Revert "🌸 Enable @objc @implementation in the form approved by SE-0436"

include/swift/AST/Attr.h

@@ -2422,9 +2422,6 @@ class DocumentationAttr: public DeclAttribute {
 
 class ObjCImplementationAttr final : public DeclAttribute {
 public:
-  /// Name of the category being implemented. This should only be used with
-  /// the early adopter \@\_objcImplementation syntax, but we support it there
-  /// for backwards compatibility.
   Identifier CategoryName;
 
   ObjCImplementationAttr(Identifier CategoryName, SourceLoc AtLoc,

include/swift/AST/Decl.h

@@ -1025,10 +1025,6 @@ class alignas(1 << DeclAlignInBits) Decl : public ASTAllocated<Decl> {
   /// Returns the source range of the declaration including its attributes.
   SourceRange getSourceRangeIncludingAttrs() const;
 
-  /// Retrieve the location at which we should insert a new attribute or
-  /// modifier.
-  SourceLoc getAttributeInsertionLoc(bool forModifier) const;
-
   using ImportAccessLevel = std::optional<AttributedImport<ImportedModule>>;
 
   /// Returns the import that may restrict the access to this decl
@@ -1920,6 +1916,11 @@ class ExtensionDecl final : public GenericContext, public Decl,
   /// extended type?
   bool isAddingConformanceToInvertible() const;
 
+  /// Returns the name of the category specified by the \c \@_objcImplementation
+  /// attribute, or \c None if the name is invalid or
+  /// \c isObjCImplementation() is false.
+  std::optional<Identifier> getCategoryNameForObjCImplementation() const;
+
   /// If this extension represents an imported Objective-C category, returns the
   /// category's name. Otherwise returns the empty identifier.
   Identifier getObjCCategoryName() const;
@@ -3180,6 +3181,10 @@ class ValueDecl : public Decl {
   /// can't be "static" or are in a context where "static" doesn't make sense.
   bool isStatic() const;
 
+  /// Retrieve the location at which we should insert a new attribute or
+  /// modifier.
+  SourceLoc getAttributeInsertionLoc(bool forModifier) const;
+
   static bool classof(const Decl *D) {
     return D->getKind() >= DeclKind::First_ValueDecl &&
            D->getKind() <= DeclKind::Last_ValueDecl;
@@ -4210,12 +4215,6 @@ class NominalTypeDecl : public GenericTypeDecl, public IterableDeclContext {
   /// Retrieve the set of extensions of this type.
   ExtensionRange getExtensions();
 
-  /// Retrieve the extension most recently added to this type. Helpful to
-  /// determine if an extension has been added.
-  ExtensionDecl *getLastExtension() const {
-    return LastExtension;
-  }
-
   /// Special-behaviour flags passed to lookupDirect()
   enum class LookupDirectFlags {
     /// Whether to include @_implements members.
@@ -5081,11 +5080,6 @@ class ClassDecl final : public NominalTypeDecl {
   llvm::TinyPtrVector<Decl *>
   getImportedObjCCategory(Identifier name) const;
 
-  /// Return a map of category names to extensions with that category name,
-  /// whether imported or otherwise. 
-  llvm::DenseMap<Identifier, llvm::TinyPtrVector<ExtensionDecl *>>
-  getObjCCategoryNameMap();
-
   // Implement isa/cast/dyncast/etc.
   static bool classof(const Decl *D) {
     return D->getKind() == DeclKind::Class;

include/swift/AST/DiagnosticsClangImporter.def

@@ -136,10 +136,12 @@ WARNING(api_pattern_attr_ignored, none,
         (StringRef, StringRef))
 
 ERROR(objc_implementation_two_impls, none,
-      "duplicate implementation of imported %kind0",
-      (Decl *))
+      "duplicate implementation of Objective-C %select{|category %0 on }0"
+      "%kind1",
+      (Identifier, Decl *))
+
 NOTE(previous_objc_implementation, none,
-     "previously implemented here", ())
+     "previously implemented by extension here", ())
 
 NOTE(macro_not_imported_unsupported_operator, none, "operator not supported in macro arithmetic", ())
 NOTE(macro_not_imported_unsupported_named_operator, none, "operator '%0' not supported in macro arithmetic", (StringRef))

include/swift/AST/DiagnosticsIRGen.def

@@ -69,16 +69,5 @@ NOTE(layout_strings_blocked,none,
      "Layout string value witnesses have been disabled for module '%0' "
      "through block list entry", (StringRef))
 
-ERROR(attr_objc_implementation_resilient_property_not_supported, none,
-      "'@implementation' does not support stored properties whose size can "
-      "change due to library evolution; store this value in an object or 'any' "
-      "type",
-      ())
-ERROR(attr_objc_implementation_resilient_property_deployment_target, none,
-      "'@implementation' on %0 %1 does not support stored properties whose "
-      "size can change due to library evolution; raise the minimum deployment "
-      "target to %0 %2 or store this value in an object or 'any' type",
-      (StringRef, const llvm::VersionTuple, const llvm::VersionTuple))
-
 #define UNDEFINE_DIAGNOSTIC_MACROS
 #include "DefineDiagnosticMacros.h"

include/swift/AST/DiagnosticsSema.def

@@ -763,9 +763,6 @@ ERROR(expr_selector_not_objc,none,
 NOTE(make_decl_objc,none,
      "add '@objc' to expose this %0 to Objective-C",
      (DescriptiveDeclKind))
-NOTE(make_decl_objc_for_implementation,none,
-     "add '@objc' to implement an Objective-C %0",
-     (DescriptiveDeclKind))
 
 // Selectors-as-string-literals.
 WARNING(selector_literal_invalid,none,
@@ -1763,17 +1760,21 @@ WARNING(objc_implementation_early_spelling_deprecated,none,
 ERROR(attr_objc_implementation_must_be_unconditional,none,
       "only unconditional extensions can implement an Objective-C '@interface'",
       ())
+ERROR(attr_objc_implementation_must_extend_class,none,
+      "cannot mark extension of %kind0 with '@_objcImplementation'; it is not "
+      "an imported Objective-C class",
+      (ValueDecl *))
 ERROR(attr_objc_implementation_must_be_imported,none,
-      "'@objc @implementation' cannot be used to extend %kind0 because it was "
+      "'@_objcImplementation' cannot be used to extend %kind0 because it was "
       "defined by a Swift 'class' declaration, not an imported Objective-C "
       "'@interface' declaration",
       (ValueDecl *))
 ERROR(attr_objc_implementation_must_have_super,none,
-      "'@objc @implementation' cannot be used to implement root %kind0; "
-      "declare its superclass in the header",
+      "'@_objcImplementation' cannot be used to implement root %kind0; declare "
+      "its superclass in the header",
       (ValueDecl *))
 ERROR(objc_implementation_cannot_have_generics,none,
-      "'@objc @implementation' cannot be used to implement %kind0",
+      "'@_objcImplementation' cannot be used to implement %kind0",
       (ValueDecl *))
 ERROR(attr_objc_implementation_category_not_found,none,
       "could not find category %0 on Objective-C class %1; make sure your "
@@ -1791,22 +1792,10 @@ ERROR(attr_objc_implementation_no_category_for_func,none,
       "name from this attribute",
       (ValueDecl*))
 ERROR(attr_objc_implementation_no_conformance,none,
-      "'@objc @implementation' extension cannot add conformance to %0; "
+      "'@_objcImplementation' extension cannot add conformance to %0; "
       "add this conformance %select{with an ordinary extension|"
       "in the Objective-C header}1",
       (Type, bool))
-ERROR(attr_objc_implementation_raise_minimum_deployment_target,none,
-      "'@implementation' of an Objective-C class requires a minimum deployment "
-      "target of at least %0 %1",
-      (StringRef, llvm::VersionTuple))
-ERROR(attr_implementation_requires_language,none,
-      "'@implementation' used without specifying the language being "
-      "implemented",
-      ())
-ERROR(attr_implementation_category_goes_on_objc_attr,none,
-      "Objective-C category should be specified on '@objc', not "
-      "'@implementation'",
-      ())
 
 ERROR(member_of_objc_implementation_not_objc_or_final,none,
       "%kind0 does not match any %kindonly0 declared in the headers for %1; "
@@ -1919,7 +1908,7 @@ NOTE(objc_implementation_requirement_here,none,
      (ValueDecl *))
 
 ERROR(objc_implementation_init_must_be_convenience, none,
-      "%kind0 is not valid in an '@objc @implementation' extension because "
+      "%kind0 is not valid in an '@_objcImplementation' extension because "
       "Objective-C subclasses must be able to override "
       "%select{designated|required}1 initializers",
       (const ValueDecl *, /*isRequired=*/bool))
@@ -1933,7 +1922,7 @@ NOTE(objc_implementation_init_turn_required_to_convenience, none,
 
 // Fallback diagnostic; super-general by nature.
 ERROR(objc_implementation_member_requires_vtable, none,
-      "%kind0 is not valid in an '@objc @implementation' extension because it "
+      "%kind0 is not valid in an '@_objcImplementation' extension because it "
       "is an overridable Swift-only %kindonly0",
       (const ValueDecl *))
 
@@ -6304,7 +6293,7 @@ ERROR(objc_extension_not_class,none,
       "'@objc' can only be applied to an extension of a class", ())
 
 // If you change this, also change enum ObjCReason
-#define OBJC_ATTR_SELECT "select{marked @_cdecl|marked dynamic|marked @objc|marked @objcMembers|marked @IBOutlet|marked @IBAction|marked @IBSegueAction|marked @NSManaged|a member of an @objc protocol|implicitly @objc|an @objc override|an implementation of an @objc requirement|marked @IBInspectable|marked @GKInspectable|in an @objc extension of a class (without @nonobjc)|in an @objc @implementation extension of a class (without final or @nonobjc)|marked @objc by an access note}"
+#define OBJC_ATTR_SELECT "select{marked @_cdecl|marked dynamic|marked @objc|marked @objcMembers|marked @IBOutlet|marked @IBAction|marked @IBSegueAction|marked @NSManaged|a member of an @objc protocol|implicitly @objc|an @objc override|an implementation of an @objc requirement|marked @IBInspectable|marked @GKInspectable|in an @objc extension of a class (without @nonobjc)|in an @_objcImplementation extension of a class (without final or @nonobjc)|marked @objc by an access note}"
 
 ERROR(objc_invalid_on_var,none,
       "property cannot be %" OBJC_ATTR_SELECT "0 "
@@ -6459,12 +6448,6 @@ ERROR(objc_redecl_same,none,
       "previous declaration with the same Objective-C selector",
       (unsigned, DeclName, unsigned, DeclName, ObjCSelector))
 
-ERROR(objc_redecl_category_name,none,
-      "%select{|imported }0extension with Objective-C category name %2 "
-      "conflicts with previous %select{|imported }1extension with the same "
-      "category name",
-      (bool, bool, Identifier))
-
 ERROR(objc_override_other,none,
       OBJC_DIAG_SELECT " with Objective-C selector %4 conflicts with "
       OBJC_DIAG_SELECT_2 " from superclass %5 with the same Objective-C "

include/swift/AST/FeatureAvailability.def

@@ -76,7 +76,6 @@ FEATURE(NoncopyableGenerics,                            (6, 0))
 FEATURE(TaskExecutor,                                   FUTURE)
 FEATURE(Differentiation,                                FUTURE)
 FEATURE(InitRawStructMetadata,                          FUTURE)
-FEATURE(UpdatePureObjCClassMetadata,                    FUTURE)
 
 #undef FEATURE
 #undef FUTURE

include/swift/AST/NameLookupRequests.h

@@ -970,39 +970,6 @@ class LookupIntrinsicRequest
   bool isCached() const { return true; }
 };
 
-using ObjCCategoryNameMap =
-  llvm::DenseMap<Identifier, llvm::TinyPtrVector<ExtensionDecl *>>;
-
-/// Generate a map of all known extensions of the given class that have an
-/// explicit category name. This request does not force clang categories that
-/// haven't been imported already, but it will generate a new map if new
-/// categories have been imported since the cached value was generated.
-///
-/// \seeAlso ClassDecl::getObjCCategoryNameMap()
-class ObjCCategoryNameMapRequest
-    : public SimpleRequest<ObjCCategoryNameMapRequest,
-                           ObjCCategoryNameMap(ClassDecl *, ExtensionDecl *),
-                           RequestFlags::Cached> {
-public:
-  using SimpleRequest::SimpleRequest;
-
-  // Convenience to automatically extract `lastExtension`.
-  ObjCCategoryNameMapRequest(ClassDecl *classDecl)
-    : ObjCCategoryNameMapRequest(classDecl, classDecl->getLastExtension())
-  {}
-
-private:
-  friend SimpleRequest;
-
-  // Evaluation.
-  ObjCCategoryNameMap evaluate(Evaluator &evaluator,
-                               ClassDecl *classDecl,
-                               ExtensionDecl *lastExtension) const;
-
-public:
-  bool isCached() const { return true; }
-};
-
 #define SWIFT_TYPEID_ZONE NameLookup
 #define SWIFT_TYPEID_HEADER "swift/AST/NameLookupTypeIDZone.def"
 #include "swift/Basic/DefineTypeIDZone.h"

include/swift/AST/NameLookupTypeIDZone.def

@@ -116,5 +116,3 @@ SWIFT_REQUEST(NameLookup, ImplementsAttrProtocolRequest,
               ProtocolDecl *(const ImplementsAttr *, DeclContext *), Cached, NoLocationInfo)
 SWIFT_REQUEST(NameLookup, LookupIntrinsicRequest,
               FuncDecl *(ModuleDecl *, Identifier), Cached, NoLocationInfo)
-SWIFT_REQUEST(NameLookup, ObjCCategoryNameMapRequest,
-              ObjCCategoryNameMap(ClassDecl *, ExtensionDecl *), Cached, NoLocationInfo)

include/swift/AST/SourceFile.h

@@ -359,10 +359,6 @@ class SourceFile final : public FileUnit {
   /// List of Objective-C member conflicts we have found during type checking.
   llvm::SetVector<ObjCMethodConflict> ObjCMethodConflicts;
 
-  /// Categories (extensions with explicit @objc names) declared in this
-  /// source file. They need to be checked for conflicts after type checking.
-  llvm::TinyPtrVector<ExtensionDecl *> ObjCCategories;
-
   /// List of attributes added by access notes, used to emit remarks for valid
   /// ones.
   llvm::DenseMap<ValueDecl *, std::vector<DeclAttribute *>>

include/swift/Basic/Features.def

@@ -202,7 +202,6 @@ SUPPRESSIBLE_LANGUAGE_FEATURE(SendingArgsAndResults, 430, "Sending arg and resul
 LANGUAGE_FEATURE(BorrowingSwitch, 432, "Noncopyable type pattern matching")
 CONDITIONALLY_SUPPRESSIBLE_LANGUAGE_FEATURE(IsolatedAny, 431, "@isolated(any) function types")
 LANGUAGE_FEATURE(IsolatedAny2, 431, "@isolated(any) function types")
-LANGUAGE_FEATURE(ObjCImplementation, 436, "@objc @implementation extensions")
 
 // Swift 6
 UPCOMING_FEATURE(ConciseMagicFile, 274, 6)
@@ -377,10 +376,8 @@ EXPERIMENTAL_FEATURE(ClosureIsolation, true)
 // Whether lookup of members respects the enclosing file's imports.
 EXPERIMENTAL_FEATURE_EXCLUDED_FROM_MODULE_INTERFACE(MemberImportVisibility, true)
 
-// Enable @implementation on extensions of ObjC classes with non-fixed layout
-// due to resilient stored properties. Requires OS support; this flag exists for
-// staging purposes.
-EXPERIMENTAL_FEATURE(ObjCImplementationWithResilientStorage, true)
+// Enable @implementation on extensions of ObjC classes.
+EXPERIMENTAL_FEATURE(ObjCImplementation, true)
 
 // Enable @implementation on @_cdecl functions.
 EXPERIMENTAL_FEATURE(CImplementation, true)

include/swift/ClangImporter/ClangImporterRequests.h

@@ -256,7 +256,7 @@ struct ObjCInterfaceAndImplementation final {
   ObjCInterfaceAndImplementation()
       : interfaceDecls(), implementationDecl(nullptr) {}
 
-  bool empty() const {
+  operator bool() const {
     return interfaceDecls.empty();
   }
 

include/swift/Runtime/Metadata.h

@@ -782,13 +782,6 @@ swift_updateClassMetadata2(ClassMetadata *self,
                            size_t numFields,
                            const TypeLayout * const *fieldTypes,
                            size_t *fieldOffsets);
-
-SWIFT_RUNTIME_EXPORT SWIFT_CC(swift)
-Class
-swift_updatePureObjCClassMetadata(Class self,
-                                  ClassLayoutFlags flags,
-                                  size_t numFields,
-                                  const TypeLayout * const *fieldTypes);
 #endif
 
 /// Given class metadata, a class descriptor and a method descriptor, look up

include/swift/Runtime/RuntimeFunctions.def

@@ -1437,19 +1437,6 @@ FUNCTION(UpdateClassMetadata2,
          EFFECT(MetaData),
          UNKNOWN_MEMEFFECTS)
 
-// objc_class *swift_updatePureObjCClassMetadata(
-//             objc_class *self,
-//             ClassLayoutFlags flags,
-//             size_t numFields,
-//             TypeLayout * const *fieldTypes);
-FUNCTION(UpdatePureObjCClassMetadata,
-         swift_updatePureObjCClassMetadata, SwiftCC, AlwaysAvailable,
-         RETURNS(ObjCClassPtrTy),
-         ARGS(ObjCClassPtrTy, SizeTy, SizeTy, Int8PtrPtrTy->getPointerTo()),
-         ATTRS(NoUnwind),
-         EFFECT(MetaData),
-         UNKNOWN_MEMEFFECTS)
-
 // void *swift_lookUpClassMethod(Metadata *metadata,
 //                               ClassDescriptor *description,
 //                               MethodDescriptor *method);

lib/AST/ASTPrinter.cpp

@@ -1326,14 +1326,6 @@ void PrintAST::printAttributes(const Decl *D) {
     }
   }
 
-  // If we are suppressing @implementation, also suppress @objc on extensions.
-  if (auto ED = dyn_cast<ExtensionDecl>(D)) {
-    if (ED->isObjCImplementation() &&
-            Options.excludeAttrKind(DeclAttrKind::ObjCImplementation)) {
-      Options.ExcludeAttrList.push_back(DeclAttrKind::ObjC);
-    }
-  }
-
   // We will handle ownership specifiers separately.
   if (isa<FuncDecl>(D)) {
     Options.ExcludeAttrList.push_back(DeclAttrKind::Mutating);