1 files changed, 17 insertions, 0 deletions
diff --git a/runtime/base/stl_util.h b/runtime/base/stl_util.h
index 324ab218d2..ad03c319d9 100644
--- a/runtime/base/stl_util.h
+++ b/runtime/base/stl_util.h
@@ -156,6 +156,23 @@ struct CStringLess {
   }
 };
 
+// Use to suppress type deduction for a function argument.
+// See std::identity<> for more background:
+// http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2005/n1856.html#20.2.2 - move/forward helpers
+//
+// e.g. "template <typename X> void bar(identity<X>::type foo);
+//     bar(5); // compilation error
+//     bar<int>(5); // ok
+// or "template <typename T> void foo(T* x, typename Identity<T*>::type y);
+//     Base b;
+//     Derived d;
+//     foo(&b, &d);  // Use implicit Derived* -> Base* conversion.
+// If T was deduced from both &b and &d, there would be a mismatch, i.e. deduction failure.
+template <typename T>
+struct Identity {
+  using type = T;
+};
+
 }  // namespace art
 
 #endif  // ART_RUNTIME_BASE_STL_UTIL_H_