[clang] [APINotes] Upstream Sema logic to apply API Notes to decls (PR #73017)

Egor Zhdan via cfe-commits cfe-commits at lists.llvm.org
Tue Nov 21 09:30:22 PST 2023


https://github.com/egorzhdan updated https://github.com/llvm/llvm-project/pull/73017

>From d7d8e8520681b6a71fda9848b18828cff8ed7415 Mon Sep 17 00:00:00 2001
From: Egor Zhdan <e_zhdan at apple.com>
Date: Mon, 20 Nov 2023 18:03:18 +0000
Subject: [PATCH 1/4] [APINotes] Upstream attributes that are created
 implicitly from APINotes

---
 clang/include/clang/Basic/Attr.td         | 46 ++++++++++++++++++++++-
 clang/lib/Sema/SemaDeclAttr.cpp           | 34 ++++++++++-------
 clang/lib/Serialization/ASTReaderDecl.cpp |  2 +
 clang/utils/TableGen/ClangAttrEmitter.cpp | 26 ++++++++++++-
 4 files changed, 92 insertions(+), 16 deletions(-)

diff --git a/clang/include/clang/Basic/Attr.td b/clang/include/clang/Basic/Attr.td
index c2fbdfc66c540d6..a9ad6c878306ad3 100644
--- a/clang/include/clang/Basic/Attr.td
+++ b/clang/include/clang/Basic/Attr.td
@@ -301,6 +301,9 @@ class VariadicEnumArgument<string name, string type, list<string> values,
   bit IsExternalType = isExternalType;
 }
 
+// Represents an attribute wrapped by another attribute.
+class AttrArgument<string name, bit opt = 0> : Argument<name, opt>;
+
 // This handles one spelling of an attribute.
 class Spelling<string name, string variety, int version = 1> {
   string Name = name;
@@ -2257,7 +2260,7 @@ def ObjCBridgeRelated : InheritableAttr {
 def NSErrorDomain : InheritableAttr {
   let Spellings = [GNU<"ns_error_domain">];
   let Subjects = SubjectList<[Enum], ErrorDiag>;
-  let Args = [DeclArgument<Var, "ErrorDomain">];
+  let Args = [IdentifierArgument<"ErrorDomain">];
   let Documentation = [NSErrorDomainDocs];
 }
 
@@ -2593,6 +2596,22 @@ def SwiftError : InheritableAttr {
   let Documentation = [SwiftErrorDocs];
 }
 
+def SwiftImportAsNonGeneric : InheritableAttr {
+  // This attribute has no spellings as it is only ever created implicitly
+  // from API notes.
+  let Spellings = [];
+  let SemaHandler = 0;
+  let Documentation = [InternalOnly];
+}
+
+def SwiftImportPropertyAsAccessors : InheritableAttr {
+  // This attribute has no spellings as it is only ever created implicitly
+  // from API notes.
+  let Spellings = [];
+  let SemaHandler = 0;
+  let Documentation = [InternalOnly];
+}
+
 def SwiftName : InheritableAttr {
   let Spellings = [GNU<"swift_name">];
   let Args = [StringArgument<"Name">];
@@ -2614,6 +2633,31 @@ def SwiftPrivate : InheritableAttr {
   let SimpleHandler = 1;
 }
 
+def SwiftVersioned : Attr {
+  // This attribute has no spellings as it is only ever created implicitly
+  // from API notes.
+  let Spellings = [];
+  let Args = [VersionArgument<"Version">, AttrArgument<"AttrToAdd">,
+              BoolArgument<"IsReplacedByActive">];
+  let SemaHandler = 0;
+  let Documentation = [InternalOnly];
+}
+
+def SwiftVersionedRemoval : Attr {
+  // This attribute has no spellings as it is only ever created implicitly
+  // from API notes.
+  let Spellings = [];
+  let Args = [VersionArgument<"Version">, UnsignedArgument<"RawKind">,
+              BoolArgument<"IsReplacedByActive">];
+  let SemaHandler = 0;
+  let Documentation = [InternalOnly];
+  let AdditionalMembers = [{
+    attr::Kind getAttrKindToRemove() const {
+      return static_cast<attr::Kind>(getRawKind());
+    }
+  }];
+}
+
 def NoDeref : TypeAttr {
   let Spellings = [Clang<"noderef">];
   let Documentation = [NoDerefDocs];
diff --git a/clang/lib/Sema/SemaDeclAttr.cpp b/clang/lib/Sema/SemaDeclAttr.cpp
index fd778793346f502..8552b28e51acd97 100644
--- a/clang/lib/Sema/SemaDeclAttr.cpp
+++ b/clang/lib/Sema/SemaDeclAttr.cpp
@@ -6210,29 +6210,35 @@ static void handleObjCRequiresSuperAttr(Sema &S, Decl *D,
   D->addAttr(::new (S.Context) ObjCRequiresSuperAttr(S.Context, Attrs));
 }
 
-static void handleNSErrorDomain(Sema &S, Decl *D, const ParsedAttr &AL) {
-  auto *E = AL.getArgAsExpr(0);
-  auto Loc = E ? E->getBeginLoc() : AL.getLoc();
-
-  auto *DRE = dyn_cast<DeclRefExpr>(AL.getArgAsExpr(0));
-  if (!DRE) {
-    S.Diag(Loc, diag::err_nserrordomain_invalid_decl) << 0;
+static void handleNSErrorDomain(Sema &S, Decl *D, const ParsedAttr &Attr) {
+  if (!isa<TagDecl>(D)) {
+    S.Diag(D->getBeginLoc(), diag::err_nserrordomain_invalid_decl) << 0;
     return;
   }
 
-  auto *VD = dyn_cast<VarDecl>(DRE->getDecl());
-  if (!VD) {
-    S.Diag(Loc, diag::err_nserrordomain_invalid_decl) << 1 << DRE->getDecl();
+  IdentifierLoc *IdentLoc =
+      Attr.isArgIdent(0) ? Attr.getArgAsIdent(0) : nullptr;
+  if (!IdentLoc || !IdentLoc->Ident) {
+    // Try to locate the argument directly.
+    SourceLocation Loc = Attr.getLoc();
+    if (Attr.isArgExpr(0) && Attr.getArgAsExpr(0))
+      Loc = Attr.getArgAsExpr(0)->getBeginLoc();
+
+    S.Diag(Loc, diag::err_nserrordomain_invalid_decl) << 0;
     return;
   }
 
-  if (!isNSStringType(VD->getType(), S.Context) &&
-      !isCFStringType(VD->getType(), S.Context)) {
-    S.Diag(Loc, diag::err_nserrordomain_wrong_type) << VD;
+  // Verify that the identifier is a valid decl in the C decl namespace.
+  LookupResult Result(S, DeclarationName(IdentLoc->Ident), SourceLocation(),
+                      Sema::LookupNameKind::LookupOrdinaryName);
+  if (!S.LookupName(Result, S.TUScope) || !Result.getAsSingle<VarDecl>()) {
+    S.Diag(IdentLoc->Loc, diag::err_nserrordomain_invalid_decl)
+        << 1 << IdentLoc->Ident;
     return;
   }
 
-  D->addAttr(::new (S.Context) NSErrorDomainAttr(S.Context, AL, VD));
+  D->addAttr(::new (S.Context)
+                 NSErrorDomainAttr(S.Context, Attr, IdentLoc->Ident));
 }
 
 static void handleObjCBridgeAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
diff --git a/clang/lib/Serialization/ASTReaderDecl.cpp b/clang/lib/Serialization/ASTReaderDecl.cpp
index 79817b3fb1ec3a0..5a8a1fa99d5a19d 100644
--- a/clang/lib/Serialization/ASTReaderDecl.cpp
+++ b/clang/lib/Serialization/ASTReaderDecl.cpp
@@ -3086,6 +3086,8 @@ class AttrReader {
 
   Expr *readExpr() { return Reader.readExpr(); }
 
+  Attr *readAttr() { return Reader.readAttr(); }
+
   std::string readString() {
     return Reader.readString();
   }
diff --git a/clang/utils/TableGen/ClangAttrEmitter.cpp b/clang/utils/TableGen/ClangAttrEmitter.cpp
index 4ec00573e8a9da8..096c1f7cf6a3700 100644
--- a/clang/utils/TableGen/ClangAttrEmitter.cpp
+++ b/clang/utils/TableGen/ClangAttrEmitter.cpp
@@ -1414,7 +1414,29 @@ namespace {
     }
   };
 
-} // end anonymous namespace
+  class AttrArgument : public SimpleArgument {
+  public:
+    AttrArgument(const Record &Arg, StringRef Attr)
+        : SimpleArgument(Arg, Attr, "Attr *") {}
+
+    void writePCHReadDecls(raw_ostream &OS) const override {
+      OS << "    Attr *" << getLowerName() << " = Record.readAttr();";
+    }
+
+    void writePCHWrite(raw_ostream &OS) const override {
+      OS << "    AddAttr(SA->get" << getUpperName() << "());";
+    }
+
+    void writeDump(raw_ostream &OS) const override {}
+
+    void writeDumpChildren(raw_ostream &OS) const override {
+      OS << "    Visit(SA->get" << getUpperName() << "());\n";
+    }
+
+    void writeHasChildren(raw_ostream &OS) const override { OS << "true"; }
+  };
+
+  } // end anonymous namespace
 
 static std::unique_ptr<Argument>
 createArgument(const Record &Arg, StringRef Attr,
@@ -1470,6 +1492,8 @@ createArgument(const Record &Arg, StringRef Attr,
     Ptr = std::make_unique<VariadicIdentifierArgument>(Arg, Attr);
   else if (ArgName == "VersionArgument")
     Ptr = std::make_unique<VersionArgument>(Arg, Attr);
+  else if (ArgName == "AttrArgument")
+    Ptr = std::make_unique<AttrArgument>(Arg, Attr);
   else if (ArgName == "OMPTraitInfoArgument")
     Ptr = std::make_unique<SimpleArgument>(Arg, Attr, "OMPTraitInfo *");
   else if (ArgName == "VariadicOMPInteropInfoArgument")

>From ec276f334ccdbc2f8b660d40cbff6a794beab8c7 Mon Sep 17 00:00:00 2001
From: Egor Zhdan <e_zhdan at apple.com>
Date: Tue, 21 Nov 2023 16:34:52 +0000
Subject: [PATCH 2/4] [APINotes] Upstream Parser support for API Notes

---
 .../clang/Basic/DiagnosticParseKinds.td       |  3 +
 clang/include/clang/Lex/Lexer.h               |  2 +-
 clang/include/clang/Parse/Parser.h            | 12 ++++
 clang/include/clang/Sema/Sema.h               |  4 ++
 clang/lib/Parse/ParseDecl.cpp                 | 65 +++++++++++++++++++
 clang/lib/Parse/Parser.cpp                    |  5 ++
 6 files changed, 90 insertions(+), 1 deletion(-)

diff --git a/clang/include/clang/Basic/DiagnosticParseKinds.td b/clang/include/clang/Basic/DiagnosticParseKinds.td
index c3753ca2828e25e..02c5b9527f5d5f3 100644
--- a/clang/include/clang/Basic/DiagnosticParseKinds.td
+++ b/clang/include/clang/Basic/DiagnosticParseKinds.td
@@ -1606,6 +1606,9 @@ def err_pragma_invalid_keyword : Error<
 def err_pragma_pipeline_invalid_keyword : Error<
     "invalid argument; expected 'disable'">;
 
+// API notes.
+def err_type_unparsed : Error<"unparsed tokens following type">;
+
 // Pragma unroll support.
 def warn_pragma_unroll_cuda_value_in_parens : Warning<
   "argument to '#pragma unroll' should not be in parentheses in CUDA C/C++">,
diff --git a/clang/include/clang/Lex/Lexer.h b/clang/include/clang/Lex/Lexer.h
index 899e665e7454652..b6ecc7e5ded9e2a 100644
--- a/clang/include/clang/Lex/Lexer.h
+++ b/clang/include/clang/Lex/Lexer.h
@@ -198,11 +198,11 @@ class Lexer : public PreprocessorLexer {
   /// from.  Currently this is only used by _Pragma handling.
   SourceLocation getFileLoc() const { return FileLoc; }
 
-private:
   /// Lex - Return the next token in the file.  If this is the end of file, it
   /// return the tok::eof token.  This implicitly involves the preprocessor.
   bool Lex(Token &Result);
 
+private:
   /// Called when the preprocessor is in 'dependency scanning lexing mode'.
   bool LexDependencyDirectiveToken(Token &Result);
 
diff --git a/clang/include/clang/Parse/Parser.h b/clang/include/clang/Parse/Parser.h
index 465453826c0b982..034a8f90abbfaf7 100644
--- a/clang/include/clang/Parse/Parser.h
+++ b/clang/include/clang/Parse/Parser.h
@@ -3609,6 +3609,18 @@ class Parser : public CodeCompletionHandler {
   ParseConceptDefinition(const ParsedTemplateInfo &TemplateInfo,
                          SourceLocation &DeclEnd);
 
+  /// Parse the given string as a type.
+  ///
+  /// This is a dangerous utility function currently employed only by API notes.
+  /// It is not a general entry-point for safely parsing types from strings.
+  ///
+  /// \param TypeStr The string to be parsed as a type.
+  /// \param Context The name of the context in which this string is being
+  /// parsed, which will be used in diagnostics.
+  /// \param IncludeLoc The location at which this parse was triggered.
+  TypeResult ParseTypeFromString(StringRef TypeStr, StringRef Context,
+                                 SourceLocation IncludeLoc);
+
   //===--------------------------------------------------------------------===//
   // Modules
   DeclGroupPtrTy ParseModuleDecl(Sema::ModuleImportState &ImportState);
diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
index 59806bcbcbb2dbc..10a2414f3f49423 100644
--- a/clang/include/clang/Sema/Sema.h
+++ b/clang/include/clang/Sema/Sema.h
@@ -955,6 +955,10 @@ class Sema final {
     OpaqueParser = P;
   }
 
+  /// Callback to the parser to parse a type expressed as a string.
+  std::function<TypeResult(StringRef, StringRef, SourceLocation)>
+      ParseTypeFromStringCallback;
+
   class DelayedDiagnostics;
 
   class DelayedDiagnosticsState {
diff --git a/clang/lib/Parse/ParseDecl.cpp b/clang/lib/Parse/ParseDecl.cpp
index 8cb5b09fd3b0fa6..421fec3bed58534 100644
--- a/clang/lib/Parse/ParseDecl.cpp
+++ b/clang/lib/Parse/ParseDecl.cpp
@@ -8028,6 +8028,71 @@ bool Parser::TryAltiVecTokenOutOfLine(DeclSpec &DS, SourceLocation Loc,
   return false;
 }
 
+TypeResult Parser::ParseTypeFromString(StringRef TypeStr, StringRef Context,
+                                       SourceLocation IncludeLoc) {
+  // Consume (unexpanded) tokens up to the end-of-directive.
+  SmallVector<Token, 4> Tokens;
+  {
+    // Create a new buffer from which we will parse the type.
+    auto &SourceMgr = PP.getSourceManager();
+    FileID FID = SourceMgr.createFileID(
+        llvm::MemoryBuffer::getMemBufferCopy(TypeStr, Context), SrcMgr::C_User,
+        0, 0, IncludeLoc);
+
+    // Form a new lexer that references the buffer.
+    Lexer L(FID, SourceMgr.getBufferOrFake(FID), PP);
+    L.setParsingPreprocessorDirective(true);
+
+    // Lex the tokens from that buffer.
+    Token Tok;
+    do {
+      L.Lex(Tok);
+      Tokens.push_back(Tok);
+    } while (Tok.isNot(tok::eod));
+  }
+
+  // Replace the "eod" token with an "eof" token identifying the end of
+  // the provided string.
+  Token &EndToken = Tokens.back();
+  EndToken.startToken();
+  EndToken.setKind(tok::eof);
+  EndToken.setLocation(Tok.getLocation());
+  EndToken.setEofData(TypeStr.data());
+
+  // Add the current token back.
+  Tokens.push_back(Tok);
+
+  // Enter the tokens into the token stream.
+  PP.EnterTokenStream(Tokens, /*DisableMacroExpansion=*/false,
+                      /*IsReinject=*/false);
+
+  // Consume the current token so that we'll start parsing the tokens we
+  // added to the stream.
+  ConsumeAnyToken();
+
+  // Enter a new scope.
+  ParseScope LocalScope(this, 0);
+
+  // Parse the type.
+  TypeResult Result = ParseTypeName(nullptr);
+
+  // Check if we parsed the whole thing.
+  if (Result.isUsable() &&
+      (Tok.isNot(tok::eof) || Tok.getEofData() != TypeStr.data())) {
+    Diag(Tok.getLocation(), diag::err_type_unparsed);
+  }
+
+  // There could be leftover tokens (e.g. because of an error).
+  // Skip through until we reach the 'end of directive' token.
+  while (Tok.isNot(tok::eof))
+    ConsumeAnyToken();
+
+  // Consume the end token.
+  if (Tok.is(tok::eof) && Tok.getEofData() == TypeStr.data())
+    ConsumeAnyToken();
+  return Result;
+}
+
 void Parser::DiagnoseBitIntUse(const Token &Tok) {
   // If the token is for _ExtInt, diagnose it as being deprecated. Otherwise,
   // the token is about _BitInt and gets (potentially) diagnosed as use of an
diff --git a/clang/lib/Parse/Parser.cpp b/clang/lib/Parse/Parser.cpp
index 1baeb2aeb021faa..97bcbb605dcbd75 100644
--- a/clang/lib/Parse/Parser.cpp
+++ b/clang/lib/Parse/Parser.cpp
@@ -70,6 +70,11 @@ Parser::Parser(Preprocessor &pp, Sema &actions, bool skipFunctionBodies)
   PP.addCommentHandler(CommentSemaHandler.get());
 
   PP.setCodeCompletionHandler(*this);
+
+  Actions.ParseTypeFromStringCallback =
+      [this](StringRef TypeStr, StringRef Context, SourceLocation IncludeLoc) {
+        return this->ParseTypeFromString(TypeStr, Context, IncludeLoc);
+      };
 }
 
 DiagnosticBuilder Parser::Diag(SourceLocation Loc, unsigned DiagID) {

>From a9f650766153ca18d5eb898a86aa6daa5c7694c2 Mon Sep 17 00:00:00 2001
From: Egor Zhdan <e_zhdan at apple.com>
Date: Tue, 21 Nov 2023 16:42:29 +0000
Subject: [PATCH 3/4] [APINotes] Upstream Sema support for API Notes

---
 clang/include/clang/Sema/Sema.h |  26 +++++
 clang/lib/Sema/SemaDecl.cpp     |  31 ++++++
 clang/lib/Sema/SemaType.cpp     | 181 +++++++++++++++++++-------------
 3 files changed, 166 insertions(+), 72 deletions(-)

diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
index 10a2414f3f49423..694eba872a2782b 100644
--- a/clang/include/clang/Sema/Sema.h
+++ b/clang/include/clang/Sema/Sema.h
@@ -3021,6 +3021,9 @@ class Sema final {
   ParmVarDecl *BuildParmVarDeclForTypedef(DeclContext *DC,
                                           SourceLocation Loc,
                                           QualType T);
+  QualType AdjustParameterTypeForObjCAutoRefCount(QualType T,
+                                                  SourceLocation NameLoc,
+                                                  TypeSourceInfo *TSInfo);
   ParmVarDecl *CheckParameter(DeclContext *DC, SourceLocation StartLoc,
                               SourceLocation NameLoc, IdentifierInfo *Name,
                               QualType T, TypeSourceInfo *TSInfo,
@@ -4806,6 +4809,29 @@ class Sema final {
   /// Valid types should not have multiple attributes with different CCs.
   const AttributedType *getCallingConvAttributedType(QualType T) const;
 
+  /// Check whether a nullability type specifier can be added to the given
+  /// type through some means not written in source (e.g. API notes).
+  ///
+  /// \param Type The type to which the nullability specifier will be
+  /// added. On success, this type will be updated appropriately.
+  ///
+  /// \param Nullability The nullability specifier to add.
+  ///
+  /// \param DiagLoc The location to use for diagnostics.
+  ///
+  /// \param AllowArrayTypes Whether to accept nullability specifiers on an
+  /// array type (e.g., because it will decay to a pointer).
+  ///
+  /// \param OverrideExisting Whether to override an existing, locally-specified
+  /// nullability specifier rather than complaining about the conflict.
+  ///
+  /// \returns true if nullability cannot be applied, false otherwise.
+  bool CheckImplicitNullabilityTypeSpecifier(QualType &Type,
+                                             NullabilityKind Nullability,
+                                             SourceLocation DiagLoc,
+                                             bool AllowArrayTypes,
+                                             bool OverrideExisting);
+
   /// Process the attributes before creating an attributed statement. Returns
   /// the semantic attributes that have been processed.
   void ProcessStmtAttributes(Stmt *Stmt, const ParsedAttributes &InAttrs,
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 4e1857b931cc868..def6cf2f6d24baa 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -15139,6 +15139,37 @@ void Sema::DiagnoseSizeOfParametersAndReturnValue(
   }
 }
 
+QualType Sema::AdjustParameterTypeForObjCAutoRefCount(QualType T,
+                                                      SourceLocation NameLoc,
+                                                      TypeSourceInfo *TSInfo) {
+  // In ARC, infer a lifetime qualifier for appropriate parameter types.
+  if (getLangOpts().ObjCAutoRefCount &&
+      T.getObjCLifetime() == Qualifiers::OCL_None && T->isObjCLifetimeType()) {
+
+    Qualifiers::ObjCLifetime Lifetime;
+
+    // Special cases for arrays:
+    //   - if it's const, use __unsafe_unretained
+    //   - otherwise, it's an error
+    if (T->isArrayType()) {
+      if (!T.isConstQualified()) {
+        if (DelayedDiagnostics.shouldDelayDiagnostics())
+          DelayedDiagnostics.add(sema::DelayedDiagnostic::makeForbiddenType(
+              NameLoc, diag::err_arc_array_param_no_ownership, T, false));
+        else
+          Diag(NameLoc, diag::err_arc_array_param_no_ownership)
+              << TSInfo->getTypeLoc().getSourceRange();
+      }
+      Lifetime = Qualifiers::OCL_ExplicitNone;
+    } else {
+      Lifetime = T->getObjCARCImplicitLifetime();
+    }
+    T = Context.getLifetimeQualifiedType(T, Lifetime);
+  }
+
+  return T;
+}
+
 ParmVarDecl *Sema::CheckParameter(DeclContext *DC, SourceLocation StartLoc,
                                   SourceLocation NameLoc, IdentifierInfo *Name,
                                   QualType T, TypeSourceInfo *TSInfo,
diff --git a/clang/lib/Sema/SemaType.cpp b/clang/lib/Sema/SemaType.cpp
index 560feafa1857cb3..1533eeb5099e087 100644
--- a/clang/lib/Sema/SemaType.cpp
+++ b/clang/lib/Sema/SemaType.cpp
@@ -7519,6 +7519,26 @@ static bool HandleWebAssemblyFuncrefAttr(TypeProcessingState &State,
   return false;
 }
 
+/// Rebuild an attributed type without the nullability attribute on it.
+static QualType rebuildAttributedTypeWithoutNullability(ASTContext &Ctx,
+                                                        QualType Type) {
+  auto Attributed = dyn_cast<AttributedType>(Type.getTypePtr());
+  if (!Attributed)
+    return Type;
+
+  // Skip the nullability attribute; we're done.
+  if (Attributed->getImmediateNullability()) {
+    return Attributed->getModifiedType();
+  }
+
+  // Build the modified type.
+  auto Modified = rebuildAttributedTypeWithoutNullability(
+      Ctx, Attributed->getModifiedType());
+  assert(Modified.getTypePtr() != Attributed->getModifiedType().getTypePtr());
+  return Ctx.getAttributedType(Attributed->getAttrKind(), Modified,
+                               Attributed->getEquivalentType());
+}
+
 /// Map a nullability attribute kind to a nullability kind.
 static NullabilityKind mapNullabilityAttrKind(ParsedAttr::Kind kind) {
   switch (kind) {
@@ -7539,74 +7559,65 @@ static NullabilityKind mapNullabilityAttrKind(ParsedAttr::Kind kind) {
   }
 }
 
-/// Applies a nullability type specifier to the given type, if possible.
-///
-/// \param state The type processing state.
-///
-/// \param type The type to which the nullability specifier will be
-/// added. On success, this type will be updated appropriately.
-///
-/// \param attr The attribute as written on the type.
-///
-/// \param allowOnArrayType Whether to accept nullability specifiers on an
-/// array type (e.g., because it will decay to a pointer).
-///
-/// \returns true if a problem has been diagnosed, false on success.
-static bool checkNullabilityTypeSpecifier(TypeProcessingState &state,
-                                          QualType &type,
-                                          ParsedAttr &attr,
-                                          bool allowOnArrayType) {
-  Sema &S = state.getSema();
-
-  NullabilityKind nullability = mapNullabilityAttrKind(attr.getKind());
-  SourceLocation nullabilityLoc = attr.getLoc();
-  bool isContextSensitive = attr.isContextSensitiveKeywordAttribute();
-
-  recordNullabilitySeen(S, nullabilityLoc);
+static bool CheckNullabilityTypeSpecifier(
+    Sema &S, TypeProcessingState *State, ParsedAttr *PAttr, QualType &QT,
+    NullabilityKind Nullability, SourceLocation NullabilityLoc,
+    bool IsContextSensitive, bool AllowOnArrayType, bool OverrideExisting) {
+  bool Implicit = (State == nullptr);
+  if (!Implicit)
+    recordNullabilitySeen(S, NullabilityLoc);
 
   // Check for existing nullability attributes on the type.
-  QualType desugared = type;
-  while (auto attributed = dyn_cast<AttributedType>(desugared.getTypePtr())) {
+  QualType Desugared = QT;
+  while (auto Attributed = dyn_cast<AttributedType>(Desugared.getTypePtr())) {
     // Check whether there is already a null
-    if (auto existingNullability = attributed->getImmediateNullability()) {
+    if (auto ExistingNullability = Attributed->getImmediateNullability()) {
       // Duplicated nullability.
-      if (nullability == *existingNullability) {
-        S.Diag(nullabilityLoc, diag::warn_nullability_duplicate)
-          << DiagNullabilityKind(nullability, isContextSensitive)
-          << FixItHint::CreateRemoval(nullabilityLoc);
+      if (Nullability == *ExistingNullability) {
+        if (Implicit)
+          break;
+
+        S.Diag(NullabilityLoc, diag::warn_nullability_duplicate)
+            << DiagNullabilityKind(Nullability, IsContextSensitive)
+            << FixItHint::CreateRemoval(NullabilityLoc);
 
         break;
       }
 
-      // Conflicting nullability.
-      S.Diag(nullabilityLoc, diag::err_nullability_conflicting)
-        << DiagNullabilityKind(nullability, isContextSensitive)
-        << DiagNullabilityKind(*existingNullability, false);
-      return true;
+      if (!OverrideExisting) {
+        // Conflicting nullability.
+        S.Diag(NullabilityLoc, diag::err_nullability_conflicting)
+            << DiagNullabilityKind(Nullability, IsContextSensitive)
+            << DiagNullabilityKind(*ExistingNullability, false);
+        return true;
+      }
+
+      // Rebuild the attributed type, dropping the existing nullability.
+      QT = rebuildAttributedTypeWithoutNullability(S.Context, QT);
     }
 
-    desugared = attributed->getModifiedType();
+    Desugared = Attributed->getModifiedType();
   }
 
   // If there is already a different nullability specifier, complain.
   // This (unlike the code above) looks through typedefs that might
   // have nullability specifiers on them, which means we cannot
   // provide a useful Fix-It.
-  if (auto existingNullability = desugared->getNullability()) {
-    if (nullability != *existingNullability) {
-      S.Diag(nullabilityLoc, diag::err_nullability_conflicting)
-        << DiagNullabilityKind(nullability, isContextSensitive)
-        << DiagNullabilityKind(*existingNullability, false);
+  if (auto ExistingNullability = Desugared->getNullability()) {
+    if (Nullability != *ExistingNullability && !Implicit) {
+      S.Diag(NullabilityLoc, diag::err_nullability_conflicting)
+          << DiagNullabilityKind(Nullability, IsContextSensitive)
+          << DiagNullabilityKind(*ExistingNullability, false);
 
       // Try to find the typedef with the existing nullability specifier.
-      if (auto typedefType = desugared->getAs<TypedefType>()) {
-        TypedefNameDecl *typedefDecl = typedefType->getDecl();
+      if (auto TT = Desugared->getAs<TypedefType>()) {
+        TypedefNameDecl *typedefDecl = TT->getDecl();
         QualType underlyingType = typedefDecl->getUnderlyingType();
-        if (auto typedefNullability
-              = AttributedType::stripOuterNullability(underlyingType)) {
-          if (*typedefNullability == *existingNullability) {
+        if (auto typedefNullability =
+                AttributedType::stripOuterNullability(underlyingType)) {
+          if (*typedefNullability == *ExistingNullability) {
             S.Diag(typedefDecl->getLocation(), diag::note_nullability_here)
-              << DiagNullabilityKind(*existingNullability, false);
+                << DiagNullabilityKind(*ExistingNullability, false);
           }
         }
       }
@@ -7616,44 +7627,73 @@ static bool checkNullabilityTypeSpecifier(TypeProcessingState &state,
   }
 
   // If this definitely isn't a pointer type, reject the specifier.
-  if (!desugared->canHaveNullability() &&
-      !(allowOnArrayType && desugared->isArrayType())) {
-    S.Diag(nullabilityLoc, diag::err_nullability_nonpointer)
-      << DiagNullabilityKind(nullability, isContextSensitive) << type;
+  if (!Desugared->canHaveNullability() &&
+      !(AllowOnArrayType && Desugared->isArrayType())) {
+    if (!Implicit)
+      S.Diag(NullabilityLoc, diag::err_nullability_nonpointer)
+          << DiagNullabilityKind(Nullability, IsContextSensitive) << QT;
+
     return true;
   }
 
   // For the context-sensitive keywords/Objective-C property
   // attributes, require that the type be a single-level pointer.
-  if (isContextSensitive) {
+  if (IsContextSensitive) {
     // Make sure that the pointee isn't itself a pointer type.
     const Type *pointeeType = nullptr;
-    if (desugared->isArrayType())
-      pointeeType = desugared->getArrayElementTypeNoTypeQual();
-    else if (desugared->isAnyPointerType())
-      pointeeType = desugared->getPointeeType().getTypePtr();
+    if (Desugared->isArrayType())
+      pointeeType = Desugared->getArrayElementTypeNoTypeQual();
+    else if (Desugared->isAnyPointerType())
+      pointeeType = Desugared->getPointeeType().getTypePtr();
 
     if (pointeeType && (pointeeType->isAnyPointerType() ||
                         pointeeType->isObjCObjectPointerType() ||
                         pointeeType->isMemberPointerType())) {
-      S.Diag(nullabilityLoc, diag::err_nullability_cs_multilevel)
-        << DiagNullabilityKind(nullability, true)
-        << type;
-      S.Diag(nullabilityLoc, diag::note_nullability_type_specifier)
-        << DiagNullabilityKind(nullability, false)
-        << type
-        << FixItHint::CreateReplacement(nullabilityLoc,
-                                        getNullabilitySpelling(nullability));
+      S.Diag(NullabilityLoc, diag::err_nullability_cs_multilevel)
+          << DiagNullabilityKind(Nullability, true) << QT;
+      S.Diag(NullabilityLoc, diag::note_nullability_type_specifier)
+          << DiagNullabilityKind(Nullability, false) << QT
+          << FixItHint::CreateReplacement(NullabilityLoc,
+                                          getNullabilitySpelling(Nullability));
       return true;
     }
   }
 
   // Form the attributed type.
-  type = state.getAttributedType(
-      createNullabilityAttr(S.Context, attr, nullability), type, type);
+  if (State) {
+    assert(PAttr);
+    Attr *A = createNullabilityAttr(S.Context, *PAttr, Nullability);
+    QT = State->getAttributedType(A, QT, QT);
+  } else {
+    attr::Kind attrKind = AttributedType::getNullabilityAttrKind(Nullability);
+    QT = S.Context.getAttributedType(attrKind, QT, QT);
+  }
   return false;
 }
 
+static bool CheckNullabilityTypeSpecifier(TypeProcessingState &State,
+                                          QualType &Type, ParsedAttr &Attr,
+                                          bool AllowOnArrayType) {
+  NullabilityKind Nullability = mapNullabilityAttrKind(Attr.getKind());
+  SourceLocation NullabilityLoc = Attr.getLoc();
+  bool IsContextSensitive = Attr.isContextSensitiveKeywordAttribute();
+
+  return CheckNullabilityTypeSpecifier(State.getSema(), &State, &Attr, Type,
+                                       Nullability, NullabilityLoc,
+                                       IsContextSensitive, AllowOnArrayType,
+                                       /*overrideExisting*/ false);
+}
+
+bool Sema::CheckImplicitNullabilityTypeSpecifier(QualType &Type,
+                                                 NullabilityKind Nullability,
+                                                 SourceLocation DiagLoc,
+                                                 bool AllowArrayTypes,
+                                                 bool OverrideExisting) {
+  return CheckNullabilityTypeSpecifier(
+      *this, nullptr, nullptr, Type, Nullability, DiagLoc,
+      /*isContextSensitive*/ false, AllowArrayTypes, OverrideExisting);
+}
+
 /// Check the application of the Objective-C '__kindof' qualifier to
 /// the given type.
 static bool checkObjCKindOfType(TypeProcessingState &state, QualType &type,
@@ -8858,11 +8898,8 @@ static void processTypeAttrs(TypeProcessingState &state, QualType &type,
         bool allowOnArrayType =
             state.getDeclarator().isPrototypeContext() &&
             !hasOuterPointerLikeChunk(state.getDeclarator(), endIndex);
-        if (checkNullabilityTypeSpecifier(
-              state,
-              type,
-              attr,
-              allowOnArrayType)) {
+        if (CheckNullabilityTypeSpecifier(state, type, attr,
+                                          allowOnArrayType)) {
           attr.setInvalid();
         }
 

>From b9c67f1c14d038a3942a6de854c58f83a1427d71 Mon Sep 17 00:00:00 2001
From: Egor Zhdan <e_zhdan at apple.com>
Date: Tue, 21 Nov 2023 16:57:26 +0000
Subject: [PATCH 4/4] [APINotes] Upstream Sema logic to apply API Notes to
 decls

---
 .../clang/Basic/DiagnosticSemaKinds.td        |    7 +
 clang/include/clang/Sema/Sema.h               |    6 +
 clang/lib/Sema/CMakeLists.txt                 |    1 +
 clang/lib/Sema/SemaAPINotes.cpp               | 1014 +++++++++++++++++
 clang/lib/Sema/SemaDecl.cpp                   |    4 +
 clang/lib/Sema/SemaDeclAttr.cpp               |    3 +
 clang/lib/Sema/SemaDeclCXX.cpp                |    6 +-
 clang/lib/Sema/SemaDeclObjC.cpp               |    4 +
 clang/lib/Sema/SemaObjCProperty.cpp           |    5 +
 clang/lib/Sema/SemaTemplate.cpp               |    7 +
 10 files changed, 1056 insertions(+), 1 deletion(-)
 create mode 100644 clang/lib/Sema/SemaAPINotes.cpp

diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index 990692c06d7d3a8..f09f2899754690d 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -10667,6 +10667,13 @@ def warn_imp_cast_drops_unaligned : Warning<
 
 } // end of sema category
 
+let CategoryName = "API Notes Issue" in {
+
+def err_incompatible_replacement_type : Error<
+  "API notes replacement type %0 has a different size from original type %1">;
+
+} // end of API Notes category
+
 let CategoryName = "OpenMP Issue" in {
 // OpenMP support.
 def err_omp_expected_var_arg : Error<
diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
index 694eba872a2782b..0b300df3ef5b666 100644
--- a/clang/include/clang/Sema/Sema.h
+++ b/clang/include/clang/Sema/Sema.h
@@ -4749,6 +4749,12 @@ class Sema final {
   bool checkCommonAttributeFeatures(const Stmt *S, const ParsedAttr &A,
                                     bool SkipArgCountCheck = false);
 
+  /// Map any API notes provided for this declaration to attributes on the
+  /// declaration.
+  ///
+  /// Triggered by declaration-attribute processing.
+  void ProcessAPINotes(Decl *D);
+
   /// Determine if type T is a valid subject for a nonnull and similar
   /// attributes. By default, we look through references (the behavior used by
   /// nonnull), but if the second parameter is true, then we treat a reference
diff --git a/clang/lib/Sema/CMakeLists.txt b/clang/lib/Sema/CMakeLists.txt
index 1856a88e9a3271a..4f72bce98fbbec3 100644
--- a/clang/lib/Sema/CMakeLists.txt
+++ b/clang/lib/Sema/CMakeLists.txt
@@ -27,6 +27,7 @@ add_clang_library(clangSema
   Sema.cpp
   SemaAccess.cpp
   SemaAttr.cpp
+  SemaAPINotes.cpp
   SemaAvailability.cpp
   SemaCXXScopeSpec.cpp
   SemaCast.cpp
diff --git a/clang/lib/Sema/SemaAPINotes.cpp b/clang/lib/Sema/SemaAPINotes.cpp
new file mode 100644
index 000000000000000..4f2ac1acfc01a9d
--- /dev/null
+++ b/clang/lib/Sema/SemaAPINotes.cpp
@@ -0,0 +1,1014 @@
+//===--- SemaAPINotes.cpp - API Notes Handling ----------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+//  This file implements the mapping from API notes to declaration attributes.
+//
+//===----------------------------------------------------------------------===//
+
+#include "clang/APINotes/APINotesReader.h"
+#include "clang/AST/Decl.h"
+#include "clang/AST/DeclObjC.h"
+#include "clang/Basic/SourceLocation.h"
+#include "clang/Lex/Lexer.h"
+#include "clang/Sema/SemaInternal.h"
+
+using namespace clang;
+
+namespace {
+enum IsActive_t : bool { IsNotActive, IsActive };
+enum IsReplacement_t : bool { IsNotReplacement, IsReplacement };
+
+struct VersionedInfoMetadata {
+  /// An empty version refers to unversioned metadata.
+  VersionTuple Version;
+  unsigned IsActive : 1;
+  unsigned IsReplacement : 1;
+
+  VersionedInfoMetadata(VersionTuple Version, IsActive_t Active,
+                        IsReplacement_t Replacement)
+      : Version(Version), IsActive(Active == IsActive_t::IsActive),
+        IsReplacement(Replacement == IsReplacement_t::IsReplacement) {}
+};
+} // end anonymous namespace
+
+/// Determine whether this is a multi-level pointer type.
+static bool isMultiLevelPointerType(QualType Type) {
+  QualType Pointee = Type->getPointeeType();
+  if (Pointee.isNull())
+    return false;
+
+  return Pointee->isAnyPointerType() || Pointee->isObjCObjectPointerType() ||
+         Pointee->isMemberPointerType();
+}
+
+/// Apply nullability to the given declaration.
+static void applyNullability(Sema &S, Decl *D, NullabilityKind Nullability,
+                             VersionedInfoMetadata Metadata) {
+  if (!Metadata.IsActive)
+    return;
+
+  QualType Type;
+
+  // Nullability for a function/method appertains to the retain type.
+  if (auto Function = dyn_cast<FunctionDecl>(D))
+    Type = Function->getReturnType();
+  else if (auto Method = dyn_cast<ObjCMethodDecl>(D))
+    Type = Method->getReturnType();
+  else if (auto Value = dyn_cast<ValueDecl>(D))
+    Type = Value->getType();
+  else if (auto Property = dyn_cast<ObjCPropertyDecl>(D))
+    Type = Property->getType();
+  else
+    return;
+
+  // Check the nullability specifier on this type.
+  QualType OrigType = Type;
+  S.CheckImplicitNullabilityTypeSpecifier(Type, Nullability, D->getLocation(),
+                                          isa<ParmVarDecl>(D),
+                                          /*overrideExisting=*/true);
+  if (Type.getTypePtr() == OrigType.getTypePtr())
+    return;
+
+  if (auto Function = dyn_cast<FunctionDecl>(D)) {
+    const FunctionType *FnType = Function->getType()->castAs<FunctionType>();
+    if (const FunctionProtoType *Proto = dyn_cast<FunctionProtoType>(FnType))
+      Function->setType(S.Context.getFunctionType(Type, Proto->getParamTypes(),
+                                                  Proto->getExtProtoInfo()));
+    else
+      Function->setType(
+          S.Context.getFunctionNoProtoType(Type, FnType->getExtInfo()));
+  } else if (auto Method = dyn_cast<ObjCMethodDecl>(D)) {
+    Method->setReturnType(Type);
+
+    // Make it a context-sensitive keyword if we can.
+    if (!isMultiLevelPointerType(Type))
+      Method->setObjCDeclQualifier(Decl::ObjCDeclQualifier(
+          Method->getObjCDeclQualifier() | Decl::OBJC_TQ_CSNullability));
+
+  } else if (auto Value = dyn_cast<ValueDecl>(D)) {
+    Value->setType(Type);
+
+    // Make it a context-sensitive keyword if we can.
+    if (auto Parm = dyn_cast<ParmVarDecl>(D)) {
+      if (Parm->isObjCMethodParameter() && !isMultiLevelPointerType(Type))
+        Parm->setObjCDeclQualifier(Decl::ObjCDeclQualifier(
+            Parm->getObjCDeclQualifier() | Decl::OBJC_TQ_CSNullability));
+    }
+  } else if (auto Property = dyn_cast<ObjCPropertyDecl>(D)) {
+    Property->setType(Type, Property->getTypeSourceInfo());
+
+    // Make it a property attribute if we can.
+    if (!isMultiLevelPointerType(Type))
+      Property->setPropertyAttributes(
+          ObjCPropertyAttribute::kind_null_resettable);
+
+  } else
+    llvm_unreachable("cannot handle nullability here");
+}
+
+/// Copy a string into ASTContext-allocated memory.
+static StringRef CopyString(ASTContext &Ctx, StringRef String) {
+  void *mem = Ctx.Allocate(String.size(), alignof(char));
+  memcpy(mem, String.data(), String.size());
+  return StringRef(static_cast<char *>(mem), String.size());
+}
+
+static AttributeCommonInfo getDummyAttrInfo() {
+  return AttributeCommonInfo(SourceRange(),
+                             AttributeCommonInfo::UnknownAttribute,
+                             {AttributeCommonInfo::AS_GNU,
+                              /*Spelling*/ 0, /*IsAlignas*/ false,
+                              /*IsRegularKeywordAttribute*/ false});
+}
+
+namespace {
+template <typename A> struct AttrKindFor {};
+
+#define ATTR(X)                                                                \
+  template <> struct AttrKindFor<X##Attr> {                                    \
+    static const attr::Kind value = attr::X;                                   \
+  };
+#include "clang/Basic/AttrList.inc"
+
+/// Handle an attribute introduced by API notes.
+///
+/// \param ShouldAddAttribute Whether we should add a new attribute
+/// (otherwise, we might remove an existing attribute).
+/// \param CreateAttr Create the new attribute to be added.
+template <typename A>
+void handleAPINotedAttribute(
+    Sema &S, Decl *D, bool ShouldAddAttribute, VersionedInfoMetadata Metadata,
+    llvm::function_ref<A *()> CreateAttr,
+    llvm::function_ref<Decl::attr_iterator(const Decl *)> GetExistingAttr) {
+  if (Metadata.IsActive) {
+    auto Existing = GetExistingAttr(D);
+    if (Existing != D->attr_end()) {
+      // Remove the existing attribute, and treat it as a superseded
+      // non-versioned attribute.
+      auto *Versioned = SwiftVersionedAttr::CreateImplicit(
+          S.Context, Metadata.Version, *Existing, /*IsReplacedByActive*/ true);
+
+      D->getAttrs().erase(Existing);
+      D->addAttr(Versioned);
+    }
+
+    // If we're supposed to add a new attribute, do so.
+    if (ShouldAddAttribute) {
+      if (auto Attr = CreateAttr())
+        D->addAttr(Attr);
+    }
+
+  } else {
+    if (ShouldAddAttribute) {
+      if (auto Attr = CreateAttr()) {
+        auto *Versioned = SwiftVersionedAttr::CreateImplicit(
+            S.Context, Metadata.Version, Attr,
+            /*IsReplacedByActive*/ Metadata.IsReplacement);
+        D->addAttr(Versioned);
+      }
+    } else {
+      // FIXME: This isn't preserving enough information for things like
+      // availability, where we're trying to remove a /specific/ kind of
+      // attribute.
+      auto *Versioned = SwiftVersionedRemovalAttr::CreateImplicit(
+          S.Context, Metadata.Version, AttrKindFor<A>::value,
+          /*IsReplacedByActive*/ Metadata.IsReplacement);
+      D->addAttr(Versioned);
+    }
+  }
+}
+
+template <typename A>
+void handleAPINotedAttribute(Sema &S, Decl *D, bool ShouldAddAttribute,
+                             VersionedInfoMetadata Metadata,
+                             llvm::function_ref<A *()> CreateAttr) {
+  handleAPINotedAttribute<A>(
+      S, D, ShouldAddAttribute, Metadata, CreateAttr, [](const Decl *D) {
+        return llvm::find_if(D->attrs(),
+                             [](const Attr *Next) { return isa<A>(Next); });
+      });
+}
+} // namespace
+
+template <typename A = CFReturnsRetainedAttr>
+static void handleAPINotedRetainCountAttribute(Sema &S, Decl *D,
+                                               bool ShouldAddAttribute,
+                                               VersionedInfoMetadata Metadata) {
+  // The template argument has a default to make the "removal" case more
+  // concise; it doesn't matter /which/ attribute is being removed.
+  handleAPINotedAttribute<A>(
+      S, D, ShouldAddAttribute, Metadata,
+      [&] { return new (S.Context) A(S.Context, getDummyAttrInfo()); },
+      [](const Decl *D) -> Decl::attr_iterator {
+        return llvm::find_if(D->attrs(), [](const Attr *Next) -> bool {
+          return isa<CFReturnsRetainedAttr>(Next) ||
+                 isa<CFReturnsNotRetainedAttr>(Next) ||
+                 isa<NSReturnsRetainedAttr>(Next) ||
+                 isa<NSReturnsNotRetainedAttr>(Next) ||
+                 isa<CFAuditedTransferAttr>(Next);
+        });
+      });
+}
+
+static void handleAPINotedRetainCountConvention(
+    Sema &S, Decl *D, VersionedInfoMetadata Metadata,
+    std::optional<api_notes::RetainCountConventionKind> Convention) {
+  if (!Convention)
+    return;
+  switch (*Convention) {
+  case api_notes::RetainCountConventionKind::None:
+    if (isa<FunctionDecl>(D)) {
+      handleAPINotedRetainCountAttribute<CFUnknownTransferAttr>(
+          S, D, /*shouldAddAttribute*/ true, Metadata);
+    } else {
+      handleAPINotedRetainCountAttribute(S, D, /*shouldAddAttribute*/ false,
+                                         Metadata);
+    }
+    break;
+  case api_notes::RetainCountConventionKind::CFReturnsRetained:
+    handleAPINotedRetainCountAttribute<CFReturnsRetainedAttr>(
+        S, D, /*shouldAddAttribute*/ true, Metadata);
+    break;
+  case api_notes::RetainCountConventionKind::CFReturnsNotRetained:
+    handleAPINotedRetainCountAttribute<CFReturnsNotRetainedAttr>(
+        S, D, /*shouldAddAttribute*/ true, Metadata);
+    break;
+  case api_notes::RetainCountConventionKind::NSReturnsRetained:
+    handleAPINotedRetainCountAttribute<NSReturnsRetainedAttr>(
+        S, D, /*shouldAddAttribute*/ true, Metadata);
+    break;
+  case api_notes::RetainCountConventionKind::NSReturnsNotRetained:
+    handleAPINotedRetainCountAttribute<NSReturnsNotRetainedAttr>(
+        S, D, /*shouldAddAttribute*/ true, Metadata);
+    break;
+  }
+}
+
+static void ProcessAPINotes(Sema &S, Decl *D,
+                            const api_notes::CommonEntityInfo &Info,
+                            VersionedInfoMetadata Metadata) {
+  // Availability
+  if (Info.Unavailable) {
+    handleAPINotedAttribute<UnavailableAttr>(S, D, true, Metadata, [&] {
+      return new (S.Context)
+          UnavailableAttr(S.Context, getDummyAttrInfo(),
+                          CopyString(S.Context, Info.UnavailableMsg));
+    });
+  }
+
+  if (Info.UnavailableInSwift) {
+    handleAPINotedAttribute<AvailabilityAttr>(
+        S, D, true, Metadata,
+        [&] {
+          return new (S.Context) AvailabilityAttr(
+              S.Context, getDummyAttrInfo(), &S.Context.Idents.get("swift"),
+              VersionTuple(), VersionTuple(), VersionTuple(),
+              /*Unavailable=*/true, CopyString(S.Context, Info.UnavailableMsg),
+              /*Strict=*/false,
+              /*Replacement=*/StringRef(),
+              /*Priority=*/Sema::AP_Explicit);
+        },
+        [](const Decl *D) {
+          return llvm::find_if(D->attrs(), [](const Attr *next) -> bool {
+            auto *AA = dyn_cast<AvailabilityAttr>(next);
+            if (!AA)
+              return false;
+            const IdentifierInfo *platform = AA->getPlatform();
+            if (!platform)
+              return false;
+            return platform->isStr("swift");
+          });
+        });
+  }
+
+  // swift_private
+  if (auto SwiftPrivate = Info.isSwiftPrivate()) {
+    handleAPINotedAttribute<SwiftPrivateAttr>(
+        S, D, *SwiftPrivate, Metadata, [&] {
+          return new (S.Context)
+              SwiftPrivateAttr(S.Context, getDummyAttrInfo());
+        });
+  }
+
+  // swift_name
+  if (!Info.SwiftName.empty()) {
+    handleAPINotedAttribute<SwiftNameAttr>(
+        S, D, true, Metadata, [&]() -> SwiftNameAttr * {
+          AttributeFactory AF{};
+          AttributePool AP{AF};
+          auto &C = S.getASTContext();
+          ParsedAttr *SNA =
+              AP.create(&C.Idents.get("swift_name"), SourceRange(), nullptr,
+                        SourceLocation(), nullptr, nullptr, nullptr,
+                        ParsedAttr::Form::GNU());
+
+          if (!S.DiagnoseSwiftName(D, Info.SwiftName, D->getLocation(), *SNA,
+                                   /*IsAsync=*/false))
+            return nullptr;
+
+          return new (S.Context)
+              SwiftNameAttr(S.Context, getDummyAttrInfo(),
+                            CopyString(S.Context, Info.SwiftName));
+        });
+  }
+}
+
+static void ProcessAPINotes(Sema &S, Decl *D,
+                            const api_notes::CommonTypeInfo &Info,
+                            VersionedInfoMetadata Metadata) {
+  // swift_bridge
+  if (auto SwiftBridge = Info.getSwiftBridge()) {
+    handleAPINotedAttribute<SwiftBridgeAttr>(
+        S, D, !SwiftBridge->empty(), Metadata, [&] {
+          return new (S.Context)
+              SwiftBridgeAttr(S.Context, getDummyAttrInfo(),
+                              CopyString(S.Context, *SwiftBridge));
+        });
+  }
+
+  // ns_error_domain
+  if (auto NSErrorDomain = Info.getNSErrorDomain()) {
+    handleAPINotedAttribute<NSErrorDomainAttr>(
+        S, D, !NSErrorDomain->empty(), Metadata, [&] {
+          return new (S.Context)
+              NSErrorDomainAttr(S.Context, getDummyAttrInfo(),
+                                &S.Context.Idents.get(*NSErrorDomain));
+        });
+  }
+
+  ProcessAPINotes(S, D, static_cast<const api_notes::CommonEntityInfo &>(Info),
+                  Metadata);
+}
+
+/// Check that the replacement type provided by API notes is reasonable.
+///
+/// This is a very weak form of ABI check.
+static bool checkAPINotesReplacementType(Sema &S, SourceLocation Loc,
+                                         QualType OrigType,
+                                         QualType ReplacementType) {
+  if (S.Context.getTypeSize(OrigType) !=
+      S.Context.getTypeSize(ReplacementType)) {
+    S.Diag(Loc, diag::err_incompatible_replacement_type)
+        << ReplacementType << OrigType;
+    return true;
+  }
+
+  return false;
+}
+
+/// Process API notes for a variable or property.
+static void ProcessAPINotes(Sema &S, Decl *D,
+                            const api_notes::VariableInfo &Info,
+                            VersionedInfoMetadata Metadata) {
+  // Type override.
+  if (Metadata.IsActive && !Info.getType().empty() &&
+      S.ParseTypeFromStringCallback) {
+    auto ParsedType = S.ParseTypeFromStringCallback(
+        Info.getType(), "<API Notes>", D->getLocation());
+    if (ParsedType.isUsable()) {
+      QualType Type = Sema::GetTypeFromParser(ParsedType.get());
+      auto TypeInfo =
+          S.Context.getTrivialTypeSourceInfo(Type, D->getLocation());
+
+      if (auto Var = dyn_cast<VarDecl>(D)) {
+        // Make adjustments to parameter types.
+        if (isa<ParmVarDecl>(Var)) {
+          Type = S.AdjustParameterTypeForObjCAutoRefCount(
+              Type, D->getLocation(), TypeInfo);
+          Type = S.Context.getAdjustedParameterType(Type);
+        }
+
+        if (!checkAPINotesReplacementType(S, Var->getLocation(), Var->getType(),
+                                          Type)) {
+          Var->setType(Type);
+          Var->setTypeSourceInfo(TypeInfo);
+        }
+      } else if (auto Property = dyn_cast<ObjCPropertyDecl>(D)) {
+        if (!checkAPINotesReplacementType(S, Property->getLocation(),
+                                          Property->getType(), Type))
+          Property->setType(Type, TypeInfo);
+
+      } else
+        llvm_unreachable("API notes allowed a type on an unknown declaration");
+    }
+  }
+
+  // Nullability.
+  if (auto Nullability = Info.getNullability())
+    applyNullability(S, D, *Nullability, Metadata);
+
+  // Handle common entity information.
+  ProcessAPINotes(S, D, static_cast<const api_notes::CommonEntityInfo &>(Info),
+                  Metadata);
+}
+
+/// Process API notes for a parameter.
+static void ProcessAPINotes(Sema &S, ParmVarDecl *D,
+                            const api_notes::ParamInfo &Info,
+                            VersionedInfoMetadata Metadata) {
+  // noescape
+  if (auto NoEscape = Info.isNoEscape())
+    handleAPINotedAttribute<NoEscapeAttr>(S, D, *NoEscape, Metadata, [&] {
+      return new (S.Context) NoEscapeAttr(S.Context, getDummyAttrInfo());
+    });
+
+  // Retain count convention
+  handleAPINotedRetainCountConvention(S, D, Metadata,
+                                      Info.getRetainCountConvention());
+
+  // Handle common entity information.
+  ProcessAPINotes(S, D, static_cast<const api_notes::VariableInfo &>(Info),
+                  Metadata);
+}
+
+/// Process API notes for a global variable.
+static void ProcessAPINotes(Sema &S, VarDecl *D,
+                            const api_notes::GlobalVariableInfo &Info,
+                            VersionedInfoMetadata metadata) {
+  // Handle common entity information.
+  ProcessAPINotes(S, D, static_cast<const api_notes::VariableInfo &>(Info),
+                  metadata);
+}
+
+/// Process API notes for an Objective-C property.
+static void ProcessAPINotes(Sema &S, ObjCPropertyDecl *D,
+                            const api_notes::ObjCPropertyInfo &Info,
+                            VersionedInfoMetadata Metadata) {
+  // Handle common entity information.
+  ProcessAPINotes(S, D, static_cast<const api_notes::VariableInfo &>(Info),
+                  Metadata);
+
+  if (auto AsAccessors = Info.getSwiftImportAsAccessors()) {
+    handleAPINotedAttribute<SwiftImportPropertyAsAccessorsAttr>(
+        S, D, *AsAccessors, Metadata, [&] {
+          return new (S.Context)
+              SwiftImportPropertyAsAccessorsAttr(S.Context, getDummyAttrInfo());
+        });
+  }
+}
+
+namespace {
+typedef llvm::PointerUnion<FunctionDecl *, ObjCMethodDecl *> FunctionOrMethod;
+}
+
+/// Process API notes for a function or method.
+static void ProcessAPINotes(Sema &S, FunctionOrMethod AnyFunc,
+                            const api_notes::FunctionInfo &Info,
+                            VersionedInfoMetadata Metadata) {
+  // Find the declaration itself.
+  FunctionDecl *FD = AnyFunc.dyn_cast<FunctionDecl *>();
+  Decl *D = FD;
+  ObjCMethodDecl *MD = 0;
+  if (!D) {
+    MD = AnyFunc.get<ObjCMethodDecl *>();
+    D = MD;
+  }
+
+  // Nullability of return type.
+  if (Info.NullabilityAudited)
+    applyNullability(S, D, Info.getReturnTypeInfo(), Metadata);
+
+  // Parameters.
+  unsigned NumParams;
+  if (FD)
+    NumParams = FD->getNumParams();
+  else
+    NumParams = MD->param_size();
+
+  bool AnyTypeChanged = false;
+  for (unsigned I = 0; I != NumParams; ++I) {
+    ParmVarDecl *Param;
+    if (FD)
+      Param = FD->getParamDecl(I);
+    else
+      Param = MD->param_begin()[I];
+
+    QualType ParamTypeBefore = Param->getType();
+
+    if (I < Info.Params.size())
+      ProcessAPINotes(S, Param, Info.Params[I], Metadata);
+
+    // Nullability.
+    if (Info.NullabilityAudited)
+      applyNullability(S, Param, Info.getParamTypeInfo(I), Metadata);
+
+    if (ParamTypeBefore.getAsOpaquePtr() != Param->getType().getAsOpaquePtr())
+      AnyTypeChanged = true;
+  }
+
+  // Result type override.
+  QualType OverriddenResultType;
+  if (Metadata.IsActive && !Info.ResultType.empty() &&
+      S.ParseTypeFromStringCallback) {
+    auto ParsedType = S.ParseTypeFromStringCallback(
+        Info.ResultType, "<API Notes>", D->getLocation());
+    if (ParsedType.isUsable()) {
+      QualType ResultType = Sema::GetTypeFromParser(ParsedType.get());
+
+      if (MD) {
+        if (!checkAPINotesReplacementType(S, D->getLocation(),
+                                          MD->getReturnType(), ResultType)) {
+          auto ResultTypeInfo =
+              S.Context.getTrivialTypeSourceInfo(ResultType, D->getLocation());
+          MD->setReturnType(ResultType);
+          MD->setReturnTypeSourceInfo(ResultTypeInfo);
+        }
+      } else if (!checkAPINotesReplacementType(
+                     S, FD->getLocation(), FD->getReturnType(), ResultType)) {
+        OverriddenResultType = ResultType;
+        AnyTypeChanged = true;
+      }
+    }
+  }
+
+  // If the result type or any of the parameter types changed for a function
+  // declaration, we have to rebuild the type.
+  if (FD && AnyTypeChanged) {
+    if (const auto *fnProtoType = FD->getType()->getAs<FunctionProtoType>()) {
+      if (OverriddenResultType.isNull())
+        OverriddenResultType = fnProtoType->getReturnType();
+
+      SmallVector<QualType, 4> ParamTypes;
+      for (auto Param : FD->parameters())
+        ParamTypes.push_back(Param->getType());
+
+      FD->setType(S.Context.getFunctionType(OverriddenResultType, ParamTypes,
+                                            fnProtoType->getExtProtoInfo()));
+    } else if (!OverriddenResultType.isNull()) {
+      const auto *FnNoProtoType = FD->getType()->castAs<FunctionNoProtoType>();
+      FD->setType(S.Context.getFunctionNoProtoType(
+          OverriddenResultType, FnNoProtoType->getExtInfo()));
+    }
+  }
+
+  // Retain count convention
+  handleAPINotedRetainCountConvention(S, D, Metadata,
+                                      Info.getRetainCountConvention());
+
+  // Handle common entity information.
+  ProcessAPINotes(S, D, static_cast<const api_notes::CommonEntityInfo &>(Info),
+                  Metadata);
+}
+
+/// Process API notes for a global function.
+static void ProcessAPINotes(Sema &S, FunctionDecl *D,
+                            const api_notes::GlobalFunctionInfo &Info,
+                            VersionedInfoMetadata Metadata) {
+  // Handle common function information.
+  ProcessAPINotes(S, FunctionOrMethod(D),
+                  static_cast<const api_notes::FunctionInfo &>(Info), Metadata);
+}
+
+/// Process API notes for an enumerator.
+static void ProcessAPINotes(Sema &S, EnumConstantDecl *D,
+                            const api_notes::EnumConstantInfo &Info,
+                            VersionedInfoMetadata Metadata) {
+  // Handle common information.
+  ProcessAPINotes(S, D, static_cast<const api_notes::CommonEntityInfo &>(Info),
+                  Metadata);
+}
+
+/// Process API notes for an Objective-C method.
+static void ProcessAPINotes(Sema &S, ObjCMethodDecl *D,
+                            const api_notes::ObjCMethodInfo &Info,
+                            VersionedInfoMetadata Metadata) {
+  // Designated initializers.
+  if (Info.DesignatedInit) {
+    handleAPINotedAttribute<ObjCDesignatedInitializerAttr>(
+        S, D, true, Metadata, [&] {
+          if (ObjCInterfaceDecl *IFace = D->getClassInterface())
+            IFace->setHasDesignatedInitializers();
+
+          return new (S.Context)
+              ObjCDesignatedInitializerAttr(S.Context, getDummyAttrInfo());
+        });
+  }
+
+  // Handle common function information.
+  ProcessAPINotes(S, FunctionOrMethod(D),
+                  static_cast<const api_notes::FunctionInfo &>(Info), Metadata);
+}
+
+/// Process API notes for a tag.
+static void ProcessAPINotes(Sema &S, TagDecl *D, const api_notes::TagInfo &Info,
+                            VersionedInfoMetadata Metadata) {
+  if (auto ImportAs = Info.SwiftImportAs) {
+    auto attr = SwiftAttrAttr::Create(S.Context, "import_" + ImportAs.value());
+    D->addAttr(attr);
+  }
+  if (auto RetainOp = Info.SwiftRetainOp) {
+    auto attr = SwiftAttrAttr::Create(S.Context, "retain:" + RetainOp.value());
+    D->addAttr(attr);
+  }
+  if (auto ReleaseOp = Info.SwiftReleaseOp) {
+    auto attr =
+        SwiftAttrAttr::Create(S.Context, "release:" + ReleaseOp.value());
+    D->addAttr(attr);
+  }
+
+  if (auto Extensibility = Info.EnumExtensibility) {
+    using api_notes::EnumExtensibilityKind;
+    bool ShouldAddAttribute = (*Extensibility != EnumExtensibilityKind::None);
+    handleAPINotedAttribute<EnumExtensibilityAttr>(
+        S, D, ShouldAddAttribute, Metadata, [&] {
+          EnumExtensibilityAttr::Kind kind;
+          switch (*Extensibility) {
+          case EnumExtensibilityKind::None:
+            llvm_unreachable("remove only");
+          case EnumExtensibilityKind::Open:
+            kind = EnumExtensibilityAttr::Open;
+            break;
+          case EnumExtensibilityKind::Closed:
+            kind = EnumExtensibilityAttr::Closed;
+            break;
+          }
+          return new (S.Context)
+              EnumExtensibilityAttr(S.Context, getDummyAttrInfo(), kind);
+        });
+  }
+
+  if (auto FlagEnum = Info.isFlagEnum()) {
+    handleAPINotedAttribute<FlagEnumAttr>(S, D, *FlagEnum, Metadata, [&] {
+      return new (S.Context) FlagEnumAttr(S.Context, getDummyAttrInfo());
+    });
+  }
+
+  // Handle common type information.
+  ProcessAPINotes(S, D, static_cast<const api_notes::CommonTypeInfo &>(Info),
+                  Metadata);
+}
+
+/// Process API notes for a typedef.
+static void ProcessAPINotes(Sema &S, TypedefNameDecl *D,
+                            const api_notes::TypedefInfo &Info,
+                            VersionedInfoMetadata Metadata) {
+  // swift_wrapper
+  using SwiftWrapperKind = api_notes::SwiftNewTypeKind;
+
+  if (auto SwiftWrapper = Info.SwiftWrapper) {
+    handleAPINotedAttribute<SwiftNewTypeAttr>(
+        S, D, *SwiftWrapper != SwiftWrapperKind::None, Metadata, [&] {
+          SwiftNewTypeAttr::NewtypeKind Kind;
+          switch (*SwiftWrapper) {
+          case SwiftWrapperKind::None:
+            llvm_unreachable("Shouldn't build an attribute");
+
+          case SwiftWrapperKind::Struct:
+            Kind = SwiftNewTypeAttr::NK_Struct;
+            break;
+
+          case SwiftWrapperKind::Enum:
+            Kind = SwiftNewTypeAttr::NK_Enum;
+            break;
+          }
+          AttributeCommonInfo SyntaxInfo{
+              SourceRange(),
+              AttributeCommonInfo::AT_SwiftNewType,
+              {AttributeCommonInfo::AS_GNU, SwiftNewTypeAttr::GNU_swift_wrapper,
+               /*IsAlignas*/ false, /*IsRegularKeywordAttribute*/ false}};
+          return new (S.Context) SwiftNewTypeAttr(S.Context, SyntaxInfo, Kind);
+        });
+  }
+
+  // Handle common type information.
+  ProcessAPINotes(S, D, static_cast<const api_notes::CommonTypeInfo &>(Info),
+                  Metadata);
+}
+
+/// Process API notes for an Objective-C class or protocol.
+static void ProcessAPINotes(Sema &S, ObjCContainerDecl *D,
+                            const api_notes::ObjCContextInfo &Info,
+                            VersionedInfoMetadata Metadata) {
+  // Handle common type information.
+  ProcessAPINotes(S, D, static_cast<const api_notes::CommonTypeInfo &>(Info),
+                  Metadata);
+}
+
+/// Process API notes for an Objective-C class.
+static void ProcessAPINotes(Sema &S, ObjCInterfaceDecl *D,
+                            const api_notes::ObjCContextInfo &Info,
+                            VersionedInfoMetadata Metadata) {
+  if (auto AsNonGeneric = Info.getSwiftImportAsNonGeneric()) {
+    handleAPINotedAttribute<SwiftImportAsNonGenericAttr>(
+        S, D, *AsNonGeneric, Metadata, [&] {
+          return new (S.Context)
+              SwiftImportAsNonGenericAttr(S.Context, getDummyAttrInfo());
+        });
+  }
+
+  if (auto ObjcMembers = Info.getSwiftObjCMembers()) {
+    handleAPINotedAttribute<SwiftObjCMembersAttr>(
+        S, D, *ObjcMembers, Metadata, [&] {
+          return new (S.Context)
+              SwiftObjCMembersAttr(S.Context, getDummyAttrInfo());
+        });
+  }
+
+  // Handle information common to Objective-C classes and protocols.
+  ProcessAPINotes(S, static_cast<clang::ObjCContainerDecl *>(D), Info,
+                  Metadata);
+}
+
+/// If we're applying API notes with an active, non-default version, and the
+/// versioned API notes have a SwiftName but the declaration normally wouldn't
+/// have one, add a removal attribute to make it clear that the new SwiftName
+/// attribute only applies to the active version of \p D, not to all versions.
+///
+/// This must be run \em before processing API notes for \p D, because otherwise
+/// any existing SwiftName attribute will have been packaged up in a
+/// SwiftVersionedAttr.
+template <typename SpecificInfo>
+static void maybeAttachUnversionedSwiftName(
+    Sema &S, Decl *D,
+    const api_notes::APINotesReader::VersionedInfo<SpecificInfo> Info) {
+  if (D->hasAttr<SwiftNameAttr>())
+    return;
+  if (!Info.getSelected())
+    return;
+
+  // Is the active slice versioned, and does it set a Swift name?
+  VersionTuple SelectedVersion;
+  SpecificInfo SelectedInfoSlice;
+  std::tie(SelectedVersion, SelectedInfoSlice) = Info[*Info.getSelected()];
+  if (SelectedVersion.empty())
+    return;
+  if (SelectedInfoSlice.SwiftName.empty())
+    return;
+
+  // Does the unversioned slice /not/ set a Swift name?
+  for (const auto &VersionAndInfoSlice : Info) {
+    if (!VersionAndInfoSlice.first.empty())
+      continue;
+    if (!VersionAndInfoSlice.second.SwiftName.empty())
+      return;
+  }
+
+  // Then explicitly call that out with a removal attribute.
+  VersionedInfoMetadata DummyFutureMetadata(SelectedVersion, IsNotActive,
+                                            IsReplacement);
+  handleAPINotedAttribute<SwiftNameAttr>(
+      S, D, /*add*/ false, DummyFutureMetadata, []() -> SwiftNameAttr * {
+        llvm_unreachable("should not try to add an attribute here");
+      });
+}
+
+/// Processes all versions of versioned API notes.
+///
+/// Just dispatches to the various ProcessAPINotes functions in this file.
+template <typename SpecificDecl, typename SpecificInfo>
+static void ProcessVersionedAPINotes(
+    Sema &S, SpecificDecl *D,
+    const api_notes::APINotesReader::VersionedInfo<SpecificInfo> Info) {
+
+  maybeAttachUnversionedSwiftName(S, D, Info);
+
+  unsigned Selected = Info.getSelected().value_or(Info.size());
+
+  VersionTuple Version;
+  SpecificInfo InfoSlice;
+  for (unsigned i = 0, e = Info.size(); i != e; ++i) {
+    std::tie(Version, InfoSlice) = Info[i];
+    auto Active = (i == Selected) ? IsActive : IsNotActive;
+    auto Replacement = IsNotReplacement;
+    if (Active == IsNotActive && Version.empty()) {
+      Replacement = IsReplacement;
+      Version = Info[Selected].first;
+    }
+    ProcessAPINotes(S, D, InfoSlice,
+                    VersionedInfoMetadata(Version, Active, Replacement));
+  }
+}
+
+/// Process API notes that are associated with this declaration, mapping them
+/// to attributes as appropriate.
+void Sema::ProcessAPINotes(Decl *D) {
+  if (!D)
+    return;
+
+  // Globals.
+  if (D->getDeclContext()->isFileContext() ||
+      D->getDeclContext()->isNamespace() ||
+      D->getDeclContext()->isExternCContext() ||
+      D->getDeclContext()->isExternCXXContext()) {
+    std::optional<api_notes::Context> APINotesContext;
+    if (auto NamespaceContext = dyn_cast<NamespaceDecl>(D->getDeclContext())) {
+      for (auto Reader :
+           APINotes.findAPINotes(NamespaceContext->getLocation())) {
+        // Retrieve the context ID for the parent namespace of the decl.
+        std::stack<NamespaceDecl *> NamespaceStack;
+        {
+          for (auto CurrentNamespace = NamespaceContext; CurrentNamespace;
+               CurrentNamespace =
+                   dyn_cast<NamespaceDecl>(CurrentNamespace->getParent())) {
+            if (!CurrentNamespace->isInlineNamespace())
+              NamespaceStack.push(CurrentNamespace);
+          }
+        }
+        std::optional<api_notes::ContextID> NamespaceID;
+        while (!NamespaceStack.empty()) {
+          auto CurrentNamespace = NamespaceStack.top();
+          NamespaceStack.pop();
+          NamespaceID = Reader->lookupNamespaceID(CurrentNamespace->getName(),
+                                                  NamespaceID);
+          if (!NamespaceID)
+            break;
+        }
+        if (NamespaceID)
+          APINotesContext = api_notes::Context(
+              *NamespaceID, api_notes::ContextKind::Namespace);
+      }
+    }
+
+    // Global variables.
+    if (auto VD = dyn_cast<VarDecl>(D)) {
+      for (auto Reader : APINotes.findAPINotes(D->getLocation())) {
+        auto Info =
+            Reader->lookupGlobalVariable(VD->getName(), APINotesContext);
+        ProcessVersionedAPINotes(*this, VD, Info);
+      }
+
+      return;
+    }
+
+    // Global functions.
+    if (auto FD = dyn_cast<FunctionDecl>(D)) {
+      if (FD->getDeclName().isIdentifier()) {
+        for (auto Reader : APINotes.findAPINotes(D->getLocation())) {
+          auto Info =
+              Reader->lookupGlobalFunction(FD->getName(), APINotesContext);
+          ProcessVersionedAPINotes(*this, FD, Info);
+        }
+      }
+
+      return;
+    }
+
+    // Objective-C classes.
+    if (auto Class = dyn_cast<ObjCInterfaceDecl>(D)) {
+      for (auto Reader : APINotes.findAPINotes(D->getLocation())) {
+        auto Info = Reader->lookupObjCClassInfo(Class->getName());
+        ProcessVersionedAPINotes(*this, Class, Info);
+      }
+
+      return;
+    }
+
+    // Objective-C protocols.
+    if (auto Protocol = dyn_cast<ObjCProtocolDecl>(D)) {
+      for (auto Reader : APINotes.findAPINotes(D->getLocation())) {
+        auto Info = Reader->lookupObjCProtocolInfo(Protocol->getName());
+        ProcessVersionedAPINotes(*this, Protocol, Info);
+      }
+
+      return;
+    }
+
+    // Tags
+    if (auto Tag = dyn_cast<TagDecl>(D)) {
+      std::string LookupName = Tag->getName().str();
+
+      // Use the source location to discern if this Tag is an OPTIONS macro.
+      // For now we would like to limit this trick of looking up the APINote tag
+      // using the EnumDecl's QualType in the case where the enum is anonymous.
+      // This is only being used to support APINotes lookup for C++
+      // NS/CF_OPTIONS when C++-Interop is enabled.
+      std::string MacroName =
+          LookupName.empty() && Tag->getOuterLocStart().isMacroID()
+              ? clang::Lexer::getImmediateMacroName(
+                    Tag->getOuterLocStart(),
+                    Tag->getASTContext().getSourceManager(), LangOpts)
+                    .str()
+              : "";
+
+      if (LookupName.empty() && isa<clang::EnumDecl>(Tag) &&
+          (MacroName == "CF_OPTIONS" || MacroName == "NS_OPTIONS" ||
+           MacroName == "OBJC_OPTIONS" || MacroName == "SWIFT_OPTIONS")) {
+
+        clang::QualType T = llvm::cast<clang::EnumDecl>(Tag)->getIntegerType();
+        LookupName = clang::QualType::getAsString(
+            T.split(), getASTContext().getPrintingPolicy());
+      }
+
+      for (auto Reader : APINotes.findAPINotes(D->getLocation())) {
+        auto Info = Reader->lookupTag(LookupName, APINotesContext);
+        ProcessVersionedAPINotes(*this, Tag, Info);
+      }
+
+      return;
+    }
+
+    // Typedefs
+    if (auto Typedef = dyn_cast<TypedefNameDecl>(D)) {
+      for (auto Reader : APINotes.findAPINotes(D->getLocation())) {
+        auto Info = Reader->lookupTypedef(Typedef->getName(), APINotesContext);
+        ProcessVersionedAPINotes(*this, Typedef, Info);
+      }
+
+      return;
+    }
+  }
+
+  // Enumerators.
+  if (D->getDeclContext()->getRedeclContext()->isFileContext() ||
+      D->getDeclContext()->getRedeclContext()->isExternCContext()) {
+    if (auto EnumConstant = dyn_cast<EnumConstantDecl>(D)) {
+      for (auto Reader : APINotes.findAPINotes(D->getLocation())) {
+        auto Info = Reader->lookupEnumConstant(EnumConstant->getName());
+        ProcessVersionedAPINotes(*this, EnumConstant, Info);
+      }
+
+      return;
+    }
+  }
+
+  if (auto ObjCContainer = dyn_cast<ObjCContainerDecl>(D->getDeclContext())) {
+    // Location function that looks up an Objective-C context.
+    auto GetContext = [&](api_notes::APINotesReader *Reader)
+        -> std::optional<api_notes::ContextID> {
+      if (auto Protocol = dyn_cast<ObjCProtocolDecl>(ObjCContainer)) {
+        if (auto Found = Reader->lookupObjCProtocolID(Protocol->getName()))
+          return *Found;
+
+        return std::nullopt;
+      }
+
+      if (auto Impl = dyn_cast<ObjCCategoryImplDecl>(ObjCContainer)) {
+        if (auto Cat = Impl->getCategoryDecl())
+          ObjCContainer = Cat;
+        else
+          return std::nullopt;
+      }
+
+      if (auto Category = dyn_cast<ObjCCategoryDecl>(ObjCContainer)) {
+        if (Category->getClassInterface())
+          ObjCContainer = Category->getClassInterface();
+        else
+          return std::nullopt;
+      }
+
+      if (auto Impl = dyn_cast<ObjCImplDecl>(ObjCContainer)) {
+        if (Impl->getClassInterface())
+          ObjCContainer = Impl->getClassInterface();
+        else
+          return std::nullopt;
+      }
+
+      if (auto Class = dyn_cast<ObjCInterfaceDecl>(ObjCContainer)) {
+        if (auto Found = Reader->lookupObjCClassID(Class->getName()))
+          return *Found;
+
+        return std::nullopt;
+      }
+
+      return std::nullopt;
+    };
+
+    // Objective-C methods.
+    if (auto Method = dyn_cast<ObjCMethodDecl>(D)) {
+      for (auto Reader : APINotes.findAPINotes(D->getLocation())) {
+        if (auto Context = GetContext(Reader)) {
+          // Map the selector.
+          Selector Sel = Method->getSelector();
+          SmallVector<StringRef, 2> SelPieces;
+          if (Sel.isUnarySelector())
+            SelPieces.push_back(Sel.getNameForSlot(0));
+          else {
+            for (unsigned i = 0, n = Sel.getNumArgs(); i != n; ++i)
+              SelPieces.push_back(Sel.getNameForSlot(i));
+          }
+
+          api_notes::ObjCSelectorRef SelectorRef;
+          SelectorRef.NumArgs = Sel.getNumArgs();
+          SelectorRef.Identifiers = SelPieces;
+
+          auto Info = Reader->lookupObjCMethod(*Context, SelectorRef,
+                                               Method->isInstanceMethod());
+          ProcessVersionedAPINotes(*this, Method, Info);
+        }
+      }
+    }
+
+    // Objective-C properties.
+    if (auto Property = dyn_cast<ObjCPropertyDecl>(D)) {
+      for (auto Reader : APINotes.findAPINotes(D->getLocation())) {
+        if (auto Context = GetContext(Reader)) {
+          bool isInstanceProperty =
+              (Property->getPropertyAttributesAsWritten() &
+               ObjCPropertyAttribute::kind_class) == 0;
+          auto Info = Reader->lookupObjCProperty(*Context, Property->getName(),
+                                                 isInstanceProperty);
+          ProcessVersionedAPINotes(*this, Property, Info);
+        }
+      }
+
+      return;
+    }
+
+    return;
+  }
+}
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index def6cf2f6d24baa..302950879e457a8 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -16300,6 +16300,7 @@ void Sema::ActOnFinishDelayedAttribute(Scope *S, Decl *D,
   if (TemplateDecl *TD = dyn_cast<TemplateDecl>(D))
     D = TD->getTemplatedDecl();
   ProcessDeclAttributeList(S, D, Attrs);
+  ProcessAPINotes(D);
 
   if (CXXMethodDecl *Method = dyn_cast_or_null<CXXMethodDecl>(D))
     if (Method->isStatic())
@@ -19519,6 +19520,7 @@ void Sema::ActOnFields(Scope *S, SourceLocation RecLoc, Decl *EnclosingDecl,
       CDecl->setIvarRBraceLoc(RBrac);
     }
   }
+  ProcessAPINotes(Record);
 
   // Check the "counted_by" attribute to ensure that the count field exists in
   // the struct. Make sure we're performing this check on the outer-most
@@ -19847,6 +19849,7 @@ Decl *Sema::ActOnEnumConstant(Scope *S, Decl *theEnumDecl, Decl *lastEnumConst,
   // Process attributes.
   ProcessDeclAttributeList(S, New, Attrs);
   AddPragmaAttributes(S, New);
+  ProcessAPINotes(New);
 
   // Register this decl in the current scope stack.
   New->setAccess(TheEnumDecl->getAccess());
@@ -20045,6 +20048,7 @@ void Sema::ActOnEnumBody(SourceLocation EnumLoc, SourceRange BraceRange,
   QualType EnumType = Context.getTypeDeclType(Enum);
 
   ProcessDeclAttributeList(S, Enum, Attrs);
+  ProcessAPINotes(Enum);
 
   if (Enum->isDependentType()) {
     for (unsigned i = 0, e = Elements.size(); i != e; ++i) {
diff --git a/clang/lib/Sema/SemaDeclAttr.cpp b/clang/lib/Sema/SemaDeclAttr.cpp
index 8552b28e51acd97..f245b1466de8dd0 100644
--- a/clang/lib/Sema/SemaDeclAttr.cpp
+++ b/clang/lib/Sema/SemaDeclAttr.cpp
@@ -9948,6 +9948,9 @@ void Sema::ProcessDeclAttributes(Scope *S, Decl *D, const Declarator &PD) {
 
   // Apply additional attributes specified by '#pragma clang attribute'.
   AddPragmaAttributes(S, D);
+
+  // Look for API notes that map to attributes.
+  ProcessAPINotes(D);
 }
 
 /// Is the given declaration allowed to use a forbidden type?
diff --git a/clang/lib/Sema/SemaDeclCXX.cpp b/clang/lib/Sema/SemaDeclCXX.cpp
index 3688192e6cbe5c5..476f19ef338f68b 100644
--- a/clang/lib/Sema/SemaDeclCXX.cpp
+++ b/clang/lib/Sema/SemaDeclCXX.cpp
@@ -11700,6 +11700,7 @@ Decl *Sema::ActOnStartNamespaceDef(Scope *NamespcScope,
 
   ProcessDeclAttributeList(DeclRegionScope, Namespc, AttrList);
   AddPragmaAttributes(DeclRegionScope, Namespc);
+  ProcessAPINotes(Namespc);
 
   // FIXME: Should we be merging attributes?
   if (const VisibilityAttr *Attr = Namespc->getAttr<VisibilityAttr>())
@@ -12219,8 +12220,10 @@ Decl *Sema::ActOnUsingDirective(Scope *S, SourceLocation UsingLoc,
     Diag(IdentLoc, diag::err_expected_namespace_name) << SS.getRange();
   }
 
-  if (UDir)
+  if (UDir) {
     ProcessDeclAttributeList(S, UDir, AttrList);
+    ProcessAPINotes(UDir);
+  }
 
   return UDir;
 }
@@ -13512,6 +13515,7 @@ Decl *Sema::ActOnAliasDeclaration(Scope *S, AccessSpecifier AS,
 
   ProcessDeclAttributeList(S, NewTD, AttrList);
   AddPragmaAttributes(S, NewTD);
+  ProcessAPINotes(NewTD);
 
   CheckTypedefForVariablyModifiedType(S, NewTD);
   Invalid |= NewTD->isInvalidDecl();
diff --git a/clang/lib/Sema/SemaDeclObjC.cpp b/clang/lib/Sema/SemaDeclObjC.cpp
index cdfa6ad3f281a43..526f3a8db30e212 100644
--- a/clang/lib/Sema/SemaDeclObjC.cpp
+++ b/clang/lib/Sema/SemaDeclObjC.cpp
@@ -1072,6 +1072,7 @@ ObjCInterfaceDecl *Sema::ActOnStartClassInterface(
 
   ProcessDeclAttributeList(TUScope, IDecl, AttrList);
   AddPragmaAttributes(TUScope, IDecl);
+  ProcessAPINotes(IDecl);
 
   // Merge attributes from previous declarations.
   if (PrevIDecl)
@@ -1273,6 +1274,7 @@ ObjCProtocolDecl *Sema::ActOnStartProtocolInterface(
 
   ProcessDeclAttributeList(TUScope, PDecl, AttrList);
   AddPragmaAttributes(TUScope, PDecl);
+  ProcessAPINotes(PDecl);
 
   // Merge attributes from previous declarations.
   if (PrevDecl)
@@ -4807,6 +4809,7 @@ Decl *Sema::ActOnMethodDeclaration(
     // Apply the attributes to the parameter.
     ProcessDeclAttributeList(TUScope, Param, ArgInfo[i].ArgAttrs);
     AddPragmaAttributes(TUScope, Param);
+    ProcessAPINotes(Param);
 
     if (Param->hasAttr<BlocksAttr>()) {
       Diag(Param->getLocation(), diag::err_block_on_nonlocal);
@@ -4837,6 +4840,7 @@ Decl *Sema::ActOnMethodDeclaration(
 
   ProcessDeclAttributeList(TUScope, ObjCMethod, AttrList);
   AddPragmaAttributes(TUScope, ObjCMethod);
+  ProcessAPINotes(ObjCMethod);
 
   // Add the method now.
   const ObjCMethodDecl *PrevMethod = nullptr;
diff --git a/clang/lib/Sema/SemaObjCProperty.cpp b/clang/lib/Sema/SemaObjCProperty.cpp
index 22540af1cda8c6d..09b6a9cdfbd5763 100644
--- a/clang/lib/Sema/SemaObjCProperty.cpp
+++ b/clang/lib/Sema/SemaObjCProperty.cpp
@@ -2509,6 +2509,8 @@ void Sema::ProcessPropertyDecl(ObjCPropertyDecl *property) {
       GetterMethod->addAttr(SectionAttr::CreateImplicit(
           Context, SA->getName(), Loc, SectionAttr::GNU_section));
 
+    ProcessAPINotes(GetterMethod);
+
     if (getLangOpts().ObjCAutoRefCount)
       CheckARCMethodDecl(GetterMethod);
   } else
@@ -2578,6 +2580,9 @@ void Sema::ProcessPropertyDecl(ObjCPropertyDecl *property) {
       if (const SectionAttr *SA = property->getAttr<SectionAttr>())
         SetterMethod->addAttr(SectionAttr::CreateImplicit(
             Context, SA->getName(), Loc, SectionAttr::GNU_section));
+
+      ProcessAPINotes(SetterMethod);
+
       // It's possible for the user to have set a very odd custom
       // setter selector that causes it to have a method family.
       if (getLangOpts().ObjCAutoRefCount)
diff --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp
index c188dd34014a4b3..737b12ac73b6994 100644
--- a/clang/lib/Sema/SemaTemplate.cpp
+++ b/clang/lib/Sema/SemaTemplate.cpp
@@ -2145,6 +2145,7 @@ DeclResult Sema::CheckClassTemplate(
     NewClass->startDefinition();
 
   ProcessDeclAttributeList(S, NewClass, Attr);
+  ProcessAPINotes(NewClass);
 
   if (PrevClassTemplate)
     mergeDeclAttributes(NewClass, PrevClassTemplate->getTemplatedDecl());
@@ -8930,6 +8931,7 @@ DeclResult Sema::ActOnClassTemplateSpecialization(
   }
 
   ProcessDeclAttributeList(S, Specialization, Attr);
+  ProcessAPINotes(Specialization);
 
   // Add alignment attributes if necessary; these attributes are checked when
   // the ASTContext lays out the structure.
@@ -10165,6 +10167,7 @@ DeclResult Sema::ActOnExplicitInstantiation(
 
   bool PreviouslyDLLExported = Specialization->hasAttr<DLLExportAttr>();
   ProcessDeclAttributeList(S, Specialization, Attr);
+  ProcessAPINotes(Specialization);
 
   // Add the explicit instantiation into its lexical context. However,
   // since explicit instantiations are never found by name lookup, we
@@ -10575,6 +10578,9 @@ DeclResult Sema::ActOnExplicitInstantiation(Scope *S,
       Prev->setTemplateSpecializationKind(TSK, D.getIdentifierLoc());
       // Merge attributes.
       ProcessDeclAttributeList(S, Prev, D.getDeclSpec().getAttributes());
+      if (PrevTemplate)
+        ProcessAPINotes(Prev);
+
       if (TSK == TSK_ExplicitInstantiationDefinition)
         InstantiateVariableDefinition(D.getIdentifierLoc(), Prev);
     }
@@ -10750,6 +10756,7 @@ DeclResult Sema::ActOnExplicitInstantiation(Scope *S,
   }
 
   ProcessDeclAttributeList(S, Specialization, D.getDeclSpec().getAttributes());
+  ProcessAPINotes(Specialization);
 
   // In MSVC mode, dllimported explicit instantiation definitions are treated as
   // instantiation declarations.



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