,8 +33,6 @@
   const bool RemoveStars;
 };
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_USE_AUTO_H
diff --git a/clang-tools-extra/clang-tidy/modernize/UseBoolLiteralsCheck.h b/clang-tools-extra/clang-tidy/modernize/UseBoolLiteralsCheck.h
--- a/clang-tools-extra/clang-tidy/modernize/UseBoolLiteralsCheck.h
+++ b/clang-tools-extra/clang-tidy/modernize/UseBoolLiteralsCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 /// Finds integer literals which are cast to bool.
 ///
@@ -33,8 +31,6 @@
   const bool IgnoreMacros;
 };
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_USE_BOOL_LITERALS_H
diff --git a/clang-tools-extra/clang-tidy/modernize/UseDefaultMemberInitCheck.h b/clang-tools-extra/clang-tidy/modernize/UseDefaultMemberInitCheck.h
--- a/clang-tools-extra/clang-tidy/modernize/UseDefaultMemberInitCheck.h
+++ b/clang-tools-extra/clang-tidy/modernize/UseDefaultMemberInitCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 /// Convert a default constructor's member initializers into default member
 /// initializers.  Remove member initializers that are the same as a default
@@ -44,8 +42,6 @@
   const bool IgnoreMacros;
 };
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_USE_DEFAULT_MEMBER_INIT_H
diff --git a/clang-tools-extra/clang-tidy/modernize/UseEmplaceCheck.h b/clang-tools-extra/clang-tidy/modernize/UseEmplaceCheck.h
--- a/clang-tools-extra/clang-tidy/modernize/UseEmplaceCheck.h
+++ b/clang-tools-extra/clang-tidy/modernize/UseEmplaceCheck.h
@@ -13,9 +13,7 @@
 #include <string>
 #include <vector>
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 /// This check looks for cases when inserting new element into std::vector but
 /// the element is constructed temporarily.
@@ -45,8 +43,6 @@
   const std::vector<StringRef> EmplacyFunctions;
 };
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_USE_EMPLACE_H
diff --git a/clang-tools-extra/clang-tidy/modernize/UseEqualsDefaultCheck.h b/clang-tools-extra/clang-tidy/modernize/UseEqualsDefaultCheck.h
--- a/clang-tools-extra/clang-tidy/modernize/UseEqualsDefaultCheck.h
+++ b/clang-tools-extra/clang-tidy/modernize/UseEqualsDefaultCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 /// Replace default bodies of special member functions with '= default;'.
 /// \code
@@ -48,8 +46,6 @@
   const bool IgnoreMacros;
 };
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_USE_EQUALS_DEFAULT_H
diff --git a/clang-tools-extra/clang-tidy/modernize/UseEqualsDeleteCheck.h b/clang-tools-extra/clang-tidy/modernize/UseEqualsDeleteCheck.h
--- a/clang-tools-extra/clang-tidy/modernize/UseEqualsDeleteCheck.h
+++ b/clang-tools-extra/clang-tidy/modernize/UseEqualsDeleteCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 /// Mark unimplemented private special member functions with '= delete'.
 /// \code
@@ -50,8 +48,6 @@
   const bool IgnoreMacros;
 };
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_USE_EQUALS_DELETE_H
diff --git a/clang-tools-extra/clang-tidy/modernize/UseNodiscardCheck.h b/clang-tools-extra/clang-tidy/modernize/UseNodiscardCheck.h
--- a/clang-tools-extra/clang-tidy/modernize/UseNodiscardCheck.h
+++ b/clang-tools-extra/clang-tidy/modernize/UseNodiscardCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 /// Add ``[[nodiscard]]`` to non-void const-member functions with no
 /// arguments or pass-by-value or pass by const-reference arguments.
@@ -43,8 +41,6 @@
   const StringRef NoDiscardMacro;
 };
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_USENODISCARDCHECK_H
diff --git a/clang-tools-extra/clang-tidy/modernize/UseNoexceptCheck.h b/clang-tools-extra/clang-tidy/modernize/UseNoexceptCheck.h
--- a/clang-tools-extra/clang-tidy/modernize/UseNoexceptCheck.h
+++ b/clang-tools-extra/clang-tidy/modernize/UseNoexceptCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 /// Replace dynamic exception specifications, with
 /// `noexcept` (or user-defined macro) or `noexcept(false)`.
@@ -44,8 +42,6 @@
   const bool UseNoexceptFalse;
 };
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_USE_NOEXCEPT_H
diff --git a/clang-tools-extra/clang-tidy/modernize/UseNullptrCheck.h b/clang-tools-extra/clang-tidy/modernize/UseNullptrCheck.h
--- a/clang-tools-extra/clang-tidy/modernize/UseNullptrCheck.h
+++ b/clang-tools-extra/clang-tidy/modernize/UseNullptrCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 class UseNullptrCheck : public ClangTidyCheck {
 public:
@@ -32,8 +30,6 @@
   SmallVector<StringRef, 1> NullMacros;
 };
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_USE_NULLPTR_H
diff --git a/clang-tools-extra/clang-tidy/modernize/UseOverrideCheck.h b/clang-tools-extra/clang-tidy/modernize/UseOverrideCheck.h
--- a/clang-tools-extra/clang-tidy/modernize/UseOverrideCheck.h
+++ b/clang-tools-extra/clang-tidy/modernize/UseOverrideCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 /// Use C++11's `override` and remove `virtual` where applicable.
 class UseOverrideCheck : public ClangTidyCheck {
@@ -34,8 +32,6 @@
   const StringRef FinalSpelling;
 };
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_USEOVERRIDECHECK_H
diff --git a/clang-tools-extra/clang-tidy/modernize/UseTrailingReturnTypeCheck.h b/clang-tools-extra/clang-tidy/modernize/UseTrailingReturnTypeCheck.h
--- a/clang-tools-extra/clang-tidy/modernize/UseTrailingReturnTypeCheck.h
+++ b/clang-tools-extra/clang-tidy/modernize/UseTrailingReturnTypeCheck.h
@@ -13,9 +13,7 @@
 #include "clang/Lex/Token.h"
 #include <optional>
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 struct ClassifiedToken {
   Token T;
@@ -60,8 +58,6 @@
                       const SourceManager &SM, const LangOptions &LangOpts);
 };
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_USETRAILINGRETURNTYPECHECK_H
diff --git a/clang-tools-extra/clang-tidy/modernize/UseTransparentFunctorsCheck.h b/clang-tools-extra/clang-tidy/modernize/UseTransparentFunctorsCheck.h
--- a/clang-tools-extra/clang-tidy/modernize/UseTransparentFunctorsCheck.h
+++ b/clang-tools-extra/clang-tidy/modernize/UseTransparentFunctorsCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 /// Prefer using transparent functors to non-transparent ones.
 ///
@@ -32,8 +30,6 @@
   const bool SafeMode;
 };
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_USE_TRANSPARENT_FUNCTORS_H
diff --git a/clang-tools-extra/clang-tidy/modernize/UseUncaughtExceptionsCheck.h b/clang-tools-extra/clang-tidy/modernize/UseUncaughtExceptionsCheck.h
--- a/clang-tools-extra/clang-tidy/modernize/UseUncaughtExceptionsCheck.h
+++ b/clang-tools-extra/clang-tidy/modernize/UseUncaughtExceptionsCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 /// This check will warn on calls to std::uncaught_exception and replace them with calls to
 /// std::uncaught_exceptions, since std::uncaught_exception was deprecated in C++17. In case of
@@ -32,8 +30,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_USE_UNCAUGHT_EXCEPTIONS_H
diff --git a/clang-tools-extra/clang-tidy/modernize/UseUsingCheck.h b/clang-tools-extra/clang-tidy/modernize/UseUsingCheck.h
--- a/clang-tools-extra/clang-tidy/modernize/UseUsingCheck.h
+++ b/clang-tools-extra/clang-tidy/modernize/UseUsingCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 /// Check finds typedefs and replaces it with usings.
 ///
@@ -38,8 +36,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_USE_USING_H
diff --git a/clang-tools-extra/clang-tidy/mpi/BufferDerefCheck.h b/clang-tools-extra/clang-tidy/mpi/BufferDerefCheck.h
--- a/clang-tools-extra/clang-tidy/mpi/BufferDerefCheck.h
+++ b/clang-tools-extra/clang-tidy/mpi/BufferDerefCheck.h
@@ -13,9 +13,7 @@
 #include "clang/StaticAnalyzer/Checkers/MPIFunctionClassifier.h"
 #include <optional>
 
-namespace clang {
-namespace tidy {
-namespace mpi {
+namespace clang::tidy::mpi {
 
 /// This check verifies if a buffer passed to an MPI (Message Passing Interface)
 /// function is sufficiently dereferenced. Buffers should be passed as a single
@@ -48,8 +46,6 @@
   std::optional<ento::mpi::MPIFunctionClassifier> FuncClassifier;
 };
 
-} // namespace mpi
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::mpi
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MPI_BUFFER_DEREF_H
diff --git a/clang-tools-extra/clang-tidy/mpi/TypeMismatchCheck.h b/clang-tools-extra/clang-tidy/mpi/TypeMismatchCheck.h
--- a/clang-tools-extra/clang-tidy/mpi/TypeMismatchCheck.h
+++ b/clang-tools-extra/clang-tidy/mpi/TypeMismatchCheck.h
@@ -14,9 +14,7 @@
 #include "clang/StaticAnalyzer/Checkers/MPIFunctionClassifier.h"
 #include <optional>
 
-namespace clang {
-namespace tidy {
-namespace mpi {
+namespace clang::tidy::mpi {
 
 /// This check verifies if buffer type and MPI (Message Passing Interface)
 /// datatype pairs match. All MPI datatypes defined by the MPI standard (3.1)
@@ -49,8 +47,6 @@
   std::optional<ento::mpi::MPIFunctionClassifier> FuncClassifier;
 };
 
-} // namespace mpi
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::mpi
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MPI_TYPE_MISMATCH_H
diff --git a/clang-tools-extra/clang-tidy/objc/AssertEquals.h b/clang-tools-extra/clang-tidy/objc/AssertEquals.h
--- a/clang-tools-extra/clang-tidy/objc/AssertEquals.h
+++ b/clang-tools-extra/clang-tidy/objc/AssertEquals.h
@@ -12,9 +12,7 @@
 #include "../ClangTidyCheck.h"
 #include "clang/ASTMatchers/ASTMatchFinder.h"
 
-namespace clang {
-namespace tidy {
-namespace objc {
+namespace clang::tidy::objc {
 
 /// Warn if XCTAssertEqual() or XCTAssertNotEqual() is used with at least one
 /// operands of type NSString*.
@@ -32,8 +30,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace objc
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::objc
 
 #endif // THIRD_PARTY_LLVM_LLVM_PROJECT_CLANG_TOOLS_EXTRA_CLANG_TIDY_OBJC_OBJCASSERTEQUALS_H_
diff --git a/clang-tools-extra/clang-tidy/objc/AvoidNSErrorInitCheck.h b/clang-tools-extra/clang-tidy/objc/AvoidNSErrorInitCheck.h
--- a/clang-tools-extra/clang-tidy/objc/AvoidNSErrorInitCheck.h
+++ b/clang-tools-extra/clang-tidy/objc/AvoidNSErrorInitCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace objc {
+namespace clang::tidy::objc {
 
 /// Finds usages of -[NSError init]. It is not the proper way of creating
 /// NSError. errorWithDomain:code:userInfo: should be used instead.
@@ -31,8 +29,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-}  // namespace objc
-}  // namespace tidy
-}  // namespace clang
+} // namespace clang::tidy::objc
 
 #endif  // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_OBJC_AVOIDNSERRORINITCHECK_H
diff --git a/clang-tools-extra/clang-tidy/objc/DeallocInCategoryCheck.h b/clang-tools-extra/clang-tidy/objc/DeallocInCategoryCheck.h
--- a/clang-tools-extra/clang-tidy/objc/DeallocInCategoryCheck.h
+++ b/clang-tools-extra/clang-tidy/objc/DeallocInCategoryCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace objc {
+namespace clang::tidy::objc {
 
 /// Finds implementations of -dealloc in Objective-C categories. The category
 /// implementation will override any dealloc in the class implementation,
@@ -32,8 +30,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace objc
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::objc
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_OBJC_DEALLOCINCATEGORYCHECK_H
diff --git a/clang-tools-extra/clang-tidy/objc/ForbiddenSubclassingCheck.h b/clang-tools-extra/clang-tidy/objc/ForbiddenSubclassingCheck.h
--- a/clang-tools-extra/clang-tidy/objc/ForbiddenSubclassingCheck.h
+++ b/clang-tools-extra/clang-tidy/objc/ForbiddenSubclassingCheck.h
@@ -13,9 +13,7 @@
 #include "llvm/ADT/StringRef.h"
 #include <vector>
 
-namespace clang {
-namespace tidy {
-namespace objc {
+namespace clang::tidy::objc {
 
 /// Finds Objective-C classes which have a superclass which is
 /// documented to not support subclassing.
@@ -36,8 +34,6 @@
   const std::vector<StringRef> ForbiddenSuperClassNames;
 };
 
-} // namespace objc
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::objc
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_OBJC_FORBIDDEN_SUBCLASSING_CHECK_H
diff --git a/clang-tools-extra/clang-tidy/objc/MissingHashCheck.h b/clang-tools-extra/clang-tidy/objc/MissingHashCheck.h
--- a/clang-tools-extra/clang-tidy/objc/MissingHashCheck.h
+++ b/clang-tools-extra/clang-tidy/objc/MissingHashCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace objc {
+namespace clang::tidy::objc {
 
 /// Finds Objective-C implementations that implement -isEqual: without also
 /// appropriately implementing -hash.
@@ -31,8 +29,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace objc
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::objc
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_OBJC_MISSINGHASHCHECK_H
diff --git a/clang-tools-extra/clang-tidy/objc/NSDateFormatterCheck.h b/clang-tools-extra/clang-tidy/objc/NSDateFormatterCheck.h
--- a/clang-tools-extra/clang-tidy/objc/NSDateFormatterCheck.h
+++ b/clang-tools-extra/clang-tidy/objc/NSDateFormatterCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace objc {
+namespace clang::tidy::objc {
 
 /// Checks the string pattern used as a date format specifier and reports
 /// warnings if it contains any incorrect sub-pattern.
@@ -31,8 +29,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace objc
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::objc
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_OBJC_NSDATEFORMATTERCHECK_H
diff --git a/clang-tools-extra/clang-tidy/objc/NSInvocationArgumentLifetimeCheck.h b/clang-tools-extra/clang-tidy/objc/NSInvocationArgumentLifetimeCheck.h
--- a/clang-tools-extra/clang-tidy/objc/NSInvocationArgumentLifetimeCheck.h
+++ b/clang-tools-extra/clang-tidy/objc/NSInvocationArgumentLifetimeCheck.h
@@ -12,9 +12,7 @@
 #include "../ClangTidyCheck.h"
 #include "clang/Basic/LangStandard.h"
 
-namespace clang {
-namespace tidy {
-namespace objc {
+namespace clang::tidy::objc {
 
 /// Finds calls to NSInvocation methods under ARC that don't have proper
 /// argument object lifetimes.
@@ -32,8 +30,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace objc
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::objc
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_OBJC_NSINVOCATIONARGUMENTLIFETIMECHECK_H
diff --git a/clang-tools-extra/clang-tidy/objc/PropertyDeclarationCheck.h b/clang-tools-extra/clang-tidy/objc/PropertyDeclarationCheck.h
--- a/clang-tools-extra/clang-tidy/objc/PropertyDeclarationCheck.h
+++ b/clang-tools-extra/clang-tidy/objc/PropertyDeclarationCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace objc {
+namespace clang::tidy::objc {
 
 /// Finds Objective-C property declarations which
 /// are not in Lower Camel Case.
@@ -34,8 +32,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace objc
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::objc
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_OBJC_PROPERTY_DECLARATION_H
diff --git a/clang-tools-extra/clang-tidy/objc/SuperSelfCheck.h b/clang-tools-extra/clang-tidy/objc/SuperSelfCheck.h
--- a/clang-tools-extra/clang-tidy/objc/SuperSelfCheck.h
+++ b/clang-tools-extra/clang-tidy/objc/SuperSelfCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace objc {
+namespace clang::tidy::objc {
 
 /// Finds invocations of -self on super instances in initializers of subclasses
 /// of NSObject and recommends calling a superclass initializer instead.
@@ -31,8 +29,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace objc
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::objc
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_OBJC_SUPERSELFCHECK_H
diff --git a/clang-tools-extra/clang-tidy/openmp/ExceptionEscapeCheck.h b/clang-tools-extra/clang-tidy/openmp/ExceptionEscapeCheck.h
--- a/clang-tools-extra/clang-tidy/openmp/ExceptionEscapeCheck.h
+++ b/clang-tools-extra/clang-tidy/openmp/ExceptionEscapeCheck.h
@@ -12,9 +12,7 @@
 #include "../ClangTidyCheck.h"
 #include "../utils/ExceptionAnalyzer.h"
 
-namespace clang {
-namespace tidy {
-namespace openmp {
+namespace clang::tidy::openmp {
 
 /// Analyzes OpenMP Structured Blocks and checks that no exception escapes
 /// out of the Structured Block it was thrown in.
@@ -37,8 +35,6 @@
   utils::ExceptionAnalyzer Tracer;
 };
 
-} // namespace openmp
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::openmp
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_OPENMP_EXCEPTIONESCAPECHECK_H
diff --git a/clang-tools-extra/clang-tidy/openmp/UseDefaultNoneCheck.h b/clang-tools-extra/clang-tidy/openmp/UseDefaultNoneCheck.h
--- a/clang-tools-extra/clang-tidy/openmp/UseDefaultNoneCheck.h
+++ b/clang-tools-extra/clang-tidy/openmp/UseDefaultNoneCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace openmp {
+namespace clang::tidy::openmp {
 
 /// Finds OpenMP directives that are allowed to contain a ``default`` clause,
 /// but either don't specify it or the clause is specified but with the kind
@@ -32,8 +30,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace openmp
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::openmp
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_OPENMP_USEDEFAULTNONECHECK_H
diff --git a/clang-tools-extra/clang-tidy/performance/FasterStringFindCheck.h b/clang-tools-extra/clang-tidy/performance/FasterStringFindCheck.h
--- a/clang-tools-extra/clang-tidy/performance/FasterStringFindCheck.h
+++ b/clang-tools-extra/clang-tidy/performance/FasterStringFindCheck.h
@@ -14,9 +14,7 @@
 #include <string>
 #include <vector>
 
-namespace clang {
-namespace tidy {
-namespace performance {
+namespace clang::tidy::performance {
 
 /// Optimize calls to std::string::find() and friends when the needle passed is
 /// a single character string literal.
@@ -38,8 +36,6 @@
   const std::vector<StringRef> StringLikeClasses;
 };
 
-} // namespace performance
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::performance
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_PERFORMANCE_FASTER_STRING_FIND_H
diff --git a/clang-tools-extra/clang-tidy/performance/ForRangeCopyCheck.h b/clang-tools-extra/clang-tidy/performance/ForRangeCopyCheck.h
--- a/clang-tools-extra/clang-tidy/performance/ForRangeCopyCheck.h
+++ b/clang-tools-extra/clang-tidy/performance/ForRangeCopyCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace performance {
+namespace clang::tidy::performance {
 
 /// A check that detects copied loop variables and suggests using const
 /// references.
@@ -45,8 +43,6 @@
   const std::vector<StringRef> AllowedTypes;
 };
 
-} // namespace performance
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::performance
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_PERFORMANCE_FORRANGECOPYCHECK_H
diff --git a/clang-tools-extra/clang-tidy/performance/ImplicitConversionInLoopCheck.h b/clang-tools-extra/clang-tidy/performance/ImplicitConversionInLoopCheck.h
--- a/clang-tools-extra/clang-tidy/performance/ImplicitConversionInLoopCheck.h
+++ b/clang-tools-extra/clang-tidy/performance/ImplicitConversionInLoopCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace performance {
+namespace clang::tidy::performance {
 
 // Checks that in a for range loop, if the provided type is a reference, then
 // the underlying type is the one returned by the iterator (i.e. that there
@@ -33,8 +31,6 @@
                     const Expr *OperatorCall);
 };
 
-} // namespace performance
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::performance
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_PERFORMANCE_IMPLICIT_CONVERSION_IN_LOOP_CHECK_H_
diff --git a/clang-tools-extra/clang-tidy/performance/InefficientAlgorithmCheck.h b/clang-tools-extra/clang-tidy/performance/InefficientAlgorithmCheck.h
--- a/clang-tools-extra/clang-tidy/performance/InefficientAlgorithmCheck.h
+++ b/clang-tools-extra/clang-tidy/performance/InefficientAlgorithmCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace performance {
+namespace clang::tidy::performance {
 
 /// Warns on inefficient use of STL algorithms on associative containers.
 ///
@@ -34,8 +32,6 @@
   }
 };
 
-} // namespace performance
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::performance
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_PERFORMANCE_INEFFICIENTALGORITHMCHECK_H
diff --git a/clang-tools-extra/clang-tidy/performance/InefficientStringConcatenationCheck.h b/clang-tools-extra/clang-tidy/performance/InefficientStringConcatenationCheck.h
--- a/clang-tools-extra/clang-tidy/performance/InefficientStringConcatenationCheck.h
+++ b/clang-tools-extra/clang-tidy/performance/InefficientStringConcatenationCheck.h
@@ -12,9 +12,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace performance {
+namespace clang::tidy::performance {
 
 /// This check is to warn about the performance overhead arising from
 /// concatenating strings, using the operator+, instead of operator+=.
@@ -36,8 +34,6 @@
   const bool StrictMode;
 };
 
-} // namespace performance
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::performance
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_PERFORMANCE_INEFFICIENTSTRINGCONCATENATION_H
diff --git a/clang-tools-extra/clang-tidy/performance/InefficientVectorOperationCheck.h b/clang-tools-extra/clang-tidy/performance/InefficientVectorOperationCheck.h
--- a/clang-tools-extra/clang-tidy/performance/InefficientVectorOperationCheck.h
+++ b/clang-tools-extra/clang-tidy/performance/InefficientVectorOperationCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace performance {
+namespace clang::tidy::performance {
 
 /// Finds possible inefficient `std::vector` operations (e.g. `push_back`) in
 /// for loops that may cause unnecessary memory reallocations.
@@ -44,8 +42,6 @@
   bool EnableProto;
 };
 
-} // namespace performance
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::performance
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_PERFORMANCE_INEFFICIENT_VECTOR_OPERATION_H
diff --git a/clang-tools-extra/clang-tidy/performance/MoveConstArgCheck.h b/clang-tools-extra/clang-tidy/performance/MoveConstArgCheck.h
--- a/clang-tools-extra/clang-tidy/performance/MoveConstArgCheck.h
+++ b/clang-tools-extra/clang-tidy/performance/MoveConstArgCheck.h
@@ -12,9 +12,7 @@
 #include "../ClangTidyCheck.h"
 #include "llvm/ADT/DenseSet.h"
 
-namespace clang {
-namespace tidy {
-namespace performance {
+namespace clang::tidy::performance {
 
 /// Find casts of calculation results to bigger type. Typically from int to
 ///
@@ -43,8 +41,6 @@
   llvm::DenseSet<const CallExpr *> AlreadyCheckedMoves;
 };
 
-} // namespace performance
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::performance
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MISC_MOVECONSTANTARGUMENTCHECK_H
diff --git a/clang-tools-extra/clang-tidy/performance/MoveConstructorInitCheck.h b/clang-tools-extra/clang-tidy/performance/MoveConstructorInitCheck.h
--- a/clang-tools-extra/clang-tidy/performance/MoveConstructorInitCheck.h
+++ b/clang-tools-extra/clang-tidy/performance/MoveConstructorInitCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace performance {
+namespace clang::tidy::performance {
 
 /// The check flags user-defined move constructors that have a ctor-initializer
 /// initializing a member or base class through a copy constructor instead of a
@@ -30,8 +28,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace performance
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::performance
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_PERFORMANCE_MOVECONSTRUCTORINITCHECK_H
diff --git a/clang-tools-extra/clang-tidy/performance/NoAutomaticMoveCheck.h b/clang-tools-extra/clang-tidy/performance/NoAutomaticMoveCheck.h
--- a/clang-tools-extra/clang-tidy/performance/NoAutomaticMoveCheck.h
+++ b/clang-tools-extra/clang-tidy/performance/NoAutomaticMoveCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace performance {
+namespace clang::tidy::performance {
 
 /// Finds local variables that cannot be automatically moved due to constness.
 /// For the user-facing documentation see:
@@ -32,8 +30,6 @@
   const std::vector<StringRef> AllowedTypes;
 };
 
-} // namespace performance
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::performance
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_PERFORMANCE_NOAUTOMATICMOVECHECK_H
diff --git a/clang-tools-extra/clang-tidy/performance/NoIntToPtrCheck.h b/clang-tools-extra/clang-tidy/performance/NoIntToPtrCheck.h
--- a/clang-tools-extra/clang-tidy/performance/NoIntToPtrCheck.h
+++ b/clang-tools-extra/clang-tidy/performance/NoIntToPtrCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace performance {
+namespace clang::tidy::performance {
 
 /// Diagnoses every integer to pointer cast.
 ///
@@ -27,8 +25,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace performance
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::performance
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_PERFORMANCE_NOINTTOPTRCHECK_H
diff --git a/clang-tools-extra/clang-tidy/performance/NoexceptMoveConstructorCheck.h b/clang-tools-extra/clang-tidy/performance/NoexceptMoveConstructorCheck.h
--- a/clang-tools-extra/clang-tidy/performance/NoexceptMoveConstructorCheck.h
+++ b/clang-tools-extra/clang-tidy/performance/NoexceptMoveConstructorCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace performance {
+namespace clang::tidy::performance {
 
 /// The check flags user-defined move constructors and assignment operators not
 /// marked with `noexcept` or marked with `noexcept(expr)` where `expr`
@@ -33,8 +31,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace performance
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::performance
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_PERFORMANCE_NOEXCEPTMOVECONSTRUCTORCHECK_H
diff --git a/clang-tools-extra/clang-tidy/performance/TriviallyDestructibleCheck.h b/clang-tools-extra/clang-tidy/performance/TriviallyDestructibleCheck.h
--- a/clang-tools-extra/clang-tidy/performance/TriviallyDestructibleCheck.h
+++ b/clang-tools-extra/clang-tidy/performance/TriviallyDestructibleCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace performance {
+namespace clang::tidy::performance {
 
 /// A check that finds classes that would be trivial if not for the defaulted
 /// destructors declared out-of-line:
@@ -36,8 +34,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace performance
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::performance
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_PERFORMANCE_TRIVIALLYDESTRUCTIBLECHECK_H
diff --git a/clang-tools-extra/clang-tidy/performance/TypePromotionInMathFnCheck.h b/clang-tools-extra/clang-tidy/performance/TypePromotionInMathFnCheck.h
--- a/clang-tools-extra/clang-tidy/performance/TypePromotionInMathFnCheck.h
+++ b/clang-tools-extra/clang-tidy/performance/TypePromotionInMathFnCheck.h
@@ -12,9 +12,7 @@
 #include "../ClangTidyCheck.h"
 #include "../utils/IncludeInserter.h"
 
-namespace clang {
-namespace tidy {
-namespace performance {
+namespace clang::tidy::performance {
 
 /// Finds calls to C math library functions with implicit float to double
 /// promotions.
@@ -39,8 +37,6 @@
   utils::IncludeInserter IncludeInserter;
 };
 
-} // namespace performance
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::performance
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_PERFORMANCE_TYPE_PROMOTION_IN_MATH_FN_H
diff --git a/clang-tools-extra/clang-tidy/performance/UnnecessaryCopyInitialization.h b/clang-tools-extra/clang-tidy/performance/UnnecessaryCopyInitialization.h
--- a/clang-tools-extra/clang-tidy/performance/UnnecessaryCopyInitialization.h
+++ b/clang-tools-extra/clang-tidy/performance/UnnecessaryCopyInitialization.h
@@ -12,9 +12,7 @@
 #include "../ClangTidyCheck.h"
 #include "clang/AST/Decl.h"
 
-namespace clang {
-namespace tidy {
-namespace performance {
+namespace clang::tidy::performance {
 
 // The check detects local variable declarations that are copy initialized with
 // the const reference of a function call or the const reference of a method
@@ -46,8 +44,6 @@
   const std::vector<StringRef> ExcludedContainerTypes;
 };
 
-} // namespace performance
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::performance
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_PERFORMANCE_UNNECESSARY_COPY_INITIALIZATION_H
diff --git a/clang-tools-extra/clang-tidy/performance/UnnecessaryValueParamCheck.h b/clang-tools-extra/clang-tidy/performance/UnnecessaryValueParamCheck.h
--- a/clang-tools-extra/clang-tidy/performance/UnnecessaryValueParamCheck.h
+++ b/clang-tools-extra/clang-tidy/performance/UnnecessaryValueParamCheck.h
@@ -13,9 +13,7 @@
 #include "../utils/IncludeInserter.h"
 #include "clang/Analysis/Analyses/ExprMutationAnalyzer.h"
 
-namespace clang {
-namespace tidy {
-namespace performance {
+namespace clang::tidy::performance {
 
 /// A check that flags value parameters of expensive to copy types that
 /// can safely be converted to const references.
@@ -45,8 +43,6 @@
   const std::vector<StringRef> AllowedTypes;
 };
 
-} // namespace performance
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::performance
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_PERFORMANCE_UNNECESSARY_VALUE_PARAM_H
diff --git a/clang-tools-extra/clang-tidy/portability/RestrictSystemIncludesCheck.h b/clang-tools-extra/clang-tidy/portability/RestrictSystemIncludesCheck.h
--- a/clang-tools-extra/clang-tidy/portability/RestrictSystemIncludesCheck.h
+++ b/clang-tools-extra/clang-tidy/portability/RestrictSystemIncludesCheck.h
@@ -13,9 +13,7 @@
 #include "../GlobList.h"
 #include "clang/Lex/PPCallbacks.h"
 
-namespace clang {
-namespace tidy {
-namespace portability {
+namespace clang::tidy::portability {
 
 /// Checks for allowed includes and suggests removal of any others. If no
 /// includes are specified, the check will exit without issuing any warnings.
@@ -78,8 +76,6 @@
   const SourceManager &SM;
 };
 
-} // namespace portability 
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::portability
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_PORTABILITY_RESTRICTINCLUDESSCHECK_H
diff --git a/clang-tools-extra/clang-tidy/portability/SIMDIntrinsicsCheck.h b/clang-tools-extra/clang-tidy/portability/SIMDIntrinsicsCheck.h
--- a/clang-tools-extra/clang-tidy/portability/SIMDIntrinsicsCheck.h
+++ b/clang-tools-extra/clang-tidy/portability/SIMDIntrinsicsCheck.h
@@ -13,9 +13,7 @@
 
 #include "llvm/ADT/SmallString.h"
 
-namespace clang {
-namespace tidy {
-namespace portability {
+namespace clang::tidy::portability {
 
 /// Find SIMD intrinsics calls and suggest std::experimental::simd alternatives.
 ///
@@ -37,8 +35,6 @@
   const bool Suggest;
 };
 
-} // namespace portability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::portability
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_SIMD_INTRINSICS_CHECK_H
diff --git a/clang-tools-extra/clang-tidy/portability/StdAllocatorConstCheck.h b/clang-tools-extra/clang-tidy/portability/StdAllocatorConstCheck.h
--- a/clang-tools-extra/clang-tidy/portability/StdAllocatorConstCheck.h
+++ b/clang-tools-extra/clang-tidy/portability/StdAllocatorConstCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace portability {
+namespace clang::tidy::portability {
 
 /// Report use of ``std::vector<const T>`` (and similar containers of const
 /// elements). These are not allowed in standard C++ due to undefined
@@ -30,8 +28,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace portability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::portability
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_PORTABILITY_STDALLOCATORCONSTCHECK_H
diff --git a/clang-tools-extra/clang-tidy/readability/AvoidConstParamsInDecls.h b/clang-tools-extra/clang-tidy/readability/AvoidConstParamsInDecls.h
--- a/clang-tools-extra/clang-tidy/readability/AvoidConstParamsInDecls.h
+++ b/clang-tools-extra/clang-tidy/readability/AvoidConstParamsInDecls.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 // Detect function declarations that have const value parameters and discourage
 // them.
@@ -34,8 +32,6 @@
   const bool IgnoreMacros;
 };
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_AVOID_CONST_PARAMS_IN_DECLS_H
diff --git a/clang-tools-extra/clang-tidy/readability/BracesAroundStatementsCheck.h b/clang-tools-extra/clang-tidy/readability/BracesAroundStatementsCheck.h
--- a/clang-tools-extra/clang-tidy/readability/BracesAroundStatementsCheck.h
+++ b/clang-tools-extra/clang-tidy/readability/BracesAroundStatementsCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 /// Checks that bodies of `if` statements and loops (`for`, `range-for`,
 /// `do-while`, and `while`) are inside braces
@@ -64,8 +62,6 @@
   const unsigned ShortStatementLines;
 };
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_BRACESAROUNDSTATEMENTSCHECK_H
diff --git a/clang-tools-extra/clang-tidy/readability/ConstReturnTypeCheck.h b/clang-tools-extra/clang-tidy/readability/ConstReturnTypeCheck.h
--- a/clang-tools-extra/clang-tidy/readability/ConstReturnTypeCheck.h
+++ b/clang-tools-extra/clang-tidy/readability/ConstReturnTypeCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 /// For any function whose return type is const-qualified, suggests removal of
 /// the `const` qualifier from that return type.
@@ -33,8 +31,6 @@
    const bool IgnoreMacros;
 };
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_CONSTRETURNTYPECHECK_H
diff --git a/clang-tools-extra/clang-tidy/readability/ContainerContainsCheck.h b/clang-tools-extra/clang-tidy/readability/ContainerContainsCheck.h
--- a/clang-tools-extra/clang-tidy/readability/ContainerContainsCheck.h
+++ b/clang-tools-extra/clang-tidy/readability/ContainerContainsCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 /// Finds usages of `container.count()` and `find() == end()` which should be
 /// replaced by a call to the `container.contains()` method introduced in C++20.
@@ -33,8 +31,6 @@
   }
 };
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_CONTAINERCONTAINSCHECK_H
diff --git a/clang-tools-extra/clang-tidy/readability/ContainerDataPointerCheck.h b/clang-tools-extra/clang-tidy/readability/ContainerDataPointerCheck.h
--- a/clang-tools-extra/clang-tidy/readability/ContainerDataPointerCheck.h
+++ b/clang-tools-extra/clang-tidy/readability/ContainerDataPointerCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 /// Checks whether a call to `operator[]` and `&` can be replaced with a call to
 /// `data()`.
 ///
@@ -38,8 +36,6 @@
     return TK_IgnoreUnlessSpelledInSource;
   }
 };
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_CONTAINERDATAPOINTERCHECK_H
diff --git a/clang-tools-extra/clang-tidy/readability/ContainerSizeEmptyCheck.h b/clang-tools-extra/clang-tidy/readability/ContainerSizeEmptyCheck.h
--- a/clang-tools-extra/clang-tidy/readability/ContainerSizeEmptyCheck.h
+++ b/clang-tools-extra/clang-tidy/readability/ContainerSizeEmptyCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 /// Checks whether a call to the `size()` method can be replaced with a call to
 /// `empty()`.
@@ -38,8 +36,6 @@
   }
 };
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_CONTAINERSIZEEMPTYCHECK_H
diff --git a/clang-tools-extra/clang-tidy/readability/ConvertMemberFunctionsToStatic.h b/clang-tools-extra/clang-tidy/readability/ConvertMemberFunctionsToStatic.h
--- a/clang-tools-extra/clang-tidy/readability/ConvertMemberFunctionsToStatic.h
+++ b/clang-tools-extra/clang-tidy/readability/ConvertMemberFunctionsToStatic.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 /// This check finds C++ class methods than can be made static
 /// because they don't use the 'this' pointer.
@@ -29,8 +27,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_CONVERTMEMFUNCTOSTATIC_H
diff --git a/clang-tools-extra/clang-tidy/readability/DeleteNullPointerCheck.h b/clang-tools-extra/clang-tidy/readability/DeleteNullPointerCheck.h
--- a/clang-tools-extra/clang-tidy/readability/DeleteNullPointerCheck.h
+++ b/clang-tools-extra/clang-tidy/readability/DeleteNullPointerCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 /// Check whether the 'if' statement is unnecessary before calling 'delete' on a
 /// pointer.
@@ -31,8 +29,6 @@
   }
 };
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_DELETE_NULL_POINTER_H
diff --git a/clang-tools-extra/clang-tidy/readability/DuplicateIncludeCheck.h b/clang-tools-extra/clang-tidy/readability/DuplicateIncludeCheck.h
--- a/clang-tools-extra/clang-tidy/readability/DuplicateIncludeCheck.h
+++ b/clang-tools-extra/clang-tidy/readability/DuplicateIncludeCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 /// \brief Find and remove duplicate #include directives.
 ///
@@ -28,8 +26,6 @@
                            Preprocessor *ModuleExpanderPP) override;
 };
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_DUPLICATE_INCLUDE_CHECK_H
diff --git a/clang-tools-extra/clang-tidy/readability/ElseAfterReturnCheck.h b/clang-tools-extra/clang-tidy/readability/ElseAfterReturnCheck.h
--- a/clang-tools-extra/clang-tidy/readability/ElseAfterReturnCheck.h
+++ b/clang-tools-extra/clang-tidy/readability/ElseAfterReturnCheck.h
@@ -12,9 +12,7 @@
 #include "../ClangTidyCheck.h"
 #include "llvm/ADT/DenseMap.h"
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 /// Flags the usages of `else` after `return`.
 ///
@@ -41,8 +39,6 @@
   ConditionalBranchMap PPConditionals;
 };
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_ELSEAFTERRETURNCHECK_H
diff --git a/clang-tools-extra/clang-tidy/readability/FunctionCognitiveComplexityCheck.h b/clang-tools-extra/clang-tidy/readability/FunctionCognitiveComplexityCheck.h
--- a/clang-tools-extra/clang-tidy/readability/FunctionCognitiveComplexityCheck.h
+++ b/clang-tools-extra/clang-tidy/readability/FunctionCognitiveComplexityCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 /// Checks function Cognitive Complexity metric.
 ///
@@ -48,8 +46,6 @@
   const bool IgnoreMacros;
 };
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_FUNCTIONCOGNITIVECOMPLEXITYCHECK_H
diff --git a/clang-tools-extra/clang-tidy/readability/FunctionSizeCheck.h b/clang-tools-extra/clang-tidy/readability/FunctionSizeCheck.h
--- a/clang-tools-extra/clang-tidy/readability/FunctionSizeCheck.h
+++ b/clang-tools-extra/clang-tidy/readability/FunctionSizeCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 /// Checks for large functions based on various metrics.
 ///
@@ -51,8 +49,6 @@
   const unsigned VariableThreshold;
 };
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_FUNCTIONSIZECHECK_H
diff --git a/clang-tools-extra/clang-tidy/readability/IdentifierLengthCheck.h b/clang-tools-extra/clang-tidy/readability/IdentifierLengthCheck.h
--- a/clang-tools-extra/clang-tidy/readability/IdentifierLengthCheck.h
+++ b/clang-tools-extra/clang-tidy/readability/IdentifierLengthCheck.h
@@ -13,9 +13,7 @@
 #include "../ClangTidyCheck.h"
 #include "llvm/Support/Regex.h"
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 /// Warns about identifiers names whose length is too short.
 ///
@@ -47,8 +45,6 @@
   llvm::Regex IgnoredParameterNames;
 };
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_IDENTIFIERLENGTHCHECK_H
diff --git a/clang-tools-extra/clang-tidy/readability/IdentifierNamingCheck.h b/clang-tools-extra/clang-tidy/readability/IdentifierNamingCheck.h
--- a/clang-tools-extra/clang-tidy/readability/IdentifierNamingCheck.h
+++ b/clang-tools-extra/clang-tidy/readability/IdentifierNamingCheck.h
@@ -11,8 +11,7 @@
 
 #include "../utils/RenamerClangTidyCheck.h"
 #include <optional>
-namespace clang {
-namespace tidy {
+namespace clang::tidy {
 namespace readability {
 
 enum StyleKind : int;
@@ -211,7 +210,6 @@
       std::pair<readability::IdentifierNamingCheck::CaseType, StringRef>>
   getEnumMapping();
 };
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_IDENTIFIERNAMINGCHECK_H
diff --git a/clang-tools-extra/clang-tidy/readability/ImplicitBoolConversionCheck.h b/clang-tools-extra/clang-tidy/readability/ImplicitBoolConversionCheck.h
--- a/clang-tools-extra/clang-tidy/readability/ImplicitBoolConversionCheck.h
+++ b/clang-tools-extra/clang-tidy/readability/ImplicitBoolConversionCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 /// Checks for use of implicit bool conversions in expressions.
 ///
@@ -40,8 +38,6 @@
   const bool AllowPointerConditions;
 };
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_IMPLICIT_BOOL_CONVERSION_H
diff --git a/clang-tools-extra/clang-tidy/readability/InconsistentDeclarationParameterNameCheck.h b/clang-tools-extra/clang-tidy/readability/InconsistentDeclarationParameterNameCheck.h
--- a/clang-tools-extra/clang-tidy/readability/InconsistentDeclarationParameterNameCheck.h
+++ b/clang-tools-extra/clang-tidy/readability/InconsistentDeclarationParameterNameCheck.h
@@ -13,9 +13,7 @@
 
 #include "llvm/ADT/DenseSet.h"
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 /// Checks for declarations of functions which differ in parameter names.
 ///
@@ -45,8 +43,6 @@
   const bool Strict;
 };
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_INCONSISTENT_DECLARATION_PARAMETER_NAME_H
diff --git a/clang-tools-extra/clang-tidy/readability/IsolateDeclarationCheck.h b/clang-tools-extra/clang-tidy/readability/IsolateDeclarationCheck.h
--- a/clang-tools-extra/clang-tidy/readability/IsolateDeclarationCheck.h
+++ b/clang-tools-extra/clang-tidy/readability/IsolateDeclarationCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 /// This check diagnoses all DeclStmt's declaring more than one variable and
 /// tries to refactor the code to one statement per declaration.
@@ -28,8 +26,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_ISOLATEDECLCHECK_H
diff --git a/clang-tools-extra/clang-tidy/readability/MagicNumbersCheck.h b/clang-tools-extra/clang-tidy/readability/MagicNumbersCheck.h
--- a/clang-tools-extra/clang-tidy/readability/MagicNumbersCheck.h
+++ b/clang-tools-extra/clang-tidy/readability/MagicNumbersCheck.h
@@ -14,9 +14,7 @@
 #include <llvm/ADT/APFloat.h>
 #include <llvm/ADT/SmallVector.h>
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 /// Detects magic numbers, integer and floating point literals embedded in code.
 ///
@@ -102,8 +100,6 @@
       IgnoredDoublePointValues;
 };
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_MAGICNUMBERSCHECK_H
diff --git a/clang-tools-extra/clang-tidy/readability/MakeMemberFunctionConstCheck.h b/clang-tools-extra/clang-tidy/readability/MakeMemberFunctionConstCheck.h
--- a/clang-tools-extra/clang-tidy/readability/MakeMemberFunctionConstCheck.h
+++ b/clang-tools-extra/clang-tidy/readability/MakeMemberFunctionConstCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 /// Finds non-static member functions that can be made 'const'.
 ///
@@ -30,8 +28,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_MAKEMEMBERFUNCTIONCONSTCHECK_H
diff --git a/clang-tools-extra/clang-tidy/readability/MisleadingIndentationCheck.h b/clang-tools-extra/clang-tidy/readability/MisleadingIndentationCheck.h
--- a/clang-tools-extra/clang-tidy/readability/MisleadingIndentationCheck.h
+++ b/clang-tools-extra/clang-tidy/readability/MisleadingIndentationCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 /// Checks the code for dangling else, and possible misleading indentations due
 /// to missing braces. Note that this check only works as expected when the tabs
@@ -37,8 +35,6 @@
   void missingBracesCheck(const SourceManager &SM, const CompoundStmt *CStmt);
 };
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_MISLEADING_INDENTATION_H
diff --git a/clang-tools-extra/clang-tidy/readability/MisplacedArrayIndexCheck.h b/clang-tools-extra/clang-tidy/readability/MisplacedArrayIndexCheck.h
--- a/clang-tools-extra/clang-tidy/readability/MisplacedArrayIndexCheck.h
+++ b/clang-tools-extra/clang-tidy/readability/MisplacedArrayIndexCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 /// Warn about unusual array index syntax (`index[array]` instead of
 /// `array[index]`).
@@ -28,8 +26,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_MISPLACED_ARRAY_INDEX_H
diff --git a/clang-tools-extra/clang-tidy/readability/NamedParameterCheck.h b/clang-tools-extra/clang-tidy/readability/NamedParameterCheck.h
--- a/clang-tools-extra/clang-tidy/readability/NamedParameterCheck.h
+++ b/clang-tools-extra/clang-tidy/readability/NamedParameterCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 /// Find functions with unnamed arguments.
 ///
@@ -37,8 +35,6 @@
   }
 };
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_NAMEDPARAMETERCHECK_H
diff --git a/clang-tools-extra/clang-tidy/readability/NamespaceCommentCheck.h b/clang-tools-extra/clang-tidy/readability/NamespaceCommentCheck.h
--- a/clang-tools-extra/clang-tidy/readability/NamespaceCommentCheck.h
+++ b/clang-tools-extra/clang-tidy/readability/NamespaceCommentCheck.h
@@ -12,9 +12,7 @@
 #include "../ClangTidyCheck.h"
 #include "llvm/Support/Regex.h"
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 /// Checks that long namespaces have a closing comment.
 ///
@@ -39,8 +37,6 @@
   llvm::SmallVector<SourceLocation, 4> Ends;
 };
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_NAMESPACECOMMENTCHECK_H
diff --git a/clang-tools-extra/clang-tidy/readability/NonConstParameterCheck.h b/clang-tools-extra/clang-tidy/readability/NonConstParameterCheck.h
--- a/clang-tools-extra/clang-tidy/readability/NonConstParameterCheck.h
+++ b/clang-tools-extra/clang-tidy/readability/NonConstParameterCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 /// Warn when a pointer function parameter can be const.
 ///
@@ -59,8 +57,6 @@
   void diagnoseNonConstParameters();
 };
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_NON_CONST_PARAMETER_H
diff --git a/clang-tools-extra/clang-tidy/readability/QualifiedAutoCheck.h b/clang-tools-extra/clang-tidy/readability/QualifiedAutoCheck.h
--- a/clang-tools-extra/clang-tidy/readability/QualifiedAutoCheck.h
+++ b/clang-tools-extra/clang-tidy/readability/QualifiedAutoCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 /// Finds variables declared as auto that could be declared as:
 /// 'auto*' or 'const auto *' and reference variables declared as:
@@ -37,8 +35,6 @@
   const bool AddConstToQualified;
 };
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_QUALIFIEDAUTOCHECK_H
diff --git a/clang-tools-extra/clang-tidy/readability/RedundantAccessSpecifiersCheck.h b/clang-tools-extra/clang-tidy/readability/RedundantAccessSpecifiersCheck.h
--- a/clang-tools-extra/clang-tidy/readability/RedundantAccessSpecifiersCheck.h
+++ b/clang-tools-extra/clang-tidy/readability/RedundantAccessSpecifiersCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 /// Detects redundant access specifiers inside classes, structs, and unions.
 ///
@@ -35,8 +33,6 @@
   const bool CheckFirstDeclaration;
 };
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_REDUNDANTACCESSSPECIFIERSCHECK_H
diff --git a/clang-tools-extra/clang-tidy/readability/RedundantControlFlowCheck.h b/clang-tools-extra/clang-tidy/readability/RedundantControlFlowCheck.h
--- a/clang-tools-extra/clang-tidy/readability/RedundantControlFlowCheck.h
+++ b/clang-tools-extra/clang-tidy/readability/RedundantControlFlowCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 /// Eliminates redundant `return` statements at the end of a function that
 /// returns `void`.
@@ -47,8 +45,6 @@
                        const char *Diag);
 };
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_REDUNDANT_CONTROL_FLOW_H
diff --git a/clang-tools-extra/clang-tidy/readability/RedundantDeclarationCheck.h b/clang-tools-extra/clang-tidy/readability/RedundantDeclarationCheck.h
--- a/clang-tools-extra/clang-tidy/readability/RedundantDeclarationCheck.h
+++ b/clang-tools-extra/clang-tidy/readability/RedundantDeclarationCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 /// Find redundant variable declarations.
 ///
@@ -30,8 +28,6 @@
   const bool IgnoreMacros;
 };
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_REDUNDANT_DECLARATION_H
diff --git a/clang-tools-extra/clang-tidy/readability/RedundantFunctionPtrDereferenceCheck.h b/clang-tools-extra/clang-tidy/readability/RedundantFunctionPtrDereferenceCheck.h
--- a/clang-tools-extra/clang-tidy/readability/RedundantFunctionPtrDereferenceCheck.h
+++ b/clang-tools-extra/clang-tidy/readability/RedundantFunctionPtrDereferenceCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 /// Eliminate redundant dereferences of a function pointer.
 ///
@@ -27,8 +25,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_REDUNDANT_FUNCTION_PTR_DEREFERENCE_H
diff --git a/clang-tools-extra/clang-tidy/readability/RedundantMemberInitCheck.h b/clang-tools-extra/clang-tidy/readability/RedundantMemberInitCheck.h
--- a/clang-tools-extra/clang-tidy/readability/RedundantMemberInitCheck.h
+++ b/clang-tools-extra/clang-tidy/readability/RedundantMemberInitCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 /// Finds member initializations that are unnecessary because the same default
 /// constructor would be called if they were not present.
@@ -40,8 +38,6 @@
   bool IgnoreBaseInCopyConstructors;
 };
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_REDUNDANT_MEMBER_INIT_H
diff --git a/clang-tools-extra/clang-tidy/readability/RedundantPreprocessorCheck.h b/clang-tools-extra/clang-tidy/readability/RedundantPreprocessorCheck.h
--- a/clang-tools-extra/clang-tidy/readability/RedundantPreprocessorCheck.h
+++ b/clang-tools-extra/clang-tidy/readability/RedundantPreprocessorCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 /// This check flags redundant preprocessor directives: nested directives with
 /// the same condition.
@@ -28,8 +26,6 @@
                            Preprocessor *ModuleExpanderPP) override;
 };
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_REDUNDANTPREPROCESSORCHECK_H
diff --git a/clang-tools-extra/clang-tidy/readability/RedundantSmartptrGetCheck.h b/clang-tools-extra/clang-tidy/readability/RedundantSmartptrGetCheck.h
--- a/clang-tools-extra/clang-tidy/readability/RedundantSmartptrGetCheck.h
+++ b/clang-tools-extra/clang-tidy/readability/RedundantSmartptrGetCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 /// Find and remove redundant calls to smart pointer's `.get()` method.
 ///
@@ -43,8 +41,6 @@
   const bool IgnoreMacros;
 };
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_REDUNDANTSMARTPTRGETCHECK_H
diff --git a/clang-tools-extra/clang-tidy/readability/RedundantStringCStrCheck.h b/clang-tools-extra/clang-tidy/readability/RedundantStringCStrCheck.h
--- a/clang-tools-extra/clang-tidy/readability/RedundantStringCStrCheck.h
+++ b/clang-tools-extra/clang-tidy/readability/RedundantStringCStrCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 /// Finds unnecessary calls to `std::string::c_str()`.
 class RedundantStringCStrCheck : public ClangTidyCheck {
@@ -27,8 +25,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_REDUNDANTSTRINGCSTRCHECK_H
diff --git a/clang-tools-extra/clang-tidy/readability/RedundantStringInitCheck.h b/clang-tools-extra/clang-tidy/readability/RedundantStringInitCheck.h
--- a/clang-tools-extra/clang-tidy/readability/RedundantStringInitCheck.h
+++ b/clang-tools-extra/clang-tidy/readability/RedundantStringInitCheck.h
@@ -13,9 +13,7 @@
 #include <string>
 #include <vector>
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 /// Finds unnecessary string initializations.
 class RedundantStringInitCheck : public ClangTidyCheck {
@@ -32,8 +30,6 @@
   std::vector<StringRef> StringNames;
 };
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_REDUNDANT_STRING_INIT_H
diff --git a/clang-tools-extra/clang-tidy/readability/SimplifyBooleanExprCheck.h b/clang-tools-extra/clang-tidy/readability/SimplifyBooleanExprCheck.h
--- a/clang-tools-extra/clang-tidy/readability/SimplifyBooleanExprCheck.h
+++ b/clang-tools-extra/clang-tidy/readability/SimplifyBooleanExprCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 /// Looks for boolean expressions involving boolean constants and simplifies
 /// them to use the appropriate boolean expression directly.
@@ -72,8 +70,6 @@
   const bool SimplifyDeMorganRelaxed;
 };
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_SIMPLIFY_BOOLEAN_EXPR_H
diff --git a/clang-tools-extra/clang-tidy/readability/SimplifySubscriptExprCheck.h b/clang-tools-extra/clang-tidy/readability/SimplifySubscriptExprCheck.h
--- a/clang-tools-extra/clang-tidy/readability/SimplifySubscriptExprCheck.h
+++ b/clang-tools-extra/clang-tidy/readability/SimplifySubscriptExprCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 /// Simplifies subscript expressions.
 ///
@@ -36,8 +34,6 @@
   const std::vector<StringRef> Types;
 };
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_SIMPLIFYSUBSCRIPTEXPRCHECK_H
diff --git a/clang-tools-extra/clang-tidy/readability/StaticAccessedThroughInstanceCheck.h b/clang-tools-extra/clang-tidy/readability/StaticAccessedThroughInstanceCheck.h
--- a/clang-tools-extra/clang-tidy/readability/StaticAccessedThroughInstanceCheck.h
+++ b/clang-tools-extra/clang-tidy/readability/StaticAccessedThroughInstanceCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 /// Checks for member expressions that access static members through
 /// instances and replaces them with uses of the appropriate qualified-id.
@@ -38,8 +36,6 @@
   const unsigned NameSpecifierNestingThreshold;
 };
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_STATIC_ACCESSED_THROUGH_INSTANCE_H
diff --git a/clang-tools-extra/clang-tidy/readability/StaticDefinitionInAnonymousNamespaceCheck.h b/clang-tools-extra/clang-tidy/readability/StaticDefinitionInAnonymousNamespaceCheck.h
--- a/clang-tools-extra/clang-tidy/readability/StaticDefinitionInAnonymousNamespaceCheck.h
+++ b/clang-tools-extra/clang-tidy/readability/StaticDefinitionInAnonymousNamespaceCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 /// Finds static function and variable definitions in anonymous namespace.
 ///
@@ -28,8 +26,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_STATIC_DEFINITION_IN_ANONYMOUS_NAMESPACE_H
diff --git a/clang-tools-extra/clang-tidy/readability/StringCompareCheck.h b/clang-tools-extra/clang-tidy/readability/StringCompareCheck.h
--- a/clang-tools-extra/clang-tidy/readability/StringCompareCheck.h
+++ b/clang-tools-extra/clang-tidy/readability/StringCompareCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 /// This check flags all calls compare when used to check for string
 /// equality or inequality.
@@ -31,8 +29,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_STRINGCOMPARECHECK_H
diff --git a/clang-tools-extra/clang-tidy/readability/SuspiciousCallArgumentCheck.h b/clang-tools-extra/clang-tidy/readability/SuspiciousCallArgumentCheck.h
--- a/clang-tools-extra/clang-tidy/readability/SuspiciousCallArgumentCheck.h
+++ b/clang-tools-extra/clang-tidy/readability/SuspiciousCallArgumentCheck.h
@@ -13,9 +13,7 @@
 #include "llvm/ADT/StringSet.h"
 #include <optional>
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 /// Finds function calls where the arguments passed are provided out of order,
 /// based on the difference between the argument name and the parameter names
@@ -94,8 +92,6 @@
                        BoundKind BK) const;
 };
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_SUSPICIOUSCALLARGUMENTCHECK_H
diff --git a/clang-tools-extra/clang-tidy/readability/UniqueptrDeleteReleaseCheck.h b/clang-tools-extra/clang-tidy/readability/UniqueptrDeleteReleaseCheck.h
--- a/clang-tools-extra/clang-tidy/readability/UniqueptrDeleteReleaseCheck.h
+++ b/clang-tools-extra/clang-tidy/readability/UniqueptrDeleteReleaseCheck.h
@@ -11,9 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 /// Flags statements of the form ``delete <unique_ptr expr>.release();`` and
 /// replaces them with: ``<unique_ptr expr> = nullptr;``
@@ -34,8 +32,6 @@
   const bool PreferResetCall;
 };
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_UNIQUEPTR_DELETE_RELEASE_H
diff --git a/clang-tools-extra/clang-tidy/readability/UppercaseLiteralSuffixCheck.h b/clang-tools-extra/clang-tidy/readability/UppercaseLiteralSuffixCheck.h
--- a/clang-tools-extra/clang-tidy/readability/UppercaseLiteralSuffixCheck.h
+++ b/clang-tools-extra/clang-tidy/readability/UppercaseLiteralSuffixCheck.h
@@ -12,9 +12,7 @@
 #include "../ClangTidyCheck.h"
 #include "../utils/OptionsUtils.h"
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 /// Detects when the integral literal or floating point literal has
 /// non-uppercase suffix, and suggests to make the suffix uppercase.
@@ -40,8 +38,6 @@
   const bool IgnoreMacros;
 };
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_UPPERCASELITERALSUFFIXCHECK_H
diff --git a/clang-tools-extra/clang-tidy/readability/UseAnyOfAllOfCheck.h b/clang-tools-extra/clang-tidy/readability/UseAnyOfAllOfCheck.h
--- a/clang-tools-extra/clang-tidy/readability/UseAnyOfAllOfCheck.h
+++ b/clang-tools-extra/clang-tidy/readability/UseAnyOfAllOfCheck.h
@@ -12,9 +12,7 @@
 #include "../ClangTidyCheck.h"
 #include "../utils/IncludeInserter.h"
 
-namespace clang {
-namespace tidy {
-namespace readability {
+namespace clang::tidy::readability {
 
 /// Finds ranged-based for loops that can be replaced by a call to std::any_of
 /// or std::all_of.
@@ -33,8 +31,6 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace readability
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::readability
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_USEALGORITHMCHECK_H
diff --git a/clang-tools-extra/clang-tidy/tool/ClangTidyMain.h b/clang-tools-extra/clang-tidy/tool/ClangTidyMain.h
--- a/clang-tools-extra/clang-tidy/tool/ClangTidyMain.h
+++ b/clang-tools-extra/clang-tidy/tool/ClangTidyMain.h
@@ -14,10 +14,8 @@
 ///
 //===----------------------------------------------------------------------===//
 
-namespace clang {
-namespace tidy {
+namespace clang::tidy {
 
 int clangTidyMain(int argc, const char **argv);
 
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy
diff --git a/clang-tools-extra/clang-tidy/utils/ASTUtils.h b/clang-tools-extra/clang-tidy/utils/ASTUtils.h
--- a/clang-tools-extra/clang-tidy/utils/ASTUtils.h
+++ b/clang-tools-extra/clang-tidy/utils/ASTUtils.h
@@ -11,9 +11,7 @@
 
 #include "clang/AST/AST.h"
 
-namespace clang {
-namespace tidy {
-namespace utils {
+namespace clang::tidy::utils {
 // Returns the (closest) Function declaration surrounding |Statement| or NULL.
 const FunctionDecl *getSurroundingFunction(ASTContext &Context,
                                            const Stmt &Statement);
@@ -38,8 +36,6 @@
 // FIXME: false-negative if the entire range is fully expanded from a macro.
 bool rangeCanBeFixed(SourceRange Range, const SourceManager *SM);
 
-} // namespace utils
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::utils
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_ASTUTILS_H
diff --git a/clang-tools-extra/clang-tidy/utils/Aliasing.h b/clang-tools-extra/clang-tidy/utils/Aliasing.h
--- a/clang-tools-extra/clang-tidy/utils/Aliasing.h
+++ b/clang-tools-extra/clang-tidy/utils/Aliasing.h
@@ -11,9 +11,7 @@
 
 #include "clang/AST/Decl.h"
 
-namespace clang {
-namespace tidy {
-namespace utils {
+namespace clang::tidy::utils {
 
 /// Returns whether \p Var has a pointer or reference in \p Func.
 ///
@@ -29,8 +27,6 @@
 
 bool hasPtrOrReferenceInFunc(const Decl *Func, const VarDecl *Var);
 
-} // namespace utils
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::utils
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_UTILS_ALIASING_H
diff --git a/clang-tools-extra/clang-tidy/utils/DeclRefExprUtils.h b/clang-tools-extra/clang-tidy/utils/DeclRefExprUtils.h
--- a/clang-tools-extra/clang-tidy/utils/DeclRefExprUtils.h
+++ b/clang-tools-extra/clang-tidy/utils/DeclRefExprUtils.h
@@ -13,10 +13,7 @@
 #include "clang/AST/Type.h"
 #include "llvm/ADT/SmallPtrSet.h"
 
-namespace clang {
-namespace tidy {
-namespace utils {
-namespace decl_ref_expr {
+namespace clang::tidy::utils::decl_ref_expr {
 
 /// Returns true if all ``DeclRefExpr`` to the variable within ``Stmt``
 /// do not modify it.
@@ -51,9 +48,6 @@
 bool isCopyAssignmentArgument(const DeclRefExpr &DeclRef, const Decl &Decl,
                               ASTContext &Context);
 
-} // namespace decl_ref_expr
-} // namespace utils
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::utils::decl_ref_expr
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_UTILS_DECLREFEXPRUTILS_H
diff --git a/clang-tools-extra/clang-tidy/utils/ExceptionAnalyzer.h b/clang-tools-extra/clang-tidy/utils/ExceptionAnalyzer.h
--- a/clang-tools-extra/clang-tidy/utils/ExceptionAnalyzer.h
+++ b/clang-tools-extra/clang-tidy/utils/ExceptionAnalyzer.h
@@ -14,9 +14,7 @@
 #include "llvm/ADT/SmallSet.h"
 #include "llvm/ADT/StringSet.h"
 
-namespace clang {
-namespace tidy {
-namespace utils {
+namespace clang::tidy::utils {
 
 /// This class analysis if a `FunctionDecl` can in principle throw an
 /// exception, either directly or indirectly. It can be configured to ignore
@@ -149,8 +147,6 @@
   std::map<const FunctionDecl *, ExceptionInfo> FunctionCache;
 };
 
-} // namespace utils
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::utils
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_UTILS_EXCEPTION_ANALYZER_H
diff --git a/clang-tools-extra/clang-tidy/utils/ExprSequence.h b/clang-tools-extra/clang-tidy/utils/ExprSequence.h
--- a/clang-tools-extra/clang-tidy/utils/ExprSequence.h
+++ b/clang-tools-extra/clang-tidy/utils/ExprSequence.h
@@ -17,9 +17,7 @@
 
 #include "../ClangTidy.h"
 
-namespace clang {
-namespace tidy {
-namespace utils {
+namespace clang::tidy::utils {
 
 /// Provides information about the evaluation order of (sub-)expressions within
 /// a `CFGBlock`.
@@ -117,8 +115,6 @@
   llvm::DenseMap<const Stmt *, const CFGBlock *> Map;
 };
 
-} // namespace utils
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::utils
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_EXPRSEQUENCE_H
diff --git a/clang-tools-extra/clang-tidy/utils/FileExtensionsUtils.h b/clang-tools-extra/clang-tidy/utils/FileExtensionsUtils.h
--- a/clang-tools-extra/clang-tidy/utils/FileExtensionsUtils.h
+++ b/clang-tools-extra/clang-tidy/utils/FileExtensionsUtils.h
@@ -15,9 +15,7 @@
 #include "llvm/ADT/StringRef.h"
 #include <optional>
 
-namespace clang {
-namespace tidy {
-namespace utils {
+namespace clang::tidy::utils {
 
 typedef llvm::SmallSet<llvm::StringRef, 5> FileExtensionsSet;
 
@@ -61,8 +59,6 @@
 bool isFileExtension(StringRef FileName,
                      const FileExtensionsSet &FileExtensions);
 
-} // namespace utils
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::utils
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_UTILS_FILE_EXTENSIONS_UTILS_H
diff --git a/clang-tools-extra/clang-tidy/utils/FixItHintUtils.h b/clang-tools-extra/clang-tidy/utils/FixItHintUtils.h
--- a/clang-tools-extra/clang-tidy/utils/FixItHintUtils.h
+++ b/clang-tools-extra/clang-tidy/utils/FixItHintUtils.h
@@ -14,10 +14,7 @@
 #include "clang/Sema/DeclSpec.h"
 #include <optional>
 
-namespace clang {
-namespace tidy {
-namespace utils {
-namespace fixit {
+namespace clang::tidy::utils::fixit {
 
 /// Creates fix to make ``VarDecl`` a reference by adding ``&``.
 FixItHint changeVarDeclToReference(const VarDecl &Var, ASTContext &Context);
@@ -47,9 +44,6 @@
                       DeclSpec::TQ Qualifier,
                       QualifierTarget CT = QualifierTarget::Pointee,
                       QualifierPolicy CP = QualifierPolicy::Left);
-} // namespace fixit
-} // namespace utils
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::utils::fixit
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_UTILS_FIXITHINTUTILS_H
diff --git a/clang-tools-extra/clang-tidy/utils/HeaderGuard.h b/clang-tools-extra/clang-tidy/utils/HeaderGuard.h
--- a/clang-tools-extra/clang-tidy/utils/HeaderGuard.h
+++ b/clang-tools-extra/clang-tidy/utils/HeaderGuard.h
@@ -12,9 +12,7 @@
 #include "../ClangTidyCheck.h"
 #include "../utils/FileExtensionsUtils.h"
 
-namespace clang {
-namespace tidy {
-namespace utils {
+namespace clang::tidy::utils {
 
 /// Finds and fixes header guards.
 /// The check supports these options:
@@ -63,8 +61,6 @@
   utils::FileExtensionsSet HeaderFileExtensions;
 };
 
-} // namespace utils
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::utils
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_UTILS_HEADERGUARD_H
diff --git a/clang-tools-extra/clang-tidy/utils/IncludeInserter.h b/clang-tools-extra/clang-tidy/utils/IncludeInserter.h
--- a/clang-tools-extra/clang-tidy/utils/IncludeInserter.h
+++ b/clang-tools-extra/clang-tidy/utils/IncludeInserter.h
@@ -17,8 +17,7 @@
 
 namespace clang {
 class Preprocessor;
-namespace tidy {
-namespace utils {
+namespace tidy::utils {
 
 /// Produces fixes to insert specified includes to source files, if not
 /// yet present.
@@ -99,7 +98,6 @@
   friend class IncludeInserterCallback;
 };
 
-} // namespace utils
-} // namespace tidy
+} // namespace tidy::utils
 } // namespace clang
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_INCLUDEINSERTER_H
diff --git a/clang-tools-extra/clang-tidy/utils/IncludeSorter.h b/clang-tools-extra/clang-tidy/utils/IncludeSorter.h
--- a/clang-tools-extra/clang-tidy/utils/IncludeSorter.h
+++ b/clang-tools-extra/clang-tidy/utils/IncludeSorter.h
@@ -13,8 +13,7 @@
 #include <optional>
 #include <string>
 
-namespace clang {
-namespace tidy {
+namespace clang::tidy {
 namespace utils {
 
 /// Class used by ``IncludeInserterCallback`` to record the names of the
@@ -73,6 +72,5 @@
   static ArrayRef<std::pair<utils::IncludeSorter::IncludeStyle, StringRef>>
   getEnumMapping();
 };
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_INCLUDESORTER_H
diff --git a/clang-tools-extra/clang-tidy/utils/LexerUtils.h b/clang-tools-extra/clang-tidy/utils/LexerUtils.h
--- a/clang-tools-extra/clang-tidy/utils/LexerUtils.h
+++ b/clang-tools-extra/clang-tidy/utils/LexerUtils.h
@@ -18,9 +18,7 @@
 
 class Stmt;
 
-namespace tidy {
-namespace utils {
-namespace lexer {
+namespace tidy::utils::lexer {
 
 /// Returns previous token or ``tok::unknown`` if not found.
 Token getPreviousToken(SourceLocation Location, const SourceManager &SM,
@@ -114,9 +112,7 @@
 SourceLocation getUnifiedEndLoc(const Stmt &S, const SourceManager &SM,
                                 const LangOptions &LangOpts);
 
-} // namespace lexer
-} // namespace utils
-} // namespace tidy
+} // namespace tidy::utils::lexer
 } // namespace clang
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_UTILS_LEXER_UTILS_H
diff --git a/clang-tools-extra/clang-tidy/utils/Matchers.h b/clang-tools-extra/clang-tidy/utils/Matchers.h
--- a/clang-tools-extra/clang-tidy/utils/Matchers.h
+++ b/clang-tools-extra/clang-tidy/utils/Matchers.h
@@ -13,9 +13,7 @@
 #include "clang/ASTMatchers/ASTMatchers.h"
 #include <optional>
 
-namespace clang {
-namespace tidy {
-namespace matchers {
+namespace clang::tidy::matchers {
 
 AST_MATCHER(BinaryOperator, isRelationalOperator) {
   return Node.isRelationalOp();
@@ -122,8 +120,6 @@
       new MatchesAnyListedNameMatcher(NameList));
 }
 
-} // namespace matchers
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::matchers
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_UTILS_MATCHERS_H
diff --git a/clang-tools-extra/clang-tidy/utils/NamespaceAliaser.h b/clang-tools-extra/clang-tidy/utils/NamespaceAliaser.h
--- a/clang-tools-extra/clang-tidy/utils/NamespaceAliaser.h
+++ b/clang-tools-extra/clang-tidy/utils/NamespaceAliaser.h
@@ -18,9 +18,7 @@
 #include <map>
 #include <optional>
 
-namespace clang {
-namespace tidy {
-namespace utils {
+namespace clang::tidy::utils {
 
 // This class creates function-level namespace aliases.
 class NamespaceAliaser {
@@ -45,8 +43,6 @@
       AddedAliases;
 };
 
-} // namespace utils
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::utils
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_NAMESPACEALIASER_H
diff --git a/clang-tools-extra/clang-tidy/utils/OptionsUtils.h b/clang-tools-extra/clang-tidy/utils/OptionsUtils.h
--- a/clang-tools-extra/clang-tidy/utils/OptionsUtils.h
+++ b/clang-tools-extra/clang-tidy/utils/OptionsUtils.h
@@ -13,10 +13,7 @@
 #include <string>
 #include <vector>
 
-namespace clang {
-namespace tidy {
-namespace utils {
-namespace options {
+namespace clang::tidy::utils::options {
 
 /// Parse a semicolon separated list of strings.
 std::vector<StringRef> parseStringList(StringRef Option);
@@ -27,9 +24,6 @@
 /// ``parseStringList``.
 std::string serializeStringList(ArrayRef<StringRef> Strings);
 
-} // namespace options
-} // namespace utils
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::utils::options
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MISC_OPTIONUTILS_H
diff --git a/clang-tools-extra/clang-tidy/utils/TransformerClangTidyCheck.h b/clang-tools-extra/clang-tidy/utils/TransformerClangTidyCheck.h
--- a/clang-tools-extra/clang-tidy/utils/TransformerClangTidyCheck.h
+++ b/clang-tools-extra/clang-tidy/utils/TransformerClangTidyCheck.h
@@ -16,9 +16,7 @@
 #include "clang/Tooling/Transformer/Transformer.h"
 #include <optional>
 
-namespace clang {
-namespace tidy {
-namespace utils {
+namespace clang::tidy::utils {
 
 /// A base class for defining a ClangTidy check based on a `RewriteRule`.
 //
@@ -83,8 +81,6 @@
   IncludeInserter Inserter;
 };
 
-} // namespace utils
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::utils
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_TRANSFORMER_CLANG_TIDY_CHECK_H
diff --git a/clang-tools-extra/clang-tidy/utils/TypeTraits.h b/clang-tools-extra/clang-tidy/utils/TypeTraits.h
--- a/clang-tools-extra/clang-tidy/utils/TypeTraits.h
+++ b/clang-tools-extra/clang-tidy/utils/TypeTraits.h
@@ -13,10 +13,7 @@
 #include "clang/AST/Type.h"
 #include <optional>
 
-namespace clang {
-namespace tidy {
-namespace utils {
-namespace type_traits {
+namespace clang::tidy::utils::type_traits {
 
 /// Returns `true` if `Type` is expensive to copy.
 std::optional<bool> isExpensiveToCopy(QualType Type, const ASTContext &Context);
@@ -37,9 +34,6 @@
 /// Return true if `Type` has a non-trivial move assignment operator.
 bool hasNonTrivialMoveAssignment(QualType Type);
 
-} // namespace type_traits
-} // namespace utils
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::utils::type_traits
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_UTILS_TYPETRAITS_H
diff --git a/clang-tools-extra/clang-tidy/utils/UsingInserter.h b/clang-tools-extra/clang-tidy/utils/UsingInserter.h
--- a/clang-tools-extra/clang-tidy/utils/UsingInserter.h
+++ b/clang-tools-extra/clang-tidy/utils/UsingInserter.h
@@ -16,9 +16,7 @@
 #include <optional>
 #include <set>
 
-namespace clang {
-namespace tidy {
-namespace utils {
+namespace clang::tidy::utils {
 
 // UsingInserter adds using declarations for |QualifiedName| to the surrounding
 // function.
@@ -44,7 +42,5 @@
   std::set<NameInFunction> AddedUsing;
 };
 
-} // namespace utils
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::utils
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_USINGINSERTER_H
diff --git a/clang-tools-extra/clang-tidy/zircon/TemporaryObjectsCheck.h b/clang-tools-extra/clang-tidy/zircon/TemporaryObjectsCheck.h
--- a/clang-tools-extra/clang-tidy/zircon/TemporaryObjectsCheck.h
+++ b/clang-tools-extra/clang-tidy/zircon/TemporaryObjectsCheck.h
@@ -12,9 +12,7 @@
 #include "../ClangTidyCheck.h"
 #include "../utils/OptionsUtils.h"
 
-namespace clang {
-namespace tidy {
-namespace zircon {
+namespace clang::tidy::zircon {
 
 /// Construction of specific temporary objects in the Zircon kernel is
 /// discouraged.
@@ -34,8 +32,6 @@
   std::vector<StringRef> Names;
 };
 
-} // namespace zircon
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::zircon
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_ZIRCON_TEMPORARYOBJECTSCHECK_H