[PCH] Fix bug where we failed to update an identifier for a single token
macro expansion.

rdar://10588825

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@146818 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Lex/PPMacroExpansion.cpp b/lib/Lex/PPMacroExpansion.cpp
index 20ebb40..5cd6565 100644
--- a/lib/Lex/PPMacroExpansion.cpp
+++ b/lib/Lex/PPMacroExpansion.cpp
@@ -116,6 +116,11 @@
   // If the token isn't an identifier, it's always literally expanded.
   if (II == 0) return true;
 
+  // If the information about this identifier is out of date, update it from
+  // the external source.
+  if (II->isOutOfDate())
+    PP.getExternalSource()->updateOutOfDateIdentifier(*II);
+
   // If the identifier is a macro, and if that macro is enabled, it may be
   // expanded so it's not a trivial expansion.
   if (II->hasMacroDefinition() && PP.getMacroInfo(II)->isEnabled() &&