lang.cpp: In instantiation of 'void Data<T>::operator+=(const Data<T>&) [with T = std::pair<int, int>]':
lang.cpp:63:17: required from here
lang.cpp:34:33: error: no match for 'operator=' (operand types are 'std::pair<int, int>' and 'std::map<std::pair<int, int>, int, std::less<std::pair<int, int> >, std::allocator<std::pair<const std::pair<int, int>, int> > >::mapped_type' {aka 'int'})
34 | p.first = v, p.second = (*this)[k];
| ~~~~~~~~~^~~~~~~~~~
In file included from /usr/include/c++/10/bits/stl_algobase.h:64,
from /usr/include/c++/10/bits/specfun.h:45,
from /usr/include/c++/10/cmath:1927,
from /usr/include/x86_64-linux-gnu/c++/10/bits/stdc++.h:41,
from lang.cpp:3:
/usr/include/c++/10/bits/stl_pair.h:390:7: note: candidate: 'std::pair<_T1, _T2>& std::pair<_T1, _T2>::operator=(typename std::conditional<std::__and_<std::is_copy_assignable<_T1>, std::is_copy_assignable<_T2> >::value, const std::pair<_T1, _T2>&, const std::__nonesuch&>::type) [with _T1 = int; _T2 = int; typename std::conditional<std::__and_<std::is_copy_assignable<_T1>, std::is_copy_assignable<_T2> >::value, const std::pair<_T1, _T2>&, const std::__nonesuch&>::type = const std::pair<int, int>&]'
390 | operator=(typename conditional<
| ^~~~~~~~
/usr/include/c++/10/bits/stl_pair.h:393:41: note: no known conversion for argument 1 from 'std::map<std::pair<int, int>, int, std::less<std::pair<int, int> >, std::allocator<std::pair<const std::pair<int, int>, int> > >::mapped_type' {aka 'int'} to 'std::conditional<true, const std::pair<int, int>&, const std::__nonesuch&>::type' {aka 'const std::pair<int, int>&'}
390 | operator=(typename conditional<
| ~~~~~~~~~~~~~~~~~~~~~
391 | __and_<is_copy_assignable<_T1>,
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
392 | is_copy_assignable<_T2>>::value,
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
393 | const pair&, const __nonesuch&>::type __p)
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~
/usr/include/c++/10/bits/stl_pair.h:401:7: note: candidate: 'std::pair<_T1, _T2>& std::pair<_T1, _T2>::operator=(typename std::conditional<std::__and_<std::is_move_assignable<_Tp>, std::is_move_assignable<_T2> >::value, std::pair<_T1, _T2>&&, std::__nonesuch&&>::type) [with _T1 = int; _T2 = int; typename std::conditional<std::__and_<std::is_move_assignable<_Tp>, std::is_move_assignable<_T2> >::value, std::pair<_T1, _T2>&&, std::__nonesuch&&>::type = std::pair<int, int>&&]'
401 | operator=(typename conditional<
| ^~~~~~~~
/usr/include/c++/10/bits/stl_pair.h:404:31: note: no known conversion for argument 1 from 'std::map<std::pair<int, int>, int, std::less<std::pair<int, int> >, std::allocator<std::pair<const std::pair<int, int>, int> > >::mapped_type' {aka 'int'} to 'std::conditional<true, std::pair<int, int>&&, std::__nonesuch&&>::type' {aka 'std::pair<int, int>&&'}
401 | operator=(typename conditional<
| ~~~~~~~~~~~~~~~~~~~~~
402 | __and_<is_move_assignable<_T1>,
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
403 | is_move_assignable<_T2>>::value,
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
404 | pair&&, __nonesuch&&>::type __p)
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~
/usr/include/c++/10/bits/stl_pair.h:418:2: note: candidate: 'template<class _U1, class _U2> typename std::enable_if<std::__and_<std::is_assignable<_T1&, const _U1&>, std::is_assignable<_T2&, const _U2&> >::value, std::pair<_T1, _T2>&>::type std::pair<_T1, _T2>::operator=(const std::pair<_U1, _U2>&) [with _U1 = _U1; _U2 = _U2; _T1 = int; _T2 = int]'
418 | operator=(const pair<_U1, _U2>& __p)
| ^~~~~~~~
/usr/include/c++/10/bits/stl_pair.h:418:2: note: template argument deduction/substitution failed:
lang.cpp:34:33: note: mismatched types 'const std::pair<_T1, _T2>' and 'std::map<std::pair<int, int>, int, std::less<std::pair<int, int> >, std::allocator<std::pair<const std::pair<int, int>, int> > >::mapped_type' {aka 'int'}
34 | p.first = v, p.second = (*this)[k];
| ~~~~~~~~~^~~~~~~~~~
In file included from /usr/include/c++/10/bits/stl_algobase.h:64,
from /usr/include/c++/10/bits/specfun.h:45,
from /usr/include/c++/10/cmath:1927,
from /usr/include/x86_64-linux-gnu/c++/10/bits/stdc++.h:41,
from lang.cpp:3:
/usr/include/c++/10/bits/stl_pair.h:430:2: note: candidate: 'template<class _U1, class _U2> typename std::enable_if<std::__and_<std::is_assignable<_T1&, _U1&&>, std::is_assignable<_T2&, _U2&&> >::value, std::pair<_T1, _T2>&>::type std::pair<_T1, _T2>::operator=(std::pair<_U1, _U2>&&) [with _U1 = _U1; _U2 = _U2; _T1 = int; _T2 = int]'
430 | operator=(pair<_U1, _U2>&& __p)
| ^~~~~~~~
/usr/include/c++/10/bits/stl_pair.h:430:2: note: template argument deduction/substitution failed:
lang.cpp:34:33: note: mismatched types 'std::pair<_T1, _T2>' and 'std::map<std::pair<int, int>, int, std::less<std::pair<int, int> >, std::allocator<std::pair<const std::pair<int, int>, int> > >::mapped_type' {aka 'int'}
34 | p.first = v, p.second = (*this)[k];
| ~~~~~~~~~^~~~~~~~~~