Improve diagnostics when property being looked up

in a forward @class object. // rdar://8774513

llvm-svn: 121933

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -2416,6 +2416,10 @@ def err_ref_array_type : Error<
   "cannot refer to declaration with an array type inside block">;
 def err_property_not_found : Error<
   "property %0 not found on object of type %1">;
+def err_property_not_found_forward_class : Error<
+  "property %0 cannot be found in forward class object %1">;
+def note_forward_class : Note<
+  "forward class is declared here">;
 def err_duplicate_property : Error<
   "property has a previous declaration">;
 def ext_gnu_void_ptr : Extension<

clang/lib/Sema/SemaExprObjC.cpp

@@ -353,6 +353,12 @@ HandleExprPropertyRefExpr(const ObjCObjectPointerType *OPT,
   ObjCInterfaceDecl *IFace = IFaceT->getDecl();
   IdentifierInfo *Member = MemberName.getAsIdentifierInfo();
 
+  if (IFace->isForwardDecl()) {
+    Diag(MemberLoc, diag::err_property_not_found_forward_class)
+         << MemberName << QualType(OPT, 0);
+    Diag(IFace->getLocation(), diag::note_forward_class);
+    return ExprError();
+  }
   // Search for a declared property first.
   if (ObjCPropertyDecl *PD = IFace->FindPropertyDeclaration(Member)) {
     // Check whether we can reference this property.

clang/test/SemaObjC/property-9.m

@@ -96,3 +96,14 @@ typedef signed char BOOL;
 - (float)setMyStyle:(int)style;
 @end
 
+// rdar://8774513
+@class MDAInstance; // expected-note {{forward class is declared here}}
+
+@interface MDATestDocument
+@property(retain) MDAInstance *instance;
+@end
+
+id f0(MDATestDocument *d) {
+  return d.instance.path; // expected-error {{property 'path' cannot be found in forward class object 'MDAInstance *'}}
+}
+