ObjC properties: consider ownership of properties from protocols when synthesizing.

When determining whether ownership was explicitly written for a
property when it is being synthesized, also consider that the original
property might have come from a protocol. Fixes rdar://problem/23931441.

llvm-svn: 255943

clang/lib/Sema/SemaObjCProperty.cpp

@@ -868,6 +868,13 @@ static bool hasWrittenStorageAttribute(ObjCPropertyDecl *Prop) {
       return OrigProp->getPropertyAttributesAsWritten() & OwnershipMask;
   }
 
+  // Look through all of the protocols.
+  for (const auto *Proto : OrigClass->all_referenced_protocols()) {
+    if (ObjCPropertyDecl *OrigProp =
+          Proto->FindPropertyDeclaration(Prop->getIdentifier()))
+      return OrigProp->getPropertyAttributesAsWritten() & OwnershipMask;
+  }
+
   return false;
 }
 

clang/test/SemaObjC/arc-property-decl-attrs.m

@@ -105,3 +105,19 @@
 @property(nonatomic, weak, nonnull, readonly) id ROdelegate; // expected-error {{property attributes 'nonnull' and 'weak' are mutually exclusive}}
 @end
 
+// rdar://problem/23931441
+@protocol P
+@property(readonly, retain) id prop;
+@end
+
+__attribute__((objc_root_class))
+@interface I2<P>
+@end
+
+@interface I2()
+@property (readwrite) id prop;
+@end
+
+@implementation I2
+@synthesize prop;
+@end