fix(tests): read cbor byte view via std::span, not basic_string_view<std::byte>

[aruisdante]

Problem

macos-latest (tests) is red on current CI (and will fail on main the next time that job runs — main is green only because its last macOS run predates the runner-image bump). The failure is in an unrelated test, not in whatever PR happens to trigger the run:

tests/cbor/test_read_byte_containers.cpp:34
  std::basic_string_view<std::byte> byte_view(...);
error: 'char_traits<std::byte>' is deprecated: char_traits<T> for T not equal to
char, wchar_t, char8_t, char16_t or char32_t is non-standard ... [-Werror,-Wdeprecated-declarations]

GitHub moved the macos-latest image to macOS 15 + Xcode 26.5, whose libc++ now marks std::char_traits<T> deprecated for any T outside {char, wchar_t, char8_t, char16_t, char32_t}. std::basic_string_view<std::byte> instantiates the now-deprecated std::char_traits<std::byte>, and the test suite builds with -Werror (tests/CMakeLists.txt), so the deprecation is a hard error.

It only shows up in one matrix cell because that cell is the sole intersection of "new libc++" and "compiles the tests": macos-15-intel still runs an older toolchain, and the benchmarks cells never compile the test files.

Change

Read the CBOR bytes through std::span<const std::byte> instead of std::basic_string_view<std::byte>.

std::span is the idiomatic non-owning byte view, does not depend on char_traits at all, and satisfies the same rfl::concepts::ContiguousByteContainer that rfl::cbor::read requires (std::byte is byte-like; ByteSpanLike's own doc-comment names span views as intended input) — so the test exercises the identical read overload. The sibling std::uint8_t-array test is unchanged.

The libc++ specialization is slated for removal, not just deprecation, so migrating off it is the durable fix rather than suppressing the warning with a diagnostic pragma.

Testing

Verified with Apple clang 21 on macOS 26.5 (same libc++ that ships the deprecation), using the exact CI flags (-std=gnu++20 -Wall -Werror -Wdeprecated-declarations):

• The original basic_string_view<std::byte> reproduces the error.
• std::span<const std::byte> compiles clean and static_asserts green against the real rfl::concepts::ContiguousByteContainer / ByteSpanLike from include/rfl/concepts.hpp.

Note

Independent of, and complementary to, #688 (a C++26 clang crash workaround touching only StringLiteral.hpp); that PR's red macOS cell is this same pre-existing toolchain regression, not anything in its diff.

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Disclosure: this investigation and patch were produced with the assistance of an AI coding agent (Claude Code / Claude Opus), reviewed by me before submitting.

[gemini-code-assist]

Code Review

This pull request updates tests/cbor/test_read_byte_containers.cpp to replace the use of std::basic_string_view<std::byte> with std::span<const std::byte>. This change avoids compilation errors under -Werror on newer toolchains like libc++ (Xcode 26.5+), which deprecates std::char_traits<std::byte>. There are no review comments, so I have no feedback to provide.

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[liuzicheng1987]

@aruisdante sorry, it took me quite a while to notice your PR