ADT/STLExtras: Introduce llvm::empty; NFC

This is modeled after C++17 std::empty().

Differential Revision: https://reviews.llvm.org/D53909

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@345679 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 17 insertions, 0 deletions

diff --git a/unittests/ADT/STLExtrasTest.cpp b/unittests/ADT/STLExtrasTest.cpp
index 427d470b61d..80e10d071ab 100644
--- a/unittests/ADT/STLExtrasTest.cpp
+++ b/unittests/ADT/STLExtrasTest.cpp
@@ -364,6 +364,23 @@ TEST(STLExtrasTest, ADLTest) {
   EXPECT_EQ(5, count);
 }
 
+TEST(STLExtrasTest, EmptyTest) {
+  std::vector<void*> V;
+  EXPECT_TRUE(empty(V));
+  V.push_back(nullptr);
+  EXPECT_FALSE(empty(V));
+
+  std::initializer_list<int> E = {};
+  std::initializer_list<int> NotE = {7, 13, 42};
+  EXPECT_TRUE(empty(E));
+  EXPECT_FALSE(empty(NotE));
+
+  auto R0 = make_range(V.begin(), V.begin());
+  EXPECT_TRUE(empty(R0));
+  auto R1 = make_range(V.begin(), V.end());
+  EXPECT_FALSE(empty(R1));
+}
+
 TEST(STLExtrasTest, EarlyIncrementTest) {
   std::list<int> L = {1, 2, 3, 4};