3 files changed, 34 insertions, 2 deletions
diff --git a/llvm/include/llvm/ADT/STLExtras.h b/llvm/include/llvm/ADT/STLExtras.h
index f69a15bdc25..16f850c0f57 100644
--- a/llvm/include/llvm/ADT/STLExtras.h
+++ b/llvm/include/llvm/ADT/STLExtras.h
@@ -77,8 +77,11 @@ class function_ref<Ret(Params...)> {
   }
 
 public:
-  template<typename Callable>
-  function_ref(Callable &&callable)
+  template <typename Callable>
+  function_ref(Callable &&callable,
+               typename std::enable_if<
+                   !std::is_same<typename std::remove_reference<Callable>::type,
+                                 function_ref>::value>::type * = nullptr)
       : callback(callback_fn<typename std::remove_reference<Callable>::type>),
         callable(reinterpret_cast<intptr_t>(&callable)) {}
   Ret operator()(Params ...params) const {
diff --git a/llvm/unittests/ADT/CMakeLists.txt b/llvm/unittests/ADT/CMakeLists.txt
index 0f214f3d0c8..845e8058200 100644
--- a/llvm/unittests/ADT/CMakeLists.txt
+++ b/llvm/unittests/ADT/CMakeLists.txt
@@ -13,6 +13,7 @@ set(ADTSources
   DenseMapTest.cpp
   DenseSetTest.cpp
   FoldingSet.cpp
+  FunctionRefTest.cpp
   HashingTest.cpp
   ilistTest.cpp
   ImmutableMapTest.cpp
diff --git a/llvm/unittests/ADT/FunctionRefTest.cpp b/llvm/unittests/ADT/FunctionRefTest.cpp
new file mode 100644
index 00000000000..075d9a070df
--- /dev/null
+++ b/llvm/unittests/ADT/FunctionRefTest.cpp
@@ -0,0 +1,28 @@
+//===- llvm/unittest/ADT/MakeUniqueTest.cpp - make_unique unit tests ------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ADT/STLExtras.h"
+#include "gtest/gtest.h"
+
+using namespace llvm;
+
+namespace {
+
+// Ensure that copies of a function_ref copy the underlying state rather than
+// causing one function_ref to chain to the next.
+TEST(FunctionRefTest, Copy) {
+  auto A = [] { return 1; };
+  auto B = [] { return 2; };
+  function_ref<int()> X = A;
+  function_ref<int()> Y = X;
+  X = B;
+  EXPECT_EQ(1, Y());
+}
+
+}