* [committed] libstdc++: Implement LWG 3877 for std::expected monadic ops
@ 2023-05-17 19:05 Jonathan Wakely
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From: Jonathan Wakely @ 2023-05-17 19:05 UTC (permalink / raw)
To: libstdc++, gcc-patches
Tested powerpc64le-linux. Pushed to trunk.
I'll probably backport this to gcc-13 too.
There are no tests for the changes to and_then and transform, because
LWG 3843 makes that hard to test. Both and_then and transform call
value(), which requires a copy constructible error_type. So we can test
that certain types can never be used as the error-type, but it's not
very useful to test.
-- >8 --
This was approved in Issaquah 2023. As well as fixing the value
categories, this fixes the fact that we were incorrectly testing E
instead of T in the or_else constraints.
libstdc++-v3/ChangeLog:
* include/std/expected (expected::and_then, expected::or_else)
(expected::transform, expected::transform_error): Fix exception
specifications as per LWG 3877.
(expected<void, E>::and_then, expected<void, E>::transform):
Likewise.
* testsuite/20_util/expected/lwg3877.cc: New test.
---
libstdc++-v3/include/std/expected | 48 +++++++-------
.../testsuite/20_util/expected/lwg3877.cc | 64 +++++++++++++++++++
2 files changed, 88 insertions(+), 24 deletions(-)
create mode 100644 libstdc++-v3/testsuite/20_util/expected/lwg3877.cc
diff --git a/libstdc++-v3/include/std/expected b/libstdc++-v3/include/std/expected
index c6d26b0d224..5ea0d6a7cb9 100644
--- a/libstdc++-v3/include/std/expected
+++ b/libstdc++-v3/include/std/expected
@@ -840,7 +840,7 @@ namespace __expected
// monadic operations
- template<typename _Fn> requires is_copy_constructible_v<_Er>
+ template<typename _Fn> requires is_constructible_v<_Er, _Er&>
constexpr auto
and_then(_Fn&& __f) &
{
@@ -854,7 +854,7 @@ namespace __expected
return _Up(unexpect, error());
}
- template<typename _Fn> requires is_copy_constructible_v<_Er>
+ template<typename _Fn> requires is_constructible_v<_Er, const _Er&>
constexpr auto
and_then(_Fn&& __f) const &
{
@@ -868,7 +868,7 @@ namespace __expected
return _Up(unexpect, error());
}
- template<typename _Fn> requires is_move_constructible_v<_Er>
+ template<typename _Fn> requires is_constructible_v<_Er, _Er>
constexpr auto
and_then(_Fn&& __f) &&
{
@@ -883,7 +883,7 @@ namespace __expected
}
- template<typename _Fn> requires is_move_constructible_v<_Er>
+ template<typename _Fn> requires is_constructible_v<_Er, const _Er>
constexpr auto
and_then(_Fn&& __f) const &&
{
@@ -897,7 +897,7 @@ namespace __expected
return _Up(unexpect, std::move(error()));
}
- template<typename _Fn> requires is_copy_constructible_v<_Er>
+ template<typename _Fn> requires is_constructible_v<_Tp, _Tp&>
constexpr auto
or_else(_Fn&& __f) &
{
@@ -911,7 +911,7 @@ namespace __expected
return std::__invoke(std::forward<_Fn>(__f), error());
}
- template<typename _Fn> requires is_copy_constructible_v<_Er>
+ template<typename _Fn> requires is_constructible_v<_Tp, const _Tp&>
constexpr auto
or_else(_Fn&& __f) const &
{
@@ -926,7 +926,7 @@ namespace __expected
}
- template<typename _Fn> requires is_move_constructible_v<_Er>
+ template<typename _Fn> requires is_constructible_v<_Tp, _Tp>
constexpr auto
or_else(_Fn&& __f) &&
{
@@ -940,7 +940,7 @@ namespace __expected
return std::__invoke(std::forward<_Fn>(__f), std::move(error()));
}
- template<typename _Fn> requires is_move_constructible_v<_Er>
+ template<typename _Fn> requires is_constructible_v<_Tp, const _Tp>
constexpr auto
or_else(_Fn&& __f) const &&
{
@@ -954,7 +954,7 @@ namespace __expected
return std::__invoke(std::forward<_Fn>(__f), std::move(error()));
}
- template<typename _Fn> requires is_copy_constructible_v<_Er>
+ template<typename _Fn> requires is_constructible_v<_Er, _Er&>
constexpr auto
transform(_Fn&& __f) &
{
@@ -970,7 +970,7 @@ namespace __expected
return _Res(unexpect, std::move(error()));
}
- template<typename _Fn> requires is_copy_constructible_v<_Er>
+ template<typename _Fn> requires is_constructible_v<_Er, const _Er&>
constexpr auto
transform(_Fn&& __f) const &
{
@@ -986,7 +986,7 @@ namespace __expected
return _Res(unexpect, std::move(error()));
}
- template<typename _Fn> requires is_move_constructible_v<_Er>
+ template<typename _Fn> requires is_constructible_v<_Er, _Er>
constexpr auto
transform(_Fn&& __f) &&
{
@@ -1002,7 +1002,7 @@ namespace __expected
return _Res(unexpect, std::move(error()));
}
- template<typename _Fn> requires is_move_constructible_v<_Er>
+ template<typename _Fn> requires is_constructible_v<_Er, const _Er>
constexpr auto
transform(_Fn&& __f) const &&
{
@@ -1018,7 +1018,7 @@ namespace __expected
return _Res(unexpect, std::move(error()));
}
- template<typename _Fn> requires is_copy_constructible_v<_Tp>
+ template<typename _Fn> requires is_constructible_v<_Tp, _Tp&>
constexpr auto
transform_error(_Fn&& __f) &
{
@@ -1034,7 +1034,7 @@ namespace __expected
});
}
- template<typename _Fn> requires is_copy_constructible_v<_Tp>
+ template<typename _Fn> requires is_constructible_v<_Tp, const _Tp&>
constexpr auto
transform_error(_Fn&& __f) const &
{
@@ -1050,7 +1050,7 @@ namespace __expected
});
}
- template<typename _Fn> requires is_move_constructible_v<_Tp>
+ template<typename _Fn> requires is_constructible_v<_Tp, _Tp>
constexpr auto
transform_error(_Fn&& __f) &&
{
@@ -1066,7 +1066,7 @@ namespace __expected
});
}
- template<typename _Fn> requires is_move_constructible_v<_Tp>
+ template<typename _Fn> requires is_constructible_v<_Tp, const _Tp>
constexpr auto
transform_error(_Fn&& __f) const &&
{
@@ -1519,7 +1519,7 @@ namespace __expected
// monadic operations
- template<typename _Fn> requires is_copy_constructible_v<_Er>
+ template<typename _Fn> requires is_constructible_v<_Er, _Er&>
constexpr auto
and_then(_Fn&& __f) &
{
@@ -1533,7 +1533,7 @@ namespace __expected
return _Up(unexpect, error());
}
- template<typename _Fn> requires is_copy_constructible_v<_Er>
+ template<typename _Fn> requires is_constructible_v<_Er, const _Er&>
constexpr auto
and_then(_Fn&& __f) const &
{
@@ -1547,7 +1547,7 @@ namespace __expected
return _Up(unexpect, error());
}
- template<typename _Fn> requires is_move_constructible_v<_Er>
+ template<typename _Fn> requires is_constructible_v<_Er, _Er>
constexpr auto
and_then(_Fn&& __f) &&
{
@@ -1561,7 +1561,7 @@ namespace __expected
return _Up(unexpect, std::move(error()));
}
- template<typename _Fn> requires is_move_constructible_v<_Er>
+ template<typename _Fn> requires is_constructible_v<_Er, const _Er>
constexpr auto
and_then(_Fn&& __f) const &&
{
@@ -1631,7 +1631,7 @@ namespace __expected
return std::__invoke(std::forward<_Fn>(__f), std::move(error()));
}
- template<typename _Fn> requires is_copy_constructible_v<_Er>
+ template<typename _Fn> requires is_constructible_v<_Er, _Er&>
constexpr auto
transform(_Fn&& __f) &
{
@@ -1644,7 +1644,7 @@ namespace __expected
return _Res(unexpect, error());
}
- template<typename _Fn> requires is_copy_constructible_v<_Er>
+ template<typename _Fn> requires is_constructible_v<_Er, const _Er&>
constexpr auto
transform(_Fn&& __f) const &
{
@@ -1657,7 +1657,7 @@ namespace __expected
return _Res(unexpect, error());
}
- template<typename _Fn> requires is_move_constructible_v<_Er>
+ template<typename _Fn> requires is_constructible_v<_Er, _Er>
constexpr auto
transform(_Fn&& __f) &&
{
@@ -1670,7 +1670,7 @@ namespace __expected
return _Res(unexpect, std::move(error()));
}
- template<typename _Fn> requires is_move_constructible_v<_Er>
+ template<typename _Fn> requires is_constructible_v<_Er, const _Er>
constexpr auto
transform(_Fn&& __f) const &&
{
diff --git a/libstdc++-v3/testsuite/20_util/expected/lwg3877.cc b/libstdc++-v3/testsuite/20_util/expected/lwg3877.cc
new file mode 100644
index 00000000000..556d8d5dc9e
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/expected/lwg3877.cc
@@ -0,0 +1,64 @@
+// { dg-options "-std=gnu++23" }
+// { dg-do compile { target c++23 } }
+
+#include <expected>
+
+struct T1
+{
+};
+
+struct T2
+{
+ T2(const T2&) = delete;
+};
+
+struct T3
+{
+ T3(const T3&) = delete;
+ T3(T3&&) = delete;
+ T3(T3&) { }
+ T3(const T3&&) { }
+};
+
+template<typename Exp, typename F>
+concept Has_or_else = requires(Exp&& exp, F f) {
+ std::forward<Exp>(exp).or_else(f);
+};
+
+using E1 = std::expected<T1, int>;
+static_assert( Has_or_else<E1&, E1(int)> );
+static_assert( Has_or_else<const E1&, E1(int)> );
+static_assert( Has_or_else<E1&&, E1(int)> );
+static_assert( Has_or_else<const E1&&, E1(int)> );
+
+using E2 = std::expected<T2, int>;
+static_assert( !Has_or_else<E2&, E2(int)> );
+static_assert( !Has_or_else<const E2&, E2(int)> );
+static_assert( !Has_or_else<E2&&, E2(int)> );
+static_assert( !Has_or_else<const E2&&, E2(int)> );
+
+using E3 = std::expected<T3, int>;
+static_assert( Has_or_else<E3&, E3(int)> );
+static_assert( !Has_or_else<const E3&, E3(int)> );
+static_assert( Has_or_else<E3&&, E3(int)> ); // uses or_else(F) const &&
+static_assert( Has_or_else<const E3&&, E3(int)> );
+
+template<typename Exp, typename F>
+concept Has_transform_error = requires(Exp&& exp, F f) {
+ std::forward<Exp>(exp).transform_error(f);
+};
+
+static_assert( Has_transform_error<E1&, int(int)> );
+static_assert( Has_transform_error<const E1&, int(int)> );
+static_assert( Has_transform_error<E1&&, int(int)> );
+static_assert( Has_transform_error<const E1&&, int(int)> );
+
+static_assert( !Has_transform_error<E2&, int(int)> );
+static_assert( !Has_transform_error<const E2&, int(int)> );
+static_assert( !Has_transform_error<E2&&, int(int)> );
+static_assert( !Has_transform_error<const E2&&, int(int)> );
+
+static_assert( Has_transform_error<E3&, int(int)> );
+static_assert( !Has_transform_error<const E3&, int(int)> );
+static_assert( Has_transform_error<E3&&, int(int)> ); // uses transform_error(F) const &&
+static_assert( Has_transform_error<const E3&&, int(int)> );
--
2.40.1
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2023-05-17 19:05 [committed] libstdc++: Implement LWG 3877 for std::expected monadic ops Jonathan Wakely
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