Pacify gcc's -Wreturn-type

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@150731 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/AST/ExprCXX.cpp b/lib/AST/ExprCXX.cpp
index 718010b..f52f881 100644
--- a/lib/AST/ExprCXX.cpp
+++ b/lib/AST/ExprCXX.cpp
@@ -120,6 +120,7 @@
   case ListInit:
     return getInitializer()->getSourceRange().getEnd();
   }
+  llvm_unreachable("bogus initialization style");
 }
 
 // CXXDeleteExpr