5 files changed, 95 insertions, 2 deletions
diff --git a/llvm/include/llvm/ADT/Optional.h b/llvm/include/llvm/ADT/Optional.h
index 76937d632ae..56eafb156e8 100644
--- a/llvm/include/llvm/ADT/Optional.h
+++ b/llvm/include/llvm/ADT/Optional.h
@@ -27,6 +27,8 @@
 
 namespace llvm {
 
+class raw_ostream;
+
 namespace optional_detail {
 /// Storage for any type.
 template <typename T, bool = isPodLike<T>::value> struct OptionalStorage {
@@ -323,6 +325,18 @@ template <typename T> bool operator>=(const T &X, const Optional<T> &Y) {
   return !(X < Y);
 }
 
+raw_ostream &operator<<(raw_ostream &OS, NoneType);
+
+template <typename T, typename = decltype(std::declval<raw_ostream &>()
+                                          << std::declval<const T &>())>
+raw_ostream &operator<<(raw_ostream &OS, const Optional<T> &O) {
+  if (O)
+    OS << *O;
+  else
+    OS << None;
+  return OS;
+}
+
 } // end namespace llvm
 
 #endif // LLVM_ADT_OPTIONAL_H
diff --git a/llvm/lib/Support/CMakeLists.txt b/llvm/lib/Support/CMakeLists.txt
index 2a6810672b1..7e791594587 100644
--- a/llvm/lib/Support/CMakeLists.txt
+++ b/llvm/lib/Support/CMakeLists.txt
@@ -106,6 +106,7 @@ add_llvm_library(LLVMSupport
   MemoryBuffer.cpp
   MD5.cpp
   NativeFormatting.cpp
+  Optional.cpp
   Options.cpp
   Parallel.cpp
   PluginLoader.cpp
diff --git a/llvm/lib/Support/Optional.cpp b/llvm/lib/Support/Optional.cpp
new file mode 100644
index 00000000000..765b25df13d
--- /dev/null
+++ b/llvm/lib/Support/Optional.cpp
@@ -0,0 +1,15 @@
+//===- Optional.cpp - Optional values ---------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ADT/Optional.h"
+#include "llvm/Support/raw_ostream.h"
+
+llvm::raw_ostream &llvm::operator<<(raw_ostream &OS, NoneType) {
+  return OS << "None";
+}
diff --git a/llvm/unittests/ADT/OptionalTest.cpp b/llvm/unittests/ADT/OptionalTest.cpp
index 20bc9da4d59..e6997ef8be7 100644
--- a/llvm/unittests/ADT/OptionalTest.cpp
+++ b/llvm/unittests/ADT/OptionalTest.cpp
@@ -8,6 +8,9 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/ADT/Optional.h"
+#include "llvm/ADT/SmallString.h"
+#include "llvm/Support/raw_ostream.h"
+#include "gtest/gtest-spi.h"
 #include "gtest/gtest.h"
 
 using namespace llvm;
@@ -518,5 +521,52 @@ TEST_F(OptionalTest, OperatorGreaterEqual) {
   CheckRelation<GreaterEqual>(InequalityLhs, InequalityRhs, !IsLess);
 }
 
-} // end anonymous namespace
+struct ComparableAndStreamable {
+  friend bool operator==(ComparableAndStreamable,
+                         ComparableAndStreamable) LLVM_ATTRIBUTE_USED {
+    return true;
+  }
+
+  friend raw_ostream &operator<<(raw_ostream &OS, ComparableAndStreamable) {
+    return OS << "ComparableAndStreamable";
+  }
 
+  static Optional<ComparableAndStreamable> get() {
+    return ComparableAndStreamable();
+  }
+};
+
+TEST_F(OptionalTest, StreamOperator) {
+  auto to_string = [](Optional<ComparableAndStreamable> O) {
+    SmallString<16> S;
+    raw_svector_ostream OS(S);
+    OS << O;
+    return S;
+  };
+  EXPECT_EQ("ComparableAndStreamable",
+            to_string(ComparableAndStreamable::get()));
+  EXPECT_EQ("None", to_string(None));
+}
+
+struct Comparable {
+  friend bool operator==(Comparable, Comparable) LLVM_ATTRIBUTE_USED {
+    return true;
+  }
+  static Optional<Comparable> get() { return Comparable(); }
+};
+
+TEST_F(OptionalTest, UseInUnitTests) {
+  // Test that we invoke the streaming operators when pretty-printing values in
+  // EXPECT macros.
+  EXPECT_NONFATAL_FAILURE(EXPECT_EQ(llvm::None, ComparableAndStreamable::get()),
+                          R"(Expected: llvm::None
+      Which is: None
+To be equal to: ComparableAndStreamable::get()
+      Which is: ComparableAndStreamable)");
+
+  // Test that it is still possible to compare objects which do not have a
+  // custom streaming operator.
+  EXPECT_NONFATAL_FAILURE(EXPECT_EQ(llvm::None, Comparable::get()), "object");
+}
+
+} // end anonymous namespace
diff --git a/llvm/utils/unittest/googletest/include/gtest/internal/custom/raw-ostream.h b/llvm/utils/unittest/googletest/include/gtest/internal/custom/raw-ostream.h
index fd993db1602..f4430f8de47 100644
--- a/llvm/utils/unittest/googletest/include/gtest/internal/custom/raw-ostream.h
+++ b/llvm/utils/unittest/googletest/include/gtest/internal/custom/raw-ostream.h
@@ -42,8 +42,9 @@ auto printable(const T &V) -> decltype(StreamSwitch<T>::printable(V)) {
 // If raw_ostream support is enabled, we specialize for types with operator<<
 // that takes a raw_ostream.
 #if !GTEST_NO_LLVM_RAW_OSTREAM
-#include "llvm/Support/raw_ostream.h"
+#include "llvm/ADT/Optional.h"
 #include "llvm/Support/raw_os_ostream.h"
+#include "llvm/Support/raw_ostream.h"
 #include <ostream>
 namespace llvm_gtest {
 
@@ -68,6 +69,18 @@ struct StreamSwitch<T, decltype((void)(std::declval<llvm::raw_ostream &>()
                                        << ConvertibleTo<const T &>()))> {
   static const RawStreamProxy<T> printable(const T &V) { return {V}; }
 };
+
+// llvm::Optional has a template operator<<, which means it will not accept any
+// implicit conversions, so we need to special-case it here.
+template <typename T>
+struct StreamSwitch<llvm::Optional<T>,
+                    decltype((void)(std::declval<llvm::raw_ostream &>()
+                                    << std::declval<llvm::Optional<T>>()))> {
+  static const RawStreamProxy<llvm::Optional<T>>
+  printable(const llvm::Optional<T> &V) {
+    return {V};
+  }
+};
 } // namespace llvm_gtest
 #endif  // !GTEST_NO_LLVM_RAW_OSTREAM