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libstdc++: LWG 3301 transform_view::iterator has incorrect iterator_category

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libstdc++-v3/ChangeLog:

	LWG 3301 transform_view::_Iterator has incorrect iterator_category
	* include/std/ranges (transform_view::_Iterator::_S_iter_cat): Adjust
	determination of iterator_category as per LWG 3301.
	* testsuite/std/ranges/adaptors/transform.cc: Augment test.
This commit is contained in:
Patrick Palka 2020-02-24 16:38:07 -05:00
parent 7f0f108309
commit 510bd1c178
3 changed files with 40 additions and 5 deletions
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5
libstdc++-v3/ChangeLog
View File

@ -1,5 +1,10 @@
2020-02-25 Patrick Palka <ppalka@redhat.com>
LWG 3301 transform_view::_Iterator has incorrect iterator_category
* include/std/ranges (transform_view::_Iterator::_S_iter_cat): Adjust
determination of iterator_category as per LWG 3301.
* testsuite/std/ranges/adaptors/transform.cc: Augment test.
LWG 3292 iota_view is under-constrained
* include/std/ranges (iota_view): Require that _Winc models semiregular
as per LWG 3292.

6
libstdc++-v3/include/std/ranges
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@ -1569,6 +1569,9 @@ namespace views
static constexpr auto
_S_iter_cat()
{
using _Res = invoke_result_t<_Fp&, range_reference_t<_Base>>;
if constexpr (is_lvalue_reference_v<_Res>)
{
using _Cat
= typename iterator_traits<_Base_iter>::iterator_category;
@ -1577,6 +1580,9 @@ namespace views
else
return _Cat{};
}
else
return input_iterator_tag{};
}
static constexpr decltype(auto)
__iter_move(const _Iterator& __i = {})

24
libstdc++-v3/testsuite/std/ranges/adaptors/transform.cc
View File

@ -77,10 +77,34 @@ test03()
VERIFY( ranges::equal(v, (int[]){1,2,3,4,5}) );
}
void
test04()
{
// LWG 3301
{
auto f = [] (int x) { return x; };
int x[] = {1,2,3,4,5};
auto v = x | views::transform(f);
auto i = v.begin();
using Cat = decltype(i)::iterator_category;
static_assert(std::same_as<Cat, std::input_iterator_tag>);
}
{
auto f = [] (int &x) -> int& { return x; };
int x[] = {1,2,3,4,5};
auto v = x | views::transform(f);
auto i = v.begin();
using Cat = decltype(i)::iterator_category;
static_assert(std::derived_from<Cat, std::forward_iterator_tag>);
}
}
int
main()
{
test01();
test02();
test03();
test04();
}