Crash in gradualizer_fmt:format_type_error: no function_clause_matching

[RobinMorisset]

Running gradualizer on the following erlang code:

-export([f/0]).

f() ->
    fun() when is_list(undefined) ->
        ok
    end.

f(#{(ok#{ok := ok}) := _}) ->
    ok.

results in the following crash:

/home/rmorisset/minimized/test374.erl: escript: exception error: no function clause matching 
                 gradualizer_fmt:format_type_error({illegal_pattern,
                                                    {map,
                                                     {12,8},
                                                     {atom,{12,6},ok},
                                                     [{map_field_exact,
                                                       {12,13},
                                                       {atom,{12,10},ok},
                                                       {atom,{12,16},ok}}]}},
                                                   [{source_file,
                                                     "/home/rmorisset/minimized/test374.erl"},
                                                    {filename,
                                                     "/home/rmorisset/minimized/test374.erl"},
                                                    {forms,
                                                     [{attribute,
                                                       {1,1},
                                                       file,
                                                       {"/home/rmorisset/minimized/test374.erl",
                                                        1}},
                                                      {attribute,
                                                       {4,2},
                                                       module,test374},
                                                      {attribute,
                                                       {5,2},
                                                       export,
                                                       [{f,0}]},
                                                      {function,
                                                       {7,1},
                                                       f,0,
                                                       [{clause,
                                                         {7,1},
                                                         [],[],
                                                         [{'fun',
                                                           {8,5},
                                                           {clauses,
                                                            [{clause,
                                                              {8,8},
                                                              [],
                                                              [[{call,
                                                                 {8,16},
                                                                 {atom,
                                                                  {8,16},
                                                                  is_list},
                                                                 [{atom,
                                                                   {8,24},
                                                                   undefined}]}]],
                                                              [{atom,
                                                                {9,9},
                                                                ok}]}]}}]}]},
                                                      {function,
                                                       {12,1},
                                                       f,1,
                                                       [{clause,
                                                         {12,1},
                                                         [{map,
                                                           {12,3},
                                                           [{map_field_exact,
                                                             {12,21},
                                                             {map,
                                                              {12,8},
                                                              {atom,{12,6},ok},
                                                              [{map_field_exact,
                                                                {12,13},
                                                                {atom,
                                                                 {12,10},
                                                                 ok},
                                                                {atom,
                                                                 {12,16},
                                                                 ok}}]},
                                                             {var,
                                                              {12,24},
                                                              '_'}}]}],
                                                         [],
                                                         [{atom,{13,5},ok}]}]},
                                                      {eof,{14,1}}]}]) (src/gradualizer_fmt.erl, line 50)
  in function  gradualizer_fmt:handle_type_error/2 (src/gradualizer_fmt.erl, line 532)
  in call from gradualizer_fmt:'-print_errors/2-lc$^0/1-0-'/2 (src/gradualizer_fmt.erl, line 518)
  in call from gradualizer_fmt:print_errors/2 (src/gradualizer_fmt.erl, line 518)
  in call from gradualizer:type_check_forms/3 (src/gradualizer.erl, line 326)
  in call from gradualizer:'-type_check_files/2-fun-1-'/4 (src/gradualizer.erl, line 276)
  in call from lists:foldl/3 (lists.erl, line 1350)
  in call from gradualizer_cli:main/1 (src/gradualizer_cli.erl, line 17)