[libc++] Move .fail.cpp tests with verify-support to .verify.cpp

libcxx/test/std/strings/basic.string/string.capacity/empty.verify.cpp

@@ -0,0 +1,29 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// <string>
+
+// class deque
+
+// bool empty() const noexcept;
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14, c++17
+// REQUIRES: verify-support
+
+#include <string>
+
+#include "test_macros.h"
+
+int main(int, char**)
+{
+    std::string c;
+    c.empty(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+
+    return 0;
+}