From: Jonathan Wakely <jwakely@redhat.com>
To: libstdc++@gcc.gnu.org, gcc-patches@gcc.gnu.org
Subject: Re: [PATCH] libstdc++: Improve static assert messages for monadic operations
Date: Mon, 6 Nov 2023 10:16:43 +0000 [thread overview]
Message-ID: <CACb0b4mv_7geej-L2L-gPv=xbg4oH2brcN1GrDdCKU-4+_tCRg@mail.gmail.com> (raw)
In-Reply-To: <20231102145522.2813330-1-jwakely@redhat.com>
On Thu, 2 Nov 2023 at 14:55, Jonathan Wakely <jwakely@redhat.com> wrote:
>
> Any objections or suggestions for better wording?
>
> Tested x86_64-linux.
Pushed to trunk.
>
> -- >8 --
>
> The monadic operations for std::optional and std::expected make use of
> internal helper traits __is_optional nad __is_expected, which are not
> very user-friendly when shown in diagnostics. Add messages to the
> assertions explaining the problem more clearly.
>
> libstdc++-v3/ChangeLog:
>
> * include/std/expected (expected::and_then, expected::or_else):
> Add string literals to static assertions.
> * include/std/optional (optional::and_then, optional::or_else):
> Likewise.
> ---
> libstdc++-v3/include/std/expected | 64 +++++++++++++++++++++++--------
> libstdc++-v3/include/std/optional | 24 +++++++++---
> 2 files changed, 66 insertions(+), 22 deletions(-)
>
> diff --git a/libstdc++-v3/include/std/expected b/libstdc++-v3/include/std/expected
> index a796f0b6f27..a176d4c3a78 100644
> --- a/libstdc++-v3/include/std/expected
> +++ b/libstdc++-v3/include/std/expected
> @@ -843,8 +843,12 @@ namespace __expected
> and_then(_Fn&& __f) &
> {
> using _Up = __expected::__result<_Fn, _Tp&>;
> - static_assert(__expected::__is_expected<_Up>);
> - static_assert(is_same_v<typename _Up::error_type, _Er>);
> + static_assert(__expected::__is_expected<_Up>,
> + "the function passed to std::expected<T, E>::and_then "
> + "must return a std::expected");
> + static_assert(is_same_v<typename _Up::error_type, _Er>,
> + "the function passed to std::expected<T, E>::and_then "
> + "must return a std::expected with the same error_type");
>
> if (has_value())
> return std::__invoke(std::forward<_Fn>(__f), _M_val);
> @@ -857,8 +861,12 @@ namespace __expected
> and_then(_Fn&& __f) const &
> {
> using _Up = __expected::__result<_Fn, const _Tp&>;
> - static_assert(__expected::__is_expected<_Up>);
> - static_assert(is_same_v<typename _Up::error_type, _Er>);
> + static_assert(__expected::__is_expected<_Up>,
> + "the function passed to std::expected<T, E>::and_then "
> + "must return a std::expected");
> + static_assert(is_same_v<typename _Up::error_type, _Er>,
> + "the function passed to std::expected<T, E>::and_then "
> + "must return a std::expected with the same error_type");
>
> if (has_value())
> return std::__invoke(std::forward<_Fn>(__f), _M_val);
> @@ -871,8 +879,12 @@ namespace __expected
> and_then(_Fn&& __f) &&
> {
> using _Up = __expected::__result<_Fn, _Tp&&>;
> - static_assert(__expected::__is_expected<_Up>);
> - static_assert(is_same_v<typename _Up::error_type, _Er>);
> + static_assert(__expected::__is_expected<_Up>,
> + "the function passed to std::expected<T, E>::and_then "
> + "must return a std::expected");
> + static_assert(is_same_v<typename _Up::error_type, _Er>,
> + "the function passed to std::expected<T, E>::and_then "
> + "must return a std::expected with the same error_type");
>
> if (has_value())
> return std::__invoke(std::forward<_Fn>(__f), std::move(_M_val));
> @@ -886,8 +898,12 @@ namespace __expected
> and_then(_Fn&& __f) const &&
> {
> using _Up = __expected::__result<_Fn, const _Tp&&>;
> - static_assert(__expected::__is_expected<_Up>);
> - static_assert(is_same_v<typename _Up::error_type, _Er>);
> + static_assert(__expected::__is_expected<_Up>,
> + "the function passed to std::expected<T, E>::and_then "
> + "must return a std::expected");
> + static_assert(is_same_v<typename _Up::error_type, _Er>,
> + "the function passed to std::expected<T, E>::and_then "
> + "must return a std::expected with the same error_type");
>
> if (has_value())
> return std::__invoke(std::forward<_Fn>(__f), std::move(_M_val));
> @@ -900,8 +916,12 @@ namespace __expected
> or_else(_Fn&& __f) &
> {
> using _Gr = __expected::__result<_Fn, _Er&>;
> - static_assert(__expected::__is_expected<_Gr>);
> - static_assert(is_same_v<typename _Gr::value_type, _Tp>);
> + static_assert(__expected::__is_expected<_Gr>,
> + "the function passed to std::expected<T, E>::or_else "
> + "must return a std::expected");
> + static_assert(is_same_v<typename _Gr::value_type, _Tp>,
> + "the function passed to std::expected<T, E>::or_else "
> + "must return a std::expected with the same value_type");
>
> if (has_value())
> return _Gr(in_place, _M_val);
> @@ -914,8 +934,12 @@ namespace __expected
> or_else(_Fn&& __f) const &
> {
> using _Gr = __expected::__result<_Fn, const _Er&>;
> - static_assert(__expected::__is_expected<_Gr>);
> - static_assert(is_same_v<typename _Gr::value_type, _Tp>);
> + static_assert(__expected::__is_expected<_Gr>,
> + "the function passed to std::expected<T, E>::or_else "
> + "must return a std::expected");
> + static_assert(is_same_v<typename _Gr::value_type, _Tp>,
> + "the function passed to std::expected<T, E>::or_else "
> + "must return a std::expected with the same value_type");
>
> if (has_value())
> return _Gr(in_place, _M_val);
> @@ -929,8 +953,12 @@ namespace __expected
> or_else(_Fn&& __f) &&
> {
> using _Gr = __expected::__result<_Fn, _Er&&>;
> - static_assert(__expected::__is_expected<_Gr>);
> - static_assert(is_same_v<typename _Gr::value_type, _Tp>);
> + static_assert(__expected::__is_expected<_Gr>,
> + "the function passed to std::expected<T, E>::or_else "
> + "must return a std::expected");
> + static_assert(is_same_v<typename _Gr::value_type, _Tp>,
> + "the function passed to std::expected<T, E>::or_else "
> + "must return a std::expected with the same value_type");
>
> if (has_value())
> return _Gr(in_place, std::move(_M_val));
> @@ -943,8 +971,12 @@ namespace __expected
> or_else(_Fn&& __f) const &&
> {
> using _Gr = __expected::__result<_Fn, const _Er&&>;
> - static_assert(__expected::__is_expected<_Gr>);
> - static_assert(is_same_v<typename _Gr::value_type, _Tp>);
> + static_assert(__expected::__is_expected<_Gr>,
> + "the function passed to std::expected<T, E>::or_else "
> + "must return a std::expected");
> + static_assert(is_same_v<typename _Gr::value_type, _Tp>,
> + "the function passed to std::expected<T, E>::or_else "
> + "must return a std::expected with the same value_type");
>
> if (has_value())
> return _Gr(in_place, std::move(_M_val));
> diff --git a/libstdc++-v3/include/std/optional b/libstdc++-v3/include/std/optional
> index 4f75eb96f97..53450c760d9 100644
> --- a/libstdc++-v3/include/std/optional
> +++ b/libstdc++-v3/include/std/optional
> @@ -1048,7 +1048,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> and_then(_Fn&& __f) &
> {
> using _Up = remove_cvref_t<invoke_result_t<_Fn, _Tp&>>;
> - static_assert(__is_optional_v<remove_cvref_t<_Up>>);
> + static_assert(__is_optional_v<remove_cvref_t<_Up>>,
> + "the function passed to std::optional<T>::and_then "
> + "must return a std::optional");
> if (has_value())
> return std::__invoke(std::forward<_Fn>(__f), **this);
> else
> @@ -1060,7 +1062,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> and_then(_Fn&& __f) const &
> {
> using _Up = remove_cvref_t<invoke_result_t<_Fn, const _Tp&>>;
> - static_assert(__is_optional_v<_Up>);
> + static_assert(__is_optional_v<_Up>,
> + "the function passed to std::optional<T>::and_then "
> + "must return a std::optional");
> if (has_value())
> return std::__invoke(std::forward<_Fn>(__f), **this);
> else
> @@ -1072,7 +1076,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> and_then(_Fn&& __f) &&
> {
> using _Up = remove_cvref_t<invoke_result_t<_Fn, _Tp>>;
> - static_assert(__is_optional_v<remove_cvref_t<_Up>>);
> + static_assert(__is_optional_v<remove_cvref_t<_Up>>,
> + "the function passed to std::optional<T>::and_then "
> + "must return a std::optional");
> if (has_value())
> return std::__invoke(std::forward<_Fn>(__f), std::move(**this));
> else
> @@ -1084,7 +1090,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> and_then(_Fn&& __f) const &&
> {
> using _Up = remove_cvref_t<invoke_result_t<_Fn, const _Tp>>;
> - static_assert(__is_optional_v<remove_cvref_t<_Up>>);
> + static_assert(__is_optional_v<remove_cvref_t<_Up>>,
> + "the function passed to std::optional<T>::and_then "
> + "must return a std::optional");
> if (has_value())
> return std::__invoke(std::forward<_Fn>(__f), std::move(**this));
> else
> @@ -1140,7 +1148,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> or_else(_Fn&& __f) const&
> {
> using _Up = invoke_result_t<_Fn>;
> - static_assert( is_same_v<remove_cvref_t<_Up>, optional> );
> + static_assert(is_same_v<remove_cvref_t<_Up>, optional>,
> + "the function passed to std::optional<T>::or_else "
> + "must return a std::optional<T>");
>
> if (has_value())
> return *this;
> @@ -1153,7 +1163,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> or_else(_Fn&& __f) &&
> {
> using _Up = invoke_result_t<_Fn>;
> - static_assert( is_same_v<remove_cvref_t<_Up>, optional> );
> + static_assert(is_same_v<remove_cvref_t<_Up>, optional>,
> + "the function passed to std::optional<T>::or_else "
> + "must return a std::optional<T>");
>
> if (has_value())
> return std::move(*this);
> --
> 2.41.0
>
prev parent reply other threads:[~2023-11-06 10:17 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-11-02 14:54 Jonathan Wakely
2023-11-06 10:16 ` Jonathan Wakely [this message]
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