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Fix thinko in ranges::iter_swap #1072

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Merged
Casey Carter (CaseyCarter) merged 2 commits into from
Jul 30, 2020
Merged

Fix thinko in ranges::iter_swap #1072

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7cce0a0
Fix thinko in ranges::iter_swap
CaseyCarter Jul 21, 2020
0332191
Stephan's review comments
CaseyCarter Jul 22, 2020
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12 changes: 6 additions & 6 deletions stl/inc/xutility
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Original file line number Diff line number Diff line change
Expand Up @@ -1028,10 +1028,10 @@ namespace ranges {
// clang-format on

template <class _Xty, class _Yty>
_NODISCARD constexpr iter_value_t<remove_reference_t<_Xty>> _Iter_exchange_move(
_Xty&& _XVal, _Yty&& _YVal) noexcept(noexcept(iter_value_t<remove_reference_t<_Xty>>(iter_move(_XVal)))) {
iter_value_t<remove_reference_t<_Xty>> _Tmp(iter_move(_XVal));
*_XVal = iter_move(_YVal);
_NODISCARD constexpr iter_value_t<remove_reference_t<_Xty>> _Iter_exchange_move(_Xty&& _XVal,
_Yty&& _YVal) noexcept(noexcept(iter_value_t<remove_reference_t<_Xty>>(_RANGES iter_move(_XVal)))) {
iter_value_t<remove_reference_t<_Xty>> _Tmp(_RANGES iter_move(_XVal));
*_XVal = _RANGES iter_move(_YVal);
return _Tmp;
}

Expand All @@ -1047,7 +1047,7 @@ namespace ranges {
return {_St::_Swap, noexcept(_RANGES swap(*_STD declval<_Ty1>(), *_STD declval<_Ty2>()))};
} else if constexpr (_Symmetric_indirectly_movable_storable<_Ty1, _Ty2>) {
constexpr auto _Nothrow = noexcept(
*_STD declval<_Ty1>() = _Iter_exchange_move(_STD declval<_Ty1>(), _STD declval<_Ty2>()));
*_STD declval<_Ty1>() = _Iter_exchange_move(_STD declval<_Ty2>(), _STD declval<_Ty1>()));
return {_St::_Exchange, _Nothrow};
} else {
return {_St::_None};
Expand All @@ -1068,7 +1068,7 @@ namespace ranges {
_RANGES swap(*static_cast<_Ty1&&>(_Val1), *static_cast<_Ty2&&>(_Val2));
} else if constexpr (_Choice<_Ty1, _Ty2>._Strategy == _St::_Exchange) {
*static_cast<_Ty1&&>(_Val1) =
_Iter_exchange_move(static_cast<_Ty1&&>(_Val1), static_cast<_Ty2&&>(_Val2));
_Iter_exchange_move(static_cast<_Ty2&&>(_Val2), static_cast<_Ty1&&>(_Val1));
} else {
static_assert(_Always_false<_Ty1>, "should be unreachable");
}
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27 changes: 22 additions & 5 deletions tests/std/tests/P0896R4_ranges_iterator_machinery/test.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1267,11 +1267,28 @@ namespace iterator_cust_swap_test {
// clang-format on

constexpr bool test() {
int i0 = 42, i1 = 13;
S s0{i0}, s1{i1};
ranges::iter_swap(s0, s1);
assert(i0 == 13);
assert(i1 == 42);
{
int i0 = 42;
int i1 = 13;
S s0{i0};
S s1{i1};
ranges::iter_swap(s0, s1);
assert(i0 == 13);
assert(i1 == 42);
}

#if !defined(__clang__) && !defined(__EDG__) // TRANSITION, VSO-938163
if (!std::is_constant_evaluated())
#endif // TRANSITION, VSO-938163
{
// Validate iter_swap bullet 3 to defend against regression of GH-1067 "ranges::iter_swap is broken"
int i = 42;
long l = 13;
ranges::iter_swap(&i, &l);
assert(i == 13);
assert(l == 42);
}

return true;
}
STATIC_ASSERT(test());
Expand Down