Tie DefineVTablesUsed() in with recursive function instantiation so that we emit
a useful template instantiation stack. Fixes PR8640.

This also causes a slight change to where the "instantianted from" note shows up
in truly esoteric cases (see the change to test/SemaCXX/destructor.cpp), but
that isn't directly the fault of this patch.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@120135 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Sema/SemaTemplateInstantiateDecl.cpp b/lib/Sema/SemaTemplateInstantiateDecl.cpp
index fc298c1..9899a85 100644
--- a/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ b/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -2108,9 +2108,12 @@
   // If we're performing recursive template instantiation, create our own
   // queue of pending implicit instantiations that we will instantiate later,
   // while we're still within our own instantiation context.
+  llvm::SmallVector<VTableUse, 16> SavedVTableUses;
   std::deque<PendingImplicitInstantiation> SavedPendingInstantiations;
-  if (Recursive)
+  if (Recursive) {
+    VTableUses.swap(SavedVTableUses);
     PendingInstantiations.swap(SavedPendingInstantiations);
+  }
 
   EnterExpressionEvaluationContext EvalContext(*this, 
                                                Sema::PotentiallyEvaluated);
@@ -2173,10 +2176,16 @@
   Scope.Exit();
 
   if (Recursive) {
+    // Define any pending vtables.
+    DefineUsedVTables();
+
     // Instantiate any pending implicit instantiations found during the
     // instantiation of this template.
     PerformPendingInstantiations();
 
+    // Restore the set of pending vtables.
+    VTableUses.swap(SavedVTableUses);
+
     // Restore the set of pending implicit instantiations.
     PendingInstantiations.swap(SavedPendingInstantiations);
   }