C++20 ranges/views are broken, via std::ranges::ref_view - iterator_concepts.h:980:13: error: no matching function for call to '__begin'

[db-src]

It seems that range view adaptors don't work. The following example of trying to use ranges gives a pile of errors, seemingly related to ref_view being broken.

#include <algorithm>
#include <iostream>
#include <ranges>

static auto
odd(int const i)
{
    return (i & 1) == 1;
}
 
static auto
print(int const i)
{
    std::cout << i;
}

auto
main() -> int
{
    int const thenumbers[]{4, 8, 15, 16, 23, 42};
    std::ranges::for_each(thenumbers | std::views::filter(odd), print);
}

This is available on Compiler Explorer running Clang x86-64 trunk here: https://godbolt.org/z/7abh7rzaP - but the same happens in released version 13 there and on Debian

The same is true of the simple (recently edited, now compliant) example code from https://en.cppreference.com/w/cpp/ranges/transform_view ...

#include <algorithm>
#include <cstdio>
#include <iterator>
#include <ranges>
#include <string>
 
char rot13a(const char x, const char a)
{
    return a + (x - a + 13) % 26;
}
 
char rot13(const char x)
{
    if (x >= 'A' && x <= 'Z') {
        return rot13a(x, 'A');
    }
 
    if (x >= 'a' && x <= 'z') {
        return rot13a(x, 'a');
    }
 
    return x;
}
 
int main()
{
    auto show = [](const unsigned char x) { std::putchar(x); };
 
    std::string in{ "cppreference.com\n" };
    std::ranges::for_each(in, show);
    std::ranges::for_each(in | std::views::transform(rot13), show);
 
    std::string out;
    std::ranges::copy( std::views::transform(in, rot13), std::back_inserter(out) );
    std::ranges::for_each(out, show);
    std::ranges::for_each(out | std::views::transform(rot13), show);
}

... as can be seen on Compiler Explorer running Clang x86-64 trunk here - https://godbolt.org/z/xzdzjxaj4 ...

These are the errors from the 1st example:

In file included from <source>:1:
In file included from /opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/algorithm:60:
In file included from /opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/stl_algobase.h:65:
In file included from /opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/stl_iterator_base_types.h:71:
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/iterator_concepts.h:982:13: error: no matching function for call to '__begin'
        = decltype(ranges::__cust_access::__begin(std::declval<_Tp&>()));
                   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/ranges_base.h:595:5: note: in instantiation of template type alias '__range_iter_t' requested here
    using iterator_t = std::__detail::__range_iter_t<_Tp>;
    ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/ranges_util.h:121:36: note: in instantiation of template type alias 'iterator_t' requested here
      requires contiguous_iterator<iterator_t<_Derived>>
                                   ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:1097:29: note: in instantiation of template class 'std::ranges::view_interface<std::ranges::ref_view<const int[6]>>' requested here
    class ref_view : public view_interface<ref_view<_Range>>
                            ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:1151:38: note: in instantiation of template class 'std::ranges::ref_view<const int[6]>' requested here
        concept __can_ref_view = requires { ref_view{std::declval<_Range>()}; };
                                            ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:1151:38: note: in instantiation of requirement here
        concept __can_ref_view = requires { ref_view{std::declval<_Range>()}; };
                                            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:1151:27: note: (skipping 20 contexts in backtrace; use -ftemplate-backtrace-limit=0 to see all)
        concept __can_ref_view = requires { ref_view{std::declval<_Range>()}; };
                                 ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:831:9: note: while substituting template arguments into constraint expression here
      = requires { std::declval<_Adaptor>()(declval<_Args>()...); };
        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:856:5: note: while checking the satisfaction of concept '__adaptor_invocable<std::ranges::views::__adaptor::_Partial<std::ranges::views::_Filter, bool (*)(int)>, const int (&)[6]>' requested here
        && __adaptor_invocable<_Self, _Range>
           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:856:5: note: while substituting template arguments into constraint expression here
        && __adaptor_invocable<_Self, _Range>
           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
<source>:21:38: note: while checking constraint satisfaction for template 'operator|<std::ranges::views::__adaptor::_Partial<std::ranges::views::_Filter, bool (*)(int)>, const int (&)[6]>' required here
    std::ranges::for_each(thenumbers | std::views::filter(odd), print);
                                     ^
<source>:21:38: note: in instantiation of function template specialization 'std::ranges::views::__adaptor::operator|<std::ranges::views::__adaptor::_Partial<std::ranges::views::_Filter, bool (*)(int)>, const int (&)[6]>' requested here
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/iterator_concepts.h:966:7: note: candidate template ignored: constraints not satisfied [with _Tp = std::ranges::ref_view<const int[6]>]
      __begin(_Tp& __t)
      ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/iterator_concepts.h:964:16: note: because 'is_array_v<std::ranges::ref_view<const int[6]> >' evaluated to false
      requires is_array_v<_Tp> || __member_begin<_Tp&> || __adl_begin<_Tp&>
               ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/iterator_concepts.h:964:35: note: and 'std::ranges::ref_view<const int[6]> &' does not satisfy '__member_begin'
      requires is_array_v<_Tp> || __member_begin<_Tp&> || __adl_begin<_Tp&>
                                  ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/iterator_concepts.h:947:23: note: because '__decay_copy(__t.begin())' would be invalid: no member named 'begin' in 'std::ranges::ref_view<const int[6]>'
          { __decay_copy(__t.begin()) } -> input_or_output_iterator;
                             ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/iterator_concepts.h:964:59: note: and 'std::ranges::ref_view<const int[6]> &' does not satisfy '__adl_begin'
      requires is_array_v<_Tp> || __member_begin<_Tp&> || __adl_begin<_Tp&>
                                                          ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/iterator_concepts.h:958:19: note: because '__decay_copy(begin(__t))' would be invalid: call to deleted function 'begin'
          { __decay_copy(begin(__t)) } -> input_or_output_iterator;
                         ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/iterator_concepts.h:982:13: error: no matching function for call to '__begin'
        = decltype(ranges::__cust_access::__begin(std::declval<_Tp&>()));
                   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/ranges_base.h:595:5: note: in instantiation of template type alias '__range_iter_t' requested here
    using iterator_t = std::__detail::__range_iter_t<_Tp>;
    ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/ranges_util.h:127:25: note: in instantiation of template type alias 'iterator_t' requested here
        && contiguous_iterator<iterator_t<const _Derived>>
                               ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:1097:29: note: in instantiation of template class 'std::ranges::view_interface<std::ranges::ref_view<const int[6]>>' requested here
    class ref_view : public view_interface<ref_view<_Range>>
                            ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:1151:38: note: in instantiation of template class 'std::ranges::ref_view<const int[6]>' requested here
        concept __can_ref_view = requires { ref_view{std::declval<_Range>()}; };
                                            ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:1151:38: note: in instantiation of requirement here
        concept __can_ref_view = requires { ref_view{std::declval<_Range>()}; };
                                            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:1151:27: note: (skipping 20 contexts in backtrace; use -ftemplate-backtrace-limit=0 to see all)
        concept __can_ref_view = requires { ref_view{std::declval<_Range>()}; };
                                 ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:831:9: note: while substituting template arguments into constraint expression here
      = requires { std::declval<_Adaptor>()(declval<_Args>()...); };
        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:856:5: note: while checking the satisfaction of concept '__adaptor_invocable<std::ranges::views::__adaptor::_Partial<std::ranges::views::_Filter, bool (*)(int)>, const int (&)[6]>' requested here
        && __adaptor_invocable<_Self, _Range>
           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:856:5: note: while substituting template arguments into constraint expression here
        && __adaptor_invocable<_Self, _Range>
           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
<source>:21:38: note: while checking constraint satisfaction for template 'operator|<std::ranges::views::__adaptor::_Partial<std::ranges::views::_Filter, bool (*)(int)>, const int (&)[6]>' required here
    std::ranges::for_each(thenumbers | std::views::filter(odd), print);
                                     ^
<source>:21:38: note: in instantiation of function template specialization 'std::ranges::views::__adaptor::operator|<std::ranges::views::__adaptor::_Partial<std::ranges::views::_Filter, bool (*)(int)>, const int (&)[6]>' requested here
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/iterator_concepts.h:966:7: note: candidate template ignored: constraints not satisfied [with _Tp = const std::ranges::ref_view<const int[6]>]
      __begin(_Tp& __t)
      ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/iterator_concepts.h:964:16: note: because 'is_array_v<const std::ranges::ref_view<const int[6]> >' evaluated to false
      requires is_array_v<_Tp> || __member_begin<_Tp&> || __adl_begin<_Tp&>
               ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/iterator_concepts.h:964:35: note: and 'const std::ranges::ref_view<const int[6]> &' does not satisfy '__member_begin'
      requires is_array_v<_Tp> || __member_begin<_Tp&> || __adl_begin<_Tp&>
                                  ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/iterator_concepts.h:947:23: note: because '__decay_copy(__t.begin())' would be invalid: no member named 'begin' in 'std::ranges::ref_view<const int[6]>'
          { __decay_copy(__t.begin()) } -> input_or_output_iterator;
                             ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/iterator_concepts.h:964:59: note: and 'const std::ranges::ref_view<const int[6]> &' does not satisfy '__adl_begin'
      requires is_array_v<_Tp> || __member_begin<_Tp&> || __adl_begin<_Tp&>
                                                          ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/iterator_concepts.h:958:19: note: because '__decay_copy(begin(__t))' would be invalid: call to deleted function 'begin'
          { __decay_copy(begin(__t)) } -> input_or_output_iterator;
                         ^
In file included from <source>:1:
In file included from /opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/algorithm:63:
In file included from /opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/ranges_algo.h:36:
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/ranges_util.h:133:24: error: constraints not satisfied for alias template 'sentinel_t' [with _Range = std::ranges::ref_view<const int[6]>]
        && sized_sentinel_for<sentinel_t<_Derived>, iterator_t<_Derived>>
                              ^~~~~~~~~~~~~~~~~~~~
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:1097:29: note: in instantiation of template class 'std::ranges::view_interface<std::ranges::ref_view<const int[6]>>' requested here
    class ref_view : public view_interface<ref_view<_Range>>
                            ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:1151:38: note: in instantiation of template class 'std::ranges::ref_view<const int[6]>' requested here
        concept __can_ref_view = requires { ref_view{std::declval<_Range>()}; };
                                            ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:1151:38: note: in instantiation of requirement here
        concept __can_ref_view = requires { ref_view{std::declval<_Range>()}; };
                                            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:1151:27: note: while substituting template arguments into constraint expression here
        concept __can_ref_view = requires { ref_view{std::declval<_Range>()}; };
                                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:1173:7: note: while checking the satisfaction of concept '__can_ref_view<const int (&)[6]>' requested here
          || __detail::__can_ref_view<_Range>
             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:1173:17: note: (skipping 18 contexts in backtrace; use -ftemplate-backtrace-limit=0 to see all)
          || __detail::__can_ref_view<_Range>
                       ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:831:9: note: while substituting template arguments into constraint expression here
      = requires { std::declval<_Adaptor>()(declval<_Args>()...); };
        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:856:5: note: while checking the satisfaction of concept '__adaptor_invocable<std::ranges::views::__adaptor::_Partial<std::ranges::views::_Filter, bool (*)(int)>, const int (&)[6]>' requested here
        && __adaptor_invocable<_Self, _Range>
           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:856:5: note: while substituting template arguments into constraint expression here
        && __adaptor_invocable<_Self, _Range>
           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
<source>:21:38: note: while checking constraint satisfaction for template 'operator|<std::ranges::views::__adaptor::_Partial<std::ranges::views::_Filter, bool (*)(int)>, const int (&)[6]>' required here
    std::ranges::for_each(thenumbers | std::views::filter(odd), print);
                                     ^
<source>:21:38: note: in instantiation of function template specialization 'std::ranges::views::__adaptor::operator|<std::ranges::views::__adaptor::_Partial<std::ranges::views::_Filter, bool (*)(int)>, const int (&)[6]>' requested here
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/ranges_base.h:597:12: note: because 'std::ranges::ref_view<const int[6]>' does not satisfy 'range'
  template<range _Range>
           ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/ranges_base.h:585:2: 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 <source>:1:
In file included from /opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/algorithm:63:
In file included from /opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/ranges_algo.h:36:
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/ranges_util.h:139:24: error: constraints not satisfied for alias template 'sentinel_t' [with _Range = const std::ranges::ref_view<const int[6]>]
        && sized_sentinel_for<sentinel_t<const _Derived>,
                              ^~~~~~~~~~~~~~~~~~~~~~~~~~
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/ranges_base.h:597:12: note: because 'const std::ranges::ref_view<const int[6]>' does not satisfy 'range'
  template<range _Range>
           ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/ranges_base.h:585:2: note: because 'ranges::begin(__t)' would be invalid: no matching function for call to object of type 'const __cust_access::_Begin'
        ranges::begin(__t);
        ^
<source>:21:38: error: invalid operands to binary expression ('const int[6]' and '_Partial<std::ranges::views::_Filter, decay_t<bool (&)(int)>>' (aka '_Partial<std::ranges::views::_Filter, bool (*)(int)>'))
    std::ranges::for_each(thenumbers | std::views::filter(odd), print);
                          ~~~~~~~~~~ ^ ~~~~~~~~~~~~~~~~~~~~~~~
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:858:7: note: candidate template ignored: constraints not satisfied [with _Self = std::ranges::views::__adaptor::_Partial<std::ranges::views::_Filter, bool (*)(int)>, _Range = const int (&)[6]]
      operator|(_Range&& __r, _Self&& __self)
      ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:856:5: note: because '__adaptor_invocable<std::ranges::views::__adaptor::_Partial<std::ranges::views::_Filter, _Bool (*)(int)>, const int (&)[6]>' evaluated to false
        && __adaptor_invocable<_Self, _Range>
           ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:831:20: note: because 'std::declval<_Adaptor>()(declval<_Args>()...)' would be invalid: no matching function for call to object of type 'std::ranges::views::__adaptor::_Partial<std::ranges::views::_Filter, bool (*)(int)>'
      = requires { std::declval<_Adaptor>()(declval<_Args>()...); };
                   ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:867:7: note: candidate template ignored: constraints not satisfied [with _Lhs = const int *, _Rhs = std::ranges::views::__adaptor::_Partial<std::ranges::views::_Filter, bool (*)(int)>]
      operator|(_Lhs __lhs, _Rhs __rhs)
      ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:864:16: note: because 'derived_from<const int *, std::ranges::views::__adaptor::_RangeAdaptorClosure>' evaluated to false
      requires derived_from<_Lhs, _RangeAdaptorClosure>
               ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/concepts:67:28: note: because '__is_base_of(std::ranges::views::__adaptor::_RangeAdaptorClosure, const int *)' evaluated to false
    concept derived_from = __is_base_of(_Base, _Derived)
                           ^
5 errors generated.
Compiler returned: 1

and 2nd:

In file included from <source>:1:
In file included from /opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/algorithm:60:
In file included from /opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/stl_algobase.h:65:
In file included from /opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/stl_iterator_base_types.h:71:
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/iterator_concepts.h:982:13: error: no matching function for call to '__begin'
        = decltype(ranges::__cust_access::__begin(std::declval<_Tp&>()));
                   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/ranges_base.h:595:5: note: in instantiation of template type alias '__range_iter_t' requested here
    using iterator_t = std::__detail::__range_iter_t<_Tp>;
    ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/ranges_util.h:121:36: note: in instantiation of template type alias 'iterator_t' requested here
      requires contiguous_iterator<iterator_t<_Derived>>
                                   ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:1097:29: note: in instantiation of template class 'std::ranges::view_interface<std::ranges::ref_view<std::basic_string<char>>>' requested here
    class ref_view : public view_interface<ref_view<_Range>>
                            ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:1151:38: note: in instantiation of template class 'std::ranges::ref_view<std::basic_string<char>>' requested here
        concept __can_ref_view = requires { ref_view{std::declval<_Range>()}; };
                                            ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:1151:38: note: in instantiation of requirement here
        concept __can_ref_view = requires { ref_view{std::declval<_Range>()}; };
                                            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:1151:27: note: (skipping 20 contexts in backtrace; use -ftemplate-backtrace-limit=0 to see all)
        concept __can_ref_view = requires { ref_view{std::declval<_Range>()}; };
                                 ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:831:9: note: while substituting template arguments into constraint expression here
      = requires { std::declval<_Adaptor>()(declval<_Args>()...); };
        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:856:5: note: while checking the satisfaction of concept '__adaptor_invocable<std::ranges::views::__adaptor::_Partial<std::ranges::views::_Transform, char (*)(char)>, std::basic_string<char> &>' requested here
        && __adaptor_invocable<_Self, _Range>
           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:856:5: note: while substituting template arguments into constraint expression here
        && __adaptor_invocable<_Self, _Range>
           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
<source>:31:30: note: while checking constraint satisfaction for template 'operator|<std::ranges::views::__adaptor::_Partial<std::ranges::views::_Transform, char (*)(char)>, std::basic_string<char> &>' required here
    std::ranges::for_each(in | std::views::transform(rot13), show);
                             ^
<source>:31:30: note: in instantiation of function template specialization 'std::ranges::views::__adaptor::operator|<std::ranges::views::__adaptor::_Partial<std::ranges::views::_Transform, char (*)(char)>, std::basic_string<char> &>' requested here
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/iterator_concepts.h:966:7: note: candidate template ignored: constraints not satisfied [with _Tp = std::ranges::ref_view<std::basic_string<char>>]
      __begin(_Tp& __t)
      ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/iterator_concepts.h:964:16: note: because 'is_array_v<std::ranges::ref_view<std::basic_string<char> > >' evaluated to false
      requires is_array_v<_Tp> || __member_begin<_Tp&> || __adl_begin<_Tp&>
               ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/iterator_concepts.h:964:35: note: and 'std::ranges::ref_view<std::basic_string<char>> &' does not satisfy '__member_begin'
      requires is_array_v<_Tp> || __member_begin<_Tp&> || __adl_begin<_Tp&>
                                  ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/iterator_concepts.h:947:23: note: because '__decay_copy(__t.begin())' would be invalid: no member named 'begin' in 'std::ranges::ref_view<std::basic_string<char>>'
          { __decay_copy(__t.begin()) } -> input_or_output_iterator;
                             ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/iterator_concepts.h:964:59: note: and 'std::ranges::ref_view<std::basic_string<char>> &' does not satisfy '__adl_begin'
      requires is_array_v<_Tp> || __member_begin<_Tp&> || __adl_begin<_Tp&>
                                                          ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/iterator_concepts.h:958:19: note: because '__decay_copy(begin(__t))' would be invalid: call to deleted function 'begin'
          { __decay_copy(begin(__t)) } -> input_or_output_iterator;
                         ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/iterator_concepts.h:982:13: error: no matching function for call to '__begin'
        = decltype(ranges::__cust_access::__begin(std::declval<_Tp&>()));
                   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/ranges_base.h:595:5: note: in instantiation of template type alias '__range_iter_t' requested here
    using iterator_t = std::__detail::__range_iter_t<_Tp>;
    ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/ranges_util.h:127:25: note: in instantiation of template type alias 'iterator_t' requested here
        && contiguous_iterator<iterator_t<const _Derived>>
                               ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:1097:29: note: in instantiation of template class 'std::ranges::view_interface<std::ranges::ref_view<std::basic_string<char>>>' requested here
    class ref_view : public view_interface<ref_view<_Range>>
                            ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:1151:38: note: in instantiation of template class 'std::ranges::ref_view<std::basic_string<char>>' requested here
        concept __can_ref_view = requires { ref_view{std::declval<_Range>()}; };
                                            ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:1151:38: note: in instantiation of requirement here
        concept __can_ref_view = requires { ref_view{std::declval<_Range>()}; };
                                            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:1151:27: note: (skipping 20 contexts in backtrace; use -ftemplate-backtrace-limit=0 to see all)
        concept __can_ref_view = requires { ref_view{std::declval<_Range>()}; };
                                 ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:831:9: note: while substituting template arguments into constraint expression here
      = requires { std::declval<_Adaptor>()(declval<_Args>()...); };
        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:856:5: note: while checking the satisfaction of concept '__adaptor_invocable<std::ranges::views::__adaptor::_Partial<std::ranges::views::_Transform, char (*)(char)>, std::basic_string<char> &>' requested here
        && __adaptor_invocable<_Self, _Range>
           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:856:5: note: while substituting template arguments into constraint expression here
        && __adaptor_invocable<_Self, _Range>
           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
<source>:31:30: note: while checking constraint satisfaction for template 'operator|<std::ranges::views::__adaptor::_Partial<std::ranges::views::_Transform, char (*)(char)>, std::basic_string<char> &>' required here
    std::ranges::for_each(in | std::views::transform(rot13), show);
                             ^
<source>:31:30: note: in instantiation of function template specialization 'std::ranges::views::__adaptor::operator|<std::ranges::views::__adaptor::_Partial<std::ranges::views::_Transform, char (*)(char)>, std::basic_string<char> &>' requested here
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/iterator_concepts.h:966:7: note: candidate template ignored: constraints not satisfied [with _Tp = const std::ranges::ref_view<std::basic_string<char>>]
      __begin(_Tp& __t)
      ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/iterator_concepts.h:964:16: note: because 'is_array_v<const std::ranges::ref_view<std::basic_string<char> > >' evaluated to false
      requires is_array_v<_Tp> || __member_begin<_Tp&> || __adl_begin<_Tp&>
               ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/iterator_concepts.h:964:35: note: and 'const std::ranges::ref_view<std::basic_string<char>> &' does not satisfy '__member_begin'
      requires is_array_v<_Tp> || __member_begin<_Tp&> || __adl_begin<_Tp&>
                                  ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/iterator_concepts.h:947:23: note: because '__decay_copy(__t.begin())' would be invalid: no member named 'begin' in 'std::ranges::ref_view<std::basic_string<char>>'
          { __decay_copy(__t.begin()) } -> input_or_output_iterator;
                             ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/iterator_concepts.h:964:59: note: and 'const std::ranges::ref_view<std::basic_string<char>> &' does not satisfy '__adl_begin'
      requires is_array_v<_Tp> || __member_begin<_Tp&> || __adl_begin<_Tp&>
                                                          ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/iterator_concepts.h:958:19: note: because '__decay_copy(begin(__t))' would be invalid: call to deleted function 'begin'
          { __decay_copy(begin(__t)) } -> input_or_output_iterator;
                         ^
In file included from <source>:1:
In file included from /opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/algorithm:63:
In file included from /opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/ranges_algo.h:36:
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/ranges_util.h:133:24: error: constraints not satisfied for alias template 'sentinel_t' [with _Range = std::ranges::ref_view<std::basic_string<char>>]
        && sized_sentinel_for<sentinel_t<_Derived>, iterator_t<_Derived>>
                              ^~~~~~~~~~~~~~~~~~~~
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:1097:29: note: in instantiation of template class 'std::ranges::view_interface<std::ranges::ref_view<std::basic_string<char>>>' requested here
    class ref_view : public view_interface<ref_view<_Range>>
                            ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:1151:38: note: in instantiation of template class 'std::ranges::ref_view<std::basic_string<char>>' requested here
        concept __can_ref_view = requires { ref_view{std::declval<_Range>()}; };
                                            ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:1151:38: note: in instantiation of requirement here
        concept __can_ref_view = requires { ref_view{std::declval<_Range>()}; };
                                            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:1151:27: note: while substituting template arguments into constraint expression here
        concept __can_ref_view = requires { ref_view{std::declval<_Range>()}; };
                                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:1173:7: note: while checking the satisfaction of concept '__can_ref_view<std::basic_string<char> &>' requested here
          || __detail::__can_ref_view<_Range>
             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:1173:17: note: (skipping 18 contexts in backtrace; use -ftemplate-backtrace-limit=0 to see all)
          || __detail::__can_ref_view<_Range>
                       ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:831:9: note: while substituting template arguments into constraint expression here
      = requires { std::declval<_Adaptor>()(declval<_Args>()...); };
        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:856:5: note: while checking the satisfaction of concept '__adaptor_invocable<std::ranges::views::__adaptor::_Partial<std::ranges::views::_Transform, char (*)(char)>, std::basic_string<char> &>' requested here
        && __adaptor_invocable<_Self, _Range>
           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:856:5: note: while substituting template arguments into constraint expression here
        && __adaptor_invocable<_Self, _Range>
           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
<source>:31:30: note: while checking constraint satisfaction for template 'operator|<std::ranges::views::__adaptor::_Partial<std::ranges::views::_Transform, char (*)(char)>, std::basic_string<char> &>' required here
    std::ranges::for_each(in | std::views::transform(rot13), show);
                             ^
<source>:31:30: note: in instantiation of function template specialization 'std::ranges::views::__adaptor::operator|<std::ranges::views::__adaptor::_Partial<std::ranges::views::_Transform, char (*)(char)>, std::basic_string<char> &>' requested here
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/ranges_base.h:597:12: note: because 'std::ranges::ref_view<std::basic_string<char>>' does not satisfy 'range'
  template<range _Range>
           ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/ranges_base.h:585:2: 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 <source>:1:
In file included from /opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/algorithm:63:
In file included from /opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/ranges_algo.h:36:
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/ranges_util.h:139:24: error: constraints not satisfied for alias template 'sentinel_t' [with _Range = const std::ranges::ref_view<std::basic_string<char>>]
        && sized_sentinel_for<sentinel_t<const _Derived>,
                              ^~~~~~~~~~~~~~~~~~~~~~~~~~
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/ranges_base.h:597:12: note: because 'const std::ranges::ref_view<std::basic_string<char>>' does not satisfy 'range'
  template<range _Range>
           ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/ranges_base.h:585:2: note: because 'ranges::begin(__t)' would be invalid: no matching function for call to object of type 'const __cust_access::_Begin'
        ranges::begin(__t);
        ^
<source>:31:30: error: invalid operands to binary expression ('std::string' (aka 'basic_string<char>') and '_Partial<std::ranges::views::_Transform, decay_t<char (&)(char)>>' (aka '_Partial<std::ranges::views::_Transform, char (*)(char)>'))
    std::ranges::for_each(in | std::views::transform(rot13), show);
                          ~~ ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/ios_base.h:87:3: note: candidate function not viable: no known conversion from 'std::string' (aka 'basic_string<char>') to 'std::_Ios_Fmtflags' for 1st argument
  operator|(_Ios_Fmtflags __a, _Ios_Fmtflags __b)
  ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/ios_base.h:130:3: note: candidate function not viable: no known conversion from 'std::string' (aka 'basic_string<char>') to 'std::_Ios_Openmode' for 1st argument
  operator|(_Ios_Openmode __a, _Ios_Openmode __b)
  ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/ios_base.h:170:3: note: candidate function not viable: no known conversion from 'std::string' (aka 'basic_string<char>') to 'std::_Ios_Iostate' for 1st argument
  operator|(_Ios_Iostate __a, _Ios_Iostate __b)
  ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/cstddef:132:3: note: candidate function not viable: no known conversion from 'std::string' (aka 'basic_string<char>') to 'std::byte' for 1st argument
  operator|(byte __l, byte __r) noexcept
  ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:858:7: note: candidate template ignored: constraints not satisfied [with _Self = std::ranges::views::__adaptor::_Partial<std::ranges::views::_Transform, char (*)(char)>, _Range = std::basic_string<char> &]
      operator|(_Range&& __r, _Self&& __self)
      ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:856:5: note: because '__adaptor_invocable<std::ranges::views::__adaptor::_Partial<std::ranges::views::_Transform, char (*)(char)>, std::basic_string<char> &>' evaluated to false
        && __adaptor_invocable<_Self, _Range>
           ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:831:20: note: because 'std::declval<_Adaptor>()(declval<_Args>()...)' would be invalid: no matching function for call to object of type 'std::ranges::views::__adaptor::_Partial<std::ranges::views::_Transform, char (*)(char)>'
      = requires { std::declval<_Adaptor>()(declval<_Args>()...); };
                   ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:867:7: note: candidate template ignored: constraints not satisfied [with _Lhs = std::basic_string<char>, _Rhs = std::ranges::views::__adaptor::_Partial<std::ranges::views::_Transform, char (*)(char)>]
      operator|(_Lhs __lhs, _Rhs __rhs)
      ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:864:16: note: because 'derived_from<std::basic_string<char>, std::ranges::views::__adaptor::_RangeAdaptorClosure>' evaluated to false
      requires derived_from<_Lhs, _RangeAdaptorClosure>
               ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/concepts:67:28: note: because '__is_base_of(std::ranges::views::__adaptor::_RangeAdaptorClosure, std::basic_string<char>)' evaluated to false
    concept derived_from = __is_base_of(_Base, _Derived)
                           ^
<source>:34:24: error: no matching function for call to object of type 'const std::ranges::views::_Transform'
    std::ranges::copy( std::views::transform(in, rot13), std::back_inserter(out) );
                       ^~~~~~~~~~~~~~~~~~~~~
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:1975:2: note: candidate template ignored: constraints not satisfied [with _Range = std::basic_string<char> &, _Fp = char (&)(char)]
        operator() [[nodiscard]] (_Range&& __r, _Fp&& __f) const
        ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:1973:21: note: because '__detail::__can_transform_view<std::basic_string<char> &, char (&)(char)>' evaluated to false
        requires __detail::__can_transform_view<_Range, _Fp>
                           ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:1967:17: note: because 'transform_view(std::declval<_Range>(), std::declval<_Fp>())' would be invalid: no viable constructor or deduction guide for deduction of template arguments of 'transform_view'
          = requires { transform_view(std::declval<_Range>(), std::declval<_Fp>()); };
                       ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:890:2: note: candidate template ignored: constraints not satisfied [with _Args = <std::basic_string<char> &, char (&)(char)>]
        operator()(_Args&&... __args) const
        ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:888:11: note: because '__adaptor_partial_app_viable<std::ranges::views::_Transform, std::basic_string<char> &, char (&)(char)>' evaluated to false
        requires __adaptor_partial_app_viable<_Derived, _Args...>
                 ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:837:11: note: because 'sizeof...(_Args) == _Transform::_S_arity - 1' (2 == 1) evaluated to false
      && (sizeof...(_Args) == _Adaptor::_S_arity - 1)
          ^
<source>:36:31: error: invalid operands to binary expression ('std::string' (aka 'basic_string<char>') and '_Partial<std::ranges::views::_Transform, decay_t<char (&)(char)>>' (aka '_Partial<std::ranges::views::_Transform, char (*)(char)>'))
    std::ranges::for_each(out | std::views::transform(rot13), show);
                          ~~~ ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/ios_base.h:87:3: note: candidate function not viable: no known conversion from 'std::string' (aka 'basic_string<char>') to 'std::_Ios_Fmtflags' for 1st argument
  operator|(_Ios_Fmtflags __a, _Ios_Fmtflags __b)
  ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/ios_base.h:130:3: note: candidate function not viable: no known conversion from 'std::string' (aka 'basic_string<char>') to 'std::_Ios_Openmode' for 1st argument
  operator|(_Ios_Openmode __a, _Ios_Openmode __b)
  ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/ios_base.h:170:3: note: candidate function not viable: no known conversion from 'std::string' (aka 'basic_string<char>') to 'std::_Ios_Iostate' for 1st argument
  operator|(_Ios_Iostate __a, _Ios_Iostate __b)
  ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/cstddef:132:3: note: candidate function not viable: no known conversion from 'std::string' (aka 'basic_string<char>') to 'std::byte' for 1st argument
  operator|(byte __l, byte __r) noexcept
  ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:858:7: note: candidate template ignored: constraints not satisfied [with _Self = std::ranges::views::__adaptor::_Partial<std::ranges::views::_Transform, char (*)(char)>, _Range = std::basic_string<char> &]
      operator|(_Range&& __r, _Self&& __self)
      ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:856:5: note: because '__adaptor_invocable<std::ranges::views::__adaptor::_Partial<std::ranges::views::_Transform, char (*)(char)>, std::basic_string<char> &>' evaluated to false
        && __adaptor_invocable<_Self, _Range>
           ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:831:20: note: because 'std::declval<_Adaptor>()(declval<_Args>()...)' would be invalid: no matching function for call to object of type 'std::ranges::views::__adaptor::_Partial<std::ranges::views::_Transform, char (*)(char)>'
      = requires { std::declval<_Adaptor>()(declval<_Args>()...); };
                   ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:867:7: note: candidate template ignored: constraints not satisfied [with _Lhs = std::basic_string<char>, _Rhs = std::ranges::views::__adaptor::_Partial<std::ranges::views::_Transform, char (*)(char)>]
      operator|(_Lhs __lhs, _Rhs __rhs)
      ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/ranges:864:16: note: because 'derived_from<std::basic_string<char>, std::ranges::views::__adaptor::_RangeAdaptorClosure>' evaluated to false
      requires derived_from<_Lhs, _RangeAdaptorClosure>
               ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/concepts:67:28: note: because '__is_base_of(std::ranges::views::__adaptor::_RangeAdaptorClosure, std::basic_string<char>)' evaluated to false
    concept derived_from = __is_base_of(_Base, _Derived)
                           ^
7 errors generated.
Compiler returned: 1

[db-src]

related:

• Compilation error when applying std::views::transform to std::array #48855
• evaluation of constraints for std::ranges::views::drop() fails unnecessarily #46853
• https://bugs.llvm.org/show_bug.cgi?id=50864
• https://bugs.llvm.org/show_bug.cgi?id=44833

[ldionne]

Clang on Godbolt uses libstdc++ by default, not libc++. You need to pass -stdlib=libc++ in order to use libc++: https://godbolt.org/z/f3cdjT61x.

If you do that, you will see that libc++ does not implement all of ranges yet, but we're working on it. In fact, we don't even enable Ranges in the version of LLVM we ship (e.g. 12.0) because we wanted to have a coherent whole before shipping anything.

TLDR: You should report this bug to libstdc++ instead, and you should drop your whiny tone that makes it sound as-if the people who contribute to these OPEN SOURCE projects owe you something, cause that's not helping your case.

[db-src]

Thanks for the explanation, and I apologise for my previous tone.

[jwakely]

TLDR: You should report this bug to libstdc++ instead

Please don't, we have more than one report for this already, and it's a Clang bug: #44178

[llvmbot]

@llvm/issue-subscribers-clang-frontend

[bachittle]

this is fixed as of the latest commit