1 files changed, 9 insertions, 0 deletions
diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index 163973bd55f..c2c886c04ea 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -6756,6 +6756,15 @@ Sema::CheckSingleAssignmentConstraints(QualType LHSType, ExprResult &RHS,
       return Incompatible;
   }
 
+  Expr *PRE = RHS.get()->IgnoreParenCasts();
+  if (ObjCProtocolExpr *OPE = dyn_cast<ObjCProtocolExpr>(PRE)) {
+    ObjCProtocolDecl *PDecl = OPE->getProtocol();
+    if (PDecl && !PDecl->hasDefinition()) {
+      Diag(PRE->getExprLoc(), diag::warn_atprotocol_protocol) << PDecl->getName();
+      Diag(PDecl->getLocation(), diag::note_entity_declared_at) << PDecl;
+    }
+  }
+  
   CastKind Kind = CK_Invalid;
   Sema::AssignConvertType result =
     CheckAssignmentConstraints(LHSType, RHS, Kind);