1 files changed, 45 insertions, 0 deletions
diff --git a/llvm/unittests/ADT/STLExtrasTest.cpp b/llvm/unittests/ADT/STLExtrasTest.cpp
index db344bc6089..8675f6d5ce1 100644
--- a/llvm/unittests/ADT/STLExtrasTest.cpp
+++ b/llvm/unittests/ADT/STLExtrasTest.cpp
@@ -192,4 +192,49 @@ TEST(STLExtrasTest, EnumerateLifetimeSemantics) {
   EXPECT_EQ(0, Moves);
   EXPECT_EQ(0, Destructors);
 }
+
+TEST(STLExtrasTest, ApplyTuple) {
+  auto T = std::make_tuple(1, 3, 7);
+  auto U = llvm::apply(
+      [](int A, int B, int C) { return std::make_tuple(A - B, B - C, C - A); },
+      T);
+
+  EXPECT_EQ(-2, std::get<0>(U));
+  EXPECT_EQ(-4, std::get<1>(U));
+  EXPECT_EQ(6, std::get<2>(U));
+
+  auto V = llvm::apply(
+      [](int A, int B, int C) {
+        return std::make_tuple(std::make_pair(A, char('A' + A)),
+                               std::make_pair(B, char('A' + B)),
+                               std::make_pair(C, char('A' + C)));
+      },
+      T);
+
+  EXPECT_EQ(std::make_pair(1, 'B'), std::get<0>(V));
+  EXPECT_EQ(std::make_pair(3, 'D'), std::get<1>(V));
+  EXPECT_EQ(std::make_pair(7, 'H'), std::get<2>(V));
+}
+
+class apply_variadic {
+  static int apply_one(int X) { return X + 1; }
+  static char apply_one(char C) { return C + 1; }
+  static StringRef apply_one(StringRef S) { return S.drop_back(); }
+
+public:
+  template <typename... Ts>
+  auto operator()(Ts &&... Items)
+      -> decltype(std::make_tuple(apply_one(Items)...)) {
+    return std::make_tuple(apply_one(Items)...);
+  }
+};
+
+TEST(STLExtrasTest, ApplyTupleVariadic) {
+  auto Items = std::make_tuple(1, llvm::StringRef("Test"), 'X');
+  auto Values = apply(apply_variadic(), Items);
+
+  EXPECT_EQ(2, std::get<0>(Values));
+  EXPECT_EQ("Tes", std::get<1>(Values));
+  EXPECT_EQ('Y', std::get<2>(Values));
+}
 }