Merging r244462:
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r244462 | joerg | 2015-08-10 09:58:04 -0700 (Mon, 10 Aug 2015) | 2 lines

Protect template argument from user interference.

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git-svn-id: https://llvm.org/svn/llvm-project/libcxx/branches/release_37@244553 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/type_traits b/include/type_traits
index 3c773ba..a0c1bc5 100644
--- a/include/type_traits
+++ b/include/type_traits
@@ -219,8 +219,8 @@
 template <class>
 struct __void_t { typedef void type; };
 
-template <class T>
-struct __identity { typedef T type; };
+template <class _Tp>
+struct __identity { typedef _Tp type; };
 
 template <class _Tp, bool>
 struct _LIBCPP_TYPE_VIS_ONLY __dependent_type : public _Tp {};