diff --git a/clang-tools-extra/clang-apply-replacements/lib/Tooling/ApplyReplacements.cpp b/clang-tools-extra/clang-apply-replacements/lib/Tooling/ApplyReplacements.cpp
index b9e83aca0ab96e..43ecfd8f0ccce2 100644
--- a/clang-tools-extra/clang-apply-replacements/lib/Tooling/ApplyReplacements.cpp
+++ b/clang-tools-extra/clang-apply-replacements/lib/Tooling/ApplyReplacements.cpp
@@ -29,6 +29,7 @@
 #include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/Path.h"
 #include "llvm/Support/raw_ostream.h"
+#include <optional>
 
 using namespace llvm;
 using namespace clang;
diff --git a/clang-tools-extra/clang-doc/HTMLGenerator.cpp b/clang-tools-extra/clang-doc/HTMLGenerator.cpp
index 37598c43e95728..589a3232c90c99 100644
--- a/clang-tools-extra/clang-doc/HTMLGenerator.cpp
+++ b/clang-tools-extra/clang-doc/HTMLGenerator.cpp
@@ -16,6 +16,7 @@
 #include "llvm/Support/JSON.h"
 #include "llvm/Support/Path.h"
 #include "llvm/Support/raw_ostream.h"
+#include <optional>
 #include <string>
 
 using namespace llvm;
diff --git a/clang-tools-extra/clang-include-fixer/find-all-symbols/FindAllMacros.cpp b/clang-tools-extra/clang-include-fixer/find-all-symbols/FindAllMacros.cpp
index f41d478293b904..2cee43845aaa03 100644
--- a/clang-tools-extra/clang-include-fixer/find-all-symbols/FindAllMacros.cpp
+++ b/clang-tools-extra/clang-include-fixer/find-all-symbols/FindAllMacros.cpp
@@ -16,6 +16,7 @@
 #include "clang/Lex/MacroInfo.h"
 #include "clang/Lex/Token.h"
 #include "llvm/Support/Path.h"
+#include <optional>
 
 namespace clang {
 namespace find_all_symbols {
diff --git a/clang-tools-extra/clang-include-fixer/find-all-symbols/FindAllMacros.h b/clang-tools-extra/clang-include-fixer/find-all-symbols/FindAllMacros.h
index 0a51ab192e8de7..99a7f5deccdcf6 100644
--- a/clang-tools-extra/clang-include-fixer/find-all-symbols/FindAllMacros.h
+++ b/clang-tools-extra/clang-include-fixer/find-all-symbols/FindAllMacros.h
@@ -13,6 +13,7 @@
 #include "SymbolInfo.h"
 #include "SymbolReporter.h"
 #include "clang/Lex/PPCallbacks.h"
+#include <optional>
 
 namespace clang {
 class MacroInfo;
diff --git a/clang-tools-extra/clang-include-fixer/find-all-symbols/FindAllSymbols.cpp b/clang-tools-extra/clang-include-fixer/find-all-symbols/FindAllSymbols.cpp
index ccfdb9332c443a..8608ba74ce9f48 100644
--- a/clang-tools-extra/clang-include-fixer/find-all-symbols/FindAllSymbols.cpp
+++ b/clang-tools-extra/clang-include-fixer/find-all-symbols/FindAllSymbols.cpp
@@ -18,6 +18,7 @@
 #include "clang/Tooling/Tooling.h"
 #include "llvm/ADT/Optional.h"
 #include "llvm/Support/FileSystem.h"
+#include <optional>
 
 using namespace clang::ast_matchers;
 
diff --git a/clang-tools-extra/clang-query/Query.cpp b/clang-tools-extra/clang-query/Query.cpp
index 4d62f37231b756..d1db851c129714 100644
--- a/clang-tools-extra/clang-query/Query.cpp
+++ b/clang-tools-extra/clang-query/Query.cpp
@@ -14,6 +14,7 @@
 #include "clang/Frontend/TextDiagnostic.h"
 #include "clang/Tooling/NodeIntrospection.h"
 #include "llvm/Support/raw_ostream.h"
+#include <optional>
 
 using namespace clang::ast_matchers;
 using namespace clang::ast_matchers::dynamic;
diff --git a/clang-tools-extra/clang-query/QueryParser.cpp b/clang-tools-extra/clang-query/QueryParser.cpp
index b80ad04726bcd2..77621d252aeda1 100644
--- a/clang-tools-extra/clang-query/QueryParser.cpp
+++ b/clang-tools-extra/clang-query/QueryParser.cpp
@@ -14,6 +14,7 @@
 #include "clang/Tooling/NodeIntrospection.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/ADT/StringSwitch.h"
+#include <optional>
 #include <set>
 
 using namespace llvm;
diff --git a/clang-tools-extra/clang-query/tool/ClangQuery.cpp b/clang-tools-extra/clang-query/tool/ClangQuery.cpp
index 2bdb36192f350e..6ba2b1a4412da4 100644
--- a/clang-tools-extra/clang-query/tool/ClangQuery.cpp
+++ b/clang-tools-extra/clang-query/tool/ClangQuery.cpp
@@ -37,6 +37,7 @@
 #include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/Signals.h"
 #include "llvm/Support/WithColor.h"
+#include <optional>
 #include <string>
 
 using namespace clang;
diff --git a/clang-tools-extra/clang-tidy/ClangTidyCheck.cpp b/clang-tools-extra/clang-tidy/ClangTidyCheck.cpp
index fedf3aa27169c1..8f90becf8ab2d8 100644
--- a/clang-tools-extra/clang-tidy/ClangTidyCheck.cpp
+++ b/clang-tools-extra/clang-tidy/ClangTidyCheck.cpp
@@ -11,6 +11,7 @@
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Support/Error.h"
 #include "llvm/Support/YAMLParser.h"
+#include <optional>
 
 namespace clang {
 namespace tidy {
diff --git a/clang-tools-extra/clang-tidy/ClangTidyCheck.h b/clang-tools-extra/clang-tidy/ClangTidyCheck.h
index e5d98b0196f58f..f2486eab5dfaa3 100644
--- a/clang-tools-extra/clang-tidy/ClangTidyCheck.h
+++ b/clang-tools-extra/clang-tidy/ClangTidyCheck.h
@@ -14,6 +14,7 @@
 #include "clang/ASTMatchers/ASTMatchFinder.h"
 #include "clang/Basic/Diagnostic.h"
 #include "llvm/ADT/Optional.h"
+#include <optional>
 #include <type_traits>
 #include <utility>
 #include <vector>
diff --git a/clang-tools-extra/clang-tidy/ClangTidyDiagnosticConsumer.cpp b/clang-tools-extra/clang-tidy/ClangTidyDiagnosticConsumer.cpp
index e6b907038a7e15..05ca2573dc4ea2 100644
--- a/clang-tools-extra/clang-tidy/ClangTidyDiagnosticConsumer.cpp
+++ b/clang-tools-extra/clang-tidy/ClangTidyDiagnosticConsumer.cpp
@@ -36,6 +36,7 @@
 #include "llvm/ADT/StringMap.h"
 #include "llvm/Support/FormatVariadic.h"
 #include "llvm/Support/Regex.h"
+#include <optional>
 #include <tuple>
 #include <utility>
 #include <vector>
diff --git a/clang-tools-extra/clang-tidy/ClangTidyDiagnosticConsumer.h b/clang-tools-extra/clang-tidy/ClangTidyDiagnosticConsumer.h
index 261e4f7ac8626a..475f38d334caf1 100644
--- a/clang-tools-extra/clang-tidy/ClangTidyDiagnosticConsumer.h
+++ b/clang-tools-extra/clang-tidy/ClangTidyDiagnosticConsumer.h
@@ -17,6 +17,7 @@
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/StringSet.h"
 #include "llvm/Support/Regex.h"
+#include <optional>
 
 namespace clang {
 
diff --git a/clang-tools-extra/clang-tidy/ExpandModularHeadersPPCallbacks.cpp b/clang-tools-extra/clang-tidy/ExpandModularHeadersPPCallbacks.cpp
index 9df26411060c1a..0cfdda3b5dedd2 100644
--- a/clang-tools-extra/clang-tidy/ExpandModularHeadersPPCallbacks.cpp
+++ b/clang-tools-extra/clang-tidy/ExpandModularHeadersPPCallbacks.cpp
@@ -12,6 +12,7 @@
 #include "clang/Frontend/CompilerInstance.h"
 #include "clang/Lex/PreprocessorOptions.h"
 #include "clang/Serialization/ASTReader.h"
+#include <optional>
 
 #define DEBUG_TYPE "clang-tidy"
 
diff --git a/clang-tools-extra/clang-tidy/NoLintDirectiveHandler.cpp b/clang-tools-extra/clang-tidy/NoLintDirectiveHandler.cpp
index 08d837c105c815..7a822cd55bed4c 100644
--- a/clang-tools-extra/clang-tidy/NoLintDirectiveHandler.cpp
+++ b/clang-tools-extra/clang-tidy/NoLintDirectiveHandler.cpp
@@ -28,6 +28,7 @@
 #include <cassert>
 #include <cstddef>
 #include <iterator>
+#include <optional>
 #include <string>
 #include <tuple>
 #include <type_traits>
diff --git a/clang-tools-extra/clang-tidy/abseil/DurationAdditionCheck.cpp b/clang-tools-extra/clang-tidy/abseil/DurationAdditionCheck.cpp
index 60047096e534b1..585b7c1310e263 100644
--- a/clang-tools-extra/clang-tidy/abseil/DurationAdditionCheck.cpp
+++ b/clang-tools-extra/clang-tidy/abseil/DurationAdditionCheck.cpp
@@ -11,6 +11,7 @@
 #include "clang/AST/ASTContext.h"
 #include "clang/ASTMatchers/ASTMatchFinder.h"
 #include "clang/Tooling/FixIt.h"
+#include <optional>
 
 using namespace clang::ast_matchers;
 
diff --git a/clang-tools-extra/clang-tidy/abseil/DurationComparisonCheck.cpp b/clang-tools-extra/clang-tidy/abseil/DurationComparisonCheck.cpp
index a6e12dd8966b85..39c7ba4fc9b4ab 100644
--- a/clang-tools-extra/clang-tidy/abseil/DurationComparisonCheck.cpp
+++ b/clang-tools-extra/clang-tidy/abseil/DurationComparisonCheck.cpp
@@ -11,6 +11,7 @@
 #include "clang/AST/ASTContext.h"
 #include "clang/ASTMatchers/ASTMatchFinder.h"
 #include "clang/Tooling/FixIt.h"
+#include <optional>
 
 using namespace clang::ast_matchers;
 
diff --git a/clang-tools-extra/clang-tidy/abseil/DurationConversionCastCheck.cpp b/clang-tools-extra/clang-tidy/abseil/DurationConversionCastCheck.cpp
index d3007d79f3766c..3a83e6707efc13 100644
--- a/clang-tools-extra/clang-tidy/abseil/DurationConversionCastCheck.cpp
+++ b/clang-tools-extra/clang-tidy/abseil/DurationConversionCastCheck.cpp
@@ -11,6 +11,7 @@
 #include "clang/AST/ASTContext.h"
 #include "clang/ASTMatchers/ASTMatchFinder.h"
 #include "clang/Tooling/FixIt.h"
+#include <optional>
 
 using namespace clang::ast_matchers;
 
diff --git a/clang-tools-extra/clang-tidy/abseil/DurationFactoryFloatCheck.cpp b/clang-tools-extra/clang-tidy/abseil/DurationFactoryFloatCheck.cpp
index 4b0ef1b3f4ee09..09512347accab3 100644
--- a/clang-tools-extra/clang-tidy/abseil/DurationFactoryFloatCheck.cpp
+++ b/clang-tools-extra/clang-tidy/abseil/DurationFactoryFloatCheck.cpp
@@ -12,6 +12,7 @@
 #include "clang/ASTMatchers/ASTMatchFinder.h"
 #include "clang/Lex/Lexer.h"
 #include "clang/Tooling/FixIt.h"
+#include <optional>
 
 using namespace clang::ast_matchers;
 
diff --git a/clang-tools-extra/clang-tidy/abseil/DurationFactoryScaleCheck.cpp b/clang-tools-extra/clang-tidy/abseil/DurationFactoryScaleCheck.cpp
index ba7dc70b2f606c..b33f1e364a6699 100644
--- a/clang-tools-extra/clang-tidy/abseil/DurationFactoryScaleCheck.cpp
+++ b/clang-tools-extra/clang-tidy/abseil/DurationFactoryScaleCheck.cpp
@@ -11,6 +11,7 @@
 #include "clang/AST/ASTContext.h"
 #include "clang/ASTMatchers/ASTMatchFinder.h"
 #include "clang/Tooling/FixIt.h"
+#include <optional>
 
 using namespace clang::ast_matchers;
 
diff --git a/clang-tools-extra/clang-tidy/abseil/DurationRewriter.cpp b/clang-tools-extra/clang-tidy/abseil/DurationRewriter.cpp
index 43f8ed709651b2..c2325c11e2adc2 100644
--- a/clang-tools-extra/clang-tidy/abseil/DurationRewriter.cpp
+++ b/clang-tools-extra/clang-tidy/abseil/DurationRewriter.cpp
@@ -7,6 +7,7 @@
 //===----------------------------------------------------------------------===//
 
 #include <cmath>
+#include <optional>
 
 #include "DurationRewriter.h"
 #include "clang/Tooling/FixIt.h"
diff --git a/clang-tools-extra/clang-tidy/abseil/DurationRewriter.h b/clang-tools-extra/clang-tidy/abseil/DurationRewriter.h
index d8b0acf63cfd50..a23dfaf9bcef41 100644
--- a/clang-tools-extra/clang-tidy/abseil/DurationRewriter.h
+++ b/clang-tools-extra/clang-tidy/abseil/DurationRewriter.h
@@ -12,6 +12,7 @@
 #include "clang/ASTMatchers/ASTMatchFinder.h"
 #include "clang/ASTMatchers/ASTMatchers.h"
 #include <cinttypes>
+#include <optional>
 
 namespace clang {
 namespace tidy {
diff --git a/clang-tools-extra/clang-tidy/abseil/DurationSubtractionCheck.cpp b/clang-tools-extra/clang-tidy/abseil/DurationSubtractionCheck.cpp
index 322171444e6da5..4d12fd337ace52 100644
--- a/clang-tools-extra/clang-tidy/abseil/DurationSubtractionCheck.cpp
+++ b/clang-tools-extra/clang-tidy/abseil/DurationSubtractionCheck.cpp
@@ -11,6 +11,7 @@
 #include "clang/AST/ASTContext.h"
 #include "clang/ASTMatchers/ASTMatchFinder.h"
 #include "clang/Tooling/FixIt.h"
+#include <optional>
 
 using namespace clang::ast_matchers;
 
diff --git a/clang-tools-extra/clang-tidy/abseil/FasterStrsplitDelimiterCheck.cpp b/clang-tools-extra/clang-tidy/abseil/FasterStrsplitDelimiterCheck.cpp
index b73b1002763c5d..36e670ea8c36d3 100644
--- a/clang-tools-extra/clang-tidy/abseil/FasterStrsplitDelimiterCheck.cpp
+++ b/clang-tools-extra/clang-tidy/abseil/FasterStrsplitDelimiterCheck.cpp
@@ -10,6 +10,7 @@
 #include "clang/AST/ASTContext.h"
 #include "clang/ASTMatchers/ASTMatchFinder.h"
 #include "clang/Tooling/FixIt.h"
+#include <optional>
 
 using namespace clang::ast_matchers;
 
diff --git a/clang-tools-extra/clang-tidy/abseil/TimeComparisonCheck.cpp b/clang-tools-extra/clang-tidy/abseil/TimeComparisonCheck.cpp
index 391f38f165c38d..ddbde758684f32 100644
--- a/clang-tools-extra/clang-tidy/abseil/TimeComparisonCheck.cpp
+++ b/clang-tools-extra/clang-tidy/abseil/TimeComparisonCheck.cpp
@@ -12,6 +12,7 @@
 #include "clang/AST/ASTContext.h"
 #include "clang/ASTMatchers/ASTMatchFinder.h"
 #include "clang/Tooling/FixIt.h"
+#include <optional>
 
 using namespace clang::ast_matchers;
 
diff --git a/clang-tools-extra/clang-tidy/abseil/TimeSubtractionCheck.cpp b/clang-tools-extra/clang-tidy/abseil/TimeSubtractionCheck.cpp
index 58ce1f4be622ed..9f2fba454cbdd2 100644
--- a/clang-tools-extra/clang-tidy/abseil/TimeSubtractionCheck.cpp
+++ b/clang-tools-extra/clang-tidy/abseil/TimeSubtractionCheck.cpp
@@ -12,6 +12,7 @@
 #include "clang/ASTMatchers/ASTMatchFinder.h"
 #include "clang/Lex/Lexer.h"
 #include "clang/Tooling/FixIt.h"
+#include <optional>
 
 using namespace clang::ast_matchers;
 
diff --git a/clang-tools-extra/clang-tidy/bugprone/BadSignalToKillThreadCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/BadSignalToKillThreadCheck.cpp
index f1bfcc84c95f59..2676540ab2c584 100644
--- a/clang-tools-extra/clang-tidy/bugprone/BadSignalToKillThreadCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/BadSignalToKillThreadCheck.cpp
@@ -10,6 +10,7 @@
 #include "clang/AST/ASTContext.h"
 #include "clang/ASTMatchers/ASTMatchFinder.h"
 #include "clang/Lex/Preprocessor.h"
+#include <optional>
 
 using namespace clang::ast_matchers;
 
diff --git a/clang-tools-extra/clang-tidy/bugprone/BadSignalToKillThreadCheck.h b/clang-tools-extra/clang-tidy/bugprone/BadSignalToKillThreadCheck.h
index 6276179d76a07c..3a5919d5121a16 100644
--- a/clang-tools-extra/clang-tidy/bugprone/BadSignalToKillThreadCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/BadSignalToKillThreadCheck.h
@@ -10,6 +10,7 @@
 #define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_BADSIGNALTOKILLTHREADCHECK_H
 
 #include "../ClangTidyCheck.h"
+#include <optional>
 
 namespace clang {
 namespace tidy {
diff --git a/clang-tools-extra/clang-tidy/bugprone/EasilySwappableParametersCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/EasilySwappableParametersCheck.cpp
index f1b78883aece70..23244dceefdabe 100644
--- a/clang-tools-extra/clang-tidy/bugprone/EasilySwappableParametersCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/EasilySwappableParametersCheck.cpp
@@ -16,6 +16,7 @@
 
 #define DEBUG_TYPE "EasilySwappableParametersCheck"
 #include "llvm/Support/Debug.h"
+#include <optional>
 
 namespace optutils = clang::tidy::utils::options;
 
diff --git a/clang-tools-extra/clang-tidy/bugprone/ImplicitWideningOfMultiplicationResultCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/ImplicitWideningOfMultiplicationResultCheck.cpp
index fbf3438889efdb..601949bfb16a8b 100644
--- a/clang-tools-extra/clang-tidy/bugprone/ImplicitWideningOfMultiplicationResultCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/ImplicitWideningOfMultiplicationResultCheck.cpp
@@ -9,6 +9,7 @@
 #include "ImplicitWideningOfMultiplicationResultCheck.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/ASTMatchers/ASTMatchFinder.h"
+#include <optional>
 
 using namespace clang::ast_matchers;
 
diff --git a/clang-tools-extra/clang-tidy/bugprone/ImplicitWideningOfMultiplicationResultCheck.h b/clang-tools-extra/clang-tidy/bugprone/ImplicitWideningOfMultiplicationResultCheck.h
index 19c364d9278533..74152efa473662 100644
--- a/clang-tools-extra/clang-tidy/bugprone/ImplicitWideningOfMultiplicationResultCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/ImplicitWideningOfMultiplicationResultCheck.h
@@ -11,6 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 #include "../utils/IncludeInserter.h"
+#include <optional>
 
 namespace clang {
 namespace tidy {
diff --git a/clang-tools-extra/clang-tidy/bugprone/NotNullTerminatedResultCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/NotNullTerminatedResultCheck.cpp
index 17537f1d1f8674..ce58f1e50f0e93 100644
--- a/clang-tools-extra/clang-tidy/bugprone/NotNullTerminatedResultCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/NotNullTerminatedResultCheck.cpp
@@ -13,6 +13,7 @@
 #include "clang/Lex/Lexer.h"
 #include "clang/Lex/PPCallbacks.h"
 #include "clang/Lex/Preprocessor.h"
+#include <optional>
 
 using namespace clang::ast_matchers;
 
diff --git a/clang-tools-extra/clang-tidy/bugprone/ReservedIdentifierCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/ReservedIdentifierCheck.cpp
index 71c7daaf7c1eea..560e9a157b467f 100644
--- a/clang-tools-extra/clang-tidy/bugprone/ReservedIdentifierCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/ReservedIdentifierCheck.cpp
@@ -14,6 +14,7 @@
 #include "clang/Lex/Token.h"
 #include <algorithm>
 #include <cctype>
+#include <optional>
 
 // FixItHint
 
diff --git a/clang-tools-extra/clang-tidy/bugprone/ReservedIdentifierCheck.h b/clang-tools-extra/clang-tidy/bugprone/ReservedIdentifierCheck.h
index 0769fcea5f239b..99c1dbe3363eb9 100644
--- a/clang-tools-extra/clang-tidy/bugprone/ReservedIdentifierCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/ReservedIdentifierCheck.h
@@ -11,6 +11,7 @@
 
 #include "../utils/RenamerClangTidyCheck.h"
 #include "llvm/ADT/Optional.h"
+#include <optional>
 #include <string>
 #include <vector>
 
diff --git a/clang-tools-extra/clang-tidy/bugprone/SuspiciousIncludeCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/SuspiciousIncludeCheck.cpp
index cd9aa00079e126..177882777f07d0 100644
--- a/clang-tools-extra/clang-tidy/bugprone/SuspiciousIncludeCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/SuspiciousIncludeCheck.cpp
@@ -9,6 +9,7 @@
 #include "SuspiciousIncludeCheck.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/Lex/Preprocessor.h"
+#include <optional>
 
 namespace clang {
 namespace tidy {
diff --git a/clang-tools-extra/clang-tidy/bugprone/SuspiciousMemoryComparisonCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/SuspiciousMemoryComparisonCheck.cpp
index d731d7d169620e..a1d04dc966adb5 100644
--- a/clang-tools-extra/clang-tidy/bugprone/SuspiciousMemoryComparisonCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/SuspiciousMemoryComparisonCheck.cpp
@@ -9,6 +9,7 @@
 #include "SuspiciousMemoryComparisonCheck.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/ASTMatchers/ASTMatchFinder.h"
+#include <optional>
 
 using namespace clang::ast_matchers;
 
diff --git a/clang-tools-extra/clang-tidy/bugprone/UncheckedOptionalAccessCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/UncheckedOptionalAccessCheck.cpp
index ccf9365940191e..89d39d2898160e 100644
--- a/clang-tools-extra/clang-tidy/bugprone/UncheckedOptionalAccessCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/UncheckedOptionalAccessCheck.cpp
@@ -22,6 +22,7 @@
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/Support/Error.h"
 #include <memory>
+#include <optional>
 #include <vector>
 
 namespace clang {
diff --git a/clang-tools-extra/clang-tidy/bugprone/UncheckedOptionalAccessCheck.h b/clang-tools-extra/clang-tidy/bugprone/UncheckedOptionalAccessCheck.h
index ae583fd0e940f9..052d6c6d5a6c49 100644
--- a/clang-tools-extra/clang-tidy/bugprone/UncheckedOptionalAccessCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/UncheckedOptionalAccessCheck.h
@@ -12,6 +12,7 @@
 #include "../ClangTidyCheck.h"
 #include "clang/ASTMatchers/ASTMatchFinder.h"
 #include "clang/Analysis/FlowSensitive/Models/UncheckedOptionalAccessModel.h"
+#include <optional>
 
 namespace clang {
 namespace tidy {
diff --git a/clang-tools-extra/clang-tidy/bugprone/UseAfterMoveCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/UseAfterMoveCheck.cpp
index d2a0dd66d32391..6c4fa9c55609e9 100644
--- a/clang-tools-extra/clang-tidy/bugprone/UseAfterMoveCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/UseAfterMoveCheck.cpp
@@ -17,6 +17,7 @@
 #include "llvm/ADT/STLExtras.h"
 
 #include "../utils/ExprSequence.h"
+#include <optional>
 
 using namespace clang::ast_matchers;
 using namespace clang::tidy::utils;
diff --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/InitVariablesCheck.cpp b/clang-tools-extra/clang-tidy/cppcoreguidelines/InitVariablesCheck.cpp
index e54a4f35fd11ba..d75990823ce5f8 100644
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/InitVariablesCheck.cpp
+++ b/clang-tools-extra/clang-tidy/cppcoreguidelines/InitVariablesCheck.cpp
@@ -12,6 +12,7 @@
 #include "clang/ASTMatchers/ASTMatchFinder.h"
 #include "clang/Lex/PPCallbacks.h"
 #include "clang/Lex/Preprocessor.h"
+#include <optional>
 
 using namespace clang::ast_matchers;
 
diff --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/ProBoundsConstantArrayIndexCheck.cpp b/clang-tools-extra/clang-tidy/cppcoreguidelines/ProBoundsConstantArrayIndexCheck.cpp
index c80be3df1ce621..6692baca99d532 100644
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/ProBoundsConstantArrayIndexCheck.cpp
+++ b/clang-tools-extra/clang-tidy/cppcoreguidelines/ProBoundsConstantArrayIndexCheck.cpp
@@ -11,6 +11,7 @@
 #include "clang/ASTMatchers/ASTMatchFinder.h"
 #include "clang/Frontend/CompilerInstance.h"
 #include "clang/Lex/Preprocessor.h"
+#include <optional>
 
 using namespace clang::ast_matchers;
 
diff --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/VirtualClassDestructorCheck.cpp b/clang-tools-extra/clang-tidy/cppcoreguidelines/VirtualClassDestructorCheck.cpp
index 2eb6e40d98638f..234ddd4ae93642 100644
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/VirtualClassDestructorCheck.cpp
+++ b/clang-tools-extra/clang-tidy/cppcoreguidelines/VirtualClassDestructorCheck.cpp
@@ -11,6 +11,7 @@
 #include "clang/AST/ASTContext.h"
 #include "clang/ASTMatchers/ASTMatchFinder.h"
 #include "clang/Lex/Lexer.h"
+#include <optional>
 #include <string>
 
 using namespace clang::ast_matchers;
diff --git a/clang-tools-extra/clang-tidy/google/UpgradeGoogletestCaseCheck.cpp b/clang-tools-extra/clang-tidy/google/UpgradeGoogletestCaseCheck.cpp
index f5ab332ff46a66..1055d26e534ca4 100644
--- a/clang-tools-extra/clang-tidy/google/UpgradeGoogletestCaseCheck.cpp
+++ b/clang-tools-extra/clang-tidy/google/UpgradeGoogletestCaseCheck.cpp
@@ -11,6 +11,7 @@
 #include "clang/ASTMatchers/ASTMatchFinder.h"
 #include "clang/Lex/PPCallbacks.h"
 #include "clang/Lex/Preprocessor.h"
+#include <optional>
 
 using namespace clang::ast_matchers;
 
diff --git a/clang-tools-extra/clang-tidy/misc/RedundantExpressionCheck.cpp b/clang-tools-extra/clang-tidy/misc/RedundantExpressionCheck.cpp
index e7c79331757a03..7c3811ceb4da9e 100644
--- a/clang-tools-extra/clang-tidy/misc/RedundantExpressionCheck.cpp
+++ b/clang-tools-extra/clang-tidy/misc/RedundantExpressionCheck.cpp
@@ -25,6 +25,7 @@
 #include <algorithm>
 #include <cassert>
 #include <cstdint>
+#include <optional>
 #include <string>
 #include <vector>
 
diff --git a/clang-tools-extra/clang-tidy/misc/StaticAssertCheck.cpp b/clang-tools-extra/clang-tidy/misc/StaticAssertCheck.cpp
index 93df4915e9f742..eaa7022321f92a 100644
--- a/clang-tools-extra/clang-tidy/misc/StaticAssertCheck.cpp
+++ b/clang-tools-extra/clang-tidy/misc/StaticAssertCheck.cpp
@@ -15,6 +15,7 @@
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Support/Casting.h"
+#include <optional>
 #include <string>
 
 using namespace clang::ast_matchers;
diff --git a/clang-tools-extra/clang-tidy/modernize/DeprecatedIosBaseAliasesCheck.cpp b/clang-tools-extra/clang-tidy/modernize/DeprecatedIosBaseAliasesCheck.cpp
index 5e3e05e88f0ca4..900077ee87b836 100644
--- a/clang-tools-extra/clang-tidy/modernize/DeprecatedIosBaseAliasesCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/DeprecatedIosBaseAliasesCheck.cpp
@@ -9,6 +9,7 @@
 #include "DeprecatedIosBaseAliasesCheck.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/ASTMatchers/ASTMatchFinder.h"
+#include <optional>
 
 using namespace clang::ast_matchers;
 
diff --git a/clang-tools-extra/clang-tidy/modernize/LoopConvertCheck.cpp b/clang-tools-extra/clang-tidy/modernize/LoopConvertCheck.cpp
index 3033fcbd3ee465..2db958ce8e6972 100644
--- a/clang-tools-extra/clang-tidy/modernize/LoopConvertCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/LoopConvertCheck.cpp
@@ -21,6 +21,7 @@
 #include "llvm/Support/raw_ostream.h"
 #include <cassert>
 #include <cstring>
+#include <optional>
 #include <utility>
 
 using namespace clang::ast_matchers;
diff --git a/clang-tools-extra/clang-tidy/modernize/LoopConvertUtils.cpp b/clang-tools-extra/clang-tidy/modernize/LoopConvertUtils.cpp
index fc3dfbdeac785f..7253b1daf6aef8 100644
--- a/clang-tools-extra/clang-tidy/modernize/LoopConvertUtils.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/LoopConvertUtils.cpp
@@ -21,6 +21,7 @@
 #include <algorithm>
 #include <cassert>
 #include <cstddef>
+#include <optional>
 #include <string>
 #include <utility>
 
diff --git a/clang-tools-extra/clang-tidy/modernize/ReplaceDisallowCopyAndAssignMacroCheck.cpp b/clang-tools-extra/clang-tidy/modernize/ReplaceDisallowCopyAndAssignMacroCheck.cpp
index 438fd4882b7fcb..fd96cb2ede977a 100644
--- a/clang-tools-extra/clang-tidy/modernize/ReplaceDisallowCopyAndAssignMacroCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/ReplaceDisallowCopyAndAssignMacroCheck.cpp
@@ -12,6 +12,7 @@
 #include "clang/Lex/PPCallbacks.h"
 #include "clang/Lex/Preprocessor.h"
 #include "llvm/Support/FormatVariadic.h"
+#include <optional>
 
 namespace clang {
 namespace tidy {
diff --git a/clang-tools-extra/clang-tidy/modernize/UseEqualsDefaultCheck.cpp b/clang-tools-extra/clang-tidy/modernize/UseEqualsDefaultCheck.cpp
index a545fae26a3bba..adf070866893b8 100644
--- a/clang-tools-extra/clang-tidy/modernize/UseEqualsDefaultCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/UseEqualsDefaultCheck.cpp
@@ -12,6 +12,7 @@
 #include "clang/AST/ASTContext.h"
 #include "clang/ASTMatchers/ASTMatchFinder.h"
 #include "clang/Lex/Lexer.h"
+#include <optional>
 
 using namespace clang::ast_matchers;
 
diff --git a/clang-tools-extra/clang-tidy/modernize/UseTrailingReturnTypeCheck.cpp b/clang-tools-extra/clang-tidy/modernize/UseTrailingReturnTypeCheck.cpp
index 9dc90937d6e542..6023fddb75add5 100644
--- a/clang-tools-extra/clang-tidy/modernize/UseTrailingReturnTypeCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/UseTrailingReturnTypeCheck.cpp
@@ -15,6 +15,7 @@
 #include "llvm/ADT/StringExtras.h"
 
 #include <cctype>
+#include <optional>
 
 using namespace clang::ast_matchers;
 
diff --git a/clang-tools-extra/clang-tidy/modernize/UseTrailingReturnTypeCheck.h b/clang-tools-extra/clang-tidy/modernize/UseTrailingReturnTypeCheck.h
index c2d831089d7c68..fa9dd407233d55 100644
--- a/clang-tools-extra/clang-tidy/modernize/UseTrailingReturnTypeCheck.h
+++ b/clang-tools-extra/clang-tidy/modernize/UseTrailingReturnTypeCheck.h
@@ -11,6 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 #include "clang/Lex/Token.h"
+#include <optional>
 
 namespace clang {
 namespace tidy {
diff --git a/clang-tools-extra/clang-tidy/mpi/BufferDerefCheck.h b/clang-tools-extra/clang-tidy/mpi/BufferDerefCheck.h
index a8da911957cac4..676654c2c27165 100644
--- a/clang-tools-extra/clang-tidy/mpi/BufferDerefCheck.h
+++ b/clang-tools-extra/clang-tidy/mpi/BufferDerefCheck.h
@@ -11,6 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 #include "clang/StaticAnalyzer/Checkers/MPIFunctionClassifier.h"
+#include <optional>
 
 namespace clang {
 namespace tidy {
diff --git a/clang-tools-extra/clang-tidy/mpi/TypeMismatchCheck.h b/clang-tools-extra/clang-tidy/mpi/TypeMismatchCheck.h
index da7b7c289b4653..261fec40160b18 100644
--- a/clang-tools-extra/clang-tidy/mpi/TypeMismatchCheck.h
+++ b/clang-tools-extra/clang-tidy/mpi/TypeMismatchCheck.h
@@ -12,6 +12,7 @@
 #include "../ClangTidyCheck.h"
 #include "clang/ASTMatchers/ASTMatchFinder.h"
 #include "clang/StaticAnalyzer/Checkers/MPIFunctionClassifier.h"
+#include <optional>
 
 namespace clang {
 namespace tidy {
diff --git a/clang-tools-extra/clang-tidy/objc/NSInvocationArgumentLifetimeCheck.cpp b/clang-tools-extra/clang-tidy/objc/NSInvocationArgumentLifetimeCheck.cpp
index 1650563a96930a..5127eaa557951a 100644
--- a/clang-tools-extra/clang-tidy/objc/NSInvocationArgumentLifetimeCheck.cpp
+++ b/clang-tools-extra/clang-tidy/objc/NSInvocationArgumentLifetimeCheck.cpp
@@ -25,6 +25,7 @@
 #include "clang/Lex/Lexer.h"
 #include "llvm/ADT/Optional.h"
 #include "llvm/ADT/StringRef.h"
+#include <optional>
 
 using namespace clang::ast_matchers;
 
diff --git a/clang-tools-extra/clang-tidy/performance/FasterStringFindCheck.cpp b/clang-tools-extra/clang-tidy/performance/FasterStringFindCheck.cpp
index e16be632d74265..190524720949b6 100644
--- a/clang-tools-extra/clang-tidy/performance/FasterStringFindCheck.cpp
+++ b/clang-tools-extra/clang-tidy/performance/FasterStringFindCheck.cpp
@@ -12,6 +12,7 @@
 #include "clang/ASTMatchers/ASTMatchFinder.h"
 #include "llvm/ADT/Optional.h"
 #include "llvm/Support/raw_ostream.h"
+#include <optional>
 
 using namespace clang::ast_matchers;
 
diff --git a/clang-tools-extra/clang-tidy/performance/ForRangeCopyCheck.cpp b/clang-tools-extra/clang-tidy/performance/ForRangeCopyCheck.cpp
index 8046301e3ce757..d2899852bf1330 100644
--- a/clang-tools-extra/clang-tidy/performance/ForRangeCopyCheck.cpp
+++ b/clang-tools-extra/clang-tidy/performance/ForRangeCopyCheck.cpp
@@ -14,6 +14,7 @@
 #include "../utils/TypeTraits.h"
 #include "clang/Analysis/Analyses/ExprMutationAnalyzer.h"
 #include "clang/Basic/Diagnostic.h"
+#include <optional>
 
 using namespace clang::ast_matchers;
 
diff --git a/clang-tools-extra/clang-tidy/performance/UnnecessaryCopyInitialization.cpp b/clang-tools-extra/clang-tidy/performance/UnnecessaryCopyInitialization.cpp
index b76f4bb6973fe4..249c00265da9d2 100644
--- a/clang-tools-extra/clang-tidy/performance/UnnecessaryCopyInitialization.cpp
+++ b/clang-tools-extra/clang-tidy/performance/UnnecessaryCopyInitialization.cpp
@@ -14,6 +14,7 @@
 #include "../utils/OptionsUtils.h"
 #include "clang/AST/Decl.h"
 #include "clang/Basic/Diagnostic.h"
+#include <optional>
 
 namespace clang {
 namespace tidy {
diff --git a/clang-tools-extra/clang-tidy/performance/UnnecessaryValueParamCheck.cpp b/clang-tools-extra/clang-tidy/performance/UnnecessaryValueParamCheck.cpp
index a8ca761d435f34..c3f742e06d09e8 100644
--- a/clang-tools-extra/clang-tidy/performance/UnnecessaryValueParamCheck.cpp
+++ b/clang-tools-extra/clang-tidy/performance/UnnecessaryValueParamCheck.cpp
@@ -16,6 +16,7 @@
 #include "clang/Frontend/CompilerInstance.h"
 #include "clang/Lex/Lexer.h"
 #include "clang/Lex/Preprocessor.h"
+#include <optional>
 
 using namespace clang::ast_matchers;
 
diff --git a/clang-tools-extra/clang-tidy/readability/ConstReturnTypeCheck.cpp b/clang-tools-extra/clang-tidy/readability/ConstReturnTypeCheck.cpp
index 0c9bda79006f49..e1ad21aaa3abd6 100644
--- a/clang-tools-extra/clang-tidy/readability/ConstReturnTypeCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/ConstReturnTypeCheck.cpp
@@ -13,6 +13,7 @@
 #include "clang/Basic/SourceLocation.h"
 #include "clang/Lex/Lexer.h"
 #include "llvm/ADT/Optional.h"
+#include <optional>
 
 using namespace clang::ast_matchers;
 
diff --git a/clang-tools-extra/clang-tidy/readability/FunctionCognitiveComplexityCheck.cpp b/clang-tools-extra/clang-tidy/readability/FunctionCognitiveComplexityCheck.cpp
index ba9e3d8e7258d3..416952cda80652 100644
--- a/clang-tools-extra/clang-tidy/readability/FunctionCognitiveComplexityCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/FunctionCognitiveComplexityCheck.cpp
@@ -26,6 +26,7 @@
 #include "llvm/Support/ErrorHandling.h"
 #include <array>
 #include <cassert>
+#include <optional>
 #include <stack>
 #include <tuple>
 #include <type_traits>
diff --git a/clang-tools-extra/clang-tidy/readability/IdentifierNamingCheck.cpp b/clang-tools-extra/clang-tidy/readability/IdentifierNamingCheck.cpp
index 524cd901052784..6aaa46d1c787ca 100644
--- a/clang-tools-extra/clang-tidy/readability/IdentifierNamingCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/IdentifierNamingCheck.cpp
@@ -20,6 +20,7 @@
 #include "llvm/Support/Path.h"
 #include "llvm/Support/Regex.h"
 #include "llvm/Support/YAMLParser.h"
+#include <optional>
 
 #define DEBUG_TYPE "clang-tidy"
 
diff --git a/clang-tools-extra/clang-tidy/readability/IdentifierNamingCheck.h b/clang-tools-extra/clang-tidy/readability/IdentifierNamingCheck.h
index 2739d18a0f74b6..a3ff2d55fa773b 100644
--- a/clang-tools-extra/clang-tidy/readability/IdentifierNamingCheck.h
+++ b/clang-tools-extra/clang-tidy/readability/IdentifierNamingCheck.h
@@ -11,6 +11,7 @@
 
 #include "../utils/RenamerClangTidyCheck.h"
 #include "llvm/ADT/Optional.h"
+#include <optional>
 namespace clang {
 namespace tidy {
 namespace readability {
diff --git a/clang-tools-extra/clang-tidy/readability/IsolateDeclarationCheck.cpp b/clang-tools-extra/clang-tidy/readability/IsolateDeclarationCheck.cpp
index 45f3ea6c681255..bc3d40db1c6daf 100644
--- a/clang-tools-extra/clang-tidy/readability/IsolateDeclarationCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/IsolateDeclarationCheck.cpp
@@ -9,6 +9,7 @@
 #include "IsolateDeclarationCheck.h"
 #include "../utils/LexerUtils.h"
 #include "clang/ASTMatchers/ASTMatchFinder.h"
+#include <optional>
 
 using namespace clang::ast_matchers;
 using namespace clang::tidy::utils::lexer;
diff --git a/clang-tools-extra/clang-tidy/readability/NamespaceCommentCheck.cpp b/clang-tools-extra/clang-tidy/readability/NamespaceCommentCheck.cpp
index 7ee48389c3c130..c53565c2604085 100644
--- a/clang-tools-extra/clang-tidy/readability/NamespaceCommentCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/NamespaceCommentCheck.cpp
@@ -14,6 +14,7 @@
 #include "clang/Basic/TokenKinds.h"
 #include "clang/Lex/Lexer.h"
 #include "llvm/ADT/StringExtras.h"
+#include <optional>
 
 using namespace clang::ast_matchers;
 
diff --git a/clang-tools-extra/clang-tidy/readability/QualifiedAutoCheck.cpp b/clang-tools-extra/clang-tidy/readability/QualifiedAutoCheck.cpp
index e25d1474ffdd01..c2ec9312bd7097 100644
--- a/clang-tools-extra/clang-tidy/readability/QualifiedAutoCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/QualifiedAutoCheck.cpp
@@ -11,6 +11,7 @@
 #include "clang/ASTMatchers/ASTMatchers.h"
 #include "llvm/ADT/Optional.h"
 #include "llvm/ADT/SmallVector.h"
+#include <optional>
 
 using namespace clang::ast_matchers;
 
diff --git a/clang-tools-extra/clang-tidy/readability/RedundantStringInitCheck.cpp b/clang-tools-extra/clang-tidy/readability/RedundantStringInitCheck.cpp
index d1537eba99f7d7..de250bbc6ce90a 100644
--- a/clang-tools-extra/clang-tidy/readability/RedundantStringInitCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/RedundantStringInitCheck.cpp
@@ -10,6 +10,7 @@
 #include "../utils/Matchers.h"
 #include "../utils/OptionsUtils.h"
 #include "clang/ASTMatchers/ASTMatchers.h"
+#include <optional>
 
 using namespace clang::ast_matchers;
 using namespace clang::tidy::matchers;
diff --git a/clang-tools-extra/clang-tidy/readability/SimplifyBooleanExprCheck.cpp b/clang-tools-extra/clang-tidy/readability/SimplifyBooleanExprCheck.cpp
index 1f1d605175a3f3..5e96a4917b07f8 100644
--- a/clang-tools-extra/clang-tidy/readability/SimplifyBooleanExprCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/SimplifyBooleanExprCheck.cpp
@@ -11,6 +11,7 @@
 #include "clang/Lex/Lexer.h"
 #include "llvm/Support/SaveAndRestore.h"
 
+#include <optional>
 #include <string>
 #include <utility>
 
diff --git a/clang-tools-extra/clang-tidy/readability/SuspiciousCallArgumentCheck.cpp b/clang-tools-extra/clang-tidy/readability/SuspiciousCallArgumentCheck.cpp
index 2a5e614584fb9b..8272a550249db8 100644
--- a/clang-tools-extra/clang-tidy/readability/SuspiciousCallArgumentCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/SuspiciousCallArgumentCheck.cpp
@@ -11,6 +11,7 @@
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/Type.h"
 #include "clang/ASTMatchers/ASTMatchFinder.h"
+#include <optional>
 #include <sstream>
 
 using namespace clang::ast_matchers;
diff --git a/clang-tools-extra/clang-tidy/readability/SuspiciousCallArgumentCheck.h b/clang-tools-extra/clang-tidy/readability/SuspiciousCallArgumentCheck.h
index dce19240e7257e..698d9cf52c1c19 100644
--- a/clang-tools-extra/clang-tidy/readability/SuspiciousCallArgumentCheck.h
+++ b/clang-tools-extra/clang-tidy/readability/SuspiciousCallArgumentCheck.h
@@ -11,6 +11,7 @@
 
 #include "../ClangTidyCheck.h"
 #include "llvm/ADT/StringSet.h"
+#include <optional>
 
 namespace clang {
 namespace tidy {
diff --git a/clang-tools-extra/clang-tidy/readability/UppercaseLiteralSuffixCheck.cpp b/clang-tools-extra/clang-tidy/readability/UppercaseLiteralSuffixCheck.cpp
index ee760f7c1ade70..e6fe75799c32a1 100644
--- a/clang-tools-extra/clang-tidy/readability/UppercaseLiteralSuffixCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/UppercaseLiteralSuffixCheck.cpp
@@ -14,6 +14,7 @@
 #include "llvm/ADT/Optional.h"
 #include "llvm/ADT/SmallString.h"
 #include <cctype>
+#include <optional>
 
 using namespace clang::ast_matchers;
 
diff --git a/clang-tools-extra/clang-tidy/utils/ExprSequence.cpp b/clang-tools-extra/clang-tidy/utils/ExprSequence.cpp
index 1d7c11f20361ce..3ca854dba67f43 100644
--- a/clang-tools-extra/clang-tidy/utils/ExprSequence.cpp
+++ b/clang-tools-extra/clang-tidy/utils/ExprSequence.cpp
@@ -8,6 +8,7 @@
 
 #include "ExprSequence.h"
 #include "clang/AST/ParentMapContext.h"
+#include <optional>
 
 namespace clang {
 namespace tidy {
diff --git a/clang-tools-extra/clang-tidy/utils/FileExtensionsUtils.cpp b/clang-tools-extra/clang-tidy/utils/FileExtensionsUtils.cpp
index 07c9eb0f00985e..6b1fe062fdd750 100644
--- a/clang-tools-extra/clang-tidy/utils/FileExtensionsUtils.cpp
+++ b/clang-tools-extra/clang-tidy/utils/FileExtensionsUtils.cpp
@@ -9,6 +9,7 @@
 #include "FileExtensionsUtils.h"
 #include "clang/Basic/CharInfo.h"
 #include "llvm/Support/Path.h"
+#include <optional>
 
 namespace clang {
 namespace tidy {
diff --git a/clang-tools-extra/clang-tidy/utils/FileExtensionsUtils.h b/clang-tools-extra/clang-tidy/utils/FileExtensionsUtils.h
index 26184a57378315..a79cf9a45a1292 100644
--- a/clang-tools-extra/clang-tidy/utils/FileExtensionsUtils.h
+++ b/clang-tools-extra/clang-tidy/utils/FileExtensionsUtils.h
@@ -14,6 +14,7 @@
 #include "llvm/ADT/Optional.h"
 #include "llvm/ADT/SmallSet.h"
 #include "llvm/ADT/StringRef.h"
+#include <optional>
 
 namespace clang {
 namespace tidy {
diff --git a/clang-tools-extra/clang-tidy/utils/FixItHintUtils.cpp b/clang-tools-extra/clang-tidy/utils/FixItHintUtils.cpp
index 546efd5ce5a295..2e96f29ffb458d 100644
--- a/clang-tools-extra/clang-tidy/utils/FixItHintUtils.cpp
+++ b/clang-tools-extra/clang-tidy/utils/FixItHintUtils.cpp
@@ -10,6 +10,7 @@
 #include "LexerUtils.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/Type.h"
+#include <optional>
 
 namespace clang {
 namespace tidy {
diff --git a/clang-tools-extra/clang-tidy/utils/FixItHintUtils.h b/clang-tools-extra/clang-tidy/utils/FixItHintUtils.h
index 2f5a74153f89a1..ec2ed50d9c7daf 100644
--- a/clang-tools-extra/clang-tidy/utils/FixItHintUtils.h
+++ b/clang-tools-extra/clang-tidy/utils/FixItHintUtils.h
@@ -12,6 +12,7 @@
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/Decl.h"
 #include "clang/Sema/DeclSpec.h"
+#include <optional>
 
 namespace clang {
 namespace tidy {
diff --git a/clang-tools-extra/clang-tidy/utils/IncludeInserter.cpp b/clang-tools-extra/clang-tidy/utils/IncludeInserter.cpp
index f4ca2d9129d733..ced2a73aa7688a 100644
--- a/clang-tools-extra/clang-tidy/utils/IncludeInserter.cpp
+++ b/clang-tools-extra/clang-tidy/utils/IncludeInserter.cpp
@@ -10,6 +10,7 @@
 #include "clang/Lex/PPCallbacks.h"
 #include "clang/Lex/Preprocessor.h"
 #include "clang/Lex/Token.h"
+#include <optional>
 
 namespace clang {
 namespace tidy {
diff --git a/clang-tools-extra/clang-tidy/utils/IncludeInserter.h b/clang-tools-extra/clang-tidy/utils/IncludeInserter.h
index 8e7c5f76ff80f4..0f4ba11acb05c9 100644
--- a/clang-tools-extra/clang-tidy/utils/IncludeInserter.h
+++ b/clang-tools-extra/clang-tidy/utils/IncludeInserter.h
@@ -13,6 +13,7 @@
 #include "clang/Basic/Diagnostic.h"
 #include "llvm/ADT/StringSet.h"
 #include <memory>
+#include <optional>
 
 namespace clang {
 class Preprocessor;
diff --git a/clang-tools-extra/clang-tidy/utils/IncludeSorter.cpp b/clang-tools-extra/clang-tidy/utils/IncludeSorter.cpp
index fc26d966c88efa..5b25d10d031a27 100644
--- a/clang-tools-extra/clang-tidy/utils/IncludeSorter.cpp
+++ b/clang-tools-extra/clang-tidy/utils/IncludeSorter.cpp
@@ -10,6 +10,7 @@
 #include "clang/Basic/SourceManager.h"
 #include "clang/Lex/Lexer.h"
 #include <algorithm>
+#include <optional>
 
 namespace clang {
 namespace tidy {
diff --git a/clang-tools-extra/clang-tidy/utils/IncludeSorter.h b/clang-tools-extra/clang-tidy/utils/IncludeSorter.h
index ac76fcd8d7d1ea..21fe5e48219c0d 100644
--- a/clang-tools-extra/clang-tidy/utils/IncludeSorter.h
+++ b/clang-tools-extra/clang-tidy/utils/IncludeSorter.h
@@ -10,6 +10,7 @@
 #define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_INCLUDESORTER_H
 
 #include "../ClangTidyCheck.h"
+#include <optional>
 #include <string>
 
 namespace clang {
diff --git a/clang-tools-extra/clang-tidy/utils/LexerUtils.cpp b/clang-tools-extra/clang-tidy/utils/LexerUtils.cpp
index 6ab48afc7d20a6..8bdbc1d19b9ae9 100644
--- a/clang-tools-extra/clang-tidy/utils/LexerUtils.cpp
+++ b/clang-tools-extra/clang-tidy/utils/LexerUtils.cpp
@@ -9,6 +9,7 @@
 #include "LexerUtils.h"
 #include "clang/AST/AST.h"
 #include "clang/Basic/SourceManager.h"
+#include <optional>
 
 namespace clang {
 namespace tidy {
diff --git a/clang-tools-extra/clang-tidy/utils/LexerUtils.h b/clang-tools-extra/clang-tidy/utils/LexerUtils.h
index b8e0f6ae2f7fc9..f67e0cb96ea99f 100644
--- a/clang-tools-extra/clang-tidy/utils/LexerUtils.h
+++ b/clang-tools-extra/clang-tidy/utils/LexerUtils.h
@@ -12,6 +12,7 @@
 #include "clang/AST/ASTContext.h"
 #include "clang/Basic/TokenKinds.h"
 #include "clang/Lex/Lexer.h"
+#include <optional>
 
 namespace clang {
 
diff --git a/clang-tools-extra/clang-tidy/utils/Matchers.h b/clang-tools-extra/clang-tidy/utils/Matchers.h
index ad9e25f201edb9..5a0e4599abf937 100644
--- a/clang-tools-extra/clang-tidy/utils/Matchers.h
+++ b/clang-tools-extra/clang-tidy/utils/Matchers.h
@@ -11,6 +11,7 @@
 
 #include "TypeTraits.h"
 #include "clang/ASTMatchers/ASTMatchers.h"
+#include <optional>
 
 namespace clang {
 namespace tidy {
diff --git a/clang-tools-extra/clang-tidy/utils/NamespaceAliaser.cpp b/clang-tools-extra/clang-tidy/utils/NamespaceAliaser.cpp
index fcefdc32024ca5..71a06f8e8e66a5 100644
--- a/clang-tools-extra/clang-tidy/utils/NamespaceAliaser.cpp
+++ b/clang-tools-extra/clang-tidy/utils/NamespaceAliaser.cpp
@@ -12,6 +12,7 @@
 #include "clang/ASTMatchers/ASTMatchFinder.h"
 #include "clang/ASTMatchers/ASTMatchers.h"
 #include "clang/Lex/Lexer.h"
+#include <optional>
 namespace clang {
 namespace tidy {
 namespace utils {
diff --git a/clang-tools-extra/clang-tidy/utils/NamespaceAliaser.h b/clang-tools-extra/clang-tidy/utils/NamespaceAliaser.h
index 177b0980c74594..934ce1341dc9ad 100644
--- a/clang-tools-extra/clang-tidy/utils/NamespaceAliaser.h
+++ b/clang-tools-extra/clang-tidy/utils/NamespaceAliaser.h
@@ -16,6 +16,7 @@
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/StringMap.h"
 #include <map>
+#include <optional>
 
 namespace clang {
 namespace tidy {
diff --git a/clang-tools-extra/clang-tidy/utils/RenamerClangTidyCheck.cpp b/clang-tools-extra/clang-tidy/utils/RenamerClangTidyCheck.cpp
index 449b0569537c2d..80a500592333fa 100644
--- a/clang-tools-extra/clang-tidy/utils/RenamerClangTidyCheck.cpp
+++ b/clang-tools-extra/clang-tidy/utils/RenamerClangTidyCheck.cpp
@@ -16,6 +16,7 @@
 #include "clang/Lex/Preprocessor.h"
 #include "llvm/ADT/DenseMapInfo.h"
 #include "llvm/ADT/PointerIntPair.h"
+#include <optional>
 
 #define DEBUG_TYPE "clang-tidy"
 
diff --git a/clang-tools-extra/clang-tidy/utils/RenamerClangTidyCheck.h b/clang-tools-extra/clang-tidy/utils/RenamerClangTidyCheck.h
index 327d98fc0485f9..2f3b79e73a1c84 100644
--- a/clang-tools-extra/clang-tidy/utils/RenamerClangTidyCheck.h
+++ b/clang-tools-extra/clang-tidy/utils/RenamerClangTidyCheck.h
@@ -14,6 +14,7 @@
 #include "llvm/ADT/DenseSet.h"
 #include "llvm/ADT/FunctionExtras.h"
 #include "llvm/ADT/Optional.h"
+#include <optional>
 #include <string>
 #include <utility>
 
diff --git a/clang-tools-extra/clang-tidy/utils/TransformerClangTidyCheck.cpp b/clang-tools-extra/clang-tidy/utils/TransformerClangTidyCheck.cpp
index 136b616836f1e9..b5e4b2b74a323d 100644
--- a/clang-tools-extra/clang-tidy/utils/TransformerClangTidyCheck.cpp
+++ b/clang-tools-extra/clang-tidy/utils/TransformerClangTidyCheck.cpp
@@ -10,6 +10,7 @@
 #include "clang/Basic/DiagnosticIDs.h"
 #include "clang/Lex/Preprocessor.h"
 #include "llvm/ADT/STLExtras.h"
+#include <optional>
 
 namespace clang {
 namespace tidy {
diff --git a/clang-tools-extra/clang-tidy/utils/TransformerClangTidyCheck.h b/clang-tools-extra/clang-tidy/utils/TransformerClangTidyCheck.h
index c52fce5aa8fe59..8ba15297cd9575 100644
--- a/clang-tools-extra/clang-tidy/utils/TransformerClangTidyCheck.h
+++ b/clang-tools-extra/clang-tidy/utils/TransformerClangTidyCheck.h
@@ -14,6 +14,7 @@
 #include "IncludeSorter.h"
 #include "clang/ASTMatchers/ASTMatchFinder.h"
 #include "clang/Tooling/Transformer/Transformer.h"
+#include <optional>
 
 namespace clang {
 namespace tidy {
diff --git a/clang-tools-extra/clang-tidy/utils/TypeTraits.cpp b/clang-tools-extra/clang-tidy/utils/TypeTraits.cpp
index ef897da98146c3..70a6ca17769f68 100644
--- a/clang-tools-extra/clang-tidy/utils/TypeTraits.cpp
+++ b/clang-tools-extra/clang-tidy/utils/TypeTraits.cpp
@@ -10,6 +10,7 @@
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/DeclCXX.h"
 #include "clang/ASTMatchers/ASTMatchFinder.h"
+#include <optional>
 
 namespace clang {
 namespace tidy {
diff --git a/clang-tools-extra/clang-tidy/utils/TypeTraits.h b/clang-tools-extra/clang-tidy/utils/TypeTraits.h
index 7e6b795e812719..37db6ef24e8ef7 100644
--- a/clang-tools-extra/clang-tidy/utils/TypeTraits.h
+++ b/clang-tools-extra/clang-tidy/utils/TypeTraits.h
@@ -11,6 +11,7 @@
 
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/Type.h"
+#include <optional>
 
 namespace clang {
 namespace tidy {
diff --git a/clang-tools-extra/clang-tidy/utils/UsingInserter.cpp b/clang-tools-extra/clang-tidy/utils/UsingInserter.cpp
index 480612c9140c23..2a10d99c0dba82 100644
--- a/clang-tools-extra/clang-tidy/utils/UsingInserter.cpp
+++ b/clang-tools-extra/clang-tidy/utils/UsingInserter.cpp
@@ -12,6 +12,7 @@
 #include "clang/ASTMatchers/ASTMatchFinder.h"
 #include "clang/ASTMatchers/ASTMatchers.h"
 #include "clang/Lex/Lexer.h"
+#include <optional>
 
 namespace clang {
 namespace tidy {
diff --git a/clang-tools-extra/clang-tidy/utils/UsingInserter.h b/clang-tools-extra/clang-tidy/utils/UsingInserter.h
index dfdf5ed3488c96..b23025bd5a7849 100644
--- a/clang-tools-extra/clang-tidy/utils/UsingInserter.h
+++ b/clang-tools-extra/clang-tidy/utils/UsingInserter.h
@@ -13,6 +13,7 @@
 #include "clang/AST/Stmt.h"
 #include "clang/Basic/Diagnostic.h"
 #include "clang/Basic/SourceManager.h"
+#include <optional>
 #include <set>
 
 namespace clang {
diff --git a/clang-tools-extra/clangd/AST.cpp b/clang-tools-extra/clangd/AST.cpp
index b9c76076f49072..d33960a0f5cf44 100644
--- a/clang-tools-extra/clangd/AST.cpp
+++ b/clang-tools-extra/clangd/AST.cpp
@@ -37,6 +37,7 @@
 #include "llvm/Support/Casting.h"
 #include "llvm/Support/raw_ostream.h"
 #include <iterator>
+#include <optional>
 #include <string>
 #include <vector>
 
diff --git a/clang-tools-extra/clangd/AST.h b/clang-tools-extra/clangd/AST.h
index 738d1b3094ae5d..fbbee899d0ed3b 100644
--- a/clang-tools-extra/clangd/AST.h
+++ b/clang-tools-extra/clangd/AST.h
@@ -21,6 +21,7 @@
 #include "clang/Basic/SourceLocation.h"
 #include "clang/Lex/MacroInfo.h"
 #include "llvm/ADT/StringRef.h"
+#include <optional>
 #include <string>
 #include <vector>
 
diff --git a/clang-tools-extra/clangd/ClangdLSPServer.cpp b/clang-tools-extra/clangd/ClangdLSPServer.cpp
index 8f5c8fa7024295..7d7517679f9d9a 100644
--- a/clang-tools-extra/clangd/ClangdLSPServer.cpp
+++ b/clang-tools-extra/clangd/ClangdLSPServer.cpp
@@ -44,6 +44,7 @@
 #include <functional>
 #include <memory>
 #include <mutex>
+#include <optional>
 #include <string>
 #include <vector>
 
diff --git a/clang-tools-extra/clangd/ClangdLSPServer.h b/clang-tools-extra/clangd/ClangdLSPServer.h
index 43b5e748075d74..1b1f4ad848fa39 100644
--- a/clang-tools-extra/clangd/ClangdLSPServer.h
+++ b/clang-tools-extra/clangd/ClangdLSPServer.h
@@ -23,6 +23,7 @@
 #include <chrono>
 #include <cstddef>
 #include <memory>
+#include <optional>
 #include <vector>
 
 namespace clang {
diff --git a/clang-tools-extra/clangd/ClangdServer.cpp b/clang-tools-extra/clangd/ClangdServer.cpp
index 2bde2a9e463bff..5a9b2edbffec28 100644
--- a/clang-tools-extra/clangd/ClangdServer.cpp
+++ b/clang-tools-extra/clangd/ClangdServer.cpp
@@ -50,6 +50,7 @@
 #include <future>
 #include <memory>
 #include <mutex>
+#include <optional>
 #include <string>
 #include <type_traits>
 
diff --git a/clang-tools-extra/clangd/ClangdServer.h b/clang-tools-extra/clangd/ClangdServer.h
index 98c67b8ef23cdd..097fed13446488 100644
--- a/clang-tools-extra/clangd/ClangdServer.h
+++ b/clang-tools-extra/clangd/ClangdServer.h
@@ -35,6 +35,7 @@
 #include "llvm/ADT/StringRef.h"
 #include <functional>
 #include <memory>
+#include <optional>
 #include <string>
 #include <type_traits>
 #include <utility>
diff --git a/clang-tools-extra/clangd/CodeComplete.cpp b/clang-tools-extra/clangd/CodeComplete.cpp
index 9015be6cf7c89d..42e6ef2bc2314f 100644
--- a/clang-tools-extra/clangd/CodeComplete.cpp
+++ b/clang-tools-extra/clangd/CodeComplete.cpp
@@ -70,6 +70,7 @@
 #include <algorithm>
 #include <iterator>
 #include <limits>
+#include <optional>
 #include <utility>
 
 // We log detailed candidate here if you run with -debug-only=codecomplete.
diff --git a/clang-tools-extra/clangd/CodeComplete.h b/clang-tools-extra/clangd/CodeComplete.h
index b661eac5987f68..e88e9b3734b225 100644
--- a/clang-tools-extra/clangd/CodeComplete.h
+++ b/clang-tools-extra/clangd/CodeComplete.h
@@ -31,6 +31,7 @@
 #include "llvm/ADT/StringRef.h"
 #include <functional>
 #include <future>
+#include <optional>
 #include <utility>
 
 namespace clang {
diff --git a/clang-tools-extra/clangd/CompileCommands.h b/clang-tools-extra/clangd/CompileCommands.h
index 3cf41afd4ccf10..561d9ea2f9ed32 100644
--- a/clang-tools-extra/clangd/CompileCommands.h
+++ b/clang-tools-extra/clangd/CompileCommands.h
@@ -13,6 +13,7 @@
 #include "llvm/ADT/StringMap.h"
 #include "llvm/ADT/StringRef.h"
 #include <deque>
+#include <optional>
 #include <string>
 #include <vector>
 
diff --git a/clang-tools-extra/clangd/ConfigCompile.cpp b/clang-tools-extra/clangd/ConfigCompile.cpp
index 2291e5fdaf7578..e1a511d0a082a3 100644
--- a/clang-tools-extra/clangd/ConfigCompile.cpp
+++ b/clang-tools-extra/clangd/ConfigCompile.cpp
@@ -45,6 +45,7 @@
 #include "llvm/Support/SourceMgr.h"
 #include <algorithm>
 #include <memory>
+#include <optional>
 #include <string>
 #include <vector>
 
diff --git a/clang-tools-extra/clangd/Diagnostics.cpp b/clang-tools-extra/clangd/Diagnostics.cpp
index a6a0204cf6b783..6c8cf5c52217fd 100644
--- a/clang-tools-extra/clangd/Diagnostics.cpp
+++ b/clang-tools-extra/clangd/Diagnostics.cpp
@@ -33,6 +33,7 @@
 #include <algorithm>
 #include <cassert>
 #include <cstddef>
+#include <optional>
 #include <vector>
 
 namespace clang {
diff --git a/clang-tools-extra/clangd/Diagnostics.h b/clang-tools-extra/clangd/Diagnostics.h
index 6004bb147361af..b1a1f0170d3460 100644
--- a/clang-tools-extra/clangd/Diagnostics.h
+++ b/clang-tools-extra/clangd/Diagnostics.h
@@ -23,6 +23,7 @@
 #include <cassert>
 #include <functional>
 #include <memory>
+#include <optional>
 #include <string>
 #include <utility>
 #include <vector>
diff --git a/clang-tools-extra/clangd/DraftStore.cpp b/clang-tools-extra/clangd/DraftStore.cpp
index 8f5b54bc7b21ab..7df70e69bdf31c 100644
--- a/clang-tools-extra/clangd/DraftStore.cpp
+++ b/clang-tools-extra/clangd/DraftStore.cpp
@@ -11,6 +11,7 @@
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/Support/VirtualFileSystem.h"
 #include <memory>
+#include <optional>
 
 namespace clang {
 namespace clangd {
diff --git a/clang-tools-extra/clangd/DraftStore.h b/clang-tools-extra/clangd/DraftStore.h
index 9a469262149688..a19fe55890b1ca 100644
--- a/clang-tools-extra/clangd/DraftStore.h
+++ b/clang-tools-extra/clangd/DraftStore.h
@@ -14,6 +14,7 @@
 #include "llvm/ADT/StringMap.h"
 #include "llvm/Support/VirtualFileSystem.h"
 #include <mutex>
+#include <optional>
 #include <string>
 #include <vector>
 
diff --git a/clang-tools-extra/clangd/DumpAST.cpp b/clang-tools-extra/clangd/DumpAST.cpp
index 1cf5e4ef8fe926..438733d44f13fd 100644
--- a/clang-tools-extra/clangd/DumpAST.cpp
+++ b/clang-tools-extra/clangd/DumpAST.cpp
@@ -23,6 +23,7 @@
 #include "clang/Tooling/Syntax/Tokens.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Support/raw_ostream.h"
+#include <optional>
 
 namespace clang {
 namespace clangd {
diff --git a/clang-tools-extra/clangd/ExpectedTypes.cpp b/clang-tools-extra/clangd/ExpectedTypes.cpp
index c45fa5925dbfe1..563612aa745cae 100644
--- a/clang-tools-extra/clangd/ExpectedTypes.cpp
+++ b/clang-tools-extra/clangd/ExpectedTypes.cpp
@@ -12,6 +12,7 @@
 #include "clang/AST/Type.h"
 #include "clang/Index/USRGeneration.h"
 #include "clang/Sema/CodeCompleteConsumer.h"
+#include <optional>
 
 namespace clang {
 namespace clangd {
diff --git a/clang-tools-extra/clangd/ExpectedTypes.h b/clang-tools-extra/clangd/ExpectedTypes.h
index 873b106b91d176..6cfd0936def6ed 100644
--- a/clang-tools-extra/clangd/ExpectedTypes.h
+++ b/clang-tools-extra/clangd/ExpectedTypes.h
@@ -20,6 +20,7 @@
 
 #include "clang/AST/Type.h"
 #include "llvm/ADT/StringRef.h"
+#include <optional>
 
 namespace clang {
 class CodeCompletionResult;
diff --git a/clang-tools-extra/clangd/FS.cpp b/clang-tools-extra/clangd/FS.cpp
index 089fbac13e3226..587b9212188c09 100644
--- a/clang-tools-extra/clangd/FS.cpp
+++ b/clang-tools-extra/clangd/FS.cpp
@@ -10,6 +10,7 @@
 #include "clang/Basic/LLVM.h"
 #include "llvm/Support/Path.h"
 #include "llvm/Support/VirtualFileSystem.h"
+#include <optional>
 
 namespace clang {
 namespace clangd {
diff --git a/clang-tools-extra/clangd/FS.h b/clang-tools-extra/clangd/FS.h
index 5994bdff9271e5..96b04dc7c9e570 100644
--- a/clang-tools-extra/clangd/FS.h
+++ b/clang-tools-extra/clangd/FS.h
@@ -14,6 +14,7 @@
 #include "llvm/ADT/Optional.h"
 #include "llvm/ADT/StringMap.h"
 #include "llvm/Support/VirtualFileSystem.h"
+#include <optional>
 
 namespace clang {
 namespace clangd {
diff --git a/clang-tools-extra/clangd/FeatureModule.h b/clang-tools-extra/clangd/FeatureModule.h
index 43007a297469bc..eb4232f26b0654 100644
--- a/clang-tools-extra/clangd/FeatureModule.h
+++ b/clang-tools-extra/clangd/FeatureModule.h
@@ -16,6 +16,7 @@
 #include "llvm/Support/Compiler.h"
 #include "llvm/Support/JSON.h"
 #include <memory>
+#include <optional>
 #include <type_traits>
 #include <vector>
 
diff --git a/clang-tools-extra/clangd/FindSymbols.cpp b/clang-tools-extra/clangd/FindSymbols.cpp
index 0a18d5b4528d99..682ca79a746dc6 100644
--- a/clang-tools-extra/clangd/FindSymbols.cpp
+++ b/clang-tools-extra/clangd/FindSymbols.cpp
@@ -21,6 +21,7 @@
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringRef.h"
 #include <limits>
+#include <optional>
 #include <tuple>
 
 #define DEBUG_TYPE "FindSymbols"
diff --git a/clang-tools-extra/clangd/GlobalCompilationDatabase.cpp b/clang-tools-extra/clangd/GlobalCompilationDatabase.cpp
index 086315feb3821c..37f6173d30e6cc 100644
--- a/clang-tools-extra/clangd/GlobalCompilationDatabase.cpp
+++ b/clang-tools-extra/clangd/GlobalCompilationDatabase.cpp
@@ -30,6 +30,7 @@
 #include <chrono>
 #include <condition_variable>
 #include <mutex>
+#include <optional>
 #include <string>
 #include <tuple>
 #include <vector>
diff --git a/clang-tools-extra/clangd/GlobalCompilationDatabase.h b/clang-tools-extra/clangd/GlobalCompilationDatabase.h
index 511fa6cb201421..04481fa6ea2277 100644
--- a/clang-tools-extra/clangd/GlobalCompilationDatabase.h
+++ b/clang-tools-extra/clangd/GlobalCompilationDatabase.h
@@ -20,6 +20,7 @@
 #include "llvm/ADT/StringMap.h"
 #include <memory>
 #include <mutex>
+#include <optional>
 #include <vector>
 
 namespace clang {
diff --git a/clang-tools-extra/clangd/HeaderSourceSwitch.cpp b/clang-tools-extra/clangd/HeaderSourceSwitch.cpp
index 9221fad77d24e7..ded7a43d4ea143 100644
--- a/clang-tools-extra/clangd/HeaderSourceSwitch.cpp
+++ b/clang-tools-extra/clangd/HeaderSourceSwitch.cpp
@@ -13,6 +13,7 @@
 #include "support/Logger.h"
 #include "support/Path.h"
 #include "clang/AST/Decl.h"
+#include <optional>
 
 namespace clang {
 namespace clangd {
diff --git a/clang-tools-extra/clangd/HeaderSourceSwitch.h b/clang-tools-extra/clangd/HeaderSourceSwitch.h
index 092b41353aef3c..1cf9da969e24be 100644
--- a/clang-tools-extra/clangd/HeaderSourceSwitch.h
+++ b/clang-tools-extra/clangd/HeaderSourceSwitch.h
@@ -11,6 +11,7 @@
 
 #include "ParsedAST.h"
 #include "llvm/ADT/Optional.h"
+#include <optional>
 
 namespace clang {
 namespace clangd {
diff --git a/clang-tools-extra/clangd/Headers.cpp b/clang-tools-extra/clangd/Headers.cpp
index b22589a374cd65..fd058e8cfd8942 100644
--- a/clang-tools-extra/clangd/Headers.cpp
+++ b/clang-tools-extra/clangd/Headers.cpp
@@ -19,6 +19,7 @@
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Support/Path.h"
 #include <cstring>
+#include <optional>
 
 namespace clang {
 namespace clangd {
diff --git a/clang-tools-extra/clangd/Headers.h b/clang-tools-extra/clangd/Headers.h
index fd739845cdd841..68ccf935fbd439 100644
--- a/clang-tools-extra/clangd/Headers.h
+++ b/clang-tools-extra/clangd/Headers.h
@@ -27,6 +27,7 @@
 #include "llvm/ADT/StringSet.h"
 #include "llvm/Support/Error.h"
 #include "llvm/Support/FileSystem/UniqueID.h"
+#include <optional>
 #include <string>
 
 namespace clang {
diff --git a/clang-tools-extra/clangd/Hover.cpp b/clang-tools-extra/clangd/Hover.cpp
index 72c0841d34c64e..ca6301999f2c52 100644
--- a/clang-tools-extra/clangd/Hover.cpp
+++ b/clang-tools-extra/clangd/Hover.cpp
@@ -47,6 +47,7 @@
 #include "llvm/Support/Format.h"
 #include "llvm/Support/ScopedPrinter.h"
 #include "llvm/Support/raw_ostream.h"
+#include <optional>
 #include <string>
 
 namespace clang {
diff --git a/clang-tools-extra/clangd/Hover.h b/clang-tools-extra/clangd/Hover.h
index 4565e6446db16f..a2c4e60949493d 100644
--- a/clang-tools-extra/clangd/Hover.h
+++ b/clang-tools-extra/clangd/Hover.h
@@ -13,6 +13,7 @@
 #include "Protocol.h"
 #include "support/Markup.h"
 #include "clang/Index/IndexSymbol.h"
+#include <optional>
 
 namespace clang {
 namespace clangd {
diff --git a/clang-tools-extra/clangd/IncludeCleaner.cpp b/clang-tools-extra/clangd/IncludeCleaner.cpp
index 3cfa52b40a20c9..daac976a41e797 100644
--- a/clang-tools-extra/clangd/IncludeCleaner.cpp
+++ b/clang-tools-extra/clangd/IncludeCleaner.cpp
@@ -31,6 +31,7 @@
 #include "llvm/Support/Path.h"
 #include "llvm/Support/Regex.h"
 #include <functional>
+#include <optional>
 
 namespace clang {
 namespace clangd {
diff --git a/clang-tools-extra/clangd/IncludeCleaner.h b/clang-tools-extra/clangd/IncludeCleaner.h
index 4ce31baaa067a2..fc3d04da78a8ed 100644
--- a/clang-tools-extra/clangd/IncludeCleaner.h
+++ b/clang-tools-extra/clangd/IncludeCleaner.h
@@ -26,6 +26,7 @@
 #include "llvm/ADT/DenseSet.h"
 #include "llvm/ADT/STLFunctionalExtras.h"
 #include "llvm/ADT/StringSet.h"
+#include <optional>
 #include <vector>
 
 namespace clang {
diff --git a/clang-tools-extra/clangd/IncludeFixer.cpp b/clang-tools-extra/clangd/IncludeFixer.cpp
index d48d5937dc93d0..5ab993230709ef 100644
--- a/clang-tools-extra/clangd/IncludeFixer.cpp
+++ b/clang-tools-extra/clangd/IncludeFixer.cpp
@@ -41,6 +41,7 @@
 #include "llvm/Support/Error.h"
 #include "llvm/Support/FormatVariadic.h"
 #include <algorithm>
+#include <optional>
 #include <set>
 #include <string>
 #include <vector>
diff --git a/clang-tools-extra/clangd/IncludeFixer.h b/clang-tools-extra/clangd/IncludeFixer.h
index 50237dd948e4a6..2a74c23ffa8eaf 100644
--- a/clang-tools-extra/clangd/IncludeFixer.h
+++ b/clang-tools-extra/clangd/IncludeFixer.h
@@ -24,6 +24,7 @@
 #include "llvm/ADT/StringMap.h"
 #include "llvm/ADT/StringRef.h"
 #include <memory>
+#include <optional>
 
 namespace clang {
 namespace clangd {
diff --git a/clang-tools-extra/clangd/InlayHints.cpp b/clang-tools-extra/clangd/InlayHints.cpp
index 7af39658885be3..20a8adcecc7310 100644
--- a/clang-tools-extra/clangd/InlayHints.cpp
+++ b/clang-tools-extra/clangd/InlayHints.cpp
@@ -18,6 +18,7 @@
 #include "clang/Basic/Builtins.h"
 #include "clang/Basic/SourceManager.h"
 #include "llvm/ADT/ScopeExit.h"
+#include <optional>
 
 namespace clang {
 namespace clangd {
diff --git a/clang-tools-extra/clangd/JSONTransport.cpp b/clang-tools-extra/clangd/JSONTransport.cpp
index 254e54ad5c23d0..50b1833a75752c 100644
--- a/clang-tools-extra/clangd/JSONTransport.cpp
+++ b/clang-tools-extra/clangd/JSONTransport.cpp
@@ -13,6 +13,7 @@
 #include "support/ThreadCrashReporter.h"
 #include "llvm/ADT/SmallString.h"
 #include "llvm/Support/Error.h"
+#include <optional>
 #include <system_error>
 
 namespace clang {
diff --git a/clang-tools-extra/clangd/ParsedAST.cpp b/clang-tools-extra/clangd/ParsedAST.cpp
index aa84ce35561d55..c2846749a70823 100644
--- a/clang-tools-extra/clangd/ParsedAST.cpp
+++ b/clang-tools-extra/clangd/ParsedAST.cpp
@@ -50,6 +50,7 @@
 #include "llvm/ADT/StringRef.h"
 #include <algorithm>
 #include <memory>
+#include <optional>
 #include <vector>
 
 // Force the linker to link in Clang-tidy modules.
diff --git a/clang-tools-extra/clangd/ParsedAST.h b/clang-tools-extra/clangd/ParsedAST.h
index e9133f16473bc5..8f74c17992d416 100644
--- a/clang-tools-extra/clangd/ParsedAST.h
+++ b/clang-tools-extra/clangd/ParsedAST.h
@@ -34,6 +34,7 @@
 #include "llvm/ADT/Optional.h"
 #include "llvm/ADT/StringRef.h"
 #include <memory>
+#include <optional>
 #include <string>
 #include <vector>
 
diff --git a/clang-tools-extra/clangd/Protocol.h b/clang-tools-extra/clangd/Protocol.h
index d68efad691757b..9cd1955ba95bec 100644
--- a/clang-tools-extra/clangd/Protocol.h
+++ b/clang-tools-extra/clangd/Protocol.h
@@ -33,6 +33,7 @@
 #include "llvm/Support/raw_ostream.h"
 #include <bitset>
 #include <memory>
+#include <optional>
 #include <string>
 #include <vector>
 
diff --git a/clang-tools-extra/clangd/Quality.cpp b/clang-tools-extra/clangd/Quality.cpp
index da8e60ef8d88eb..72e3154bdbab6e 100644
--- a/clang-tools-extra/clangd/Quality.cpp
+++ b/clang-tools-extra/clangd/Quality.cpp
@@ -26,6 +26,7 @@
 #include "llvm/Support/raw_ostream.h"
 #include <algorithm>
 #include <cmath>
+#include <optional>
 
 namespace clang {
 namespace clangd {
diff --git a/clang-tools-extra/clangd/Quality.h b/clang-tools-extra/clangd/Quality.h
index 88235964a768ef..2a4efe934f5806 100644
--- a/clang-tools-extra/clangd/Quality.h
+++ b/clang-tools-extra/clangd/Quality.h
@@ -33,6 +33,7 @@
 #include "llvm/ADT/StringSet.h"
 #include <algorithm>
 #include <functional>
+#include <optional>
 #include <vector>
 
 namespace llvm {
diff --git a/clang-tools-extra/clangd/Selection.cpp b/clang-tools-extra/clangd/Selection.cpp
index 754d31c7155b56..56836fd8509530 100644
--- a/clang-tools-extra/clangd/Selection.cpp
+++ b/clang-tools-extra/clangd/Selection.cpp
@@ -31,6 +31,7 @@
 #include "llvm/Support/Casting.h"
 #include "llvm/Support/raw_ostream.h"
 #include <algorithm>
+#include <optional>
 #include <set>
 #include <string>
 
diff --git a/clang-tools-extra/clangd/SemanticHighlighting.cpp b/clang-tools-extra/clangd/SemanticHighlighting.cpp
index 1f9f851b2817bd..eaed8870fcbe9c 100644
--- a/clang-tools-extra/clangd/SemanticHighlighting.cpp
+++ b/clang-tools-extra/clangd/SemanticHighlighting.cpp
@@ -33,6 +33,7 @@
 #include "llvm/Support/Casting.h"
 #include "llvm/Support/Error.h"
 #include <algorithm>
+#include <optional>
 
 namespace clang {
 namespace clangd {
diff --git a/clang-tools-extra/clangd/SemanticSelection.cpp b/clang-tools-extra/clangd/SemanticSelection.cpp
index 3541ede75f5c76..fe01c1577bff5e 100644
--- a/clang-tools-extra/clangd/SemanticSelection.cpp
+++ b/clang-tools-extra/clangd/SemanticSelection.cpp
@@ -25,6 +25,7 @@
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Support/Casting.h"
 #include "llvm/Support/Error.h"
+#include <optional>
 #include <queue>
 #include <vector>
 
diff --git a/clang-tools-extra/clangd/SourceCode.cpp b/clang-tools-extra/clangd/SourceCode.cpp
index 0ba98f3d838fa5..90dd37f82f04b1 100644
--- a/clang-tools-extra/clangd/SourceCode.cpp
+++ b/clang-tools-extra/clangd/SourceCode.cpp
@@ -40,6 +40,7 @@
 #include "llvm/Support/xxhash.h"
 #include <algorithm>
 #include <cstddef>
+#include <optional>
 #include <string>
 #include <vector>
 
diff --git a/clang-tools-extra/clangd/SourceCode.h b/clang-tools-extra/clangd/SourceCode.h
index fa4e03b9f2e5a2..69626c2678d5ed 100644
--- a/clang-tools-extra/clangd/SourceCode.h
+++ b/clang-tools-extra/clangd/SourceCode.h
@@ -28,6 +28,7 @@
 #include "llvm/ADT/StringRef.h"
 #include "llvm/ADT/StringSet.h"
 #include "llvm/Support/Error.h"
+#include <optional>
 #include <string>
 
 namespace clang {
diff --git a/clang-tools-extra/clangd/SystemIncludeExtractor.cpp b/clang-tools-extra/clangd/SystemIncludeExtractor.cpp
index b65902bd4256bd..d78d56e367c8e6 100644
--- a/clang-tools-extra/clangd/SystemIncludeExtractor.cpp
+++ b/clang-tools-extra/clangd/SystemIncludeExtractor.cpp
@@ -52,6 +52,7 @@
 #include <algorithm>
 #include <iterator>
 #include <map>
+#include <optional>
 #include <string>
 #include <vector>
 
diff --git a/clang-tools-extra/clangd/TUScheduler.cpp b/clang-tools-extra/clangd/TUScheduler.cpp
index 44a0d4ac941f47..50802d2c8b377f 100644
--- a/clang-tools-extra/clangd/TUScheduler.cpp
+++ b/clang-tools-extra/clangd/TUScheduler.cpp
@@ -85,6 +85,7 @@
 #include <functional>
 #include <memory>
 #include <mutex>
+#include <optional>
 #include <queue>
 #include <string>
 #include <thread>
diff --git a/clang-tools-extra/clangd/TUScheduler.h b/clang-tools-extra/clangd/TUScheduler.h
index d616814a5edb97..f9582a6f3f42f2 100644
--- a/clang-tools-extra/clangd/TUScheduler.h
+++ b/clang-tools-extra/clangd/TUScheduler.h
@@ -22,6 +22,7 @@
 #include "llvm/ADT/StringMap.h"
 #include "llvm/ADT/StringRef.h"
 #include <chrono>
+#include <optional>
 #include <string>
 
 namespace clang {
diff --git a/clang-tools-extra/clangd/XRefs.cpp b/clang-tools-extra/clangd/XRefs.cpp
index 953f911b1398e3..da33b722876fe1 100644
--- a/clang-tools-extra/clangd/XRefs.cpp
+++ b/clang-tools-extra/clangd/XRefs.cpp
@@ -61,6 +61,7 @@
 #include "llvm/Support/Error.h"
 #include "llvm/Support/Path.h"
 #include "llvm/Support/raw_ostream.h"
+#include <optional>
 #include <vector>
 
 namespace clang {
diff --git a/clang-tools-extra/clangd/XRefs.h b/clang-tools-extra/clangd/XRefs.h
index 60e8e881958dbd..8af5106078b4e2 100644
--- a/clang-tools-extra/clangd/XRefs.h
+++ b/clang-tools-extra/clangd/XRefs.h
@@ -22,6 +22,7 @@
 #include "llvm/ADT/Optional.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Support/raw_ostream.h"
+#include <optional>
 #include <vector>
 
 namespace clang {
diff --git a/clang-tools-extra/clangd/index/Background.cpp b/clang-tools-extra/clangd/index/Background.cpp
index 2b75b8b585020f..f09fb5d293018a 100644
--- a/clang-tools-extra/clangd/index/Background.cpp
+++ b/clang-tools-extra/clangd/index/Background.cpp
@@ -49,6 +49,7 @@
 #include <memory>
 #include <mutex>
 #include <numeric>
+#include <optional>
 #include <queue>
 #include <random>
 #include <string>
diff --git a/clang-tools-extra/clangd/index/Background.h b/clang-tools-extra/clangd/index/Background.h
index ac99a151e73bba..45f679a16617cc 100644
--- a/clang-tools-extra/clangd/index/Background.h
+++ b/clang-tools-extra/clangd/index/Background.h
@@ -27,6 +27,7 @@
 #include <condition_variable>
 #include <deque>
 #include <mutex>
+#include <optional>
 #include <queue>
 #include <string>
 #include <thread>
diff --git a/clang-tools-extra/clangd/index/BackgroundIndexStorage.cpp b/clang-tools-extra/clangd/index/BackgroundIndexStorage.cpp
index 1de118993a11e4..c7bbd98a32cec4 100644
--- a/clang-tools-extra/clangd/index/BackgroundIndexStorage.cpp
+++ b/clang-tools-extra/clangd/index/BackgroundIndexStorage.cpp
@@ -19,6 +19,7 @@
 #include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/Path.h"
 #include <functional>
+#include <optional>
 
 namespace clang {
 namespace clangd {
diff --git a/clang-tools-extra/clangd/index/BackgroundQueue.cpp b/clang-tools-extra/clangd/index/BackgroundQueue.cpp
index b0dc2acca356bf..5fb1511353ee2d 100644
--- a/clang-tools-extra/clangd/index/BackgroundQueue.cpp
+++ b/clang-tools-extra/clangd/index/BackgroundQueue.cpp
@@ -8,6 +8,7 @@
 
 #include "index/Background.h"
 #include "support/Logger.h"
+#include <optional>
 
 namespace clang {
 namespace clangd {
diff --git a/clang-tools-extra/clangd/index/FileIndex.cpp b/clang-tools-extra/clangd/index/FileIndex.cpp
index 1080cb0f4b81e0..95bda42a796c4d 100644
--- a/clang-tools-extra/clangd/index/FileIndex.cpp
+++ b/clang-tools-extra/clangd/index/FileIndex.cpp
@@ -35,6 +35,7 @@
 #include "llvm/ADT/StringRef.h"
 #include <algorithm>
 #include <memory>
+#include <optional>
 #include <tuple>
 #include <utility>
 #include <vector>
diff --git a/clang-tools-extra/clangd/index/FileIndex.h b/clang-tools-extra/clangd/index/FileIndex.h
index 24ffbc9c7fb529..31757d13eb40c0 100644
--- a/clang-tools-extra/clangd/index/FileIndex.h
+++ b/clang-tools-extra/clangd/index/FileIndex.h
@@ -31,6 +31,7 @@
 #include "llvm/ADT/StringMap.h"
 #include "llvm/ADT/StringRef.h"
 #include <memory>
+#include <optional>
 #include <vector>
 
 namespace clang {
diff --git a/clang-tools-extra/clangd/index/Index.h b/clang-tools-extra/clangd/index/Index.h
index 5406b95eae04a3..e836d459c2ee2b 100644
--- a/clang-tools-extra/clangd/index/Index.h
+++ b/clang-tools-extra/clangd/index/Index.h
@@ -18,6 +18,7 @@
 #include "llvm/ADT/Optional.h"
 #include "llvm/Support/JSON.h"
 #include <mutex>
+#include <optional>
 #include <string>
 
 namespace clang {
diff --git a/clang-tools-extra/clangd/index/IndexAction.cpp b/clang-tools-extra/clangd/index/IndexAction.cpp
index a5f8f6b4498c2a..d97dc40e03a6bd 100644
--- a/clang-tools-extra/clangd/index/IndexAction.cpp
+++ b/clang-tools-extra/clangd/index/IndexAction.cpp
@@ -22,6 +22,7 @@
 #include <cstddef>
 #include <functional>
 #include <memory>
+#include <optional>
 #include <utility>
 
 namespace clang {
diff --git a/clang-tools-extra/clangd/index/Serialization.h b/clang-tools-extra/clangd/index/Serialization.h
index 16b80961a98163..fceaefed4c0ccf 100644
--- a/clang-tools-extra/clangd/index/Serialization.h
+++ b/clang-tools-extra/clangd/index/Serialization.h
@@ -29,6 +29,7 @@
 #include "index/Symbol.h"
 #include "clang/Tooling/CompilationDatabase.h"
 #include "llvm/Support/Error.h"
+#include <optional>
 
 namespace clang {
 namespace clangd {
diff --git a/clang-tools-extra/clangd/index/StdLib.cpp b/clang-tools-extra/clangd/index/StdLib.cpp
index ac7388ca30b2a8..ab9a8ed8cfb329 100644
--- a/clang-tools-extra/clangd/index/StdLib.cpp
+++ b/clang-tools-extra/clangd/index/StdLib.cpp
@@ -8,6 +8,7 @@
 #include "StdLib.h"
 #include <fstream>
 #include <memory>
+#include <optional>
 #include <string>
 #include <vector>
 
diff --git a/clang-tools-extra/clangd/index/StdLib.h b/clang-tools-extra/clangd/index/StdLib.h
index 6df30ace669c8f..6c170dceba9c70 100644
--- a/clang-tools-extra/clangd/index/StdLib.h
+++ b/clang-tools-extra/clangd/index/StdLib.h
@@ -26,6 +26,7 @@
 #include "index/Symbol.h"
 #include "support/ThreadsafeFS.h"
 #include "llvm/ADT/StringRef.h"
+#include <optional>
 #include <string>
 
 namespace clang {
diff --git a/clang-tools-extra/clangd/index/SymbolCollector.cpp b/clang-tools-extra/clangd/index/SymbolCollector.cpp
index 4c865a4317ba5b..5f9c8bbb4ee9d1 100644
--- a/clang-tools-extra/clangd/index/SymbolCollector.cpp
+++ b/clang-tools-extra/clangd/index/SymbolCollector.cpp
@@ -33,6 +33,7 @@
 #include "llvm/Support/Casting.h"
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/Path.h"
+#include <optional>
 
 namespace clang {
 namespace clangd {
diff --git a/clang-tools-extra/clangd/index/SymbolCollector.h b/clang-tools-extra/clangd/index/SymbolCollector.h
index f3d8d80aa8deef..6acce1f3e3c40c 100644
--- a/clang-tools-extra/clangd/index/SymbolCollector.h
+++ b/clang-tools-extra/clangd/index/SymbolCollector.h
@@ -25,6 +25,7 @@
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/DenseMap.h"
 #include <functional>
+#include <optional>
 
 namespace clang {
 namespace clangd {
diff --git a/clang-tools-extra/clangd/index/YAMLSerialization.cpp b/clang-tools-extra/clangd/index/YAMLSerialization.cpp
index 593ce30501b046..c51489fd5dc66c 100644
--- a/clang-tools-extra/clangd/index/YAMLSerialization.cpp
+++ b/clang-tools-extra/clangd/index/YAMLSerialization.cpp
@@ -27,6 +27,7 @@
 #include "llvm/Support/YAMLTraits.h"
 #include "llvm/Support/raw_ostream.h"
 #include <cstdint>
+#include <optional>
 
 namespace {
 struct YIncludeHeaderWithReferences;
diff --git a/clang-tools-extra/clangd/index/dex/Dex.cpp b/clang-tools-extra/clangd/index/dex/Dex.cpp
index c66e7f0d936cee..0e94f59187de6d 100644
--- a/clang-tools-extra/clangd/index/dex/Dex.cpp
+++ b/clang-tools-extra/clangd/index/dex/Dex.cpp
@@ -23,6 +23,7 @@
 #include "llvm/Support/Path.h"
 #include "llvm/Support/ScopedPrinter.h"
 #include <algorithm>
+#include <optional>
 #include <queue>
 #include <utility>
 #include <vector>
diff --git a/clang-tools-extra/clangd/index/dex/dexp/Dexp.cpp b/clang-tools-extra/clangd/index/dex/dexp/Dexp.cpp
index 7bbcba33983357..763382204dc278 100644
--- a/clang-tools-extra/clangd/index/dex/dexp/Dexp.cpp
+++ b/clang-tools-extra/clangd/index/dex/dexp/Dexp.cpp
@@ -21,6 +21,7 @@
 #include "llvm/LineEditor/LineEditor.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Signals.h"
+#include <optional>
 
 namespace clang {
 namespace clangd {
diff --git a/clang-tools-extra/clangd/index/remote/server/Server.cpp b/clang-tools-extra/clangd/index/remote/server/Server.cpp
index 016ae728d040a6..5d2c82e2c86ad0 100644
--- a/clang-tools-extra/clangd/index/remote/server/Server.cpp
+++ b/clang-tools-extra/clangd/index/remote/server/Server.cpp
@@ -36,6 +36,7 @@
 #include <grpc++/grpc++.h>
 #include <grpc++/health_check_service_interface.h>
 #include <memory>
+#include <optional>
 #include <string>
 #include <thread>
 #include <utility>
diff --git a/clang-tools-extra/clangd/refactor/InsertionPoint.cpp b/clang-tools-extra/clangd/refactor/InsertionPoint.cpp
index 3158863cbb3c96..ff17ddd420b7b2 100644
--- a/clang-tools-extra/clangd/refactor/InsertionPoint.cpp
+++ b/clang-tools-extra/clangd/refactor/InsertionPoint.cpp
@@ -13,6 +13,7 @@
 #include "clang/AST/DeclObjC.h"
 #include "clang/AST/DeclTemplate.h"
 #include "clang/Basic/SourceManager.h"
+#include <optional>
 
 namespace clang {
 namespace clangd {
diff --git a/clang-tools-extra/clangd/refactor/Rename.cpp b/clang-tools-extra/clangd/refactor/Rename.cpp
index 5145ba4811adfc..afddab0073580c 100644
--- a/clang-tools-extra/clangd/refactor/Rename.cpp
+++ b/clang-tools-extra/clangd/refactor/Rename.cpp
@@ -33,6 +33,7 @@
 #include "llvm/Support/FormatVariadic.h"
 #include "llvm/Support/JSON.h"
 #include <algorithm>
+#include <optional>
 
 namespace clang {
 namespace clangd {
diff --git a/clang-tools-extra/clangd/refactor/Rename.h b/clang-tools-extra/clangd/refactor/Rename.h
index c10aa5a3ad20d4..6b917d56118012 100644
--- a/clang-tools-extra/clangd/refactor/Rename.h
+++ b/clang-tools-extra/clangd/refactor/Rename.h
@@ -13,6 +13,7 @@
 #include "SourceCode.h"
 #include "clang/Basic/LangOptions.h"
 #include "llvm/Support/Error.h"
+#include <optional>
 
 namespace clang {
 namespace clangd {
diff --git a/clang-tools-extra/clangd/refactor/Tweak.h b/clang-tools-extra/clangd/refactor/Tweak.h
index 5e7b77fcba8421..f91faf2aedcff4 100644
--- a/clang-tools-extra/clangd/refactor/Tweak.h
+++ b/clang-tools-extra/clangd/refactor/Tweak.h
@@ -28,6 +28,7 @@
 #include "llvm/ADT/Optional.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Support/Error.h"
+#include <optional>
 #include <string>
 
 namespace clang {
diff --git a/clang-tools-extra/clangd/refactor/tweaks/DefineInline.cpp b/clang-tools-extra/clangd/refactor/tweaks/DefineInline.cpp
index 8c2bf9f8eaf205..410dec0b910021 100644
--- a/clang-tools-extra/clangd/refactor/tweaks/DefineInline.cpp
+++ b/clang-tools-extra/clangd/refactor/tweaks/DefineInline.cpp
@@ -39,6 +39,7 @@
 #include "llvm/Support/Error.h"
 #include "llvm/Support/raw_ostream.h"
 #include <cstddef>
+#include <optional>
 #include <set>
 #include <string>
 #include <unordered_map>
diff --git a/clang-tools-extra/clangd/refactor/tweaks/DefineOutline.cpp b/clang-tools-extra/clangd/refactor/tweaks/DefineOutline.cpp
index 87890b9a4b0b33..1e09da9aa20b36 100644
--- a/clang-tools-extra/clangd/refactor/tweaks/DefineOutline.cpp
+++ b/clang-tools-extra/clangd/refactor/tweaks/DefineOutline.cpp
@@ -33,6 +33,7 @@
 #include "llvm/Support/Casting.h"
 #include "llvm/Support/Error.h"
 #include <cstddef>
+#include <optional>
 #include <string>
 
 namespace clang {
diff --git a/clang-tools-extra/clangd/refactor/tweaks/DumpAST.cpp b/clang-tools-extra/clangd/refactor/tweaks/DumpAST.cpp
index f2ae97c080693a..7a89ce7dc3cf51 100644
--- a/clang-tools-extra/clangd/refactor/tweaks/DumpAST.cpp
+++ b/clang-tools-extra/clangd/refactor/tweaks/DumpAST.cpp
@@ -16,6 +16,7 @@
 #include "llvm/Support/FormatVariadic.h"
 #include "llvm/Support/ScopedPrinter.h"
 #include "llvm/Support/raw_ostream.h"
+#include <optional>
 
 namespace clang {
 namespace clangd {
diff --git a/clang-tools-extra/clangd/refactor/tweaks/ExpandAutoType.cpp b/clang-tools-extra/clangd/refactor/tweaks/ExpandAutoType.cpp
index 04f4a2c8fdb78f..aabaed045c3d26 100644
--- a/clang-tools-extra/clangd/refactor/tweaks/ExpandAutoType.cpp
+++ b/clang-tools-extra/clangd/refactor/tweaks/ExpandAutoType.cpp
@@ -16,6 +16,7 @@
 #include <AST.h>
 #include <climits>
 #include <memory>
+#include <optional>
 #include <string>
 
 namespace clang {
diff --git a/clang-tools-extra/clangd/refactor/tweaks/ExtractFunction.cpp b/clang-tools-extra/clangd/refactor/tweaks/ExtractFunction.cpp
index c645859175fbff..a259deb0a91505 100644
--- a/clang-tools-extra/clangd/refactor/tweaks/ExtractFunction.cpp
+++ b/clang-tools-extra/clangd/refactor/tweaks/ExtractFunction.cpp
@@ -72,6 +72,7 @@
 #include "llvm/Support/Casting.h"
 #include "llvm/Support/Error.h"
 #include "llvm/Support/raw_os_ostream.h"
+#include <optional>
 
 namespace clang {
 namespace clangd {
diff --git a/clang-tools-extra/clangd/refactor/tweaks/ObjCMemberwiseInitializer.cpp b/clang-tools-extra/clangd/refactor/tweaks/ObjCMemberwiseInitializer.cpp
index 3fb9ac52ee3265..dbaf2a5d5c36a0 100644
--- a/clang-tools-extra/clangd/refactor/tweaks/ObjCMemberwiseInitializer.cpp
+++ b/clang-tools-extra/clangd/refactor/tweaks/ObjCMemberwiseInitializer.cpp
@@ -23,6 +23,7 @@
 #include "llvm/ADT/iterator_range.h"
 #include "llvm/Support/Casting.h"
 #include "llvm/Support/Error.h"
+#include <optional>
 
 namespace clang {
 namespace clangd {
diff --git a/clang-tools-extra/clangd/refactor/tweaks/RemoveUsingNamespace.cpp b/clang-tools-extra/clangd/refactor/tweaks/RemoveUsingNamespace.cpp
index ec02beb7e46f9f..51d299ee63def2 100644
--- a/clang-tools-extra/clangd/refactor/tweaks/RemoveUsingNamespace.cpp
+++ b/clang-tools-extra/clangd/refactor/tweaks/RemoveUsingNamespace.cpp
@@ -16,6 +16,7 @@
 #include "clang/AST/RecursiveASTVisitor.h"
 #include "clang/Basic/SourceLocation.h"
 #include "clang/Tooling/Core/Replacement.h"
+#include <optional>
 
 namespace clang {
 namespace clangd {
diff --git a/clang-tools-extra/clangd/tool/Check.cpp b/clang-tools-extra/clangd/tool/Check.cpp
index f2677d378ffcc8..3250571d4bce0c 100644
--- a/clang-tools-extra/clangd/tool/Check.cpp
+++ b/clang-tools-extra/clangd/tool/Check.cpp
@@ -54,6 +54,7 @@
 #include "llvm/ADT/Optional.h"
 #include "llvm/Support/Path.h"
 #include "llvm/Support/Process.h"
+#include <optional>
 
 namespace clang {
 namespace clangd {
diff --git a/clang-tools-extra/clangd/tool/ClangdMain.cpp b/clang-tools-extra/clangd/tool/ClangdMain.cpp
index 3975ae967f9085..fa6bda1c6d1ed5 100644
--- a/clang-tools-extra/clangd/tool/ClangdMain.cpp
+++ b/clang-tools-extra/clangd/tool/ClangdMain.cpp
@@ -44,6 +44,7 @@
 #include <cstdlib>
 #include <memory>
 #include <mutex>
+#include <optional>
 #include <string>
 #include <thread>
 #include <utility>
diff --git a/clang-tools-extra/clangd/unittests/ClangdLSPServerTests.cpp b/clang-tools-extra/clangd/unittests/ClangdLSPServerTests.cpp
index c3ad1b8cfb6662..a9a30eac436824 100644
--- a/clang-tools-extra/clangd/unittests/ClangdLSPServerTests.cpp
+++ b/clang-tools-extra/clangd/unittests/ClangdLSPServerTests.cpp
@@ -20,6 +20,7 @@
 #include "llvm/Testing/Support/SupportHelpers.h"
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
+#include <optional>
 
 namespace clang {
 namespace clangd {
diff --git a/clang-tools-extra/clangd/unittests/ClangdTests.cpp b/clang-tools-extra/clangd/unittests/ClangdTests.cpp
index 226fbad649b2af..05630629009c31 100644
--- a/clang-tools-extra/clangd/unittests/ClangdTests.cpp
+++ b/clang-tools-extra/clangd/unittests/ClangdTests.cpp
@@ -40,6 +40,7 @@
 #include <algorithm>
 #include <chrono>
 #include <iostream>
+#include <optional>
 #include <random>
 #include <string>
 #include <thread>
diff --git a/clang-tools-extra/clangd/unittests/ConfigCompileTests.cpp b/clang-tools-extra/clangd/unittests/ConfigCompileTests.cpp
index 1c87cea3291692..8d434a2793e2e6 100644
--- a/clang-tools-extra/clangd/unittests/ConfigCompileTests.cpp
+++ b/clang-tools-extra/clangd/unittests/ConfigCompileTests.cpp
@@ -19,6 +19,7 @@
 #include "llvm/Support/SourceMgr.h"
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
+#include <optional>
 #include <string>
 
 namespace clang {
diff --git a/clang-tools-extra/clangd/unittests/ConfigTesting.h b/clang-tools-extra/clangd/unittests/ConfigTesting.h
index f31a9c0591a46a..c06a0612767333 100644
--- a/clang-tools-extra/clangd/unittests/ConfigTesting.h
+++ b/clang-tools-extra/clangd/unittests/ConfigTesting.h
@@ -14,6 +14,7 @@
 #include "llvm/Support/SourceMgr.h"
 #include "gmock/gmock.h"
 #include <functional>
+#include <optional>
 
 namespace clang {
 namespace clangd {
diff --git a/clang-tools-extra/clangd/unittests/ExpectedTypeTest.cpp b/clang-tools-extra/clangd/unittests/ExpectedTypeTest.cpp
index c52413a12d501f..839f4c8e57a56e 100644
--- a/clang-tools-extra/clangd/unittests/ExpectedTypeTest.cpp
+++ b/clang-tools-extra/clangd/unittests/ExpectedTypeTest.cpp
@@ -14,6 +14,7 @@
 #include "llvm/ADT/StringRef.h"
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
+#include <optional>
 
 namespace clang {
 namespace clangd {
diff --git a/clang-tools-extra/clangd/unittests/GlobalCompilationDatabaseTests.cpp b/clang-tools-extra/clangd/unittests/GlobalCompilationDatabaseTests.cpp
index 2d4cddeb86709a..71bcb1234ba885 100644
--- a/clang-tools-extra/clangd/unittests/GlobalCompilationDatabaseTests.cpp
+++ b/clang-tools-extra/clangd/unittests/GlobalCompilationDatabaseTests.cpp
@@ -24,6 +24,7 @@
 #include "gtest/gtest.h"
 #include <chrono>
 #include <fstream>
+#include <optional>
 #include <string>
 
 namespace clang {
diff --git a/clang-tools-extra/clangd/unittests/HeaderSourceSwitchTests.cpp b/clang-tools-extra/clangd/unittests/HeaderSourceSwitchTests.cpp
index 4a61ada1dc7592..f6bc9a6248cfaa 100644
--- a/clang-tools-extra/clangd/unittests/HeaderSourceSwitchTests.cpp
+++ b/clang-tools-extra/clangd/unittests/HeaderSourceSwitchTests.cpp
@@ -16,6 +16,7 @@
 #include "llvm/Testing/Support/SupportHelpers.h"
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
+#include <optional>
 
 namespace clang {
 namespace clangd {
diff --git a/clang-tools-extra/clangd/unittests/HeadersTests.cpp b/clang-tools-extra/clangd/unittests/HeadersTests.cpp
index 66caa5ebab95f0..b14a14f0528b3a 100644
--- a/clang-tools-extra/clangd/unittests/HeadersTests.cpp
+++ b/clang-tools-extra/clangd/unittests/HeadersTests.cpp
@@ -24,6 +24,7 @@
 #include "llvm/Testing/Support/Error.h"
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
+#include <optional>
 
 namespace clang {
 namespace clangd {
diff --git a/clang-tools-extra/clangd/unittests/LSPBinderTests.cpp b/clang-tools-extra/clangd/unittests/LSPBinderTests.cpp
index 97a4316928a8cb..b23c00edc99ea0 100644
--- a/clang-tools-extra/clangd/unittests/LSPBinderTests.cpp
+++ b/clang-tools-extra/clangd/unittests/LSPBinderTests.cpp
@@ -10,6 +10,7 @@
 #include "llvm/Testing/Support/Error.h"
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
+#include <optional>
 
 namespace clang {
 namespace clangd {
diff --git a/clang-tools-extra/clangd/unittests/LSPClient.cpp b/clang-tools-extra/clangd/unittests/LSPClient.cpp
index aaadc62e68f358..027bf57a8a0492 100644
--- a/clang-tools-extra/clangd/unittests/LSPClient.cpp
+++ b/clang-tools-extra/clangd/unittests/LSPClient.cpp
@@ -16,6 +16,7 @@
 #include "llvm/Support/raw_ostream.h"
 #include "gtest/gtest.h"
 #include <condition_variable>
+#include <optional>
 #include <queue>
 
 namespace clang {
diff --git a/clang-tools-extra/clangd/unittests/PreambleTests.cpp b/clang-tools-extra/clangd/unittests/PreambleTests.cpp
index f38e297049a320..eb071e39c41d9c 100644
--- a/clang-tools-extra/clangd/unittests/PreambleTests.cpp
+++ b/clang-tools-extra/clangd/unittests/PreambleTests.cpp
@@ -25,6 +25,7 @@
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
 #include <memory>
+#include <optional>
 #include <string>
 #include <vector>
 
diff --git a/clang-tools-extra/clangd/unittests/SourceCodeTests.cpp b/clang-tools-extra/clangd/unittests/SourceCodeTests.cpp
index 459b4dbb93611e..eb5f60c3b93527 100644
--- a/clang-tools-extra/clangd/unittests/SourceCodeTests.cpp
+++ b/clang-tools-extra/clangd/unittests/SourceCodeTests.cpp
@@ -19,6 +19,7 @@
 #include "llvm/Testing/Support/Error.h"
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
+#include <optional>
 #include <tuple>
 
 namespace clang {
diff --git a/clang-tools-extra/clangd/unittests/SymbolCollectorTests.cpp b/clang-tools-extra/clangd/unittests/SymbolCollectorTests.cpp
index 27854004094e05..08523edfc558b0 100644
--- a/clang-tools-extra/clangd/unittests/SymbolCollectorTests.cpp
+++ b/clang-tools-extra/clangd/unittests/SymbolCollectorTests.cpp
@@ -26,6 +26,7 @@
 #include "gtest/gtest.h"
 
 #include <memory>
+#include <optional>
 #include <string>
 
 namespace clang {
diff --git a/clang-tools-extra/clangd/unittests/SymbolInfoTests.cpp b/clang-tools-extra/clangd/unittests/SymbolInfoTests.cpp
index f68f87fef1560f..ad76d7dcf55475 100644
--- a/clang-tools-extra/clangd/unittests/SymbolInfoTests.cpp
+++ b/clang-tools-extra/clangd/unittests/SymbolInfoTests.cpp
@@ -11,6 +11,7 @@
 #include "XRefs.h"
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
+#include <optional>
 
 namespace clang {
 namespace clangd {
diff --git a/clang-tools-extra/clangd/unittests/SyncAPI.cpp b/clang-tools-extra/clangd/unittests/SyncAPI.cpp
index 52f47b01b4e1b4..2c4fde7d189534 100644
--- a/clang-tools-extra/clangd/unittests/SyncAPI.cpp
+++ b/clang-tools-extra/clangd/unittests/SyncAPI.cpp
@@ -9,6 +9,7 @@
 #include "SyncAPI.h"
 #include "Protocol.h"
 #include "index/Index.h"
+#include <optional>
 
 namespace clang {
 namespace clangd {
diff --git a/clang-tools-extra/clangd/unittests/SyncAPI.h b/clang-tools-extra/clangd/unittests/SyncAPI.h
index 46202239105b12..6b4e3fc608e971 100644
--- a/clang-tools-extra/clangd/unittests/SyncAPI.h
+++ b/clang-tools-extra/clangd/unittests/SyncAPI.h
@@ -18,6 +18,7 @@
 #include "ClangdServer.h"
 #include "Protocol.h"
 #include "index/Index.h"
+#include <optional>
 
 namespace clang {
 namespace clangd {
diff --git a/clang-tools-extra/clangd/unittests/TUSchedulerTests.cpp b/clang-tools-extra/clangd/unittests/TUSchedulerTests.cpp
index 67d6fd2cbe5600..c7e28a0e213a61 100644
--- a/clang-tools-extra/clangd/unittests/TUSchedulerTests.cpp
+++ b/clang-tools-extra/clangd/unittests/TUSchedulerTests.cpp
@@ -36,6 +36,7 @@
 #include <chrono>
 #include <cstdint>
 #include <memory>
+#include <optional>
 #include <string>
 #include <utility>
 
diff --git a/clang-tools-extra/clangd/unittests/TestFS.cpp b/clang-tools-extra/clangd/unittests/TestFS.cpp
index b820bc7d02b355..be26a6ccf25f3b 100644
--- a/clang-tools-extra/clangd/unittests/TestFS.cpp
+++ b/clang-tools-extra/clangd/unittests/TestFS.cpp
@@ -13,6 +13,7 @@
 #include "llvm/ADT/Optional.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Support/Path.h"
+#include <optional>
 
 namespace clang {
 namespace clangd {
diff --git a/clang-tools-extra/clangd/unittests/TestFS.h b/clang-tools-extra/clangd/unittests/TestFS.h
index 7d3d4d3d03ddaa..3e4ac3bab1c924 100644
--- a/clang-tools-extra/clangd/unittests/TestFS.h
+++ b/clang-tools-extra/clangd/unittests/TestFS.h
@@ -18,6 +18,7 @@
 #include "llvm/ADT/Optional.h"
 #include "llvm/Support/Path.h"
 #include "llvm/Support/VirtualFileSystem.h"
+#include <optional>
 
 namespace clang {
 namespace clangd {
diff --git a/clang-tools-extra/clangd/unittests/TestWorkspace.cpp b/clang-tools-extra/clangd/unittests/TestWorkspace.cpp
index bca24fca3a04cd..662eef63d25a6f 100644
--- a/clang-tools-extra/clangd/unittests/TestWorkspace.cpp
+++ b/clang-tools-extra/clangd/unittests/TestWorkspace.cpp
@@ -9,6 +9,7 @@
 #include "TestWorkspace.h"
 #include "index/FileIndex.h"
 #include "gtest/gtest.h"
+#include <optional>
 
 namespace clang {
 namespace clangd {
diff --git a/clang-tools-extra/clangd/unittests/TestWorkspace.h b/clang-tools-extra/clangd/unittests/TestWorkspace.h
index 4467c7efb74a41..bc6aee1c58d1d3 100644
--- a/clang-tools-extra/clangd/unittests/TestWorkspace.h
+++ b/clang-tools-extra/clangd/unittests/TestWorkspace.h
@@ -19,6 +19,7 @@
 #include "TestTU.h"
 #include "index/Index.h"
 #include "llvm/ADT/StringRef.h"
+#include <optional>
 #include <string>
 #include <vector>
 
diff --git a/clang-tools-extra/clangd/unittests/XRefsTests.cpp b/clang-tools-extra/clangd/unittests/XRefsTests.cpp
index 1a25b5d69d7ac0..ae19656f6f9a29 100644
--- a/clang-tools-extra/clangd/unittests/XRefsTests.cpp
+++ b/clang-tools-extra/clangd/unittests/XRefsTests.cpp
@@ -24,6 +24,7 @@
 #include "llvm/Support/ScopedPrinter.h"
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
+#include <optional>
 #include <string>
 #include <vector>
 
diff --git a/clang-tools-extra/clangd/unittests/support/FileCacheTests.cpp b/clang-tools-extra/clangd/unittests/support/FileCacheTests.cpp
index 8d2bc4d15d7b9b..133b83ba93fd1f 100644
--- a/clang-tools-extra/clangd/unittests/support/FileCacheTests.cpp
+++ b/clang-tools-extra/clangd/unittests/support/FileCacheTests.cpp
@@ -13,6 +13,7 @@
 #include "gtest/gtest.h"
 #include <atomic>
 #include <chrono>
+#include <optional>
 
 namespace clang {
 namespace clangd {
diff --git a/clang-tools-extra/clangd/unittests/tweaks/TweakTesting.cpp b/clang-tools-extra/clangd/unittests/tweaks/TweakTesting.cpp
index 59885cec057032..12836d0926e231 100644
--- a/clang-tools-extra/clangd/unittests/tweaks/TweakTesting.cpp
+++ b/clang-tools-extra/clangd/unittests/tweaks/TweakTesting.cpp
@@ -14,6 +14,7 @@
 #include "llvm/Support/Error.h"
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
+#include <optional>
 #include <string>
 
 namespace clang {
diff --git a/clang-tools-extra/clangd/xpc/XPCTransport.cpp b/clang-tools-extra/clangd/xpc/XPCTransport.cpp
index 9c43647c3c767a..dac8e29efae1d9 100644
--- a/clang-tools-extra/clangd/xpc/XPCTransport.cpp
+++ b/clang-tools-extra/clangd/xpc/XPCTransport.cpp
@@ -11,6 +11,7 @@
 #include "support/Logger.h"
 #include "llvm/Support/Errno.h"
 
+#include <optional>
 #include <xpc/xpc.h>
 
 using namespace llvm;
diff --git a/clang-tools-extra/pseudo/include/clang-pseudo/DirectiveTree.h b/clang-tools-extra/pseudo/include/clang-pseudo/DirectiveTree.h
index e9af9a5bb04fdd..e8f4240b8fa3e2 100644
--- a/clang-tools-extra/pseudo/include/clang-pseudo/DirectiveTree.h
+++ b/clang-tools-extra/pseudo/include/clang-pseudo/DirectiveTree.h
@@ -30,6 +30,7 @@
 
 #include "clang-pseudo/Token.h"
 #include "clang/Basic/TokenKinds.h"
+#include <optional>
 #include <variant>
 #include <vector>
 
diff --git a/clang-tools-extra/pseudo/lib/DirectiveTree.cpp b/clang-tools-extra/pseudo/lib/DirectiveTree.cpp
index 4835fc24071a9d..4e866815e63be8 100644
--- a/clang-tools-extra/pseudo/lib/DirectiveTree.cpp
+++ b/clang-tools-extra/pseudo/lib/DirectiveTree.cpp
@@ -10,6 +10,7 @@
 #include "clang/Basic/IdentifierTable.h"
 #include "clang/Basic/TokenKinds.h"
 #include "llvm/Support/FormatVariadic.h"
+#include <optional>
 #include <variant>
 
 namespace clang {
diff --git a/clang-tools-extra/pseudo/lib/Forest.cpp b/clang-tools-extra/pseudo/lib/Forest.cpp
index 78e7983d28bcad..e6b2d2ec0f9029 100644
--- a/clang-tools-extra/pseudo/lib/Forest.cpp
+++ b/clang-tools-extra/pseudo/lib/Forest.cpp
@@ -11,6 +11,7 @@
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/Support/FormatVariadic.h"
+#include <optional>
 
 namespace clang {
 namespace pseudo {
diff --git a/clang-tools-extra/pseudo/lib/GLR.cpp b/clang-tools-extra/pseudo/lib/GLR.cpp
index e49cbc40efce00..a4169dd96f4aaa 100644
--- a/clang-tools-extra/pseudo/lib/GLR.cpp
+++ b/clang-tools-extra/pseudo/lib/GLR.cpp
@@ -19,6 +19,7 @@
 #include "llvm/Support/FormatVariadic.h"
 #include <algorithm>
 #include <memory>
+#include <optional>
 #include <queue>
 
 #define DEBUG_TYPE "GLR.cpp"
diff --git a/clang-tools-extra/pseudo/tool/ClangPseudo.cpp b/clang-tools-extra/pseudo/tool/ClangPseudo.cpp
index c6d06739e7b0f8..c22ea171c96cc5 100644
--- a/clang-tools-extra/pseudo/tool/ClangPseudo.cpp
+++ b/clang-tools-extra/pseudo/tool/ClangPseudo.cpp
@@ -24,6 +24,7 @@
 #include "llvm/Support/FormatVariadic.h"
 #include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/Signals.h"
+#include <optional>
 
 using clang::pseudo::ForestNode;
 using clang::pseudo::Token;
diff --git a/clang-tools-extra/unittests/clang-tidy/AddConstTest.cpp b/clang-tools-extra/unittests/clang-tidy/AddConstTest.cpp
index 31a444f2e4ec9c..437d9b4df8fe04 100644
--- a/clang-tools-extra/unittests/clang-tidy/AddConstTest.cpp
+++ b/clang-tools-extra/unittests/clang-tidy/AddConstTest.cpp
@@ -5,6 +5,7 @@
 #include "clang/ASTMatchers/ASTMatchers.h"
 #include "clang/Tooling/Tooling.h"
 #include "gtest/gtest.h"
+#include <optional>
 
 namespace clang {
 namespace tidy {
diff --git a/clang-tools-extra/unittests/clang-tidy/ClangTidyOptionsTest.cpp b/clang-tools-extra/unittests/clang-tidy/ClangTidyOptionsTest.cpp
index 5dcec035c476a5..d861e86284b3af 100644
--- a/clang-tools-extra/unittests/clang-tidy/ClangTidyOptionsTest.cpp
+++ b/clang-tools-extra/unittests/clang-tidy/ClangTidyOptionsTest.cpp
@@ -6,6 +6,7 @@
 #include "llvm/Testing/Support/Annotations.h"
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
+#include <optional>
 
 namespace clang {
 namespace tidy {
diff --git a/clang-tools-extra/unittests/clang-tidy/LLVMModuleTest.cpp b/clang-tools-extra/unittests/clang-tidy/LLVMModuleTest.cpp
index 5394e75268099e..964f5f74a2bf14 100644
--- a/clang-tools-extra/unittests/clang-tidy/LLVMModuleTest.cpp
+++ b/clang-tools-extra/unittests/clang-tidy/LLVMModuleTest.cpp
@@ -5,6 +5,7 @@
 #include "llvm/HeaderGuardCheck.h"
 #include "llvm/IncludeOrderCheck.h"
 #include "gtest/gtest.h"
+#include <optional>
 
 using namespace clang::tidy::llvm_check;
 
diff --git a/clang-tools-extra/unittests/clang-tidy/TransformerClangTidyCheckTest.cpp b/clang-tools-extra/unittests/clang-tidy/TransformerClangTidyCheckTest.cpp
index e1ebad73bb73d0..873259414b74f9 100644
--- a/clang-tools-extra/unittests/clang-tidy/TransformerClangTidyCheckTest.cpp
+++ b/clang-tools-extra/unittests/clang-tidy/TransformerClangTidyCheckTest.cpp
@@ -15,6 +15,7 @@
 #include "clang/Tooling/Transformer/Transformer.h"
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
+#include <optional>
 
 namespace clang {
 namespace tidy {