[ObjC] The absence of ownership qualifiers on an ambiguous property leads

to synthesis of a valid property even when the selected protocol property
has ownership qualifiers

rdar://39024725

llvm-svn: 331409

2 files changed, 49 insertions, 4 deletions

diff --git a/clang/lib/Sema/SemaObjCProperty.cpp b/clang/lib/Sema/SemaObjCProperty.cpp
index 3b8ad3d7e11..7ff037018fa 100644
--- a/clang/lib/Sema/SemaObjCProperty.cpp
+++ b/clang/lib/Sema/SemaObjCProperty.cpp
@@ -897,14 +897,24 @@ SelectPropertyForSynthesisFromProtocols(Sema &S, SourceLocation AtLoc,
                                                  : HasUnexpectedAttribute;
         Mismatches.push_back({Prop, Kind, AttributeName});
       };
-      if (isIncompatiblePropertyAttribute(OriginalAttributes, Attr,
+      // The ownership might be incompatible unless the property has no explicit
+      // ownership.
+      bool HasOwnership = (Attr & (ObjCPropertyDecl::OBJC_PR_retain |
+                                   ObjCPropertyDecl::OBJC_PR_strong |
+                                   ObjCPropertyDecl::OBJC_PR_copy |
+                                   ObjCPropertyDecl::OBJC_PR_assign |
+                                   ObjCPropertyDecl::OBJC_PR_unsafe_unretained |
+                                   ObjCPropertyDecl::OBJC_PR_weak)) != 0;
+      if (HasOwnership &&
+          isIncompatiblePropertyAttribute(OriginalAttributes, Attr,
                                           ObjCPropertyDecl::OBJC_PR_copy)) {
         Diag(OriginalAttributes & ObjCPropertyDecl::OBJC_PR_copy, "copy");
         continue;
       }
-      if (areIncompatiblePropertyAttributes(
-              OriginalAttributes, Attr, ObjCPropertyDecl::OBJC_PR_retain |
-                                            ObjCPropertyDecl::OBJC_PR_strong)) {
+      if (HasOwnership && areIncompatiblePropertyAttributes(
+                              OriginalAttributes, Attr,
+                              ObjCPropertyDecl::OBJC_PR_retain |
+                                  ObjCPropertyDecl::OBJC_PR_strong)) {
         Diag(OriginalAttributes & (ObjCPropertyDecl::OBJC_PR_retain |
                                    ObjCPropertyDecl::OBJC_PR_strong),
              "retain (or strong)");
diff --git a/clang/test/SemaObjC/arc-property-decl-attrs.m b/clang/test/SemaObjC/arc-property-decl-attrs.m
index 7393f58199f..6638054bef8 100644
--- a/clang/test/SemaObjC/arc-property-decl-attrs.m
+++ b/clang/test/SemaObjC/arc-property-decl-attrs.m
@@ -252,3 +252,38 @@ __attribute__((objc_root_class))
 @synthesize prop = _prop;
 
 @end
+
+// rdar://39024725
+// Allow strong readwrite property and a readonly one.
+@protocol StrongCollision
+
+@property(strong) NSObject *p;
+@property(copy) NSObject *p2;
+
+// expected-error@+1 {{property with attribute 'retain (or strong)' was selected for synthesis}}
+@property(strong, readwrite) NSObject *collision;
+
+@end
+
+@protocol ReadonlyCollision
+
+@property(readonly) NSObject *p;
+@property(readonly) NSObject *p2;
+
+// expected-note@+1 {{it could also be property without attribute 'retain (or strong)' declared here}}
+@property(readonly, weak) NSObject *collision;
+
+@end
+
+@interface StrongReadonlyCollision : NSObject <StrongCollision, ReadonlyCollision>
+@end
+
+@implementation StrongReadonlyCollision
+
+// no error
+@synthesize p = _p;
+@synthesize p2 = _p2;
+
+@synthesize collision = _collision; // expected-note {{property synthesized here}}
+
+@end