Sema: Diagnose unsupported '@objc' on classes and members of extensions of classes with resilient ancestry

Unless -enable-resilient-objc-class-stubs is passed in, these cases
are not supported, so now we diagnose them instead of asserting or
failing to link.

Note the behavior change here; classes with resilient ancestry were
previously isObjC(). However this is wrong since isObjC() means
"statically visible to Objective-C via the generated header".

After this patch, isObjC() only returns true for a class with resilient
ancestry if -enable-resilient-objc-class-stubs is passed in.

Author: slavapestov

include/swift/AST/DiagnosticsSema.def

@@ -3592,9 +3592,11 @@ ERROR(invalid_nonobjc_extension,none,
 ERROR(objc_in_extension_context,none,
       "members of constrained extensions cannot be declared @objc", ())
 ERROR(objc_in_generic_extension,none,
-      "members of extensions of "
-      "%select{classes from generic context|generic classes}0 "
-      "cannot be declared @objc", (bool))
+      "extensions of %select{classes from generic context|generic classes}0 "
+      "cannot contain '@objc' members", (bool))
+ERROR(objc_in_resilient_extension,none,
+      "extensions of classes built with library evolution support "
+      "cannot contain '@objc' members", ())
 ERROR(objc_operator, none,
       "operator methods cannot be declared @objc", ())
 ERROR(objc_operator_proto, none,
@@ -3615,6 +3617,10 @@ NOTE(objc_inference_swift3_addnonobjc,none,
 ERROR(objc_for_generic_class,none,
       "generic subclasses of '@objc' classes cannot have an explicit '@objc' "
       "because they are not directly visible from Objective-C", ())
+ERROR(objc_for_resilient_class,none,
+      "classes built with library evolution support cannot have explicit "
+      "'@objc' subclasses because they are not directly "
+      "visible from Objective-C", ())
 ERROR(objc_getter_for_nonobjc_property,none,
       "'@objc' getter for non-'@objc' property", ())
 ERROR(objc_getter_for_nonobjc_subscript,none,

lib/Sema/TypeCheckDeclObjC.cpp

@@ -383,6 +383,21 @@ static bool checkObjCInExtensionContext(const ValueDecl *value,
     }
 
     if (auto classDecl = ED->getSelfClassDecl()) {
+      auto *mod = value->getModuleContext();
+      auto &ctx = mod->getASTContext();
+
+      if (!ctx.LangOpts.EnableObjCResilientClassStubs) {
+        if (classDecl->checkAncestry().contains(
+              AncestryFlags::ResilientOther) ||
+            classDecl->hasResilientMetadata(mod,
+                                            ResilienceExpansion::Maximal)) {
+          if (diagnose) {
+            value->diagnose(diag::objc_in_resilient_extension);
+          }
+          return true;
+        }
+      }
+
       if (classDecl->isGenericContext()) {
         if (!classDecl->usesObjCGenericsModel()) {
           if (diagnose) {
@@ -1016,6 +1031,20 @@ static Optional<ObjCReason> shouldMarkClassAsObjC(const ClassDecl *CD) {
         .fixItRemove(attr->getRangeWithAt());
     }
 
+    // If the class has resilient ancestry, @objc just controls the runtime
+    // name unless -enable-resilient-objc-class-stubs is enabled.
+    if (ancestry.contains(AncestryFlags::ResilientOther) &&
+        !ctx.LangOpts.EnableObjCResilientClassStubs) {
+      if (attr->hasName()) {
+        const_cast<ClassDecl *>(CD)->getAttrs().add(
+          new (ctx) ObjCRuntimeNameAttr(*attr));
+        return None;
+      }
+
+      ctx.Diags.diagnose(attr->getLocation(), diag::objc_for_resilient_class)
+        .fixItRemove(attr->getRangeWithAt());
+    }
+
     // Only allow ObjC-rooted classes to be @objc.
     // (Leave a hole for test cases.)
     if (ancestry.contains(AncestryFlags::ObjC) &&
@@ -1032,8 +1061,16 @@ static Optional<ObjCReason> shouldMarkClassAsObjC(const ClassDecl *CD) {
     return ObjCReason(ObjCReason::ExplicitlyObjC);
   }
 
-  if (ancestry.contains(AncestryFlags::ObjC) &&
-      !ancestry.contains(AncestryFlags::Generic)) {
+  if (ancestry.contains(AncestryFlags::ObjC)) {
+    if (ancestry.contains(AncestryFlags::Generic)) {
+      return None;
+    }
+
+    if (ancestry.contains(AncestryFlags::ResilientOther) &&
+        !ctx.LangOpts.EnableObjCResilientClassStubs) {
+      return None;
+    }
+
     return ObjCReason(ObjCReason::ImplicitlyObjC);
   }
 

test/attr/attr_objc.swift

@@ -193,9 +193,9 @@ extension subject_genericClass where T : Hashable {
 }
 
 extension subject_genericClass {
-  @objc var extProp: Int { return 0 } // expected-error{{members of extensions of generic classes cannot be declared @objc}}
+  @objc var extProp: Int { return 0 } // expected-error{{extensions of generic classes cannot contain '@objc' members}}
 
-  @objc func extFoo() {} // expected-error{{members of extensions of generic classes cannot be declared @objc}}
+  @objc func extFoo() {} // expected-error{{extensions of generic classes cannot contain '@objc' members}}
 }
 
 @objc

test/attr/attr_objc_resilience.swift

@@ -0,0 +1,44 @@
+// RUN: %empty-directory(%t)
+// RUN: %target-swift-frontend -emit-module-path %t/resilient_struct.swiftmodule %S/../Inputs/resilient_struct.swift -enable-library-evolution
+// RUN: %target-swift-frontend(mock-sdk: %clang-importer-sdk) -emit-module-path %t/resilient_objc_class.swiftmodule %S/../Inputs/resilient_objc_class.swift -I %t -enable-library-evolution
+// RUN: %target-swift-frontend -typecheck -verify %s -I %t
+
+// REQUIRES: objc_interop
+
+import Foundation
+import resilient_objc_class
+
+@objc public class ResilientNSObjectSubclass : ResilientNSObjectOutsideParent {}
+// expected-error@-1 {{classes built with library evolution support cannot have explicit '@objc' subclasses because they are not directly visible from Objective-C}}
+
+public class AnotherResilientNSObjectSubclass : ResilientNSObjectOutsideParent {}
+
+extension ResilientNSObjectOutsideParent {
+  @objc public func categoryOneMethod() {}
+  // expected-error@-1 {{extensions of classes built with library evolution support cannot contain '@objc' members}}
+}
+
+extension AnotherResilientNSObjectSubclass {
+  @objc public func categoryTwoMethod() {}
+  // expected-error@-1 {{extensions of classes built with library evolution support cannot contain '@objc' members}}
+}
+
+// Note: @_fixed_layout on a class only applies to the storage layout and
+// not metadata, which remains resilient.
+
+@_fixed_layout
+@objc public class FixedLayoutNSObjectSubclass : FixedLayoutNSObjectOutsideParent {}
+// expected-error@-1 {{classes built with library evolution support cannot have explicit '@objc' subclasses because they are not directly visible from Objective-C}}
+
+@_fixed_layout
+public class AnotherFixedLayoutNSObjectSubclass : FixedLayoutNSObjectOutsideParent {}
+
+extension FixedLayoutNSObjectOutsideParent {
+  @objc public func categoryOneMethod() {}
+  // expected-error@-1 {{extensions of classes built with library evolution support cannot contain '@objc' members}}
+}
+
+extension AnotherFixedLayoutNSObjectSubclass {
+  @objc public func categoryTwoMethod() {}
+  // expected-error@-1 {{extensions of classes built with library evolution support cannot contain '@objc' members}}
+}

test/attr/attr_objc_resilient_stubs.swift

@@ -0,0 +1,41 @@
+// RUN: %empty-directory(%t)
+// RUN: %target-swift-frontend -emit-module-path %t/resilient_struct.swiftmodule %S/../Inputs/resilient_struct.swift -enable-library-evolution
+// RUN: %target-swift-frontend(mock-sdk: %clang-importer-sdk) -emit-module-path %t/resilient_objc_class.swiftmodule %S/../Inputs/resilient_objc_class.swift -I %t -enable-library-evolution -enable-resilient-objc-class-stubs
+// RUN: %target-swift-frontend -typecheck -verify %s -I %t -enable-resilient-objc-class-stubs
+
+// REQUIRES: objc_interop
+
+import Foundation
+import resilient_objc_class
+
+// When built with -enable-resilient-objc-class-stubs, all of these cases are
+// allowed.
+
+@objc public class ResilientNSObjectSubclass : ResilientNSObjectOutsideParent {}
+
+public class AnotherResilientNSObjectSubclass : ResilientNSObjectOutsideParent {}
+
+extension ResilientNSObjectOutsideParent {
+  @objc public func categoryOneMethod() {}
+}
+
+extension AnotherResilientNSObjectSubclass {
+  @objc public func categoryTwoMethod() {}
+}
+
+// Note: @_fixed_layout on a class only applies to the storage layout and
+// not metadata, which remains resilient.
+
+@_fixed_layout
+@objc public class FixedLayoutNSObjectSubclass : FixedLayoutNSObjectOutsideParent {}
+
+@_fixed_layout
+public class AnotherFixedLayoutNSObjectSubclass : FixedLayoutNSObjectOutsideParent {}
+
+extension FixedLayoutNSObjectOutsideParent {
+  @objc public func categoryOneMethod() {}
+}
+
+extension AnotherFixedLayoutNSObjectSubclass {
+  @objc public func categoryTwoMethod() {}
+}

test/decl/ext/extension-generic-objc.swift

@@ -15,7 +15,7 @@ class A<T> : NSObject {
 }
 extension A {
     // This should throw an error
-    @objc func a1() {} // expected-error{{members of extensions of generic classes cannot be declared @objc}}
+    @objc func a1() {} // expected-error{{extensions of generic classes cannot contain '@objc' members}}
     // This should *not* throw an error
     func a2() {}
 }
@@ -51,6 +51,6 @@ class Outer<T> {
 
 extension Outer.Inner {
     @objc func outerInner1() {}
-    // expected-error@-1{{members of extensions of classes from generic context cannot be declared @objc}}
+    // expected-error@-1{{extensions of classes from generic context cannot contain '@objc' members}}
     func outerInner2() {}
 }