From 1a3cb157e1a1fc24fc64d782b5c54b03f5c6313f Mon Sep 17 00:00:00 2001
From: Douglas Gregor <dgregor@apple.com>
Date: Fri, 18 Dec 2015 00:52:31 +0000
Subject: [PATCH] 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.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@255943 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Sema/SemaObjCProperty.cpp           |  7 +++++++
 test/SemaObjC/arc-property-decl-attrs.m | 16 ++++++++++++++++
 2 files changed, 23 insertions(+)

diff --git a/lib/Sema/SemaObjCProperty.cpp b/lib/Sema/SemaObjCProperty.cpp
index f42daced86..1cb84e4480 100644
--- a/lib/Sema/SemaObjCProperty.cpp
+++ b/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;
 }
 
diff --git a/test/SemaObjC/arc-property-decl-attrs.m b/test/SemaObjC/arc-property-decl-attrs.m
index 408b270920..6c96ba481c 100644
--- a/test/SemaObjC/arc-property-decl-attrs.m
+++ b/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
-- 
2.40.0