[libc++][NFC] Test span is nothrow trivially destructible

[jloser]

Summary

Add tests showing span is trivially_destructible and nothrow_destructible.
Note that we do not need to explicitly default the destructor in span.

[jloser]

Explicitly include <type_traits> in test

[Mordante]

libcxx/test/std/containers/views/span.cons/span.dtor.pass.cpp

23 ↗

(On Diff #370781)

Since the test doesn't execute any code, please rename the file to span.dtor.compile.pass.cpp and rename main to a different name, test for example.

The types of test files used is documented in utils/libcxx/test/format.py

Lit test format for the C++ Standard Library conformance test suite.        

This test format is based on top of the ShTest format -- it basically       
creates a shell script performing the right operations (compile/link/run)   
based on the extension of the test file it encounters. It supports files    
with the following extensions:                                              

FOO.pass.cpp            - Compiles, links and runs successfully             
FOO.pass.mm             - Same as .pass.cpp, but for Objective-C++          

FOO.compile.pass.cpp    - Compiles successfully, link and run not attempted 
FOO.compile.fail.cpp    - Does not compile successfully                     
    
FOO.link.pass.cpp       - Compiles and links successfully, run not attempted
FOO.link.fail.cpp       - Compiles successfully, but fails to link          
    
FOO.sh.<anything>       - A builtin Lit Shell test

FOO.verify.cpp          - Compiles with clang-verify. This type of test is  
                          automatically marked as UNSUPPORTED if the compiler
                          does not support Clang-verify.

FOO.fail.cpp            - Compiled with clang-verify if clang-verify is     
                          supported, and equivalent to a .compile.fail.cpp  
                          test otherwise. This is supported only for backwards
                          compatibility with the test suite.

25 ↗

(On Diff #370781)

Can you please remove the unneeded space > >?
Once llvm 13 is released we can use its clang-format which doesn't add the unneeded spaces.

[jloser]

Convert test to compile time only test

[jloser]

libcxx/test/std/containers/views/span.cons/span.dtor.pass.cpp

23 ↗

(On Diff #370781)

Thanks for the info on the different types of tests and showing me where I can always look them up for next time; I often forget about some of the differences.

Just renamed to span.dtor.compile.pass.cpp.

[jloser]

[NFC] Move naked static_asserts into test function

[Mordante]

Thanks, LGTM!

libcxx/test/std/containers/views/span.cons/span.dtor.compile.pass.cpp

+//===------------------------------ span ---------------------------------===//
+//
+// 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
+//
+//===---------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <span>
+
+// ~span() = default;
+
+#include <span>
+#include <type_traits>
+
+template <class T>
+constexpr bool test() {
+  return std::is_nothrow_destructible_v<T> && std::is_trivially_destructible_v<T>;
+}
+
+static_assert(test<std::span<int, 1>>());
+static_assert(test<std::span<int>>());