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Implement LWG-3520 #2200

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merged 7 commits into from
Sep 25, 2021
Merged

Implement LWG-3520 #2200

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2e4c239
delete `friend constexpr void iter_swap` for `class transform_view` `…
fsb4000 Sep 12, 2021
109398c
fix tests
fsb4000 Sep 12, 2021
ef6b748
add test
fsb4000 Sep 12, 2021
a456b6c
check unconditionally
fsb4000 Sep 12, 2021
d9c637d
`iter_swap` on `transform_view::iterator` is still possible
fsb4000 Sep 12, 2021
fd1c32a
better variable names
fsb4000 Sep 12, 2021
fe60f6a
Update comment to say "an lvalue"
StephanTLavavej Sep 17, 2021
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9 changes: 0 additions & 9 deletions stl/inc/ranges
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Original file line number Diff line number Diff line change
Expand Up @@ -1988,15 +1988,6 @@ namespace ranges {
return *_It;
}
}

friend constexpr void iter_swap(const _Iterator& _Left, const _Iterator& _Right) _NOEXCEPT_IDL0(noexcept(
_RANGES iter_swap(_Left._Current, _Right._Current))) requires indirectly_swappable<iterator_t<_Base>> {
#if _ITERATOR_DEBUG_LEVEL != 0
_Left._Check_dereference();
_Right._Check_dereference();
#endif // _ITERATOR_DEBUG_LEVEL != 0
_RANGES iter_swap(_Left._Current, _Right._Current);
}
};

template <bool _Const>
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5 changes: 5 additions & 0 deletions tests/std/include/range_algorithm_support.hpp
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Expand Up @@ -1449,3 +1449,8 @@ template <class R>
concept CanBool = requires(R&& r) {
std::forward<R>(r) ? true : false;
};

template <class I>
concept CanIterSwap = requires(I&& i1, I&& i2) {
ranges::iter_swap(std::forward<I>(i1), std::forward<I>(i2));
};
26 changes: 16 additions & 10 deletions tests/std/tests/P0896R4_views_transform/test.cpp
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Expand Up @@ -509,16 +509,7 @@ struct iterator_instantiator {
assert(ranges::iter_move(i0) == add8(mutable_ints[0])); // NB: moving from int leaves it unchanged
STATIC_ASSERT(NOEXCEPT_IDL0(ranges::iter_move(i0)));

if constexpr (forward_iterator<Iter>) {
auto i1 = ranges::next(i0);
ranges::iter_swap(i0, i1);
assert(mutable_ints[0] == 1);
assert(mutable_ints[1] == 0);
ranges::iter_swap(i1, i0);
assert(mutable_ints[0] == 0);
assert(mutable_ints[1] == 1);
STATIC_ASSERT(NOEXCEPT_IDL0(ranges::iter_swap(i0, i1)));
}
STATIC_ASSERT(!CanIterSwap<decltype(i0)>);
}

{ // Validate increments
Expand Down Expand Up @@ -784,4 +775,19 @@ int main() {

(void) views::transform(Fn{})(span<int>{});
}

{ // Validate that iter_swap works when result of transformation is a lvalue reference
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char base[] = "hello";
auto v = ranges::transform_view{base, [](char& c) -> char& { return c; }};
auto i1 = v.begin();
auto i2 = v.begin() + 1;

assert(*i1 == 'h');
assert(*i2 == 'e');

ranges::iter_swap(i1, i2);

assert(*i1 == 'e');
assert(*i2 == 'h');
}
}
23 changes: 0 additions & 23 deletions tests/std/tests/P0896R4_views_transform_death/test.cpp
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Expand Up @@ -287,26 +287,6 @@ void test_iter_move_value_initialized_iterator() {
(void) ranges::iter_move(i); // cannot dereference value-initialized transform_view iterator
}

void test_iter_swap_value_initialized_iterators() {
ranges::iterator_t<TV> i0{};
ranges::iterator_t<TV> i1{};
(void) ranges::iter_swap(i0, i1); // cannot dereference value-initialized transform_view iterator
}

void test_iter_swap_value_initialized_iterator_left() {
ranges::iterator_t<TV> i0{};
TV r{some_ints, lambda};
ranges::iterator_t<TV> i1 = r.begin();
(void) ranges::iter_swap(i0, i1); // cannot dereference value-initialized transform_view iterator
}

void test_iter_swap_value_initialized_iterator_right() {
TV r{some_ints, lambda};
ranges::iterator_t<TV> i0 = r.begin();
ranges::iterator_t<TV> i1{};
(void) ranges::iter_swap(i0, i1); // cannot dereference value-initialized transform_view iterator
}

void test_sentinel_compare_value_initialized() {
auto r = ranges::subrange{counted_iterator{some_ints, ranges::distance(some_ints)}, default_sentinel}
| views::transform(lambda);
Expand Down Expand Up @@ -382,9 +362,6 @@ int main(int argc, char* argv[]) {
test_operator_minus_incompatible_different,
test_operator_minus_incompatible_value_initialized,
test_iter_move_value_initialized_iterator,
test_iter_swap_value_initialized_iterators,
test_iter_swap_value_initialized_iterator_left,
test_iter_swap_value_initialized_iterator_right,
test_sentinel_compare_value_initialized,
test_sentinel_difference_value_initialized,
test_flipped_sentinel_difference_value_initialized,
Expand Down