[clang] Use std::nullopt instead of None in comments (NFC)

This is part of an effort to migrate from llvm::Optional to
std::optional:

https://discourse.llvm.org/t/deprecating-llvm-optional-x-hasvalue-getvalue-getvalueor/63716

clang/include/clang/APINotes/Types.h

@@ -215,7 +215,8 @@ public:
   /// Determine the default nullability for properties and methods of this
   /// class.
   ///
-  /// eturns the default nullability, if implied, or None if there is no
+  /// Returns the default nullability, if implied, or std::nullopt if there is
+  /// none.
   llvm::Optional<NullabilityKind> getDefaultNullability() const {
     return HasDefaultNullability
                ? llvm::Optional<NullabilityKind>(

clang/include/clang/AST/CharUnits.h

@@ -183,7 +183,8 @@ namespace clang {
       llvm::Align getAsAlign() const { return llvm::Align(Quantity); }
 
       /// getAsMaybeAlign - Returns Quantity as a valid llvm::Align or
-      /// llvm::None, Beware llvm::MaybeAlign assumes power of two 8-bit bytes.
+      /// std::nullopt, Beware llvm::MaybeAlign assumes power of two 8-bit
+      /// bytes.
       llvm::MaybeAlign getAsMaybeAlign() const {
         return llvm::MaybeAlign(Quantity);
       }

clang/include/clang/ASTMatchers/ASTMatchersInternal.h

@@ -536,7 +536,7 @@ public:
   /// Returns the \c TraversalKind respected by calls to `match()`, if any.
   ///
   /// Most matchers will not have a traversal kind set, instead relying on the
-  /// surrounding context. For those, \c llvm::None is returned.
+  /// surrounding context. For those, \c std::nullopt is returned.
   llvm::Optional<clang::TraversalKind> getTraversalKind() const {
     return Implementation->TraversalKind();
   }

clang/include/clang/Analysis/FlowSensitive/TypeErasedDataflowAnalysis.h

@@ -135,7 +135,7 @@ struct TypeErasedDataflowAnalysisState {
 ///
 ///   All predecessors of `Block` except those with loop back edges must have
 ///   already been transferred. States in `BlockStates` that are set to
-///   `llvm::None` represent basic blocks that are not evaluated yet.
+///   `std::nullopt` represent basic blocks that are not evaluated yet.
 TypeErasedDataflowAnalysisState transferBlock(
     const ControlFlowContext &CFCtx,
     llvm::ArrayRef<llvm::Optional<TypeErasedDataflowAnalysisState>> BlockStates,

clang/include/clang/Analysis/RetainSummaryManager.h

@@ -719,8 +719,8 @@ private:
   /// type for functions/methods) @c QT has any of the given attributes,
   /// provided they pass necessary validation checks AND tracking the given
   /// attribute is enabled.
-  /// Returns the object kind corresponding to the present attribute, or None,
-  /// if none of the specified attributes are present.
+  /// Returns the object kind corresponding to the present attribute, or
+  /// std::nullopt, if none of the specified attributes are present.
   /// Crashes if passed an attribute which is not explicitly handled.
   template <class T>
   Optional<ObjKind> hasAnyEnabledAttrOf(const Decl *D, QualType QT);

clang/include/clang/Basic/DarwinSDKInfo.h

@@ -99,7 +99,7 @@ public:
 
     /// Returns the mapped key, or the appropriate Minimum / MaximumValue if
     /// they key is outside of the mapping bounds. If they key isn't mapped, but
-    /// within the minimum and maximum bounds, None is returned.
+    /// within the minimum and maximum bounds, std::nullopt is returned.
     std::optional<VersionTuple>
     map(const VersionTuple &Key, const VersionTuple &MinimumValue,
         std::optional<VersionTuple> MaximumValue) const;

clang/include/clang/Basic/TargetID.h

@@ -31,9 +31,9 @@ llvm::StringRef getProcessorFromTargetID(const llvm::Triple &T,
                                          llvm::StringRef OffloadArch);
 
 /// Parse a target ID to get processor and feature map.
-/// Returns canonicalized processor name or None if the target ID is invalid.
-/// Returns target ID features in \p FeatureMap if it is not null pointer.
-/// This function assumes \p OffloadArch is a valid target ID.
+/// Returns canonicalized processor name or std::nullopt if the target ID is
+/// invalid.  Returns target ID features in \p FeatureMap if it is not null
+/// pointer. This function assumes \p OffloadArch is a valid target ID.
 /// If the target ID contains feature+, map it to true.
 /// If the target ID contains feature-, map it to false.
 /// If the target ID does not contain a feature (default), do not map it.

clang/include/clang/Frontend/CommandLineSourceLoc.h

@@ -67,8 +67,8 @@ struct ParsedSourceRange {
   /// second element is the column.
   std::pair<unsigned, unsigned> End;
 
-  /// Returns a parsed source range from a string or None if the string is
-  /// invalid.
+  /// Returns a parsed source range from a string or std::nullopt if the string
+  /// is invalid.
   ///
   /// These source string has the following format:
   ///

clang/include/clang/StaticAnalyzer/Core/PathSensitive/CheckerHelpers.h

@@ -67,7 +67,8 @@ Nullability getNullabilityAnnotation(QualType Type);
 
 /// Try to parse the value of a defined preprocessor macro. We can only parse
 /// simple expressions that consist of an optional minus sign token and then a
-/// token for an integer. If we cannot parse the value then None is returned.
+/// token for an integer. If we cannot parse the value then std::nullopt is
+/// returned.
 llvm::Optional<int> tryExpandAsInteger(StringRef Macro, const Preprocessor &PP);
 
 class OperatorKind {

clang/include/clang/Tooling/Syntax/Tokens.h

@@ -204,7 +204,7 @@ public:
   /// Returns the subrange of spelled tokens corresponding to AST node spanning
   /// \p Expanded. This is the text that should be replaced if a refactoring
   /// were to rewrite the node. If \p Expanded is empty, the returned value is
-  /// llvm::None.
+  /// std::nullopt.
   ///
   /// Will fail if the expanded tokens do not correspond to a sequence of
   /// spelled tokens. E.g. for the following example:

clang/lib/Analysis/FlowSensitive/TypeErasedDataflowAnalysis.cpp

@@ -210,7 +210,7 @@ struct AnalysisContext {
 ///
 ///   All predecessors of `Block` except those with loop back edges must have
 ///   already been transferred. States in `AC.BlockStates` that are set to
-///   `llvm::None` represent basic blocks that are not evaluated yet.
+///   `std::nullopt` represent basic blocks that are not evaluated yet.
 static TypeErasedDataflowAnalysisState
 computeBlockInputState(const CFGBlock &Block, AnalysisContext &AC) {
   llvm::DenseSet<const CFGBlock *> Preds;
@@ -479,7 +479,7 @@ runTypeErasedDataflowAnalysis(
     Worklist.enqueueSuccessors(Block);
   }
   // FIXME: Consider evaluating unreachable basic blocks (those that have a
-  // state set to `llvm::None` at this point) to also analyze dead code.
+  // state set to `std::nullopt` at this point) to also analyze dead code.
 
   if (PostVisitCFG) {
     for (const CFGBlock *Block : CFCtx.getCFG()) {

clang/lib/Driver/ToolChains/Cuda.cpp

@@ -78,7 +78,7 @@ CudaVersion getCudaVersion(uint32_t raw_version) {
 
 CudaVersion parseCudaHFile(llvm::StringRef Input) {
   // Helper lambda which skips the words if the line starts with them or returns
-  // None otherwise.
+  // std::nullopt otherwise.
   auto StartsWithWords =
       [](llvm::StringRef Line,
          const SmallVector<StringRef, 3> words) -> std::optional<StringRef> {

clang/lib/Format/ContinuationIndenter.cpp

@@ -146,9 +146,9 @@ static bool opensProtoMessageField(const FormatToken &LessTok,
            (LessTok.Previous && LessTok.Previous->is(tok::equal))));
 }
 
-// Returns the delimiter of a raw string literal, or None if TokenText is not
-// the text of a raw string literal. The delimiter could be the empty string.
-// For example, the delimiter of R"deli(cont)deli" is deli.
+// Returns the delimiter of a raw string literal, or std::nullopt if TokenText
+// is not the text of a raw string literal. The delimiter could be the empty
+// string.  For example, the delimiter of R"deli(cont)deli" is deli.
 static llvm::Optional<StringRef> getRawStringDelimiter(StringRef TokenText) {
   if (TokenText.size() < 5 // The smallest raw string possible is 'R"()"'.
       || !TokenText.startswith("R\"") || !TokenText.endswith("\"")) {

clang/lib/StaticAnalyzer/Core/BugReporterVisitors.cpp

@@ -538,7 +538,7 @@ private:
   /// Dereferences fields up to a given recursion limit.
   /// Note that \p Vec is passed by value, leading to quadratic copying cost,
   /// but it's OK in practice since its length is limited to DEREFERENCE_LIMIT.
-  /// \return A chain fields leading to the region of interest or None.
+  /// \return A chain fields leading to the region of interest or std::nullopt.
   const Optional<RegionVector>
   findRegionOfInterestInRecord(const RecordDecl *RD, ProgramStateRef State,
                                const MemRegion *R, const RegionVector &Vec = {},
@@ -619,7 +619,7 @@ static bool potentiallyWritesIntoIvar(const Decl *Parent,
 /// Dereferences fields up to a given recursion limit.
 /// Note that \p Vec is passed by value, leading to quadratic copying cost,
 /// but it's OK in practice since its length is limited to DEREFERENCE_LIMIT.
-/// \return A chain fields leading to the region of interest or None.
+/// \return A chain fields leading to the region of interest or std::nullopt.
 const Optional<NoStoreFuncVisitor::RegionVector>
 NoStoreFuncVisitor::findRegionOfInterestInRecord(
     const RecordDecl *RD, ProgramStateRef State, const MemRegion *R,

clang/lib/StaticAnalyzer/Core/ExprEngine.cpp

@@ -2671,8 +2671,8 @@ bool ExprEngine::hasMoreIteration(ProgramStateRef State,
 }
 
 /// Split the state on whether there are any more iterations left for this loop.
-/// Returns a (HasMoreIteration, HasNoMoreIteration) pair, or None when the
-/// acquisition of the loop condition value failed.
+/// Returns a (HasMoreIteration, HasNoMoreIteration) pair, or std::nullopt when
+/// the acquisition of the loop condition value failed.
 static Optional<std::pair<ProgramStateRef, ProgramStateRef>>
 assumeCondition(const Stmt *Condition, ExplodedNode *N) {
   ProgramStateRef State = N->getState();

clang/lib/StaticAnalyzer/Core/RangeConstraintManager.cpp

@@ -1164,7 +1164,8 @@ template <class SecondTy, class... RestTy>
 
 /// Main generic intersect function.
 /// It intersects all of the given range sets.  If some of the given arguments
-/// don't hold a range set (nullptr or llvm::None), the function will skip them.
+/// don't hold a range set (nullptr or std::nullopt), the function will skip
+/// them.
 ///
 /// Available representations for the arguments are:
 ///   * RangeSet
@@ -1179,7 +1180,7 @@ template <class SecondTy, class... RestTy>
 /// simply RangeSet, in other cases we have to back off to Optional<RangeSet>.
 ///
 /// Please, prefer optional range sets to raw pointers.  If the last argument is
-/// a raw pointer and all previous arguments are None, it will cost one
+/// a raw pointer and all previous arguments are std::nullopt, it will cost one
 /// additional check to convert RangeSet * into Optional<RangeSet>.
 template <class HeadTy, class SecondTy, class... RestTy>
 [[nodiscard]] inline

clang/lib/Tooling/Transformer/Parsing.cpp

@@ -46,7 +46,7 @@ struct ParseState {
 };
 
 // Represents an intermediate result returned by a parsing function. Functions
-// that don't generate values should use `llvm::None`
+// that don't generate values should use `std::nullopt`
 template <typename ResultType> struct ParseProgress {
   ParseState State;
   // Intermediate result generated by the Parser.