[5.9][Macros] Generalize conformance macros as extension macros

include/swift/AST/Attr.h

@@ -2368,36 +2368,45 @@ class ObjCImplementationAttr final : public DeclAttribute {
 /// which declares one of the roles that a given macro can inhabit.
 class MacroRoleAttr final
     : public DeclAttribute,
-      private llvm::TrailingObjects<MacroRoleAttr, MacroIntroducedDeclName> {
+      private llvm::TrailingObjects<MacroRoleAttr, MacroIntroducedDeclName,
+                                    TypeExpr *> {
   friend TrailingObjects;
 
   MacroSyntax syntax;
   MacroRole role;
   unsigned numNames;
+  unsigned numConformances;
   SourceLoc lParenLoc, rParenLoc;
 
   MacroRoleAttr(SourceLoc atLoc, SourceRange range, MacroSyntax syntax,
                 SourceLoc lParenLoc, MacroRole role,
                 ArrayRef<MacroIntroducedDeclName> names,
+                ArrayRef<TypeExpr *> conformances,
                 SourceLoc rParenLoc, bool implicit);
 
 public:
   static MacroRoleAttr *create(ASTContext &ctx, SourceLoc atLoc,
                                SourceRange range, MacroSyntax syntax,
                                SourceLoc lParenLoc, MacroRole role,
                                ArrayRef<MacroIntroducedDeclName> names,
+                               ArrayRef<TypeExpr *> conformances,
                                SourceLoc rParenLoc, bool implicit);
 
   size_t numTrailingObjects(OverloadToken<MacroIntroducedDeclName>) const {
     return numNames;
   }
 
+  size_t numTrailingObjects(OverloadToken<TypeExpr *>) const {
+    return numConformances;
+  }
+
   SourceLoc getLParenLoc() const { return lParenLoc; }
   SourceLoc getRParenLoc() const { return rParenLoc; }
 
   MacroSyntax getMacroSyntax() const { return syntax; }
   MacroRole getMacroRole() const { return role; }
   ArrayRef<MacroIntroducedDeclName> getNames() const;
+  ArrayRef<TypeExpr *> getConformances() const;
   bool hasNameKind(MacroIntroducedDeclNameKind kind) const;
 
   static bool classof(const DeclAttribute *DA) {

include/swift/AST/DiagnosticsSema.def

@@ -7148,6 +7148,9 @@ ERROR(global_arbitrary_name,none,
       "'%0' macros are not allowed to introduce arbitrary names "
       "at global scope",
       (StringRef))
+ERROR(local_extension_macro,none,
+      "local type cannot have attached extension macro",
+      ())
 
 ERROR(macro_resolve_circular_reference, none,
       "circular reference resolving %select{freestanding|attached}0 macro %1",

include/swift/AST/MacroDeclaration.h

@@ -58,6 +58,9 @@ enum class MacroRole: uint32_t {
   /// A freestanding macro that expands to expressions, statements and
   /// declarations in a code block.
   CodeItem = 0x80,
+  /// An attached macro that adds extensions to the declaration the
+  /// macro is attached to.
+  Extension = 0x100,
 
   // NOTE: When adding a new macro role, also add it to `getAllMacroRoles`.
 };

include/swift/AST/PrintOptions.h

@@ -582,6 +582,11 @@ struct PrintOptions {
   /// If false, we print them as ordinary associated types.
   bool PrintPrimaryAssociatedTypes = true;
 
+  /// Whether or not to print \c @attached(extension) attributes on
+  /// macro declarations. This is used for feature suppression in
+  /// Swift interface printing.
+  bool PrintExtensionMacroAttributes = true;
+
   /// If this is not \c nullptr then function bodies (including accessors
   /// and constructors) will be printed by this function.
   std::function<void(const ValueDecl *, ASTPrinter &)> FunctionBody;

include/swift/AST/TypeCheckRequests.h

@@ -4054,6 +4054,28 @@ class ExpandConformanceMacros
   void noteCycleStep(DiagnosticEngine &diags) const;
 };
 
+/// Expand all extension macros attached to the given declaration.
+///
+/// Produces the set of macro expansion buffer IDs.
+class ExpandExtensionMacros
+    : public SimpleRequest<ExpandExtensionMacros,
+                           ArrayRef<unsigned>(NominalTypeDecl *),
+                           RequestFlags::Cached> {
+public:
+  using SimpleRequest::SimpleRequest;
+
+private:
+  friend SimpleRequest;
+
+  ArrayRef<unsigned> evaluate(Evaluator &evaluator,
+                              NominalTypeDecl *nominal) const;
+
+public:
+  bool isCached() const { return true; }
+  void diagnoseCycle(DiagnosticEngine &diags) const;
+  void noteCycleStep(DiagnosticEngine &diags) const;
+};
+
 /// Expand all member attribute macros attached to the given
 /// declaration.
 ///

include/swift/AST/TypeCheckerTypeIDZone.def

@@ -460,6 +460,9 @@ SWIFT_REQUEST(TypeChecker, ExpandAccessorMacros,
 SWIFT_REQUEST(TypeChecker, ExpandConformanceMacros,
               ArrayRef<unsigned>(NominalTypeDecl *),
               Cached, NoLocationInfo)
+SWIFT_REQUEST(TypeChecker, ExpandExtensionMacros,
+              ArrayRef<unsigned>(NominalTypeDecl *),
+              Cached, NoLocationInfo)
 SWIFT_REQUEST(TypeChecker, ExpandSynthesizedMemberMacroRequest,
               ArrayRef<unsigned>(Decl *),
               Cached, NoLocationInfo)

include/swift/Basic/Features.def

@@ -121,6 +121,9 @@ EXPERIMENTAL_FEATURE(CodeItemMacros, true)
 EXPERIMENTAL_FEATURE(TupleConformances, false)
 EXPERIMENTAL_FEATURE(InitAccessors, false)
 
+EXPERIMENTAL_FEATURE(ExtensionMacros, false)
+SUPPRESSIBLE_LANGUAGE_FEATURE(ExtensionMacroAttr, 0, "@attached(extension)", true)
+
 // FIXME: MoveOnlyClasses is not intended to be in production,
 // but our tests currently rely on it, and we want to run those
 // tests in non-asserts builds too.

include/swift/Basic/SourceManager.h

@@ -53,6 +53,9 @@ class GeneratedSourceInfo {
     /// The expansion of an attached conformance macro.
     ConformanceMacroExpansion,
 
+    /// The expansion of an attached extension macro.
+    ExtensionMacroExpansion,
+
     /// A new function body that is replacing an existing function body.
     ReplacedFunctionBody,
 

include/swift/Demangling/DemangleNodes.def

@@ -93,6 +93,7 @@ NODE(DifferentiableFunctionType)
 NODE(ExistentialMetatype)
 CONTEXT_NODE(ExplicitClosure)
 CONTEXT_NODE(Extension)
+NODE(ExtensionAttachedMacroExpansion)
 NODE(FieldOffset)
 NODE(FreestandingMacroExpansion)
 NODE(FullTypeMetadata)

lib/AST/ASTMangler.cpp

@@ -3914,7 +3914,8 @@ void ASTMangler::appendMacroExpansionContext(
   case GeneratedSourceInfo::MemberAttributeMacroExpansion:
   case GeneratedSourceInfo::MemberMacroExpansion:
   case GeneratedSourceInfo::PeerMacroExpansion:
-  case GeneratedSourceInfo::ConformanceMacroExpansion: {
+  case GeneratedSourceInfo::ConformanceMacroExpansion:
+  case GeneratedSourceInfo::ExtensionMacroExpansion: {
     auto decl = ASTNode::getFromOpaqueValue(generatedSourceInfo->astNode)
       .get<Decl *>();
     auto attr = generatedSourceInfo->attachedMacroCustomAttr;
@@ -3940,6 +3941,10 @@ void ASTMangler::appendMacroExpansionContext(
       role = MacroRole::Conformance;
       break;
 
+    case GeneratedSourceInfo::ExtensionMacroExpansion:
+      role = MacroRole::Extension;
+      break;
+
     default:
       llvm_unreachable("Unhandled macro role");
     }
@@ -4004,6 +4009,10 @@ void ASTMangler::appendMacroExpansionOperator(
   case MacroRole::Conformance:
     appendOperator("fMc", Index(discriminator));
     break;
+
+  case MacroRole::Extension:
+    appendOperator("fMe", Index(discriminator));
+    break;
   }
 }
 

lib/AST/ASTPrinter.cpp

@@ -2853,6 +2853,26 @@ static bool usesFeatureCodeItemMacros(Decl *decl) {
   return macro->getMacroRoles().contains(MacroRole::CodeItem);
 }
 
+static bool usesFeatureExtensionMacros(Decl *decl) {
+  auto macro = dyn_cast<MacroDecl>(decl);
+  if (!macro)
+    return false;
+
+  return macro->getMacroRoles().contains(MacroRole::Extension);
+}
+
+static bool usesFeatureExtensionMacroAttr(Decl *decl) {
+  return usesFeatureExtensionMacros(decl);
+}
+
+static void suppressingFeatureExtensionMacroAttr(PrintOptions &options,
+                                                 llvm::function_ref<void()> action) {
+  bool originalPrintExtensionMacroAttrs = options.PrintExtensionMacroAttributes;
+  options.PrintExtensionMacroAttributes = false;
+  action();
+  options.PrintExtensionMacroAttributes = originalPrintExtensionMacroAttrs;
+}
+
 static bool usesFeatureAttachedMacros(Decl *decl) {
   auto macro = dyn_cast<MacroDecl>(decl);
   if (!macro)

lib/AST/ASTScopeCreation.cpp

@@ -273,6 +273,7 @@ ASTSourceFileScope::ASTSourceFileScope(SourceFile *SF,
     case MacroRole::Accessor:
     case MacroRole::MemberAttribute:
     case MacroRole::Conformance:
+    case MacroRole::Extension:
       parentLoc = expansion.getStartLoc();
       break;
     case MacroRole::Peer: {

lib/AST/Attr.cpp

@@ -1365,6 +1365,13 @@ bool DeclAttribute::printImpl(ASTPrinter &Printer, const PrintOptions &Options,
 
   case DAK_MacroRole: {
     auto Attr = cast<MacroRoleAttr>(this);
+
+    // Suppress @attached(extension) if needed.
+    if (!Options.PrintExtensionMacroAttributes &&
+        Attr->getMacroRole() == MacroRole::Extension) {
+      break;
+    }
+
     switch (Attr->getMacroSyntax()) {
     case MacroSyntax::Freestanding:
       Printer.printAttrName("@freestanding");
@@ -2480,23 +2487,32 @@ MacroRoleAttr::MacroRoleAttr(SourceLoc atLoc, SourceRange range,
                              MacroSyntax syntax, SourceLoc lParenLoc,
                              MacroRole role,
                              ArrayRef<MacroIntroducedDeclName> names,
+                             ArrayRef<TypeExpr *> conformances,
                              SourceLoc rParenLoc, bool implicit)
     : DeclAttribute(DAK_MacroRole, atLoc, range, implicit),
-      syntax(syntax), role(role), numNames(names.size()), lParenLoc(lParenLoc),
+      syntax(syntax), role(role), numNames(names.size()),
+      numConformances(conformances.size()), lParenLoc(lParenLoc),
       rParenLoc(rParenLoc) {
   auto *trailingNamesBuffer = getTrailingObjects<MacroIntroducedDeclName>();
   std::uninitialized_copy(names.begin(), names.end(), trailingNamesBuffer);
+
+  auto *trailingConformancesBuffer = getTrailingObjects<TypeExpr *>();
+  std::uninitialized_copy(conformances.begin(), conformances.end(),
+                          trailingConformancesBuffer);
 }
 
 MacroRoleAttr *
 MacroRoleAttr::create(ASTContext &ctx, SourceLoc atLoc, SourceRange range,
                       MacroSyntax syntax, SourceLoc lParenLoc, MacroRole role,
                       ArrayRef<MacroIntroducedDeclName> names,
+                      ArrayRef<TypeExpr *> conformances,
                       SourceLoc rParenLoc, bool implicit) {
-  unsigned size = totalSizeToAlloc<MacroIntroducedDeclName>(names.size());
+  unsigned size =
+      totalSizeToAlloc<MacroIntroducedDeclName, TypeExpr *>(
+          names.size(), conformances.size());
   auto *mem = ctx.Allocate(size, alignof(MacroRoleAttr));
   return new (mem) MacroRoleAttr(atLoc, range, syntax, lParenLoc, role, names,
-                                 rParenLoc, implicit);
+                                 conformances, rParenLoc, implicit);
 }
 
 ArrayRef<MacroIntroducedDeclName> MacroRoleAttr::getNames() const {
@@ -2506,6 +2522,13 @@ ArrayRef<MacroIntroducedDeclName> MacroRoleAttr::getNames() const {
   };
 }
 
+ArrayRef<TypeExpr *> MacroRoleAttr::getConformances() const {
+  return {
+    getTrailingObjects<TypeExpr *>(),
+    numConformances
+  };
+}
+
 bool MacroRoleAttr::hasNameKind(MacroIntroducedDeclNameKind kind) const {
   return llvm::find_if(getNames(), [kind](MacroIntroducedDeclName name) {
     return name.getKind() == kind;

lib/AST/ConformanceLookupTable.cpp

@@ -286,6 +286,10 @@ void ConformanceLookupTable::updateLookupTable(NominalTypeDecl *nominal,
           ASTContext &ctx = nominal->getASTContext();
           (void)evaluateOrDefault(
               ctx.evaluator, ExpandConformanceMacros{nominal}, { });
+
+          // Expand extension macros.
+          (void)evaluateOrDefault(
+              ctx.evaluator, ExpandExtensionMacros{nominal}, { });
         },
         [&](ExtensionDecl *ext,
             ArrayRef<ConformanceConstructionInfo> protos) {

lib/AST/Decl.cpp

@@ -10352,7 +10352,7 @@ std::vector<MacroRole> swift::getAllMacroRoles() {
   return {
       MacroRole::Expression,      MacroRole::Declaration, MacroRole::Accessor,
       MacroRole::MemberAttribute, MacroRole::Member,      MacroRole::Peer,
-      MacroRole::Conformance,     MacroRole::CodeItem,
+      MacroRole::Conformance,     MacroRole::CodeItem,    MacroRole::Extension,
   };
 }
 
@@ -10381,6 +10381,9 @@ StringRef swift::getMacroRoleString(MacroRole role) {
 
   case MacroRole::CodeItem:
     return "codeItem";
+
+  case MacroRole::Extension:
+    return "extension";
   }
 }
 
@@ -10440,7 +10443,8 @@ static MacroRoles attachedMacroRoles = (MacroRoles() |
                                         MacroRole::MemberAttribute |
                                         MacroRole::Member |
                                         MacroRole::Peer |
-                                        MacroRole::Conformance);
+                                        MacroRole::Conformance |
+                                        MacroRole::Extension);
 
 bool swift::isFreestandingMacro(MacroRoles contexts) {
   return bool(contexts & freestandingMacroRoles);
@@ -10470,6 +10474,8 @@ bool swift::isMacroSupported(MacroRole role, ASTContext &ctx) {
     return true;
   case MacroRole::CodeItem:
     return ctx.LangOpts.hasFeature(Feature::CodeItemMacros);
+  case MacroRole::Extension:
+    return ctx.LangOpts.hasFeature(Feature::ExtensionMacros);
   }
 }
 
@@ -10668,6 +10674,7 @@ void MacroDecl::getIntroducedNames(MacroRole role, ValueDecl *attachedTo,
   case MacroRole::Member:
   case MacroRole::Peer:
   case MacroRole::CodeItem:
+  case MacroRole::Extension:
     names.push_back(MacroDecl::getUniqueNamePlaceholder(getASTContext()));
     break;
 
@@ -10863,6 +10870,7 @@ MacroDiscriminatorContext MacroDiscriminatorContext::getParentOf(
   case GeneratedSourceInfo::MemberMacroExpansion:
   case GeneratedSourceInfo::PeerMacroExpansion:
   case GeneratedSourceInfo::ConformanceMacroExpansion:
+  case GeneratedSourceInfo::ExtensionMacroExpansion:
   case GeneratedSourceInfo::PrettyPrinted:
   case GeneratedSourceInfo::ReplacedFunctionBody:
     return origDC;

lib/AST/DiagnosticEngine.cpp

@@ -1288,6 +1288,7 @@ DiagnosticEngine::diagnosticInfoForDiagnostic(const Diagnostic &diagnostic) {
       case GeneratedSourceInfo::MemberMacroExpansion:
       case GeneratedSourceInfo::PeerMacroExpansion:
       case GeneratedSourceInfo::ConformanceMacroExpansion:
+      case GeneratedSourceInfo::ExtensionMacroExpansion:
       case GeneratedSourceInfo::PrettyPrinted:
         fixIts = {};
         break;
@@ -1335,7 +1336,8 @@ DiagnosticEngine::getGeneratedSourceBufferNotes(SourceLoc loc) {
     case GeneratedSourceInfo::MemberAttributeMacroExpansion:
     case GeneratedSourceInfo::MemberMacroExpansion:
     case GeneratedSourceInfo::PeerMacroExpansion:
-    case GeneratedSourceInfo::ConformanceMacroExpansion: {
+    case GeneratedSourceInfo::ConformanceMacroExpansion:
+    case GeneratedSourceInfo::ExtensionMacroExpansion: {
       SourceRange origRange = expansionNode.getSourceRange();
       DeclName macroName = getGeneratedSourceInfoMacroName(*generatedInfo);
 
@@ -1533,7 +1535,8 @@ swift::getGeneratedSourceInfoMacroName(const GeneratedSourceInfo &info) {
   case GeneratedSourceInfo::MemberAttributeMacroExpansion:
   case GeneratedSourceInfo::MemberMacroExpansion:
   case GeneratedSourceInfo::PeerMacroExpansion:
-  case GeneratedSourceInfo::ConformanceMacroExpansion: {
+  case GeneratedSourceInfo::ConformanceMacroExpansion:
+  case GeneratedSourceInfo::ExtensionMacroExpansion: {
     DeclName macroName;
     if (auto customAttr = info.attachedMacroCustomAttr) {
       // FIXME: How will we handle deserialized custom attributes like this?

lib/AST/Module.cpp

@@ -848,7 +848,8 @@ ModuleDecl::getOriginalLocation(SourceLoc loc) const {
     case GeneratedSourceInfo::MemberAttributeMacroExpansion:
     case GeneratedSourceInfo::MemberMacroExpansion:
     case GeneratedSourceInfo::PeerMacroExpansion:
-    case GeneratedSourceInfo::ConformanceMacroExpansion: {
+    case GeneratedSourceInfo::ConformanceMacroExpansion:
+    case GeneratedSourceInfo::ExtensionMacroExpansion: {
       // Location was within a macro expansion, return the expansion site, not
       // the insertion location.
       if (info->attachedMacroCustomAttr) {
@@ -1158,6 +1159,9 @@ Optional<MacroRole> SourceFile::getFulfilledMacroRole() const {
   case GeneratedSourceInfo::ConformanceMacroExpansion:
     return MacroRole::Conformance;
 
+  case GeneratedSourceInfo::ExtensionMacroExpansion:
+    return MacroRole::Extension;
+
   case GeneratedSourceInfo::ReplacedFunctionBody:
   case GeneratedSourceInfo::PrettyPrinted:
     return None;