% g++ -std=c++20 -o main main.cpp
In file included from /usr/include/c++/10.1.0/ext/alloc_traits.h:34,
                 from /usr/include/c++/10.1.0/bits/stl_uninitialized.h:67,
                 from /usr/include/c++/10.1.0/vector:66,
                 from /usr/include/entt/core/algorithm.hpp:5,
                 from /usr/include/entt/entt.hpp:1,
                 from main.cpp:1:
/usr/include/c++/10.1.0/bits/alloc_traits.h: In instantiation of ‘static constexpr void std::allocator_traits<std::allocator<_Up> >::construct(std::allocator_traits<std::allocator<_Up> >::allocator_type&, _Up*, _Args&& ...) [with _Up = Component; _Args = {}; _Tp = Component; std::allocator_traits<std::allocator<_Up> >::allocator_type = std::allocator<Component>]’:
/usr/include/c++/10.1.0/bits/vector.tcc:115:30:   required from ‘std::vector<_Tp, _Alloc>::reference std::vector<_Tp, _Alloc>::emplace_back(_Args&& ...) [with _Args = {}; _Tp = Component; _Alloc = std::allocator<Component>; std::vector<_Tp, _Alloc>::reference = Component&]’
/usr/include/entt/entity/storage.hpp:327:35:   required from ‘void entt::storage<Entity, Type, <template-parameter-1-3> >::emplace(entt::storage<Entity, Type, <template-parameter-1-3> >::entity_type, Args&& ...) [with Args = {}; Entity = entt::entity; Type = Component; <template-parameter-1-3> = void; entt::storage<Entity, Type, <template-parameter-1-3> >::entity_type = entt::entity]’
/usr/include/entt/entity/registry.hpp:66:53:   required from ‘decltype(auto) entt::basic_registry< <template-parameter-1-1> >::pool_handler<Component>::emplace(entt::basic_registry< <template-parameter-1-1> >&, Entity, Args&& ...) [with Args = {}; Component = Component; Entity = entt::entity]’
/usr/include/entt/entity/registry.hpp:647:43:   required from ‘decltype(auto) entt::basic_registry< <template-parameter-1-1> >::emplace(entt::basic_registry< <template-parameter-1-1> >::entity_type, Args&& ...) [with Component = Component; Args = {}; Entity = entt::entity; entt::basic_registry< <template-parameter-1-1> >::entity_type = entt::entity]’
/usr/include/entt/entity/registry.hpp:654:34:   required from ‘decltype(auto) entt::basic_registry< <template-parameter-1-1> >::assign(entt::basic_registry< <template-parameter-1-1> >::entity_type, Args&& ...) [with Component = Component; Args = {}; Entity = entt::entity; entt::basic_registry< <template-parameter-1-1> >::entity_type = entt::entity]’
/usr/include/entt/entity/registry.hpp:786:57:   required by substitution of ‘template<class Component, class ... Func> decltype (((entt::basic_registry< <template-parameter-1-1> >::replace::func((declval<Component&>)()) , ...), ((entt::basic_registry<entt::entity>*)this)->assign<Component>(entity))) entt::basic_registry<entt::entity>::replace<Component, Func ...>(entt::basic_registry<entt::entity>::entity_type, Func&& ...) [with Component = Component; Func = <missing>]’
main.cpp:14:42:   required from here
/usr/include/c++/10.1.0/bits/alloc_traits.h:514:21: error: no matching function for call to ‘construct_at(Component*&)’
  514 |    std::construct_at(__p, std::forward<_Args>(__args)...);
      |    ~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from /usr/include/c++/10.1.0/bits/stl_tempbuf.h:60,
                 from /usr/include/c++/10.1.0/bits/stl_algo.h:62,
                 from /usr/include/c++/10.1.0/vector:62,
                 from /usr/include/entt/core/algorithm.hpp:5,
                 from /usr/include/entt/entt.hpp:1,
                 from main.cpp:1:
/usr/include/c++/10.1.0/bits/stl_construct.h:94:5: note: candidate: ‘template<class _Tp, class ... _Args> constexpr decltype (::new(void*(0)) _Tp) std::construct_at(_Tp*, _Args&& ...)’
   94 |     construct_at(_Tp* __location, _Args&&... __args)
      |     ^~~~~~~~~~~~
/usr/include/c++/10.1.0/bits/stl_construct.h:94:5: note:   template argument deduction/substitution failed:
/usr/include/c++/10.1.0/bits/stl_construct.h: In substitution of ‘template<class _Tp, class ... _Args> constexpr decltype (::new(void*(0)) _Tp) std::construct_at(_Tp*, _Args&& ...) [with _Tp = Component; _Args = {}]’:
/usr/include/c++/10.1.0/bits/alloc_traits.h:514:21:   required from ‘static constexpr void std::allocator_traits<std::allocator<_Up> >::construct(std::allocator_traits<std::allocator<_Up> >::allocator_type&, _Up*, _Args&& ...) [with _Up = Component; _Args = {}; _Tp = Component; std::allocator_traits<std::allocator<_Up> >::allocator_type = std::allocator<Component>]’
/usr/include/c++/10.1.0/bits/vector.tcc:115:30:   required from ‘std::vector<_Tp, _Alloc>::reference std::vector<_Tp, _Alloc>::emplace_back(_Args&& ...) [with _Args = {}; _Tp = Component; _Alloc = std::allocator<Component>; std::vector<_Tp, _Alloc>::reference = Component&]’
/usr/include/entt/entity/storage.hpp:327:35:   required from ‘void entt::storage<Entity, Type, <template-parameter-1-3> >::emplace(entt::storage<Entity, Type, <template-parameter-1-3> >::entity_type, Args&& ...) [with Args = {}; Entity = entt::entity; Type = Component; <template-parameter-1-3> = void; entt::storage<Entity, Type, <template-parameter-1-3> >::entity_type = entt::entity]’
/usr/include/entt/entity/registry.hpp:66:53:   required from ‘decltype(auto) entt::basic_registry< <template-parameter-1-1> >::pool_handler<Component>::emplace(entt::basic_registry< <template-parameter-1-1> >&, Entity, Args&& ...) [with Args = {}; Component = Component; Entity = entt::entity]’
/usr/include/entt/entity/registry.hpp:647:43:   required from ‘decltype(auto) entt::basic_registry< <template-parameter-1-1> >::emplace(entt::basic_registry< <template-parameter-1-1> >::entity_type, Args&& ...) [with Component = Component; Args = {}; Entity = entt::entity; entt::basic_registry< <template-parameter-1-1> >::entity_type = entt::entity]’
/usr/include/entt/entity/registry.hpp:654:34:   required from ‘decltype(auto) entt::basic_registry< <template-parameter-1-1> >::assign(entt::basic_registry< <template-parameter-1-1> >::entity_type, Args&& ...) [with Component = Component; Args = {}; Entity = entt::entity; entt::basic_registry< <template-parameter-1-1> >::entity_type = entt::entity]’
/usr/include/entt/entity/registry.hpp:786:57:   required by substitution of ‘template<class Component, class ... Func> decltype (((entt::basic_registry< <template-parameter-1-1> >::replace::func((declval<Component&>)()) , ...), ((entt::basic_registry<entt::entity>*)this)->assign<Component>(entity))) entt::basic_registry<entt::entity>::replace<Component, Func ...>(entt::basic_registry<entt::entity>::entity_type, Func&& ...) [with Component = Component; Func = <missing>]’
main.cpp:14:42:   required from here
/usr/include/c++/10.1.0/bits/stl_construct.h:96:17: error: no matching function for call to ‘Component::Component()’
   96 |     -> decltype(::new((void*)0) _Tp(std::declval<_Args>()...))
      |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
main.cpp:6:5: note: candidate: ‘Component::Component(int)’
    6 |     Component(int a) : a(a) {}
      |     ^~~~~~~~~
main.cpp:6:5: note:   candidate expects 1 argument, 0 provided
main.cpp:3:8: note: candidate: ‘constexpr Component::Component(const Component&)’
    3 | struct Component {
      |        ^~~~~~~~~
main.cpp:3:8: note:   candidate expects 1 argument, 0 provided
main.cpp:3:8: note: candidate: ‘constexpr Component::Component(Component&&)’
main.cpp:3:8: note:   candidate expects 1 argument, 0 provided