anchor.diff:  	t_guard_receive/1, t_guard_fun/1,
   	t_list_comprehension/1,
   	t_map_sort_literals/1,
  -	%t_size/1,
   	t_map_size/1,
  -
  +	t_build_and_match_aliasing/1,
  +
  +	%% variables
  +	t_build_and_match_variables/1,
  +	t_update_assoc_variables/1,t_update_exact_variables/1,
  +	t_nested_pattern_expressions/1,
  +	t_guard_update_variables/1,
  +	t_guard_sequence_variables/1,
  +	t_guard_sequence_mixed/1,
  +	t_frequency_table/1,
  +
  +	%% not covered in 17.0-rc1
  +	t_build_and_match_over_alloc/1,
  +	t_build_and_match_empty_val/1,
  +	t_build_and_match_val/1,
  +	t_build_and_match_nil/1,
  +	t_build_and_match_structure/1,
  +
  +	%% errors in 17.0-rc1
  +	t_update_values/1,
  +        t_expand_map_update/1,
  +        t_export/1,
  + 
   	%% Specific Map BIFs
   	t_bif_map_get/1,
   	t_bif_map_find/1,
  
positive.code:     {'EXIT',{badarg,_}} = (catch M0#{42=>v1,42.0:=v2,42:=v3}),
  
      ok.
  
  t_guard_bifs(Config) when is_list(Config) ->
      true   = map_guard_head(#{a=>1}),
  
negative.code:     ets:delete(Tid),
      ok.
  
  t_build_and_match_aliasing(Config) when is_list(Config) ->
      M1 = id(#{a=>1,b=>2,c=>3,d=>4}),
      #{c:=C1=_=_=C2} = M1,
      true = C1 =:= C2,
      #{a:=A,a:=A,a:=A,b:=B,b:=B} = M1,
      #{a:=A,a:=A,a:=A,b:=B,b:=B,b:=2} = M1,
      #{a:=A=1,a:=A,a:=A,b:=B=2,b:=B,b:=2} = M1,
      #{c:=C1, c:=_, c:=3, c:=_, c:=C2} = M1,
      #{c:=C=_=3=_=C} = M1,
  
      M2 = id(#{"a"=>1,"b"=>2,"c"=>3,"d"=>4}),
      #{"a":=A2,"a":=A2,"a":=A2,"b":=B2,"b":=B2,"b":=2} = M2,
      #{"a":=_,"a":=_,"a":=_,"b":=_,"b":=_,"b":=2} = M2,
      ok.
  
  %% simple build and match variables
  t_build_and_match_variables(Config) when is_list(Config) ->
      K0 = id(#{}),
      K1 = id(1),       V1 = id(a),
      K2 = id(2),       V2 = id(b),
      K3 = id(3),       V3 = id("c"),
      K4 = id("4"),     V4 = id("d"),
      K5 = id(<<"5">>), V5 = id(<<"e">>),
      K6 = id({"6",7}), V6 = id("f"),
      K7 = id(#{ "a" => 3 }),
      #{K1:=V1} = id(#{K1=>V1}),
      #{K1:=V1,K2:=V2} = id(#{K1=>V1,K2=>V2}),
      #{K1:=V1,K2:=V2,K3:=V3} = id(#{K1=>V1,K2=>V2,K3=>V3}),
      #{K1:=V1,K2:=V2,K3:=V3,K4:=V4} = id(#{K1=>V1,K2=>V2,K3=>V3,K4=>V4}),
      #{K1:=V1,K2:=V2,K3:=V3,K4:=V4,K5:=V5} = id(#{K1=>V1,K2=>V2,K3=>V3,K4=>V4,K5=>V5}),
      #{K1:=V1,K2:=V2,K3:=V3,K4:=V4,K5:=V5,K6:=V6} = id(#{K1=>V1,K2=>V2,K3=>V3,K4=>V4,K5=>V5,K6=>V6}),
  
      #{K5:=X,K5:=X=3,K4:=4} = id(#{K5=>3,K4=>4}),
      #{K5:=X,<<"5">>:=X=3,K4:=4} = id(#{K5=>3,K4=>4}),
      #{K5:=X,<<"5">>:=X=3,K4:=4} = id(#{<<"5">>=>3,K4=>4}),
  
      #{ K4:=#{ K3:=#{K1:=V1, K2:=V2}}, K5:=V5} =
  	id(#{ K5=>V5, K4=>#{ K3=>#{K2 => V2, K1 => V1}}}),
      #{ K4 := #{ K5 := Res }, K6 := Res} = id(#{K4=>#{K5 => 99}, K6 => 99}),
  
      %% has keys
      #{a :=_,b :=_,K1:=_,K2:=_,K3:=V3,K4:=ResKey,K4:=ResKey,"4":=ResKey,"4":="ok"} =
  	id(#{ a=>1, b=>1, K1=>V1, K2=>V2, K3=>V3, K4=>"nope", "4"=>"ok" }),
  
      %% function
      ok = match_function_map_neg_keys(#{ -1 => a, -2 => b, -3 => c }),
  
      %% map key
      #{ K0 := 42 } = id(#{ K0 => 42 }),
      #{ K7 := 42 } = id(#{ K7 => 42 }),
  
      %% nil key
      KNIL = id([]),
      #{KNIL:=ok,1:=2} = id(#{KNIL=>ok,1=>2}),
  
      Bin = <<0:258>>,
      #{ Bin := "three" } = id(#{<<0:258>> =>"three"}),
  
      %% error case
      {'EXIT',{{badmatch,_},_}} = (catch (#{K5:=3,x:=2} = id(#{K5=>3}))),
      {'EXIT',{{badmatch,_},_}} = (catch (#{K5:=2} = id(#{K5=>3}))),
      {'EXIT',{{badmatch,_},_}} = (catch (#{K5:=3} = id({a,b,c}))),
      {'EXIT',{{badmatch,_},_}} = (catch (#{K5:=3} = id(#{K6=>3}))),
      {'EXIT',{{badmatch,_},_}} = (catch (#{K5:=3} = id(K7))),
      {'EXIT',{{badmatch,_},_}} = (catch (#{K7:=3} = id(#{K7=>42}))),
      ok.
  
  
  match_function_map_neg_keys(#{ -1 := a, -2 := b, -3 := c }) -> ok.
  
  t_update_assoc_variables(Config) when is_list(Config) ->
      K1 = id(1),
      K2 = id(2),
      K3 = id(3.0),
      K4 = id(4),
      K5 = id(5),
      K6 = id(2.0),
  
      M0 = #{K1=>a,K2=>b,K3=>c,K4=>d,K5=>e},
  
      M1 = M0#{K1=>42,K2=>100,K4=>[a,b,c]},
      #{1:=42,2:=100,3.0:=c,4:=[a,b,c],5:=e} = M1,
      #{1:=42,2:=b,4:=d,5:=e,2.0:=100,K3:=c,4.0:=[a,b,c]} = M0#{1.0=>float,1:=42,2.0=>wrong,K6=>100,4.0=>[a,b,c]},
  
      M2 = M0#{K3=>new},
      #{1:=a,2:=b,K3:=new,4:=d,5:=e} = M2,
      M2 = M0#{3.0:=wrong,K3=>new},
  
      #{ <<0:258>> := val } = id(M0#{<<0:258>> => val}), %% binary limitation
  
      %% Errors cases.
      BadMap = id(badmap),
      {'EXIT',{{badarg,_},_}} = (catch BadMap#{nonexisting=>val}),
      {'EXIT',{{badarg,_},_}} = (catch <<>>#{nonexisting=>val}),
      ok.
  
  t_update_exact_variables(Config) when is_list(Config) ->
      K1 = id(1),
      K2 = id(2),
      K3 = id(3.0),
      K4 = id(4),
  
      M0 = id(#{1=>a,2=>b,3.0=>c,4=>d,5=>e}),
  
      M1 = M0#{K1:=42,K2:=100,K4:=[a,b,c]},
      #{1:=42,2:=100,3.0:=c,K4:=[a,b,c],5:=e} = M1,
      M1 = M0#{K1:=wrong,1:=also_wrong,K1=>42,2=>wrong,K2:=100,4:=[a,b,c]},
  
      M2 = M0#{K3:=new},
      #{1:=a,K2:=b,3.0:=new,K4:=d,5:=e} = M2,
      M2 = M0#{3.0=>wrong,K3:=new},
      true = M2 =/= M0#{3=>right,3.0:=new},
      #{ 3 := right, 3.0 := new } = M0#{3=>right,K3:=new},
  
      M3 = id(#{ 1 => val}),
      #{1 := update2,1.0 := new_val4} = M3#{
  	1.0 => new_val1, K1 := update, K1=> update3,
  	K1 := update2, 1.0 := new_val2, 1.0 => new_val3,
  	1.0 => new_val4 },
  
      %% Errors cases.
      {'EXIT',{{badarg,_},_}} = (catch ((id(nil))#{ a := b })),
      {'EXIT',{{badarg,_},_}} = (catch <<>>#{nonexisting:=val}),
  
      {'EXIT',{badarg,_}} = (catch M0#{nonexisting:=val}),
      {'EXIT',{badarg,_}} = (catch M0#{1.0:=v,1.0=>v2}),
      {'EXIT',{badarg,_}} = (catch M0#{42.0:=v,42:=v2}),
      {'EXIT',{badarg,_}} = (catch M0#{42=>v1,42.0:=v2,42:=v3}),
      {'EXIT',{badarg,_}} = (catch M0#{<<0:257>> := val}), %% limitation
      ok.
  
  t_nested_pattern_expressions(Config) when is_list(Config) ->
      K1 = id("hello"),
      %K2 = id({ok}),
      [_,_,#{ <<"hi">> := wat, K1 := 42 }|_] = id([k,k,#{<<"hi">> => wat, K1 => 42}]),
      [_,_,#{ -1 := wat, K1 := 42 }|_] = id([k,k,#{-1 => wat, K1 => 42}]),
      [_,_,{#{ -1 := #{ {-3,<<0:300>>} := V1 }, K1 := 42 },3}|_] = id([k,k,{#{-1 => #{{-3,<<0:300>>}=>"hi"}, K1 => 42},3}]),
      "hi" = V1,
      %[k,#{ {-1,K1,[]} := {wat,K1}, K2 := 42 }|_] = id([k,#{{-1,K1,[]} => {wat,K1}, K2 => 42}]),
      %[k,#{ [-1,K2,[]] := {wat,K1}, K1 := 42 }|_] = id([k,#{[-1,K2,[]] => {wat,K1}, K1 => 42}]),
      ok.
  
  t_guard_update_variables(Config) when is_list(Config) ->
      error  = map_guard_update_variables(n,#{},#{}),
      first  = map_guard_update_variables(x,#{}, #{x=>first}),
      second = map_guard_update_variables(x,#{y=>old}, #{x=>second,y=>old}),
      third  = map_guard_update_variables(x,#{x=>old,y=>old}, #{x=>third,y=>old}),
      fourth = map_guard_update_variables(x,#{x=>old,y=>old}, #{x=>4,y=>new}),
      ok.
  
  map_guard_update_variables(K,M1,M2) when M1#{K=>first}    =:= M2 -> first;
  map_guard_update_variables(K,M1,M2) when M1#{K=>second}   =:= M2 -> second;
  map_guard_update_variables(K,M1,M2) when M1#{K:=third}    =:= M2 -> third;
  map_guard_update_variables(K,M1,M2) when M1#{K:=4,y=>new} =:= M2 -> fourth;
  map_guard_update_variables(_,_,_) -> error.
  
  t_guard_sequence_variables(Config) when is_list(Config) ->
      {1,"a"} = map_guard_sequence_var_1(a,#{seq=>1,a=>id("a"),b=>no}),
      {2,"b"} = map_guard_sequence_var_1(b,#{seq=>2,b=>id("b"),a=>no}),
      {3,"c"} = map_guard_sequence_var_1(a,#{seq=>3,a=>id("c"),b=>no}),
      {4,"d"} = map_guard_sequence_var_1(b,#{seq=>4,b=>id("d"),a=>no}),
      {4,4}   = map_guard_sequence_var_1(seq,#{seq=>4}),
      {4,4,y} = map_guard_sequence_var_1(seq,#{seq=>4,b=>id("d"),a=>y}),
      {5,"d"} = map_guard_sequence_var_1(b,#{seq=>5,b=>id("d"),a=>y}),
  
      %% error case
      {'EXIT',{{case_clause,_},_}} = (catch map_guard_sequence_var_1("a",#{seq=>4,val=>id("e")})),
      ok.
  
  
  map_guard_sequence_var_1(K,M) ->
      case M of
  	#{seq:=1=Seq, K:=Val} -> {Seq,Val};
  	#{seq:=2=Seq, K:=Val} -> {Seq,Val};
  	#{seq:=3=Seq, K:=Val} -> {Seq,Val};
  	#{K:=4=Seq,   K:=Val1,a:=Val2} -> {Seq,Val1,Val2};
  	#{seq:=4=Seq, K:=Val} -> {Seq,Val};
  	#{K:=4=Seq,   K:=Val} -> {Seq,Val};
  	#{seq:=5=Seq, K:=Val} -> {Seq,Val}
      end.
  
  
  t_guard_sequence_mixed(Config) when is_list(Config) ->
      M0 = id(#{ a=>1, b=>1, c=>1, d=>1, e=>1, f=>1, g=>1, h=>1 }),
      M1 = id(M0#{ d := 3 }),
      1 = map_guard_sequence_mixed(a,d,M1),
      M2 = id(M1#{ b := 2, d := 4, h := 2 }),
      2 = map_guard_sequence_mixed(a,d,M2),
      M3 = id(M2#{ b := 3, e := 5, g := 3 }),
      3 = map_guard_sequence_mixed(a,e,M3),
      M4 = id(M3#{ c := 4, e := 6, h := 1 }),
      4 = map_guard_sequence_mixed(a,e,M4),
      M5 = id(M4#{ c := 5, f := 7, g := 2 }),
      5 = map_guard_sequence_mixed(a,f,M5),
      M6 = id(M5#{ c := 6, f := 8, h := 3 }),
      6 = map_guard_sequence_mixed(a,f,M6),
  
      %% error case
      {'EXIT',{{case_clause,_},_}} = (catch map_guard_sequence_mixed(a,b,M0)),
      ok.
  
  map_guard_sequence_mixed(K1,K2,M) ->
      case M of
  	#{ K1 := 1, b := 1, K2 := 3, g := 1} -> 1;
  	#{ K1 := 1, b := 2, K2 := 4, h := 2} -> 2;
  	#{ K1 := 1, b := 3, K2 := 5, g := 3} -> 3;
  	#{ K1 := 1, c := 4, K2 := 6, h := 1} -> 4;
  	#{ K1 := 1, c := 5, K2 := 7, g := 2} -> 5;
  	#{ K1 := 1, c := 6, K2 := 8, h := 3} -> 6
      end.
  
  
  
  t_frequency_table(Config) when is_list(Config) ->
      random:seed({13,1337,54}),  % pseudo random
      N = 100000,
      Ts = rand_terms(N),
      #{ n:=N, tf := Tf } = frequency_table(Ts,#{ n=>0, tf => #{}}),
      ok = check_frequency(Ts,Tf),
      ok.
  
  
  frequency_table([T|Ts], M) ->
      case M of
  	#{ n := N, tf := #{ T := C } = F } ->
  	    frequency_table(Ts,M#{ n := N + 1, tf := F#{ T := C + 1 }});
  	#{ n := N, tf := F } ->
  	    frequency_table(Ts,M#{ n := N + 1, tf := F#{ T => 1 }})
      end;
  frequency_table([], M) -> M.
  
  
  check_frequency(Ts,Tf) ->
      check_frequency(Ts,Tf,dict:new()).
  
  check_frequency([T|Ts],Tf,D) ->
      case dict:find(T,D) of
  	error  -> check_frequency(Ts,Tf,dict:store(T,1,D));
  	{ok,C} -> check_frequency(Ts,Tf,dict:store(T,C+1,D))
      end;
  check_frequency([],Tf,D) ->
      validate_frequency(dict:to_list(D),Tf).
  
  validate_frequency([{T,C}|Fs],Tf) ->
      case Tf of
  	#{ T := C } -> validate_frequency(Fs,Tf);
  	_ -> error
      end;
  validate_frequency([], _) -> ok.
  
  
  %% aux
  
  rand_terms(0) -> [];
  rand_terms(N) -> [rand_term()|rand_terms(N-1)].
  
  rand_term() ->
      case random:uniform(6) of
  	1 -> rand_binary();
  	2 -> rand_number();
  	3 -> rand_atom();
  	4 -> rand_tuple();
  	5 -> rand_list();
  	6 -> rand_map()
      end.
  
  rand_binary() ->
      case random:uniform(3) of
  	1 -> <<>>;
  	2 -> <<"hi">>;
  	3 -> <<"message text larger than 64 bytes. yep, message text larger than 64 bytes.">>
      end.
  
  rand_number() ->
      case random:uniform(3) of
  	1 -> random:uniform(5);
  	2 -> float(random:uniform(5));
  	3 -> 1 bsl (63 + random:uniform(3))
      end.
  
  rand_atom() ->
      case random:uniform(3) of
  	1 -> hi;
  	2 -> some_atom;
  	3 -> some_other_atom
      end.
  
  
  rand_tuple() ->
      case random:uniform(3) of
  	1 -> {ok, rand_term()}; % careful
  	2 -> {1, 2, 3};
  	3 -> {<<"yep">>, 1337}
      end.
  
  rand_list() ->
      case random:uniform(3) of
  	1 -> "hi";
  	2 -> [1,rand_term()]; % careful
  	3 -> [improper|list]
      end.
  
  rand_map() ->
      case random:uniform(3) of
  	1 -> #{ hi => 3 };
  	2 -> #{ wat => rand_term(), other => 3 };  % careful
  	3 -> #{ hi => 42, other => 42, yet_anoter => 1337 }
      end.
  
  
  t_build_and_match_over_alloc(Config) when is_list(Config) ->
      Ls = id([1,2,3]),
      V0 = [a|Ls],
      M0 = id(#{ "a" => V0 }),
      #{ "a" := V1 } = M0,
      V2 = id([c|Ls]),
      M2 = id(#{ "a" => V2 }),
      #{ "a" := V3 } = M2,
      {[a,1,2,3],[c,1,2,3]} = id({V1,V3}),
      ok.
  
  t_build_and_match_empty_val(Config) when is_list(Config) ->
      F = fun(#{ "hi":=_,{1,2}:=_,1337:=_}) -> ok end,
      ok = F(id(#{"hi"=>ok,{1,2}=>ok,1337=>ok})),
  
      %% error case
      case (catch (F(id(#{"hi"=>ok})))) of
  	{'EXIT',{function_clause,_}} -> ok;
  	{'EXIT', {{case_clause,_},_}} -> {comment,inlined};
  	Other ->
  	    test_server:fail({no_match, Other})
      end.
  
  t_build_and_match_val(Config) when is_list(Config) ->
      F = fun
  	(#{ "hi" := first,  v := V}) -> {1,V};
  	(#{ "hi" := second, v := V}) -> {2,V}
      end,
  
  
      {1,"hello"}  = F(id(#{"hi"=>first,v=>"hello"})),
      {2,"second"} = F(id(#{"hi"=>second,v=>"second"})),
  
      %% error case
      case (catch (F(id(#{"hi"=>ok})))) of
  	{'EXIT',{function_clause,_}} -> ok;
  	{'EXIT', {{case_clause,_},_}} -> {comment,inlined};
  	Other ->
  	    test_server:fail({no_match, Other})
      end.
  
  t_build_and_match_nil(Config) when is_list(Config) ->
      %% literals removed the coverage
      V1 = id(cookie),
      V2 = id(cake),
      V3 = id(crisps),
  
      #{ [] := V1, "treat" := V2, {your,treat} := V3 } = id(#{
  	    {your,treat} => V3,
  	    "treat" => V2, 
  	    [] => V1 }),
      #{ [] := V3, [] := V3 } = id(#{ [] => V1, [] => V3 }),
      ok.
  
  t_build_and_match_structure(Config) when is_list(Config) ->
      V2 = id("it"),
      S = id([42,{"hi", "=)", #{ "a" => 42, any => any, val => "get_" ++ V2}}]),
  
      %% match deep map values
      V2 = case S of
  	[42,{"hi",_, #{ "a" := 42, val := "get_" ++ V1, any := _ }}] -> V1
      end,
      %% match deep map
      ok = case S of
  	[42,{"hi",_, #{ }}] -> ok
      end,
      ok.
  
  
  
  %% Use this function to avoid compile-time evaluation of an expression.
  id(I) -> I.
  