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
 
-#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_AVOID_BIND_H
+
+} // namespace clang::tidy::modernize#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_AVOID_BIND_H
diff --git a/clang-tools-extra/clang-tidy/modernize/AvoidBindCheck.cpp b/clang-tools-extra/clang-tidy/modernize/AvoidBindCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/AvoidBindCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/AvoidBindCheck.cpp
@@ -28,9 +28,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 namespace {
 
@@ -718,6 +716,4 @@
                                        Stream.str());
 }
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
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 +28,4 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
-
-#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_AVOIDCARRAYSCHECK_H
+} // namespace clang::tidy::modernize#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_AVOIDCARRAYSCHECK_H
diff --git a/clang-tools-extra/clang-tidy/modernize/AvoidCArraysCheck.cpp b/clang-tools-extra/clang-tidy/modernize/AvoidCArraysCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/AvoidCArraysCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/AvoidCArraysCheck.cpp
@@ -38,9 +38,7 @@
 
 } // namespace
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 void AvoidCArraysCheck::registerMatchers(MatchFinder *Finder) {
   Finder->addMatcher(
@@ -66,6 +64,4 @@
        ArrayType->getTypePtr()->isVariableArrayType() ? UseVector : UseArray);
 }
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
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 +34,5 @@
   NamespaceString concatNamespaces();
   NamespaceContextVec Namespaces;
 };
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
 
-#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_CONCATNESTEDNAMESPACESCHECK_H
+} // namespace clang::tidy::modernize#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_CONCATNESTEDNAMESPACESCHECK_H
diff --git a/clang-tools-extra/clang-tidy/modernize/ConcatNestedNamespacesCheck.cpp b/clang-tools-extra/clang-tidy/modernize/ConcatNestedNamespacesCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/ConcatNestedNamespacesCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/ConcatNestedNamespacesCheck.cpp
@@ -12,9 +12,7 @@
 #include <algorithm>
 #include <iterator>
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 static bool locationsInSameFile(const SourceManager &Sources,
                                 SourceLocation Loc1, SourceLocation Loc2) {
@@ -105,6 +103,4 @@
   Namespaces.clear();
 }
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
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.
@@ -43,8 +41,4 @@
                            Preprocessor *ModuleExpanderPP) override;
 };
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
-
-#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_C_HEADERS_TO_CXX_H
+} // 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/DeprecatedHeadersCheck.cpp b/clang-tools-extra/clang-tidy/modernize/DeprecatedHeadersCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/DeprecatedHeadersCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/DeprecatedHeadersCheck.cpp
@@ -15,9 +15,7 @@
 
 #include <vector>
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 namespace {
 class IncludeModernizePPCallbacks : public PPCallbacks {
@@ -117,6 +115,5 @@
   }
 }
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+
+} // namespace clang::tidy::modernize
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 +29,5 @@
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 };
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
 
-#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_DEPRECATEDIOSBASEALIASESCHECK_H
+} // namespace clang::tidy::modernize#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_DEPRECATEDIOSBASEALIASESCHECK_H
diff --git a/clang-tools-extra/clang-tidy/modernize/DeprecatedIosBaseAliasesCheck.cpp b/clang-tools-extra/clang-tidy/modernize/DeprecatedIosBaseAliasesCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/DeprecatedIosBaseAliasesCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/DeprecatedIosBaseAliasesCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 static constexpr std::array<StringRef, 5> DeprecatedTypes = {
     "::std::ios_base::io_state", "::std::ios_base::open_mode",
@@ -71,6 +69,4 @@
     diag(IoStateLoc, "'std::ios_base::%0' is deprecated") << TypeName;
 }
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
diff --git a/clang-tools-extra/clang-tidy/modernize/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
@@ -12,9 +12,7 @@
 #include "../ClangTidyCheck.h"
 #include "LoopConvertUtils.h"
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 class LoopConvertCheck : public ClangTidyCheck {
 public:
@@ -73,8 +71,4 @@
   const VariableNamer::NamingStyle NamingStyle;
 };
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
-
-#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_LOOP_CONVERT_H
+} // namespace clang::tidy::modernize#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_LOOP_CONVERT_H
diff --git a/clang-tools-extra/clang-tidy/modernize/LoopConvertCheck.cpp b/clang-tools-extra/clang-tidy/modernize/LoopConvertCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/LoopConvertCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/LoopConvertCheck.cpp
@@ -26,9 +26,7 @@
 using namespace clang::ast_matchers;
 using namespace llvm;
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 static const char LoopNameArray[] = "forLoopArray";
 static const char LoopNameIterator[] = "forLoopIterator";
@@ -926,6 +924,5 @@
                Finder.aliasFromForInit(), Loop, Descriptor);
 }
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+
+} // namespace clang::tidy::modernize
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, LFK_Iterator, LFK_PseudoArray };
 
@@ -459,8 +457,6 @@
   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/LoopConvertUtils.cpp b/clang-tools-extra/clang-tidy/modernize/LoopConvertUtils.cpp
--- a/clang-tools-extra/clang-tidy/modernize/LoopConvertUtils.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/LoopConvertUtils.cpp
@@ -26,9 +26,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 /// Tracks a stack of parent statements during traversal.
 ///
@@ -903,6 +901,4 @@
   return DeclFinder.findUsages(SourceStmt);
 }
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
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 +33,4 @@
   SmartPtrTypeMatcher getSmartPointerTypeMatcher() const override;
 };
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
-
-#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_MAKE_SHARED_H
+} // namespace clang::tidy::modernize#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_MAKE_SHARED_H
diff --git a/clang-tools-extra/clang-tidy/modernize/MakeSharedCheck.cpp b/clang-tools-extra/clang-tidy/modernize/MakeSharedCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/MakeSharedCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/MakeSharedCheck.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 MakeSharedCheck::MakeSharedCheck(StringRef Name, ClangTidyContext *Context)
     : MakeSmartPtrCheck(Name, Context, "std::make_shared") {}
@@ -29,6 +27,4 @@
                                      qualType().bind(PointerType)))))))));
 }
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
diff --git a/clang-tools-extra/clang-tidy/modernize/MakeSmartPtrCheck.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 +62,5 @@
   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/MakeSmartPtrCheck.cpp b/clang-tools-extra/clang-tidy/modernize/MakeSmartPtrCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/MakeSmartPtrCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/MakeSmartPtrCheck.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 namespace {
 
@@ -439,6 +437,5 @@
       /*IsAngled=*/MakeSmartPtrFunctionHeader == StdMemoryHeader);
 }
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+
+} // namespace clang::tidy::modernize
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 +35,5 @@
   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/MakeUniqueCheck.cpp b/clang-tools-extra/clang-tidy/modernize/MakeUniqueCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/MakeUniqueCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/MakeUniqueCheck.cpp
@@ -10,9 +10,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 MakeUniqueCheck::MakeUniqueCheck(StringRef Name,
                                  clang::tidy::ClangTidyContext *Context)
@@ -43,6 +41,5 @@
 
 // FixItHint is done by MakeSmartPtrCheck
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+
+} // namespace clang::tidy::modernize
\ No newline at end of file
diff --git a/clang-tools-extra/clang-tidy/modernize/ModernizeTidyModule.cpp b/clang-tools-extra/clang-tidy/modernize/ModernizeTidyModule.cpp
--- a/clang-tools-extra/clang-tidy/modernize/ModernizeTidyModule.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/ModernizeTidyModule.cpp
@@ -43,9 +43,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 class ModernizeModule : public ClangTidyModule {
 public:
@@ -122,11 +120,9 @@
 static ClangTidyModuleRegistry::Add<ModernizeModule> X("modernize-module",
                                                        "Add modernize checks.");
 
-} // namespace modernize
-
-// This anchor is used to force the linker to link in the generated object file
+} // namespace clang::tidy::modernize// This anchor is used to force the linker to link in the generated object file
 // and thus register the ModernizeModule.
 volatile int ModernizeModuleAnchorSource = 0;
 
-} // namespace tidy
-} // namespace clang
+
+
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:
@@ -36,8 +34,5 @@
   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/PassByValueCheck.cpp b/clang-tools-extra/clang-tidy/modernize/PassByValueCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/PassByValueCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/PassByValueCheck.cpp
@@ -18,9 +18,7 @@
 using namespace clang::ast_matchers;
 using namespace llvm;
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 namespace {
 /// Matches move-constructible classes.
@@ -224,6 +222,4 @@
               /*IsAngled=*/true);
 }
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
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 +42,5 @@
   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/RawStringLiteralCheck.cpp b/clang-tools-extra/clang-tidy/modernize/RawStringLiteralCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/RawStringLiteralCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/RawStringLiteralCheck.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 namespace {
 
@@ -147,6 +145,4 @@
       << FixItHint::CreateReplacement(CharRange, Replacement);
 }
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
diff --git a/clang-tools-extra/clang-tidy/modernize/RedundantVoidArgCheck.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 +71,5 @@
   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/RedundantVoidArgCheck.cpp b/clang-tools-extra/clang-tidy/modernize/RedundantVoidArgCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/RedundantVoidArgCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/RedundantVoidArgCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 namespace {
 
@@ -245,6 +243,4 @@
   }
 }
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
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
@@ -12,7 +12,7 @@
 #include "../ClangTidyCheck.h"
 #include "../utils/IncludeInserter.h"
 
-namespace clang {
+namespace clang::tidy::modernize {
 namespace tidy {
 namespace modernize {
 
@@ -57,8 +57,5 @@
   const utils::IncludeSorter::IncludeStyle IncludeStyle;
 };
 
-} // 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/ReplaceAutoPtrCheck.cpp b/clang-tools-extra/clang-tidy/modernize/ReplaceAutoPtrCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/ReplaceAutoPtrCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/ReplaceAutoPtrCheck.cpp
@@ -16,9 +16,7 @@
 using namespace clang;
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 namespace {
 static const char AutoPtrTokenId[] = "AutoPrTokenId";
@@ -189,6 +187,4 @@
                                       "unique_ptr");
 }
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
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 +53,5 @@
   const std::string 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/ReplaceDisallowCopyAndAssignMacroCheck.cpp b/clang-tools-extra/clang-tidy/modernize/ReplaceDisallowCopyAndAssignMacroCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/ReplaceDisallowCopyAndAssignMacroCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/ReplaceDisallowCopyAndAssignMacroCheck.cpp
@@ -11,9 +11,7 @@
 #include "clang/Lex/MacroArgs.h"
 #include "llvm/Support/FormatVariadic.h"
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 namespace {
 
@@ -85,6 +83,4 @@
   Options.store(Opts, "MacroName", MacroName);
 }
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
diff --git a/clang-tools-extra/clang-tidy/modernize/ReplaceRandomShuffleCheck.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.
@@ -38,8 +36,5 @@
   const utils::IncludeSorter::IncludeStyle IncludeStyle;
 };
 
-} // 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/ReplaceRandomShuffleCheck.cpp b/clang-tools-extra/clang-tidy/modernize/ReplaceRandomShuffleCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/ReplaceRandomShuffleCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/ReplaceRandomShuffleCheck.cpp
@@ -16,9 +16,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 ReplaceRandomShuffleCheck::ReplaceRandomShuffleCheck(StringRef Name,
                                                      ClangTidyContext *Context)
@@ -100,6 +98,4 @@
       "random", /*IsAngled=*/true);
 }
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
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.
@@ -31,8 +29,5 @@
   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_RETURN_BRACED_INIT_LIST_H
diff --git a/clang-tools-extra/clang-tidy/modernize/ReturnBracedInitListCheck.cpp b/clang-tools-extra/clang-tidy/modernize/ReturnBracedInitListCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/ReturnBracedInitListCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/ReturnBracedInitListCheck.cpp
@@ -14,9 +14,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 void ReturnBracedInitListCheck::registerMatchers(MatchFinder *Finder) {
   // Skip list initialization and constructors with an initializer list.
@@ -89,6 +87,4 @@
        << FixItHint::CreateReplacement(CallParensRange.getEnd(), "}");
 }
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
diff --git a/clang-tools-extra/clang-tidy/modernize/ShrinkToFitCheck.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.
@@ -32,8 +30,5 @@
   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_SHRINKTOFITCHECK_H
diff --git a/clang-tools-extra/clang-tidy/modernize/ShrinkToFitCheck.cpp b/clang-tools-extra/clang-tidy/modernize/ShrinkToFitCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/ShrinkToFitCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/ShrinkToFitCheck.cpp
@@ -14,9 +14,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 void ShrinkToFitCheck::registerMatchers(MatchFinder *Finder) {
   // Swap as a function need not to be considered, because rvalue can not
@@ -82,6 +80,4 @@
       << Hint;
 }
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
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 +29,5 @@
   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/UnaryStaticAssertCheck.cpp b/clang-tools-extra/clang-tidy/modernize/UnaryStaticAssertCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/UnaryStaticAssertCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/UnaryStaticAssertCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 void UnaryStaticAssertCheck::registerMatchers(MatchFinder *Finder) {
   Finder->addMatcher(staticAssertDecl().bind("static_assert"), this);
@@ -36,6 +34,4 @@
       << FixItHint::CreateRemoval(AssertMessage->getSourceRange());
 }
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
diff --git a/clang-tools-extra/clang-tidy/modernize/UseAutoCheck.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 +33,5 @@
   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/UseAutoCheck.cpp b/clang-tools-extra/clang-tidy/modernize/UseAutoCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/UseAutoCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/UseAutoCheck.cpp
@@ -17,9 +17,7 @@
 using namespace clang::ast_matchers;
 using namespace clang::ast_matchers::internal;
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 namespace {
 
 const char IteratorDeclStmtId[] = "iterator_decl";
@@ -494,6 +492,4 @@
   }
 }
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
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 +31,5 @@
   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/UseBoolLiteralsCheck.cpp b/clang-tools-extra/clang-tidy/modernize/UseBoolLiteralsCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/UseBoolLiteralsCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/UseBoolLiteralsCheck.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 UseBoolLiteralsCheck::UseBoolLiteralsCheck(StringRef Name,
                                            ClangTidyContext *Context)
@@ -74,6 +72,4 @@
         Expression->getSourceRange(), LiteralBooleanValue ? "true" : "false");
 }
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
diff --git a/clang-tools-extra/clang-tidy/modernize/UseDefaultMemberInitCheck.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
@@ -41,8 +39,5 @@
   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/UseDefaultMemberInitCheck.cpp b/clang-tools-extra/clang-tidy/modernize/UseDefaultMemberInitCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/UseDefaultMemberInitCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/UseDefaultMemberInitCheck.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 namespace {
 AST_MATCHER_P(InitListExpr, initCountIs, unsigned, N) {
@@ -295,6 +293,4 @@
       << FixItHint::CreateRemoval(Init->getSourceRange());
 }
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
diff --git a/clang-tools-extra/clang-tidy/modernize/UseEmplaceCheck.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.
@@ -42,8 +40,5 @@
   const std::vector<std::string> TupleMakeFunctions;
 };
 
-} // 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/UseEmplaceCheck.cpp b/clang-tools-extra/clang-tidy/modernize/UseEmplaceCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/UseEmplaceCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/UseEmplaceCheck.cpp
@@ -10,9 +10,7 @@
 #include "../utils/OptionsUtils.h"
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 namespace {
 AST_MATCHER(DeclRefExpr, hasExplicitTemplateArgs) {
@@ -171,6 +169,4 @@
                 utils::options::serializeStringList(TupleMakeFunctions));
 }
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
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 +46,5 @@
   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/UseEqualsDefaultCheck.cpp b/clang-tools-extra/clang-tidy/modernize/UseEqualsDefaultCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/UseEqualsDefaultCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/UseEqualsDefaultCheck.cpp
@@ -14,9 +14,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 static const char SpecialFunction[] = "SpecialFunction";
 
@@ -324,6 +322,4 @@
   }
 }
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
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 +48,5 @@
   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/UseEqualsDeleteCheck.cpp b/clang-tools-extra/clang-tidy/modernize/UseEqualsDeleteCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/UseEqualsDeleteCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/UseEqualsDeleteCheck.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 static const char SpecialFunction[] = "SpecialFunction";
 static const char DeletedNotPublic[] = "DeletedNotPublic";
@@ -75,6 +73,4 @@
   }
 }
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
diff --git a/clang-tools-extra/clang-tidy/modernize/UseNodiscardCheck.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 +41,5 @@
   const std::string 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/UseNodiscardCheck.cpp b/clang-tools-extra/clang-tidy/modernize/UseNodiscardCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/UseNodiscardCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/UseNodiscardCheck.cpp
@@ -14,9 +14,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 static bool doesNoDiscardMacroExist(ASTContext &Context,
                                     const llvm::StringRef &MacroId) {
@@ -146,6 +144,4 @@
   return LangOpts.CPlusPlus;
 }
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
diff --git a/clang-tools-extra/clang-tidy/modernize/UseNoexceptCheck.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 +42,5 @@
   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/UseNoexceptCheck.cpp b/clang-tools-extra/clang-tidy/modernize/UseNoexceptCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/UseNoexceptCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/UseNoexceptCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 namespace {
 AST_MATCHER(NamedDecl, isValid) { return !Node.isInvalidDecl(); }
@@ -104,6 +102,4 @@
       << ReplacementStr.empty() << ReplacementStr << FixIt;
 }
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
diff --git a/clang-tools-extra/clang-tidy/modernize/UseNullptrCheck.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 +30,5 @@
   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/UseNullptrCheck.cpp b/clang-tools-extra/clang-tidy/modernize/UseNullptrCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/UseNullptrCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/UseNullptrCheck.cpp
@@ -16,9 +16,7 @@
 using namespace clang::ast_matchers;
 using namespace llvm;
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 namespace {
 
 const char CastSequence[] = "sequence";
@@ -489,6 +487,4 @@
       .TraverseStmt(const_cast<CastExpr *>(NullCast));
 }
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
diff --git a/clang-tools-extra/clang-tidy/modernize/UseOverrideCheck.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 +32,5 @@
   const std::string 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/UseOverrideCheck.cpp b/clang-tools-extra/clang-tidy/modernize/UseOverrideCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/UseOverrideCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/UseOverrideCheck.cpp
@@ -13,9 +13,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 UseOverrideCheck::UseOverrideCheck(StringRef Name, ClangTidyContext *Context)
     : ClangTidyCheck(Name, Context),
@@ -228,6 +226,4 @@
   }
 }
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
diff --git a/clang-tools-extra/clang-tidy/modernize/UseTrailingReturnTypeCheck.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
@@ -12,9 +12,7 @@
 
 #include "../ClangTidy.h"
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 struct ClassifiedToken {
   Token T;
@@ -58,8 +56,5 @@
                       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/UseTrailingReturnTypeCheck.cpp b/clang-tools-extra/clang-tidy/modernize/UseTrailingReturnTypeCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/UseTrailingReturnTypeCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/UseTrailingReturnTypeCheck.cpp
@@ -18,9 +18,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 namespace {
 struct UnqualNameVisitor : public RecursiveASTVisitor<UnqualNameVisitor> {
 public:
@@ -473,6 +471,4 @@
       << FixItHint::CreateInsertion(InsertionLoc, " -> " + ReturnType);
 }
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
diff --git a/clang-tools-extra/clang-tidy/modernize/UseTransparentFunctorsCheck.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 +30,5 @@
   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/UseTransparentFunctorsCheck.cpp b/clang-tools-extra/clang-tidy/modernize/UseTransparentFunctorsCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/UseTransparentFunctorsCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/UseTransparentFunctorsCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 UseTransparentFunctorsCheck::UseTransparentFunctorsCheck(
     StringRef Name, ClangTidyContext *Context)
@@ -124,6 +122,4 @@
                                   FunctorTypeLoc.getArgLoc(0).getSourceRange());
 }
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
diff --git a/clang-tools-extra/clang-tidy/modernize/UseUncaughtExceptionsCheck.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 +30,5 @@
   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/UseUncaughtExceptionsCheck.cpp b/clang-tools-extra/clang-tidy/modernize/UseUncaughtExceptionsCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/UseUncaughtExceptionsCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/UseUncaughtExceptionsCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 void UseUncaughtExceptionsCheck::registerMatchers(MatchFinder *Finder) {
   std::string MatchText = "::std::uncaught_exception";
@@ -96,6 +94,4 @@
   }
 }
 
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+} // namespace clang::tidy::modernize
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.
 ///
@@ -37,8 +35,5 @@
   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/modernize/UseUsingCheck.cpp b/clang-tools-extra/clang-tidy/modernize/UseUsingCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/UseUsingCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/UseUsingCheck.cpp
@@ -12,9 +12,7 @@
 
 using namespace clang::ast_matchers;
 
-namespace clang {
-namespace tidy {
-namespace modernize {
+namespace clang::tidy::modernize {
 
 UseUsingCheck::UseUsingCheck(StringRef Name, ClangTidyContext *Context)
     : ClangTidyCheck(Name, Context),
@@ -115,6 +113,5 @@
   std::string Replacement = Using + Name + " = " + Type;
   Diag << FixItHint::CreateReplacement(ReplaceRange, Replacement);
 }
-} // namespace modernize
-} // namespace tidy
-} // namespace clang
+
+} // namespace clang::tidy::modernize
diff --git a/clang/lib/Analysis/Consumed.cpp b/clang/lib/Analysis/Consumed.cpp
--- a/clang/lib/Analysis/Consumed.cpp
+++ b/clang/lib/Analysis/Consumed.cpp
@@ -282,8 +282,7 @@
 
 } // namespace
 
-namespace clang {
-namespace consumed {
+namespace clang::consumed {
 
 enum EffectiveOp {
   EO_And,
@@ -439,8 +438,7 @@
   }
 };
 
-} // namespace consumed
-} // namespace clang
+} // namespace clang::consumed
 
 static void
 setStateForVarOrTmp(ConsumedStateMap *StateMap, const PropagationInfo &PInfo,
@@ -453,8 +451,7 @@
     StateMap->setState(PInfo.getTmp(), State);
 }
 
-namespace clang {
-namespace consumed {
+namespace clang::consumed {
 
 class ConsumedStmtVisitor : public ConstStmtVisitor<ConsumedStmtVisitor> {
   using MapType = llvm::DenseMap<const Stmt *, PropagationInfo>;
@@ -530,8 +527,7 @@
   }
 };
 
-} // namespace consumed
-} // namespace clang
+} // namespace clang::consumed
 
 void ConsumedStmtVisitor::forwardInfo(const Expr *From, const Expr *To) {
   InfoEntry Entry = findInfo(From);
diff --git a/clang/lib/Analysis/ReachableCode.cpp b/clang/lib/Analysis/ReachableCode.cpp
--- a/clang/lib/Analysis/ReachableCode.cpp
+++ b/clang/lib/Analysis/ReachableCode.cpp
@@ -667,7 +667,7 @@
 // Reachability APIs.
 //===----------------------------------------------------------------------===//
 
-namespace clang { namespace reachable_code {
+namespace clang::reachable_code {
 
 void Callback::anchor() { }
 
@@ -718,4 +718,4 @@
   }
 }
 
-}} // end namespace clang::reachable_code
+}// end namespace clang::reachable_code
diff --git a/clang/lib/Analysis/ThreadSafety.cpp b/clang/lib/Analysis/ThreadSafety.cpp
--- a/clang/lib/Analysis/ThreadSafety.cpp
+++ b/clang/lib/Analysis/ThreadSafety.cpp
@@ -269,8 +269,7 @@
 
 } // namespace
 
-namespace clang {
-namespace threadSafety {
+namespace clang::threadSafety {
 
 class BeforeSet {
 private:
@@ -306,9 +305,7 @@
   BeforeMap BMap;
   CycleMap CycMap;
 };
-
-} // namespace threadSafety
-} // namespace clang
+} // namespace clang::threadSafety
 
 namespace {
 
diff --git a/clang/lib/Analysis/ThreadSafetyCommon.cpp b/clang/lib/Analysis/ThreadSafetyCommon.cpp
--- a/clang/lib/Analysis/ThreadSafetyCommon.cpp
+++ b/clang/lib/Analysis/ThreadSafetyCommon.cpp
@@ -957,8 +957,7 @@
 
 } // namespace
 
-namespace clang {
-namespace threadSafety {
+namespace clang::threadSafety {
 
 void printSCFG(CFGWalker &Walker) {
   llvm::BumpPtrAllocator Bpa;
@@ -968,6 +967,5 @@
   TILPrinter::print(Scfg, llvm::errs());
 }
 
-} // namespace threadSafety
-} // namespace clang
+} // namespace clang::threadSafety
 */
diff --git a/clang/lib/Analysis/ThreadSafetyLogical.cpp b/clang/lib/Analysis/ThreadSafetyLogical.cpp
--- a/clang/lib/Analysis/ThreadSafetyLogical.cpp
+++ b/clang/lib/Analysis/ThreadSafetyLogical.cpp
@@ -98,14 +98,10 @@
   return cast<Terminal>(LHS)->expr() == cast<Terminal>(RHS)->expr();
 }
 
-namespace clang {
-namespace threadSafety {
-namespace lexpr {
+namespace clang::threadSafety::lexpr {
 
 bool implies(const LExpr *LHS, const LExpr *RHS) {
   // Start out by assuming that LHS and RHS are not negated.
   return ::implies(LHS, false, RHS, false);
 }
 }
-}
-}