More dead code removal (using -Wunreachable-code)

llvm-svn: 148577
diff --git a/clang/lib/AST/DeclBase.cpp b/clang/lib/AST/DeclBase.cpp
index 3763ebd..da54a44 100644
--- a/clang/lib/AST/DeclBase.cpp
+++ b/clang/lib/AST/DeclBase.cpp
@@ -529,7 +529,7 @@
       return 0;
   }
 
-  return 0;
+  llvm_unreachable("Invalid DeclKind!");
 }
 
 void Decl::setAttrs(const AttrVec &attrs) {