[PrintAsObjC] Reintroduce +new when reintroducing -init. (#13320)

Follow-up to 49c65facc9 to account for subclasses. An unavailable
-init makes +new unavailable, but reintroducing it in a subclass
should reintroduce +new if the root class is NSObject (where +new is
implemented).

rdar://problem/35914080

lib/PrintAsObjC/PrintAsObjC.cpp

@@ -501,6 +501,12 @@ private:
     return result;
   }
 
+  /// Returns true if \p sel is the no-argument selector 'init'.
+  static bool selectorIsInit(ObjCSelector sel) {
+    return sel.getNumArgs() == 0 &&
+           sel.getSelectorPieces().front().str() == "init";
+  }
+                                          
   void printAbstractFunctionAsMethod(AbstractFunctionDecl *AFD,
                                      bool isClassMethod,
                                      bool isNSUIntegerSubscript = false) {
@@ -605,6 +611,7 @@ private:
 
     bool skipAvailability = false;
     bool makeNewUnavailable = false;
+    bool makeNewExplicitlyAvailable = false;
     // Swift designated initializers are Objective-C designated initializers.
     if (auto ctor = dyn_cast<ConstructorDecl>(AFD)) {
       if (ctor->hasStubImplementation()
@@ -614,12 +621,34 @@ private:
         os << " SWIFT_UNAVAILABLE";
         skipAvailability = true;
         // If -init is unavailable, then +new should be, too:
-        const bool selectorIsInit = selector.getNumArgs() == 0 && selectorPieces.front().str() == "init";
+        makeNewUnavailable = selectorIsInit(selector);
-        makeNewUnavailable = selectorIsInit;
+      } else {
-      } else if (ctor->isDesignatedInit() &&
+        if (ctor->isDesignatedInit() &&
-          !isa<ProtocolDecl>(ctor->getDeclContext())) {
+            !isa<ProtocolDecl>(ctor->getDeclContext())) {
-        os << " OBJC_DESIGNATED_INITIALIZER";
+          os << " OBJC_DESIGNATED_INITIALIZER";
+        }
+
+        // If -init is newly available, +new should be as well if the class
+        // inherits from NSObject.
+        if (selectorIsInit(selector) && !ctor->getOverriddenDecl()) {
+          auto container = ctor->getDeclContext();
+          auto *classDecl = container->getAsClassOrClassExtensionContext();
+          if (!classDecl) {
+            assert(container->getAsProtocolOrProtocolExtensionContext());
+          } else {
+            while (classDecl->hasSuperclass()) {
+              classDecl = classDecl->getSuperclassDecl();
+              assert(classDecl &&
+                     "shouldn't PrintAsObjC with invalid superclasses");
+            }
+            if (classDecl->hasClangNode() &&
+                classDecl->getNameStr() == "NSObject") {
+              makeNewExplicitlyAvailable = true;
+            }
+          }
+        }
       }
+
       if (!looksLikeInitMethod(AFD->getObjCSelector())) {
         os << " SWIFT_METHOD_FAMILY(init)";
       }
@@ -649,7 +678,10 @@ private:
     os << ";\n";
 
     if (makeNewUnavailable) {
-        os << "+ (nonnull instancetype)new SWIFT_UNAVAILABLE;\n";
+      assert(!makeNewExplicitlyAvailable);
+      os << "+ (nonnull instancetype)new SWIFT_UNAVAILABLE;\n";
+    } else if (makeNewExplicitlyAvailable) {
+      os << "+ (nonnull instancetype)new;\n";
     }
   }
 

test/PrintAsObjC/classes.swift

@@ -433,6 +433,41 @@ class MyObject : NSObject {}
   @objc class Subclass : NestedSuperclass {}
 }
 
+// CHECK-LABEL: @interface NewBanned
+// CHECK-NEXT: - (nonnull instancetype)initWithArbitraryArgument:(NSInteger)arbitraryArgument OBJC_DESIGNATED_INITIALIZER;
+// CHECK-NEXT: - (nonnull instancetype)init SWIFT_UNAVAILABLE;
+// CHECK-NEXT: + (nonnull instancetype)new SWIFT_UNAVAILABLE;
+// CHECK-NEXT: @end
+@objc class NewBanned : NSObject {
+  init(arbitraryArgument: Int) { super.init() }
+}
+
+// CHECK-LABEL: @interface NewBanned
+// CHECK-NEXT: - (nonnull instancetype)initWithDifferentArbitraryArgument:(NSInteger)differentArbitraryArgument OBJC_DESIGNATED_INITIALIZER;
+// CHECK-NEXT: - (nonnull instancetype)initWithArbitraryArgument:(NSInteger)arbitraryArgument SWIFT_UNAVAILABLE;
+// CHECK-NEXT: @end
+@objc class NewBannedStill : NewBanned {
+  init(differentArbitraryArgument: Int) { super.init(arbitraryArgument: 0) }
+}
+
+// CHECK-LABEL: @interface NewUnbanned
+// CHECK-NEXT: - (nonnull instancetype)init OBJC_DESIGNATED_INITIALIZER;
+// CHECK-NEXT: + (nonnull instancetype)new;
+// CHECK-NEXT: - (nonnull instancetype)initWithArbitraryArgument:(NSInteger)arbitraryArgument SWIFT_UNAVAILABLE;
+// CHECK-NEXT: @end
+@objc class NewUnbanned : NewBanned {
+  init() { super.init(arbitraryArgument: 0) }
+}
+
+// CHECK-LABEL: @interface NewUnbannedDouble
+// CHECK-NEXT: - (nonnull instancetype)init OBJC_DESIGNATED_INITIALIZER;
+// CHECK-NEXT: + (nonnull instancetype)new;
+// CHECK-NEXT: - (nonnull instancetype)initWithDifferentArbitraryArgument:(NSInteger)differentArbitraryArgument SWIFT_UNAVAILABLE;
+// CHECK-NEXT: @end
+@objc class NewUnbannedDouble : NewBannedStill {
+  init() { super.init(differentArbitraryArgument: 0) }
+}
+
 // NEGATIVE-NOT: @interface Private :
 private class Private : A1 {}
 

validation-test/PrintAsObjC/Inputs/reintroduced-new.swift

@@ -0,0 +1,8 @@
+import ObjectiveC
+
+public class Base : NSObject {
+  public init(foo: Int) { super.init() }
+}
+public class Sub: Base {
+  @objc public init() { super.init(foo: 0) }
+}

validation-test/PrintAsObjC/reintroduced-new.m

@@ -0,0 +1,26 @@
+// REQUIRES: objc_interop
+
+// RUN: %empty-directory(%t)
+
+// FIXME: BEGIN -enable-source-import hackaround
+// RUN:  %target-swift-frontend(mock-sdk: -sdk %S/../../test/Inputs/clang-importer-sdk -I %t) -emit-module -o %t %S/../../test/Inputs/clang-importer-sdk/swift-modules/ObjectiveC.swift
+// FIXME: END -enable-source-import hackaround
+
+// RUN: %target-swift-frontend(mock-sdk: -sdk %S/../../test/Inputs/clang-importer-sdk -I %t) -emit-module -o %t %S/Inputs/reintroduced-new.swift -disable-objc-attr-requires-foundation-module -module-name main
+// RUN: %target-swift-frontend(mock-sdk: -sdk %S/../../test/Inputs/clang-importer-sdk -I %t) -parse-as-library %t/main.swiftmodule -typecheck -emit-objc-header-path %t/generated.h -disable-objc-attr-requires-foundation-module
+// RUN: not %clang -fsyntax-only -x objective-c %s -include %t/generated.h -fobjc-arc -fmodules -Werror -isysroot %S/../../test/Inputs/clang-importer-sdk 2>&1 | %FileCheck %s
+
+// CHECK-NOT: error:
+
+void test() {
+  // CHECK: :[[@LINE+1]]:{{[0-9]+}}: error: 'init' is unavailable
+  (void)[[Base alloc] init];
+   // CHECK-NOT: error:
+  (void)[[Sub alloc] init];
+  // CHECK: :[[@LINE+1]]:{{[0-9]+}}: error: 'new' is unavailable
+  (void)[Base new];
+   // CHECK-NOT: error:
+  (void)[Sub new];
+}
+
+// CHECK-NOT: error: