Fix typo in comment

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@94576 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Lex/PPMacroExpansion.cpp b/lib/Lex/PPMacroExpansion.cpp
index 13aeb88..d0480b8 100644
--- a/lib/Lex/PPMacroExpansion.cpp
+++ b/lib/Lex/PPMacroExpansion.cpp
@@ -152,7 +152,7 @@
                                                  MacroInfo *MI) {
   if (Callbacks) Callbacks->MacroExpands(Identifier, MI);
 
-  // If this is a macro exapnsion in the "#if !defined(x)" line for the file,
+  // If this is a macro expansion in the "#if !defined(x)" line for the file,
   // then the macro could expand to different things in other contexts, we need
   // to disable the optimization in this case.
   if (CurPPLexer) CurPPLexer->MIOpt.ExpandedMacro();