1 files changed, 55 insertions, 0 deletions
diff --git a/lib/Sema/SemaAccess.cpp b/lib/Sema/SemaAccess.cpp
index 4625cb15ea..e629f0fd35 100644
--- a/lib/Sema/SemaAccess.cpp
+++ b/lib/Sema/SemaAccess.cpp
@@ -930,6 +930,57 @@ static CXXBasePath *FindBestPath(Sema &S,
   return BestPath;
 }
 
+/// Given that an entity has protected natural access, check whether
+/// access might be denied because of the protected member access
+/// restriction.
+///
+/// \return true if a note was emitted
+static bool TryDiagnoseProtectedAccess(Sema &S, const EffectiveContext &EC,
+                                       AccessTarget &Target) {
+  // Only applies to instance accesses.
+  if (!Target.hasInstanceContext())
+    return false;
+  assert(Target.isMemberAccess());
+  NamedDecl *D = Target.getTargetDecl();
+
+  const CXXRecordDecl *DeclaringClass = Target.getDeclaringClass();
+  DeclaringClass = DeclaringClass->getCanonicalDecl();
+
+  for (EffectiveContext::record_iterator
+         I = EC.Records.begin(), E = EC.Records.end(); I != E; ++I) {
+    const CXXRecordDecl *ECRecord = *I;
+    switch (IsDerivedFromInclusive(ECRecord, DeclaringClass)) {
+    case AR_accessible: break;
+    case AR_inaccessible: continue;
+    case AR_dependent: continue;
+    }
+
+    // The effective context is a subclass of the declaring class.
+    // If that class isn't a superclass of the instance context,
+    // then the [class.protected] restriction applies.
+
+    // To get this exactly right, this might need to be checked more
+    // holistically;  it's not necessarily the case that gaining
+    // access here would grant us access overall.
+
+    const CXXRecordDecl *InstanceContext = Target.resolveInstanceContext(S);
+    assert(InstanceContext && "diagnosing dependent access");
+
+    switch (IsDerivedFromInclusive(InstanceContext, ECRecord)) {
+    case AR_accessible: continue;
+    case AR_dependent: continue;
+    case AR_inaccessible:
+      S.Diag(D->getLocation(), diag::note_access_protected_restricted)
+        << (InstanceContext != Target.getNamingClass()->getCanonicalDecl())
+        << S.Context.getTypeDeclType(InstanceContext)
+        << S.Context.getTypeDeclType(ECRecord);
+      return true;
+    }
+  }
+
+  return false;
+}
+
 /// Diagnose the path which caused the given declaration or base class
 /// to become inaccessible.
 static void DiagnoseAccessPath(Sema &S,
@@ -948,6 +999,10 @@ static void DiagnoseAccessPath(Sema &S,
   if (D && (Access == D->getAccess() || D->getAccess() == AS_private)) {
     switch (HasAccess(S, EC, DeclaringClass, D->getAccess(), Entity)) {
     case AR_inaccessible: {
+      if (Access == AS_protected &&
+          TryDiagnoseProtectedAccess(S, EC, Entity))
+        return;
+
       S.Diag(D->getLocation(), diag::note_access_natural)
         << (unsigned) (Access == AS_protected)
         << /*FIXME: not implicitly*/ 0;