Missing operator < for permission_level

[conr2d]

operator < is not overloaded for permission_level, so some std containers of permission_level is not usable.

test.cpp:

#include <eosio/eosio.hpp>
#include <eosio/permission.hpp>

using namespace eosio;

class [[eosio::contract]] test : public contract {
public:
   using contract::contract;

   [[eosio::action]]
   void hi(permission_level p) {
      std::set<permission_level> s;
      s.insert(p);
   }
};

result:

$ eosio-cpp -o test.wasm test.cpp
In file included from /home/conr2d/contracts/test/test.cpp:1:
In file included from /usr/opt/eosio.cdt/1.6.2/bin/../include/eosiolib/contracts/eosio/eosio.hpp:6:
In file included from /usr/opt/eosio.cdt/1.6.2/bin/../include/eosiolib/contracts/eosio/../../contracts/eosio/action.hpp:9:
In file included from /usr/opt/eosio.cdt/1.6.2/bin/../include/eosiolib/core/eosio/datastream.hpp:6:
In file included from /usr/opt/eosio.cdt/1.6.2/bin/../include/eosiolib/contracts/eosio/../../core/eosio/check.hpp:8:
In file included from /usr/opt/eosio.cdt/1.6.2/bin/../include/libcxx/string:470:
In file included from /usr/opt/eosio.cdt/1.6.2/bin/../include/libcxx/string_view:169:
In file included from /usr/opt/eosio.cdt/1.6.2/bin/../include/libcxx/__string:56:
In file included from /usr/opt/eosio.cdt/1.6.2/bin/../include/libcxx/algorithm:643:
In file included from /usr/opt/eosio.cdt/1.6.2/bin/../include/libcxx/memory:650:
In file included from /usr/opt/eosio.cdt/1.6.2/bin/../include/libcxx/iterator:427:
/usr/opt/eosio.cdt/1.6.2/bin/../include/libcxx/__functional_base:55:21: error: invalid operands to binary expression ('const eosio::permission_level' and 'const eosio::permission_level')
        {return __x < __y;}
                ~~~ ^ ~~~
/usr/opt/eosio.cdt/1.6.2/bin/../include/libcxx/__tree:2007:17: note: in instantiation of member function 'std::__1::less<eosio::permission_level>::operator()' requested here
            if (value_comp()(__v, __nd->__value_))
                ^
/usr/opt/eosio.cdt/1.6.2/bin/../include/libcxx/__tree:2131:36: note: in instantiation of function template specialization 'std::__1::__tree<eosio::permission_level, std::__1::less<eosio::permission_level>, std::__1::allocator<eosio::permission_level> >::__find_equal<eosio::permission_level>' requested here
    __node_base_pointer& __child = __find_equal(__parent, __k);
                                   ^
/usr/opt/eosio.cdt/1.6.2/bin/../include/libcxx/__tree:1273:16: note: in instantiation of function template specialization 'std::__1::__tree<eosio::permission_level, std::__1::less<eosio::permission_level>, std::__1::allocator<eosio::permission_level> >::__emplace_unique_key_args<eosio::permission_level, const eosio::permission_level &>' requested here
        return __emplace_unique_key_args(_NodeTypes::__get_key(__v), __v);
               ^
/usr/opt/eosio.cdt/1.6.2/bin/../include/libcxx/set:599:25: note: in instantiation of member function 'std::__1::__tree<eosio::permission_level, std::__1::less<eosio::permission_level>, std::__1::allocator<eosio::permission_level> >::__insert_unique' requested here
        {return __tree_.__insert_unique(__v);}
                        ^
/home/conr2d/contracts/test/test.cpp:13:9: note: in instantiation of member function 'std::__1::set<eosio::permission_level, std::__1::less<eosio::permission_level>, std::__1::allocator<eosio::permission_level> >::insert' requested here
      s.insert(p);
        ^
/usr/opt/eosio.cdt/1.6.2/bin/../include/libcxx/utility:567:1: note: candidate template ignored: could not match 'pair<type-parameter-0-0, type-parameter-0-1>' against 'const eosio::permission_level'
operator< (const pair<_T1,_T2>& __x, const pair<_T1,_T2>& __y)
^
/usr/opt/eosio.cdt/1.6.2/bin/../include/eosiolib/core/eosio/fixed_bytes.hpp:323:9: note: candidate template ignored: could not match 'fixed_bytes<Size>' against 'const eosio::permission_level'
   bool operator <(const fixed_bytes<Size> &c1, const fixed_bytes<Size> &c2) {
        ^
Warning, empty ricardian clause file
Warning, empty ricardian clause file
Warning, action <hi> does not have a ricardian contract
1 error generated.
Error while processing /home/conr2d/contracts/test/test.cpp.
abigen error