[PrintAsObjC] Use enum_extensibility to represent @_frozen

Previously (a03c40c) we assumed all Swift enums were non-frozen in
ObjC, a weird choice in retrospect. Now that we actually distinguish
frozen and non-frozen enums in Swift, we can use the
'enum_extensibility' attribute to mark them as open or closed in ObjC.

Note that this only matters for Swift libraries compiled with
-enable-resilience, i.e. those that might get a new implementation at
runtime. Everyone else is now declaring a "closed" enum, matching the
behavior in Swift.

Author: jrose-apple

lib/AST/Decl.cpp

@@ -3116,6 +3116,11 @@ bool EnumDecl::isExhaustive(const DeclContext *useDC) const {
   if (!accessScope.isPublic())
     return true;
 
+  // All other checks are use-site specific; with no further information, the
+  // enum must be treated non-exhaustively.
+  if (!useDC)
+    return false;
+
   // Enums in the same module as the use site are exhaustive /unless/ the use
   // site is inlinable.
   if (useDC->getParentModule() == containingModule)

lib/PrintAsObjC/PrintAsObjC.cpp

@@ -421,7 +421,9 @@ class ObjCPrinter : private DeclVisitor<ObjCPrinter>,
       os << ", " << customName
          << ", \"" << ED->getName() << "\"";
     }
-    os << ") {\n";
+    os << ", " << (ED->isExhaustive(/*useDC*/nullptr) ? "closed" : "open")
+       << ") {\n";
+
     for (auto Elt : ED->getAllElements()) {
       printDocumentationComment(Elt);
 
@@ -2569,24 +2571,26 @@ class ModuleWriter {
            "#if !defined(SWIFT_ENUM_ATTR)\n"
            "# if defined(__has_attribute) && "
              "__has_attribute(enum_extensibility)\n"
-           "#  define SWIFT_ENUM_ATTR "
-             "__attribute__((enum_extensibility(open)))\n"
+           "#  define SWIFT_ENUM_ATTR(_extensibility) "
+             "__attribute__((enum_extensibility(_extensibility)))\n"
            "# else\n"
-           "#  define SWIFT_ENUM_ATTR\n"
+           "#  define SWIFT_ENUM_ATTR(_extensibility)\n"
            "# endif\n"
            "#endif\n"
            "#if !defined(SWIFT_ENUM)\n"
-           "# define SWIFT_ENUM(_type, _name) "
+           "# define SWIFT_ENUM(_type, _name, _extensibility) "
              "enum _name : _type _name; "
-             "enum SWIFT_ENUM_ATTR SWIFT_ENUM_EXTRA _name : _type\n"
+             "enum SWIFT_ENUM_ATTR(_extensibility) SWIFT_ENUM_EXTRA "
+             "_name : _type\n"
            "# if __has_feature(generalized_swift_name)\n"
-           "#  define SWIFT_ENUM_NAMED(_type, _name, SWIFT_NAME) "
+           "#  define SWIFT_ENUM_NAMED(_type, _name, SWIFT_NAME, "
+             "_extensibility) "
              "enum _name : _type _name SWIFT_COMPILE_NAME(SWIFT_NAME); "
-             "enum SWIFT_COMPILE_NAME(SWIFT_NAME) SWIFT_ENUM_ATTR "
-             "SWIFT_ENUM_EXTRA _name : _type\n"
+             "enum SWIFT_COMPILE_NAME(SWIFT_NAME) "
+             "SWIFT_ENUM_ATTR(_extensibility) SWIFT_ENUM_EXTRA _name : _type\n"
            "# else\n"
-           "#  define SWIFT_ENUM_NAMED(_type, _name, SWIFT_NAME) "
-             "SWIFT_ENUM(_type, _name)\n"
+           "#  define SWIFT_ENUM_NAMED(_type, _name, SWIFT_NAME, "
+             "_extensibility) SWIFT_ENUM(_type, _name, _extensibility)\n"
            "# endif\n"
            "#endif\n"
            "#if !defined(SWIFT_UNAVAILABLE)\n"

test/PrintAsObjC/enums-frozen.swift

@@ -0,0 +1,23 @@
+// RUN: %empty-directory(%t)
+// RUN: %target-swift-frontend(mock-sdk: %clang-importer-sdk) -enable-source-import -emit-module -emit-module-doc -o %t %s -import-objc-header %S/Inputs/enums.h -disable-objc-attr-requires-foundation-module -enable-resilience -module-name enums
+// RUN: %target-swift-frontend(mock-sdk: %clang-importer-sdk) -parse-as-library %t/enums.swiftmodule -typecheck -emit-objc-header-path %t/enums.h -import-objc-header %S/Inputs/enums.h -disable-objc-attr-requires-foundation-module -enable-resilience
+// RUN: %FileCheck %s < %t/enums.h
+// RUN: %check-in-clang %t/enums.h
+// RUN: %check-in-clang -fno-modules -Qunused-arguments %t/enums.h -include Foundation.h -include ctypes.h -include CoreFoundation.h
+
+// REQUIRES: objc_interop
+
+import Foundation
+
+// CHECK-LABEL: typedef SWIFT_ENUM(NSInteger, FrozenEnum, closed) {
+@objc @_frozen public enum FrozenEnum: Int {
+  case yes
+  case no
+}
+
+// CHECK-LABEL: typedef SWIFT_ENUM(NSInteger, NonFrozenEnum, open) {
+@objc public enum NonFrozenEnum: Int {
+  case yes
+  case no
+  case fileNotFound
+}

test/PrintAsObjC/enums.swift

@@ -36,7 +36,7 @@ import Foundation
   @objc func acceptMemberImported(a: Wrapper.Raw, b: Wrapper.Enum, c: Wrapper.Options, d: Wrapper.Typedef, e: Wrapper.Anon, ee: Wrapper.Anon2) {}
 }
 
-// CHECK-LABEL: typedef SWIFT_ENUM_NAMED(NSInteger, ObjcEnumNamed, "EnumNamed") {
+// CHECK-LABEL: typedef SWIFT_ENUM_NAMED(NSInteger, ObjcEnumNamed, "EnumNamed", closed) {
 // CHECK-NEXT:   ObjcEnumNamedA = 0,
 // CHECK-NEXT:   ObjcEnumNamedB = 1,
 // CHECK-NEXT:   ObjcEnumNamedC = 2,
@@ -48,7 +48,7 @@ import Foundation
   case A, B, C, d, helloDolly
 }
 
-// CHECK-LABEL: typedef SWIFT_ENUM(NSInteger, EnumWithNamedConstants) {
+// CHECK-LABEL: typedef SWIFT_ENUM(NSInteger, EnumWithNamedConstants, closed) {
 // CHECK-NEXT:   kEnumA SWIFT_COMPILE_NAME("A") = 0,
 // CHECK-NEXT:   kEnumB SWIFT_COMPILE_NAME("B") = 1,
 // CHECK-NEXT:   kEnumC SWIFT_COMPILE_NAME("C") = 2,
@@ -60,7 +60,7 @@ import Foundation
   @objc(kEnumC) case C
 }
 
-// CHECK-LABEL: typedef SWIFT_ENUM(unsigned int, ExplicitValues) {
+// CHECK-LABEL: typedef SWIFT_ENUM(unsigned int, ExplicitValues, closed) {
 // CHECK-NEXT:   ExplicitValuesZim = 0,
 // CHECK-NEXT:   ExplicitValuesZang = 219,
 // CHECK-NEXT:   ExplicitValuesZung = 220,
@@ -74,7 +74,7 @@ import Foundation
 }
 
 // CHECK: /// Foo: A feer, a female feer.
-// CHECK-NEXT: typedef SWIFT_ENUM(NSInteger, FooComments) {
+// CHECK-NEXT: typedef SWIFT_ENUM(NSInteger, FooComments, closed) {
 // CHECK: /// Zim: A zeer, a female zeer.
 // CHECK-NEXT:   FooCommentsZim = 0,
 // CHECK-NEXT:   FooCommentsZang = 1,
@@ -88,7 +88,7 @@ import Foundation
   case Zang, Zung
 }
 
-// CHECK-LABEL: typedef SWIFT_ENUM(int16_t, NegativeValues) {
+// CHECK-LABEL: typedef SWIFT_ENUM(int16_t, NegativeValues, closed) {
 // CHECK-NEXT:   Zang = -219,
 // CHECK-NEXT:   Zung = -218,
 // CHECK-NEXT: };
@@ -98,7 +98,7 @@ import Foundation
   func methodNotExportedToObjC() {}
 }
 
-// CHECK-LABEL: typedef SWIFT_ENUM(NSInteger, SomeError) {
+// CHECK-LABEL: typedef SWIFT_ENUM(NSInteger, SomeError, closed) {
 // CHECK-NEXT:   SomeErrorBadness = 9001,
 // CHECK-NEXT:   SomeErrorWorseness = 9002,
 // CHECK-NEXT: };
@@ -108,15 +108,15 @@ import Foundation
   case Worseness
 }
 
-// CHECK-LABEL: typedef SWIFT_ENUM(NSInteger, SomeOtherError) {
+// CHECK-LABEL: typedef SWIFT_ENUM(NSInteger, SomeOtherError, closed) {
 // CHECK-NEXT:   SomeOtherErrorDomain = 0,
 // CHECK-NEXT: };
 // NEGATIVE-NOT: NSString * _Nonnull const SomeOtherErrorDomain
 @objc enum SomeOtherError: Int, Error {
   case Domain // collision!
 }
 
-// CHECK-LABEL: typedef SWIFT_ENUM_NAMED(NSInteger, ObjcErrorType, "SomeRenamedErrorType") {
+// CHECK-LABEL: typedef SWIFT_ENUM_NAMED(NSInteger, ObjcErrorType, "SomeRenamedErrorType", closed) {
 // CHECK-NEXT:   ObjcErrorTypeBadStuff = 0,
 // CHECK-NEXT: };
 // CHECK-NEXT: static NSString * _Nonnull const ObjcErrorTypeDomain = @"enums.SomeRenamedErrorType";
@@ -133,4 +133,3 @@ import Foundation
     return .Zung
   }
 }
-

test/PrintAsObjC/swift_name.swift

@@ -38,6 +38,6 @@ public enum TestE : Int{
 	case A1
 	case B1
 }
-// CHECK: typedef SWIFT_ENUM(NSInteger, TestE)
+// CHECK: typedef SWIFT_ENUM(NSInteger, TestE, closed)
 // CHECK-NEXT: {{^}} A2 SWIFT_COMPILE_NAME("A1") = 0,
 // CHECK-NEXT: {{^}} TestEB1 = 1,