[Objective-C] Add objc_subclassing_restricted attribute
This patch adds an objc_subclassing_restricted attribute into clang. This
attribute acts similarly to 'final' - Objective-C classes with this attribute
can't be subclassed. However, @interface declarations that have
objc_subclassing_restricted but don't have @implementation are allowed to
inherit other @interface declarations with objc_subclassing_restricted. This is
needed to describe the Swift class hierarchy in clang while making sure that
the Objective-C classes cannot subclass the Swift classes.
This attribute is already implemented in a fork of clang that's used for Swift
(https://github.com/apple/swift-clang) and this patch moves that code to the
upstream clang repository.
rdar://28937548
Differential Revision: https://reviews.llvm.org/D25993
llvm-svn: 285391
diff --git a/clang/test/SemaObjC/subclassing-restricted-attr.m b/clang/test/SemaObjC/subclassing-restricted-attr.m
new file mode 100644
index 0000000..d0db5e45
--- /dev/null
+++ b/clang/test/SemaObjC/subclassing-restricted-attr.m
@@ -0,0 +1,36 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -Wno-objc-root-class %s
+// RUN: %clang_cc1 -x objective-c++ -fsyntax-only -verify -Wno-objc-root-class %s
+// rdar://16560476
+
+__attribute__((objc_subclassing_restricted))
+@interface Leaf // okay
+@end
+
+__attribute__((objc_subclassing_restricted))
+@interface SubClassOfLeaf : Leaf // expected-note {{class is declared here}}
+@end
+
+
+@interface SubClass : SubClassOfLeaf // expected-error {{cannot subclass a class that was declared with the 'objc_subclassing_restricted' attribute}}
+@end
+
+__attribute__((objc_root_class))
+@interface PlainRoot
+@end
+
+__attribute__((objc_subclassing_restricted))
+@interface Sub2Class : PlainRoot // okay
+@end
+
+// rdar://28753587
+__attribute__((objc_subclassing_restricted))
+@interface SuperImplClass // expected-note {{class is declared here}}
+@end
+@implementation SuperImplClass
+@end
+
+__attribute__((objc_subclassing_restricted))
+@interface SubImplClass : SuperImplClass
+@end
+@implementation SubImplClass // expected-error {{cannot subclass a class that was declared with the 'objc_subclassing_restricted' attribute}}
+@end