<xutility>: basic_const_iterator<int *> cannot convert to basic_const_iterator<const int *> #5321
Description
Describe the bug
The conversion selects the following constructor:
template <convertible_to<_Iter> _Other>
constexpr basic_const_iterator(basic_const_iterator<_Other> _Current_)
noexcept(is_nothrow_constructible_v<_Iter, _Other>) // strengthened
: _Current(_STD move(_Current_._Current)) {}However, it fails at _Current_._Current, which is a private member of basic_const_iterator<int *>. This member cannot be accessed by basic_const_iterator<const int *>, as the latter is not a friend of the former.
Command-line test case
C:\Temp>type repro.cpp
#include <iterator>
int main() {
std::basic_const_iterator<int *> i;
std::basic_const_iterator<const int *> ci = i;
}
C:\Temp>cl /EHsc /W4 /WX /std:c++latest .\repro.cpp
Microsoft (R) C/C++ Optimizing Compiler Version 19.43.34808 for x64
Copyright (C) Microsoft Corporation. All rights reserved.
/std:c++latest is provided as a preview of language features from the latest C++
working draft, and we're eager to hear about bugs and suggestions for improvements.
However, note that these features are provided as-is without support, and subject
to changes or removal as the working draft evolves. See
https://go.microsoft.com/fwlink/?linkid=2045807 for details.
repro.cpp
C:\Program Files (x86)\Microsoft Visual Studio\2022\BuildTools\VC\Tools\MSVC\14.43.34808\include\xutility(2278): error C2248: 'std::basic_const_iterator<int *>::_Current': cannot access private member declared in class 'std::basic_const_iterator<int *>'
C:\Program Files (x86)\Microsoft Visual Studio\2022\BuildTools\VC\Tools\MSVC\14.43.34808\include\xutility(2244): note: see declaration of 'std::basic_const_iterator<int *>::_Current'
C:\Program Files (x86)\Microsoft Visual Studio\2022\BuildTools\VC\Tools\MSVC\14.43.34808\include\xutility(2242): note: see declaration of 'std::basic_const_iterator<int *>'
C:\Program Files (x86)\Microsoft Visual Studio\2022\BuildTools\VC\Tools\MSVC\14.43.34808\include\xutility(2278): note: the template instantiation context (the oldest one first) is
.\repro.cpp(5): note: see reference to function template instantiation 'std::basic_const_iterator<const int *>::basic_const_iterator<int*>(std::basic_const_iterator<int *>) noexcept' being compiled
.\repro.cpp(5): note: see the first reference to 'std::basic_const_iterator<const int *>::basic_const_iterator' in 'main'
Expected behavior
The conversion should be allowed.
STL version
Visual Studio Build Tools 2022
17.13.2