On Tue, 26 May 2020 at 07:39, Ray Lischner via cfe-users <
cfe-users@lists.llvm.org> wrote:
> On 5/15/20 6:53 PM, Richard Smith wrote:
> > Can you try calling begin() on an istream_view<int>& directly, and see
> > if you get the same error?
>
> $ cat istream_begin.cpp
> #include <cassert>
> #include <iostream>
> #include <ranges>
> #include <sstream>
>
> int main()
> {
> auto ints = std::istringstream{"0 1 2 3 4"};
> auto view{ std::ranges::istream_view<int>(ints) };
> auto begin{ std::ranges::begin(view) };
>
Here, Clang claims istream_view<int> has no member named 'begin', during
satisfaction checking.
> assert(&*view.begin() == &*begin);
>
... but Clang accepts this. There's definitely something wrong here.
Can you humor me for a second and try calling 'view.begin()' directly
before using std::ranges::begin? (I'm suspicious that we're somehow not
triggering instantiation of istream_view<int> until too late; calling
'view.begin()' earlier would resolve the problem if that's the case.)
> }
> $ g++ -std=c++20 istream_begin.cpp
> $ ./a.out
> $ clang++ -std=c++20 istream_begin.cpp
> In file included from istream_begin.cpp:2:
> In file included from
>
> /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/iostream:39:
> In file included from
>
> /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/ostream:38:
> In file included from
>
> /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/ios:40:
> In file included from
>
> /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/bits/char_traits.h:39:
> In file included from
>
> /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/bits/stl_algobase.h:65:
> In file included from
>
> /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/bits/stl_iterator_base_types.h:71:
> /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/bits/iterator_concepts.h:902:13:
>
> error: no matching function for call to '__ranges_begin'
> = decltype(__detail::__ranges_begin(std::declval<_Tp&>()));
> ^~~~~~~~~~~~~~~~~~~~~~~~
> /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/bits/range_access.h:874:5:
>
> note: in instantiation of template type alias '__range_iter_t' requested
> here
> using iterator_t = std::__detail::__range_iter_t<_Tp>;
> ^
> /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/ranges:134:43:
>
> note: in instantiation of template type alias 'iterator_t' requested here
> data() requires contiguous_iterator<iterator_t<_Derived>>
> ^
> /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/ranges:956:14:
>
> note: in instantiation of template class
> 'std::ranges::view_interface<std::ranges::basic_istream_view<int, char,
> std::char_traits<char> > >' requested here
> : public view_interface<basic_istream_view<_Val, _CharT, _Traits>>
> ^
> istream_begin.cpp:9:14: note: in instantiation of template class
> 'std::ranges::basic_istream_view<int, char, std::char_traits<char> >'
> requested here
> auto view{ std::ranges::istream_view<int>(ints) };
> ^
> /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/bits/iterator_concepts.h:885:7:
>
> note: candidate template ignored: constraints not satisfied [with _Tp =
> std::ranges::basic_istream_view<int, char, std::char_traits<char> >]
> __ranges_begin(_Tp& __t)
> ^
> /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/bits/iterator_concepts.h:883:16:
>
> note: because 'is_array_v<std::ranges::basic_istream_view<int, char,
> std::char_traits<char> > >' evaluated to false
> requires is_array_v<_Tp> || __member_begin<_Tp&> ||
> __adl_begin<_Tp&>
> ^
> /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/bits/iterator_concepts.h:883:35:
>
> note: and 'std::ranges::basic_istream_view<int, char,
> std::char_traits<char> > &' does not satisfy '__member_begin'
> requires is_array_v<_Tp> || __member_begin<_Tp&> ||
> __adl_begin<_Tp&>
> ^
> /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/bits/iterator_concepts.h:867:33:
>
> note: because '__detail::__decay_copy(__t.begin())' would be invalid: no
> member named 'begin' in 'std::ranges::basic_istream_view<int, char,
> std::char_traits<char> >'
> { __detail::__decay_copy(__t.begin()) } ->
> input_or_output_iterator;
> ^
> /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/bits/iterator_concepts.h:883:59:
>
> note: and 'std::ranges::basic_istream_view<int, char,
> std::char_traits<char> > &' does not satisfy '__adl_begin'
> requires is_array_v<_Tp> || __member_begin<_Tp&> ||
> __adl_begin<_Tp&>
> ^
> /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/bits/iterator_concepts.h:877:29:
>
> note: because '__detail::__decay_copy(begin(__t))' would be invalid:
> call to deleted function 'begin'
> { __detail::__decay_copy(begin(__t)) } ->
> input_or_output_iterator;
> ^
> /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/bits/iterator_concepts.h:902:13:
>
> error: no matching function for call to '__ranges_begin'
> = decltype(__detail::__ranges_begin(std::declval<_Tp&>()));
> ^~~~~~~~~~~~~~~~~~~~~~~~
> /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/bits/range_access.h:874:5:
>
> note: in instantiation of template type alias '__range_iter_t' requested
> here
> using iterator_t = std::__detail::__range_iter_t<_Tp>;
> ^
> /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/ranges:140:25:
>
> note: in instantiation of template type alias 'iterator_t' requested here
> && contiguous_iterator<iterator_t<const _Derived>>
> ^
> /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/ranges:956:14:
>
> note: in instantiation of template class
> 'std::ranges::view_interface<std::ranges::basic_istream_view<int, char,
> std::char_traits<char> > >' requested here
> : public view_interface<basic_istream_view<_Val, _CharT, _Traits>>
> ^
> istream_begin.cpp:9:14: note: in instantiation of template class
> 'std::ranges::basic_istream_view<int, char, std::char_traits<char> >'
> requested here
> auto view{ std::ranges::istream_view<int>(ints) };
> ^
> /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/bits/iterator_concepts.h:885:7:
>
> note: candidate template ignored: constraints not satisfied [with _Tp =
> const std::ranges::basic_istream_view<int, char, std::char_traits<char> >]
> __ranges_begin(_Tp& __t)
> ^
> /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/bits/iterator_concepts.h:883:16:
>
> note: because 'is_array_v<const std::ranges::basic_istream_view<int,
> char, std::char_traits<char> > >' evaluated to false
> requires is_array_v<_Tp> || __member_begin<_Tp&> ||
> __adl_begin<_Tp&>
> ^
> /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/bits/iterator_concepts.h:883:35:
>
> note: and 'const std::ranges::basic_istream_view<int, char,
> std::char_traits<char> > &' does not satisfy '__member_begin'
> requires is_array_v<_Tp> || __member_begin<_Tp&> ||
> __adl_begin<_Tp&>
> ^
> /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/bits/iterator_concepts.h:867:33:
>
> note: because '__detail::__decay_copy(__t.begin())' would be invalid: no
> member named 'begin' in 'std::ranges::basic_istream_view<int, char,
> std::char_traits<char> >'
> { __detail::__decay_copy(__t.begin()) } ->
> input_or_output_iterator;
> ^
> /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/bits/iterator_concepts.h:883:59:
>
> note: and 'const std::ranges::basic_istream_view<int, char,
> std::char_traits<char> > &' does not satisfy '__adl_begin'
> requires is_array_v<_Tp> || __member_begin<_Tp&> ||
> __adl_begin<_Tp&>
> ^
> /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/bits/iterator_concepts.h:877:29:
>
> note: because '__detail::__decay_copy(begin(__t))' would be invalid:
> call to deleted function 'begin'
> { __detail::__decay_copy(begin(__t)) } ->
> input_or_output_iterator;
> ^
> In file included from istream_begin.cpp:3:
> /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/ranges:146:24:
>
> error: constraints not satisfied for alias template 'sentinel_t' [with
> _Range = std::ranges::basic_istream_view<int, char,
> std::char_traits<char> >]
> && sized_sentinel_for<sentinel_t<_Derived>, iterator_t<_Derived>>
> ^~~~~~~~~~~~~~~~~~~~
> /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/ranges:956:14:
>
> note: in instantiation of template class
> 'std::ranges::view_interface<std::ranges::basic_istream_view<int, char,
> std::char_traits<char> > >' requested here
> : public view_interface<basic_istream_view<_Val, _CharT, _Traits>>
> ^
> istream_begin.cpp:9:14: note: in instantiation of template class
> 'std::ranges::basic_istream_view<int, char, std::char_traits<char> >'
> requested here
> auto view{ std::ranges::istream_view<int>(ints) };
> ^
> /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/bits/range_access.h:876:12:
>
> note: because 'std::ranges::basic_istream_view<int, char,
> std::char_traits<char> >' does not satisfy 'range'
> template<range _Range>
> ^
> /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/bits/range_access.h:864:2:
>
> note: because 'ranges::begin(__t)' would be invalid: no matching
> function for call to object of type 'const __cust_access::_Begin'
> ranges::begin(__t);
> ^
> In file included from istream_begin.cpp:3:
> /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/ranges:152:24:
>
> error: constraints not satisfied for alias template 'sentinel_t' [with
> _Range = const std::ranges::basic_istream_view<int, char,
> std::char_traits<char> >]
> && sized_sentinel_for<sentinel_t<const _Derived>,
> ^~~~~~~~~~~~~~~~~~~~~~~~~~
> /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/bits/range_access.h:876:12:
>
> note: because 'const std::ranges::basic_istream_view<int, char,
> std::char_traits<char> >' does not satisfy 'range'
> template<range _Range>
> ^
> /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/bits/range_access.h:864:2:
>
> note: because 'ranges::begin(__t)' would be invalid: no matching
> function for call to object of type 'const __cust_access::_Begin'
> ranges::begin(__t);
> ^
> istream_begin.cpp:10:15: error: no matching function for call to object
> of type 'const __cust_access::_Begin'
> auto begin{ std::ranges::begin(view) };
> ^~~~~~~~~~~~~~~~~~
> /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/bits/range_access.h:400:2:
>
> note: candidate template ignored: constraints not satisfied [with _Tp =
> std::ranges::basic_istream_view<int, char, std::char_traits<char> > &]
> operator()(_Tp&& __t) const noexcept(_S_noexcept<_Tp>())
> ^
> /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/bits/range_access.h:397:11:
>
> note: because
> 'is_array_v<remove_reference_t<std::ranges::basic_istream_view<int,
> char, std::char_traits<char> > &> >' evaluated to false
> requires is_array_v<remove_reference_t<_Tp>> ||
> __member_begin<_Tp>
> ^
> /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/bits/range_access.h:397:50:
>
> note: and 'std::ranges::basic_istream_view<int, char,
> std::char_traits<char> > &' does not satisfy '__member_begin'
> requires is_array_v<remove_reference_t<_Tp>> ||
> __member_begin<_Tp>
> ^
> /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/bits/iterator_concepts.h:867:33:
>
> note: because '__detail::__decay_copy(__t.begin())' would be invalid: no
> member named 'begin' in 'std::ranges::basic_istream_view<int, char,
> std::char_traits<char> >'
> { __detail::__decay_copy(__t.begin()) } ->
> input_or_output_iterator;
> ^
> /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/bits/range_access.h:398:7:
>
> note: and 'std::ranges::basic_istream_view<int, char,
> std::char_traits<char> > &' does not satisfy '__adl_begin'
> || __adl_begin<_Tp>
> ^
> /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/bits/iterator_concepts.h:877:29:
>
> note: because '__detail::__decay_copy(begin(__t))' would be invalid:
> call to deleted function 'begin'
> { __detail::__decay_copy(begin(__t)) } ->
> input_or_output_iterator;
> ^
> 5 errors generated.
>
> --
> Ray Lischner
> _______________________________________________
> cfe-users mailing list
> cfe-users@lists.llvm.org
> https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-users
>
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