add tests that debug mode catches nullptr->string_view conversions in comparison operators

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@372907 91177308-0d34-0410-b5e6-96231b3b80d8

test/libcxx/debug/db_string_view.pass.cpp

diff --git a/test/libcxx/debug/db_string_view.pass.cpp b/test/libcxx/debug/db_string_view.pass.cpp
index 0753aea..d4ae1ce 100644
--- a/test/libcxx/debug/db_string_view.pass.cpp
+++ b/test/libcxx/debug/db_string_view.pass.cpp
@@ -26,6 +26,11 @@
   EXPECT_DEATH(std::string_view(nullptr));
   EXPECT_DEATH(std::string_view(NULL));
   EXPECT_DEATH(std::string_view(static_cast<const char*>(0)));
+  {
+    std::string_view v;
+    EXPECT_DEATH(((void)(v == nullptr)));
+    EXPECT_DEATH(((void)(nullptr == v)));
+  }
 }
 
 int main(int, char**)