diff --git a/clang/lib/Sema/SemaTemplateVariadic.cpp b/clang/lib/Sema/SemaTemplateVariadic.cpp
index 473dcb7d..dc5013c 100644
--- a/clang/lib/Sema/SemaTemplateVariadic.cpp
+++ b/clang/lib/Sema/SemaTemplateVariadic.cpp
@@ -456,6 +456,10 @@
   std::pair<IdentifierInfo *, SourceLocation> FirstPack;
   bool HaveFirstPack = false;
   
+  // FIXME: Variadic templates. Even if we don't expand, we'd still like to
+  // return the number of expansions back to the caller, perhaps as an 
+  // llvm::Optional, so that it can be embedded in the pack expansion. This
+  // is important for the multi-level substitution case.
   for (unsigned I = 0; I != NumUnexpanded; ++I) {
     // Compute the depth and index for this parameter pack.
     unsigned Depth;