-Warc-repeated-use-of-weak: Check messages to property accessors as well.

Previously, [foo weakProp] was not being treated the same as foo.weakProp.
Now, for every explicit message send, we check if it's a property access,
and if so, if the property is weak. Then for every assignment of a
message, we have to do the same thing again.

This is a potentially expensive increase because determining whether a
method is a property accessor requires searching through the methods it
overrides. However, without it -Warc-repeated-use-of-weak will miss cases
from people who prefer not to use dot syntax. If this turns out to be
too expensive, we can try caching the result somewhere, or even lose
precision by not checking superclass methods. The warning is off-by-default,
though.

<rdar://problem/12407765>

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@165718 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 18 insertions, 0 deletions

diff --git a/lib/Sema/SemaExprObjC.cpp b/lib/Sema/SemaExprObjC.cpp
index 1bb4df0483..3f9c14c685 100644
--- a/lib/Sema/SemaExprObjC.cpp
+++ b/lib/Sema/SemaExprObjC.cpp
@@ -2434,6 +2434,24 @@ ExprResult Sema::BuildInstanceMessage(Expr *Receiver,
     // In ARC, check for message sends which are likely to introduce
     // retain cycles.
     checkRetainCycles(Result);
+
+    if (!isImplicit && Method) {
+      if (const ObjCPropertyDecl *Prop = Method->findPropertyDecl()) {
+        bool IsWeak =
+          Prop->getPropertyAttributes() & ObjCPropertyDecl::OBJC_PR_weak;
+        if (!IsWeak && Sel.isUnarySelector())
+          IsWeak = ReturnType.getObjCLifetime() & Qualifiers::OCL_Weak;
+
+        if (IsWeak) {
+          DiagnosticsEngine::Level Level =
+            Diags.getDiagnosticLevel(diag::warn_arc_repeated_use_of_weak,
+                                     LBracLoc);
+          if (Level != DiagnosticsEngine::Ignored)
+            getCurFunction()->recordUseOfWeak(Result, Prop);
+
+        }
+      }
+    }
   }
       
   return MaybeBindToTemporary(Result);