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Implement LWG-4222 expected constructor from a single value missing a constraint #5602

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Merged
merged 1 commit into from
Aug 8, 2025
Merged

Implement LWG-4222 expected constructor from a single value missing a constraint #5602

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1 change: 1 addition & 0 deletions stl/inc/expected
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Original file line number Diff line number Diff line change
Expand Up @@ -306,6 +306,7 @@ public:

template <class _Uty = remove_cv_t<_Ty>>
requires (!is_same_v<remove_cvref_t<_Uty>, in_place_t> && !is_same_v<remove_cvref_t<_Uty>, expected>
&& !is_same_v<remove_cvref_t<_Uty>, unexpect_t>
&& !_Is_specialization_v<remove_cvref_t<_Uty>, unexpected>
&& (!is_same_v<remove_cv_t<_Ty>, bool>
#if defined(__clang__) || defined(__EDG__) // TRANSITION, DevCom-10655311
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15 changes: 15 additions & 0 deletions tests/std/tests/P0323R12_expected/test.cpp
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Expand Up @@ -2509,6 +2509,21 @@ static_assert(!is_assignable_v<expected<void, move_only>&, ambiguating_expected_

static_assert(test_lwg_3886());

// Test LWG-4222 "expected constructor from a single value missing a constraint"

struct ConstructibleFromEverything {
explicit ConstructibleFromEverything(auto);
};

struct ConvertibleFromInt {
ConvertibleFromInt(int);
};

static_assert(!is_constructible_v<expected<ConstructibleFromEverything, ConvertibleFromInt>, unexpect_t&>);
static_assert(!is_constructible_v<expected<ConstructibleFromEverything, ConvertibleFromInt>, const unexpect_t&>);
static_assert(!is_constructible_v<expected<ConstructibleFromEverything, ConvertibleFromInt>, unexpect_t>);
static_assert(!is_constructible_v<expected<ConstructibleFromEverything, ConvertibleFromInt>, const unexpect_t>);

int main() {
test_unexpected::test_all();
static_assert(test_unexpected::test_all());
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