Merge branch 'margnus1/dialyzer-maps/PR-1014'

* margnus1/dialyzer-maps/PR-1014: (24 commits)
  doc: Correct shorthand typo
  stdlib: Correct association types
  stdlib: Add shadow comments for BIFs in maps
  erts: Add exact association types to the abstract format doc
  stdlib: Add pretty-printing of exact map types
  stdlib: Correct a type in module epp
  erl_types: Don't consider opaque keys singleton
  erl_types: Fix t_subtract/2 correctness bug
  erl_types: Fix crash merging maps with opaque keys
  dialyzer_typesig: Fix bad external type
  dialyzer: Fix another pattern literal bug
  Bump Dialyzer version
  dialyzer: Improve map pattern typesetting
  dialyzer_contracts: Consider #{} a violation
  dialyzer_typesig: Fix simplification bug
  dialyzer_dataflow: Fix try in guards
  dialyzer: Unfold cerl patterns containing maps
  dialyzer_dataflow: Add map support
  dialyzer_typesig: Add map support
  Enhance map specs in erts, stdlib, runtime_tools
  ...

71 files changed, 5034 insertions, 150 deletions

diff --git a/bootstrap/lib/stdlib/ebin/erl_parse.beam b/bootstrap/lib/stdlib/ebin/erl_parse.beam
index efe68730d5..9b04739d58 100644
--- a/bootstrap/lib/stdlib/ebin/erl_parse.beam
+++ b/bootstrap/lib/stdlib/ebin/erl_parse.beam
diff --git a/erts/doc/src/absform.xml b/erts/doc/src/absform.xml
index 13756ddfdc..6d6ba224a0 100644
--- a/erts/doc/src/absform.xml
+++ b/erts/doc/src/absform.xml
@@ -636,6 +636,9 @@
        <item>If A is an association type <c>K => V</c>, where
         <c>K</c> and <c>V</c> are types, then Rep(A) =
         <c>{type,LINE,map_field_assoc,[Rep(K),Rep(V)]}</c>.</item>
+       <item>If A is an association type <c>K := V</c>, where
+        <c>K</c> and <c>V</c> are types, then Rep(A) =
+        <c>{type,LINE,map_field_exact,[Rep(K),Rep(V)]}</c>.</item>
       </list>
     </section>
 
diff --git a/erts/preloaded/src/erlang.erl b/erts/preloaded/src/erlang.erl
index 3cc17014ff..20a64e81b4 100644
--- a/erts/preloaded/src/erlang.erl
+++ b/erts/preloaded/src/erlang.erl
@@ -2257,9 +2257,9 @@ spawn_opt(_Tuple) ->
       Input :: non_neg_integer(),
       Output :: non_neg_integer();
                 (microstate_accounting) -> [MSAcc_Thread] | undefined when
-      MSAcc_Thread :: #{ type => MSAcc_Thread_Type,
-                        id => MSAcc_Thread_Id,
-                        counters => MSAcc_Counters},
+      MSAcc_Thread :: #{ type := MSAcc_Thread_Type,
+                        id := MSAcc_Thread_Id,
+                        counters := MSAcc_Counters},
       MSAcc_Thread_Type :: scheduler | async | aux,
       MSAcc_Thread_Id :: non_neg_integer(),
       MSAcc_Counters :: #{ MSAcc_Thread_State => non_neg_integer() },
diff --git a/lib/compiler/src/cerl.erl b/lib/compiler/src/cerl.erl
index 37ec4e97c9..6dc162db40 100644
--- a/lib/compiler/src/cerl.erl
+++ b/lib/compiler/src/cerl.erl
@@ -135,7 +135,7 @@
 	 ann_c_map_pattern/2,
 	 map_pair_op/1,map_pair_key/1,map_pair_val/1,
 	 update_c_map_pair/4,
-	 c_map_pair/2,
+	 c_map_pair/2, c_map_pair_exact/2,
 	 ann_c_map_pair/4
      ]).
 
@@ -1694,6 +1694,11 @@ map_pair_op(#c_map_pair{op=Op}) -> Op.
 c_map_pair(Key,Val) ->
     #c_map_pair{op=#c_literal{val=assoc},key=Key,val=Val}.
 
+-spec c_map_pair_exact(cerl(), cerl()) -> c_map_pair().
+
+c_map_pair_exact(Key,Val) ->
+    #c_map_pair{op=#c_literal{val=exact},key=Key,val=Val}.
+
 -spec ann_c_map_pair([term()], cerl(), cerl(), cerl()) ->
         c_map_pair().
 
diff --git a/lib/dialyzer/src/dialyzer.erl b/lib/dialyzer/src/dialyzer.erl
index 9f51dfe356..bcac8afe64 100644
--- a/lib/dialyzer/src/dialyzer.erl
+++ b/lib/dialyzer/src/dialyzer.erl
@@ -336,6 +336,9 @@ message_to_string({guard_fail, []}) ->
   "Clause guard cannot succeed.\n";
 message_to_string({guard_fail, [Arg1, Infix, Arg2]}) ->
   io_lib:format("Guard test ~s ~s ~s can never succeed\n", [Arg1, Infix, Arg2]);
+message_to_string({map_update, [Type, Key]}) ->
+  io_lib:format("A key of type ~s cannot exist "
+		"in a map of type ~s\n", [Key, Type]);
 message_to_string({neg_guard_fail, [Arg1, Infix, Arg2]}) ->
   io_lib:format("Guard test not(~s ~s ~s) can never succeed\n",
 		[Arg1, Infix, Arg2]);
diff --git a/lib/dialyzer/src/dialyzer.hrl b/lib/dialyzer/src/dialyzer.hrl
index 601e2e954b..ea6a71217c 100644
--- a/lib/dialyzer/src/dialyzer.hrl
+++ b/lib/dialyzer/src/dialyzer.hrl
@@ -60,6 +60,7 @@
 -define(WARN_BEHAVIOUR, warn_behaviour).
 -define(WARN_UNDEFINED_CALLBACK, warn_undefined_callbacks).
 -define(WARN_UNKNOWN, warn_unknown).
+-define(WARN_MAP_CONSTRUCTION, warn_map_construction).
 
 %%
 %% The following type has double role:
@@ -75,7 +76,8 @@
                        | ?WARN_CONTRACT_SUPERTYPE | ?WARN_CALLGRAPH
                        | ?WARN_UNMATCHED_RETURN | ?WARN_RACE_CONDITION
                        | ?WARN_BEHAVIOUR | ?WARN_CONTRACT_RANGE
-		       | ?WARN_UNDEFINED_CALLBACK | ?WARN_UNKNOWN.
+		       | ?WARN_UNDEFINED_CALLBACK | ?WARN_UNKNOWN
+		       | ?WARN_MAP_CONSTRUCTION.
 
 %%
 %% This is the representation of each warning as they will be returned
diff --git a/lib/dialyzer/src/dialyzer_contracts.erl b/lib/dialyzer/src/dialyzer_contracts.erl
index e03e4d5bb4..1895a98e96 100644
--- a/lib/dialyzer/src/dialyzer_contracts.erl
+++ b/lib/dialyzer/src/dialyzer_contracts.erl
@@ -277,28 +277,45 @@ check_extraneous_1(Contract, SuccType) ->
   case [CR || CR <- CRngs,
               erl_types:t_is_none(erl_types:t_inf(CR, STRng))] of
     [] ->
-      CRngList = list_part(CRng),
-      STRngList = list_part(STRng),
-      case is_not_nil_list(CRngList) andalso is_not_nil_list(STRngList) of
-        false -> ok;
-        true ->
-          CRngElements = erl_types:t_list_elements(CRngList),
-          STRngElements = erl_types:t_list_elements(STRngList),
-          Inf = erl_types:t_inf(CRngElements, STRngElements),
-          case erl_types:t_is_none(Inf) of
-            true -> {error, invalid_contract};
-            false -> ok
-          end
+      case bad_extraneous_list(CRng, STRng)
+	orelse bad_extraneous_map(CRng, STRng)
+      of
+	true -> {error, invalid_contract};
+	false -> ok
       end;
     CRs -> {error, {extra_range, erl_types:t_sup(CRs), STRng}}
   end.
 
+bad_extraneous_list(CRng, STRng) ->
+  CRngList = list_part(CRng),
+  STRngList = list_part(STRng),
+  case is_not_nil_list(CRngList) andalso is_not_nil_list(STRngList) of
+    false -> false;
+    true ->
+      CRngElements = erl_types:t_list_elements(CRngList),
+      STRngElements = erl_types:t_list_elements(STRngList),
+      Inf = erl_types:t_inf(CRngElements, STRngElements),
+      erl_types:t_is_none(Inf)
+  end.
+
 list_part(Type) ->
   erl_types:t_inf(erl_types:t_list(), Type).
 
 is_not_nil_list(Type) ->
   erl_types:t_is_list(Type) andalso not erl_types:t_is_nil(Type).
 
+bad_extraneous_map(CRng, STRng) ->
+  CRngMap = map_part(CRng),
+  STRngMap = map_part(STRng),
+  (not is_empty_map(CRngMap)) andalso (not is_empty_map(STRngMap))
+    andalso is_empty_map(erl_types:t_inf(CRngMap, STRngMap)).
+
+map_part(Type) ->
+  erl_types:t_inf(erl_types:t_map(), Type).
+
+is_empty_map(Type) ->
+  erl_types:t_is_equal(Type, erl_types:t_from_term(#{})).
+
 %% This is the heart of the "range function"
 -spec process_contracts([contract_pair()], [erl_types:erl_type()]) ->
                            erl_types:erl_type().
diff --git a/lib/dialyzer/src/dialyzer_dataflow.erl b/lib/dialyzer/src/dialyzer_dataflow.erl
index 6e49043551..f0fa9fbb4e 100644
--- a/lib/dialyzer/src/dialyzer_dataflow.erl
+++ b/lib/dialyzer/src/dialyzer_dataflow.erl
@@ -72,7 +72,7 @@
 	 t_tuple/0, t_tuple/1, t_tuple_args/1, t_tuple_args/2,
          t_tuple_subtypes/2,
 	 t_unit/0, t_unopaque/2,
-	 t_map/1
+	 t_map/0, t_map/1, t_is_singleton/2
      ]).
 
 %%-define(DEBUG, true).
@@ -342,8 +342,6 @@ traverse(Tree, Map, State) ->
       handle_tuple(Tree, Map, State);
     map ->
       handle_map(Tree, Map, State);
-    map_pair ->
-      handle_map_pair(Tree, Map, State);
     values ->
       Elements = cerl:values_es(Tree),
       {State1, Map1, EsType} = traverse_list(Elements, Map, State),
@@ -1102,15 +1100,54 @@ handle_try(Tree, Map, State) ->
 %%----------------------------------------
 
 handle_map(Tree,Map,State) ->
-    Pairs = cerl:map_es(Tree),
-    {State1, Map1, TypePairs} = traverse_list(Pairs,Map,State),
-    {State1, Map1, t_map(TypePairs)}.
+  Pairs = cerl:map_es(Tree),
+  Arg = cerl:map_arg(Tree),
+  {State1, Map1, ArgType} = traverse(Arg, Map, State),
+  ArgType1 = t_inf(t_map(), ArgType),
+  case t_is_none_or_unit(ArgType1) of
+    true ->
+      {State1, Map1, ArgType1};
+    false ->
+      {State2, Map2, TypePairs, ExactKeys} =
+	traverse_map_pairs(Pairs, Map1, State1, t_none(), [], []),
+      InsertPair = fun({KV,assoc,_},Acc) -> erl_types:t_map_put(KV,Acc);
+		      ({KV,exact,KVTree},Acc) ->
+		       case t_is_none(T=erl_types:t_map_update(KV,Acc)) of
+			 true -> throw({none, Acc, KV, KVTree});
+			 false -> T
+		       end
+		   end,
+      try lists:foldl(InsertPair, ArgType1, TypePairs)
+      of ResT ->
+	  BindT = t_map([{K, t_any()} || K <- ExactKeys]),
+	  case bind_pat_vars_reverse([Arg], [BindT], [], Map2, State2) of
+	    {error, _, _, _, _} -> {State2, Map2, ResT};
+	    {Map3, _} ->           {State2, Map3, ResT}
+	  end
+      catch {none, MapType, {K,_}, KVTree} ->
+	  Msg2 = {map_update, [format_type(MapType, State2),
+			       format_type(K, State2)]},
+	  {state__add_warning(State2, ?WARN_MAP_CONSTRUCTION, KVTree, Msg2),
+	   Map2, t_none()}
+      end
+  end.
 
-handle_map_pair(Tree,Map,State) ->
-  Key = cerl:map_pair_key(Tree),
-  Val = cerl:map_pair_val(Tree),
+traverse_map_pairs([], Map, State, _ShadowKeys, PairAcc, KeyAcc) ->
+  {State, Map, lists:reverse(PairAcc), KeyAcc};
+traverse_map_pairs([Pair|Pairs], Map, State, ShadowKeys, PairAcc, KeyAcc) ->
+  Key = cerl:map_pair_key(Pair),
+  Val = cerl:map_pair_val(Pair),
+  Op = cerl:map_pair_op(Pair),
   {State1, Map1, [K,V]} = traverse_list([Key,Val],Map,State),
-  {State1, Map1, {K,V}}.
+  KeyAcc1 =
+    case cerl:is_literal(Op) andalso cerl:concrete(Op) =:= exact andalso
+      t_is_singleton(K, State#state.opaques) andalso
+      t_is_none(t_inf(ShadowKeys, K)) of
+      true -> [K|KeyAcc];
+      false -> KeyAcc
+  end,
+  traverse_map_pairs(Pairs, Map1, State1, t_sup(K, ShadowKeys),
+		     [{{K,V},cerl:concrete(Op),Pair}|PairAcc], KeyAcc1).
 
 %%----------------------------------------
 
@@ -1445,7 +1482,9 @@ bind_pat_vars([Pat|PatLeft], [Type|TypeLeft], Acc, Map, State, Rev) ->
   {NewMap, TypeOut} =
     case cerl:type(Pat) of
       alias ->
-	AliasPat = cerl:alias_pat(Pat),
+	%% Map patterns are more allowing than the type of their literal. We
+	%% must unfold AliasPat if it is a literal.
+	AliasPat = dialyzer_utils:refold_pattern(cerl:alias_pat(Pat)),
 	Var = cerl:alias_var(Pat),
 	Map1 = enter_subst(Var, AliasPat, Map),
 	{Map2, [PatType]} = bind_pat_vars([AliasPat], [Type], [],
@@ -1486,14 +1525,59 @@ bind_pat_vars([Pat|PatLeft], [Type|TypeLeft], Acc, Map, State, Rev) ->
 	    {Map1, t_cons(HdType, TlType)}
 	end;
       literal ->
-	Literal = literal_type(Pat),
-	case t_is_none(t_inf(Literal, Type, Opaques)) of
+	Pat0 = dialyzer_utils:refold_pattern(Pat),
+	case cerl:is_literal(Pat0) of
 	  true ->
-	    bind_opaque_pats(Literal, Type, Pat, State);
-	  false -> {Map, Literal}
+	    Literal = literal_type(Pat),
+	    case t_is_none(t_inf(Literal, Type, Opaques)) of
+	      true ->
+		bind_opaque_pats(Literal, Type, Pat, State);
+	      false -> {Map, Literal}
+	    end;
+	  false ->
+	    %% Retry with the unfolded pattern
+	    {Map1, [PatType]}
+	      = bind_pat_vars([Pat0], [Type], [], Map, State, Rev),
+	    {Map1, PatType}
 	end;
       map ->
-	  {Map, t_map([])};
+	MapT = t_inf(Type, t_map(), Opaques),
+	case t_is_none(MapT) of
+	  true ->
+	    bind_opaque_pats(t_map(), Type, Pat, State);
+	  false ->
+	    case Rev of
+	      %% TODO: Reverse matching (propagating a matched subset back to a value)
+	      true -> {Map, MapT};
+	      false ->
+		FoldFun =
+		  fun(Pair, {MapAcc, ListAcc}) ->
+		      %% Only exact (:=) can appear in patterns
+		      exact = cerl:concrete(cerl:map_pair_op(Pair)),
+		      Key = cerl:map_pair_key(Pair),
+		      KeyType =
+			case cerl:type(Key) of
+			  var ->
+			    case state__lookup_type_for_letrec(Key, State) of
+			      error -> lookup_type(Key, MapAcc);
+			      {ok, RecType} -> RecType
+			    end;
+			  literal ->
+			    literal_type(Key)
+			end,
+		      Bind = erl_types:t_map_get(KeyType, MapT),
+		      {MapAcc1, [ValType]} =
+			bind_pat_vars([cerl:map_pair_val(Pair)],
+				      [Bind], [], MapAcc, State, Rev),
+		      case t_is_singleton(KeyType, Opaques) of
+			true  -> {MapAcc1, [{KeyType, ValType}|ListAcc]};
+			false -> {MapAcc1, ListAcc}
+		      end
+		  end,
+		{Map1, Pairs} = lists:foldl(FoldFun, {Map, []}, cerl:map_es(Pat)),
+		{Map1, t_inf(MapT, t_map(Pairs))}
+	    end
+	end;
       tuple ->
 	Es = cerl:tuple_es(Pat),
 	{TypedRecord, Prototype} =
@@ -1710,15 +1794,58 @@ bind_guard(Guard, Map, Env, Eval, State) ->
     'try' ->
       Arg = cerl:try_arg(Guard),
       [Var] = cerl:try_vars(Guard),
+      EVars = cerl:try_evars(Guard),
       %%?debug("Storing: ~w\n", [Var]),
-      NewEnv = dict:store(get_label(Var), Arg, Env),
-      bind_guard(cerl:try_body(Guard), Map, NewEnv, Eval, State);
+      Map1 = join_maps_begin(Map),
+      Map2 = mark_as_fresh(EVars, Map1),
+      %% Visit handler first so we know if it should be ignored
+      {{HandlerMap, HandlerType}, HandlerE} =
+	try {bind_guard(cerl:try_handler(Guard), Map2, Env, Eval, State), none}
+	catch throw:HE ->
+	    {{Map2, t_none()}, HE}
+	end,
+      BodyEnv = dict:store(get_label(Var), Arg, Env),
+      Wanted = case Eval of pos -> t_atom(true); neg -> t_atom(false);
+		 dont_know -> t_any() end,
+      case t_is_none(t_inf(HandlerType, Wanted)) of
+	%% Handler won't save us; pretend it does not exist
+	true -> bind_guard(cerl:try_body(Guard), Map, BodyEnv, Eval, State);
+	false ->
+	  {{BodyMap, BodyType}, BodyE} =
+	    try {bind_guard(cerl:try_body(Guard), Map1, BodyEnv,
+			    Eval, State), none}
+	    catch throw:BE ->
+		{{Map1, t_none()}, BE}
+	    end,
+	  Map3 = join_maps_end([BodyMap, HandlerMap], Map1),
+	  case t_is_none(Sup = t_sup(BodyType, HandlerType)) of
+	    true ->
+	      %% Pick a reason. N.B. We assume that the handler is always
+	      %% compiler-generated if the body is; that way, we won't need to
+	      %% check.
+	      Fatality = case {BodyE, HandlerE} of
+			   {{fatal_fail, _}, _} -> fatal_fail;
+			   {_, {fatal_fail, _}} -> fatal_fail;
+			   _ -> fail
+			 end,
+	      throw({Fatality,
+		     case {BodyE, HandlerE} of
+		       {{_, Rsn}, _} when Rsn =/= none -> Rsn;
+		       {_, {_,Rsn}} -> Rsn;
+		       _ -> none
+		     end});
+	    false -> {Map3, Sup}
+	  end
+      end;
     tuple ->
       Es0 = cerl:tuple_es(Guard),
       {Map1, Es} = bind_guard_list(Es0, Map, Env, dont_know, State),
       {Map1, t_tuple(Es)};
     map ->
-      {Map, t_map([])};
+      case Eval of
+	dont_know -> handle_guard_map(Guard, Map, Env, State);
+	_PosOrNeg -> {Map, t_none()}  %% Map exprs do not produce bools
+      end;
     'let' ->
       Arg = cerl:let_arg(Guard),
       [Var] = cerl:let_vars(Guard),
@@ -1761,7 +1888,7 @@ handle_guard_call(Guard, Map, Env, Eval, State) ->
     {erlang, F, 1} when F =:= is_atom; F =:= is_boolean;
 			F =:= is_binary; F =:= is_bitstring;
 			F =:= is_float; F =:= is_function;
-			F =:= is_integer; F =:= is_list;
+			F =:= is_integer; F =:= is_list; F =:= is_map;
 			F =:= is_number; F =:= is_pid; F =:= is_port;
 			F =:= is_reference; F =:= is_tuple ->
       handle_guard_type_test(Guard, F, Map, Env, Eval, State);
@@ -1841,6 +1968,7 @@ bind_type_test(Eval, TypeTest, ArgType, State) ->
 	   is_function -> t_fun();
 	   is_integer -> t_integer();
 	   is_list -> t_maybe_improper_list();
+	   is_map -> t_map();
 	   is_number -> t_number();
 	   is_pid -> t_pid();
 	   is_port -> t_port();
@@ -2349,6 +2477,30 @@ bind_guard_list([G|Gs], Map, Env, Eval, State, Acc) ->
 bind_guard_list([], Map, _Env, _Eval, _State, Acc) ->
   {Map, lists:reverse(Acc)}.
 
+handle_guard_map(Guard, Map, Env, State) ->
+  Pairs = cerl:map_es(Guard),
+  Arg = cerl:map_arg(Guard),
+  {Map1, ArgType0} = bind_guard(Arg, Map, Env, dont_know, State),
+  ArgType1 = t_inf(t_map(), ArgType0),
+  case t_is_none_or_unit(ArgType1) of
+    true -> {Map1, t_none()};
+    false ->
+      {Map2, TypePairs} = bind_guard_map_pairs(Pairs, Map1, Env, State, []),
+      {Map2, lists:foldl(fun({KV,assoc},Acc) -> erl_types:t_map_put(KV,Acc);
+			    ({KV,exact},Acc) -> erl_types:t_map_update(KV,Acc)
+			 end, ArgType1, TypePairs)}
+  end.
+
+bind_guard_map_pairs([], Map, _Env, _State, PairAcc) ->
+  {Map, lists:reverse(PairAcc)};
+bind_guard_map_pairs([Pair|Pairs], Map, Env, State, PairAcc) ->
+  Key = cerl:map_pair_key(Pair),
+  Val = cerl:map_pair_val(Pair),
+  Op = cerl:map_pair_op(Pair),
+  {Map1, [K,V]} = bind_guard_list([Key,Val],Map,Env,dont_know,State),
+  bind_guard_map_pairs(Pairs, Map1, Env, State,
+		       [{{K,V},cerl:concrete(Op)}|PairAcc]).
+
 -type eval() :: 'pos' | 'neg' | 'dont_know'.
 
 -spec signal_guard_fail(eval(), cerl:c_call(), [type()],
@@ -2421,7 +2573,9 @@ filter_fail_clauses([Clause|Left]) ->
   case (cerl:clause_pats(Clause) =:= []) of
     true ->
       Body = cerl:clause_body(Clause),
-      case cerl:is_literal(Body) andalso (cerl:concrete(Body) =:= fail) of
+      case cerl:is_literal(Body) andalso (cerl:concrete(Body) =:= fail) orelse
+	cerl:is_c_primop(Body) andalso
+	(cerl:atom_val(cerl:primop_name(Body)) =:= match_fail) of
 	true -> filter_fail_clauses(Left);
 	false -> [Clause|filter_fail_clauses(Left)]
       end;
@@ -2639,8 +2793,9 @@ store_map(Key, Val, #map{dict = Dict, ref = undefined} = Map) ->
 store_map(Key, Val, #map{dict = Dict, modified = Mod} = Map) ->
   Map#map{dict = dict:store(Key, Val, Dict), modified = [Key | Mod]}.
 
-enter_subst(Key, Val, #map{subst = Subst} = MS) ->
+enter_subst(Key, Val0, #map{subst = Subst} = MS) ->
   KeyLabel = get_label(Key),
+  Val = dialyzer_utils:refold_pattern(Val0),
   case cerl:is_literal(Val) of
     true ->
       store_map(KeyLabel, literal_type(Val), MS);
@@ -2703,6 +2858,9 @@ mark_as_fresh([Tree|Left], Map) ->
       bitstr ->
 	%% The Size field is not fresh.
 	{SubTrees1 -- [cerl:bitstr_size(Tree)], Map};
+      map_pair ->
+	%% The keys are not fresh
+	{SubTrees1 -- [cerl:map_pair_key(Tree)], Map};
       var ->
 	{SubTrees1, enter_type(Tree, t_any(), Map)};
       _ ->
diff --git a/lib/dialyzer/src/dialyzer_options.erl b/lib/dialyzer/src/dialyzer_options.erl
index dd81dd01ed..add660eae9 100644
--- a/lib/dialyzer/src/dialyzer_options.erl
+++ b/lib/dialyzer/src/dialyzer_options.erl
@@ -47,6 +47,7 @@ build(Opts) ->
 		  ?WARN_CALLGRAPH,
 		  ?WARN_FAILING_CALL,
 		  ?WARN_BIN_CONSTRUCTION,
+		  ?WARN_MAP_CONSTRUCTION,
 		  ?WARN_CONTRACT_RANGE,
 		  ?WARN_CONTRACT_TYPES,
 		  ?WARN_CONTRACT_SYNTAX,
diff --git a/lib/dialyzer/src/dialyzer_typesig.erl b/lib/dialyzer/src/dialyzer_typesig.erl
index 5f0881bbcd..50fcbc555b 100644
--- a/lib/dialyzer/src/dialyzer_typesig.erl
+++ b/lib/dialyzer/src/dialyzer_typesig.erl
@@ -48,6 +48,7 @@
 	 t_is_float/1, t_is_fun/1,
 	 t_is_integer/1, t_non_neg_integer/0,
 	 t_is_list/1, t_is_nil/1, t_is_none/1, t_is_number/1,
+	 t_is_singleton/1,
 
          t_limit/2, t_list/0, t_list/1,
 	 t_list_elements/1, t_nonempty_list/1, t_maybe_improper_list/0,
@@ -57,7 +58,7 @@
 	 t_timeout/0, t_tuple/0, t_tuple/1,
          t_var/1, t_var_name/1,
 	 t_none/0, t_unit/0,
-	 t_map/1
+	 t_map/0, t_map/1, t_map_get/2, t_map_put/2
      ]).
 
 -include("dialyzer.hrl").
@@ -126,6 +127,8 @@
                 solvers     = []                :: [solver()]
 	       }).
 
+-type state() :: #state{}.
+
 %%-----------------------------------------------------------------------------
 
 -define(TYPE_LIMIT, 4).
@@ -311,7 +314,7 @@ traverse(Tree, DefinedVars, State) ->
       Hd = cerl:cons_hd(Tree),
       Tl = cerl:cons_tl(Tree),
       {State1, [HdVar, TlVar]} = traverse_list([Hd, Tl], DefinedVars, State),
-      case cerl:is_literal(cerl:fold_literal(Tree)) of
+      case cerl:is_literal(fold_literal_maybe_match(Tree, State)) of
 	true ->
 	  %% We do not need to do anything more here.
 	  {State, t_cons(HdVar, TlVar)};
@@ -392,8 +395,18 @@ traverse(Tree, DefinedVars, State) ->
       {State2, _} = traverse_list(Funs, DefinedVars1, State1),
       traverse(Body, DefinedVars1, State2);
     literal ->
-      Type = t_from_term(cerl:concrete(Tree)),
-      {State, Type};
+      %% Maps are special; a literal pattern matches more than just the value
+      %% constructed by the literal. For example #{} constructs the empty map,
+      %% but matches every map.
+      case state__is_in_match(State) of
+	true ->
+	  Tree1 = dialyzer_utils:refold_pattern(Tree),
+	  case cerl:is_literal(Tree1) of
+	    false -> traverse(Tree1, DefinedVars, State);
+	    true -> {State, t_from_term(cerl:concrete(Tree))}
+	  end;
+	_ -> {State, t_from_term(cerl:concrete(Tree))}
+      end;
     module ->
       Defs = cerl:module_defs(Tree),
       Funs = [Fun || {_Var, Fun} <- Defs],
@@ -437,7 +450,7 @@ traverse(Tree, DefinedVars, State) ->
       Elements = cerl:tuple_es(Tree),
       {State1, EVars} = traverse_list(Elements, DefinedVars, State),
       {State2, TupleType} =
-	case cerl:is_literal(cerl:fold_literal(Tree)) of
+	case cerl:is_literal(fold_literal_maybe_match(Tree, State1)) of
 	  true ->
 	    %% We do not need to do anything more here.
 	    {State, t_tuple(EVars)};
@@ -476,7 +489,111 @@ traverse(Tree, DefinedVars, State) ->
 	[] -> {State2, TupleType}
       end;
     map ->
-	{State, t_map([])};
+      Entries = cerl:map_es(Tree),
+      MapFoldFun = fun(Entry, AccState) ->
+		       AccState1 = state__set_in_match(AccState, false),
+		       {AccState2, KeyVar} = traverse(cerl:map_pair_key(Entry),
+						      DefinedVars, AccState1),
+		       AccState3 = state__set_in_match(
+				     AccState2, state__is_in_match(AccState)),
+		       {AccState4, ValVar} = traverse(cerl:map_pair_val(Entry),
+						      DefinedVars, AccState3),
+		       {{KeyVar, ValVar}, AccState4}
+		   end,
+      {Pairs, State1} = lists:mapfoldl(MapFoldFun, State, Entries),
+      %% We mustn't recurse into map arguments to matches. Not only are they
+      %% syntactically only allowed to be the literal #{}, but that would also
+      %% cause an infinite recursion, since traverse/3 unfolds literals with
+      %% maps in them using dialyzer_utils:reflow_pattern/1.
+      {State2, ArgVar} =
+	case state__is_in_match(State) of
+	  false -> traverse(cerl:map_arg(Tree), DefinedVars, State1);
+	  true -> {State1, t_map()}
+	end,
+      MapVar = mk_var(Tree),
+      MapType = ?mk_fun_var(
+		   fun(Map) ->
+		       lists:foldl(
+			 fun({K,V}, TypeAcc) ->
+			     t_map_put({lookup_type(K, Map),
+					lookup_type(V, Map)},
+				       TypeAcc)
+			 end, t_inf(t_map(), lookup_type(ArgVar, Map)),
+			 Pairs)
+		   end, [ArgVar | lists:append([[K,V] || {K,V} <- Pairs])]),
+      %% TODO: does the "same element appearing several times" problem apply
+      %% here too?
+      Fun =
+	fun({KeyVar, ValVar}, {AccState, ShadowKeys}) ->
+	    %% If Val is known to be the last association of Key (i.e. Key
+	    %% is not in ShadowKeys), Val must be a subtype of what is
+	    %% associated to Key in Tree
+	    TypeFun =
+	      fun(Map) ->
+		  KeyType = lookup_type(KeyVar, Map),
+		  case t_is_singleton(KeyType) of
+		    false -> t_any();
+		    true ->
+		      MT = t_inf(lookup_type(MapVar, Map), t_map()),
+		      case t_is_none(MT) of
+			true -> t_none();
+			false ->
+			  DisjointFromKeyType =
+			    fun(ShadowKey) ->
+				t_is_none(t_inf(lookup_type(ShadowKey, Map),
+						KeyType))
+			    end,
+			  case lists:all(DisjointFromKeyType, ShadowKeys) of
+			    true -> t_map_get(KeyType, MT);
+			    %% A later association might shadow this one
+			    false -> t_any()
+			  end
+		      end
+		  end
+	      end,
+	    ValType = ?mk_fun_var(TypeFun, [KeyVar, MapVar | ShadowKeys]),
+	    {state__store_conj(ValVar, sub, ValType, AccState),
+	     [KeyVar | ShadowKeys]}
+	end,
+      %% Accumulate shadowing keys right-to-left
+      {State3, _} = lists:foldr(Fun, {State2, []}, Pairs),
+      %% In a map expression, Arg must contain all keys that are inserted with
+      %% the exact (:=) operator, and are known (i.e. are not in ShadowedKeys)
+      %% to not have been introduced by a previous association
+      State4 =
+	case state__is_in_match(State) of
+	  true -> State3;
+	  false ->
+	    ArgFun =
+	      fun(Map) ->
+		  FoldFun =
+		    fun({{KeyVar, _}, Entry}, {AccType, ShadowedKeys}) ->
+			OpTree = cerl:map_pair_op(Entry),
+			KeyType = lookup_type(KeyVar, Map),
+			AccType1 =
+			  case cerl:is_literal(OpTree) andalso
+			    cerl:concrete(OpTree) =:= exact of
+			    true ->
+			      case t_is_none(t_inf(ShadowedKeys, KeyType)) of
+				true ->
+				  t_map_put({KeyType, t_any()}, AccType);
+				false ->
+				  AccType
+			      end;
+			    false ->
+			      AccType
+			  end,
+			{AccType1, t_sup(KeyType, ShadowedKeys)}
+		    end,
+		  %% Accumulate shadowed keys left-to-right
+		  {ResType, _} = lists:foldl(FoldFun, {t_map(), t_none()},
+					     lists:zip(Pairs, Entries)),
+		  ResType
+	      end,
+	    ArgType = ?mk_fun_var(ArgFun, [KeyVar || {KeyVar, _} <- Pairs]),
+	    state__store_conj(ArgVar, sub, ArgType, State3)
+	end,
+      {state__store_conj(MapVar, sub, MapType, State4), MapVar};
     values ->
       %% We can get into trouble when unifying products that have the
       %% same element appearing several times. Handle these cases by
@@ -948,6 +1065,7 @@ get_type_test({erlang, is_float, 1}) ->     {ok, t_float()};
 get_type_test({erlang, is_function, 1}) ->  {ok, t_fun()};
 get_type_test({erlang, is_integer, 1}) ->   {ok, t_integer()};
 get_type_test({erlang, is_list, 1}) ->      {ok, t_list()};
+get_type_test({erlang, is_map, 1}) ->       {ok, t_map()};
 get_type_test({erlang, is_number, 1}) ->    {ok, t_number()};
 get_type_test({erlang, is_pid, 1}) ->       {ok, t_pid()};
 get_type_test({erlang, is_port, 1}) ->      {ok, t_port()};
@@ -1004,7 +1122,9 @@ bitstr_val_constr(SizeType, UnitVal, Flags) ->
       end
   end.
 
-get_safe_underapprox_1([Pat|Left], Acc, Map) ->
+get_safe_underapprox_1([Pat0|Left], Acc, Map) ->
+  %% Maps should be treated as patterns, not as literals
+  Pat = dialyzer_utils:refold_pattern(Pat0),
   case cerl:type(Pat) of
     alias ->
       APat = cerl:alias_pat(Pat),
@@ -1048,8 +1168,35 @@ get_safe_underapprox_1([Pat|Left], Acc, Map) ->
       Type = t_tuple(Ts),
       get_safe_underapprox_1(Left, [Type|Acc], Map1);
     map ->
-      %% TODO: Can maybe do something here
-      throw(dont_know);
+      %% Some assertions in case the syntax gets more premissive in the future
+      true = #{} =:= cerl:concrete(cerl:map_arg(Pat)),
+      true = lists:all(fun(P) ->
+			   cerl:is_literal(Op = cerl:map_pair_op(P)) andalso
+			     exact =:= cerl:concrete(Op)
+		       end, cerl:map_es(Pat)),
+      KeyTrees = lists:map(fun cerl:map_pair_key/1, cerl:map_es(Pat)),
+      ValTrees = lists:map(fun cerl:map_pair_val/1, cerl:map_es(Pat)),
+      %% Keys must not be underapproximated. Overapproximations are safe.
+      Keys = get_safe_overapprox(KeyTrees),
+      {Vals, Map1} = get_safe_underapprox_1(ValTrees, [], Map),
+      case lists:all(fun erl_types:t_is_singleton/1, Keys) of
+	false -> throw(dont_know);
+	true -> ok
+      end,
+      SortedPairs = lists:sort(lists:zip(Keys, Vals)),
+      %% We need to deal with duplicates ourselves
+      SquashDuplicates =
+	fun SquashDuplicates([{K,First},{K,Second}|List]) ->
+	    case t_is_none(Inf = t_inf(First, Second)) of
+	      true -> throw(dont_know);
+	      false -> [{K, Inf}|SquashDuplicates(List)]
+	    end;
+	    SquashDuplicates([Good|Rest]) ->
+	    [Good|SquashDuplicates(Rest)];
+	    SquashDuplicates([]) -> []
+	end,
+      Type = t_map(SquashDuplicates(SortedPairs)),
+      get_safe_underapprox_1(Left, [Type|Acc], Map1);
     values ->
       Es = cerl:values_es(Pat),
       {Ts, Map1} = get_safe_underapprox_1(Es, [], Map),
@@ -1064,6 +1211,15 @@ get_safe_underapprox_1([Pat|Left], Acc, Map) ->
 get_safe_underapprox_1([], Acc, Map) ->
   {lists:reverse(Acc), Map}.
 
+get_safe_overapprox(Pats) ->
+  lists:map(fun get_safe_overapprox_1/1, Pats).
+
+get_safe_overapprox_1(Pat) ->
+  case cerl:is_literal(Lit = cerl:fold_literal(Pat)) of
+    true  -> t_from_term(cerl:concrete(Lit));
+    false -> t_any()
+  end.
+
 %%----------------------------------------
 %% Guards
 %%
@@ -1263,6 +1419,8 @@ get_bif_constr({erlang, is_integer, 1}, Dst, [Arg], State) ->
   get_bif_test_constr(Dst, Arg, t_integer(), State);
 get_bif_constr({erlang, is_list, 1}, Dst, [Arg], State) ->
   get_bif_test_constr(Dst, Arg, t_maybe_improper_list(), State);
+get_bif_constr({erlang, is_map, 1}, Dst, [Arg], State) ->
+  get_bif_test_constr(Dst, Arg, t_map(), State);
 get_bif_constr({erlang, is_number, 1}, Dst, [Arg], State) ->
   get_bif_test_constr(Dst, Arg, t_number(), State);
 get_bif_constr({erlang, is_pid, 1}, Dst, [Arg], State) ->
@@ -1900,7 +2058,7 @@ sane_maps(Map1, Map2, Keys, _S1, _S2) ->
 %% Solver v2
 
 -record(v2_state, {constr_data = dict:new() :: dict:dict(),
-                   state :: #state{}}).
+		   state :: state()}).
 
 v2_solve_ref(Fun, Map, State) ->
   V2State = #v2_state{state = State},
@@ -2975,13 +3133,24 @@ mk_constraint_ref(Id, Deps) ->
 
 mk_constraint_list(Type, List) ->
   List1 = ordsets:from_list(lift_lists(Type, List)),
-  List2 = ordsets:filter(fun(X) -> get_deps(X) =/= [] end, List1),
-  Deps = calculate_deps(List2),
+  case Type of
+    conj ->
+      List2 = ordsets:filter(fun(X) -> get_deps(X) =/= [] end, List1),
+      mk_constraint_list_cont(Type, List2);
+    disj ->
+      case lists:any(fun(X) -> get_deps(X) =:= [] end, List1) of
+	true -> mk_constraint_list_cont(Type, [mk_constraint_any(eq)]);
+	false -> mk_constraint_list_cont(Type, List1)
+      end
+  end.
+
+mk_constraint_list_cont(Type, List) ->
+  Deps = calculate_deps(List),
   case Deps =:= [] of
     true -> #constraint_list{type = conj,
 			     list = [mk_constraint_any(eq)],
 			     deps = []};
-    false -> #constraint_list{type = Type, list = List2, deps = Deps}
+    false -> #constraint_list{type = Type, list = List, deps = Deps}
   end.
 
 lift_lists(Type, List) ->
@@ -3263,6 +3432,15 @@ find_constraint(Tuple, [#constraint_list{list = List}|Cs]) ->
 find_constraint(Tuple, [_|Cs]) ->
   find_constraint(Tuple, Cs).
 
+-spec fold_literal_maybe_match(cerl:cerl(), state()) -> cerl:cerl().
+
+fold_literal_maybe_match(Tree0, State) ->
+  Tree1 = cerl:fold_literal(Tree0),
+  case state__is_in_match(State) of
+    false -> Tree1;
+    true -> dialyzer_utils:refold_pattern(Tree1)
+  end.
+
 lookup_record(Records, Tag, Arity) ->
   case erl_types:lookup_record(Tag, Arity, Records) of
     {ok, Fields} ->
diff --git a/lib/dialyzer/src/dialyzer_utils.erl b/lib/dialyzer/src/dialyzer_utils.erl
index 5fc1c0e691..d37701f03b 100644
--- a/lib/dialyzer/src/dialyzer_utils.erl
+++ b/lib/dialyzer/src/dialyzer_utils.erl
@@ -49,6 +49,7 @@
 	 process_record_remote_types/1,
          sets_filter/2,
 	 src_compiler_opts/0,
+	 refold_pattern/1,
 	 parallelism/0,
          family/1
 	]).
@@ -752,6 +753,13 @@ pp_hook(Node, Ctxt, Cont) ->
       pp_binary(Node, Ctxt, Cont);
     bitstr ->
       pp_segment(Node, Ctxt, Cont);
+    map ->
+      pp_map(Node, Ctxt, Cont);
+    literal ->
+      case is_map(cerl:concrete(Node)) of
+	true -> pp_map(Node, Ctxt, Cont);
+	false -> Cont(Node, Ctxt)
+      end;
     _ ->
       Cont(Node, Ctxt)
   end.
@@ -832,6 +840,87 @@ pp_atom(Atom) ->
   String = atom_to_list(cerl:atom_val(Atom)),
   prettypr:text(String).
 
+pp_map(Node, Ctxt, Cont) ->
+  Arg = cerl:map_arg(Node),
+  Before = case cerl:is_c_map_empty(Arg) of
+	     true -> prettypr:floating(prettypr:text("#{"));
+	     false ->
+	       prettypr:beside(Cont(Arg,Ctxt),
+			       prettypr:floating(prettypr:text("#{")))
+	   end,
+  prettypr:beside(
+    Before, prettypr:beside(
+	      prettypr:par(seq(cerl:map_es(Node),
+			       prettypr:floating(prettypr:text(",")),
+			       Ctxt, Cont)),
+	      prettypr:floating(prettypr:text("}")))).
+
+seq([H | T], Separator, Ctxt, Fun) ->
+  case T of
+    [] -> [Fun(H, Ctxt)];
+    _  -> [prettypr:beside(Fun(H, Ctxt), Separator)
+	   | seq(T, Separator, Ctxt, Fun)]
+  end;
+seq([], _, _, _) ->
+  [prettypr:empty()].
+
+%%------------------------------------------------------------------------------
+
+-spec refold_pattern(cerl:cerl()) -> cerl:cerl().
+
+refold_pattern(Pat) ->
+  %% Avoid the churn of unfolding and refolding
+  case cerl:is_literal(Pat) andalso find_map(cerl:concrete(Pat)) of
+    true ->
+      Tree = refold_concrete_pat(cerl:concrete(Pat)),
+      PatAnn = cerl:get_ann(Pat),
+      case proplists:is_defined(label, PatAnn) of
+	%% Literals are not normally annotated with a label, but can be if, for
+	%% example, they were created by cerl:fold_literal/1.
+	true -> cerl:set_ann(Tree, PatAnn);
+	false ->
+	  [{label, Label}] = cerl:get_ann(Tree),
+	  cerl:set_ann(Tree, [{label, Label}|PatAnn])
+      end;
+    false -> Pat
+  end.
+
+find_map(#{}) -> true;
+find_map(Tuple) when is_tuple(Tuple) -> find_map(tuple_to_list(Tuple));
+find_map([H|T]) -> find_map(H) orelse find_map(T);
+find_map(_) -> false.
+
+refold_concrete_pat(Val) ->
+  case Val of
+    _ when is_tuple(Val) ->
+      Els = lists:map(fun refold_concrete_pat/1, tuple_to_list(Val)),
+      case lists:all(fun cerl:is_literal/1, Els) of
+	true -> cerl:abstract(Val);
+	false -> label(cerl:c_tuple_skel(Els))
+      end;
+    [H|T] ->
+      case  cerl:is_literal(HP=refold_concrete_pat(H))
+	and cerl:is_literal(TP=refold_concrete_pat(T))
+      of
+	true -> cerl:abstract(Val);
+	false -> label(cerl:c_cons_skel(HP, TP))
+      end;
+    M when is_map(M) ->
+      %% Map patterns are not generated by the parser(!), but they have a
+      %% property we want, namely that they are never folded into literals.
+      %% N.B.: The key in a map pattern is an expression, *not* a pattern.
+      label(cerl:c_map_pattern([cerl:c_map_pair_exact(cerl:abstract(K),
+						      refold_concrete_pat(V))
+				|| {K, V} <- maps:to_list(M)]));
+    _ ->
+      cerl:abstract(Val)
+  end.
+
+label(Tree) ->
+      %% Sigh
+      Label = -erlang:unique_integer([positive]),
+      cerl:set_ann(Tree, [{label, Label}]).
+
 %%------------------------------------------------------------------------------
 
 -spec parallelism() -> integer().
diff --git a/lib/dialyzer/test/behaviour_SUITE_data/results/supervisor_incorrect_return b/lib/dialyzer/test/behaviour_SUITE_data/results/supervisor_incorrect_return
index 89eb295604..638d031923 100644
--- a/lib/dialyzer/test/behaviour_SUITE_data/results/supervisor_incorrect_return
+++ b/lib/dialyzer/test/behaviour_SUITE_data/results/supervisor_incorrect_return
@@ -1,2 +1,2 @@
 
-supervisor_incorrect_return.erl:14: The inferred return type of init/1 ({'ok',{{'one_against_one',0,1},[{_,_,_,_,_,_},...]}}) has nothing in common with 'ignore' | {'ok',{{'one_for_all',non_neg_integer(),pos_integer()} | {'one_for_one',non_neg_integer(),pos_integer()} | {'rest_for_one',non_neg_integer(),pos_integer()} | {'simple_one_for_one',non_neg_integer(),pos_integer()} | #{},[{_,{atom(),atom(),'undefined' | [any()]},'permanent' | 'temporary' | 'transient','brutal_kill' | 'infinity' | non_neg_integer(),'supervisor' | 'worker','dynamic' | [atom()]} | #{}]}}, which is the expected return type for the callback of supervisor behaviour
+supervisor_incorrect_return.erl:14: The inferred return type of init/1 ({'ok',{{'one_against_one',0,1},[{_,_,_,_,_,_},...]}}) has nothing in common with 'ignore' | {'ok',{{'one_for_all',non_neg_integer(),pos_integer()} | {'one_for_one',non_neg_integer(),pos_integer()} | {'rest_for_one',non_neg_integer(),pos_integer()} | {'simple_one_for_one',non_neg_integer(),pos_integer()} | #{'intensity'=>non_neg_integer(), 'period'=>pos_integer(), 'strategy'=>'one_for_all' | 'one_for_one' | 'rest_for_one' | 'simple_one_for_one'},[{_,{atom(),atom(),'undefined' | [any()]},'permanent' | 'temporary' | 'transient','brutal_kill' | 'infinity' | non_neg_integer(),'supervisor' | 'worker','dynamic' | [atom()]} | #{'id':=_, 'start':={atom(),atom(),'undefined' | [any()]}, 'modules'=>'dynamic' | [atom()], 'restart'=>'permanent' | 'temporary' | 'transient', 'shutdown'=>'brutal_kill' | 'infinity' | non_neg_integer(), 'type'=>'supervisor' | 'worker'}]}}, which is the expected return type for the callback of supervisor behaviour
diff --git a/lib/dialyzer/test/map_SUITE_data/dialyzer_options b/lib/dialyzer/test/map_SUITE_data/dialyzer_options
new file mode 100644
index 0000000000..50991c9bc5
--- /dev/null
+++ b/lib/dialyzer/test/map_SUITE_data/dialyzer_options
@@ -0,0 +1 @@
+{dialyzer_options, []}.
diff --git a/lib/dialyzer/test/map_SUITE_data/results/bad_argument b/lib/dialyzer/test/map_SUITE_data/results/bad_argument
new file mode 100644
index 0000000000..af61a89638
--- /dev/null
+++ b/lib/dialyzer/test/map_SUITE_data/results/bad_argument
@@ -0,0 +1,5 @@
+
+bad_argument.erl:14: Function t3/0 has no local return
+bad_argument.erl:15: Guard test is_map('not_a_map') can never succeed
+bad_argument.erl:5: Function t/0 has no local return
+bad_argument.erl:6: A key of type 'b' cannot exist in a map of type #{'a':='q'}
diff --git a/lib/dialyzer/test/map_SUITE_data/results/contract b/lib/dialyzer/test/map_SUITE_data/results/contract
new file mode 100644
index 0000000000..0f6e1d0c65
--- /dev/null
+++ b/lib/dialyzer/test/map_SUITE_data/results/contract
@@ -0,0 +1,7 @@
+
+contract.erl:10: Function t2/0 has no local return
+contract.erl:10: The call missing:f(#{'a':=1, 'c':=4}) breaks the contract (#{'a':=1,'b'=>2,'c'=>3}) -> 'ok'
+contract.erl:12: Function t3/0 has no local return
+contract.erl:12: The call missing:f(#{'a':=1, 'b':=2, 'e':=3}) breaks the contract (#{'a':=1,'b'=>2,'c'=>3}) -> 'ok'
+contract.erl:8: Function t1/0 has no local return
+contract.erl:8: The call missing:f(#{'b':=2}) breaks the contract (#{'a':=1,'b'=>2,'c'=>3}) -> 'ok'
diff --git a/lib/dialyzer/test/map_SUITE_data/results/contract_violation b/lib/dialyzer/test/map_SUITE_data/results/contract_violation
new file mode 100644
index 0000000000..958321618f
--- /dev/null
+++ b/lib/dialyzer/test/map_SUITE_data/results/contract_violation
@@ -0,0 +1,3 @@
+
+contract_violation.erl:12: The pattern #{I:=Loc} can never match the type #{}
+contract_violation.erl:16: Invalid type specification for function contract_violation:beam_disasm_lines/2. The success typing is ('none' | <<_:32,_:_*8>>,_) -> #{pos_integer()=>{'location',_,_}}
diff --git a/lib/dialyzer/test/map_SUITE_data/results/exact b/lib/dialyzer/test/map_SUITE_data/results/exact
new file mode 100644
index 0000000000..374ada8869
--- /dev/null
+++ b/lib/dialyzer/test/map_SUITE_data/results/exact
@@ -0,0 +1,3 @@
+
+exact.erl:15: Function t2/1 has no local return
+exact.erl:19: The variable _ can never match since previous clauses completely covered the type #{'a':=_, ...}
diff --git a/lib/dialyzer/test/map_SUITE_data/results/guard_update b/lib/dialyzer/test/map_SUITE_data/results/guard_update
new file mode 100644
index 0000000000..e4bc892195
--- /dev/null
+++ b/lib/dialyzer/test/map_SUITE_data/results/guard_update
@@ -0,0 +1,5 @@
+
+guard_update.erl:5: Function t/0 has no local return
+guard_update.erl:6: The call guard_update:f(#{'a':=2}) will never return since it differs in the 1st argument from the success typing arguments: (#{'b':=_, ...})
+guard_update.erl:8: Clause guard cannot succeed. The variable M was matched against the type #{'a':=2}
+guard_update.erl:8: Function f/1 has no local return
diff --git a/lib/dialyzer/test/map_SUITE_data/results/initial_dataflow b/lib/dialyzer/test/map_SUITE_data/results/initial_dataflow
new file mode 100644
index 0000000000..69144f9208
--- /dev/null
+++ b/lib/dialyzer/test/map_SUITE_data/results/initial_dataflow
@@ -0,0 +1,4 @@
+
+initial_dataflow.erl:11: The variable Q can never match since previous clauses completely covered the type #{}
+initial_dataflow.erl:5: Function test/0 has no local return
+initial_dataflow.erl:6: The pattern 'false' can never match the type 'true'
diff --git a/lib/dialyzer/test/map_SUITE_data/results/is_map_guard b/lib/dialyzer/test/map_SUITE_data/results/is_map_guard
new file mode 100644
index 0000000000..6ab464d865
--- /dev/null
+++ b/lib/dialyzer/test/map_SUITE_data/results/is_map_guard
@@ -0,0 +1,5 @@
+
+is_map_guard.erl:13: Function t2/0 has no local return
+is_map_guard.erl:15: The call is_map_guard:explicit('still_not_map') will never return since it differs in the 1st argument from the success typing arguments: (map())
+is_map_guard.erl:6: Function t1/0 has no local return
+is_map_guard.erl:8: The call is_map_guard:implicit('not_a_map') will never return since it differs in the 1st argument from the success typing arguments: (map())
diff --git a/lib/dialyzer/test/map_SUITE_data/results/map_galore b/lib/dialyzer/test/map_SUITE_data/results/map_galore
new file mode 100644
index 0000000000..6ea88f01f8
--- /dev/null
+++ b/lib/dialyzer/test/map_SUITE_data/results/map_galore
@@ -0,0 +1,28 @@
+
+map_galore.erl:1000: A key of type 42 cannot exist in a map of type #{1:='a', 2:='b', 4:='d', 5:='e', float()=>'c' | 'v'}
+map_galore.erl:1080: A key of type 'nonexisting' cannot exist in a map of type #{#{'map':='key', 'one':='small'}:=[32 | 49 | 97 | 101 | 107 | 108 | 109 | 112 | 115 | 121,...], #{'map':='key', 'second':='small'}:=[32 | 50 | 97 | 101 | 107 | 108 | 109 | 112 | 115 | 121,...], #{'map':='key', 'third':='small'}:=[32 | 51 | 97 | 101 | 107 | 108 | 109 | 112 | 115 | 121,...], 10:='a0', 11:='a1', 12:='a2', 13:='a3', 14:='a4', 15:='a5', 16:='a6', 17:='a7', 18:='a8', 19:='a9', 20:='b0', 21:='b1', 22:='b2', 23:='b3', 24:='b4', 25:='b5', 26:='b6', 27:='b7', 28:='b8', 29:='b9', 30:=[48 | 99,...], 31:=[49 | 99,...], 32:=[50 | 99,...], 33:=[51 | 99,...], 34:=[52 | 99,...], 35:=[53 | 99,...], 36:=[54 | 99,...], 37:=[55 | 99,...], 38:=[56 | 99,...], 39:=[57 | 99,...], <<_:16>> | [48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57,...] | float() | {[[48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57,...],...]} | #{10:='a0', 11:='a1', 12:='a2', 13:='a3', 14:='a4', 15:='a5', 17:='a7', 18:='a8', 19:='a9', 20:='b0', 21:='b1', 22:='b2', 23:='b3', 24:='b4', 25:='b5', 27:='b7', 28:='b8', 29:='b9', 30:=[48 | 99,...], 31:=[49 | 99,...], 32:=[50 | 99,...], 33:=[51 | 99,...], 34:=[52 | 99,...], 35:=[53 | 99,...], 37:=[55 | 99,...], 38:=[56 | 99,...], 39:=[57 | 99,...], 'k16'=>'a6', 'k26'=>'b6', 'k36'=>[54 | 99,...], 16=>'a6', 26=>'b6', 36=>[54 | 99,...], <<_:16>> | [48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57,...] | {[[48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57,...],...]}=>[48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57 | 100 | 101,...]}=>atom() | [1..255,...]}
+map_galore.erl:1082: A key of type 42 cannot exist in a map of type #{#{'map':='key', 'one':='small'}:=[32 | 49 | 97 | 101 | 107 | 108 | 109 | 112 | 115 | 121,...], #{'map':='key', 'second':='small'}:=[32 | 50 | 97 | 101 | 107 | 108 | 109 | 112 | 115 | 121,...], #{'map':='key', 'third':='small'}:=[32 | 51 | 97 | 101 | 107 | 108 | 109 | 112 | 115 | 121,...], 10:='a0', 11:='a1', 12:='a2', 13:='a3', 14:='a4', 15:='a5', 16:='a6', 17:='a7', 18:='a8', 19:='a9', 20:='b0', 21:='b1', 22:='b2', 23:='b3', 24:='b4', 25:='b5', 26:='b6', 27:='b7', 28:='b8', 29:='b9', 30:=[48 | 99,...], 31:=[49 | 99,...], 32:=[50 | 99,...], 33:=[51 | 99,...], 34:=[52 | 99,...], 35:=[53 | 99,...], 36:=[54 | 99,...], 37:=[55 | 99,...], 38:=[56 | 99,...], 39:=[57 | 99,...], <<_:16>> | [48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57,...] | float() | {[[48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57,...],...]} | #{10:='a0', 11:='a1', 12:='a2', 13:='a3', 14:='a4', 15:='a5', 17:='a7', 18:='a8', 19:='a9', 20:='b0', 21:='b1', 22:='b2', 23:='b3', 24:='b4', 25:='b5', 27:='b7', 28:='b8', 29:='b9', 30:=[48 | 99,...], 31:=[49 | 99,...], 32:=[50 | 99,...], 33:=[51 | 99,...], 34:=[52 | 99,...], 35:=[53 | 99,...], 37:=[55 | 99,...], 38:=[56 | 99,...], 39:=[57 | 99,...], 'k16'=>'a6', 'k26'=>'b6', 'k36'=>[54 | 99,...], 16=>'a6', 26=>'b6', 36=>[54 | 99,...], <<_:16>> | [48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57,...] | {[[48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57,...],...]}=>[48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57 | 100 | 101,...]}=>atom() | [1..255,...]}
+map_galore.erl:1140: The call map_galore:map_guard_sequence_1(#{'seq':=6, 'val':=[101,...]}) will never return since it differs in the 1st argument from the success typing arguments: (#{'seq':=1 | 2 | 3 | 4 | 5, 'val':=[97 | 98 | 99 | 100 | 101,...], #{'map':='key', 'one':='small'}=>[32 | 49 | 97 | 101 | 107 | 108 | 109 | 112 | 115 | 121,...], #{'map':='key', 'second':='small'}=>[32 | 50 | 97 | 101 | 107 | 108 | 109 | 112 | 115 | 121,...], #{'map':='key', 'third':='small'}=>[32 | 51 | 97 | 101 | 107 | 108 | 109 | 112 | 115 | 121,...], 10=>'a0', 11=>'a1', 12=>'a2', 13=>'a3', 14=>'a4', 15=>'a5', 16=>'a6', 17=>'a7', 18=>'a8', 19=>'a9', 20=>'b0', 21=>'b1', 22=>'b2', 23=>'b3', 24=>'b4', 25=>'b5', 26=>'b6', 27=>'b7', 28=>'b8', 29=>'b9', 30=>[48 | 99,...], 31=>[49 | 99,...], 32=>[50 | 99,...], 33=>[51 | 99,...], 34=>[52 | 99,...], 35=>[53 | 99,...], 36=>[54 | 99,...], 37=>[55 | 99,...], 38=>[56 | 99,...], 39=>[57 | 99,...], <<_:16>> | [48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57,...] | float() | {[any(),...]} | #{10:='a0', 11:='a1', 12:='a2', 13:='a3', 14:='a4', 15:='a5', 17:='a7', 18:='a8', 19:='a9', 20:='b0', 21:='b1', 22:='b2', 23:='b3', 24:='b4', 25:='b5', 27:='b7', 28:='b8', 29:='b9', 30:=[any(),...], 31:=[any(),...], 32:=[any(),...], 33:=[any(),...], 34:=[any(),...], 35:=[any(),...], 37:=[any(),...], 38:=[any(),...], 39:=[any(),...], 'k16'=>'a6', 'k26'=>'b6', 'k36'=>[any(),...], 16=>'a6', 26=>'b6', 36=>[any(),...], <<_:16>> | [any(),...] | {_}=>[any(),...]}=>atom() | [1..255,...]})
+map_galore.erl:1141: The call map_galore:map_guard_sequence_2(#{'b':=5}) will never return since it differs in the 1st argument from the success typing arguments: (#{'a':='gg' | 'kk' | 'sc' | 3 | 4, 'b'=>'other' | 3 | 4 | 5, 'c'=>'sc2', #{'map':='key', 'one':='small'}=>[32 | 49 | 97 | 101 | 107 | 108 | 109 | 112 | 115 | 121,...], #{'map':='key', 'second':='small'}=>[32 | 50 | 97 | 101 | 107 | 108 | 109 | 112 | 115 | 121,...], #{'map':='key', 'third':='small'}=>[32 | 51 | 97 | 101 | 107 | 108 | 109 | 112 | 115 | 121,...], 10=>'a0', 11=>'a1', 12=>'a2', 13=>'a3', 14=>'a4', 15=>'a5', 16=>'a6', 17=>'a7', 18=>'a8', 19=>'a9', 20=>'b0', 21=>'b1', 22=>'b2', 23=>'b3', 24=>'b4', 25=>'b5', 26=>'b6', 27=>'b7', 28=>'b8', 29=>'b9', 30=>[48 | 99,...], 31=>[49 | 99,...], 32=>[50 | 99,...], 33=>[51 | 99,...], 34=>[52 | 99,...], 35=>[53 | 99,...], 36=>[54 | 99,...], 37=>[55 | 99,...], 38=>[56 | 99,...], 39=>[57 | 99,...], <<_:16>> | [48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57,...] | float() | {[any(),...]} | #{10:='a0', 11:='a1', 12:='a2', 13:='a3', 14:='a4', 15:='a5', 17:='a7', 18:='a8', 19:='a9', 20:='b0', 21:='b1', 22:='b2', 23:='b3', 24:='b4', 25:='b5', 27:='b7', 28:='b8', 29:='b9', 30:=[any(),...], 31:=[any(),...], 32:=[any(),...], 33:=[any(),...], 34:=[any(),...], 35:=[any(),...], 37:=[any(),...], 38:=[any(),...], 39:=[any(),...], 'k16'=>'a6', 'k26'=>'b6', 'k36'=>[any(),...], 16=>'a6', 26=>'b6', 36=>[any(),...], <<_:16>> | [any(),...] | {_}=>[any(),...]}=>atom() | [1..255,...]})
+map_galore.erl:1209: The call map_galore:map_guard_sequence_1(#{'seq':=6, 'val':=[101,...], #{'map':='key', 'one':='small'}:=[32 | 49 | 97 | 101 | 107 | 108 | 109 | 112 | 115 | 121,...], #{'map':='key', 'second':='small'}:=[32 | 50 | 97 | 101 | 107 | 108 | 109 | 112 | 115 | 121,...], #{'map':='key', 'third':='small'}:=[32 | 51 | 97 | 101 | 107 | 108 | 109 | 112 | 115 | 121,...], 10:='a0', 11:='a1', 12:='a2', 13:='a3', 14:='a4', 15:='a5', 16:='a6', 17:='a7', 18:='a8', 19:='a9', 20:='b0', 21:='b1', 22:='b2', 23:='b3', 24:='b4', 25:='b5', 26:='b6', 27:='b7', 28:='b8', 29:='b9', 30:=[48 | 99,...], 31:=[49 | 99,...], 32:=[50 | 99,...], 33:=[51 | 99,...], 34:=[52 | 99,...], 35:=[53 | 99,...], 36:=[54 | 99,...], 37:=[55 | 99,...], 38:=[56 | 99,...], 39:=[57 | 99,...], <<_:16>> | [48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57,...] | float() | {[[48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57,...] | 3,...]} | #{10:='a0', 11:='a1', 12:='a2', 13:='a3', 14:='a4', 15:='a5', 17:='a7', 18:='a8', 19:='a9', 20:='b0', 21:='b1', 22:='b2', 23:='b3', 24:='b4', 25:='b5', 27:='b7', 28:='b8', 29:='b9', 30:=[48 | 99,...], 31:=[49 | 99,...], 32:=[50 | 99,...], 33:=[51 | 99,...], 34:=[52 | 99,...], 35:=[53 | 99,...], 37:=[55 | 99,...], 38:=[56 | 99,...], 39:=[57 | 99,...], 'k16'=>'a6', 'k26'=>'b6', 'k36'=>[54 | 99,...], 16=>'a6', 26=>'b6', 36=>[54 | 99,...], <<_:16>> | [48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57,...] | {[[48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57,...],...]}=>[48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57 | 100 | 101,...]}=>atom() | [1..255,...]}) will never return since it differs in the 1st argument from the success typing arguments: (#{'seq':=1 | 2 | 3 | 4 | 5, 'val':=[97 | 98 | 99 | 100 | 101,...], #{'map':='key', 'one':='small'}=>[32 | 49 | 97 | 101 | 107 | 108 | 109 | 112 | 115 | 121,...], #{'map':='key', 'second':='small'}=>[32 | 50 | 97 | 101 | 107 | 108 | 109 | 112 | 115 | 121,...], #{'map':='key', 'third':='small'}=>[32 | 51 | 97 | 101 | 107 | 108 | 109 | 112 | 115 | 121,...], 10=>'a0', 11=>'a1', 12=>'a2', 13=>'a3', 14=>'a4', 15=>'a5', 16=>'a6', 17=>'a7', 18=>'a8', 19=>'a9', 20=>'b0', 21=>'b1', 22=>'b2', 23=>'b3', 24=>'b4', 25=>'b5', 26=>'b6', 27=>'b7', 28=>'b8', 29=>'b9', 30=>[48 | 99,...], 31=>[49 | 99,...], 32=>[50 | 99,...], 33=>[51 | 99,...], 34=>[52 | 99,...], 35=>[53 | 99,...], 36=>[54 | 99,...], 37=>[55 | 99,...], 38=>[56 | 99,...], 39=>[57 | 99,...], <<_:16>> | [48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57,...] | float() | {[any(),...]} | #{10:='a0', 11:='a1', 12:='a2', 13:='a3', 14:='a4', 15:='a5', 17:='a7', 18:='a8', 19:='a9', 20:='b0', 21:='b1', 22:='b2', 23:='b3', 24:='b4', 25:='b5', 27:='b7', 28:='b8', 29:='b9', 30:=[any(),...], 31:=[any(),...], 32:=[any(),...], 33:=[any(),...], 34:=[any(),...], 35:=[any(),...], 37:=[any(),...], 38:=[any(),...], 39:=[any(),...], 'k16'=>'a6', 'k26'=>'b6', 'k36'=>[any(),...], 16=>'a6', 26=>'b6', 36=>[any(),...], <<_:16>> | [any(),...] | {_}=>[any(),...]}=>atom() | [1..255,...]})
+map_galore.erl:1210: The call map_galore:map_guard_sequence_2(#{'b':=5, #{'map':='key', 'one':='small'}:=[32 | 49 | 97 | 101 | 107 | 108 | 109 | 112 | 115 | 121,...], #{'map':='key', 'second':='small'}:=[32 | 50 | 97 | 101 | 107 | 108 | 109 | 112 | 115 | 121,...], #{'map':='key', 'third':='small'}:=[32 | 51 | 97 | 101 | 107 | 108 | 109 | 112 | 115 | 121,...], 10:='a0', 11:='a1', 12:='a2', 13:='a3', 14:='a4', 15:='a5', 16:='a6', 17:='a7', 18:='a8', 19:='a9', 20:='b0', 21:='b1', 22:='b2', 23:='b3', 24:='b4', 25:='b5', 26:='b6', 27:='b7', 28:='b8', 29:='b9', 30:=[48 | 99,...], 31:=[49 | 99,...], 32:=[50 | 99,...], 33:=[51 | 99,...], 34:=[52 | 99,...], 35:=[53 | 99,...], 36:=[54 | 99,...], 37:=[55 | 99,...], 38:=[56 | 99,...], 39:=[57 | 99,...], <<_:16>> | [48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57,...] | float() | {[[48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57,...] | 3,...]} | #{10:='a0', 11:='a1', 12:='a2', 13:='a3', 14:='a4', 15:='a5', 17:='a7', 18:='a8', 19:='a9', 20:='b0', 21:='b1', 22:='b2', 23:='b3', 24:='b4', 25:='b5', 27:='b7', 28:='b8', 29:='b9', 30:=[48 | 99,...], 31:=[49 | 99,...], 32:=[50 | 99,...], 33:=[51 | 99,...], 34:=[52 | 99,...], 35:=[53 | 99,...], 37:=[55 | 99,...], 38:=[56 | 99,...], 39:=[57 | 99,...], 'k16'=>'a6', 'k26'=>'b6', 'k36'=>[54 | 99,...], 16=>'a6', 26=>'b6', 36=>[54 | 99,...], <<_:16>> | [48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57,...] | {[[48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57,...],...]}=>[48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57 | 100 | 101,...]}=>atom() | [1..255,...]}) will never return since it differs in the 1st argument from the success typing arguments: (#{'a':='gg' | 'kk' | 'sc' | 3 | 4, 'b'=>'other' | 3 | 4 | 5, 'c'=>'sc2', #{'map':='key', 'one':='small'}=>[32 | 49 | 97 | 101 | 107 | 108 | 109 | 112 | 115 | 121,...], #{'map':='key', 'second':='small'}=>[32 | 50 | 97 | 101 | 107 | 108 | 109 | 112 | 115 | 121,...], #{'map':='key', 'third':='small'}=>[32 | 51 | 97 | 101 | 107 | 108 | 109 | 112 | 115 | 121,...], 10=>'a0', 11=>'a1', 12=>'a2', 13=>'a3', 14=>'a4', 15=>'a5', 16=>'a6', 17=>'a7', 18=>'a8', 19=>'a9', 20=>'b0', 21=>'b1', 22=>'b2', 23=>'b3', 24=>'b4', 25=>'b5', 26=>'b6', 27=>'b7', 28=>'b8', 29=>'b9', 30=>[48 | 99,...], 31=>[49 | 99,...], 32=>[50 | 99,...], 33=>[51 | 99,...], 34=>[52 | 99,...], 35=>[53 | 99,...], 36=>[54 | 99,...], 37=>[55 | 99,...], 38=>[56 | 99,...], 39=>[57 | 99,...], <<_:16>> | [48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57,...] | float() | {[any(),...]} | #{10:='a0', 11:='a1', 12:='a2', 13:='a3', 14:='a4', 15:='a5', 17:='a7', 18:='a8', 19:='a9', 20:='b0', 21:='b1', 22:='b2', 23:='b3', 24:='b4', 25:='b5', 27:='b7', 28:='b8', 29:='b9', 30:=[any(),...], 31:=[any(),...], 32:=[any(),...], 33:=[any(),...], 34:=[any(),...], 35:=[any(),...], 37:=[any(),...], 38:=[any(),...], 39:=[any(),...], 'k16'=>'a6', 'k26'=>'b6', 'k36'=>[any(),...], 16=>'a6', 26=>'b6', 36=>[any(),...], <<_:16>> | [any(),...] | {_}=>[any(),...]}=>atom() | [1..255,...]})
+map_galore.erl:1418: Fun application with arguments (#{'s':='none', 'v':='none'}) will never return since it differs in the 1st argument from the success typing arguments: (#{'s':='l' | 't' | 'v', 'v':='none' | <<_:16>> | [<<_:16>>,...] | {<<_:16>>,<<_:16>>}})
+map_galore.erl:1491: The test #{} =:= #{'a':=1} can never evaluate to 'true'
+map_galore.erl:1492: The test #{'a':=1} =:= #{} can never evaluate to 'true'
+map_galore.erl:1495: The test #{'a':=1} =:= #{'a':=2} can never evaluate to 'true'
+map_galore.erl:1496: The test #{'a':=2} =:= #{'a':=1} can never evaluate to 'true'
+map_galore.erl:1497: The test #{'a':=2, 'b':=1} =:= #{'a':=1, 'b':=3} can never evaluate to 'true'
+map_galore.erl:1498: The test #{'a':=1, 'b':=1} =:= #{'a':=1, 'b':=3} can never evaluate to 'true'
+map_galore.erl:1762: The call maps:get({1, 1},#{{1,float()}=>[101 | 108 | 112 | 116 | 117,...]}) will never return since the success typing arguments are (any(),map())
+map_galore.erl:1763: The call maps:get('a',#{}) will never return since the success typing arguments are (any(),map())
+map_galore.erl:1765: The call maps:get('a',#{'b':=1, 'c':=2}) will never return since the success typing arguments are (any(),map())
+map_galore.erl:186: The pattern #{'x':=2} can never match the type #{'x':=3}
+map_galore.erl:187: The pattern #{'x':=3} can never match the type {'a','b','c'}
+map_galore.erl:188: The pattern #{'x':=3} can never match the type #{'y':=3}
+map_galore.erl:189: The pattern #{'x':=3} can never match the type #{'x':=[101 | 104 | 114 | 116,...]}
+map_galore.erl:2304: Cons will produce an improper list since its 2nd argument is {'b','a'}
+map_galore.erl:2304: The call maps:from_list(nonempty_improper_list({'a','b'},{'b','a'})) will never return since it differs in the 1st argument from the success typing arguments: ([{_,_}])
+map_galore.erl:2305: The call maps:from_list('a') will never return since it differs in the 1st argument from the success typing arguments: ([{_,_}])
+map_galore.erl:2306: The call maps:from_list(42) will never return since it differs in the 1st argument from the success typing arguments: ([{_,_}])
+map_galore.erl:997: A key of type 'nonexisting' cannot exist in a map of type #{}
+map_galore.erl:998: A key of type 'nonexisting' cannot exist in a map of type #{1:='a', 2:='b', 4:='d', 5:='e', float()=>'c'}
diff --git a/lib/dialyzer/test/map_SUITE_data/results/map_in_guard b/lib/dialyzer/test/map_SUITE_data/results/map_in_guard
new file mode 100644
index 0000000000..1015f76128
--- /dev/null
+++ b/lib/dialyzer/test/map_SUITE_data/results/map_in_guard
@@ -0,0 +1,4 @@
+
+map_in_guard.erl:10: The call map_in_guard:assoc_update('not_a_map') will never return since it differs in the 1st argument from the success typing arguments: (#{})
+map_in_guard.erl:13: The call map_in_guard:assoc_guard_clause('not_a_map') will never return since it differs in the 1st argument from the success typing arguments: (#{})
+map_in_guard.erl:20: The call map_in_guard:exact_guard_clause(#{}) will never return since it differs in the 1st argument from the success typing arguments: (#{'a':='q'})
diff --git a/lib/dialyzer/test/map_SUITE_data/results/map_in_guard2 b/lib/dialyzer/test/map_SUITE_data/results/map_in_guard2
new file mode 100644
index 0000000000..6bc0c010d7
--- /dev/null
+++ b/lib/dialyzer/test/map_SUITE_data/results/map_in_guard2
@@ -0,0 +1,13 @@
+
+map_in_guard2.erl:10: The call map_in_guard2:assoc_guard_clause('not_a_map') will never return since it differs in the 1st argument from the success typing arguments: (map())
+map_in_guard2.erl:12: The pattern 'true' can never match the type 'false'
+map_in_guard2.erl:14: The call map_in_guard2:exact_guard_clause(#{}) will never return since it differs in the 1st argument from the success typing arguments: (#{'a':=_, ...})
+map_in_guard2.erl:17: Clause guard cannot succeed. The variable M was matched against the type 'not_a_map'
+map_in_guard2.erl:20: Function assoc_update/1 has no local return
+map_in_guard2.erl:20: Guard test is_map(M::'not_a_map') can never succeed
+map_in_guard2.erl:22: Clause guard cannot succeed. The variable M was matched against the type 'not_a_map'
+map_in_guard2.erl:22: Function assoc_guard_clause/1 has no local return
+map_in_guard2.erl:24: Clause guard cannot succeed. The variable M was matched against the type #{}
+map_in_guard2.erl:27: Clause guard cannot succeed. The variable M was matched against the type #{}
+map_in_guard2.erl:27: Function exact_guard_clause/1 has no local return
+map_in_guard2.erl:8: The call map_in_guard2:assoc_update('not_a_map') will never return since it differs in the 1st argument from the success typing arguments: (map())
diff --git a/lib/dialyzer/test/map_SUITE_data/results/map_size b/lib/dialyzer/test/map_SUITE_data/results/map_size
new file mode 100644
index 0000000000..fc6c1f028c
--- /dev/null
+++ b/lib/dialyzer/test/map_SUITE_data/results/map_size
@@ -0,0 +1,13 @@
+
+map_size.erl:11: The pattern 1 can never match the type 0
+map_size.erl:13: Function t2/0 has no local return
+map_size.erl:15: Function p/1 has no local return
+map_size.erl:15: Guard test 1 =:= 0 can never succeed
+map_size.erl:17: Function t3/0 has no local return
+map_size.erl:21: The pattern 4 can never match the type 1 | 2 | 3
+map_size.erl:23: Function t4/0 has no local return
+map_size.erl:24: The pattern 0 can never match the type 1 | 2 | 3
+map_size.erl:26: Function t5/1 has no local return
+map_size.erl:5: Function t1/0 has no local return
+map_size.erl:7: The pattern 1 can never match the type 0
+map_size.erl:9: Function e1/0 has no local return
diff --git a/lib/dialyzer/test/map_SUITE_data/results/maps_merge b/lib/dialyzer/test/map_SUITE_data/results/maps_merge
new file mode 100644
index 0000000000..0c347b4cdb
--- /dev/null
+++ b/lib/dialyzer/test/map_SUITE_data/results/maps_merge
@@ -0,0 +1,11 @@
+
+maps_merge.erl:10: The pattern #{_:=_} can never match the type #{'a':=1, 3:='ok', 'q'=>none(), 7=>none(), atom() | integer()=>_}
+maps_merge.erl:12: Function t3/0 has no local return
+maps_merge.erl:14: The pattern #{7:='q'} can never match the type #{'a':=1, 3:='ok', 'q'=>none(), 7=>none(), atom() | integer()=>_}
+maps_merge.erl:16: Function t4/0 has no local return
+maps_merge.erl:18: The pattern #{7:='q'} can never match the type #{'a':=1, 3:='ok', 'q'=>none(), 7=>none(), atom() | integer()=>_}
+maps_merge.erl:20: Function t5/0 has no local return
+maps_merge.erl:21: The pattern #{'a':=2} can never match the type #{'a':=1, 'q'=>none(), 11=>_, atom()=>_}
+maps_merge.erl:5: Function t1/0 has no local return
+maps_merge.erl:6: The pattern #{'a':=1} can never match the type #{}
+maps_merge.erl:8: Function t2/0 has no local return
diff --git a/lib/dialyzer/test/map_SUITE_data/results/opaque_key b/lib/dialyzer/test/map_SUITE_data/results/opaque_key
new file mode 100644
index 0000000000..fb7080cdc5
--- /dev/null
+++ b/lib/dialyzer/test/map_SUITE_data/results/opaque_key
@@ -0,0 +1,15 @@
+
+opaque_key_adt.erl:41: Invalid type specification for function opaque_key_adt:s4/0. The success typing is () -> #{1:='a'}
+opaque_key_adt.erl:44: Invalid type specification for function opaque_key_adt:s5/0. The success typing is () -> #{2:=3}
+opaque_key_adt.erl:56: Invalid type specification for function opaque_key_adt:smt1/0. The success typing is () -> #{3:='a'}
+opaque_key_adt.erl:59: Invalid type specification for function opaque_key_adt:smt2/0. The success typing is () -> #{1:='a'}
+opaque_key_use.erl:13: The test opaque_key_use:t() =:= opaque_key_use:t(integer()) can never evaluate to 'true'
+opaque_key_use.erl:24: Attempt to test for equality between a term of type opaque_key_adt:t(integer()) and a term of opaque type opaque_key_adt:t()
+opaque_key_use.erl:37: Function adt_mm1/0 has no local return
+opaque_key_use.erl:40: The attempt to match a term of type opaque_key_adt:m() against the pattern #{A:=R} breaks the opaqueness of the term
+opaque_key_use.erl:48: Function adt_mu1/0 has no local return
+opaque_key_use.erl:51: Guard test is_map(M::opaque_key_adt:m()) breaks the opaqueness of its argument
+opaque_key_use.erl:53: Function adt_mu2/0 has no local return
+opaque_key_use.erl:56: Guard test is_map(M::opaque_key_adt:m()) breaks the opaqueness of its argument
+opaque_key_use.erl:58: Function adt_mu3/0 has no local return
+opaque_key_use.erl:60: Guard test is_map(M::opaque_key_adt:m()) breaks the opaqueness of its argument
diff --git a/lib/dialyzer/test/map_SUITE_data/results/order b/lib/dialyzer/test/map_SUITE_data/results/order
new file mode 100644
index 0000000000..7be789a11a
--- /dev/null
+++ b/lib/dialyzer/test/map_SUITE_data/results/order
@@ -0,0 +1,17 @@
+
+order.erl:12: Function t2/0 has no local return
+order.erl:14: Guard test is_integer(Int::'b') can never succeed
+order.erl:16: The variable _Else can never match since previous clauses completely covered the type 'b'
+order.erl:19: Function t3/0 has no local return
+order.erl:21: Guard test is_integer(Int::'b') can never succeed
+order.erl:23: The variable _Else can never match since previous clauses completely covered the type 'b'
+order.erl:30: The variable _Else can never match since previous clauses completely covered the type 'b' | 1
+order.erl:33: Function t5/0 has no local return
+order.erl:36: The variable Atom can never match since previous clauses completely covered the type 1
+order.erl:37: The variable _Else can never match since previous clauses completely covered the type 1
+order.erl:40: Function t6/0 has no local return
+order.erl:42: Guard test is_integer(Int::'b') can never succeed
+order.erl:44: The variable _Else can never match since previous clauses completely covered the type 'b'
+order.erl:5: Function t1/0 has no local return
+order.erl:7: Guard test is_integer(Int::'b') can never succeed
+order.erl:9: The variable _Else can never match since previous clauses completely covered the type 'b'
diff --git a/lib/dialyzer/test/map_SUITE_data/results/subtract_value_flip b/lib/dialyzer/test/map_SUITE_data/results/subtract_value_flip
new file mode 100644
index 0000000000..e69de29bb2
--- /dev/null
+++ b/lib/dialyzer/test/map_SUITE_data/results/subtract_value_flip
diff --git a/lib/dialyzer/test/map_SUITE_data/results/typeflow b/lib/dialyzer/test/map_SUITE_data/results/typeflow
new file mode 100644
index 0000000000..e3378a24bb
--- /dev/null
+++ b/lib/dialyzer/test/map_SUITE_data/results/typeflow
@@ -0,0 +1,4 @@
+
+typeflow.erl:14: Function t2/1 has no local return
+typeflow.erl:16: The call lists:sort(integer()) will never return since it differs in the 1st argument from the success typing arguments: ([any()])
+typeflow.erl:9: The variable _ can never match since previous clauses completely covered the type #{'a':=integer(), ...}
diff --git a/lib/dialyzer/test/map_SUITE_data/results/typeflow2 b/lib/dialyzer/test/map_SUITE_data/results/typeflow2
new file mode 100644
index 0000000000..3adf638978
--- /dev/null
+++ b/lib/dialyzer/test/map_SUITE_data/results/typeflow2
@@ -0,0 +1,13 @@
+
+typeflow2.erl:10: The pattern #{'a':=X} can never match the type #{'a'=>none(), _=>maybe_improper_list() | integer()}
+typeflow2.erl:11: The pattern #{'a':=X} can never match the type #{'a'=>none(), _=>maybe_improper_list() | integer()}
+typeflow2.erl:26: Function t2/1 has no local return
+typeflow2.erl:29: The call lists:sort(integer()) will never return since it differs in the 1st argument from the success typing arguments: ([any()])
+typeflow2.erl:42: The pattern #{'a':=X} can never match since previous clauses completely covered the type #{'a':=integer()}
+typeflow2.erl:43: The variable _ can never match since previous clauses completely covered the type #{'a':=integer()}
+typeflow2.erl:48: The pattern #{} can never match since previous clauses completely covered the type #{'a':=atom() | maybe_improper_list() | integer()}
+typeflow2.erl:58: The pattern #{'a':=X} can never match the type #{'a'=>none(), _=>maybe_improper_list() | integer()}
+typeflow2.erl:59: The pattern #{'a':=X} can never match the type #{'a'=>none(), _=>maybe_improper_list() | integer()}
+typeflow2.erl:60: The pattern #{'a':=X} can never match the type #{'a'=>none(), _=>maybe_improper_list() | integer()}
+typeflow2.erl:82: The pattern #{'a':=X} can never match the type #{}
+typeflow2.erl:83: The pattern #{'a':=X} can never match the type #{}
diff --git a/lib/dialyzer/test/map_SUITE_data/results/typesig b/lib/dialyzer/test/map_SUITE_data/results/typesig
new file mode 100644
index 0000000000..3049402860
--- /dev/null
+++ b/lib/dialyzer/test/map_SUITE_data/results/typesig
@@ -0,0 +1,5 @@
+
+typesig.erl:5: Function t1/0 has no local return
+typesig.erl:5: The call typesig:test(#{'a':=1}) will never return since it differs in the 1st argument from the success typing arguments: (#{'a':={number()}, ...})
+typesig.erl:6: Function t2/0 has no local return
+typesig.erl:6: The call typesig:test(#{'a':={'b'}}) will never return since it differs in the 1st argument from the success typing arguments: (#{'a':={number()}, ...})
diff --git a/lib/dialyzer/test/map_SUITE_data/src/bad_argument.erl b/lib/dialyzer/test/map_SUITE_data/src/bad_argument.erl
new file mode 100644
index 0000000000..95e2b32ddc
--- /dev/null
+++ b/lib/dialyzer/test/map_SUITE_data/src/bad_argument.erl
@@ -0,0 +1,19 @@
+-module(bad_argument).
+
+-export([t/0, t2/0, t3/0]).
+
+t() ->
+    _=(id1(#{a=>q}))#{b:=9}.
+
+t2() ->
+    _ = id2(4),
+    X = id2(3),
+    _ = (#{ X => q})#{3 := p},
+    X.
+
+t3() ->
+    (id3(not_a_map))#{a => b}.
+
+id1(X) -> X.
+id2(X) -> X.
+id3(X) -> X.
diff --git a/lib/dialyzer/test/map_SUITE_data/src/bug.erl b/lib/dialyzer/test/map_SUITE_data/src/bug.erl
new file mode 100644
index 0000000000..fc32f5641a
--- /dev/null
+++ b/lib/dialyzer/test/map_SUITE_data/src/bug.erl
@@ -0,0 +1,63 @@
+-module(bug).
+
+-export([t1/0, f1/1
+	,t2/0, f2/1
+	,t3/0, f3/1
+	,t4/0, f4/1
+	,t5/0, f5/1
+	]).
+
+t1() ->
+    V = f1(#{a=>b}),
+    case V of
+	#{a := Q} -> Q; %% Must not warn here
+	_ -> ok
+    end,
+    ok.
+
+f1(M) -> %% Should get map() succ typing
+    #{} = M.
+
+t2() ->
+    V = f2([#{a=>b}]),
+    case V of
+	[#{a := P}] -> P; %% Must not warn here
+	_ -> ok
+    end,
+    ok.
+
+f2(M) -> %% Should get [map(),...] succ typing
+    [#{}] = M.
+
+t3() ->
+    V = f3([#{a=>b},a]),
+    case V of
+	[#{a := P}, _Q] -> P; %% Must not warn here
+	_ -> ok
+    end,
+    ok.
+
+f3(M) -> %% Should get [map()|a,...] succ typing
+    [#{},a] = M.
+
+t4() ->
+    V = f4({#{a=>b},{}}),
+    case V of
+	{#{a := P},{}} -> P; %% Must not warn here
+	_ -> ok
+    end,
+    ok.
+
+f4(M) -> %% Should get {map(),{}} succ typing
+    {#{},{}} = M.
+
+t5() ->
+    V = f5(#{k=>q,a=>b}),
+    case V of
+	#{k := q, a := P} -> P; %% Must not warn here
+	_ -> ok
+    end,
+    ok.
+
+f5(M) -> %% Should get #{k:=q, ...} succ typing
+    #{k:=q} = M.
diff --git a/lib/dialyzer/test/map_SUITE_data/src/contract.erl b/lib/dialyzer/test/map_SUITE_data/src/contract.erl
new file mode 100644
index 0000000000..2b31be0d58
--- /dev/null
+++ b/lib/dialyzer/test/map_SUITE_data/src/contract.erl
@@ -0,0 +1,14 @@
+-module(missing).
+
+-export([t1/0, t2/0, t3/0, t4/0]).
+
+-spec f(#{a := 1, b => 2, c => 3}) -> ok.
+f(_) -> ok.
+
+t1() -> f(#{b => 2}).
+
+t2() -> f(#{a => 1, c => 4}).
+
+t3() -> f(#{a => 1, b => 2, e => 3}).
+
+t4() -> f(#{a => 1, b => 2}).
diff --git a/lib/dialyzer/test/map_SUITE_data/src/contract_violation.erl b/lib/dialyzer/test/map_SUITE_data/src/contract_violation.erl
new file mode 100644
index 0000000000..850f2cad34
--- /dev/null
+++ b/lib/dialyzer/test/map_SUITE_data/src/contract_violation.erl
@@ -0,0 +1,29 @@
+-module(contract_violation).
+
+-export([entry/1, beam_disasm_lines/2]).
+
+%%-----------------------------------------------------------------------
+
+-type lines() :: #{non_neg_integer() => {string(), non_neg_integer()}}.
+
+entry(Bin) ->
+    I = 42,
+    case beam_disasm_lines(Bin, ':-)') of
+	#{I := Loc} -> {good, Loc};
+	_ -> bad
+    end.
+
+-spec beam_disasm_lines(binary() | none, module()) -> lines().
+
+beam_disasm_lines(none, _) -> #{};
+beam_disasm_lines(<<NumLines:32, LineBin:NumLines/binary, FileBin/binary>>,
+		  _Module) ->
+    Lines = binary_to_term(LineBin),
+    Files = binary_to_term(FileBin),
+    lines_collect_items(Lines, Files, #{}).
+
+lines_collect_items([], _, Acc) -> Acc;
+lines_collect_items([{FileNo, LineNo}|Rest], Files, Acc) ->
+    #{FileNo := File} = Files,
+    lines_collect_items(
+      Rest, Files, Acc#{map_size(Acc)+1 => {location, File, LineNo}}).
diff --git a/lib/dialyzer/test/map_SUITE_data/src/exact.erl b/lib/dialyzer/test/map_SUITE_data/src/exact.erl
new file mode 100644
index 0000000000..e5ad02ec54
--- /dev/null
+++ b/lib/dialyzer/test/map_SUITE_data/src/exact.erl
@@ -0,0 +1,23 @@
+-module(exact).
+
+-export([t1/1, t2/1]).
+
+t1(M = #{}) ->
+    any_map(M),
+    case M of
+	#{a := _} -> error(fail);
+	_ -> ok
+    end.
+
+any_map(X) ->
+    X#{a => 1, a := 2}.
+
+t2(M = #{}) ->
+    has_a(M),
+    case M of
+	#{a := _} -> error(ok);
+	_ -> unreachable
+    end.
+
+has_a(M) ->
+    M#{a := 1, a => 2}.
diff --git a/lib/dialyzer/test/map_SUITE_data/src/guard_update.erl b/lib/dialyzer/test/map_SUITE_data/src/guard_update.erl
new file mode 100644
index 0000000000..19d0089401
--- /dev/null
+++ b/lib/dialyzer/test/map_SUITE_data/src/guard_update.erl
@@ -0,0 +1,18 @@
+-module(guard_update).
+
+-export([t/0, t2/0]).
+
+t() ->
+    f(#{a=>2}). %% Illegal
+
+f(M)
+  when M#{b := 7} =/= q
+       -> ok.
+
+t2() ->
+    f2(#{a=>2}). %% Legal!
+
+f2(M)
+  when M#{b := 7} =/= q;
+       M =/= p
+       -> ok.
diff --git a/lib/dialyzer/test/map_SUITE_data/src/initial_dataflow.erl b/lib/dialyzer/test/map_SUITE_data/src/initial_dataflow.erl
new file mode 100644
index 0000000000..bbc0d5682a
--- /dev/null
+++ b/lib/dialyzer/test/map_SUITE_data/src/initial_dataflow.erl
@@ -0,0 +1,11 @@
+-module(initial_dataflow).
+
+-export([test/0]).
+
+test() ->
+    false = assoc_guard(#{}),
+    true  = assoc_guard(not_a_map),
+    ok.
+
+assoc_guard(#{}) -> true;
+assoc_guard(Q) -> false.
diff --git a/lib/dialyzer/test/map_SUITE_data/src/is_map_guard.erl b/lib/dialyzer/test/map_SUITE_data/src/is_map_guard.erl
new file mode 100644
index 0000000000..ceb4a8763a
--- /dev/null
+++ b/lib/dialyzer/test/map_SUITE_data/src/is_map_guard.erl
@@ -0,0 +1,17 @@
+-module(is_map_guard).
+
+-export([t1/0, t2/0, implicit/1, explicit/1
+	]).
+
+t1() ->
+    _ = implicit(#{}),
+    implicit(not_a_map).
+
+implicit(M) ->
+    M#{}.
+
+t2() ->
+    explicit(#{q=>d}),
+    explicit(still_not_map).
+
+explicit(M) when is_map(M) -> ok.
diff --git a/lib/dialyzer/test/map_SUITE_data/src/map_galore.erl b/lib/dialyzer/test/map_SUITE_data/src/map_galore.erl
new file mode 100644
index 0000000000..2611241379
--- /dev/null
+++ b/lib/dialyzer/test/map_SUITE_data/src/map_galore.erl
@@ -0,0 +1,2824 @@
+%% %CopyrightBegin%
+%% 
+%% Copyright Ericsson AB 2013. All Rights Reserved.
+%% 
+%% Licensed under the Apache License, Version 2.0 (the "License");
+%% you may not use this file except in compliance with the License.
+%% You may obtain a copy of the License at
+%%
+%%     http://www.apache.org/licenses/LICENSE-2.0
+%%
+%% Unless required by applicable law or agreed to in writing, software
+%% distributed under the License is distributed on an "AS IS" BASIS,
+%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+%% See the License for the specific language governing permissions and
+%% limitations under the License.
+%% 
+%% %CopyrightEnd%
+%%
+-module(map_galore).
+-export([all/0, suite/0,groups/0,init_per_suite/1, end_per_suite/1, 
+	init_per_group/2,end_per_group/2
+    ]).
+
+-export([
+	t_build_and_match_literals/1, t_build_and_match_literals_large/1,
+	t_update_literals/1, t_update_literals_large/1,
+        t_match_and_update_literals/1, t_match_and_update_literals_large/1,
+	t_update_map_expressions/1,
+	t_update_assoc/1, t_update_assoc_large/1,
+        t_update_exact/1, t_update_exact_large/1,
+	t_guard_bifs/1,
+        t_guard_sequence/1, t_guard_sequence_large/1,
+        t_guard_update/1, t_guard_update_large/1,
+	t_guard_receive/1, t_guard_receive_large/1,
+        t_guard_fun/1,
+        t_update_deep/1,
+	t_list_comprehension/1,
+	t_map_sort_literals/1,
+	t_map_equal/1,
+	t_map_compare/1,
+	t_map_size/1,
+	t_is_map/1,
+
+	%% Specific Map BIFs
+	t_bif_map_get/1,
+	t_bif_map_find/1,
+	t_bif_map_is_key/1,
+	t_bif_map_keys/1,
+	t_bif_map_merge/1,
+	t_bif_map_new/1,
+	t_bif_map_put/1,
+	t_bif_map_remove/1,
+	t_bif_map_update/1,
+	t_bif_map_values/1,
+	t_bif_map_to_list/1,
+	t_bif_map_from_list/1,
+
+	%% erlang
+	t_erlang_hash/1,
+	t_map_encode_decode/1,
+
+	%% non specific BIF related
+	t_bif_build_and_check/1,
+	t_bif_merge_and_check/1,
+
+	%% maps module not bifs
+	t_maps_fold/1,
+	t_maps_map/1,
+	t_maps_size/1,
+	t_maps_without/1,
+
+	%% misc
+	t_erts_internal_order/1,
+        t_erts_internal_hash/1,
+	t_pdict/1,
+	t_ets/1,
+	t_dets/1,
+	t_tracing/1,
+
+	%% instruction-level tests
+	t_has_map_fields/1,
+	y_regs/1
+    ]).
+
+-include_lib("stdlib/include/ms_transform.hrl").
+
+-define(CHECK(Cond,Term),
+	case (catch (Cond)) of
+	    true -> true;
+	    _ -> io:format("###### CHECK FAILED ######~nINPUT:  ~p~n", [Term]),
+		 exit(Term)
+	end).
+
+suite() -> [].
+
+all() -> [
+	t_build_and_match_literals, t_build_and_match_literals_large,
+	t_update_literals, t_update_literals_large,
+        t_match_and_update_literals, t_match_and_update_literals_large,
+	t_update_map_expressions,
+	t_update_assoc, t_update_assoc_large,
+        t_update_exact, t_update_exact_large,
+	t_guard_bifs,
+        t_guard_sequence, t_guard_sequence_large,
+        t_guard_update, t_guard_update_large,
+	t_guard_receive, t_guard_receive_large,
+        t_guard_fun, t_list_comprehension,
+        t_update_deep,
+	t_map_equal, t_map_compare,
+	t_map_sort_literals,
+
+	%% Specific Map BIFs
+	t_bif_map_get,t_bif_map_find,t_bif_map_is_key,
+	t_bif_map_keys, t_bif_map_merge, t_bif_map_new,
+	t_bif_map_put,
+	t_bif_map_remove, t_bif_map_update,
+	t_bif_map_values,
+	t_bif_map_to_list, t_bif_map_from_list,
+
+	%% erlang
+	t_erlang_hash, t_map_encode_decode,
+	t_map_size, t_is_map,
+
+	%% non specific BIF related
+	t_bif_build_and_check,
+	t_bif_merge_and_check,
+
+	%% maps module
+	t_maps_fold, t_maps_map,
+	t_maps_size, t_maps_without,
+
+
+        %% Other functions
+	t_erts_internal_order,
+        t_erts_internal_hash,
+	t_pdict,
+	t_ets,
+	t_tracing,
+
+	%% instruction-level tests
+	t_has_map_fields,
+	y_regs
+    ].
+
+groups() -> [].
+
+init_per_suite(Config) -> Config.
+end_per_suite(_Config) -> ok.
+
+init_per_group(_GroupName, Config) -> Config.
+end_per_group(_GroupName, Config) -> Config.
+
+%% tests
+
+t_build_and_match_literals(Config) when is_list(Config) ->
+    #{} = #{},
+    #{1:=a} = #{1=>a},
+    #{1:=a,2:=b} = #{1=>a,2=>b},
+    #{1:=a,2:=b,3:="c"} = #{1=>a,2=>b,3=>"c"},
+    #{1:=a,2:=b,3:="c","4":="d"} = #{1=>a,2=>b,3=>"c","4"=>"d"},
+    #{1:=a,2:=b,3:="c","4":="d",<<"5">>:=<<"e">>} =
+	#{1=>a,2=>b,3=>"c","4"=>"d",<<"5">>=><<"e">>},
+    #{1:=a,2:=b,3:="c","4":="d",<<"5">>:=<<"e">>,{"6",7}:="f"} =
+	#{1=>a,2=>b,3=>"c","4"=>"d",<<"5">>=><<"e">>,{"6",7}=>"f"},
+    #{1:=a,2:=b,3:="c","4":="d",<<"5">>:=<<"e">>,{"6",7}:="f",8:=g} =
+	#{1=>a,2=>b,3=>"c","4"=>"d",<<"5">>=><<"e">>,{"6",7}=>"f",8=>g},
+
+    #{[]:=a,42.0:=b,x:={x,y},[a,b]:=list} =
+         #{[]=>a,42.0=>b,x=>{x,y},[a,b]=>list},
+
+    #{<<"hi all">> := 1} = #{<<"hi",32,"all">> => 1},
+
+    #{a:=X,a:=X=3,b:=4} = #{a=>3,b=>4}, % weird but ok =)
+
+    #{ a:=#{ b:=#{c := third, b:=second}}, b:=first} =
+	#{ b=>first, a=>#{ b=>#{c => third, b=> second}}},
+
+    M = #{ map_1=>#{ map_2=>#{value_3 => third}, value_2=> second}, value_1=>first},
+    M = #{ map_1:=#{ map_2:=#{value_3 := third}, value_2:= second}, value_1:=first} =
+	 #{ map_1=>#{ map_2=>#{value_3 => third}, value_2=> second}, value_1=>first},
+
+    %% error case
+    %V = 32,
+    %{'EXIT',{{badmatch,_},_}} = (catch (#{<<"hi all">> => 1} = #{<<"hi",V,"all">> => 1})),
+    {'EXIT',{{badmatch,_},_}} = (catch (#{x:=3,x:=2} = #{x=>3})),
+    {'EXIT',{{badmatch,_},_}} = (catch (#{x:=2} = #{x=>3})),
+    {'EXIT',{{badmatch,_},_}} = (catch (#{x:=3} = {a,b,c})),
+    {'EXIT',{{badmatch,_},_}} = (catch (#{x:=3} = #{y=>3})),
+    {'EXIT',{{badmatch,_},_}} = (catch (#{x:=3} = #{x=>"three"})),
+    ok.
+
+t_build_and_match_literals_large(Config) when is_list(Config) ->
+    % normal non-repeating
+    M0 = #{ 10=>a0,20=>b0,30=>"c0","40"=>"d0",<<"50">>=>"e0",{["00"]}=>"10",
+               11=>a1,21=>b1,31=>"c1","41"=>"d1",<<"51">>=>"e1",{["01"]}=>"11",
+               12=>a2,22=>b2,32=>"c2","42"=>"d2",<<"52">>=>"e2",{["02"]}=>"12",
+               13=>a3,23=>b3,33=>"c3","43"=>"d3",<<"53">>=>"e3",{["03"]}=>"13",
+               14=>a4,24=>b4,34=>"c4","44"=>"d4",<<"54">>=>"e4",{["04"]}=>"14",
+
+               15=>a5,25=>b5,35=>"c5","45"=>"d5",<<"55">>=>"e5",{["05"]}=>"15",
+               16=>a6,26=>b6,36=>"c6","46"=>"d6",<<"56">>=>"e6",{["06"]}=>"16",
+               17=>a7,27=>b7,37=>"c7","47"=>"d7",<<"57">>=>"e7",{["07"]}=>"17",
+               18=>a8,28=>b8,38=>"c8","48"=>"d8",<<"58">>=>"e8",{["08"]}=>"18",
+               19=>a9,29=>b9,39=>"c9","49"=>"d9",<<"59">>=>"e9",{["09"]}=>"19" },
+
+    #{10:=a0,20:=b0,30:="c0","40":="d0",<<"50">>:="e0",{["00"]}:="10"} = M0,
+    #{11:=a1,21:=b1,31:="c1","41":="d1",<<"51">>:="e1",{["01"]}:="11"} = M0,
+    #{12:=a2,22:=b2,32:="c2","42":="d2",<<"52">>:="e2",{["02"]}:="12"} = M0,
+    #{13:=a3,23:=b3,33:="c3","43":="d3",<<"53">>:="e3",{["03"]}:="13"} = M0,
+    #{14:=a4,24:=b4,34:="c4","44":="d4",<<"54">>:="e4",{["04"]}:="14"} = M0,
+
+    #{15:=a5,25:=b5,35:="c5","45":="d5",<<"55">>:="e5",{["05"]}:="15"} = M0,
+    #{16:=a6,26:=b6,36:="c6","46":="d6",<<"56">>:="e6",{["06"]}:="16"} = M0,
+    #{17:=a7,27:=b7,37:="c7","47":="d7",<<"57">>:="e7",{["07"]}:="17"} = M0,
+    #{18:=a8,28:=b8,38:="c8","48":="d8",<<"58">>:="e8",{["08"]}:="18"} = M0,
+    #{19:=a9,29:=b9,39:="c9","49":="d9",<<"59">>:="e9",{["09"]}:="19"} = M0,
+
+    60 = map_size(M0),
+    60 = maps:size(M0),
+
+    % with repeating
+    M1 = #{ 10=>a0,20=>b0,30=>"c0","40"=>"d0",<<"50">>=>"e0",{["00"]}=>"10",
+               11=>a1,21=>b1,31=>"c1","41"=>"d1",<<"51">>=>"e1",{["01"]}=>"11",
+               12=>a2,22=>b2,32=>"c2","42"=>"d2",<<"52">>=>"e2",{["02"]}=>"12",
+               13=>a3,23=>b3,33=>"c3","43"=>"d3",<<"53">>=>"e3",{["03"]}=>"13",
+               14=>a4,24=>b4,34=>"c4","44"=>"d4",<<"54">>=>"e4",{["04"]}=>"14",
+
+               10=>na0,20=>nb0,30=>"nc0","40"=>"nd0",<<"50">>=>"ne0",{["00"]}=>"n10",
+               11=>na1,21=>nb1,31=>"nc1","41"=>"nd1",<<"51">>=>"ne1",{["01"]}=>"n11",
+               12=>na2,22=>nb2,32=>"nc2","42"=>"nd2",<<"52">>=>"ne2",{["02"]}=>"n12",
+
+               15=>a5,25=>b5,35=>"c5","45"=>"d5",<<"55">>=>"e5",{["05"]}=>"15",
+               16=>a6,26=>b6,36=>"c6","46"=>"d6",<<"56">>=>"e6",{["06"]}=>"16",
+               17=>a7,27=>b7,37=>"c7","47"=>"d7",<<"57">>=>"e7",{["07"]}=>"17",
+
+               13=>na3,23=>nb3,33=>"nc3","43"=>"nd3",<<"53">>=>"ne3",{["03"]}=>"n13",
+               14=>na4,24=>nb4,34=>"nc4","44"=>"nd4",<<"54">>=>"ne4",{["04"]}=>"n14",
+
+               18=>a8,28=>b8,38=>"c8","48"=>"d8",<<"58">>=>"e8",{["08"]}=>"18",
+               19=>a9,29=>b9,39=>"c9","49"=>"d9",<<"59">>=>"e9",{["09"]}=>"19" },
+
+    #{10:=na0,20:=nb0,30:="nc0","40":="nd0",<<"50">>:="ne0",{["00"]}:="n10"} = M1,
+    #{11:=na1,21:=nb1,31:="nc1","41":="nd1",<<"51">>:="ne1",{["01"]}:="n11"} = M1,
+    #{12:=na2,22:=nb2,32:="nc2","42":="nd2",<<"52">>:="ne2",{["02"]}:="n12"} = M1,
+    #{13:=na3,23:=nb3,33:="nc3","43":="nd3",<<"53">>:="ne3",{["03"]}:="n13"} = M1,
+    #{14:=na4,24:=nb4,34:="nc4","44":="nd4",<<"54">>:="ne4",{["04"]}:="n14"} = M1,
+
+    #{15:=a5,25:=b5,35:="c5","45":="d5",<<"55">>:="e5",{["05"]}:="15"} = M1,
+    #{16:=a6,26:=b6,36:="c6","46":="d6",<<"56">>:="e6",{["06"]}:="16"} = M1,
+    #{17:=a7,27:=b7,37:="c7","47":="d7",<<"57">>:="e7",{["07"]}:="17"} = M1,
+    #{18:=a8,28:=b8,38:="c8","48":="d8",<<"58">>:="e8",{["08"]}:="18"} = M1,
+    #{19:=a9,29:=b9,39:="c9","49":="d9",<<"59">>:="e9",{["09"]}:="19"} = M1,
+
+    60 = map_size(M1),
+    60 = maps:size(M1),
+
+    % with floats
+
+    M2 = #{ 10=>a0,20=>b0,30=>"c0","40"=>"d0",<<"50">>=>"e0",{["00"]}=>"10",
+               11=>a1,21=>b1,31=>"c1","41"=>"d1",<<"51">>=>"e1",{["01"]}=>"11",
+               12=>a2,22=>b2,32=>"c2","42"=>"d2",<<"52">>=>"e2",{["02"]}=>"12",
+               13=>a3,23=>b3,33=>"c3","43"=>"d3",<<"53">>=>"e3",{["03"]}=>"13",
+               14=>a4,24=>b4,34=>"c4","44"=>"d4",<<"54">>=>"e4",{["04"]}=>"14",
+
+               15=>a5,25=>b5,35=>"c5","45"=>"d5",<<"55">>=>"e5",{["05"]}=>"15",
+               16=>a6,26=>b6,36=>"c6","46"=>"d6",<<"56">>=>"e6",{["06"]}=>"16",
+               17=>a7,27=>b7,37=>"c7","47"=>"d7",<<"57">>=>"e7",{["07"]}=>"17",
+               18=>a8,28=>b8,38=>"c8","48"=>"d8",<<"58">>=>"e8",{["08"]}=>"18",
+               19=>a9,29=>b9,39=>"c9","49"=>"d9",<<"59">>=>"e9",{["09"]}=>"19",
+
+               10.0=>fa0,20.0=>fb0,30.0=>"fc0",
+               11.0=>fa1,21.0=>fb1,31.0=>"fc1",
+               12.0=>fa2,22.0=>fb2,32.0=>"fc2",
+               13.0=>fa3,23.0=>fb3,33.0=>"fc3",
+               14.0=>fa4,24.0=>fb4,34.0=>"fc4",
+
+               15.0=>fa5,25.0=>fb5,35.0=>"fc5",
+               16.0=>fa6,26.0=>fb6,36.0=>"fc6",
+               17.0=>fa7,27.0=>fb7,37.0=>"fc7",
+               18.0=>fa8,28.0=>fb8,38.0=>"fc8",
+               19.0=>fa9,29.0=>fb9,39.0=>"fc9"},
+
+    #{10:=a0,20:=b0,30:="c0","40":="d0",<<"50">>:="e0",{["00"]}:="10"} = M2,
+    #{11:=a1,21:=b1,31:="c1","41":="d1",<<"51">>:="e1",{["01"]}:="11"} = M2,
+    #{12:=a2,22:=b2,32:="c2","42":="d2",<<"52">>:="e2",{["02"]}:="12"} = M2,
+    #{13:=a3,23:=b3,33:="c3","43":="d3",<<"53">>:="e3",{["03"]}:="13"} = M2,
+    #{14:=a4,24:=b4,34:="c4","44":="d4",<<"54">>:="e4",{["04"]}:="14"} = M2,
+
+    #{15:=a5,25:=b5,35:="c5","45":="d5",<<"55">>:="e5",{["05"]}:="15"} = M2,
+    #{16:=a6,26:=b6,36:="c6","46":="d6",<<"56">>:="e6",{["06"]}:="16"} = M2,
+    #{17:=a7,27:=b7,37:="c7","47":="d7",<<"57">>:="e7",{["07"]}:="17"} = M2,
+    #{18:=a8,28:=b8,38:="c8","48":="d8",<<"58">>:="e8",{["08"]}:="18"} = M2,
+    #{19:=a9,29:=b9,39:="c9","49":="d9",<<"59">>:="e9",{["09"]}:="19"} = M2,
+
+    #{10.0:=fa0,20.0:=fb0,30.0:="fc0","40":="d0",<<"50">>:="e0",{["00"]}:="10"} = M2,
+    #{11.0:=fa1,21.0:=fb1,31.0:="fc1","41":="d1",<<"51">>:="e1",{["01"]}:="11"} = M2,
+    #{12.0:=fa2,22.0:=fb2,32.0:="fc2","42":="d2",<<"52">>:="e2",{["02"]}:="12"} = M2,
+    #{13.0:=fa3,23.0:=fb3,33.0:="fc3","43":="d3",<<"53">>:="e3",{["03"]}:="13"} = M2,
+    #{14.0:=fa4,24.0:=fb4,34.0:="fc4","44":="d4",<<"54">>:="e4",{["04"]}:="14"} = M2,
+
+    #{15.0:=fa5,25.0:=fb5,35.0:="fc5","45":="d5",<<"55">>:="e5",{["05"]}:="15"} = M2,
+    #{16.0:=fa6,26.0:=fb6,36.0:="fc6","46":="d6",<<"56">>:="e6",{["06"]}:="16"} = M2,
+    #{17.0:=fa7,27.0:=fb7,37.0:="fc7","47":="d7",<<"57">>:="e7",{["07"]}:="17"} = M2,
+    #{18.0:=fa8,28.0:=fb8,38.0:="fc8","48":="d8",<<"58">>:="e8",{["08"]}:="18"} = M2,
+    #{19.0:=fa9,29.0:=fb9,39.0:="fc9","49":="d9",<<"59">>:="e9",{["09"]}:="19"} = M2,
+
+    90 = map_size(M2),
+    90 = maps:size(M2),
+
+    % with bignums
+    M3 = #{ 10=>a0,20=>b0,30=>"c0","40"=>"d0",<<"50">>=>"e0",{["00"]}=>"10",
+               11=>a1,21=>b1,31=>"c1","41"=>"d1",<<"51">>=>"e1",{["01"]}=>"11",
+               12=>a2,22=>b2,32=>"c2","42"=>"d2",<<"52">>=>"e2",{["02"]}=>"12",
+               13=>a3,23=>b3,33=>"c3","43"=>"d3",<<"53">>=>"e3",{["03"]}=>"13",
+               14=>a4,24=>b4,34=>"c4","44"=>"d4",<<"54">>=>"e4",{["04"]}=>"14",
+
+               15=>a5,25=>b5,35=>"c5","45"=>"d5",<<"55">>=>"e5",{["05"]}=>"15",
+               16=>a6,26=>b6,36=>"c6","46"=>"d6",<<"56">>=>"e6",{["06"]}=>"16",
+               17=>a7,27=>b7,37=>"c7","47"=>"d7",<<"57">>=>"e7",{["07"]}=>"17",
+               18=>a8,28=>b8,38=>"c8","48"=>"d8",<<"58">>=>"e8",{["08"]}=>"18",
+               19=>a9,29=>b9,39=>"c9","49"=>"d9",<<"59">>=>"e9",{["09"]}=>"19",
+
+               10.0=>fa0,20.0=>fb0,30.0=>"fc0",
+               11.0=>fa1,21.0=>fb1,31.0=>"fc1",
+               12.0=>fa2,22.0=>fb2,32.0=>"fc2",
+               13.0=>fa3,23.0=>fb3,33.0=>"fc3",
+               14.0=>fa4,24.0=>fb4,34.0=>"fc4",
+
+               15.0=>fa5,25.0=>fb5,35.0=>"fc5",
+               16.0=>fa6,26.0=>fb6,36.0=>"fc6",
+               17.0=>fa7,27.0=>fb7,37.0=>"fc7",
+               18.0=>fa8,28.0=>fb8,38.0=>"fc8",
+               19.0=>fa9,29.0=>fb9,39.0=>"fc9",
+
+               36893488147419103232=>big1,  73786976294838206464=>big2,
+               147573952589676412928=>big3, 18446744073709551616=>big4,
+               4294967296=>big5,            8589934592=>big6,
+               4294967295=>big7,            67108863=>big8
+             },
+
+    #{10:=a0,20:=b0,30:="c0","40":="d0",<<"50">>:="e0",{["00"]}:="10"} = M3,
+    #{11:=a1,21:=b1,31:="c1","41":="d1",<<"51">>:="e1",{["01"]}:="11"} = M3,
+    #{12:=a2,22:=b2,32:="c2","42":="d2",<<"52">>:="e2",{["02"]}:="12"} = M3,
+    #{13:=a3,23:=b3,33:="c3","43":="d3",<<"53">>:="e3",{["03"]}:="13"} = M3,
+    #{14:=a4,24:=b4,34:="c4","44":="d4",<<"54">>:="e4",{["04"]}:="14"} = M3,
+
+    #{15:=a5,25:=b5,35:="c5","45":="d5",<<"55">>:="e5",{["05"]}:="15"} = M3,
+    #{16:=a6,26:=b6,36:="c6","46":="d6",<<"56">>:="e6",{["06"]}:="16"} = M3,
+    #{17:=a7,27:=b7,37:="c7","47":="d7",<<"57">>:="e7",{["07"]}:="17"} = M3,
+    #{18:=a8,28:=b8,38:="c8","48":="d8",<<"58">>:="e8",{["08"]}:="18"} = M3,
+    #{19:=a9,29:=b9,39:="c9","49":="d9",<<"59">>:="e9",{["09"]}:="19"} = M3,
+
+    #{10.0:=fa0,20.0:=fb0,30.0:="fc0","40":="d0",<<"50">>:="e0",{["00"]}:="10"} = M3,
+    #{11.0:=fa1,21.0:=fb1,31.0:="fc1","41":="d1",<<"51">>:="e1",{["01"]}:="11"} = M3,
+    #{12.0:=fa2,22.0:=fb2,32.0:="fc2","42":="d2",<<"52">>:="e2",{["02"]}:="12"} = M3,
+    #{13.0:=fa3,23.0:=fb3,33.0:="fc3","43":="d3",<<"53">>:="e3",{["03"]}:="13"} = M3,
+    #{14.0:=fa4,24.0:=fb4,34.0:="fc4","44":="d4",<<"54">>:="e4",{["04"]}:="14"} = M3,
+
+    #{15.0:=fa5,25.0:=fb5,35.0:="fc5","45":="d5",<<"55">>:="e5",{["05"]}:="15"} = M3,
+    #{16.0:=fa6,26.0:=fb6,36.0:="fc6","46":="d6",<<"56">>:="e6",{["06"]}:="16"} = M3,
+    #{17.0:=fa7,27.0:=fb7,37.0:="fc7","47":="d7",<<"57">>:="e7",{["07"]}:="17"} = M3,
+    #{18.0:=fa8,28.0:=fb8,38.0:="fc8","48":="d8",<<"58">>:="e8",{["08"]}:="18"} = M3,
+    #{19.0:=fa9,29.0:=fb9,39.0:="fc9","49":="d9",<<"59">>:="e9",{["09"]}:="19"} = M3,
+
+    #{36893488147419103232:=big1,67108863:=big8,"45":="d5",<<"55">>:="e5",{["05"]}:="15"} = M3,
+    #{147573952589676412928:=big3,8589934592:=big6,"46":="d6",<<"56">>:="e6",{["06"]}:="16"} = M3,
+    #{4294967296:=big5,18446744073709551616:=big4,"47":="d7",<<"57">>:="e7",{["07"]}:="17"} = M3,
+    #{4294967295:=big7,73786976294838206464:=big2,"48":="d8",<<"58">>:="e8",{["08"]}:="18"} = M3,
+
+    98 = map_size(M3),
+    98 = maps:size(M3),
+
+    %% with maps
+
+    M4 = #{ 10=>a0,20=>b0,30=>"c0","40"=>"d0",<<"50">>=>"e0",{["00"]}=>"10",
+               11=>a1,21=>b1,31=>"c1","41"=>"d1",<<"51">>=>"e1",{["01"]}=>"11",
+               12=>a2,22=>b2,32=>"c2","42"=>"d2",<<"52">>=>"e2",{["02"]}=>"12",
+               13=>a3,23=>b3,33=>"c3","43"=>"d3",<<"53">>=>"e3",{["03"]}=>"13",
+               14=>a4,24=>b4,34=>"c4","44"=>"d4",<<"54">>=>"e4",{["04"]}=>"14",
+
+               15=>a5,25=>b5,35=>"c5","45"=>"d5",<<"55">>=>"e5",{["05"]}=>"15",
+               16=>a6,26=>b6,36=>"c6","46"=>"d6",<<"56">>=>"e6",{["06"]}=>"16",
+               17=>a7,27=>b7,37=>"c7","47"=>"d7",<<"57">>=>"e7",{["07"]}=>"17",
+               18=>a8,28=>b8,38=>"c8","48"=>"d8",<<"58">>=>"e8",{["08"]}=>"18",
+               19=>a9,29=>b9,39=>"c9","49"=>"d9",<<"59">>=>"e9",{["09"]}=>"19",
+
+               10.0=>fa0,20.0=>fb0,30.0=>"fc0",
+               11.0=>fa1,21.0=>fb1,31.0=>"fc1",
+               12.0=>fa2,22.0=>fb2,32.0=>"fc2",
+               13.0=>fa3,23.0=>fb3,33.0=>"fc3",
+               14.0=>fa4,24.0=>fb4,34.0=>"fc4",
+
+               15.0=>fa5,25.0=>fb5,35.0=>"fc5",
+               16.0=>fa6,26.0=>fb6,36.0=>"fc6",
+               17.0=>fa7,27.0=>fb7,37.0=>"fc7",
+               18.0=>fa8,28.0=>fb8,38.0=>"fc8",
+               19.0=>fa9,29.0=>fb9,39.0=>"fc9",
+
+               #{ one => small, map => key } => "small map key 1",
+               #{ second => small, map => key } => "small map key 2",
+               #{ third => small, map => key } => "small map key 3",
+
+               #{ 10=>a0,20=>b0,30=>"c0","40"=>"d0",<<"50">>=>"e0",{["00"]}=>"10",
+                  11=>a1,21=>b1,31=>"c1","41"=>"d1",<<"51">>=>"e1",{["01"]}=>"11",
+                  12=>a2,22=>b2,32=>"c2","42"=>"d2",<<"52">>=>"e2",{["02"]}=>"12",
+                  13=>a3,23=>b3,33=>"c3","43"=>"d3",<<"53">>=>"e3",{["03"]}=>"13",
+                  14=>a4,24=>b4,34=>"c4","44"=>"d4",<<"54">>=>"e4",{["04"]}=>"14",
+
+                  15=>a5,25=>b5,35=>"c5","45"=>"d5",<<"55">>=>"e5",{["05"]}=>"15",
+                  16=>a6,26=>b6,36=>"c6","46"=>"d6",<<"56">>=>"e6",{["06"]}=>"16",
+                  17=>a7,27=>b7,37=>"c7","47"=>"d7",<<"57">>=>"e7",{["07"]}=>"17",
+                  18=>a8,28=>b8,38=>"c8","48"=>"d8",<<"58">>=>"e8",{["08"]}=>"18",
+                  19=>a9,29=>b9,39=>"c9","49"=>"d9",<<"59">>=>"e9",{["09"]}=>"19" } => "large map key 1",
+
+               #{ 10=>a0,20=>b0,30=>"c0","40"=>"d0",<<"50">>=>"e0",{["00"]}=>"10",
+                  11=>a1,21=>b1,31=>"c1","41"=>"d1",<<"51">>=>"e1",{["01"]}=>"11",
+                  12=>a2,22=>b2,32=>"c2","42"=>"d2",<<"52">>=>"e2",{["02"]}=>"12",
+                  13=>a3,23=>b3,33=>"c3","43"=>"d3",<<"53">>=>"e3",{["03"]}=>"13",
+                  14=>a4,24=>b4,34=>"c4","44"=>"d4",<<"54">>=>"e4",{["04"]}=>"14",
+
+                  15=>a5,25=>b5,35=>"c5","45"=>"d5",<<"55">>=>"e5",{["05"]}=>"15",
+                  k16=>a6,k26=>b6,k36=>"c6","46"=>"d6",<<"56">>=>"e6",{["06"]}=>"16",
+                  17=>a7,27=>b7,37=>"c7","47"=>"d7",<<"57">>=>"e7",{["07"]}=>"17",
+                  18=>a8,28=>b8,38=>"c8","48"=>"d8",<<"58">>=>"e8",{["08"]}=>"18",
+                  19=>a9,29=>b9,39=>"c9","49"=>"d9",<<"59">>=>"e9",{["09"]}=>"19" } => "large map key 2" },
+
+    #{10:=a0,20:=b0,30:="c0","40":="d0",<<"50">>:="e0",{["00"]}:="10"} = M4,
+    #{11:=a1,21:=b1,31:="c1","41":="d1",<<"51">>:="e1",{["01"]}:="11"} = M4,
+    #{12:=a2,22:=b2,32:="c2","42":="d2",<<"52">>:="e2",{["02"]}:="12"} = M4,
+    #{13:=a3,23:=b3,33:="c3","43":="d3",<<"53">>:="e3",{["03"]}:="13"} = M4,
+    #{14:=a4,24:=b4,34:="c4","44":="d4",<<"54">>:="e4",{["04"]}:="14"} = M4,
+
+    #{15:=a5,25:=b5,35:="c5","45":="d5",<<"55">>:="e5",{["05"]}:="15"} = M4,
+    #{16:=a6,26:=b6,36:="c6","46":="d6",<<"56">>:="e6",{["06"]}:="16"} = M4,
+    #{17:=a7,27:=b7,37:="c7","47":="d7",<<"57">>:="e7",{["07"]}:="17"} = M4,
+    #{18:=a8,28:=b8,38:="c8","48":="d8",<<"58">>:="e8",{["08"]}:="18"} = M4,
+    #{19:=a9,29:=b9,39:="c9","49":="d9",<<"59">>:="e9",{["09"]}:="19"} = M4,
+
+    #{ #{ one => small, map => key }    := "small map key 1",
+       #{ second => small, map => key } := "small map key 2",
+       #{ third => small, map => key }  := "small map key 3" } = M4,
+
+    #{ #{ 10=>a0,20=>b0,30=>"c0","40"=>"d0",<<"50">>=>"e0",{["00"]}=>"10",
+          11=>a1,21=>b1,31=>"c1","41"=>"d1",<<"51">>=>"e1",{["01"]}=>"11",
+          12=>a2,22=>b2,32=>"c2","42"=>"d2",<<"52">>=>"e2",{["02"]}=>"12",
+          13=>a3,23=>b3,33=>"c3","43"=>"d3",<<"53">>=>"e3",{["03"]}=>"13",
+          14=>a4,24=>b4,34=>"c4","44"=>"d4",<<"54">>=>"e4",{["04"]}=>"14",
+
+          15=>a5,25=>b5,35=>"c5","45"=>"d5",<<"55">>=>"e5",{["05"]}=>"15",
+          16=>a6,26=>b6,36=>"c6","46"=>"d6",<<"56">>=>"e6",{["06"]}=>"16",
+          17=>a7,27=>b7,37=>"c7","47"=>"d7",<<"57">>=>"e7",{["07"]}=>"17",
+          18=>a8,28=>b8,38=>"c8","48"=>"d8",<<"58">>=>"e8",{["08"]}=>"18",
+          19=>a9,29=>b9,39=>"c9","49"=>"d9",<<"59">>=>"e9",{["09"]}=>"19" } := "large map key 1",
+
+       #{ 10=>a0,20=>b0,30=>"c0","40"=>"d0",<<"50">>=>"e0",{["00"]}=>"10",
+          11=>a1,21=>b1,31=>"c1","41"=>"d1",<<"51">>=>"e1",{["01"]}=>"11",
+          12=>a2,22=>b2,32=>"c2","42"=>"d2",<<"52">>=>"e2",{["02"]}=>"12",
+          13=>a3,23=>b3,33=>"c3","43"=>"d3",<<"53">>=>"e3",{["03"]}=>"13",
+          14=>a4,24=>b4,34=>"c4","44"=>"d4",<<"54">>=>"e4",{["04"]}=>"14",
+
+          15=>a5,25=>b5,35=>"c5","45"=>"d5",<<"55">>=>"e5",{["05"]}=>"15",
+          k16=>a6,k26=>b6,k36=>"c6","46"=>"d6",<<"56">>=>"e6",{["06"]}=>"16",
+          17=>a7,27=>b7,37=>"c7","47"=>"d7",<<"57">>=>"e7",{["07"]}=>"17",
+          18=>a8,28=>b8,38=>"c8","48"=>"d8",<<"58">>=>"e8",{["08"]}=>"18",
+          19=>a9,29=>b9,39=>"c9","49"=>"d9",<<"59">>=>"e9",{["09"]}=>"19" } := "large map key 2" } = M4,
+
+
+    #{ 15:=V1,25:=b5,35:=V2,"45":="d5",<<"55">>:=V3,{["05"]}:="15",
+       #{ one => small, map => key }    := "small map key 1",
+       #{ second => small, map => key } := V4,
+       #{ third => small, map => key }  := "small map key 3",
+       #{ 10=>a0,20=>b0,30=>"c0","40"=>"d0",<<"50">>=>"e0",{["00"]}=>"10",
+          11=>a1,21=>b1,31=>"c1","41"=>"d1",<<"51">>=>"e1",{["01"]}=>"11",
+          12=>a2,22=>b2,32=>"c2","42"=>"d2",<<"52">>=>"e2",{["02"]}=>"12",
+          13=>a3,23=>b3,33=>"c3","43"=>"d3",<<"53">>=>"e3",{["03"]}=>"13",
+          14=>a4,24=>b4,34=>"c4","44"=>"d4",<<"54">>=>"e4",{["04"]}=>"14",
+
+          15=>a5,25=>b5,35=>"c5","45"=>"d5",<<"55">>=>"e5",{["05"]}=>"15",
+          16=>a6,26=>b6,36=>"c6","46"=>"d6",<<"56">>=>"e6",{["06"]}=>"16",
+          17=>a7,27=>b7,37=>"c7","47"=>"d7",<<"57">>=>"e7",{["07"]}=>"17",
+          18=>a8,28=>b8,38=>"c8","48"=>"d8",<<"58">>=>"e8",{["08"]}=>"18",
+          19=>a9,29=>b9,39=>"c9","49"=>"d9",<<"59">>=>"e9",{["09"]}=>"19" } := V5 } = M4,
+
+    a5   = V1,
+    "c5" = V2,
+    "e5" = V3,
+    "small map key 2" = V4,
+    "large map key 1" = V5,
+
+    95 = map_size(M4),
+    95 = maps:size(M4),
+
+    % call for value
+
+    M5 = #{ 10=>a0,20=>b0,30=>"c0","40"=>"d0",<<"50">>=>"e0",{["00"]}=>"10",
+               11=>a1,21=>b1,31=>"c1","41"=>"d1",<<"51">>=>"e1",{["01"]}=>"11",
+               12=>a2,22=>b2,32=>"c2","42"=>"d2",<<"52">>=>"e2",{["02"]}=>"12",
+               13=>a3,23=>b3,33=>"c3","43"=>"d3",<<"53">>=>"e3",{["03"]}=>"13",
+               14=>a4,24=>b4,34=>"c4","44"=>"d4",<<"54">>=>"e4",{["04"]}=>"14",
+
+               15=>a5,25=>b5,35=>"c5","45"=>"d5",<<"55">>=>"e5",{["05"]}=>"15",
+               16=>a6,26=>b6,36=>"c6","46"=>"d6",<<"56">>=>"e6",{["06"]}=>"16",
+               17=>a7,27=>b7,37=>"c7","47"=>"d7",<<"57">>=>"e7",{["07"]}=>"17",
+               18=>a8,28=>b8,38=>"c8","48"=>"d8",<<"58">>=>"e8",{["08"]}=>"18",
+               19=>a9,29=>b9,39=>"c9","49"=>"d9",<<"59">>=>"e9",{["09"]}=>"19",
+
+               10.0=>fa0,20.0=>fb0,30.0=>"fc0",
+               11.0=>fa1,21.0=>fb1,31.0=>"fc1",
+               12.0=>fa2,22.0=>fb2,32.0=>"fc2",
+               13.0=>fa3,23.0=>fb3,33.0=>"fc3",
+               14.0=>fa4,24.0=>fb4,34.0=>"fc4",
+
+               15.0=>fa5,25.0=>fb5,35.0=>"fc5",
+               16.0=>fa6,26.0=>fb6,36.0=>"fc6",
+               17.0=>fa7,27.0=>fb7,37.0=>"fc7",
+               18.0=>fa8,28.0=>fb8,38.0=>"fc8",
+               19.0=>fa9,29.0=>fb9,39.0=>"fc9",
+
+               #{ one => small, map => key } => "small map key 1",
+               #{ second => small, map => key } => "small map key 2",
+               #{ third => small, map => key } => "small map key 3",
+
+               #{ 10=>a0,20=>b0,30=>"c0","40"=>"d0",<<"50">>=>"e0",{["00"]}=>"10",
+                  11=>a1,21=>b1,31=>"c1","41"=>"d1",<<"51">>=>"e1",{["01"]}=>"11",
+                  12=>a2,22=>b2,32=>"c2","42"=>"d2",<<"52">>=>"e2",{["02"]}=>"12",
+                  13=>a3,23=>b3,33=>"c3","43"=>"d3",<<"53">>=>"e3",{["03"]}=>"13",
+                  14=>a4,24=>b4,34=>"c4","44"=>"d4",<<"54">>=>"e4",{["04"]}=>"14",
+
+                  15=>a5,25=>b5,35=>"c5","45"=>"d5",<<"55">>=>"e5",{["05"]}=>"15",
+                  16=>a6,26=>b6,36=>"c6","46"=>"d6",<<"56">>=>"e6",{["06"]}=>"16",
+                  17=>a7,27=>b7,37=>"c7","47"=>"d7",<<"57">>=>"e7",{["07"]}=>"17",
+                  18=>a8,28=>b8,38=>"c8","48"=>"d8",<<"58">>=>"e8",{["08"]}=>"18",
+                  19=>a9,29=>b9,39=>"c9","49"=>"d9",<<"59">>=>"e9",{["09"]}=>"19" } => "large map key 1",
+
+               #{ 10=>a0,20=>b0,30=>"c0","40"=>"d0",<<"50">>=>"e0",{["00"]}=>"10",
+                  11=>a1,21=>b1,31=>"c1","41"=>"d1",<<"51">>=>"e1",{["01"]}=>"11",
+                  12=>a2,22=>b2,32=>"c2","42"=>"d2",<<"52">>=>"e2",{["02"]}=>"12",
+                  13=>a3,23=>b3,33=>"c3","43"=>"d3",<<"53">>=>"e3",{["03"]}=>"13",
+                  14=>a4,24=>b4,34=>"c4","44"=>"d4",<<"54">>=>"e4",{["04"]}=>"14",
+
+                  15=>a5,25=>b5,35=>"c5","45"=>"d5",<<"55">>=>"e5",{["05"]}=>"15",
+                  k16=>a6,k26=>b6,k36=>"c6","46"=>"d6",<<"56">>=>"e6",{["06"]}=>"16",
+                  17=>a7,27=>b7,37=>"c7","47"=>"d7",<<"57">>=>"e7",{["07"]}=>"17",
+                  18=>a8,28=>b8,38=>"c8","48"=>"d8",<<"58">>=>"e8",{["08"]}=>"18",
+                  19=>a9,29=>b9,39=>"c9","49"=>"d9",<<"59">>=>"e9",{["09"]}=>"19" } => "large map key 2" },
+
+    #{10:=a0,20:=b0,30:="c0","40":="d0",<<"50">>:="e0",{["00"]}:="10"} = M5,
+    #{11:=a1,21:=b1,31:="c1","41":="d1",<<"51">>:="e1",{["01"]}:="11"} = M5,
+    #{12:=a2,22:=b2,32:="c2","42":="d2",<<"52">>:="e2",{["02"]}:="12"} = M5,
+    #{13:=a3,23:=b3,33:="c3","43":="d3",<<"53">>:="e3",{["03"]}:="13"} = M5,
+    #{14:=a4,24:=b4,34:="c4","44":="d4",<<"54">>:="e4",{["04"]}:="14"} = M5,
+
+    #{15:=a5,25:=b5,35:="c5","45":="d5",<<"55">>:="e5",{["05"]}:="15"} = M5,
+    #{16:=a6,26:=b6,36:="c6","46":="d6",<<"56">>:="e6",{["06"]}:="16"} = M5,
+    #{17:=a7,27:=b7,37:="c7","47":="d7",<<"57">>:="e7",{["07"]}:="17"} = M5,
+    #{18:=a8,28:=b8,38:="c8","48":="d8",<<"58">>:="e8",{["08"]}:="18"} = M5,
+    #{19:=a9,29:=b9,39:="c9","49":="d9",<<"59">>:="e9",{["09"]}:="19"} = M5,
+
+    #{ #{ one => small, map => key }    := "small map key 1",
+       #{ second => small, map => key } := "small map key 2",
+       #{ third => small, map => key }  := "small map key 3" } = M5,
+
+    #{ #{ 10=>a0,20=>b0,30=>"c0","40"=>"d0",<<"50">>=>"e0",{["00"]}=>"10",
+          11=>a1,21=>b1,31=>"c1","41"=>"d1",<<"51">>=>"e1",{["01"]}=>"11",
+          12=>a2,22=>b2,32=>"c2","42"=>"d2",<<"52">>=>"e2",{["02"]}=>"12",
+          13=>a3,23=>b3,33=>"c3","43"=>"d3",<<"53">>=>"e3",{["03"]}=>"13",
+          14=>a4,24=>b4,34=>"c4","44"=>"d4",<<"54">>=>"e4",{["04"]}=>"14",
+
+          15=>a5,25=>b5,35=>"c5","45"=>"d5",<<"55">>=>"e5",{["05"]}=>"15",
+          16=>a6,26=>b6,36=>"c6","46"=>"d6",<<"56">>=>"e6",{["06"]}=>"16",
+          17=>a7,27=>b7,37=>"c7","47"=>"d7",<<"57">>=>"e7",{["07"]}=>"17",
+          18=>a8,28=>b8,38=>"c8","48"=>"d8",<<"58">>=>"e8",{["08"]}=>"18",
+          19=>a9,29=>b9,39=>"c9","49"=>"d9",<<"59">>=>"e9",{["09"]}=>"19" } := "large map key 1",
+
+       #{ 10=>a0,20=>b0,30=>"c0","40"=>"d0",<<"50">>=>"e0",{["00"]}=>"10",
+          11=>a1,21=>b1,31=>"c1","41"=>"d1",<<"51">>=>"e1",{["01"]}=>"11",
+          12=>a2,22=>b2,32=>"c2","42"=>"d2",<<"52">>=>"e2",{["02"]}=>"12",
+          13=>a3,23=>b3,33=>"c3","43"=>"d3",<<"53">>=>"e3",{["03"]}=>"13",
+          14=>a4,24=>b4,34=>"c4","44"=>"d4",<<"54">>=>"e4",{["04"]}=>"14",
+
+          15=>a5,25=>b5,35=>"c5","45"=>"d5",<<"55">>=>"e5",{["05"]}=>"15",
+          k16=>a6,k26=>b6,k36=>"c6","46"=>"d6",<<"56">>=>"e6",{["06"]}=>"16",
+          17=>a7,27=>b7,37=>"c7","47"=>"d7",<<"57">>=>"e7",{["07"]}=>"17",
+          18=>a8,28=>b8,38=>"c8","48"=>"d8",<<"58">>=>"e8",{["08"]}=>"18",
+          19=>a9,29=>b9,39=>"c9","49"=>"d9",<<"59">>=>"e9",{["09"]}=>"19" } := "large map key 2" } = M5,
+
+    95 = map_size(M5),
+    95 = maps:size(M5),
+
+    %% remember
+
+    #{10:=a0,20:=b0,30:="c0","40":="d0",<<"50">>:="e0",{["00"]}:="10"} = M0,
+    #{11:=a1,21:=b1,31:="c1","41":="d1",<<"51">>:="e1",{["01"]}:="11"} = M0,
+    #{12:=a2,22:=b2,32:="c2","42":="d2",<<"52">>:="e2",{["02"]}:="12"} = M0,
+    #{13:=a3,23:=b3,33:="c3","43":="d3",<<"53">>:="e3",{["03"]}:="13"} = M0,
+    #{14:=a4,24:=b4,34:="c4","44":="d4",<<"54">>:="e4",{["04"]}:="14"} = M0,
+
+    #{10:=na0,20:=nb0,30:="nc0","40":="nd0",<<"50">>:="ne0",{["00"]}:="n10"} = M1,
+    #{11:=na1,21:=nb1,31:="nc1","41":="nd1",<<"51">>:="ne1",{["01"]}:="n11"} = M1,
+    #{12:=na2,22:=nb2,32:="nc2","42":="nd2",<<"52">>:="ne2",{["02"]}:="n12"} = M1,
+    #{13:=na3,23:=nb3,33:="nc3","43":="nd3",<<"53">>:="ne3",{["03"]}:="n13"} = M1,
+    #{14:=na4,24:=nb4,34:="nc4","44":="nd4",<<"54">>:="ne4",{["04"]}:="n14"} = M1,
+
+    #{15:=a5,25:=b5,35:="c5","45":="d5",<<"55">>:="e5",{["05"]}:="15"} = M1,
+    #{16:=a6,26:=b6,36:="c6","46":="d6",<<"56">>:="e6",{["06"]}:="16"} = M1,
+    #{17:=a7,27:=b7,37:="c7","47":="d7",<<"57">>:="e7",{["07"]}:="17"} = M1,
+    #{18:=a8,28:=b8,38:="c8","48":="d8",<<"58">>:="e8",{["08"]}:="18"} = M1,
+    #{19:=a9,29:=b9,39:="c9","49":="d9",<<"59">>:="e9",{["09"]}:="19"} = M1,
+
+    #{15:=a5,25:=b5,35:="c5","45":="d5",<<"55">>:="e5",{["05"]}:="15"} = M2,
+    #{16:=a6,26:=b6,36:="c6","46":="d6",<<"56">>:="e6",{["06"]}:="16"} = M2,
+    #{17:=a7,27:=b7,37:="c7","47":="d7",<<"57">>:="e7",{["07"]}:="17"} = M2,
+    #{18:=a8,28:=b8,38:="c8","48":="d8",<<"58">>:="e8",{["08"]}:="18"} = M2,
+    #{19:=a9,29:=b9,39:="c9","49":="d9",<<"59">>:="e9",{["09"]}:="19"} = M2,
+
+    #{10.0:=fa0,20.0:=fb0,30.0:="fc0","40":="d0",<<"50">>:="e0",{["00"]}:="10"} = M2,
+    #{11.0:=fa1,21.0:=fb1,31.0:="fc1","41":="d1",<<"51">>:="e1",{["01"]}:="11"} = M2,
+    #{12.0:=fa2,22.0:=fb2,32.0:="fc2","42":="d2",<<"52">>:="e2",{["02"]}:="12"} = M2,
+    #{13.0:=fa3,23.0:=fb3,33.0:="fc3","43":="d3",<<"53">>:="e3",{["03"]}:="13"} = M2,
+    #{14.0:=fa4,24.0:=fb4,34.0:="fc4","44":="d4",<<"54">>:="e4",{["04"]}:="14"} = M2,
+
+    #{15:=a5,25:=b5,35:="c5","45":="d5",<<"55">>:="e5",{["05"]}:="15"} = M3,
+    #{16:=a6,26:=b6,36:="c6","46":="d6",<<"56">>:="e6",{["06"]}:="16"} = M3,
+    #{17:=a7,27:=b7,37:="c7","47":="d7",<<"57">>:="e7",{["07"]}:="17"} = M3,
+    #{18:=a8,28:=b8,38:="c8","48":="d8",<<"58">>:="e8",{["08"]}:="18"} = M3,
+    #{19:=a9,29:=b9,39:="c9","49":="d9",<<"59">>:="e9",{["09"]}:="19"} = M3,
+
+    #{10.0:=fa0,20.0:=fb0,30.0:="fc0","40":="d0",<<"50">>:="e0",{["00"]}:="10"} = M3,
+    #{11.0:=fa1,21.0:=fb1,31.0:="fc1","41":="d1",<<"51">>:="e1",{["01"]}:="11"} = M3,
+    #{12.0:=fa2,22.0:=fb2,32.0:="fc2","42":="d2",<<"52">>:="e2",{["02"]}:="12"} = M3,
+    #{13.0:=fa3,23.0:=fb3,33.0:="fc3","43":="d3",<<"53">>:="e3",{["03"]}:="13"} = M3,
+    #{14.0:=fa4,24.0:=fb4,34.0:="fc4","44":="d4",<<"54">>:="e4",{["04"]}:="14"} = M3,
+
+    #{15.0:=fa5,25.0:=fb5,35.0:="fc5","45":="d5",<<"55">>:="e5",{["05"]}:="15"} = M3,
+    #{16.0:=fa6,26.0:=fb6,36.0:="fc6","46":="d6",<<"56">>:="e6",{["06"]}:="16"} = M3,
+    #{17.0:=fa7,27.0:=fb7,37.0:="fc7","47":="d7",<<"57">>:="e7",{["07"]}:="17"} = M3,
+    #{18.0:=fa8,28.0:=fb8,38.0:="fc8","48":="d8",<<"58">>:="e8",{["08"]}:="18"} = M3,
+    #{19.0:=fa9,29.0:=fb9,39.0:="fc9","49":="d9",<<"59">>:="e9",{["09"]}:="19"} = M3,
+
+    #{36893488147419103232:=big1,67108863:=big8,"45":="d5",<<"55">>:="e5",{["05"]}:="15"} = M3,
+    #{147573952589676412928:=big3,8589934592:=big6,"46":="d6",<<"56">>:="e6",{["06"]}:="16"} = M3,
+    #{4294967296:=big5,18446744073709551616:=big4,"47":="d7",<<"57">>:="e7",{["07"]}:="17"} = M3,
+    #{4294967295:=big7,73786976294838206464:=big2,"48":="d8",<<"58">>:="e8",{["08"]}:="18"} = M3,
+
+    ok.
+
+
+t_map_size(Config) when is_list(Config) ->
+    0 = map_size(#{}),
+    1 = map_size(#{a=>1}),
+    1 = map_size(#{a=>"wat"}),
+    2 = map_size(#{a=>1, b=>2}),
+    3 = map_size(#{a=>1, b=>2, b=>"3","33"=><<"n">>}),
+
+    true = map_is_size(#{a=>1}, 1),
+    true = map_is_size(#{a=>1, a=>2}, 1),
+    M = #{ "a" => 1, "b" => 2},
+    true  = map_is_size(M, 2),
+    false = map_is_size(M, 3),
+    true  = map_is_size(M#{ "a" => 2}, 2),
+    false = map_is_size(M#{ "c" => 2}, 2),
+
+    Ks = [build_key(fun(K) -> <<1,K:32,1>> end,I)||I<-lists:seq(1,100)],
+    ok = build_and_check_size(Ks,0,#{}),
+
+    %% try deep collisions
+    %% statistically we get another subtree at 50k -> 100k elements
+    %% Try to be nice and don't use too much memory in the testcase,
+
+    N  = 500000,
+    Is = lists:seq(1,N),
+    N  = map_size(maps:from_list([{I,I}||I<-Is])),
+    N  = map_size(maps:from_list([{<<I:32>>,I}||I<-Is])),
+    N  = map_size(maps:from_list([{integer_to_list(I),I}||I<-Is])),
+    N  = map_size(maps:from_list([{float(I),I}||I<-Is])),
+
+    %% Error cases.
+    do_badmap(fun(T) ->
+                    {'EXIT',{{badmap,T},_}} =
+                      (catch map_size(T))
+              end),
+    ok.
+
+build_and_check_size([K|Ks],N,M0) ->
+    N = map_size(M0),
+    M1 = M0#{ K => K },
+    build_and_check_size(Ks,N + 1,M1);
+build_and_check_size([],N,M) ->
+    N = map_size(M),
+    ok.
+
+map_is_size(M,N) when map_size(M) =:= N -> true;
+map_is_size(_,_) -> false.
+
+t_is_map(Config) when is_list(Config) ->
+    true = is_map(#{}),
+    true = is_map(#{a=>1}),
+    false = is_map({a,b}),
+    false = is_map(x),
+    if is_map(#{}) -> ok end,
+    if is_map(#{b=>1}) -> ok end,
+    if not is_map([1,2,3]) -> ok end,
+    if not is_map(x) -> ok end,
+    ok.
+
+% test map updates without matching
+t_update_literals_large(Config) when is_list(Config) ->
+    Map = #{ 10=>a0,20=>b0,30=>"c0","40"=>"d0",<<"50">>=>"e0",{["00"]}=>"10",
+                11=>a1,21=>b1,31=>"c1","41"=>"d1",<<"51">>=>"e1",{["01"]}=>"11",
+                12=>a2,22=>b2,32=>"c2","42"=>"d2",<<"52">>=>"e2",{["02"]}=>"12",
+                13=>a3,23=>b3,33=>"c3","43"=>"d3",<<"53">>=>"e3",{["03"]}=>"13",
+                14=>a4,24=>b4,34=>"c4","44"=>"d4",<<"54">>=>"e4",{["04"]}=>"14",
+
+                15=>a5,25=>b5,35=>"c5","45"=>"d5",<<"55">>=>"e5",{["05"]}=>"15",
+                16=>a6,26=>b6,36=>"c6","46"=>"d6",<<"56">>=>"e6",{["06"]}=>"16",
+                17=>a7,27=>b7,37=>"c7","47"=>"d7",<<"57">>=>"e7",{["07"]}=>"17",
+                18=>a8,28=>b8,38=>"c8","48"=>"d8",<<"58">>=>"e8",{["08"]}=>"18",
+                19=>a9,29=>b9,39=>"c9","49"=>"d9",<<"59">>=>"e9",{["09"]}=>"19",
+
+                10.0=>fa0,20.0=>fb0,30.0=>"fc0",
+                11.0=>fa1,21.0=>fb1,31.0=>"fc1",
+                12.0=>fa2,22.0=>fb2,32.0=>"fc2",
+                13.0=>fa3,23.0=>fb3,33.0=>"fc3",
+                14.0=>fa4,24.0=>fb4,34.0=>"fc4",
+
+                15.0=>fa5,25.0=>fb5,35.0=>"fc5",
+                16.0=>fa6,26.0=>fb6,36.0=>"fc6",
+                17.0=>fa7,27.0=>fb7,37.0=>"fc7",
+                18.0=>fa8,28.0=>fb8,38.0=>"fc8",
+                19.0=>fa9,29.0=>fb9,39.0=>"fc9",
+
+                #{ one => small, map => key } => "small map key 1",
+                #{ second => small, map => key } => "small map key 2",
+                #{ third => small, map => key } => "small map key 3",
+
+                #{ 10=>a0,20=>b0,30=>"c0","40"=>"d0",<<"50">>=>"e0",{["00"]}=>"10",
+                   11=>a1,21=>b1,31=>"c1","41"=>"d1",<<"51">>=>"e1",{["01"]}=>"11",
+                   12=>a2,22=>b2,32=>"c2","42"=>"d2",<<"52">>=>"e2",{["02"]}=>"12",
+                   13=>a3,23=>b3,33=>"c3","43"=>"d3",<<"53">>=>"e3",{["03"]}=>"13",
+                   14=>a4,24=>b4,34=>"c4","44"=>"d4",<<"54">>=>"e4",{["04"]}=>"14",
+
+                   15=>a5,25=>b5,35=>"c5","45"=>"d5",<<"55">>=>"e5",{["05"]}=>"15",
+                   16=>a6,26=>b6,36=>"c6","46"=>"d6",<<"56">>=>"e6",{["06"]}=>"16",
+                   17=>a7,27=>b7,37=>"c7","47"=>"d7",<<"57">>=>"e7",{["07"]}=>"17",
+                   18=>a8,28=>b8,38=>"c8","48"=>"d8",<<"58">>=>"e8",{["08"]}=>"18",
+                   19=>a9,29=>b9,39=>"c9","49"=>"d9",<<"59">>=>"e9",{["09"]}=>"19" } => "large map key 1",
+
+                #{ 10=>a0,20=>b0,30=>"c0","40"=>"d0",<<"50">>=>"e0",{["00"]}=>"10",
+                   11=>a1,21=>b1,31=>"c1","41"=>"d1",<<"51">>=>"e1",{["01"]}=>"11",
+                   12=>a2,22=>b2,32=>"c2","42"=>"d2",<<"52">>=>"e2",{["02"]}=>"12",
+                   13=>a3,23=>b3,33=>"c3","43"=>"d3",<<"53">>=>"e3",{["03"]}=>"13",
+                   14=>a4,24=>b4,34=>"c4","44"=>"d4",<<"54">>=>"e4",{["04"]}=>"14",
+
+                   15=>a5,25=>b5,35=>"c5","45"=>"d5",<<"55">>=>"e5",{["05"]}=>"15",
+                   k16=>a6,k26=>b6,k36=>"c6","46"=>"d6",<<"56">>=>"e6",{["06"]}=>"16",
+                   17=>a7,27=>b7,37=>"c7","47"=>"d7",<<"57">>=>"e7",{["07"]}=>"17",
+                   18=>a8,28=>b8,38=>"c8","48"=>"d8",<<"58">>=>"e8",{["08"]}=>"18",
+                   19=>a9,29=>b9,39=>"c9","49"=>"d9",<<"59">>=>"e9",{["09"]}=>"19" } => "large map key 2" },
+
+    #{x:="d",q:="4"} = loop_update_literals_x_q(Map, [
+		{"a","1"},{"b","2"},{"c","3"},{"d","4"}
+	]),
+    ok.
+
+t_update_literals(Config) when is_list(Config) ->
+    Map = #{x=>1,y=>2,z=>3,q=>4},
+    #{x:="d",q:="4"} = loop_update_literals_x_q(Map, [
+		{"a","1"},{"b","2"},{"c","3"},{"d","4"}
+	]),
+    ok.
+
+
+loop_update_literals_x_q(Map, []) -> Map;
+loop_update_literals_x_q(Map, [{X,Q}|Vs]) ->
+    loop_update_literals_x_q(Map#{q=>Q,x=>X},Vs).
+
+% test map updates with matching
+t_match_and_update_literals(Config) when is_list(Config) ->
+    Map = #{ x=>0,y=>"untouched",z=>"also untouched",q=>1,
+             #{ "one" => small, map => key } => "small map key 1" },
+    #{x:=16,q:=21,y:="untouched",z:="also untouched"} = loop_match_and_update_literals_x_q(Map, [
+	    {1,2},{3,4},{5,6},{7,8}
+	]),
+    M0 = #{ "hi" => "hello", int => 3, <<"key">> => <<"value">>,
+	    4 => number, 18446744073709551629 => wat},
+    M1 = #{},
+    M2 = M1#{ "hi" => "hello", int => 3, <<"key">> => <<"value">>,
+	4 => number, 18446744073709551629 => wat},
+    M0 = M2,
+
+    #{ 4 := another_number, int := 3 } = M2#{ 4 => another_number },
+    ok.
+
+t_match_and_update_literals_large(Config) when is_list(Config) ->
+    Map = #{ 10=>a0,20=>b0,30=>"c0","40"=>"d0",<<"50">>=>"e0",{["00"]}=>"10",
+                11=>a1,21=>b1,31=>"c1","41"=>"d1",<<"51">>=>"e1",{["01"]}=>"11",
+                12=>a2,22=>b2,32=>"c2","42"=>"d2",<<"52">>=>"e2",{["02"]}=>"12",
+                13=>a3,23=>b3,33=>"c3","43"=>"d3",<<"53">>=>"e3",{["03"]}=>"13",
+                14=>a4,24=>b4,34=>"c4","44"=>"d4",<<"54">>=>"e4",{["04"]}=>"14",
+
+                15=>a5,25=>b5,35=>"c5","45"=>"d5",<<"55">>=>"e5",{["05"]}=>"15",
+                16=>a6,26=>b6,36=>"c6","46"=>"d6",<<"56">>=>"e6",{["06"]}=>"16",
+                17=>a7,27=>b7,37=>"c7","47"=>"d7",<<"57">>=>"e7",{["07"]}=>"17",
+                18=>a8,28=>b8,38=>"c8","48"=>"d8",<<"58">>=>"e8",{["08"]}=>"18",
+                19=>a9,29=>b9,39=>"c9","49"=>"d9",<<"59">>=>"e9",{["09"]}=>"19",
+
+                10.0=>fa0,20.0=>fb0,30.0=>"fc0",
+                11.0=>fa1,21.0=>fb1,31.0=>"fc1",
+                12.0=>fa2,22.0=>fb2,32.0=>"fc2",
+                13.0=>fa3,23.0=>fb3,33.0=>"fc3",
+                14.0=>fa4,24.0=>fb4,34.0=>"fc4",
+
+                15.0=>fa5,25.0=>fb5,35.0=>"fc5",
+                16.0=>fa6,26.0=>fb6,36.0=>"fc6",
+                17.0=>fa7,27.0=>fb7,37.0=>"fc7",
+                18.0=>fa8,28.0=>fb8,38.0=>"fc8",
+                19.0=>fa9,29.0=>fb9,39.0=>"fc9",
+
+                x=>0,y=>"untouched",z=>"also untouched",q=>1,
+
+                #{ "one" => small, map => key } => "small map key 1",
+                #{ second => small, map => key } => "small map key 2",
+                #{ third => small, map => key } => "small map key 3",
+
+                #{ 10=>a0,20=>b0,30=>"c0","40"=>"d0",<<"50">>=>"e0",{["00"]}=>"10",
+                   11=>a1,21=>b1,31=>"c1","41"=>"d1",<<"51">>=>"e1",{["01"]}=>"11",
+                   12=>a2,22=>b2,32=>"c2","42"=>"d2",<<"52">>=>"e2",{["02"]}=>"12",
+                   13=>a3,23=>b3,33=>"c3","43"=>"d3",<<"53">>=>"e3",{["03"]}=>"13",
+                   14=>a4,24=>b4,34=>"c4","44"=>"d4",<<"54">>=>"e4",{["04"]}=>"14",
+
+                   15=>a5,25=>b5,35=>"c5","45"=>"d5",<<"55">>=>"e5",{["05"]}=>"15",
+                   16=>a6,26=>b6,36=>"c6","46"=>"d6",<<"56">>=>"e6",{["06"]}=>"16",
+                   17=>a7,27=>b7,37=>"c7","47"=>"d7",<<"57">>=>"e7",{["07"]}=>"17",
+                   18=>a8,28=>b8,38=>"c8","48"=>"d8",<<"58">>=>"e8",{["08"]}=>"18",
+                   19=>a9,29=>b9,39=>"c9","49"=>"d9",<<"59">>=>"e9",{["09"]}=>"19" } => "large map key 1",
+
+                #{ 10=>a0,20=>b0,30=>"c0","40"=>"d0",<<"50">>=>"e0",{["00"]}=>"10",
+                   11=>a1,21=>b1,31=>"c1","41"=>"d1",<<"51">>=>"e1",{["01"]}=>"11",
+                   12=>a2,22=>b2,32=>"c2","42"=>"d2",<<"52">>=>"e2",{["02"]}=>"12",
+                   13=>a3,23=>b3,33=>"c3","43"=>"d3",<<"53">>=>"e3",{["03"]}=>"13",
+                   14=>a4,24=>b4,34=>"c4","44"=>"d4",<<"54">>=>"e4",{["04"]}=>"14",
+
+                   15=>a5,25=>b5,35=>"c5","45"=>"d5",<<"55">>=>"e5",{["05"]}=>"15",
+                   k16=>a6,k26=>b6,k36=>"c6","46"=>"d6",<<"56">>=>"e6",{["06"]}=>"16",
+                   17=>a7,27=>b7,37=>"c7","47"=>"d7",<<"57">>=>"e7",{["07"]}=>"17",
+                   18=>a8,28=>b8,38=>"c8","48"=>"d8",<<"58">>=>"e8",{["08"]}=>"18",
+                   19=>a9,29=>b9,39=>"c9","49"=>"d9",<<"59">>=>"e9",{["09"]}=>"19" } => "large map key 2" },
+
+    #{x:=16,q:=21,y:="untouched",z:="also untouched"} = loop_match_and_update_literals_x_q(Map, [
+	    {1,2},{3,4},{5,6},{7,8}
+	]),
+    M0 = Map#{ "hi" => "hello", int => 3, <<"key">> => <<"value">>,
+                  4 => number, 18446744073709551629 => wat},
+    M1 = Map#{},
+    M2 = M1#{ "hi" => "hello", int => 3, <<"key">> => <<"value">>,
+              4 => number, 18446744073709551629 => wat},
+    M0 = M2,
+
+    #{ 4 := another_number, int := 3 } = M2#{ 4 => another_number },
+    ok.
+
+
+loop_match_and_update_literals_x_q(Map, []) -> Map;
+loop_match_and_update_literals_x_q(#{ q:=Q0, x:=X0,
+                                     #{ "one" => small, map => key } := "small map key 1" } = Map, [{X,Q}|Vs]) ->
+    loop_match_and_update_literals_x_q(Map#{q=>Q0+Q,x=>X0+X},Vs).
+
+
+t_update_map_expressions(Config) when is_list(Config) ->
+    M = maps:new(),
+    #{ a := 1 } = M#{a => 1},
+
+    #{ b := 2 } = (maps:new())#{ b => 2 },
+
+    #{ a :=42, b:=42, c:=42 } = (maps:from_list([{a,1},{b,2},{c,3}]))#{ a := 42, b := 42, c := 42 },
+    #{ "a" :=1, "b":=42, "c":=42 } = (maps:from_list([{"a",1},{"b",2}]))#{ "b" := 42, "c" => 42 },
+    Ks = lists:seq($a,$z),
+    #{ "aa" := {$a,$a}, "ac":=41, "dc":=42 } =
+        (maps:from_list([{[K1,K2],{K1,K2}}|| K1 <- Ks, K2 <- Ks]))#{ "ac" := 41, "dc" => 42 },
+
+    %% Error cases.
+    do_badmap(fun(T) ->
+		      {'EXIT',{{badmap,T},_}} =
+			  (catch (T)#{a:=42,b=>2})
+	      end),
+    ok.
+
+t_update_assoc(Config) when is_list(Config) ->
+    M0 = #{1=>a,2=>b,3.0=>c,4=>d,5=>e},
+
+    M1 = M0#{1=>42,2=>100,4=>[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:=100,3.0:=c,4.0:=[a,b,c]} = M0#{1.0=>float,1:=42,2.0=>wrong,2.0=>100,4.0=>[a,b,c]},
+
+    M2 = M0#{3.0=>new},
+    #{1:=a,2:=b,3.0:=new,4:=d,5:=e} = M2,
+    M2 = M0#{3.0:=wrong,3.0=>new},
+
+    %% Errors cases.
+    do_badmap(fun(T) ->
+		      {'EXIT',{{badmap,T},_}} =
+			  (catch T#{nonexisting=>val})
+	      end),
+    ok.
+
+
+t_update_assoc_large(Config) when is_list(Config) ->
+    M0 = #{ 10=>a0,20=>b0,30=>"c0","40"=>"d0",<<"50">>=>"e0",{["00"]}=>"10",
+               11=>a1,21=>b1,31=>"c1","41"=>"d1",<<"51">>=>"e1",{["01"]}=>"11",
+               12=>a2,22=>b2,32=>"c2","42"=>"d2",<<"52">>=>"e2",{["02"]}=>"12",
+               13=>a3,23=>b3,33=>"c3","43"=>"d3",<<"53">>=>"e3",{["03"]}=>"13",
+               14=>a4,24=>b4,34=>"c4","44"=>"d4",<<"54">>=>"e4",{["04"]}=>"14",
+
+               15=>a5,25=>b5,35=>"c5","45"=>"d5",<<"55">>=>"e5",{["05"]}=>"15",
+               16=>a6,26=>b6,36=>"c6","46"=>"d6",<<"56">>=>"e6",{["06"]}=>"16",
+               17=>a7,27=>b7,37=>"c7","47"=>"d7",<<"57">>=>"e7",{["07"]}=>"17",
+               18=>a8,28=>b8,38=>"c8","48"=>"d8",<<"58">>=>"e8",{["08"]}=>"18",
+               19=>a9,29=>b9,39=>"c9","49"=>"d9",<<"59">>=>"e9",{["09"]}=>"19",
+
+               10.0=>fa0,20.0=>fb0,30.0=>"fc0",
+               11.0=>fa1,21.0=>fb1,31.0=>"fc1",
+               12.0=>fa2,22.0=>fb2,32.0=>"fc2",
+               13.0=>fa3,23.0=>fb3,33.0=>"fc3",
+               14.0=>fa4,24.0=>fb4,34.0=>"fc4",
+
+               15.0=>fa5,25.0=>fb5,35.0=>"fc5",
+               16.0=>fa6,26.0=>fb6,36.0=>"fc6",
+               17.0=>fa7,27.0=>fb7,37.0=>"fc7",
+               18.0=>fa8,28.0=>fb8,38.0=>"fc8",
+               19.0=>fa9,29.0=>fb9,39.0=>"fc9",
+
+               #{ one => small, map => key } => "small map key 1",
+               #{ second => small, map => key } => "small map key 2",
+               #{ third => small, map => key } => "small map key 3",
+
+               #{ 10=>a0,20=>b0,30=>"c0","40"=>"d0",<<"50">>=>"e0",{["00"]}=>"10",
+                  11=>a1,21=>b1,31=>"c1","41"=>"d1",<<"51">>=>"e1",{["01"]}=>"11",
+                  12=>a2,22=>b2,32=>"c2","42"=>"d2",<<"52">>=>"e2",{["02"]}=>"12",
+                  13=>a3,23=>b3,33=>"c3","43"=>"d3",<<"53">>=>"e3",{["03"]}=>"13",
+                  14=>a4,24=>b4,34=>"c4","44"=>"d4",<<"54">>=>"e4",{["04"]}=>"14",
+
+                  15=>a5,25=>b5,35=>"c5","45"=>"d5",<<"55">>=>"e5",{["05"]}=>"15",
+                  16=>a6,26=>b6,36=>"c6","46"=>"d6",<<"56">>=>"e6",{["06"]}=>"16",
+                  17=>a7,27=>b7,37=>"c7","47"=>"d7",<<"57">>=>"e7",{["07"]}=>"17",
+                  18=>a8,28=>b8,38=>"c8","48"=>"d8",<<"58">>=>"e8",{["08"]}=>"18",
+                  19=>a9,29=>b9,39=>"c9","49"=>"d9",<<"59">>=>"e9",{["09"]}=>"19" } => "large map key 1",
+
+               #{ 10=>a0,20=>b0,30=>"c0","40"=>"d0",<<"50">>=>"e0",{["00"]}=>"10",
+                  11=>a1,21=>b1,31=>"c1","41"=>"d1",<<"51">>=>"e1",{["01"]}=>"11",
+                  12=>a2,22=>b2,32=>"c2","42"=>"d2",<<"52">>=>"e2",{["02"]}=>"12",
+                  13=>a3,23=>b3,33=>"c3","43"=>"d3",<<"53">>=>"e3",{["03"]}=>"13",
+                  14=>a4,24=>b4,34=>"c4","44"=>"d4",<<"54">>=>"e4",{["04"]}=>"14",
+
+                  15=>a5,25=>b5,35=>"c5","45"=>"d5",<<"55">>=>"e5",{["05"]}=>"15",
+                  k16=>a6,k26=>b6,k36=>"c6","46"=>"d6",<<"56">>=>"e6",{["06"]}=>"16",
+                  17=>a7,27=>b7,37=>"c7","47"=>"d7",<<"57">>=>"e7",{["07"]}=>"17",
+                  18=>a8,28=>b8,38=>"c8","48"=>"d8",<<"58">>=>"e8",{["08"]}=>"18",
+                  19=>a9,29=>b9,39=>"c9","49"=>"d9",<<"59">>=>"e9",{["09"]}=>"19" } => "large map key 2" },
+
+
+    M1 = M0#{1=>42,2=>100,4=>[a,b,c]},
+    #{1:=42,2:=100,10.0:=fa0,4:=[a,b,c],25:=b5} = M1,
+    #{ 10:=43, 24:=b4, 15:=a5, 35:="c5", 2.0:=100, 13.0:=fa3, 4.0:=[a,b,c]} =
+        M0#{1.0=>float,10:=43,2.0=>wrong,2.0=>100,4.0=>[a,b,c]},
+
+    M2 = M0#{13.0=>new},
+    #{10:=a0,20:=b0,13.0:=new,"40":="d0",<<"50">>:="e0"} = M2,
+    M2 = M0#{13.0:=wrong,13.0=>new},
+
+    ok.
+
+t_update_exact(Config) when is_list(Config) ->
+    M0 = #{1=>a,2=>b,3.0=>c,4=>d,5=>e},
+
+    M1 = M0#{1:=42,2:=100,4:=[a,b,c]},
+    #{1:=42,2:=100,3.0:=c,4:=[a,b,c],5:=e} = M1,
+    M1 = M0#{1:=wrong,1=>42,2=>wrong,2:=100,4:=[a,b,c]},
+
+    M2 = M0#{3.0:=new},
+    #{1:=a,2:=b,3.0:=new,4:=d,5:=e} = M2,
+    M2 = M0#{3.0=>wrong,3.0:=new},
+    true = M2 =/= M0#{3=>right,3.0:=new},
+    #{ 3 := right, 3.0 := new } = M0#{3=>right,3.0:=new},
+
+    M3 = #{ 1 => val},
+    #{1 := update2,1.0 := new_val4} = M3#{
+	1.0 => new_val1, 1 := update, 1=> update3,
+	1 := update2, 1.0 := new_val2, 1.0 => new_val3,
+	1.0 => new_val4 },
+
+    %% Errors cases.
+    do_badmap(fun(T) ->
+		      {'EXIT',{{badmap,T},_}} =
+			  (catch T#{nonexisting=>val})
+	      end),
+    Empty = #{},
+    {'EXIT',{{badkey,nonexisting},_}} = (catch Empty#{nonexisting:=val}),
+    {'EXIT',{{badkey,nonexisting},_}} = (catch M0#{nonexisting:=val}),
+    {'EXIT',{{badkey,1.0},_}} = (catch M0#{1.0:=v,1.0=>v2}),
+    {'EXIT',{{badkey,42},_}} = (catch M0#{42.0:=v,42:=v2}),
+    {'EXIT',{{badkey,42.0},_}} = (catch M0#{42=>v1,42.0:=v2,42:=v3}),
+
+    ok.
+
+t_update_exact_large(Config) when is_list(Config) ->
+    M0 = #{ 10=>a0,20=>b0,30=>"c0","40"=>"d0",<<"50">>=>"e0",{["00"]}=>"10",
+               11=>a1,21=>b1,31=>"c1","41"=>"d1",<<"51">>=>"e1",{["01"]}=>"11",
+               12=>a2,22=>b2,32=>"c2","42"=>"d2",<<"52">>=>"e2",{["02"]}=>"12",
+               13=>a3,23=>b3,33=>"c3","43"=>"d3",<<"53">>=>"e3",{["03"]}=>"13",
+               14=>a4,24=>b4,34=>"c4","44"=>"d4",<<"54">>=>"e4",{["04"]}=>"14",
+
+               15=>a5,25=>b5,35=>"c5","45"=>"d5",<<"55">>=>"e5",{["05"]}=>"15",
+               16=>a6,26=>b6,36=>"c6","46"=>"d6",<<"56">>=>"e6",{["06"]}=>"16",
+               17=>a7,27=>b7,37=>"c7","47"=>"d7",<<"57">>=>"e7",{["07"]}=>"17",
+               18=>a8,28=>b8,38=>"c8","48"=>"d8",<<"58">>=>"e8",{["08"]}=>"18",
+               19=>a9,29=>b9,39=>"c9","49"=>"d9",<<"59">>=>"e9",{["09"]}=>"19",
+
+               10.0=>fa0,20.0=>fb0,30.0=>"fc0",
+               11.0=>fa1,21.0=>fb1,31.0=>"fc1",
+               12.0=>fa2,22.0=>fb2,32.0=>"fc2",
+               13.0=>fa3,23.0=>fb3,33.0=>"fc3",
+               14.0=>fa4,24.0=>fb4,34.0=>"fc4",
+
+               15.0=>fa5,25.0=>fb5,35.0=>"fc5",
+               16.0=>fa6,26.0=>fb6,36.0=>"fc6",
+               17.0=>fa7,27.0=>fb7,37.0=>"fc7",
+               18.0=>fa8,28.0=>fb8,38.0=>"fc8",
+               19.0=>fa9,29.0=>fb9,39.0=>"fc9",
+
+               #{ one => small, map => key } => "small map key 1",
+               #{ second => small, map => key } => "small map key 2",
+               #{ third => small, map => key } => "small map key 3",
+
+               #{ 10=>a0,20=>b0,30=>"c0","40"=>"d0",<<"50">>=>"e0",{["00"]}=>"10",
+                  11=>a1,21=>b1,31=>"c1","41"=>"d1",<<"51">>=>"e1",{["01"]}=>"11",
+                  12=>a2,22=>b2,32=>"c2","42"=>"d2",<<"52">>=>"e2",{["02"]}=>"12",
+                  13=>a3,23=>b3,33=>"c3","43"=>"d3",<<"53">>=>"e3",{["03"]}=>"13",
+                  14=>a4,24=>b4,34=>"c4","44"=>"d4",<<"54">>=>"e4",{["04"]}=>"14",
+
+                  15=>a5,25=>b5,35=>"c5","45"=>"d5",<<"55">>=>"e5",{["05"]}=>"15",
+                  16=>a6,26=>b6,36=>"c6","46"=>"d6",<<"56">>=>"e6",{["06"]}=>"16",
+                  17=>a7,27=>b7,37=>"c7","47"=>"d7",<<"57">>=>"e7",{["07"]}=>"17",
+                  18=>a8,28=>b8,38=>"c8","48"=>"d8",<<"58">>=>"e8",{["08"]}=>"18",
+                  19=>a9,29=>b9,39=>"c9","49"=>"d9",<<"59">>=>"e9",{["09"]}=>"19" } => "large map key 1",
+
+               #{ 10=>a0,20=>b0,30=>"c0","40"=>"d0",<<"50">>=>"e0",{["00"]}=>"10",
+                  11=>a1,21=>b1,31=>"c1","41"=>"d1",<<"51">>=>"e1",{["01"]}=>"11",
+                  12=>a2,22=>b2,32=>"c2","42"=>"d2",<<"52">>=>"e2",{["02"]}=>"12",
+                  13=>a3,23=>b3,33=>"c3","43"=>"d3",<<"53">>=>"e3",{["03"]}=>"13",
+                  14=>a4,24=>b4,34=>"c4","44"=>"d4",<<"54">>=>"e4",{["04"]}=>"14",
+
+                  15=>a5,25=>b5,35=>"c5","45"=>"d5",<<"55">>=>"e5",{["05"]}=>"15",
+                  k16=>a6,k26=>b6,k36=>"c6","46"=>"d6",<<"56">>=>"e6",{["06"]}=>"16",
+                  17=>a7,27=>b7,37=>"c7","47"=>"d7",<<"57">>=>"e7",{["07"]}=>"17",
+                  18=>a8,28=>b8,38=>"c8","48"=>"d8",<<"58">>=>"e8",{["08"]}=>"18",
+                  19=>a9,29=>b9,39=>"c9","49"=>"d9",<<"59">>=>"e9",{["09"]}=>"19" } => "large map key 2" },
+
+
+    M1 = M0#{10:=42,<<"55">>:=100,10.0:=[a,b,c]},
+    #{ 10:=42,<<"55">>:=100,{["05"]}:="15",10.0:=[a,b,c],
+       #{ 10=>a0,20=>b0,30=>"c0","40"=>"d0",<<"50">>=>"e0",{["00"]}=>"10",
+          11=>a1,21=>b1,31=>"c1","41"=>"d1",<<"51">>=>"e1",{["01"]}=>"11",
+          12=>a2,22=>b2,32=>"c2","42"=>"d2",<<"52">>=>"e2",{["02"]}=>"12",
+          13=>a3,23=>b3,33=>"c3","43"=>"d3",<<"53">>=>"e3",{["03"]}=>"13",
+          14=>a4,24=>b4,34=>"c4","44"=>"d4",<<"54">>=>"e4",{["04"]}=>"14",
+
+          15=>a5,25=>b5,35=>"c5","45"=>"d5",<<"55">>=>"e5",{["05"]}=>"15",
+          16=>a6,26=>b6,36=>"c6","46"=>"d6",<<"56">>=>"e6",{["06"]}=>"16",
+          17=>a7,27=>b7,37=>"c7","47"=>"d7",<<"57">>=>"e7",{["07"]}=>"17",
+          18=>a8,28=>b8,38=>"c8","48"=>"d8",<<"58">>=>"e8",{["08"]}=>"18",
+          19=>a9,29=>b9,39=>"c9","49"=>"d9",<<"59">>=>"e9",{["09"]}=>"19" } := "large map key 1" } = M1,
+
+    M1 = M0#{10:=wrong,10=>42,<<"55">>=>wrong,<<"55">>:=100,10.0:=[a,b,c]},
+
+    M2 = M0#{13.0:=new},
+    #{10:=a0,20:=b0,13.0:=new} = M2,
+    M2 = M0#{13.0=>wrong,13.0:=new},
+
+    %% Errors cases.
+    {'EXIT',{{badkey,nonexisting},_}} = (catch M0#{nonexisting:=val}),
+    {'EXIT',{{badkey,1.0},_}} = (catch M0#{1.0:=v,1.0=>v2}),
+    {'EXIT',{{badkey,42},_}} = (catch M0#{42.0:=v,42:=v2}),
+    {'EXIT',{{badkey,42.0},_}} = (catch M0#{42=>v1,42.0:=v2,42:=v3}),
+
+    ok.
+
+t_update_deep(Config) when is_list(Config) ->
+    N = 250000,
+    M0 = maps:from_list([{integer_to_list(I),a}||I<-lists:seq(1,N)]),
+    #{ "1" := a, "10" := a, "100" := a, "1000" := a, "10000" := a } = M0,
+
+    M1 = M0#{ "1" := b, "10" := b, "100" := b, "1000" := b, "10000" := b },
+    #{ "1" := a, "10" := a, "100" := a, "1000" := a, "10000" := a } = M0,
+    #{ "1" := b, "10" := b, "100" := b, "1000" := b, "10000" := b } = M1,
+
+    M2 = M0#{ "1" => c, "10" => c, "100" => c, "1000" => c, "10000" => c },
+    #{ "1" := a, "10" := a, "100" := a, "1000" := a, "10000" := a } = M0,
+    #{ "1" := b, "10" := b, "100" := b, "1000" := b, "10000" := b } = M1,
+    #{ "1" := c, "10" := c, "100" := c, "1000" := c, "10000" := c } = M2,
+
+    M3 = M2#{ "n1" => d, "n10" => d, "n100" => d, "n1000" => d, "n10000" => d },
+    #{  "1" := a,  "10" := a,  "100" := a,  "1000" := a,  "10000" := a } = M0,
+    #{  "1" := b,  "10" := b,  "100" := b,  "1000" := b,  "10000" := b } = M1,
+    #{  "1" := c,  "10" := c,  "100" := c,  "1000" := c,  "10000" := c } = M2,
+    #{  "1" := c,  "10" := c,  "100" := c,  "1000" := c,  "10000" := c } = M3,
+    #{ "n1" := d, "n10" := d, "n100" := d, "n1000" := d, "n10000" := d } = M3,
+    ok.
+
+t_guard_bifs(Config) when is_list(Config) ->
+    true   = map_guard_head(#{a=>1}),
+    false  = map_guard_head([]),
+    true   = map_guard_body(#{a=>1}),
+    false  = map_guard_body({}),
+    true   = map_guard_pattern(#{a=>1, <<"hi">> => "hi" }),
+    false  = map_guard_pattern("list"),
+    ok.
+
+map_guard_head(M) when is_map(M) -> true;
+map_guard_head(_) -> false.
+
+map_guard_body(M) -> is_map(M).
+
+map_guard_pattern(#{}) -> true;
+map_guard_pattern(_)   -> false.
+
+t_guard_sequence(Config) when is_list(Config) ->
+	{1, "a"} = map_guard_sequence_1(#{seq=>1,val=>"a"}),
+	{2, "b"} = map_guard_sequence_1(#{seq=>2,val=>"b"}),
+	{3, "c"} = map_guard_sequence_1(#{seq=>3,val=>"c"}),
+	{4, "d"} = map_guard_sequence_1(#{seq=>4,val=>"d"}),
+	{5, "e"} = map_guard_sequence_1(#{seq=>5,val=>"e"}),
+
+	{1,M1}       = map_guard_sequence_2(M1 = #{a=>3}),
+	{2,M2}       = map_guard_sequence_2(M2 = #{a=>4, b=>4}),
+	{3,gg,M3}    = map_guard_sequence_2(M3 = #{a=>gg, b=>4}),
+	{4,sc,sc,M4} = map_guard_sequence_2(M4 = #{a=>sc, b=>3, c=>sc2}),
+	{5,kk,kk,M5} = map_guard_sequence_2(M5 = #{a=>kk, b=>other, c=>sc2}),
+
+	%% error case
+	{'EXIT',{function_clause,_}} = (catch map_guard_sequence_1(#{seq=>6,val=>"e"})),
+	{'EXIT',{function_clause,_}} = (catch map_guard_sequence_2(#{b=>5})),
+	ok.
+
+t_guard_sequence_large(Config) when is_list(Config) ->
+    M0 = #{ 10=>a0,20=>b0,30=>"c0","40"=>"d0",<<"50">>=>"e0",{["00",03]}=>"10",
+               11=>a1,21=>b1,31=>"c1","41"=>"d1",<<"51">>=>"e1",{["01",03]}=>"11",
+               12=>a2,22=>b2,32=>"c2","42"=>"d2",<<"52">>=>"e2",{["02",03]}=>"12",
+               13=>a3,23=>b3,33=>"c3","43"=>"d3",<<"53">>=>"e3",{["03",03]}=>"13",
+               14=>a4,24=>b4,34=>"c4","44"=>"d4",<<"54">>=>"e4",{["04",03]}=>"14",
+
+               15=>a5,25=>b5,35=>"c5","45"=>"d5",<<"55">>=>"e5",{["05",03]}=>"15",
+               16=>a6,26=>b6,36=>"c6","46"=>"d6",<<"56">>=>"e6",{["06",03]}=>"16",
+               17=>a7,27=>b7,37=>"c7","47"=>"d7",<<"57">>=>"e7",{["07",03]}=>"17",
+               18=>a8,28=>b8,38=>"c8","48"=>"d8",<<"58">>=>"e8",{["08",03]}=>"18",
+               19=>a9,29=>b9,39=>"c9","49"=>"d9",<<"59">>=>"e9",{["09",03]}=>"19",
+
+               10.0=>fa0,20.0=>fb0,30.0=>"fc0",
+               11.0=>fa1,21.0=>fb1,31.0=>"fc1",
+               12.0=>fa2,22.0=>fb2,32.0=>"fc2",
+               13.0=>fa3,23.0=>fb3,33.0=>"fc3",
+               14.0=>fa4,24.0=>fb4,34.0=>"fc4",
+
+               15.0=>fa5,25.0=>fb5,35.0=>"fc5",
+               16.0=>fa6,26.0=>fb6,36.0=>"fc6",
+               17.0=>fa7,27.0=>fb7,37.0=>"fc7",
+               18.0=>fa8,28.0=>fb8,38.0=>"fc8",
+               19.0=>fa9,29.0=>fb9,39.0=>"fc9",
+
+               #{ one => small, map => key } => "small map key 1",
+               #{ second => small, map => key } => "small map key 2",
+               #{ third => small, map => key } => "small map key 3",
+
+               #{ 10=>a0,20=>b0,30=>"c0","40"=>"d0",<<"50">>=>"e0",{["00"]}=>"10",
+                  11=>a1,21=>b1,31=>"c1","41"=>"d1",<<"51">>=>"e1",{["01"]}=>"11",
+                  12=>a2,22=>b2,32=>"c2","42"=>"d2",<<"52">>=>"e2",{["02"]}=>"12",
+                  13=>a3,23=>b3,33=>"c3","43"=>"d3",<<"53">>=>"e3",{["03"]}=>"13",
+                  14=>a4,24=>b4,34=>"c4","44"=>"d4",<<"54">>=>"e4",{["04"]}=>"14",
+
+                  15=>a5,25=>b5,35=>"c5","45"=>"d5",<<"55">>=>"e5",{["05"]}=>"15",
+                  16=>a6,26=>b6,36=>"c6","46"=>"d6",<<"56">>=>"e6",{["06"]}=>"16",
+                  17=>a7,27=>b7,37=>"c7","47"=>"d7",<<"57">>=>"e7",{["07"]}=>"17",
+                  18=>a8,28=>b8,38=>"c8","48"=>"d8",<<"58">>=>"e8",{["08"]}=>"18",
+                  19=>a9,29=>b9,39=>"c9","49"=>"d9",<<"59">>=>"e9",{["09"]}=>"19" } => "large map key 1",
+
+               #{ 10=>a0,20=>b0,30=>"c0","40"=>"d0",<<"50">>=>"e0",{["00"]}=>"10",
+                  11=>a1,21=>b1,31=>"c1","41"=>"d1",<<"51">>=>"e1",{["01"]}=>"11",
+                  12=>a2,22=>b2,32=>"c2","42"=>"d2",<<"52">>=>"e2",{["02"]}=>"12",
+                  13=>a3,23=>b3,33=>"c3","43"=>"d3",<<"53">>=>"e3",{["03"]}=>"13",
+                  14=>a4,24=>b4,34=>"c4","44"=>"d4",<<"54">>=>"e4",{["04"]}=>"14",
+
+                  15=>a5,25=>b5,35=>"c5","45"=>"d5",<<"55">>=>"e5",{["05"]}=>"15",
+                  k16=>a6,k26=>b6,k36=>"c6","46"=>"d6",<<"56">>=>"e6",{["06"]}=>"16",
+                  17=>a7,27=>b7,37=>"c7","47"=>"d7",<<"57">>=>"e7",{["07"]}=>"17",
+                  18=>a8,28=>b8,38=>"c8","48"=>"d8",<<"58">>=>"e8",{["08"]}=>"18",
+                  19=>a9,29=>b9,39=>"c9","49"=>"d9",<<"59">>=>"e9",{["09"]}=>"19" } => "large map key 2" },
+
+	{1, "a"} = map_guard_sequence_1(M0#{seq=>1,val=>"a"}),
+	{2, "b"} = map_guard_sequence_1(M0#{seq=>2,val=>"b"}),
+	{3, "c"} = map_guard_sequence_1(M0#{seq=>3,val=>"c"}),
+	{4, "d"} = map_guard_sequence_1(M0#{seq=>4,val=>"d"}),
+	{5, "e"} = map_guard_sequence_1(M0#{seq=>5,val=>"e"}),
+
+	{1,M1}       = map_guard_sequence_2(M1 = M0#{a=>3}),
+	{2,M2}       = map_guard_sequence_2(M2 = M0#{a=>4, b=>4}),
+	{3,gg,M3}    = map_guard_sequence_2(M3 = M0#{a=>gg, b=>4}),
+	{4,sc,sc,M4} = map_guard_sequence_2(M4 = M0#{a=>sc, b=>3, c=>sc2}),
+	{5,kk,kk,M5} = map_guard_sequence_2(M5 = M0#{a=>kk, b=>other, c=>sc2}),
+
+	{'EXIT',{function_clause,_}} = (catch map_guard_sequence_1(M0#{seq=>6,val=>"e"})),
+	{'EXIT',{function_clause,_}} = (catch map_guard_sequence_2(M0#{b=>5})),
+        ok.
+
+
+map_guard_sequence_1(#{seq:=1=Seq, val:=Val}) -> {Seq,Val};
+map_guard_sequence_1(#{seq:=2=Seq, val:=Val}) -> {Seq,Val};
+map_guard_sequence_1(#{seq:=3=Seq, val:=Val}) -> {Seq,Val};
+map_guard_sequence_1(#{seq:=4=Seq, val:=Val}) -> {Seq,Val};
+map_guard_sequence_1(#{seq:=5=Seq, val:=Val}) -> {Seq,Val}.
+
+map_guard_sequence_2(#{ a:=3 }=M) -> {1, M};
+map_guard_sequence_2(#{ a:=4 }=M) -> {2, M};
+map_guard_sequence_2(#{ a:=X, a:=X, b:=4 }=M) -> {3,X,M};
+map_guard_sequence_2(#{ a:=X, a:=Y, b:=3 }=M) when X =:= Y -> {4,X,Y,M};
+map_guard_sequence_2(#{ a:=X, a:=Y }=M) when X =:= Y -> {5,X,Y,M}.
+
+
+t_guard_update(Config) when is_list(Config) ->
+    error  = map_guard_update(#{},#{}),
+    first  = map_guard_update(#{}, #{x=>first}),
+    second = map_guard_update(#{y=>old}, #{x=>second,y=>old}),
+    ok.
+
+t_guard_update_large(Config) when is_list(Config) ->
+    M0 = #{ 70=>a0,80=>b0,90=>"c0","40"=>"d0",<<"50">>=>"e0",{["00",03]}=>"10",
+               71=>a1,81=>b1,91=>"c1","41"=>"d1",<<"51">>=>"e1",{["01",03]}=>"11",
+               72=>a2,82=>b2,92=>"c2","42"=>"d2",<<"52">>=>"e2",{["02",03]}=>"12",
+               73=>a3,83=>b3,93=>"c3","43"=>"d3",<<"53">>=>"e3",{["03",03]}=>"13",
+               74=>a4,84=>b4,94=>"c4","44"=>"d4",<<"54">>=>"e4",{["04",03]}=>"14",
+
+               75=>a5,85=>b5,95=>"c5","45"=>"d5",<<"55">>=>"e5",{["05",03]}=>"15",
+               76=>a6,86=>b6,96=>"c6","46"=>"d6",<<"56">>=>"e6",{["06",03]}=>"16",
+               77=>a7,87=>b7,97=>"c7","47"=>"d7",<<"57">>=>"e7",{["07",03]}=>"17",
+               78=>a8,88=>b8,98=>"c8","48"=>"d8",<<"58">>=>"e8",{["08",03]}=>"18",
+               79=>a9,89=>b9,99=>"c9","49"=>"d9",<<"59">>=>"e9",{["09",03]}=>"19",
+
+               70.0=>fa0,80.0=>fb0,90.0=>"fc0",
+               71.0=>fa1,81.0=>fb1,91.0=>"fc1",
+               72.0=>fa2,82.0=>fb2,92.0=>"fc2",
+               73.0=>fa3,83.0=>fb3,93.0=>"fc3",
+               74.0=>fa4,84.0=>fb4,94.0=>"fc4",
+
+               75.0=>fa5,85.0=>fb5,95.0=>"fc5",
+               76.0=>fa6,86.0=>fb6,96.0=>"fc6",
+               77.0=>fa7,87.0=>fb7,97.0=>"fc7",
+               78.0=>fa8,88.0=>fb8,98.0=>"fc8",
+               79.0=>fa9,89.0=>fb9,99.0=>"fc9",
+
+               #{ one => small, map => key } => "small map key 1",
+               #{ second => small, map => key } => "small map key 2",
+               #{ third => small, map => key } => "small map key 3",
+
+               #{ 10=>a0,20=>b0,30=>"c0","40"=>"d0",<<"50">>=>"e0",{["00"]}=>"10",
+                  11=>a1,21=>b1,31=>"c1","41"=>"d1",<<"51">>=>"e1",{["01"]}=>"11",
+                  12=>a2,22=>b2,32=>"c2","42"=>"d2",<<"52">>=>"e2",{["02"]}=>"12",
+                  13=>a3,23=>b3,33=>"c3","43"=>"d3",<<"53">>=>"e3",{["03"]}=>"13",
+                  14=>a4,24=>b4,34=>"c4","44"=>"d4",<<"54">>=>"e4",{["04"]}=>"14",
+
+                  15=>a5,25=>b5,35=>"c5","45"=>"d5",<<"55">>=>"e5",{["05"]}=>"15",
+                  16=>a6,26=>b6,36=>"c6","46"=>"d6",<<"56">>=>"e6",{["06"]}=>"16",
+                  17=>a7,27=>b7,37=>"c7","47"=>"d7",<<"57">>=>"e7",{["07"]}=>"17",
+                  18=>a8,28=>b8,38=>"c8","48"=>"d8",<<"58">>=>"e8",{["08"]}=>"18",
+                  19=>a9,29=>b9,39=>"c9","49"=>"d9",<<"59">>=>"e9",{["09"]}=>"19" } => "large map key 1",
+
+               #{ 10=>a0,20=>b0,30=>"c0","40"=>"d0",<<"50">>=>"e0",{["00"]}=>"10",
+                  11=>a1,21=>b1,31=>"c1","41"=>"d1",<<"51">>=>"e1",{["01"]}=>"11",
+                  12=>a2,22=>b2,32=>"c2","42"=>"d2",<<"52">>=>"e2",{["02"]}=>"12",
+                  13=>a3,23=>b3,33=>"c3","43"=>"d3",<<"53">>=>"e3",{["03"]}=>"13",
+                  14=>a4,24=>b4,34=>"c4","44"=>"d4",<<"54">>=>"e4",{["04"]}=>"14",
+
+                  15=>a5,25=>b5,35=>"c5","45"=>"d5",<<"55">>=>"e5",{["05"]}=>"15",
+                  k16=>a6,k26=>b6,k36=>"c6","46"=>"d6",<<"56">>=>"e6",{["06"]}=>"16",
+                  17=>a7,27=>b7,37=>"c7","47"=>"d7",<<"57">>=>"e7",{["07"]}=>"17",
+                  18=>a8,28=>b8,38=>"c8","48"=>"d8",<<"58">>=>"e8",{["08"]}=>"18",
+                  19=>a9,29=>b9,39=>"c9","49"=>"d9",<<"59">>=>"e9",{["09"]}=>"19" } => "large map key 2" },
+
+
+    error  = map_guard_update(M0#{},M0#{}),
+    first  = map_guard_update(M0#{},M0#{x=>first}),
+    second = map_guard_update(M0#{y=>old}, M0#{x=>second,y=>old}),
+    ok.
+
+
+map_guard_update(M1, M2) when M1#{x=>first}  =:= M2 -> first;
+map_guard_update(M1, M2) when M1#{x=>second} =:= M2 -> second;
+map_guard_update(_, _) -> error.
+
+t_guard_receive(Config) when is_list(Config) ->
+    M0  = #{ id => 0 },
+    Pid = spawn_link(fun() -> guard_receive_loop() end),
+    Big = 36893488147419103229,
+    B1  = <<"some text">>,
+    B2  = <<"was appended">>,
+    B3  = <<B1/binary, B2/binary>>,
+
+    #{id:=1, res:=Big} = M1 = call(Pid, M0#{op=>sub,in=>{1 bsl 65, 3}}),
+    #{id:=2, res:=26}  = M2 = call(Pid, M1#{op=>idiv,in=>{53,2}}),
+    #{id:=3, res:=832} = M3 = call(Pid, M2#{op=>imul,in=>{26,32}}),
+    #{id:=4, res:=4}   = M4 = call(Pid, M3#{op=>add,in=>{1,3}}),
+    #{id:=5, res:=Big} = M5 = call(Pid, M4#{op=>sub,in=>{1 bsl 65, 3}}),
+    #{id:=6, res:=B3}  = M6 = call(Pid, M5#{op=>"append",in=>{B1,B2}}),
+    #{id:=7, res:=4}   = _  = call(Pid, M6#{op=>add,in=>{1,3}}),
+
+
+    %% update old maps and check id update
+    #{id:=2, res:=B3} = call(Pid, M1#{op=>"append",in=>{B1,B2}}),
+    #{id:=5, res:=99} = call(Pid, M4#{op=>add,in=>{33, 66}}),
+
+    %% cleanup
+    done = call(Pid, done),
+    ok.
+
+-define(t_guard_receive_large_procs, 1500).
+
+t_guard_receive_large(Config) when is_list(Config) ->
+    M = lists:foldl(fun(_,#{procs := Ps } = M) ->
+                            M#{ procs := Ps#{ spawn_link(fun() -> grecv_loop() end) => 0 }}
+                    end, #{procs => #{}, done => 0}, lists:seq(1,?t_guard_receive_large_procs)),
+    lists:foreach(fun(Pid) ->
+                          Pid ! {self(), hello}
+                  end, maps:keys(maps:get(procs,M))),
+    ok = guard_receive_large_loop(M),
+    ok.
+
+guard_receive_large_loop(#{done := ?t_guard_receive_large_procs}) ->
+    ok;
+guard_receive_large_loop(M) ->
+    receive
+        #{pid := Pid, msg := hello} ->
+            case M of
+                #{done := Count, procs := #{Pid := 150}} ->
+                    Pid ! {self(), done},
+                    guard_receive_large_loop(M#{done := Count + 1});
+                #{procs := #{Pid := Count} = Ps} ->
+                    Pid ! {self(), hello},
+                    guard_receive_large_loop(M#{procs := Ps#{Pid := Count + 1}})
+            end
+    end.
+
+grecv_loop() ->
+    receive
+        {_, done} ->
+            ok;
+        {Pid, hello} ->
+            Pid ! #{pid=>self(), msg=>hello},
+            grecv_loop()
+    end.
+
+call(Pid, M) ->
+    Pid ! {self(), M}, receive {Pid, Res} -> Res end.
+
+guard_receive_loop() ->
+    receive
+	{Pid, #{ id:=Id, op:="append", in:={X,Y}}=M} when is_binary(X), is_binary(Y) ->
+	    Pid ! {self(), M#{ id=>Id+1, res=><<X/binary,Y/binary>>}},
+	    guard_receive_loop();
+	{Pid, #{ id:=Id, op:=add, in:={X,Y}}} ->
+	    Pid ! {self(), #{ id=>Id+1, res=>X+Y}},
+	    guard_receive_loop();
+	{Pid, #{ id:=Id, op:=sub,  in:={X,Y}}=M} ->
+	    Pid ! {self(), M#{ id=>Id+1, res=>X-Y}},
+	    guard_receive_loop();
+	{Pid, #{ id:=Id, op:=idiv, in:={X,Y}}=M} ->
+	    Pid ! {self(), M#{ id=>Id+1, res=>X div Y}},
+	    guard_receive_loop();
+	{Pid, #{ id:=Id, op:=imul, in:={X,Y}}=M} ->
+	    Pid ! {self(), M#{ id=>Id+1, res=>X * Y}},
+	    guard_receive_loop();
+	{Pid, done} ->
+	    Pid ! {self(), done};
+	{Pid, Other} ->
+	    Pid ! {error, Other},
+	    guard_receive_loop()
+    end.
+
+
+t_list_comprehension(Config) when is_list(Config) ->
+    [#{k:=1},#{k:=2},#{k:=3}] = [#{k=>I} || I <- [1,2,3]],
+
+    Ks = lists:seq($a,$z),
+    Ms = [#{[K1,K2]=>{K1,K2}} || K1 <- Ks, K2 <- Ks],
+    [#{"aa" := {$a,$a}},#{"ab":={$a,$b}}|_] = Ms,
+    [#{"zz" := {$z,$z}},#{"zy":={$z,$y}}|_] = lists:reverse(Ms),
+    ok.
+
+t_guard_fun(Config) when is_list(Config) ->
+    F1 = fun
+	    (#{s:=v,v:=V})     -> {v,V};
+	    (#{s:=t,v:={V,V}}) -> {t,V};
+	    (#{s:=l,v:=[V,V]}) -> {l,V}
+    end,
+    
+    F2 = fun
+	    (#{s:=T,v:={V,V}}) -> {T,V};
+	    (#{s:=T,v:=[V,V]}) -> {T,V};
+	    (#{s:=T,v:=V})     -> {T,V}
+    end,
+    V = <<"hi">>,
+
+    {v,V} = F1(#{s=>v,v=>V}),
+    {t,V} = F1(#{s=>t,v=>{V,V}}),
+    {l,V} = F1(#{s=>l,v=>[V,V]}),
+
+    {v,V} = F2(#{s=>v,v=>V}),
+    {t,V} = F2(#{s=>t,v=>{V,V}}),
+    {l,V} = F2(#{s=>l,v=>[V,V]}),
+
+    %% error case
+    {'EXIT', {function_clause,[{?MODULE,_,[#{s:=none,v:=none}],_}|_]}} = (catch F1(#{s=>none,v=>none})),
+    ok.
+
+
+t_map_sort_literals(Config) when is_list(Config) ->
+    % test relation
+
+    %% size order
+    true  = #{ a => 1, b => 2} < #{ a => 1, b => 1, c => 1},
+    true  = #{ b => 1, a => 1} < #{ c => 1, a => 1, b => 1},
+    false = #{ c => 1, b => 1, a => 1} < #{ c => 1, a => 1},
+
+    %% key order
+    true  = #{ a => 1 } < #{ b => 1},
+    false = #{ b => 1 } < #{ a => 1},
+    true  = #{ a => 1, b => 1, c => 1 } < #{ b => 1, c => 1, d => 1},
+    true  = #{ b => 1, c => 1, d => 1 } > #{ a => 1, b => 1, c => 1},
+    true  = #{ c => 1, b => 1, a => 1 } < #{ b => 1, c => 1, d => 1},
+    true  = #{ "a" => 1 } < #{ <<"a">> => 1},
+    false = #{ <<"a">> => 1 } < #{ "a" => 1},
+    true  = #{ 1 => 1 } < #{ 1.0 => 1},
+    false = #{ 1.0 => 1 } < #{ 1 => 1},
+
+    %% value order
+    true  = #{ a => 1 } < #{ a => 2},
+    false = #{ a => 2 } < #{ a => 1},
+    false = #{ a => 2, b => 1 } < #{ a => 1, b => 3},
+    true  = #{ a => 1, b => 1 } < #{ a => 1, b => 3},
+    false = #{ a => 1 } < #{ a => 1.0},
+    false = #{ a => 1.0 } < #{ a => 1},
+
+    true  = #{ "a" => "hi", b => 134 } == #{ b => 134,"a" => "hi"},
+
+    %% large maps
+
+    M = maps:from_list([{I,I}||I <- lists:seq(1,500)]),
+
+    %% size order
+    true  = M#{ a => 1, b => 2} < M#{ a => 1, b => 1, c => 1},
+    true  = M#{ b => 1, a => 1} < M#{ c => 1, a => 1, b => 1},
+    false = M#{ c => 1, b => 1, a => 1} < M#{ c => 1, a => 1},
+
+    %% key order
+    true  = M#{ a => 1 } < M#{ b => 1},
+    false = M#{ b => 1 } < M#{ a => 1},
+    true  = M#{ a => 1, b => 1, c => 1 } < M#{ b => 1, c => 1, d => 1},
+    true  = M#{ b => 1, c => 1, d => 1 } > M#{ a => 1, b => 1, c => 1},
+    true  = M#{ c => 1, b => 1, a => 1 } < M#{ b => 1, c => 1, d => 1},
+    true  = M#{ "a" => 1 } < M#{ <<"a">> => 1},
+    false = M#{ <<"a">> => 1 } < #{ "a" => 1},
+    true  = M#{ 1 => 1 } < maps:remove(1,M#{ 1.0 => 1}),
+    false = M#{ 1.0 => 1 } < M#{ 1 => 1},
+
+    %% value order
+    true  = M#{ a => 1 } < M#{ a => 2},
+    false = M#{ a => 2 } < M#{ a => 1},
+    false = M#{ a => 2, b => 1 } < M#{ a => 1, b => 3},
+    true  = M#{ a => 1, b => 1 } < M#{ a => 1, b => 3},
+    false = M#{ a => 1 } < M#{ a => 1.0},
+    false = M#{ a => 1.0 } < M#{ a => 1},
+
+    true  = M#{ "a" => "hi", b => 134 } == M#{ b => 134,"a" => "hi"},
+
+    %% lists:sort
+
+    SortVs = [#{"a"=>1},#{a=>2},#{1=>3},#{<<"a">>=>4}],
+    [#{1:=ok},#{a:=ok},#{"a":=ok},#{<<"a">>:=ok}] = lists:sort([#{"a"=>ok},#{a=>ok},#{1=>ok},#{<<"a">>=>ok}]),
+    [#{1:=3},#{a:=2},#{"a":=1},#{<<"a">>:=4}] = lists:sort(SortVs),
+    [#{1:=3},#{a:=2},#{"a":=1},#{<<"a">>:=4}] = lists:sort(lists:reverse(SortVs)),
+    ok.
+
+t_map_equal(Config) when is_list(Config) ->
+    true  = #{} =:= #{},
+    false = #{} =:= #{a=>1},
+    false = #{a=>1} =:= #{},
+    true  = #{ "a" => "hi", b => 134 } =:= #{ b => 134,"a" => "hi"},
+
+    false = #{ a => 1 } =:= #{ a => 2},
+    false = #{ a => 2 } =:= #{ a => 1},
+    false = #{ a => 2, b => 1 } =:= #{ a => 1, b => 3},
+    false = #{ a => 1, b => 1 } =:= #{ a => 1, b => 3},
+
+    true = #{ a => 1 } =:= #{ a => 1},
+    true = #{ "a" => 2 } =:= #{ "a" => 2},
+    true = #{ "a" => 2, b => 3 } =:= #{ "a" => 2, b => 3},
+    true = #{ a => 1, b => 3, c => <<"wat">> } =:= #{ a => 1, b => 3, c=><<"wat">>},
+    ok.
+
+
+t_map_compare(Config) when is_list(Config) ->
+    Seed = {erlang:monotonic_time(),
+	    erlang:time_offset(),
+	    erlang:unique_integer()},
+    io:format("seed = ~p\n", [Seed]),
+    random:seed(Seed),
+    repeat(100, fun(_) -> float_int_compare() end, []),
+    repeat(100, fun(_) -> recursive_compare() end, []),
+    ok.
+
+float_int_compare() ->
+    Terms = numeric_keys(3),
+    %%io:format("Keys to use: ~p\n", [Terms]),
+    Pairs = lists:map(fun(K) -> list_to_tuple([{K,V} || V <- Terms]) end, Terms),
+    lists:foreach(fun(Size) ->
+			  MapGen = fun() -> map_gen(list_to_tuple(Pairs), Size) end,
+			  repeat(100, fun do_compare/1, [MapGen, MapGen])
+		  end,
+		  lists:seq(1,length(Terms))),
+    ok.
+
+numeric_keys(N) ->
+    lists:foldl(fun(_,Acc) ->
+			Int = random:uniform(N*4) - N*2,
+			Float = float(Int),
+			[Int, Float, Float * 0.99, Float * 1.01 | Acc]
+		end,
+		[],
+		lists:seq(1,N)).
+
+
+repeat(0, _, _) ->
+    ok;
+repeat(N, Fun, Arg) ->
+    Fun(Arg),
+    repeat(N-1, Fun, Arg).
+
+copy_term(T) ->
+    Papa = self(),
+    P = spawn_link(fun() -> receive Msg -> Papa ! Msg end end),
+    P ! T,
+    receive R -> R end.
+
+do_compare([Gen1, Gen2]) ->
+    M1 = Gen1(),
+    M2 = Gen2(),
+    %%io:format("Maps to compare: ~p AND ~p\n", [M1, M2]),
+    C = (M1 < M2),
+    Erlang = maps_lessthan(M1, M2),
+    C = Erlang,
+    ?CHECK(M1==M1, M1),
+
+    %% Change one key from int to float (or vice versa) and check compare
+    ML1 = maps:to_list(M1),
+    {K1,V1} = lists:nth(random:uniform(length(ML1)), ML1),
+    case K1 of
+	I when is_integer(I) ->
+	    case maps:find(float(I),M1) of
+		error ->
+		    M1f = maps:remove(I, maps:put(float(I), V1, M1)),
+		    ?CHECK(M1f > M1, [M1f, M1]);
+		_ -> ok
+	    end;
+
+	F when is_float(F), round(F) == F ->
+	    case maps:find(round(F),M1) of
+		error ->
+		    M1i = maps:remove(F, maps:put(round(F), V1, M1)),
+		    ?CHECK(M1i < M1, [M1i, M1]);
+		_ -> ok
+	    end;
+
+	_ -> ok   % skip floats with decimals
+    end,
+
+    ?CHECK(M2 == M2, [M2]).
+
+
+maps_lessthan(M1, M2) ->
+  case {maps:size(M1),maps:size(M2)} of
+      {_S,_S} ->
+	  {K1,V1} = lists:unzip(term_sort(maps:to_list(M1))),
+	  {K2,V2} = lists:unzip(term_sort(maps:to_list(M2))),
+
+	  case erts_internal:cmp_term(K1,K2) of
+	      -1 -> true;
+	      0 -> (V1 < V2);
+	      1 -> false
+	  end;
+
+      {S1, S2} ->
+	  S1 < S2
+  end.
+
+term_sort(L) ->
+    lists:sort(fun(A,B) -> erts_internal:cmp_term(A,B) =< 0 end,
+	       L).
+
+
+cmp(T1, T2, Exact) when is_tuple(T1) and is_tuple(T2) ->
+    case {size(T1),size(T2)} of
+	{_S,_S} -> cmp(tuple_to_list(T1), tuple_to_list(T2), Exact);
+	{S1,S2} when S1 < S2 -> -1;
+	{S1,S2} when S1 > S2 -> 1
+    end;
+
+cmp([H1|T1], [H2|T2], Exact) ->
+    case cmp(H1,H2, Exact) of
+	0 -> cmp(T1,T2, Exact);
+	C -> C
+    end;
+
+cmp(M1, M2, Exact) when is_map(M1) andalso is_map(M2) ->
+    cmp_maps(M1,M2,Exact);
+cmp(M1, M2, Exact) ->
+    cmp_others(M1, M2, Exact).
+
+cmp_maps(M1, M2, Exact) ->
+    case {maps:size(M1),maps:size(M2)} of
+	{_S,_S} ->
+	    {K1,V1} = lists:unzip(term_sort(maps:to_list(M1))),
+	    {K2,V2} = lists:unzip(term_sort(maps:to_list(M2))),
+
+	    case cmp(K1, K2, true) of
+		0 -> cmp(V1, V2, Exact);
+		C -> C
+	    end;
+
+	{S1,S2} when S1 < S2 -> -1;
+	{S1,S2} when S1 > S2 -> 1
+    end.
+
+cmp_others(I, F, true) when is_integer(I), is_float(F) ->
+    -1;
+cmp_others(F, I, true) when is_float(F), is_integer(I) ->
+    1;
+cmp_others(T1, T2, _) ->
+    case {T1<T2, T1==T2} of
+	{true,false} -> -1;
+	{false,true} -> 0;
+	{false,false} -> 1
+    end.
+
+map_gen(Pairs, Size) ->
+    {_,L} = lists:foldl(fun(_, {Keys, Acc}) ->
+				KI = random:uniform(size(Keys)),
+				K = element(KI,Keys),
+				KV = element(random:uniform(size(K)), K),
+				{erlang:delete_element(KI,Keys), [KV | Acc]}
+			end,
+			{Pairs, []},
+			lists:seq(1,Size)),
+
+    maps:from_list(L).
+
+
+recursive_compare() ->
+    Leafs = {atom, 17, 16.9, 17.1, [], self(), spawn(fun() -> ok end), make_ref(), make_ref()},
+    {A, B} = term_gen_recursive(Leafs, 0, 0),
+    %%io:format("Recursive term A = ~p\n", [A]),
+    %%io:format("Recursive term B = ~p\n", [B]),
+
+    ?CHECK({true,false} =:=  case do_cmp(A, B, false) of
+				 -1 -> {A<B, A>=B};
+				 0 -> {A==B, A/=B};
+				 1 -> {A>B, A=<B}
+			     end,
+	   {A,B}),
+    A2 = copy_term(A),
+    ?CHECK(A == A2, {A,A2}),
+    ?CHECK(0 =:= cmp(A, A2, false), {A,A2}),
+
+    B2 = copy_term(B),
+    ?CHECK(B == B2, {B,B2}),
+    ?CHECK(0 =:= cmp(B, B2, false), {B,B2}),
+    ok.
+
+do_cmp(A, B, Exact) ->
+    C = cmp(A, B, Exact),
+    C.
+
+%% Generate two terms {A,B} that may only differ
+%% at float vs integer types.
+term_gen_recursive(Leafs, Flags, Depth) ->
+    MaxDepth = 10,
+    Rnd = case {Flags, Depth} of
+	      {_, MaxDepth} -> % Only leafs
+		  random:uniform(size(Leafs)) + 3;
+	      {0, 0} ->        % Only containers
+		  random:uniform(3);
+	      {0,_} ->         % Anything
+		  random:uniform(size(Leafs)+3)
+	  end,
+    case Rnd of
+	1 -> % Make map
+	    Size = random:uniform(size(Leafs)),
+	    lists:foldl(fun(_, {Acc1,Acc2}) ->
+				{K1,K2} = term_gen_recursive(Leafs, Flags,
+							     Depth+1),
+				{V1,V2} = term_gen_recursive(Leafs, Flags, Depth+1),
+				{maps:put(K1,V1, Acc1), maps:put(K2,V2, Acc2)}
+			end,
+			{maps:new(), maps:new()},
+			lists:seq(1,Size));
+	2 -> % Make cons
+	    {Car1,Car2} = term_gen_recursive(Leafs, Flags, Depth+1),
+	    {Cdr1,Cdr2} = term_gen_recursive(Leafs, Flags, Depth+1),
+	    {[Car1 | Cdr1], [Car2 | Cdr2]};
+	3 -> % Make tuple
+	    Size = random:uniform(size(Leafs)),
+	    L = lists:map(fun(_) -> term_gen_recursive(Leafs, Flags, Depth+1) end,
+			  lists:seq(1,Size)),
+	    {L1, L2} = lists:unzip(L),
+	    {list_to_tuple(L1), list_to_tuple(L2)};
+
+	N -> % Make leaf
+	    case element(N-3, Leafs) of
+		I when is_integer(I) ->
+		    case random:uniform(4) of
+			1 -> {I, float(I)};
+			2 -> {float(I), I};
+			_ -> {I,I}
+		    end;
+		T -> {T,T}
+	    end
+    end.
+
+%% BIFs
+t_bif_map_get(Config) when is_list(Config) ->
+    %% small map
+    1    = maps:get(a, #{ a=> 1}),
+    2    = maps:get(b, #{ a=> 1, b => 2}),
+    "hi" = maps:get("hello", #{ a=>1, "hello" => "hi"}),
+    "tuple hi" = maps:get({1,1.0}, #{ a=>a, {1,1.0} => "tuple hi"}),
+
+    M0    = #{ k1=>"v1", <<"k2">> => <<"v3">> },
+    "v4" = maps:get(<<"k2">>, M0#{<<"k2">> => "v4"}),
+
+    %% large map
+    M1   = maps:from_list([{I,I}||I<-lists:seq(1,100)] ++
+			  [{a,1},{b,2},{"hello","hi"},{{1,1.0},"tuple hi"},
+			   {k1,"v1"},{<<"k2">>,"v3"}]),
+    1    = maps:get(a, M1),
+    2    = maps:get(b, M1),
+    "hi" = maps:get("hello", M1),
+    "tuple hi" = maps:get({1,1.0}, M1),
+    "v3" = maps:get(<<"k2">>, M1),
+
+    %% error cases
+    do_badmap(fun(T) ->
+		      {'EXIT',{{badmap,T},[{maps,get,_,_}|_]}} =
+			  (catch maps:get(a, T))
+	      end),
+
+    {'EXIT',{{badkey,{1,1}},[{maps,get,_,_}|_]}} =
+	(catch maps:get({1,1}, #{{1,1.0} => "tuple"})),
+    {'EXIT',{{badkey,a},[{maps,get,_,_}|_]}} = (catch maps:get(a, #{})),
+    {'EXIT',{{badkey,a},[{maps,get,_,_}|_]}} =
+	(catch maps:get(a, #{b=>1, c=>2})),
+    ok.
+
+t_bif_map_find(Config) when is_list(Config) ->
+    %% small map
+    {ok, 1}     = maps:find(a, #{ a=> 1}),
+    {ok, 2}     = maps:find(b, #{ a=> 1, b => 2}),
+    {ok, "int"} = maps:find(1, #{ 1   => "int"}),
+    {ok, "float"} = maps:find(1.0, #{ 1.0=> "float"}),
+
+    {ok, "hi"} = maps:find("hello", #{ a=>1, "hello" => "hi"}),
+    {ok, "tuple hi"} = maps:find({1,1.0}, #{ a=>a, {1,1.0} => "tuple hi"}),
+
+    M0 = #{ k1=>"v1", <<"k2">> => <<"v3">> },
+    {ok, "v4"} = maps:find(<<"k2">>, M0#{ <<"k2">> => "v4" }),
+
+    %% large map
+    M1   = maps:from_list([{I,I}||I<-lists:seq(1,100)] ++
+			  [{a,1},{b,2},{"hello","hi"},{{1,1.0},"tuple hi"},
+			   {k1,"v1"},{<<"k2">>,"v3"}]),
+    {ok, 1}    = maps:find(a, M1),
+    {ok, 2}    = maps:find(b, M1),
+    {ok, "hi"} = maps:find("hello", M1),
+    {ok, "tuple hi"} = maps:find({1,1.0}, M1),
+    {ok, "v3"} = maps:find(<<"k2">>, M1),
+
+    %% error case
+    error = maps:find(a,#{}),
+    error = maps:find(a,#{b=>1, c=>2}),
+    error = maps:find(1.0, #{ 1 => "int"}),
+    error = maps:find(1, #{ 1.0  => "float"}),
+    error = maps:find({1.0,1}, #{ a=>a, {1,1.0} => "tuple hi"}), % reverse types in tuple key
+
+    do_badmap(fun(T) ->
+		      {'EXIT',{{badmap,T},[{maps,find,_,_}|_]}} =
+			  (catch maps:find(a, T))
+	      end),
+    ok.
+
+
+t_bif_map_is_key(Config) when is_list(Config) ->
+    M1 = #{ "hi" => "hello", int => 3, <<"key">> => <<"value">>, 4 => number},
+
+    true  = maps:is_key("hi", M1),
+    true  = maps:is_key(int, M1),
+    true  = maps:is_key(<<"key">>, M1),
+    true  = maps:is_key(4, M1),
+
+    false = maps:is_key(5, M1),
+    false = maps:is_key(<<"key2">>, M1),
+    false = maps:is_key("h", M1),
+    false = maps:is_key("hello", M1),
+    false = maps:is_key(atom, M1),
+    false = maps:is_key(any, #{}),
+
+    false = maps:is_key("hi", maps:remove("hi", M1)),
+    true  = maps:is_key("hi", M1),
+    true  = maps:is_key(1, maps:put(1, "number", M1)),
+    false = maps:is_key(1.0, maps:put(1, "number", M1)),
+
+    %% error case
+    do_badmap(fun(T) ->
+		      {'EXIT',{{badmap,T},[{maps,is_key,_,_}|_]}} =
+			  (catch maps:is_key(a, T))
+	      end),
+    ok.
+
+t_bif_map_keys(Config) when is_list(Config) ->
+    [] = maps:keys(#{}),
+
+    [1,2,3,4,5] = lists:sort(maps:keys(#{ 1 => a, 2 => b, 3 => c, 4 => d, 5 => e})),
+    [1,2,3,4,5] = lists:sort(maps:keys(#{ 4 => d, 5 => e, 1 => a, 2 => b, 3 => c})),
+
+    % values in key order: [4,int,"hi",<<"key">>]
+    M1 = #{ "hi" => "hello", int => 3, <<"key">> => <<"value">>, 4 => number},
+    [4,int,"hi",<<"key">>] = lists:sort(maps:keys(M1)),
+
+    %% error case
+    do_badmap(fun(T) ->
+		      {'EXIT',{{badmap,T},[{maps,keys,_,_}|_]}} =
+			  (catch maps:keys(T))
+	      end),
+    ok.
+
+t_bif_map_new(Config) when is_list(Config) ->
+    #{} = maps:new(),
+    0   = erlang:map_size(maps:new()),
+    ok.
+
+t_bif_map_merge(Config) when is_list(Config) ->
+    0   = erlang:map_size(maps:merge(#{},#{})),
+
+    M0 = #{ "hi" => "hello", int => 3, <<"key">> => <<"value">>,
+	4 => number, 18446744073709551629 => wat},
+
+    #{ "hi" := "hello", int := 3, <<"key">> := <<"value">>,
+	4 := number, 18446744073709551629 := wat} = maps:merge(#{}, M0),
+
+    #{ "hi" := "hello", int := 3, <<"key">> := <<"value">>,
+	4 := number, 18446744073709551629 := wat} = maps:merge(M0, #{}),
+
+    M1 = #{ "hi" => "hello again", float => 3.3, {1,2} => "tuple", 4 => integer },
+
+    #{4 := number, 18446744073709551629 := wat, float := 3.3, int := 3,
+	{1,2} := "tuple", "hi" := "hello", <<"key">> := <<"value">>} = maps:merge(M1,M0),
+
+    #{4 := integer, 18446744073709551629 := wat, float := 3.3, int := 3,
+	{1,2} := "tuple", "hi" := "hello again", <<"key">> := <<"value">>} = maps:merge(M0,M1),
+
+    %% try deep collisions
+    N  = 150000,
+    Is = lists:seq(1,N),
+    M2 = maps:from_list([{I,I}||I<-Is]),
+    150000 = maps:size(M2),
+    M3 = maps:from_list([{<<I:32>>,I}||I<-Is]),
+    150000 = maps:size(M3),
+    M4 = maps:merge(M2,M3),
+    300000 = maps:size(M4),
+    M5 = maps:from_list([{integer_to_list(I),I}||I<-Is]),
+    150000 = maps:size(M5),
+    M6 = maps:merge(M4,M5),
+    450000 = maps:size(M6),
+    M7 = maps:from_list([{float(I),I}||I<-Is]),
+    150000 = maps:size(M7),
+    M8 = maps:merge(M7,M6),
+    600000 = maps:size(M8),
+
+    #{      1 := 1,           "1" := 1,           <<1:32>> := 1      } = M8,
+    #{     10 := 10,         "10" := 10,         <<10:32>> := 10     } = M8,
+    #{    100 := 100,       "100" := 100,       <<100:32>> := 100    } = M8,
+    #{   1000 := 1000,     "1000" := 1000,     <<1000:32>> := 1000   } = M8,
+    #{  10000 := 10000,   "10000" := 10000,   <<10000:32>> := 10000  } = M8,
+    #{ 100000 := 100000, "100000" := 100000, <<100000:32>> := 100000 } = M8,
+
+    %% overlapping
+    M8 = maps:merge(M2,M8),
+    M8 = maps:merge(M3,M8),
+    M8 = maps:merge(M4,M8),
+    M8 = maps:merge(M5,M8),
+    M8 = maps:merge(M6,M8),
+    M8 = maps:merge(M7,M8),
+    M8 = maps:merge(M8,M8),
+
+    %% maps:merge/2 and mixed
+
+    Ks1 = [764492191,2361333849], %% deep collision
+    Ks2 = lists:seq(1,33),
+    M9  = maps:from_list([{K,K}||K <- Ks1]),
+    M10 = maps:from_list([{K,K}||K <- Ks2]),
+    M11 = maps:merge(M9,M10),
+    ok = check_keys_exist(Ks1 ++ Ks2, M11),
+
+    %% error case
+    do_badmap(fun(T) ->
+		      {'EXIT',{{badmap,T},[{maps,merge,_,_}|_]}} =
+			  (catch maps:merge(#{}, T)),
+		      {'EXIT',{{badmap,T},[{maps,merge,_,_}|_]}} =
+			  (catch maps:merge(T, #{})),
+		      {'EXIT',{{badmap,T},[{maps,merge,_,_}|_]}} =
+			  (catch maps:merge(T, T))
+	      end),
+    ok.
+
+
+t_bif_map_put(Config) when is_list(Config) ->
+    M0 = #{ "hi" => "hello", int => 3, <<"key">> => <<"value">>,
+	4 => number, 18446744073709551629 => wat},
+
+    M1 = #{ "hi" := "hello"} = maps:put("hi", "hello", #{}),
+
+    true = is_members(["hi"],maps:keys(M1)),
+    true = is_members(["hello"],maps:values(M1)),
+
+    M2 = #{ int := 3 } = maps:put(int, 3, M1),
+
+    true = is_members([int,"hi"],maps:keys(M2)),
+    true = is_members([3,"hello"],maps:values(M2)),
+
+    M3 = #{ <<"key">> := <<"value">> } = maps:put(<<"key">>, <<"value">>, M2),
+
+    true = is_members([int,"hi",<<"key">>],maps:keys(M3)),
+    true = is_members([3,"hello",<<"value">>],maps:values(M3)),
+
+    M4 = #{ 18446744073709551629 := wat } = maps:put(18446744073709551629, wat, M3),
+
+    true = is_members([18446744073709551629,int,"hi",<<"key">>],maps:keys(M4)),
+    true = is_members([wat,3,"hello",<<"value">>],maps:values(M4)),
+
+    M0 = #{ 4 := number } = M5 = maps:put(4, number, M4),
+
+    true = is_members([4,18446744073709551629,int,"hi",<<"key">>],maps:keys(M5)),
+    true = is_members([number,wat,3,"hello",<<"value">>],maps:values(M5)),
+
+    M6 = #{ <<"key">> := <<"other value">> } = maps:put(<<"key">>, <<"other value">>, M5),
+
+    true = is_members([4,18446744073709551629,int,"hi",<<"key">>],maps:keys(M6)),
+    true = is_members([number,wat,3,"hello",<<"other value">>],maps:values(M6)),
+
+    %% error case
+    do_badmap(fun(T) ->
+		      {'EXIT',{{badmap,T},[{maps,put,_,_}|_]}} =
+			  (catch maps:put(1, a, T))
+	      end),
+    ok.
+
+is_members(Ks,Ls) when length(Ks) =/= length(Ls) -> false;
+is_members(Ks,Ls) -> is_members_do(Ks,Ls).
+
+is_members_do([],[]) -> true;
+is_members_do([],_) -> false;
+is_members_do([K|Ks],Ls) ->
+    is_members_do(Ks, lists:delete(K,Ls)).
+
+t_bif_map_remove(Config) when is_list(Config) ->
+    0  = erlang:map_size(maps:remove(some_key, #{})),
+
+    M0 = #{ "hi" => "hello", int => 3, <<"key">> => <<"value">>,
+	4 => number, 18446744073709551629 => wat},
+
+    M1 = maps:remove("hi", M0),
+    true = is_members([4,18446744073709551629,int,<<"key">>],maps:keys(M1)),
+    true = is_members([number,wat,3,<<"value">>],maps:values(M1)),
+
+    M2 = maps:remove(int, M1),
+    true = is_members([4,18446744073709551629,<<"key">>],maps:keys(M2)),
+    true = is_members([number,wat,<<"value">>],maps:values(M2)),
+
+    M3 = maps:remove(<<"key">>, M2),
+    true = is_members([4,18446744073709551629],maps:keys(M3)),
+    true = is_members([number,wat],maps:values(M3)),
+
+    M4 = maps:remove(18446744073709551629, M3),
+    true = is_members([4],maps:keys(M4)),
+    true = is_members([number],maps:values(M4)),
+
+    M5 = maps:remove(4, M4),
+    [] = maps:keys(M5),
+    [] = maps:values(M5),
+
+    M0 = maps:remove(5,M0),
+    M0 = maps:remove("hi there",M0),
+
+    #{ "hi" := "hello", int := 3, 4 := number} = maps:remove(18446744073709551629,maps:remove(<<"key">>,M0)),
+
+    %% error case
+    do_badmap(fun(T) ->
+		      {'EXIT',{{badmap,T},[{maps,remove,_,_}|_]}} =
+	(catch maps:remove(a, T))
+	      end),
+     ok.
+
+t_bif_map_update(Config) when is_list(Config) ->
+    M0 = #{ "hi" => "hello", int => 3, <<"key">> => <<"value">>,
+	4 => number, 18446744073709551629 => wat},
+
+    #{ "hi" := "hello again", int := 3, <<"key">> := <<"value">>,
+	4 := number, 18446744073709551629 := wat} = maps:update("hi", "hello again", M0),
+
+    #{ "hi" := "hello", int := 1337, <<"key">> := <<"value">>,
+	4 := number, 18446744073709551629 := wat} = maps:update(int, 1337, M0),
+
+    #{ "hi" := "hello", int := 3, <<"key">> := <<"new value">>,
+	4 := number, 18446744073709551629 := wat} = maps:update(<<"key">>, <<"new value">>, M0),
+
+    #{ "hi" := "hello", int := 3, <<"key">> := <<"value">>,
+	4 := integer, 18446744073709551629 := wat} = maps:update(4, integer, M0),
+
+    #{ "hi" := "hello", int := 3, <<"key">> := <<"value">>,
+	4 := number, 18446744073709551629 := wazzup} = maps:update(18446744073709551629, wazzup, M0),
+
+    %% error case
+    do_badmap(fun(T) ->
+		      {'EXIT',{{badmap,T},[{maps,update,_,_}|_]}} =
+			  (catch maps:update(1, none, T))
+	      end),
+    ok.
+
+
+
+t_bif_map_values(Config) when is_list(Config) ->
+
+    [] = maps:values(#{}),
+    [1] = maps:values(#{a=>1}),
+
+    true = is_members([a,b,c,d,e],maps:values(#{ 1 => a, 2 => b, 3 => c, 4 => d, 5 => e})),
+    true = is_members([a,b,c,d,e],maps:values(#{ 4 => d, 5 => e, 1 => a, 2 => b, 3 => c})),
+
+    M1 = #{ "hi" => "hello", int => 3, <<"key">> => <<"value">>, 4 => number},
+    M2 = M1#{ "hi" => "hello2", <<"key">> => <<"value2">> },
+    true = is_members([number,3,"hello2",<<"value2">>],maps:values(M2)),
+    true = is_members([number,3,"hello",<<"value">>],maps:values(M1)),
+
+    Vs = lists:seq(1000,20000),
+    M3 = maps:from_list([{K,K}||K<-Vs]),
+    M4 = maps:merge(M1,M3),
+    M5 = maps:merge(M2,M3),
+    true = is_members(Vs,maps:values(M3)),
+    true = is_members([number,3,"hello",<<"value">>]++Vs,maps:values(M4)),
+    true = is_members([number,3,"hello2",<<"value2">>]++Vs,maps:values(M5)),
+
+    %% error case
+    do_badmap(fun(T) ->
+		      {'EXIT',{{badmap,T},[{maps,values,_,_}|_]}} =
+			  (catch maps:values(T))
+	      end),
+    ok.
+
+t_erlang_hash(Config) when is_list(Config) ->
+
+    ok = t_bif_erlang_phash2(),
+    ok = t_bif_erlang_phash(),
+    ok = t_bif_erlang_hash(),
+
+    ok.
+
+t_bif_erlang_phash2() ->
+
+    39679005 = erlang:phash2(#{}),
+    33667975 = erlang:phash2(#{ a => 1, "a" => 2, <<"a">> => 3, {a,b} => 4 }), % 78942764
+    95332690 = erlang:phash2(#{ 1 => a, 2 => "a", 3 => <<"a">>, 4 => {a,b} }), % 37338230
+    108954384 = erlang:phash2(#{ 1 => a }), % 14363616
+    59617982 = erlang:phash2(#{ a => 1 }), % 51612236
+
+    42770201 = erlang:phash2(#{{} => <<>>}), % 37468437
+    71687700 = erlang:phash2(#{<<>> => {}}), % 44049159
+
+    M0 = #{ a => 1, "key" => <<"value">> },
+    M1 = maps:remove("key",M0),
+    M2 = M1#{ "key" => <<"value">> },
+
+    70249457 = erlang:phash2(M0), % 118679416
+    59617982 = erlang:phash2(M1), % 51612236
+    70249457 = erlang:phash2(M2), % 118679416
+    ok.
+
+t_bif_erlang_phash() ->
+    Sz = 1 bsl 32,
+    1113425985 = erlang:phash(#{},Sz), % 268440612
+    1510068139 = erlang:phash(#{ a => 1, "a" => 2, <<"a">> => 3, {a,b} => 4 },Sz), % 1196461908
+    3182345590 = erlang:phash(#{ 1 => a, 2 => "a", 3 => <<"a">>, 4 => {a,b} },Sz), % 3944426064
+    2927531828 = erlang:phash(#{ 1 => a },Sz), % 1394238263
+    1670235874 = erlang:phash(#{ a => 1 },Sz), % 4066388227
+
+    3935089469 = erlang:phash(#{{} => <<>>},Sz), % 1578050717
+    71692856   = erlang:phash(#{<<>> => {}},Sz), % 1578050717
+
+    M0 = #{ a => 1, "key" => <<"value">> },
+    M1 = maps:remove("key",M0),
+    M2 = M1#{ "key" => <<"value">> },
+
+    2620391445 = erlang:phash(M0,Sz), % 3590546636
+    1670235874 = erlang:phash(M1,Sz), % 4066388227
+    2620391445 = erlang:phash(M2,Sz), % 3590546636
+    ok.
+
+t_bif_erlang_hash() ->
+    Sz = 1 bsl 27 - 1,
+    39684169 = erlang:hash(#{},Sz),  % 5158
+    33673142 = erlang:hash(#{ a => 1, "a" => 2, <<"a">> => 3, {a,b} => 4 },Sz), % 71555838
+    95337869 = erlang:hash(#{ 1 => a, 2 => "a", 3 => <<"a">>, 4 => {a,b} },Sz), % 5497225
+    108959561 = erlang:hash(#{ 1 => a },Sz), % 126071654
+    59623150 = erlang:hash(#{ a => 1 },Sz), % 126426236
+
+    42775386 = erlang:hash(#{{} => <<>>},Sz), % 101655720
+    71692856 = erlang:hash(#{<<>> => {}},Sz), % 101655720
+
+    M0 = #{ a => 1, "key" => <<"value">> },
+    M1 = maps:remove("key",M0),
+    M2 = M1#{ "key" => <<"value">> },
+
+    70254632 = erlang:hash(M0,Sz), % 38260486
+    59623150 = erlang:hash(M1,Sz), % 126426236
+    70254632 = erlang:hash(M2,Sz), % 38260486
+    ok.
+
+
+t_map_encode_decode(Config) when is_list(Config) ->
+    <<131,116,0,0,0,0>> = erlang:term_to_binary(#{}),
+    Pairs = [
+	{a,b},{"key","values"},{<<"key">>,<<"value">>},
+	{1,b},{[atom,1],{<<"wat">>,1,2,3}},
+	{aa,"values"},
+	{1 bsl 64 + (1 bsl 50 - 1), sc1},
+	{99, sc2},
+	{1 bsl 65 + (1 bsl 51 - 1), sc3},
+	{88, sc4},
+	{1 bsl 66 + (1 bsl 52 - 1), sc5},
+	{77, sc6},
+	{1 bsl 67 + (1 bsl 53 - 1), sc3},
+	{75, sc6}, {-10,sc8},
+	{<<>>, sc9}, {3.14158, sc10},
+	{[3.14158], sc11}, {more_atoms, sc12},
+	{{more_tuples}, sc13}, {self(), sc14},
+	{{},{}},{[],[]}
+    ],
+    ok = map_encode_decode_and_match(Pairs,[],#{}),
+
+    %% check sorting
+
+    %% literally #{ b=>2, a=>1 } in the internal order
+    #{ a:=1, b:=2 } =
+	erlang:binary_to_term(<<131,116,0,0,0,2,100,0,1,98,97,2,100,0,1,97,97,1>>),
+
+
+    %% literally #{ "hi" => "value", a=>33, b=>55 } in the internal order
+    #{ a:=33, b:=55, "hi" := "value"} = erlang:binary_to_term(<<131,116,0,0,0,3,
+	107,0,2,104,105,            % "hi" :: list()
+	107,0,5,118,97,108,117,101, % "value" :: list()
+	100,0,1,97,                 % a :: atom()
+	97,33,                      % 33 :: integer()
+	100,0,1,98,                 % b :: atom()
+	97,55                       % 55 :: integer()
+	>>),
+
+    %% Maps of different sizes
+    lists:foldl(fun(Key, M0) ->
+			M1 = M0#{Key => Key},
+			case Key rem 17 of
+			    0 ->
+				M1 = binary_to_term(term_to_binary(M1));
+			    _ ->
+				ok
+			end,
+			M1
+		end,
+		#{},
+		lists:seq(1,10000)),
+
+    %% many maps in same binary
+    MapList = lists:foldl(fun(K, [M|_]=Acc) -> [M#{K => K} | Acc] end,
+			  [#{}],
+			  lists:seq(1,100)),
+    MapList = binary_to_term(term_to_binary(MapList)),
+    MapListR = lists:reverse(MapList),
+    MapListR = binary_to_term(term_to_binary(MapListR)),
+
+    %% error cases
+    %% template: <<131,116,0,0,0,2,100,0,1,97,100,0,1,98,97,1,97,1>>
+    %% which is: #{ a=>1, b=>1 }
+
+    %% uniqueness violation
+    %% literally #{ a=>1, "hi"=>"value", a=>2 }
+    {'EXIT',{badarg,[{_,_,_,_}|_]}} = (catch
+	erlang:binary_to_term(<<131,116,0,0,0,3,
+			       100,0,1,97,
+			       97,1,
+			       107,0,2,104,105,
+			       107,0,5,118,97,108,117,101,
+			       100,0,1,97,
+			       97,2>>)),
+
+    %% bad size (too large)
+    {'EXIT',{badarg,[{_,_,_,_}|_]}} = (catch
+	erlang:binary_to_term(<<131,116,0,0,0,12,100,0,1,97,97,1,100,0,1,98,97,1>>)),
+
+    %% bad size (too small) .. should fail just truncate it .. weird.
+    %% possibly change external format so truncated will be #{a:=1}
+    #{ a:=b } =
+	erlang:binary_to_term(<<131,116,0,0,0,1,100,0,1,97,100,0,1,98,97,1,97,1>>),
+
+    ok.
+
+map_encode_decode_and_match([{K,V}|Pairs], EncodedPairs, M0) ->
+    M1 = maps:put(K,V,M0),
+    B0 = erlang:term_to_binary(M1),
+    Ls = [{erlang:term_to_binary(K), erlang:term_to_binary(V)}|EncodedPairs],
+    ok = match_encoded_map(B0, length(Ls), Ls),
+    %% decode and match it
+    M1 = erlang:binary_to_term(B0),
+    map_encode_decode_and_match(Pairs,Ls,M1);
+map_encode_decode_and_match([],_,_) -> ok.
+
+match_encoded_map(<<131,116,Size:32,Encoded/binary>>,Size,Items) ->
+    match_encoded_map_stripped_size(Encoded,Items,Items);
+match_encoded_map(_,_,_) -> no_match_size.
+
+match_encoded_map_stripped_size(<<>>,_,_) -> ok;
+match_encoded_map_stripped_size(B0,[{<<131,K/binary>>,<<131,V/binary>>}|Items],Ls) ->
+    Ksz = byte_size(K),
+    Vsz = byte_size(V),
+    case B0 of
+	<<K:Ksz/binary,V:Vsz/binary,B1/binary>> ->
+	    match_encoded_map_stripped_size(B1,Ls,Ls);
+	_ ->
+	    match_encoded_map_stripped_size(B0,Items,Ls)
+    end;
+match_encoded_map_stripped_size(_,[],_) -> fail.
+
+
+t_bif_map_to_list(Config) when is_list(Config) ->
+    [] = maps:to_list(#{}),
+    [{a,1},{b,2}] = lists:sort(maps:to_list(#{a=>1,b=>2})),
+    [{a,1},{b,2},{c,3}] = lists:sort(maps:to_list(#{c=>3,a=>1,b=>2})),
+    [{a,1},{b,2},{g,3}] = lists:sort(maps:to_list(#{g=>3,a=>1,b=>2})),
+    [{a,1},{b,2},{g,3},{"c",4}] = lists:sort(maps:to_list(#{g=>3,a=>1,b=>2,"c"=>4})),
+    [{3,v2},{hi,v4},{{hi,3},v5},{"hi",v3},{<<"hi">>,v1}] =
+	lists:sort(maps:to_list(#{<<"hi">>=>v1,3=>v2,"hi"=>v3,hi=>v4,{hi,3}=>v5})),
+
+    [{3,v7},{hi,v9},{{hi,3},v10},{"hi",v8},{<<"hi">>,v6}] =
+	lists:sort(maps:to_list(#{<<"hi">>=>v1,3=>v2,"hi"=>v3,hi=>v4,{hi,3}=>v5,
+				  <<"hi">>=>v6,3=>v7,"hi"=>v8,hi=>v9,{hi,3}=>v10})),
+
+    %% error cases
+    do_badmap(fun(T) ->
+		      {'EXIT', {{badmap,T},_}} =
+			  (catch maps:to_list(T))
+	      end),
+    ok.
+
+
+t_bif_map_from_list(Config) when is_list(Config) ->
+    #{} = maps:from_list([]),
+    A   = maps:from_list([]),
+    0   = erlang:map_size(A),
+
+    #{a:=1,b:=2}      = maps:from_list([{a,1},{b,2}]),
+    #{c:=3,a:=1,b:=2} = maps:from_list([{a,1},{b,2},{c,3}]),
+    #{g:=3,a:=1,b:=2} = maps:from_list([{a,1},{b,2},{g,3}]),
+
+    #{a:=2} = maps:from_list([{a,1},{a,3},{a,2}]),
+
+    #{ <<"hi">>:=v1,3:=v3,"hi":=v6,hi:=v4,{hi,3}:=v5} =
+	maps:from_list([{3,v3},{"hi",v6},{hi,v4},{{hi,3},v5},{<<"hi">>,v1}]),
+
+    #{<<"hi">>:=v6,3:=v8,"hi":=v11,hi:=v9,{hi,3}:=v10} =
+	maps:from_list([ {{hi,3},v3}, {"hi",v0},{3,v1}, {<<"hi">>,v4}, {hi,v2},
+	    {<<"hi">>,v6}, {{hi,3},v10},{"hi",v11}, {hi,v9}, {3,v8}]),
+
+    %% repeated keys (large -> small)
+    Ps1 = [{a,I}|| I <- lists:seq(1,32)],
+    Ps2 = [{a,I}|| I <- lists:seq(33,64)],
+
+    M = maps:from_list(Ps1 ++ [{b,1},{c,1}] ++ Ps2),
+    #{ a := 64, b := 1, c := 1 } = M,
+
+    %% error cases
+    {'EXIT', {badarg,_}} = (catch maps:from_list([{a,b},b])),
+    {'EXIT', {badarg,_}} = (catch maps:from_list([{a,b},{b,b,3}])),
+    {'EXIT', {badarg,_}} = (catch maps:from_list([{a,b},<<>>])),
+    {'EXIT', {badarg,_}} = (catch maps:from_list([{a,b}|{b,a}])),
+    {'EXIT', {badarg,_}} = (catch maps:from_list(a)),
+    {'EXIT', {badarg,_}} = (catch maps:from_list(42)),
+    ok.
+
+t_bif_build_and_check(Config) when is_list(Config) ->
+    ok = check_build_and_remove(750,[
+				      fun(K) -> [K,K] end,
+				      fun(K) -> [float(K),K] end,
+				      fun(K) -> K end,
+				      fun(K) -> {1,K} end,
+				      fun(K) -> {K} end,
+				      fun(K) -> [K|K] end,
+				      fun(K) -> [K,1,2,3,4] end,
+				      fun(K) -> {K,atom} end,
+				      fun(K) -> float(K) end,
+				      fun(K) -> integer_to_list(K) end,
+				      fun(K) -> list_to_atom(integer_to_list(K)) end,
+				      fun(K) -> [K,{K,[K,{K,[K]}]}] end,
+				      fun(K) -> <<K:32>> end
+			      ]),
+
+    ok.
+
+check_build_and_remove(_,[]) -> ok;
+check_build_and_remove(N,[F|Fs]) ->
+    {M,Ks} = build_and_check(N, maps:new(), F, []),
+    ok     = remove_and_check(Ks,M),
+    check_build_and_remove(N,Fs).
+
+build_and_check(0, M0, _, Ks) -> {M0, Ks};
+build_and_check(N, M0, F, Ks) ->
+    K  = build_key(F,N),
+    M1 = maps:put(K,K,M0),
+    ok = check_keys_exist([I||{I,_} <- [{K,M1}|Ks]], M1),
+    M2 = maps:update(K,v,M1),
+    v  = maps:get(K,M2),
+    build_and_check(N-1,M1,F,[{K,M1}|Ks]).
+
+remove_and_check([],_) -> ok;
+remove_and_check([{K,Mc}|Ks], M0) ->
+    K     = maps:get(K,M0),
+    true  = maps:is_key(K,M0),
+    true  = Mc =:= M0,
+    true  = M0 == Mc,
+    M1    = maps:remove(K,M0),
+    false = M1 =:= Mc,
+    false = Mc == M1,
+    false = maps:is_key(K,M1),
+    true  = maps:is_key(K,M0),
+    ok    = check_keys_exist([I||{I,_} <- Ks],M1),
+    error = maps:find(K,M1),
+    remove_and_check(Ks, M1).
+
+build_key(F,N) when N rem 3 =:= 0 -> F(N);
+build_key(F,N) when N rem 3 =:= 1 -> K = F(N), {K,K};
+build_key(F,N) when N rem 3 =:= 2 -> K = F(N), [K,K].
+
+check_keys_exist([], _) -> ok;
+check_keys_exist([K|Ks],M) ->
+    true = maps:is_key(K,M),
+    check_keys_exist(Ks,M).
+
+t_bif_merge_and_check(Config) when is_list(Config) ->
+
+    io:format("rand:export_seed() -> ~p\n",[rand:export_seed()]),
+
+    %% simple disjunct ones
+    %% make sure all keys are unique
+    Kss = [[a,b,c,d],
+	   [1,2,3,4],
+	   [],
+	   ["hi"],
+	   [e],
+	   [build_key(fun(K) -> {small,K} end, I) || I <- lists:seq(1,32)],
+	   lists:seq(5, 28),
+	   lists:seq(29, 59),
+	   [build_key(fun(K) -> integer_to_list(K) end, I) || I <- lists:seq(2000,10000)],
+	   [build_key(fun(K) -> <<K:32>> end, I) || I <- lists:seq(1,80)],
+	   [build_key(fun(K) -> {<<K:32>>} end, I) || I <- lists:seq(100,1000)]],
+
+
+    KsMs = build_keys_map_pairs(Kss),
+    Cs   = [{CKs1,CM1,CKs2,CM2} || {CKs1,CM1} <- KsMs, {CKs2,CM2} <- KsMs],
+    ok   = merge_and_check_combo(Cs),
+
+    %% overlapping ones
+
+    KVs1 = [{a,1},{b,2},{c,3}],
+    KVs2 = [{b,3},{c,4},{d,5}],
+    KVs  = [{I,I} || I <- lists:seq(1,32)],
+    KVs3 = KVs1 ++ KVs,
+    KVs4 = KVs2 ++ KVs,
+
+    M1  = maps:from_list(KVs1),
+    M2  = maps:from_list(KVs2),
+    M3  = maps:from_list(KVs3),
+    M4  = maps:from_list(KVs4),
+
+    M12 = maps:merge(M1,M2),
+    ok  = check_key_values(KVs2 ++ [{a,1}], M12),
+    M21 = maps:merge(M2,M1),
+    ok  = check_key_values(KVs1 ++ [{d,5}], M21),
+
+    M34 = maps:merge(M3,M4),
+    ok  = check_key_values(KVs4 ++ [{a,1}], M34),
+    M43 = maps:merge(M4,M3),
+    ok  = check_key_values(KVs3 ++ [{d,5}], M43),
+
+    M14 = maps:merge(M1,M4),
+    ok  = check_key_values(KVs4 ++ [{a,1}], M14),
+    M41 = maps:merge(M4,M1),
+    ok  = check_key_values(KVs1 ++ [{d,5}] ++ KVs, M41),
+
+    [begin Ma = random_map(SzA, a),
+	   Mb = random_map(SzB, b),
+	   ok = merge_maps(Ma, Mb)
+     end || SzA <- [3,10,20,100,200,1000], SzB <- [3,10,20,100,200,1000]],
+
+    ok.
+
+% Generate random map with an average of Sz number of pairs: K -> {V,K}
+random_map(Sz, V) ->
+    random_map_insert(#{}, 0, V, Sz*2).
+
+random_map_insert(M0, K0, _, Sz) when K0 > Sz ->
+    M0;
+random_map_insert(M0, K0, V, Sz) ->
+    Key = K0 + rand:uniform(3),
+    random_map_insert(M0#{Key => {V,Key}}, Key, V, Sz).
+
+
+merge_maps(A, B) ->
+    AB = maps:merge(A, B),
+    %%io:format("A=~p\nB=~p\n",[A,B]),
+    maps_foreach(fun(K,VB) -> VB = maps:get(K, AB)
+		 end, B),
+    maps_foreach(fun(K,VA) ->
+			 case {maps:get(K, AB),maps:find(K, B)} of
+			     {VA, error} -> ok;
+			     {VB, {ok, VB}} -> ok
+			 end
+		 end, A),
+
+    maps_foreach(fun(K,V) ->
+			 case {maps:find(K, A),maps:find(K, B)} of
+			     {{ok, V}, error} -> ok;
+			     {error, {ok, V}} -> ok;
+			     {{ok,_}, {ok, V}} -> ok
+			 end
+		 end, AB),
+    ok.
+
+maps_foreach(Fun, Map) ->
+    maps:fold(fun(K,V,_) -> Fun(K,V) end, void, Map).
+
+
+check_key_values([],_) -> ok;
+check_key_values([{K,V}|KVs],M) ->
+    V = maps:get(K,M),
+    check_key_values(KVs,M).
+
+merge_and_check_combo([]) -> ok;
+merge_and_check_combo([{Ks1,M1,Ks2,M2}|Cs]) ->
+    M12 = maps:merge(M1,M2),
+    ok  = check_keys_exist(Ks1 ++ Ks2, M12),
+    M21 = maps:merge(M2,M1),
+    ok  = check_keys_exist(Ks1 ++ Ks2, M21),
+
+    true = M12 =:= M21,
+    M12  = M21,
+
+    merge_and_check_combo(Cs).
+
+build_keys_map_pairs([]) -> [];
+build_keys_map_pairs([Ks|Kss]) ->
+    M  = maps:from_list(keys_to_pairs(Ks)),
+    ok = check_keys_exist(Ks, M),
+    [{Ks,M}|build_keys_map_pairs(Kss)].
+
+keys_to_pairs(Ks) -> [{K,K} || K <- Ks].
+
+
+%% Maps module, not BIFs
+t_maps_fold(_Config) ->
+    Vs = lists:seq(1,100),
+    M  = maps:from_list([{{k,I},{v,I}}||I<-Vs]),
+
+    %% fold
+    5050 = maps:fold(fun({k,_},{v,V},A) -> V + A end, 0, M),
+
+    ok.
+
+t_maps_map(_Config) ->
+    Vs = lists:seq(1,100),
+    M1 = maps:from_list([{I,I}||I<-Vs]),
+    M2 = maps:from_list([{I,{token,I}}||I<-Vs]),
+
+    M2 = maps:map(fun(_K,V) -> {token,V} end, M1),
+    ok.
+
+t_maps_size(_Config) ->
+    Vs = lists:seq(1,100),
+    lists:foldl(fun(I,M) ->
+		M1 = maps:put(I,I,M),
+		I  = maps:size(M1),
+		M1
+	end, #{}, Vs),
+    ok.
+
+
+t_maps_without(_Config) ->
+    Ki = [11,22,33,44,55,66,77,88,99],
+    M0 = maps:from_list([{{k,I},{v,I}}||I<-lists:seq(1,100)]),
+    M1 = maps:from_list([{{k,I},{v,I}}||I<-lists:seq(1,100) -- Ki]),
+    M1 = maps:without([{k,I}||I <- Ki],M0),
+    ok.
+
+t_erts_internal_order(_Config) when is_list(_Config) ->
+    M = #{0 => 0,2147483648 => 0},
+    true = M =:= binary_to_term(term_to_binary(M)),
+
+    F1 = fun(_, _) -> 0 end,
+    F2 = fun(_, _) -> 1 end,
+    M0 = maps:from_list( [{-2147483649, 0}, {0,0}, {97, 0}, {false, 0}, {flower, 0}, {F1, 0}, {F2, 0}, {<<>>, 0}]),
+    M1 = maps:merge(M0, #{0 => 1}),
+    8  = maps:size(M1),
+    1  = maps:get(0,M1),
+    ok.
+
+t_erts_internal_hash(_Config) when is_list(_Config) ->
+    K1 = 0.0,
+    K2 = 0.0/-1,
+    M  = maps:from_list([{I,I}||I<-lists:seq(1,32)]),
+
+    M1 = M#{ K1 => a, K2 => b },
+    b  = maps:get(K2,M1),
+
+    M2 = M#{ K2 => a, K1 => b },
+    b  = maps:get(K1,M2),
+
+    %% test previously faulty hash list optimization
+
+    M3 = M#{[0] => a, [0,0] => b, [0,0,0] => c, [0,0,0,0] => d},
+    a  = maps:get([0],M3),
+    b  = maps:get([0,0],M3),
+    c  = maps:get([0,0,0],M3),
+    d  = maps:get([0,0,0,0],M3),
+
+    M4 = M#{{[0]} => a, {[0,0]} => b, {[0,0,0]} => c, {[0,0,0,0]} => d},
+    a  = maps:get({[0]},M4),
+    b  = maps:get({[0,0]},M4),
+    c  = maps:get({[0,0,0]},M4),
+    d  = maps:get({[0,0,0,0]},M4),
+
+    M5 = M3#{[0,0,0] => e, [0,0,0,0] => f, [0,0,0,0,0] => g,
+             [0,0,0,0,0,0] => h, [0,0,0,0,0,0,0] => i,
+             [0,0,0,0,0,0,0,0] => j, [0,0,0,0,0,0,0,0,0] => k},
+
+    a  = maps:get([0],M5),
+    b  = maps:get([0,0],M5),
+    e  = maps:get([0,0,0],M5),
+    f  = maps:get([0,0,0,0],M5),
+    g  = maps:get([0,0,0,0,0],M5),
+    h  = maps:get([0,0,0,0,0,0],M5),
+    i  = maps:get([0,0,0,0,0,0,0],M5),
+    j  = maps:get([0,0,0,0,0,0,0,0],M5),
+    k  = maps:get([0,0,0,0,0,0,0,0,0],M5),
+
+    M6 = M4#{{[0,0,0]} => e, {[0,0,0,0]} => f, {[0,0,0,0,0]} => g,
+             {[0,0,0,0,0,0]} => h, {[0,0,0,0,0,0,0]} => i,
+             {[0,0,0,0,0,0,0,0]} => j, {[0,0,0,0,0,0,0,0,0]} => k},
+
+    a  = maps:get({[0]},M6),
+    b  = maps:get({[0,0]},M6),
+    e  = maps:get({[0,0,0]},M6),
+    f  = maps:get({[0,0,0,0]},M6),
+    g  = maps:get({[0,0,0,0,0]},M6),
+    h  = maps:get({[0,0,0,0,0,0]},M6),
+    i  = maps:get({[0,0,0,0,0,0,0]},M6),
+    j  = maps:get({[0,0,0,0,0,0,0,0]},M6),
+    k  = maps:get({[0,0,0,0,0,0,0,0,0]},M6),
+
+    M7 = maps:merge(M5,M6),
+
+    a  = maps:get([0],M7),
+    b  = maps:get([0,0],M7),
+    e  = maps:get([0,0,0],M7),
+    f  = maps:get([0,0,0,0],M7),
+    g  = maps:get([0,0,0,0,0],M7),
+    h  = maps:get([0,0,0,0,0,0],M7),
+    i  = maps:get([0,0,0,0,0,0,0],M7),
+    j  = maps:get([0,0,0,0,0,0,0,0],M7),
+    k  = maps:get([0,0,0,0,0,0,0,0,0],M7),
+    a  = maps:get({[0]},M7),
+    b  = maps:get({[0,0]},M7),
+    e  = maps:get({[0,0,0]},M7),
+    f  = maps:get({[0,0,0,0]},M7),
+    g  = maps:get({[0,0,0,0,0]},M7),
+    h  = maps:get({[0,0,0,0,0,0]},M7),
+    i  = maps:get({[0,0,0,0,0,0,0]},M7),
+    j  = maps:get({[0,0,0,0,0,0,0,0]},M7),
+    k  = maps:get({[0,0,0,0,0,0,0,0,0]},M7),
+    ok.
+
+t_pdict(_Config) ->
+
+    put(#{ a => b, b => a},#{ c => d}),
+    put(get(#{ a => b, b => a}),1),
+    1 = get(#{ c => d}),
+    #{ c := d } = get(#{ a => b, b => a}).
+
+t_ets(_Config) ->
+
+    Tid = ets:new(map_table,[]),
+
+    [ets:insert(Tid,{maps:from_list([{I,-I}]),I}) || I <- lists:seq(1,100)],
+
+
+    [{#{ 2 := -2},2}] = ets:lookup(Tid,#{ 2 => -2 }),
+
+    %% Test equal
+    [3,4] = lists:sort(
+	      ets:select(Tid,[{{'$1','$2'},
+			       [{'or',{'==','$1',#{ 3 => -3 }},
+				 {'==','$1',#{ 4 => -4 }}}],
+			       ['$2']}])),
+    %% Test match
+    [30,50] = lists:sort(
+		ets:select(Tid,
+			   [{{#{ 30 => -30}, '$1'},[],['$1']},
+			    {{#{ 50 => -50}, '$1'},[],['$1']}]
+			  )),
+
+    ets:insert(Tid,{#{ a => b, b => c, c => a},transitivity}),
+
+    %% Test equal with map of different size
+    [] = ets:select(Tid,[{{'$1','_'},[{'==','$1',#{ b => c }}],['$_']}]),
+
+    %% Test match with map of different size
+    %[{#{ a := b },_}] = ets:select(Tid,[{{#{ b => c },'_'},[],['$_']}]),
+
+    %%% Test match with don't care value
+    %[{#{ a := b },_}] = ets:select(Tid,[{{#{ b => '_' },'_'},[],['$_']}]),
+
+    %% Test is_map bif
+    101 = length(ets:select(Tid,[{'$1',[{is_map,{element,1,'$1'}}],['$1']}])),
+    ets:insert(Tid,{not_a_map,2}),
+    101 = length(ets:select(Tid,[{'$1',[{is_map,{element,1,'$1'}}],['$1']}])),
+    ets:insert(Tid,{{nope,a,tuple},2}),
+    101 = length(ets:select(Tid,[{'$1',[{is_map,{element,1,'$1'}}],['$1']}])),
+
+    %% Test map_size bif
+    [3] = ets:select(Tid,[{{'$1','_'},[{'==',{map_size,'$1'},3}],
+			   [{map_size,'$1'}]}]),
+
+    true = ets:delete(Tid,#{50 => -50}),
+    [] = ets:lookup(Tid,#{50 => -50}),
+
+    ets:delete(Tid),
+    ok.
+
+t_dets(_Config) ->
+    ok.
+
+t_tracing(_Config) ->
+
+    dbg:stop_clear(),
+    {ok,Tracer} = dbg:tracer(process,{fun trace_collector/2, self()}),
+    dbg:p(self(),c),
+
+    %% Test basic map call
+    {ok,_} = dbg:tpl(?MODULE,id,x),
+    #{ a => b },
+    {trace,_,call,{?MODULE,id,[#{ a := b }]}} = getmsg(Tracer),
+    {trace,_,return_from,{?MODULE,id,1},#{ a := b }} = getmsg(Tracer),
+    dbg:ctpl(),
+
+    %% Test equals in argument list
+    {ok,_} = dbg:tpl(?MODULE,id,[{['$1'],[{'==','$1',#{ b => c}}],
+				  [{return_trace}]}]),
+    #{ a => b },
+    #{ b => c },
+    {trace,_,call,{?MODULE,id,[#{ b := c }]}} = getmsg(Tracer),
+    {trace,_,return_from,{?MODULE,id,1},#{ b := c }} = getmsg(Tracer),
+    dbg:ctpl(),
+
+    %% Test match in head
+    {ok,_} = dbg:tpl(?MODULE,id,[{[#{b => c}],[],[]}]),
+    #{ a => b },
+    #{ b => c },
+    {trace,_,call,{?MODULE,id,[#{ b := c }]}} = getmsg(Tracer),
+    dbg:ctpl(),
+
+    % Test map guard bifs
+    {ok,_} = dbg:tpl(?MODULE,id,[{['$1'],[{is_map,{element,1,'$1'}}],[]}]),
+    #{ a => b },
+    {1,2},
+    {#{ a => b},2},
+    {trace,_,call,{?MODULE,id,[{#{ a := b },2}]}} = getmsg(Tracer),
+    dbg:ctpl(),
+
+    {ok,_} = dbg:tpl(?MODULE,id,[{['$1'],[{'==',{map_size,{element,1,'$1'}},2}],[]}]),
+    #{ a => b },
+    {1,2},
+    {#{ a => b},2},
+    {#{ a => b, b => c},atom},
+    {trace,_,call,{?MODULE,id,[{#{ a := b, b := c },atom}]}} = getmsg(Tracer),
+    dbg:ctpl(),
+
+    %MS = dbg:fun2ms(fun([A]) when A == #{ a => b} -> ok end),
+    %dbg:tpl(?MODULE,id,MS),
+    %#{ a => b },
+    %#{ b => c },
+    %{trace,_,call,{?MODULE,id,[#{ a := b }]}} = getmsg(Tracer),
+    %dbg:ctpl(),
+
+    %% Check to extra messages
+    timeout = getmsg(Tracer),
+
+    dbg:stop_clear(),
+    ok.
+
+getmsg(_Tracer) ->
+    receive V -> V after 100 -> timeout end.
+
+trace_collector(Msg,Parent) ->
+    io:format("~p~n",[Msg]),
+    Parent ! Msg,
+    Parent.
+
+t_has_map_fields(Config) when is_list(Config) ->
+    true = has_map_fields_1(#{one=>1}),
+    true = has_map_fields_1(#{one=>1,two=>2}),
+    false = has_map_fields_1(#{two=>2}),
+    false = has_map_fields_1(#{}),
+
+    true = has_map_fields_2(#{c=>1,b=>2,a=>3}),
+    true = has_map_fields_2(#{c=>1,b=>2,a=>3,x=>42}),
+    false = has_map_fields_2(#{b=>2,c=>1}),
+    false = has_map_fields_2(#{x=>y}),
+    false = has_map_fields_2(#{}),
+
+    true = has_map_fields_3(#{c=>1,b=>2,a=>3}),
+    true = has_map_fields_3(#{c=>1,b=>2,a=>3,[]=>42}),
+    true = has_map_fields_3(#{b=>2,a=>3,[]=>42,42.0=>43}),
+    true = has_map_fields_3(#{a=>3,[]=>42,42.0=>43}),
+    true = has_map_fields_3(#{[]=>42,42.0=>43}),
+    false = has_map_fields_3(#{b=>2,c=>1}),
+    false = has_map_fields_3(#{[]=>y}),
+    false = has_map_fields_3(#{42.0=>x,a=>99}),
+    false = has_map_fields_3(#{}),
+
+    ok.
+
+has_map_fields_1(#{one:=_}) -> true;
+has_map_fields_1(#{}) -> false.
+
+has_map_fields_2(#{a:=_,b:=_,c:=_}) -> true;
+has_map_fields_2(#{}) -> false.
+
+has_map_fields_3(#{a:=_,b:=_}) -> true;
+has_map_fields_3(#{[]:=_,42.0:=_}) -> true;
+has_map_fields_3(#{}) -> false.
+
+y_regs(Config) when is_list(Config) ->
+    Val = [length(Config)],
+    Map0 = y_regs_update(#{}, Val),
+    Map2 = y_regs_update(Map0, Val),
+
+    Map3 = maps:from_list([{I,I*I} || I <- lists:seq(1, 100)]),
+    Map4 = y_regs_update(Map3, Val),
+
+    true = is_map(Map2) andalso is_map(Map4),
+
+    ok.
+
+y_regs_update(Map0, Val0) ->
+    Val1 = {t,Val0},
+    K1 = {key,1},
+    K2 = {key,2},
+    Map1 = Map0#{K1=>K1,
+		 a=>Val0,b=>Val0,c=>Val0,d=>Val0,e=>Val0,
+		 f=>Val0,g=>Val0,h=>Val0,i=>Val0,j=>Val0,
+		 k=>Val0,l=>Val0,m=>Val0,n=>Val0,o=>Val0,
+		 p=>Val0,q=>Val0,r=>Val0,s=>Val0,t=>Val0,
+		 u=>Val0,v=>Val0,w=>Val0,x=>Val0,y=>Val0,
+		 z=>Val0,
+		 aa=>Val0,ab=>Val0,ac=>Val0,ad=>Val0,ae=>Val0,
+		 af=>Val0,ag=>Val0,ah=>Val0,ai=>Val0,aj=>Val0,
+		 ak=>Val0,al=>Val0,am=>Val0,an=>Val0,ao=>Val0,
+		 ap=>Val0,aq=>Val0,ar=>Val0,as=>Val0,at=>Val0,
+		 au=>Val0,av=>Val0,aw=>Val0,ax=>Val0,ay=>Val0,
+		 az=>Val0,
+		 K2=>[a,b,c]},
+    Map2 = Map1#{K1=>K1,
+		 a:=Val1,b:=Val1,c:=Val1,d:=Val1,e:=Val1,
+		 f:=Val1,g:=Val1,h:=Val1,i:=Val1,j:=Val1,
+		 k:=Val1,l:=Val1,m:=Val1,n:=Val1,o:=Val1,
+		 p:=Val1,q:=Val1,r:=Val1,s:=Val1,t:=Val1,
+		 u:=Val1,v:=Val1,w:=Val1,x:=Val1,y:=Val1,
+		 z:=Val1,
+		 aa:=Val1,ab:=Val1,ac:=Val1,ad:=Val1,ae:=Val1,
+		 af:=Val1,ag:=Val1,ah:=Val1,ai:=Val1,aj:=Val1,
+		 ak:=Val1,al:=Val1,am:=Val1,an:=Val1,ao:=Val1,
+		 ap:=Val1,aq:=Val1,ar:=Val1,as:=Val1,at:=Val1,
+		 au:=Val1,av:=Val1,aw:=Val1,ax:=Val1,ay:=Val1,
+		 az:=Val1,
+		 K2=>[a,b,c]},
+
+    %% Traverse the maps to validate them.
+    _ = erlang:phash2({Map1,Map2}, 100000),
+
+    _ = {K1,K2,Val0,Val1},			%Force use of Y registers.
+    Map2.
+
+do_badmap(Test) ->
+    Terms = [Test,fun erlang:abs/1,make_ref(),self(),0.0/-1,
+	     <<0:1024>>,<<1:1>>,<<>>,<<1,2,3>>,
+	     [],{a,b,c},[a,b],atom,10.0,42,(1 bsl 65) + 3],
+    [Test(T) || T <- Terms].
diff --git a/lib/dialyzer/test/map_SUITE_data/src/map_in_guard.erl b/lib/dialyzer/test/map_SUITE_data/src/map_in_guard.erl
new file mode 100644
index 0000000000..6176ef1fdf
--- /dev/null
+++ b/lib/dialyzer/test/map_SUITE_data/src/map_in_guard.erl
@@ -0,0 +1,35 @@
+-module(map_in_guard).
+
+-export([test/0, raw_expr/0]).
+
+test() ->
+    false = assoc_guard(#{}),
+    true  = assoc_guard(not_a_map),
+    #{a := true} = assoc_update(#{}),
+    {'EXIT', {{badmap, not_a_map}, [{?MODULE, assoc_update, 1, _}|_]}}
+	= (catch assoc_update(not_a_map)),
+    ok = assoc_guard_clause(#{}),
+    {'EXIT', {function_clause, [{?MODULE, assoc_guard_clause, _, _}|_]}}
+	= (catch assoc_guard_clause(not_a_map)),
+    true = exact_guard(#{a=>1}),
+    {'EXIT', {function_clause, [{?MODULE, assoc_guard_clause, _, _}|_]}}
+    %% There's nothing we can do to find the error here, is there?
+	= (catch (begin true = exact_guard(#{}) end)),
+    ok = exact_guard_clause(#{a => q}),
+    {'EXIT', {function_clause, [{?MODULE, exact_guard_clause, _, _}|_]}}
+	= (catch exact_guard_clause(#{})),
+    ok.
+
+assoc_guard(M) when is_map(M#{a => b}) -> true;
+assoc_guard(Q) -> false.
+
+assoc_update(M) -> M#{a => true}.
+
+assoc_guard_clause(M) when is_map(M#{a => 3}) -> ok.
+
+exact_guard(M) when (false =/= M#{a := b}) -> true;
+exact_guard(_) -> false.
+
+exact_guard_clause(M) when (false =/= M#{a := b}) -> ok.
+
+raw_expr() when #{}; true -> ok. %% Must not warn here!
diff --git a/lib/dialyzer/test/map_SUITE_data/src/map_in_guard2.erl b/lib/dialyzer/test/map_SUITE_data/src/map_in_guard2.erl
new file mode 100644
index 0000000000..ac2205e8fa
--- /dev/null
+++ b/lib/dialyzer/test/map_SUITE_data/src/map_in_guard2.erl
@@ -0,0 +1,27 @@
+-module(map_in_guard2).
+
+-export([test/0]).
+
+test() ->
+    false = assoc_guard(not_a_map),
+    {'EXIT', {{badmap, not_a_map}, [{?MODULE, assoc_update, 1, _}|_]}}
+	= (catch assoc_update(not_a_map)),
+    {'EXIT', {function_clause, [{?MODULE, assoc_guard_clause, _, _}|_]}}
+	= (catch assoc_guard_clause(not_a_map)),
+    {'EXIT', {function_clause, [{?MODULE, assoc_guard_clause, _, _}|_]}}
+	= (catch (begin true = exact_guard(#{}) end)),
+    {'EXIT', {function_clause, [{?MODULE, exact_guard_clause, _, _}|_]}}
+	= (catch exact_guard_clause(#{})),
+    ok.
+
+assoc_guard(M) when is_map(M#{a => b}) -> true;
+assoc_guard(_) -> false.
+
+assoc_update(M) -> M#{a => true}.
+
+assoc_guard_clause(M) when is_map(M#{a => 3}) -> ok.
+
+exact_guard(M) when (false =/= M#{a := b}) -> true;
+exact_guard(_) -> false.
+
+exact_guard_clause(M) when (false =/= M#{a := b}) -> ok.
diff --git a/lib/dialyzer/test/map_SUITE_data/src/map_size.erl b/lib/dialyzer/test/map_SUITE_data/src/map_size.erl
new file mode 100644
index 0000000000..2da4f6904e
--- /dev/null
+++ b/lib/dialyzer/test/map_SUITE_data/src/map_size.erl
@@ -0,0 +1,36 @@
+-module(map_size).
+
+-export([t1/0, e1/0, t2/0, t3/0, t4/0, t5/1, t6/1, t7/1]).
+
+t1() ->
+    0 = maps:size(#{}),
+    1 = maps:size(#{}).
+
+e1() ->
+    0 = map_size(#{}),
+    1 = map_size(#{}).
+
+t2() -> p(#{a=>x}).
+
+p(M) when map_size(M) =:= 0 -> ok.
+
+t3() ->
+    1 = map_size(cio()),
+    2 = map_size(cio()),
+    3 = map_size(cio()),
+    4 = map_size(cio()).
+
+t4() ->
+    0 = map_size(cio()).
+
+t5(M) when map_size(M) =:= 0 ->
+    #{a := _} = M. %% Only t5 has no local return; want better message
+
+t6(M) when map_size(M) =:= 0 ->
+    #{} = M.
+
+t7(M=#{a := _}) when map_size(M) =:= 1 ->
+    #{b := _} = M. %% We should warn here too
+
+-spec cio() -> #{3 := ok, 9 => _, 11 => x}.
+cio() -> binary_to_term(<<131,116,0,0,0,2,97,3,100,0,2,111,107,97,9,97,6>>).
diff --git a/lib/dialyzer/test/map_SUITE_data/src/maps_merge.erl b/lib/dialyzer/test/map_SUITE_data/src/maps_merge.erl
new file mode 100644
index 0000000000..d4f3c6887a
--- /dev/null
+++ b/lib/dialyzer/test/map_SUITE_data/src/maps_merge.erl
@@ -0,0 +1,29 @@
+-module(maps_merge).
+
+-export([t1/0, t2/0, t3/0, t4/0, t5/0]).
+
+t1() ->
+    #{a:=1} = maps:merge(#{}, #{}).
+
+t2() ->
+    #{hej := _} = maps:merge(cao(), cio()),
+    #{{} := _} = maps:merge(cao(), cio()).
+
+t3() ->
+    #{a:=1} = maps:merge(cao(), cio()),
+    #{7:=q} = maps:merge(cao(), cio()).
+
+t4() ->
+    #{a:=1} = maps:merge(cio(), cao()),
+    #{7:=q} = maps:merge(cio(), cao()).
+
+t5() ->
+    #{a:=2} = maps:merge(cao(), #{}).
+
+-spec cao() -> #{a := 1, q => none(), 11 => _, atom() => _}.
+cao() ->
+    binary_to_term(<<131,116,0,0,0,3,100,0,1,97,97,1,100,0,1,98,97,9,100,0,1,
+		     102,104,0>>).
+
+-spec cio() -> #{3 := ok, 7 => none(), z => _, integer() => _}.
+cio() -> binary_to_term(<<131,116,0,0,0,2,97,3,100,0,2,111,107,97,9,97,6>>).
diff --git a/lib/dialyzer/test/map_SUITE_data/src/opaque_key/opaque_key_adt.erl b/lib/dialyzer/test/map_SUITE_data/src/opaque_key/opaque_key_adt.erl
new file mode 100644
index 0000000000..b98c713c6b
--- /dev/null
+++ b/lib/dialyzer/test/map_SUITE_data/src/opaque_key/opaque_key_adt.erl
@@ -0,0 +1,69 @@
+-module(opaque_key_adt).
+
+-compile(export_all).
+
+-export_type([t/0, t/1, m/0, s/1, sm/1]).
+
+-opaque t()    :: #{atom() => integer()}.
+-opaque t(A)   :: #{A => integer()}.
+
+-opaque m()    :: #{t() => integer()}.
+-type   mt()   :: #{t() => integer()}.
+
+-opaque s(K)   :: #{K => integer(), integer() => atom()}.
+-opaque sm(K)  :: #{K := integer(), integer() := atom()}.
+-type   smt(K) :: #{K := integer(), integer() := atom()}.
+
+-spec t0() -> t().
+t0() -> #{}.
+
+-spec t1() -> t(integer()).
+t1() -> #{3 => 1}.
+
+-spec m0() -> m().
+m0() -> #{#{} => 3}.
+
+-spec mt0() -> mt().
+mt0() -> #{#{} => 3}.
+
+-spec s0() -> s(atom()).
+s0() -> #{}.
+
+-spec s1() -> s(atom()).
+s1() -> #{3 => a}.
+
+-spec s2() -> s(atom() | 3).
+s2() -> #{3 => a}. %% Contract breakage (not found)
+
+-spec s3() -> s(atom() | 3).
+s3() -> #{3 => 5, a => 6, 7 => 8}.
+
+-spec s4() -> s(integer()).
+s4() -> #{1 => a}. %% Contract breakage
+
+-spec s5() -> s(1).
+s5() -> #{2 => 3}. %% Contract breakage
+
+-spec s6() -> s(1).
+s6() -> #{1 => 3}.
+
+-spec s7() -> s(integer()).
+s7() -> #{1 => 3}.
+
+-spec sm1() -> sm(1).
+sm1() -> #{1 => 2, 3 => a}.
+
+-spec smt1() -> smt(1).
+smt1() -> #{3 => a}. %% Contract breakage
+
+-spec smt2() -> smt(1).
+smt2() -> #{1 => a}.  %% Contract breakage
+
+-spec smt3() -> smt(q).
+smt3() -> #{q => 1}. %% Slight contract breakage (probably requires better map type)
+
+-spec smt4() -> smt(q).
+smt4() -> #{q => 2, 3 => a}.
+
+-spec smt5() -> smt(1).
+smt5() -> #{1 => 2, 3 => a}.
diff --git a/lib/dialyzer/test/map_SUITE_data/src/opaque_key/opaque_key_use.erl b/lib/dialyzer/test/map_SUITE_data/src/opaque_key/opaque_key_use.erl
new file mode 100644
index 0000000000..917413fdd2
--- /dev/null
+++ b/lib/dialyzer/test/map_SUITE_data/src/opaque_key/opaque_key_use.erl
@@ -0,0 +1,97 @@
+-module(opaque_key_use).
+
+-compile(export_all).
+
+-export_type([t/0, t/1]).
+
+-opaque t()  :: #{atom() => integer()}.
+-opaque t(A) :: #{A => integer()}.
+
+tt1() ->
+    A = t0(),
+    B = t1(),
+    A =:= B. % never 'true'
+
+-spec t0() -> t().
+t0() -> #{a => 1}.
+
+-spec t1() -> t(integer()).
+t1() -> #{3 => 1}.
+
+adt_tt1() ->
+    A = adt_t0(),
+    B = adt_t1(),
+    A =:= B. % opaque attempt
+
+adt_tt2() ->
+    A = adt_t0(),
+    B = adt_t1(),
+    #{A => 1 % opaque key
+     ,B => 2 % opaque key
+     }.
+
+adt_tt3() ->
+    A = map_adt:t0(),
+    #{A => 1}. % opaque key
+
+adt_mm1() ->
+    A = adt_t0(),
+    M = adt_m0(),
+    #{A := R} = M, % opaque attempt
+    R.
+
+%% adt_ms1() ->
+%%     A = adt_t0(),
+%%     M = adt_m0(),
+%%     M#{A}. % opaque arg
+
+adt_mu1() ->
+    A = adt_t0(),
+    M = adt_m0(),
+    M#{A := 4}. % opaque arg
+
+adt_mu2() ->
+    A = adt_t0(),
+    M = adt_m0(),
+    M#{A => 4}. % opaque arg
+
+adt_mu3() ->
+    M = adt_m0(),
+    M#{}. % opaque arg
+
+adt_mtm1() ->
+    A = adt_t0(),
+    M = adt_mt0(),
+    #{A := R} = M, % opaque key
+    R.
+
+%% adt_mts1() ->
+%%     A = adt_t0(),
+%%     M = adt_mt0(),
+%%     M#{A}. % opaque key
+
+adt_mtu1() ->
+    A = adt_t0(),
+    M = adt_mt0(),
+    M#{A := 4}. % opaque key
+
+adt_mtu2() ->
+    A = adt_t0(),
+    M = adt_mt0(),
+    M#{A => 4}. % opaque key
+
+adt_mtu3() ->
+    M = adt_mt0(),
+    M#{}. % Ok to not warn
+
+adt_t0() ->
+    opaque_key_adt:t0().
+
+adt_t1() ->
+    opaque_key_adt:t1().
+
+adt_m0() ->
+    opaque_key_adt:m0().
+
+adt_mt0() ->
+    opaque_key_adt:mt0().
diff --git a/lib/dialyzer/test/map_SUITE_data/src/order.erl b/lib/dialyzer/test/map_SUITE_data/src/order.erl
new file mode 100644
index 0000000000..51868d7e94
--- /dev/null
+++ b/lib/dialyzer/test/map_SUITE_data/src/order.erl
@@ -0,0 +1,56 @@
+-module(order).
+
+-export([t1/0, t2/0, t3/0, t4/0, t5/0, t6/0]).
+
+t1() ->
+    case maps:get(a, #{a=>1, a=>b}) of
+	Int when is_integer(Int) -> fail;
+	Atom when is_atom(Atom) -> error(ok);
+	_Else -> fail
+    end.
+
+t2() ->
+    case maps:get(a, #{a=>id_1(1), a=>id_b(b)}) of
+	Int when is_integer(Int) -> fail;
+	Atom when is_atom(Atom) -> error(ok);
+	_Else -> fail
+    end.
+
+t3() ->
+    case maps:get(a, #{a=>id_1(1), id_a(a)=>id_b(b)}) of
+	Int when is_integer(Int) -> fail;
+	Atom when is_atom(Atom) -> error(ok);
+	_Else -> fail
+    end.
+
+t4() ->
+    case maps:get(a, #{a=>id_1(1), a_or_b()=>id_b(b)}) of
+	Int when is_integer(Int) -> ok;
+	Atom when is_atom(Atom) -> ok;
+	_Else -> fail
+    end.
+
+t5() ->
+    case maps:get(c, #{c=>id_1(1), a_or_b()=>id_b(b)}) of
+	Int when is_integer(Int) -> error(ok);
+	Atom when is_atom(Atom) -> fail;
+	_Else -> fail
+    end.
+
+t6() ->
+    case maps:get(a, #{a_or_b()=>id_1(1), id_a(a)=>id_b(b)}) of
+	Int when is_integer(Int) -> fail;
+	Atom when is_atom(Atom) -> error(ok);
+	_Else -> fail
+    end.
+
+id_1(X) -> X.
+
+id_a(X) -> X.
+
+id_b(X) -> X.
+
+any() -> binary_to_term(<<>>).
+
+-spec a_or_b() -> a | b.
+a_or_b() -> any().
diff --git a/lib/dialyzer/test/map_SUITE_data/src/subtract_value_flip.erl b/lib/dialyzer/test/map_SUITE_data/src/subtract_value_flip.erl
new file mode 100644
index 0000000000..97e6b54e3c
--- /dev/null
+++ b/lib/dialyzer/test/map_SUITE_data/src/subtract_value_flip.erl
@@ -0,0 +1,9 @@
+-module(subtract_value_flip).
+
+-export([t1/1]).
+
+t1(#{type := _Smth} = Map) ->
+    case Map of
+	#{type := a} -> ok;
+	#{type := b} -> error
+    end.
diff --git a/lib/dialyzer/test/map_SUITE_data/src/typeflow.erl b/lib/dialyzer/test/map_SUITE_data/src/typeflow.erl
new file mode 100644
index 0000000000..b43fd6897b
--- /dev/null
+++ b/lib/dialyzer/test/map_SUITE_data/src/typeflow.erl
@@ -0,0 +1,25 @@
+-module(typeflow).
+
+-export([t1/1, t2/1, t3/1, t4/1]).
+
+t1(M = #{}) ->
+    a_is_integer(M),
+    case M of
+	#{a := X} when is_integer(X) -> ok;
+	_ -> fail
+    end.
+
+a_is_integer(#{a := X}) when is_integer(X) -> ok.
+
+t2(M = #{}) ->
+    a_is_integer(M),
+    lists:sort(maps:get(a, M)),
+    ok.
+
+t3(M = #{}) ->
+    lists:sort(maps:get(a, M)),
+    ok.
+
+t4(M) ->
+    lists:sort(maps:get(a, M)),
+    ok.
diff --git a/lib/dialyzer/test/map_SUITE_data/src/typeflow2.erl b/lib/dialyzer/test/map_SUITE_data/src/typeflow2.erl
new file mode 100644
index 0000000000..71a9657a60
--- /dev/null
+++ b/lib/dialyzer/test/map_SUITE_data/src/typeflow2.erl
@@ -0,0 +1,88 @@
+-module(typeflow2).
+
+-export([t1/1, t2/1, t3/1, t4/1, t5/1, t6/1, t7/1, optional3/1]).
+
+t1(L) ->
+    M = only_integers_and_lists(L),
+    optional(M),
+    case M of
+	#{a := X} when is_integer(X) -> ok;
+	#{a := X} when is_list(X) -> ok; %% Must warn here
+	#{a := X} when is_pid(X) -> ok;
+	_ -> fail
+    end.
+
+optional(#{a:=X}) ->
+    true = is_integer(X);
+optional(#{}) ->
+    true.
+
+only_integers_and_lists(L) -> only_integers_and_lists(L, #{}).
+
+only_integers_and_lists([], M) -> M;
+only_integers_and_lists([{K,V}|T], M) when is_integer(V); is_list(V)->
+    only_integers_and_lists(T, M#{K => V}).
+
+t2(L) ->
+    M = only_integers_and_lists(L),
+    optional(M),
+    lists:sort(maps:get(a, M)),
+    ok.
+
+t3(L) ->
+    M = only_integers_and_lists(L),
+    lists:sort(maps:get(a, M)),
+    ok.
+
+t4(V) ->
+    M=map_with(a,V),
+    optional2(M),
+    case M of
+	#{a := X} when is_integer(X) -> ok;
+	#{a := X} when is_list(X) -> ok; %% Must warn here
+	_ -> fail
+    end.
+
+optional2(#{a:=X}) ->
+    true = is_integer(X);
+optional2(#{}) ->
+    true.
+
+map_with(K, V) when is_integer(V); is_list(V); is_atom(V) -> #{K => V}.
+
+t5(L) ->
+    M = only_integers_and_lists(L),
+    optional3(M),
+    case M of
+	#{a := X} when is_integer(X) -> ok;
+	#{a := X} when is_list(X) -> ok; %% Must warn here
+	#{a := X} when is_pid(X) -> ok; %% Must warn here
+	#{a := X} when is_atom(X) -> ok;
+	_ -> fail
+    end.
+
+t6(L) ->
+    M = only_integers_and_lists(L),
+    case M of
+	#{a := X} when is_integer(X) -> ok;
+	#{a := X} when is_list(X) -> ok; %% Must not warn here
+	_ -> fail
+    end.
+
+optional3(#{a:=X}) ->
+    true = is_integer(X);
+optional3(#{}) ->
+    true.
+
+t7(M) ->
+    optional4(M),
+    case M of
+	#{a := X} when is_integer(X) -> ok;
+	#{a := X} when is_list(X) -> ok;
+	#{a := X} when is_pid(X) -> ok; %% Must warn here
+	#{a := X} when is_atom(X) -> ok; %% Must warn here
+	_ -> fail %% Must not warn here (requires parsing)
+    end.
+
+-spec optional4(#{a=>integer()|list()}) -> true.
+optional4(#{}) -> true.
diff --git a/lib/dialyzer/test/map_SUITE_data/src/typesig.erl b/lib/dialyzer/test/map_SUITE_data/src/typesig.erl
new file mode 100644
index 0000000000..b50511af41
--- /dev/null
+++ b/lib/dialyzer/test/map_SUITE_data/src/typesig.erl
@@ -0,0 +1,9 @@
+-module(typesig).
+
+-export([t1/0, t2/0, t3/0, test/1]).
+
+t1() -> test(#{a=>1}).
+t2() -> test(#{a=>{b}}).
+t3() -> test(#{a=>{3}}).
+
+test(#{a:={X}}) -> X+1.
diff --git a/lib/dialyzer/test/small_SUITE_data/results/literals b/lib/dialyzer/test/small_SUITE_data/results/literals
index 222d2c0cdb..1ee39453a4 100644
--- a/lib/dialyzer/test/small_SUITE_data/results/literals
+++ b/lib/dialyzer/test/small_SUITE_data/results/literals
@@ -5,6 +5,7 @@ literals.erl:14: Function t2/0 has no local return
 literals.erl:15: Record construction #r{id::'a'} violates the declared type of field id::'integer'
 literals.erl:17: Function t3/0 has no local return
 literals.erl:18: Record construction #r{id::'a'} violates the declared type of field id::'integer'
+literals.erl:20: Function t4/0 has no local return
 literals.erl:21: Record construction #r{id::'a'} violates the declared type of field id::'integer'
 literals.erl:23: Function m1/1 has no local return
 literals.erl:23: Matching of pattern {'r', 'a'} tagged with a record name violates the declared type of #r{id::'integer'}
@@ -12,3 +13,5 @@ literals.erl:26: Function m2/1 has no local return
 literals.erl:26: Matching of pattern {'r', 'a'} tagged with a record name violates the declared type of #r{id::'integer'}
 literals.erl:29: Function m3/1 has no local return
 literals.erl:29: The pattern {{'r', 'a'}} can never match the type any()
+literals.erl:32: Function m4/1 has no local return
+literals.erl:32: Matching of pattern {'r', 'a'} tagged with a record name violates the declared type of #r{id::'integer'}
diff --git a/lib/dialyzer/test/small_SUITE_data/results/maps1 b/lib/dialyzer/test/small_SUITE_data/results/maps1
index e88c91f21f..a178e96b20 100644
--- a/lib/dialyzer/test/small_SUITE_data/results/maps1
+++ b/lib/dialyzer/test/small_SUITE_data/results/maps1
@@ -1,4 +1,4 @@
 
 maps1.erl:43: Function t3/0 has no local return
-maps1.erl:44: The call maps1:foo(~{'greger'=>3, ~{'arne'=>'anka'}~=>45}~,1) will never return since it differs in the 2nd argument from the success typing arguments: (#{},'b')
-maps1.erl:52: The call Mod:'function'(~{'literal'=>'map'}~,'another_arg') requires that Mod is of type atom() not #{}
+maps1.erl:44: The call maps1:foo(#{'greger'=>3, #{'arne'=>'anka'}=>45},1) will never return since it differs in the 1st and 2nd argument from the success typing arguments: (#{'beta':=_, ...},'b')
+maps1.erl:52: The variable Mod can never match since previous clauses completely covered the type #{}
diff --git a/lib/dialyzer/test/small_SUITE_data/results/maps_difftype b/lib/dialyzer/test/small_SUITE_data/results/maps_difftype
index 8980321135..3018b888db 100644
--- a/lib/dialyzer/test/small_SUITE_data/results/maps_difftype
+++ b/lib/dialyzer/test/small_SUITE_data/results/maps_difftype
@@ -1,3 +1,3 @@
 
 maps_difftype.erl:10: Function empty_mismatch/1 has no local return
-maps_difftype.erl:11: The pattern ~{}~ can never match the type tuple()
+maps_difftype.erl:11: The pattern #{} can never match the type tuple()
diff --git a/lib/dialyzer/test/small_SUITE_data/results/maps_sum b/lib/dialyzer/test/small_SUITE_data/results/maps_sum
index a19c0bba96..bd192bdb93 100644
--- a/lib/dialyzer/test/small_SUITE_data/results/maps_sum
+++ b/lib/dialyzer/test/small_SUITE_data/results/maps_sum
@@ -1,4 +1,4 @@
 
-maps_sum.erl:15: Invalid type specification for function maps_sum:wrong1/1. The success typing is (#{}) -> any()
+maps_sum.erl:15: Invalid type specification for function maps_sum:wrong1/1. The success typing is (map()) -> any()
 maps_sum.erl:26: Function wrong2/1 has no local return
 maps_sum.erl:27: The call lists:foldl(fun((_,_,_) -> any()),0,Data::any()) will never return since it differs in the 1st argument from the success typing arguments: (fun((_,_) -> any()),any(),[any()])
diff --git a/lib/dialyzer/test/small_SUITE_data/src/literals.erl b/lib/dialyzer/test/small_SUITE_data/src/literals.erl
index abd7033712..354a0f4cdc 100644
--- a/lib/dialyzer/test/small_SUITE_data/src/literals.erl
+++ b/lib/dialyzer/test/small_SUITE_data/src/literals.erl
@@ -2,7 +2,7 @@
 
 %% Bad records inside structures used to be ignored. The reason:
 %% v3_core:unfold() does not annotate the parts of a literal.
-%% This example does not work perfectly yet, in particular Maps.
+%% This example does not work perfectly yet.
 
 -export([t1/0, t2/0, t3/0, t4/0, m1/1, m2/1, m3/1, m4/1]).
 
@@ -18,7 +18,7 @@ t3() ->
     {#r{id = a}}. % violation
 
 t4() ->
-    #{a => #r{id = a}}. % violation found, but t4() returns... (bug)
+    #{a => #r{id = a}}. % violation
 
 m1(#r{id = a}) -> % violation
     ok.
@@ -29,5 +29,5 @@ m2([#r{id = a}]) -> % violation
 m3({#r{id = a}}) -> % can never match; not so good
     ok.
 
-m4(#{a := #r{id = a}}) -> % violation not found
+m4(#{a := #r{id = a}}) -> % violation
     ok.
diff --git a/lib/dialyzer/test/small_SUITE_data/src/maps1.erl b/lib/dialyzer/test/small_SUITE_data/src/maps1.erl
index bb2f66a498..597358d16a 100644
--- a/lib/dialyzer/test/small_SUITE_data/src/maps1.erl
+++ b/lib/dialyzer/test/small_SUITE_data/src/maps1.erl
@@ -21,7 +21,7 @@ recv(Packet, Fun, Chan) ->
   #{id := Can_id, data := Can_data} = P = decode(Packet),
   Fun(P).
 
--spec decode(<<_:64,_:_*8>>) -> #{id => <<_:11>>,timestamp => char()}.
+-spec decode(<<_:64,_:_*8>>) -> #{id => <<_:11>>,timestamp => char(),_ => _}.
 decode(<<_:12, Len:4, Timestamp:16, 0:3, Id:11/bitstring, 0:18,
 	 Data:Len/binary, _/binary>>) ->
   #{id => Id, data => Data, timestamp => Timestamp}.
diff --git a/lib/dialyzer/vsn.mk b/lib/dialyzer/vsn.mk
index 44982ab46d..77ea9d0413 100644
--- a/lib/dialyzer/vsn.mk
+++ b/lib/dialyzer/vsn.mk
@@ -1 +1 @@
-DIALYZER_VSN = 2.9
+DIALYZER_VSN = 2.10
diff --git a/lib/hipe/cerl/erl_bif_types.erl b/lib/hipe/cerl/erl_bif_types.erl
index 7684dc4a81..9453ca6c6f 100644
--- a/lib/hipe/cerl/erl_bif_types.erl
+++ b/lib/hipe/cerl/erl_bif_types.erl
@@ -115,7 +115,16 @@
 		    t_tuple_size/2,
 		    t_tuple_subtypes/2,
 		    t_is_map/2,
-		    t_map/0
+		    t_map/0,
+		    t_map/3,
+		    t_map_def_key/2,
+		    t_map_def_val/2,
+		    t_map_get/3,
+		    t_map_is_key/3,
+		    t_map_entries/2,
+		    t_map_put/3,
+		    t_map_update/3,
+		    map_pairwise_merge/3
 		   ]).
 
 -ifdef(DO_ERL_BIF_TYPES_TEST).
@@ -755,7 +764,7 @@ type(erlang, length, 1, Xs, Opaques) ->
   strict(erlang, length, 1, Xs, fun (_) -> t_non_neg_fixnum() end, Opaques);
 %% Guard bif, needs to be here.
 type(erlang, map_size, 1, Xs, Opaques) ->
-  strict(erlang, map_size, 1, Xs, fun (_) -> t_non_neg_integer() end, Opaques);
+  type(maps, size, 1, Xs, Opaques);
 type(erlang, make_fun, 3, Xs, Opaques) ->
   strict(erlang, make_fun, 3, Xs,
          fun ([_, _, Arity]) ->
@@ -1645,6 +1654,89 @@ type(lists, zipwith3, 4, Xs, Opaques) ->
 	 fun ([F,_As,_Bs,_Cs]) -> t_sup(t_list(t_fun_range(F, Opaques)),
                                         t_nil()) end, Opaques);
 
+%%-- maps ---------------------------------------------------------------------
+type(maps, from_list, 1, Xs, Opaques) ->
+  strict(maps, from_list, 1, Xs,
+	 fun ([List]) ->
+	     case t_is_nil(List, Opaques) of
+	       true -> t_from_term(#{});
+	       false ->
+		 T = t_list_elements(List, Opaques),
+		 case t_tuple_subtypes(T, Opaques) of
+		   unknown -> t_map();
+		   Stypes when length(Stypes) >= 1 ->
+		     t_sup([begin
+			      [K, V] = t_tuple_args(Args, Opaques),
+			      t_map([], K, V)
+			    end || Args <- Stypes])
+		 end
+	     end
+	 end, Opaques);
+type(maps, get, 2, Xs, Opaques) ->
+  strict(maps, get, 2, Xs,
+	 fun ([Key, Map]) ->
+	     t_map_get(Key, Map, Opaques)
+	 end, Opaques);
+type(maps, is_key, 2, Xs, Opaques) ->
+  strict(maps, is_key, 2, Xs,
+	 fun ([Key, Map]) ->
+	     t_map_is_key(Key, Map, Opaques)
+	 end, Opaques);
+type(maps, merge, 2, Xs, Opaques) ->
+  strict(maps, merge, 2, Xs,
+	 fun ([MapA, MapB]) ->
+	     ADefK = t_map_def_key(MapA, Opaques),
+	     BDefK = t_map_def_key(MapB, Opaques),
+	     ADefV = t_map_def_val(MapA, Opaques),
+	     BDefV = t_map_def_val(MapB, Opaques),
+	     t_map(map_pairwise_merge(
+		     fun(K, _,     _,  mandatory, V) -> {K, mandatory, V};
+			(K, MNess, VA, optional, VB) -> {K, MNess, t_sup(VA,VB)}
+		     end, MapA, MapB),
+		   t_sup(ADefK, BDefK), t_sup(ADefV, BDefV))
+	 end, Opaques);
+type(maps, put, 3, Xs, Opaques) ->
+  strict(maps, put, 3, Xs,
+	 fun ([Key, Value, Map]) ->
+	     t_map_put({Key, Value}, Map, Opaques)
+	 end, Opaques);
+type(maps, size, 1, Xs, Opaques) ->
+  strict(maps, size, 1, Xs,
+	 fun ([Map]) ->
+	     Mand = [E || E={_,mandatory,_} <- t_map_entries(Map, Opaques)],
+	     LowerBound = length(Mand),
+	     case t_is_none(t_map_def_key(Map, Opaques)) of
+	       false -> t_from_range(LowerBound, pos_inf);
+	       true ->
+		 Opt = [E || E={_,optional,_} <- t_map_entries(Map, Opaques)],
+		 UpperBound = LowerBound + length(Opt),
+		 t_from_range(LowerBound, UpperBound)
+	     end
+	 end, Opaques);
+type(maps, to_list, 1, Xs, Opaques) ->
+  strict(maps, to_list, 1, Xs,
+	 fun ([Map]) ->
+	     DefK = t_map_def_key(Map, Opaques),
+	     DefV = t_map_def_val(Map, Opaques),
+	     Pairs = t_map_entries(Map, Opaques),
+	     EType = lists:foldl(
+		       fun({K,_,V},EType0) ->
+			   case t_is_none(V) of
+			     true -> t_subtract(EType0, t_tuple([K,t_any()]));
+			     false -> t_sup(EType0, t_tuple([K,V]))
+			   end
+		       end, t_tuple([DefK, DefV]), Pairs),
+	     case t_is_none(EType) of
+	       true -> t_nil();
+	       false -> t_list(EType)
+	     end
+	 end, Opaques);
+type(maps, update, 3, Xs, Opaques) ->
+  strict(maps, update, 3, Xs,
+	 fun ([Key, Value, Map]) ->
+	     t_map_update({Key, Value}, Map, Opaques)
+	 end, Opaques);
+
 %%-----------------------------------------------------------------------------
 type(M, F, A, Xs, _O) when is_atom(M), is_atom(F),
 		       is_integer(A), 0 =< A, A =< 255 ->
@@ -2556,6 +2648,23 @@ arg_types(lists, zipwith, 3) ->
   [t_fun([t_any(), t_any()], t_any()), t_list(), t_list()];
 arg_types(lists, zipwith3, 4) ->
   [t_fun([t_any(), t_any(), t_any()], t_any()), t_list(), t_list(), t_list()];
+%%------- maps ----------------------------------------------------------------
+arg_types(maps, from_list, 1) ->
+  [t_list(t_tuple(2))];
+arg_types(maps, get, 2) ->
+  [t_any(), t_map()];
+arg_types(maps, is_key, 2) ->
+  [t_any(), t_map()];
+arg_types(maps, merge, 2) ->
+  [t_map(), t_map()];
+arg_types(maps, put, 3) ->
+  [t_any(), t_any(), t_map()];
+arg_types(maps, size, 1) ->
+  [t_map()];
+arg_types(maps, to_list, 1) ->
+  [t_map()];
+arg_types(maps, update, 3) ->
+  [t_any(), t_any(), t_map()];
 arg_types(M, F, A) when is_atom(M), is_atom(F),
 			is_integer(A), 0 =< A, A =< 255 ->
   unknown.                     % safe approximation for all functions.
diff --git a/lib/hipe/cerl/erl_types.erl b/lib/hipe/cerl/erl_types.erl
index fae12d7421..58060361af 100644
--- a/lib/hipe/cerl/erl_types.erl
+++ b/lib/hipe/cerl/erl_types.erl
@@ -140,6 +140,8 @@
 	 t_is_port/1, t_is_port/2,
 	 t_is_maybe_improper_list/1, t_is_maybe_improper_list/2,
 	 t_is_reference/1, t_is_reference/2,
+	 t_is_singleton/1,
+	 t_is_singleton/2,
 	 t_is_string/1,
 	 t_is_subtype/2,
 	 t_is_tuple/1, t_is_tuple/2,
@@ -152,6 +154,14 @@
 	 t_list_termination/1, t_list_termination/2,
 	 t_map/0,
 	 t_map/1,
+	 t_map/3,
+	 t_map_entries/2, t_map_entries/1,
+	 t_map_def_key/2, t_map_def_key/1,
+	 t_map_def_val/2, t_map_def_val/1,
+	 t_map_get/2, t_map_get/3,
+	 t_map_is_key/2, t_map_is_key/3,
+	 t_map_update/2, t_map_update/3,
+	 t_map_put/2, t_map_put/3,
 	 t_matchstate/0,
 	 t_matchstate/2,
 	 t_matchstate_present/1,
@@ -178,6 +188,7 @@
 	 %% t_maybe_improper_list/2,
 	 t_product/1,
 	 t_reference/0,
+	 t_singleton_to_term/2,
 	 t_string/0,
 	 t_struct_from_opaque/2,
 	 t_subst/2,
@@ -208,7 +219,8 @@
          lift_list_to_pos_empty/1, lift_list_to_pos_empty/2,
          is_opaque_type/2,
 	 is_erl_type/1,
-	 atom_to_string/1
+	 atom_to_string/1,
+	 map_pairwise_merge/3
 	]).
 
 %%-define(DO_ERL_TYPES_TEST, true).
@@ -341,7 +353,8 @@
 -define(nonempty_list(Types, Term),?list(Types, Term, ?nonempty_qual)).
 -define(number(Set, Qualifier),    #c{tag=?number_tag, elements=Set, 
 				      qualifier=Qualifier}).
--define(map(Pairs),                #c{tag=?map_tag, elements=Pairs}).
+-define(map(Pairs,DefKey,DefVal),
+	#c{tag=?map_tag, elements={Pairs,DefKey,DefVal}}).
 -define(opaque(Optypes),           #c{tag=?opaque_tag, elements=Optypes}).
 -define(product(Types),            #c{tag=?product_tag, elements=Types}).
 -define(tuple(Types, Arity, Qual), #c{tag=?tuple_tag, elements=Types, 
@@ -484,9 +497,8 @@ t_contains_opaque(?int_range(_From, _To), _Opaques) -> false;
 t_contains_opaque(?int_set(_Set), _Opaques) -> false;
 t_contains_opaque(?list(Type, Tail, _), Opaques) ->
   t_contains_opaque(Type, Opaques) orelse t_contains_opaque(Tail, Opaques);
-t_contains_opaque(?map(_) = Map, Opaques) ->
-  list_contains_opaque(map_values(Map), Opaques) orelse
-  list_contains_opaque(map_keys(Map), Opaques);
+t_contains_opaque(?map(_, _, _) = Map, Opaques) ->
+  list_contains_opaque(map_all_types(Map), Opaques);
 t_contains_opaque(?matchstate(_P, _Slots), _Opaques) -> false;
 t_contains_opaque(?nil, _Opaques) -> false;
 t_contains_opaque(?number(_Set, _Tag), _Opaques) -> false;
@@ -1581,16 +1593,107 @@ lift_list_to_pos_empty(?list(Content, Termination, _)) ->
 %%-----------------------------------------------------------------------------
 %% Maps
 %%
+%% Representation:
+%%  ?map(Pairs, DefaultKey, DefaultValue)
+%%
+%% Pairs is a sorted dictionary of types with a mandatoriness tag on each pair
+%% (t_map_dict()). DefaultKey and DefaultValue are plain types.
+%%
+%% A map M belongs to this type iff
+%%   For each pair {KT, mandatory, VT} in Pairs, there exists a pair {K, V} in M
+%%     such that K \in KT and V \in VT.
+%%   For each pair {KT, optional, VT} in Pairs, either there exists no key K in
+%%     M s.t. K in KT, or there exists a pair {K, V} in M such that K \in KT and
+%%     V \in VT.
+%%   For each remaining pair {K, V} in M (where remaining means that there is no
+%%     key KT in Pairs s.t. K \in KT), K \in DefaultKey and V \in DefaultValue.
+%%
+%% Invariants:
+%%  * The keys in Pairs are singleton types.
+%%  * The values of Pairs must not be unit, and may only be none if the
+%%      mandatoriness tag  is 'optional'.
+%%  * Optional must contain no pair {K,V} s.t. K is a subtype of DefaultKey and
+%%    V is equal to DefaultKey.
+%%  * DefaultKey must be the empty type iff DefaultValue is the empty type.
+%%  * DefaultKey must not be a singleton type.
+%%  * For every key K in Pairs, DefaultKey - K must not be representable; i.e.
+%%    t_subtract(DefaultKey, K) must return DefaultKey.
+%%  * For every pair {K, 'optional', ?none} in Pairs, K must be a subtype of
+%%    DefaultKey.
+%%  * Pairs must be sorted and not contain any duplicate keys.
+%%
+%% These invariants ensure that equal map types are represented by equal terms.
+
+-define(mand, mandatory).
+-define(opt, optional).
+
+-type t_map_mandatoriness() :: ?mand | ?opt.
+-type t_map_pair() :: {erl_type(), t_map_mandatoriness(), erl_type()}.
+-type t_map_dict() :: [t_map_pair()].
 
 -spec t_map() -> erl_type().
 
 t_map() ->
-  ?map([]).
+  t_map([], t_any(), t_any()).
 
 -spec t_map([{erl_type(), erl_type()}]) -> erl_type().
 
-t_map(_) ->
-  ?map([]).
+t_map(L) ->
+  lists:foldl(fun t_map_put/2, t_map(), L).
+
+-spec t_map(t_map_dict(), erl_type(), erl_type()) -> erl_type().
+
+t_map(Pairs0, DefK0, DefV0) ->
+  DefK1 = lists:foldl(fun({K,_,_},Acc)->t_subtract(Acc,K)end, DefK0, Pairs0),
+  {DefK2, DefV1} =
+    case t_is_none_or_unit(DefK1) orelse t_is_none_or_unit(DefV0) of
+      true  -> {?none, ?none};
+      false -> {DefK1, DefV0}
+    end,
+  {Pairs1, DefK, DefV}
+    = case is_singleton_type(DefK2) of
+	true  -> {mapdict_insert({DefK2, ?opt, DefV1}, Pairs0), ?none, ?none};
+	false -> {Pairs0,                                       DefK2, DefV1}
+      end,
+  Pairs = normalise_map_optionals(Pairs1, DefK, DefV),
+  %% Validate invariants of the map representation.
+  %% Since we needed to iterate over the arguments in order to normalise anyway,
+  %% we might as well save us some future pain and do this even without
+  %% define(DEBUG, true).
+  try
+    validate_map_elements(Pairs)
+  catch error:badarg ->      error(badarg,      [Pairs0,DefK0,DefV0]);
+	error:{badarg, E} -> error({badarg, E}, [Pairs0,DefK0,DefV0])
+  end,
+  ?map(Pairs, DefK, DefV).
+
+normalise_map_optionals([], _, _) -> [];
+normalise_map_optionals([E={K,?opt,?none}|T], DefK, DefV) ->
+  Diff = t_subtract(DefK, K),
+  case t_is_subtype(K, DefK) andalso DefK =:= Diff of
+    true -> [E|normalise_map_optionals(T, DefK, DefV)];
+    false -> normalise_map_optionals(T, Diff, DefV)
+  end;
+normalise_map_optionals([E={K,?opt,V}|T], DefK, DefV) ->
+  case t_is_equal(V, DefV) andalso t_is_subtype(K, DefK) of
+    true -> normalise_map_optionals(T, DefK, DefV);
+    false -> [E|normalise_map_optionals(T, DefK, DefV)]
+  end;
+normalise_map_optionals([E|T], DefK, DefV) ->
+  [E|normalise_map_optionals(T, DefK, DefV)].
+
+validate_map_elements([{_,?mand,?none}|_]) -> error({badarg, none_in_mand});
+validate_map_elements([{K1,_,_}|Rest=[{K2,_,_}|_]]) ->
+  case is_singleton_type(K1) andalso K1 < K2 of
+    false -> error(badarg);
+    true -> validate_map_elements(Rest)
+  end;
+validate_map_elements([{K,_,_}]) ->
+  case is_singleton_type(K) of
+    false -> error(badarg);
+    true -> true
+  end;
+validate_map_elements([]) -> true.
 
 -spec t_is_map(erl_type()) -> boolean().
 
@@ -1602,9 +1705,242 @@ t_is_map(Type) ->
 t_is_map(Type, Opaques) ->
   do_opaque(Type, Opaques, fun is_map1/1).
 
-is_map1(?map(_)) -> true;
+is_map1(?map(_, _, _)) -> true;
 is_map1(_) -> false.
 
+-spec t_map_entries(erl_type()) -> t_map_dict().
+
+t_map_entries(M) ->
+  t_map_entries(M, 'universe').
+
+-spec t_map_entries(erl_type(), opaques()) -> t_map_dict().
+
+t_map_entries(M, Opaques) ->
+  do_opaque(M, Opaques, fun map_entries/1).
+
+map_entries(?map(Pairs,_,_)) ->
+  Pairs.
+
+-spec t_map_def_key(erl_type()) -> erl_type().
+
+t_map_def_key(M) ->
+  t_map_def_key(M, 'universe').
+
+-spec t_map_def_key(erl_type(), opaques()) -> erl_type().
+
+t_map_def_key(M, Opaques) ->
+  do_opaque(M, Opaques, fun map_def_key/1).
+
+map_def_key(?map(_,DefK,_)) ->
+  DefK.
+
+-spec t_map_def_val(erl_type()) -> erl_type().
+
+t_map_def_val(M) ->
+  t_map_def_val(M, 'universe').
+
+-spec t_map_def_val(erl_type(), opaques()) -> erl_type().
+
+t_map_def_val(M, Opaques) ->
+  do_opaque(M, Opaques, fun map_def_val/1).
+
+map_def_val(?map(_,_,DefV)) ->
+  DefV.
+
+-spec mapdict_store(t_map_pair(), t_map_dict()) -> t_map_dict().
+
+mapdict_store(E={K,_,_}, [{K,_,_}|T]) -> [E|T];
+mapdict_store(E1={K1,_,_}, [E2={K2,_,_}|T]) when K1 > K2->
+  [E2|mapdict_store(E1, T)];
+mapdict_store(E={_,_,_}, T) -> [E|T].
+
+-spec mapdict_insert(t_map_pair(), t_map_dict()) -> t_map_dict().
+
+mapdict_insert(E={K,_,_}, D=[{K,_,_}|_]) -> error(badarg, [E, D]);
+mapdict_insert(E1={K1,_,_}, [E2={K2,_,_}|T]) when K1 > K2->
+  [E2|mapdict_insert(E1, T)];
+mapdict_insert(E={_,_,_}, T) -> [E|T].
+
+%% Merges the pairs of two maps together. Missing pairs become (?opt, DefV) or
+%% (?opt, ?none), depending on whether K \in DefK.
+-spec map_pairwise_merge(fun((erl_type(),
+			      t_map_mandatoriness(), erl_type(),
+			      t_map_mandatoriness(), erl_type())
+			     -> t_map_pair() | false),
+			 erl_type(), erl_type()) -> t_map_dict().
+map_pairwise_merge(F, ?map(APairs, ADefK, ADefV),
+		       ?map(BPairs, BDefK, BDefV)) ->
+  map_pairwise_merge(F, APairs, ADefK, ADefV, BPairs, BDefK, BDefV).
+
+map_pairwise_merge(_, [], _, _, [], _, _) -> [];
+map_pairwise_merge(F, As0, ADefK, ADefV, Bs0, BDefK, BDefV) ->
+  case {As0, Bs0} of
+    {[{K,AMNess,AV}|As], [{K, BMNess,BV}|Bs]} -> ok;
+    {[{K,AMNess,AV}|As], [{BK,_,     _ }|_]=Bs} when K < BK ->
+      {BMNess, BV} = {?opt, mapmerge_otherv(K, BDefK, BDefV)};
+    {As,                 [{K, BMNess,BV}|Bs]} ->
+      {AMNess, AV} = {?opt, mapmerge_otherv(K, ADefK, ADefV)};
+    {[{K,AMNess,AV}|As], []=Bs} ->
+      {BMNess, BV} = {?opt, mapmerge_otherv(K, BDefK, BDefV)}
+  end,
+  MK = K, %% Rename to make clear that we are matching below
+  case F(K, AMNess, AV, BMNess, BV) of
+    false ->         map_pairwise_merge(F,As,ADefK,ADefV,Bs,BDefK,BDefV);
+    M={MK,_,_} -> [M|map_pairwise_merge(F,As,ADefK,ADefV,Bs,BDefK,BDefV)]
+  end.
+
+%% Folds over the pairs in two maps simultaneously in reverse key order. Missing
+%% pairs become (?opt, DefV) or (?opt, ?none), depending on whether K \in DefK.
+-spec map_pairwise_merge_foldr(fun((erl_type(),
+				    t_map_mandatoriness(), erl_type(),
+				    t_map_mandatoriness(), erl_type(),
+				    Acc) -> Acc),
+			       Acc, erl_type(), erl_type()) -> Acc.
+
+map_pairwise_merge_foldr(F, AccIn, ?map(APairs, ADefK, ADefV),
+			 ?map(BPairs, BDefK, BDefV)) ->
+  map_pairwise_merge_foldr(F, AccIn, APairs, ADefK, ADefV, BPairs, BDefK, BDefV).
+
+map_pairwise_merge_foldr(_, Acc,   [],  _,     _,     [],  _,     _) -> Acc;
+map_pairwise_merge_foldr(F, AccIn, As0, ADefK, ADefV, Bs0, BDefK, BDefV) ->
+  case {As0, Bs0} of
+    {[{K,AMNess,AV}|As], [{K, BMNess,BV}|Bs]} -> ok;
+    {[{K,AMNess,AV}|As], [{BK,_,     _ }|_]=Bs} when K < BK ->
+      {BMNess, BV} = {?opt, mapmerge_otherv(K, BDefK, BDefV)};
+    {As,                 [{K, BMNess,BV}|Bs]} ->
+      {AMNess, AV} = {?opt, mapmerge_otherv(K, ADefK, ADefV)};
+    {[{K,AMNess,AV}|As], []=Bs} ->
+      {BMNess, BV} = {?opt, mapmerge_otherv(K, BDefK, BDefV)}
+  end,
+  F(K, AMNess, AV, BMNess, BV,
+    map_pairwise_merge_foldr(F,AccIn,As,ADefK,ADefV,Bs,BDefK,BDefV)).
+
+%% By observing that a missing pair in a map is equivalent to an optional pair,
+%% with ?none or DefV value, depending on whether K \in DefK, we can simplify
+%% merging by denormalising the map pairs temporarily, removing all 'false'
+%% cases, at the cost of the creation of more tuples:
+mapmerge_otherv(K, ODefK, ODefV) ->
+  case t_inf(K, ODefK) of
+    ?none      -> ?none;
+    _KOrOpaque -> ODefV
+  end.
+
+-spec t_map_put({erl_type(), erl_type()}, erl_type()) -> erl_type().
+
+t_map_put(KV, Map) ->
+  t_map_put(KV, Map, 'universe').
+
+-spec t_map_put({erl_type(), erl_type()}, erl_type(), opaques()) -> erl_type().
+
+t_map_put(KV, Map, Opaques) ->
+  do_opaque(Map, Opaques, fun(UM) -> map_put(KV, UM, Opaques) end).
+
+%% Key and Value are *not* unopaqued, but the map is
+map_put(_, ?none, _) -> ?none;
+map_put({Key, Value}, ?map(Pairs,DefK,DefV), Opaques) ->
+  case t_is_none_or_unit(Key) orelse t_is_none_or_unit(Value) of
+    true -> ?none;
+    false ->
+      case is_singleton_type(Key) of
+	true ->
+	  t_map(mapdict_store({Key, ?mand, Value}, Pairs), DefK, DefV);
+	false ->
+	  t_map([{K, MNess, case t_is_none(t_inf(K, Key, Opaques)) of
+			      true -> V;
+			      false -> t_sup(V, Value)
+			    end} || {K, MNess, V} <- Pairs],
+		t_sup(DefK, Key),
+		t_sup(DefV, Value))
+      end
+  end.
+
+-spec t_map_update({erl_type(), erl_type()}, erl_type()) -> erl_type().
+
+t_map_update(KV, Map) ->
+  t_map_update(KV, Map, 'universe').
+
+-spec t_map_update({erl_type(), erl_type()}, erl_type(), opaques()) -> erl_type().
+
+t_map_update(_, ?none, _) -> ?none;
+t_map_update(KV={Key, _}, M, Opaques) ->
+  case t_is_subtype(t_atom('true'), t_map_is_key(Key, M, Opaques)) of
+    false -> ?none;
+    true -> t_map_put(KV, M, Opaques)
+  end.
+
+-spec t_map_get(erl_type(), erl_type()) -> erl_type().
+
+t_map_get(Key, Map) ->
+  t_map_get(Key, Map, 'universe').
+
+-spec t_map_get(erl_type(), erl_type(), opaques()) -> erl_type().
+
+t_map_get(Key, Map, Opaques) ->
+  do_opaque(Map, Opaques,
+	    fun(UM) ->
+		do_opaque(Key, Opaques, fun(UK) -> map_get(UK, UM) end)
+	    end).
+
+map_get(_, ?none) -> ?none;
+map_get(Key, ?map(Pairs, DefK, DefV)) ->
+  DefRes =
+    case t_do_overlap(DefK, Key) of
+      false -> t_none();
+      true -> DefV
+    end,
+  case is_singleton_type(Key) of
+    false ->
+      lists:foldl(fun({K, _, V}, Res) ->
+		      case t_do_overlap(K, Key) of
+			false -> Res;
+			true -> t_sup(Res, V)
+		      end
+		  end, DefRes, Pairs);
+    true ->
+      case lists:keyfind(Key, 1, Pairs) of
+	false -> DefRes;
+	{_, _, ValType} -> ValType
+      end
+  end.
+
+-spec t_map_is_key(erl_type(), erl_type()) -> erl_type().
+
+t_map_is_key(Key, Map) ->
+  t_map_is_key(Key, Map, 'universe').
+
+-spec t_map_is_key(erl_type(), erl_type(), opaques()) -> erl_type().
+
+t_map_is_key(Key, Map, Opaques) ->
+  do_opaque(Map, Opaques,
+	    fun(UM) ->
+		do_opaque(Key, Opaques, fun(UK) -> map_is_key(UK, UM) end)
+	    end).
+
+map_is_key(_, ?none) -> ?none;
+map_is_key(Key, ?map(Pairs, DefK, _DefV)) ->
+  case is_singleton_type(Key) of
+    true ->
+      case lists:keyfind(Key, 1, Pairs) of
+	{Key, ?mand, _}     -> t_atom(true);
+	{Key, ?opt,  ?none} -> t_atom(false);
+	{Key, ?opt,  _}     -> t_boolean();
+	false ->
+	  case t_do_overlap(DefK, Key) of
+	    false -> t_atom(false);
+	    true -> t_boolean()
+	  end
+      end;
+    false ->
+      case t_do_overlap(DefK, Key)
+	orelse lists:any(fun({_,_,?none}) -> false;
+			    ({K,_,_}) -> t_do_overlap(K, Key)
+			 end, Pairs)
+      of
+	true -> t_boolean();
+	false -> t_atom(false)
+      end
+  end.
+
 %%-----------------------------------------------------------------------------
 %% Tuples
 %%
@@ -1862,8 +2198,9 @@ t_has_var(?tuple(Elements, _, _)) ->
   t_has_var_list(Elements);
 t_has_var(?tuple_set(_) = T) ->
   t_has_var_list(t_tuple_subtypes(T));
-t_has_var(?map(_)= Map) ->
-  t_has_var_list(map_keys(Map)) orelse t_has_var_list(map_values(Map));
+t_has_var(?map(_, DefK, _)= Map) ->
+  t_has_var_list(map_all_values(Map)) orelse
+    t_has_var(DefK);
 t_has_var(?opaque(Set)) ->
   %% Assume variables in 'args' are also present i 'struct'
   t_has_var_list([O#opaque.struct || O <- set_to_list(Set)]);
@@ -1898,9 +2235,9 @@ t_collect_vars(?tuple(Types, _, _), Acc) ->
   t_collect_vars_list(Types, Acc);
 t_collect_vars(?tuple_set(_) = TS, Acc) ->
   t_collect_vars_list(t_tuple_subtypes(TS), Acc);
-t_collect_vars(?map(_) = Map, Acc0) ->
-  Acc = t_collect_vars_list(map_keys(Map), Acc0),
-  t_collect_vars_list(map_values(Map), Acc);
+t_collect_vars(?map(_, DefK, _) = Map, Acc0) ->
+  Acc = t_collect_vars_list(map_all_values(Map), Acc0),
+  t_collect_vars(DefK, Acc);
 t_collect_vars(?opaque(Set), Acc) ->
   %% Assume variables in 'args' are also present i 'struct'
   t_collect_vars_list([O#opaque.struct || O <- set_to_list(Set)], Acc);
@@ -1935,7 +2272,15 @@ t_from_term(T) when is_function(T) ->
   {arity, Arity} = erlang:fun_info(T, arity),
   t_fun(Arity, t_any());
 t_from_term(T) when is_integer(T) ->   t_integer(T);
-t_from_term(T) when is_map(T) ->       t_map();
+t_from_term(T) when is_map(T) ->
+  Pairs = [{t_from_term(K), ?mand, t_from_term(V)}
+	   || {K, V} <- maps:to_list(T)],
+  {Stons, Rest} = lists:partition(fun({K,_,_}) -> is_singleton_type(K) end,
+				  Pairs),
+  {DefK, DefV}
+    = lists:foldl(fun({K,_,V},{AK,AV}) -> {t_sup(K,AK), t_sup(V,AV)} end,
+		  {t_none(), t_none()}, Rest),
+  t_map(lists:keysort(1, Stons), DefK, DefV);
 t_from_term(T) when is_pid(T) ->       t_pid();
 t_from_term(T) when is_port(T) ->      t_port();
 t_from_term(T) when is_reference(T) -> t_reference();
@@ -2225,6 +2570,13 @@ t_sup(?tuple_set(List1), T2 = ?tuple(_, Arity, _)) ->
   sup_tuple_sets(List1, [{Arity, [T2]}]);
 t_sup(?tuple(_, Arity, _) = T1, ?tuple_set(List2)) ->
   sup_tuple_sets([{Arity, [T1]}], List2);
+t_sup(?map(_, ADefK, ADefV) = A, ?map(_, BDefK, BDefV) = B) ->
+  Pairs =
+    map_pairwise_merge(
+      fun(K, MNess, V1, MNess, V2) -> {K, MNess, t_sup(V1, V2)};
+	 (K, _,     V1, _,     V2) -> {K, ?opt,  t_sup(V1, V2)}
+      end, A, B),
+  t_map(Pairs, t_sup(ADefK, BDefK), t_sup(ADefV, BDefV));
 t_sup(T1, T2) ->
   ?union(U1) = force_union(T1),
   ?union(U2) = force_union(T2),
@@ -2343,7 +2695,7 @@ force_union(T = ?list(_, _, _)) ->    ?list_union(T);
 force_union(T = ?nil) ->              ?list_union(T);
 force_union(T = ?number(_, _)) ->     ?number_union(T);
 force_union(T = ?opaque(_)) ->        ?opaque_union(T);
-force_union(T = ?map(_)) ->           ?map_union(T);
+force_union(T = ?map(_,_,_)) ->       ?map_union(T);
 force_union(T = ?tuple(_, _, _)) ->   ?tuple_union(T);
 force_union(T = ?tuple_set(_)) ->     ?tuple_union(T);
 force_union(T = ?matchstate(_, _)) -> ?matchstate_union(T);
@@ -2380,7 +2732,7 @@ t_elements(?number(_, _) = T) ->
   end;
 t_elements(?opaque(_) = T) ->
   do_elements(T);
-t_elements(?map(_) = T) -> [T];
+t_elements(?map(_,_,_) = T) -> [T];
 t_elements(?tuple(_, _, _) = T) -> [T];
 t_elements(?tuple_set(_) = TS) ->
   case t_tuple_subtypes(TS) of
@@ -2462,6 +2814,25 @@ t_inf(?identifier(Set1), ?identifier(Set2), _Opaques) ->
     ?none -> ?none;
     Set -> ?identifier(Set)
   end;
+t_inf(?map(_, ADefK, ADefV) = A, ?map(_, BDefK, BDefV) = B, _Opaques) ->
+  %% Because it simplifies the anonymous function, we allow Pairs to temporarily
+  %% contain mandatory pairs with none values, since all such cases should
+  %% result in a none result.
+  Pairs =
+    map_pairwise_merge(
+      %% For optional keys in both maps, when the infinimum is none, we have
+      %% essentially concluded that K must not be a key in the map.
+      fun(K, ?opt, V1, ?opt, V2) -> {K, ?opt, t_inf(V1, V2)};
+	 %% When a key is optional in one map, but mandatory in another, it
+	 %% becomes mandatory in the infinumum
+	 (K, _, V1, _, V2) -> {K, ?mand, t_inf(V1, V2)}
+      end, A, B),
+  %% If the infinimum of any mandatory values is ?none, the entire map infinimum
+  %% is ?none.
+  case lists:any(fun({_,?mand,?none})->true; ({_,_,_}) -> false end, Pairs) of
+    true -> t_none();
+    false -> t_map(Pairs, t_inf(ADefK, BDefK), t_inf(ADefV, BDefV))
+  end;
 t_inf(?matchstate(Pres1, Slots1), ?matchstate(Pres2, Slots2), _Opaques) ->
   ?matchstate(t_inf(Pres1, Pres2), t_inf(Slots1, Slots2));
 t_inf(?nil, ?nil, _Opaques) -> ?nil;
@@ -2970,9 +3341,9 @@ t_subst_dict(?tuple(Elements, _Arity, _Tag), Dict) ->
   t_tuple([t_subst_dict(E, Dict) || E <- Elements]);
 t_subst_dict(?tuple_set(_) = TS, Dict) ->
   t_sup([t_subst_dict(T, Dict) || T <- t_tuple_subtypes(TS)]);
-t_subst_dict(?map(Pairs), Dict) ->
-  ?map([{t_subst_dict(K, Dict), t_subst_dict(V, Dict)} ||
-         {K, V} <- Pairs]);
+t_subst_dict(?map(Pairs, DefK, DefV), Dict) ->
+  t_map([{K, MNess, t_subst_dict(V, Dict)} || {K, MNess, V} <- Pairs],
+	t_subst_dict(DefK, Dict), t_subst_dict(DefV, Dict));
 t_subst_dict(?opaque(Es), Dict) ->
   List = [Opaque#opaque{args = [t_subst_dict(Arg, Dict) || Arg <- Args],
                         struct = t_subst_dict(S, Dict)} ||
@@ -3022,9 +3393,9 @@ t_subst_aux(?tuple(Elements, _Arity, _Tag), VarMap) ->
   t_tuple([t_subst_aux(E, VarMap) || E <- Elements]);
 t_subst_aux(?tuple_set(_) = TS, VarMap) ->
   t_sup([t_subst_aux(T, VarMap) || T <- t_tuple_subtypes(TS)]);
-t_subst_aux(?map(Pairs), VarMap) ->
-  ?map([{t_subst_aux(K, VarMap), t_subst_aux(V, VarMap)} ||
-         {K, V} <- Pairs]);
+t_subst_aux(?map(Pairs, DefK, DefV), VarMap) ->
+  t_map([{K, MNess, t_subst_aux(V, VarMap)} || {K, MNess, V} <- Pairs],
+	t_subst_aux(DefK, VarMap), t_subst_aux(DefV, VarMap));
 t_subst_aux(?opaque(Es), VarMap) ->
    List = [Opaque#opaque{args = [t_subst_aux(Arg, VarMap) || Arg <- Args],
                          struct = t_subst_aux(S, VarMap)} ||
@@ -3104,6 +3475,23 @@ t_unify(?tuple_set(List1) = T1, ?tuple_set(List2) = T2, VarMap) ->
     {Tuples, NewVarMap} -> {t_sup(Tuples), NewVarMap}
   catch _:_ -> throw({mismatch, T1, T2})
   end;
+t_unify(?map(_, ADefK, ADefV) = A, ?map(_, BDefK, BDefV) = B, VarMap0) ->
+  {DefK, VarMap1} = t_unify(ADefK, BDefK, VarMap0),
+  {DefV, VarMap2} = t_unify(ADefV, BDefV, VarMap1),
+  {Pairs, VarMap} =
+    map_pairwise_merge_foldr(
+      fun(K, MNess, V1, MNess, V2, {Pairs0, VarMap3}) ->
+	  %% We know that the keys unify and do not contain variables, or they
+	  %% would not be singletons
+	  %% TODO: Should V=?none (known missing keys) be handled special?
+	  {V, VarMap4} = t_unify(V1, V2, VarMap3),
+	  {[{K,MNess,V}|Pairs0], VarMap4};
+	 (K, _, V1, _, V2, {Pairs0, VarMap3}) ->
+	  %% One mandatory and one optional; what should be done in this case?
+	  {V, VarMap4} = t_unify(V1, V2, VarMap3),
+	  {[{K,?mand,V}|Pairs0], VarMap4}
+      end, {[], VarMap2}, A, B),
+  {t_map(Pairs, DefK, DefV), VarMap};
 t_unify(?opaque(_) = T1, ?opaque(_) = T2, VarMap) ->
   t_unify(t_opaque_structure(T1), t_opaque_structure(T2), VarMap);
 t_unify(T1, ?opaque(_) = T2, VarMap) ->
@@ -3307,7 +3695,7 @@ t_subtract_list(T, []) ->
 -spec t_subtract(erl_type(), erl_type()) -> erl_type().
 
 t_subtract(_, ?any) -> ?none;
-t_subtract(_, ?var(_)) -> ?none;
+t_subtract(T, ?var(_)) -> T;
 t_subtract(?any, _) -> ?any;
 t_subtract(?var(_) = T, _) -> T;
 t_subtract(T, ?unit) -> T;
@@ -3460,8 +3848,50 @@ t_subtract(?product(Elements1) = T1, ?product(Elements2)) ->
 	_ -> T1
       end
   end;
-t_subtract(?map(_) = T, _) ->  % XXX: very crude; will probably need refinement
-  T;
+t_subtract(?map(APairs, ADefK, ADefV) = A, ?map(_, BDefK, BDefV) = B) ->
+  case t_is_subtype(ADefK, BDefK) andalso t_is_subtype(ADefV, BDefV) of
+    false -> A;
+    true ->
+      %% We fold over the maps to produce a list of constraints, where
+      %% constraints are additional key-value pairs to put in Pairs. Only one
+      %% constraint need to be applied to produce a type that excludes the
+      %% right-hand-side type, so if more than one constraint is produced, we
+      %% just return the left-hand-side argument.
+      %%
+      %% Each case of the fold may either conclude that
+      %%  * The arguments constrain A at least as much as B, i.e. that A so far
+      %%    is a subtype of B. In that case they return false
+      %%  * That for the particular arguments, A being a subtype of B does not
+      %%    hold, but the infinimum of A and B is nonempty, and by narrowing a
+      %%    pair in A, we can create a type that excludes some elements in the
+      %%    infinumum. In that case, they will return that pair.
+      %%  * That for the particular arguments, A being a subtype of B does not
+      %%    hold, and either the infinumum of A and B is empty, or it is not
+      %%    possible with the current representation to create a type that
+      %%    excludes elements from B without also excluding elements that are
+      %%    only in A. In that case, it will return the pair from A unchanged.
+      case
+	map_pairwise_merge(
+	  %% If V1 is a subtype of V2, the case that K does not exist in A
+	  %% remain.
+	  fun(K, ?opt, V1, ?mand, V2) -> {K, ?opt, t_subtract(V1, V2)};
+	     (K, _,    V1, _,     V2) ->
+	      %% If we subtract an optional key, that leaves a mandatory key
+	      case t_subtract(V1, V2) of
+		?none -> false;
+		Partial -> {K, ?mand, Partial}
+	      end
+	  end, A, B)
+      of
+	  %% We produce a list of keys that are constrained. As only one of
+	  %% these should apply at a time, we can't represent the difference if
+	  %% more than one constraint is produced. If we applied all of them,
+	  %% that would make an underapproximation, which we must not do.
+	  [] -> ?none; %% A is a subtype of B
+	  [E] -> t_map(mapdict_store(E, APairs), ADefK, ADefV);
+	  _ -> A
+      end
+  end;
 t_subtract(?product(P1), _) ->
   ?product(P1);
 t_subtract(T, ?product(_)) ->
@@ -3592,6 +4022,11 @@ subtype_is_equal(T1, T2) ->
 t_is_instance(ConcreteType, Type) ->
   t_is_subtype(ConcreteType, t_unopaque(Type)).
 
+-spec t_do_overlap(erl_type(), erl_type()) -> boolean().
+
+t_do_overlap(TypeA, TypeB) ->
+  not (t_is_none_or_unit(t_inf(TypeA, TypeB))).
+
 -spec t_unopaque(erl_type()) -> erl_type().
 
 t_unopaque(T) ->
@@ -3622,12 +4057,17 @@ t_unopaque(?union([A,B,F,I,L,N,T,M,O,Map]), Opaques) ->
   UL = t_unopaque(L, Opaques),
   UT = t_unopaque(T, Opaques),
   UF = t_unopaque(F, Opaques),
+  UM = t_unopaque(M, Opaques),
   UMap = t_unopaque(Map, Opaques),
   {OF,UO} = case t_unopaque(O, Opaques) of
               ?opaque(_) = O1 -> {O1, []};
               Type -> {?none, [Type]}
             end,
-  t_sup([?union([A,B,UF,I,UL,N,UT,M,OF,UMap])|UO]);
+  t_sup([?union([A,B,UF,I,UL,N,UT,UM,OF,UMap])|UO]);
+t_unopaque(?map(Pairs,DefK,DefV), Opaques) ->
+  t_map([{K, MNess, t_unopaque(V, Opaques)} || {K, MNess, V} <- Pairs],
+	t_unopaque(DefK, Opaques),
+	t_unopaque(DefV, Opaques));
 t_unopaque(T, _) ->
   T.
 
@@ -3679,6 +4119,16 @@ t_limit_k(?opaque(Es), K) ->
             Opaque#opaque{struct = NewS}
           end || #opaque{struct = S} = Opaque <- set_to_list(Es)],
   ?opaque(ordsets:from_list(List));
+t_limit_k(?map(Pairs0, DefK0, DefV0), K) ->
+  Fun = fun({EK, MNess, EV}, {Exact, DefK1, DefV1}) ->
+	    LV = t_limit_k(EV, K - 1),
+	    case t_limit_k(EK, K - 1) of
+	      EK -> {[{EK,MNess,LV}|Exact], DefK1, DefV1};
+	      LK -> {Exact, t_sup(LK, DefK1), t_sup(LV, DefV1)}
+	    end
+	end,
+  {Pairs, DefK2, DefV2} = lists:foldr(Fun, {[], DefK0, DefV0}, Pairs0),
+  t_map(Pairs, t_limit_k(DefK2, K - 1), t_limit_k(DefV2, K - 1));
 t_limit_k(T, _K) -> T.
 
 %%============================================================================
@@ -3753,6 +4203,9 @@ t_map(Fun, ?opaque(Set)) ->
         [] -> ?none;
         _ -> ?opaque(ordsets:from_list(L))
       end);
+t_map(Fun, ?map(Pairs,DefK,DefV)) ->
+  %% TODO:
+  Fun(t_map(Pairs, Fun(DefK), Fun(DefV)));
 t_map(Fun, T) ->
   Fun(T).
 
@@ -3894,8 +4347,23 @@ t_to_string(?float, _RecDict) -> "float()";
 t_to_string(?number(?any, ?unknown_qual), _RecDict) -> "number()";
 t_to_string(?product(List), RecDict) -> 
   "<" ++ comma_sequence(List, RecDict) ++ ">";
-t_to_string(?map(Pairs), RecDict) ->
-    "#{" ++ map_pairs_to_string(Pairs,RecDict) ++ "}";
+t_to_string(?map([],?any,?any), _RecDict) -> "map()";
+t_to_string(?map(Pairs0,DefK,DefV), RecDict) ->
+  {Pairs, ExtraEl} =
+    case {DefK, DefV} of
+      {?none, ?none} -> {Pairs0, []};
+      {?any, ?any} -> {Pairs0, ["..."]};
+      _ -> {Pairs0 ++ [{DefK,?opt,DefV}], []}
+    end,
+  Tos = fun(T) -> case T of
+		    ?any -> "_";
+		    _ -> t_to_string(T, RecDict)
+		  end end,
+  StrMand = [{Tos(K),Tos(V)}||{K,?mand,V}<-Pairs],
+  StrOpt  = [{Tos(K),Tos(V)}||{K,?opt,V}<-Pairs],
+  "#{" ++ string:join([K ++ ":=" ++ V||{K,V}<-StrMand]
+		      ++ [K ++ "=>" ++ V||{K,V}<-StrOpt]
+		      ++ ExtraEl, ", ") ++ "}";
 t_to_string(?tuple(?any, ?any, ?any), _RecDict) -> "tuple()";
 t_to_string(?tuple(Elements, _Arity, ?any), RecDict) ->   
   "{" ++ comma_sequence(Elements, RecDict) ++ "}";
@@ -3916,12 +4384,6 @@ t_to_string(?var(Id), _RecDict) when is_integer(Id) ->
   flat_format("var(~w)", [Id]).
 
 
-map_pairs_to_string([],_) -> [];
-map_pairs_to_string(Pairs,RecDict) ->
-    StrPairs = [{t_to_string(K,RecDict),t_to_string(V,RecDict)}||{K,V}<-Pairs],
-    string:join([K ++ "=>" ++ V||{K,V}<-StrPairs], ", ").
-
-
 record_to_string(Tag, [_|Fields], FieldNames, RecDict) ->
   FieldStrings = record_fields_to_string(Fields, FieldNames, RecDict, []),
   "#" ++ atom_to_string(Tag) ++ "{" ++ string:join(FieldStrings, ",") ++ "}".
@@ -4164,8 +4626,26 @@ t_from_form({type, _L, list, []}, _TypeNames, _ET, _S, _MR, _V, _D, L) ->
 t_from_form({type, _L, list, [Type]}, TypeNames, ET, S, MR, V, D, L) ->
   {T, L1} = t_from_form(Type, TypeNames, ET, S, MR, V, D - 1, L - 1),
   {t_list(T), L1};
-t_from_form({type, _L, map, _}, TypeNames, ET, S, MR, V, D, L) ->
-  builtin_type(map, t_map([]), TypeNames, ET, S, MR, V, D, L);
+t_from_form({type, _L, map, any}, TypeNames, ET, S, MR, V, D, L) ->
+  builtin_type(map, t_map(), TypeNames, ET, S, MR, V, D, L);
+t_from_form({type, _L, map, List}, TypeNames, ET, S, MR, V, D, L) ->
+  {Pairs1, L5} =
+    fun PairsFromForm(_, L1) when L1 =< 0 -> {[{?any,?opt,?any}], L1};
+	PairsFromForm([], L1) -> {[], L1};
+	PairsFromForm([{type, _, Oper, [KF, VF]}|T], L1) ->
+	{Key, L2} = t_from_form(KF, TypeNames, ET, S, MR, V, D - 1, L1),
+	{Val, L3} = t_from_form(VF, TypeNames, ET, S, MR, V, D - 1, L2),
+	{Pairs0, L4} = PairsFromForm(T, L3 - 1),
+	case Oper of
+	  map_field_assoc -> {[{Key,?opt, Val}|Pairs0], L4};
+	  map_field_exact -> {[{Key,?mand,Val}|Pairs0], L4}
+	end
+    end(List, L),
+  try
+    {Pairs, DefK, DefV} = map_from_form(Pairs1, [], [], [], ?none, ?none),
+    {t_map(Pairs, DefK, DefV), L5}
+  catch none -> {t_none(), L5}
+  end;
 t_from_form({type, _L, mfa, []}, _TypeNames, _ET, _S, _MR, _V, _D, L) ->
   {t_mfa(), L};
 t_from_form({type, _L, module, []}, _TypeNames, _ET, _S, _MR, _V, _D, L) ->
@@ -4495,6 +4975,50 @@ list_from_form([H|Tail], TypeNames, ET, S, MR, V, D, L) ->
   {T1, L2} = list_from_form(Tail, TypeNames, ET, S, MR, V, D, L1),
   {[H1|T1], L2}.
 
+%% Sorts, combines non-singleton pairs, and applies precendence and
+%% mandatoriness rules.
+map_from_form([], ShdwPs, MKs, Pairs, DefK, DefV) ->
+  verify_possible(MKs, ShdwPs),
+  {promote_to_mand(MKs, Pairs), DefK, DefV};
+map_from_form([{SKey,MNess,Val}|SPairs], ShdwPs0, MKs0, Pairs0, DefK0, DefV0) ->
+  Key = lists:foldl(fun({K,_},S)->t_subtract(S,K)end, SKey, ShdwPs0),
+  ShdwPs = case Key of ?none -> ShdwPs0; _ -> [{Key,Val}|ShdwPs0] end,
+  MKs = case MNess of ?mand -> [SKey|MKs0]; ?opt -> MKs0 end,
+  if MNess =:= ?mand, SKey =:= ?none -> throw(none);
+     true -> ok
+  end,
+  {Pairs, DefK, DefV} =
+    case is_singleton_type(Key) of
+      true ->
+	MNess1 = case Val =:= ?none of true -> ?opt; false -> MNess end,
+	{mapdict_insert({Key,MNess1,Val}, Pairs0), DefK0, DefV0};
+      false ->
+	case Key =:= ?none orelse Val =:= ?none of
+	  true  -> {Pairs0, DefK0,             DefV0};
+	  false -> {Pairs0, t_sup(DefK0, Key), t_sup(DefV0, Val)}
+	end
+    end,
+  map_from_form(SPairs, ShdwPs, MKs, Pairs, DefK, DefV).
+
+%% Verifies that all mandatory keys are possible, throws 'none' otherwise
+verify_possible(MKs, ShdwPs) ->
+  lists:foreach(fun(M) -> verify_possible_1(M, ShdwPs) end, MKs).
+
+verify_possible_1(M, ShdwPs) ->
+  case lists:any(fun({K,_}) -> t_inf(M, K) =/= ?none end, ShdwPs) of
+    true -> ok;
+    false -> throw(none)
+  end.
+
+-spec promote_to_mand([erl_type()], t_map_dict()) -> t_map_dict().
+
+promote_to_mand(_, []) -> [];
+promote_to_mand(MKs, [E={K,_,V}|T]) ->
+  [case lists:any(fun(M) -> t_is_equal(K,M) end, MKs) of
+     true -> {K, ?mand, V};
+     false -> E
+   end|promote_to_mand(MKs, T)].
+
 -spec t_check_record_fields(parse_form(), sets:set(mfa()), site(),
                             mod_records()) -> ok.
 
@@ -4627,8 +5151,13 @@ t_form_to_string({type, _L, iodata, []}) -> "iodata()";
 t_form_to_string({type, _L, iolist, []}) -> "iolist()";
 t_form_to_string({type, _L, list, [Type]}) -> 
   "[" ++ t_form_to_string(Type) ++ "]";
-t_form_to_string({type, _L, map, _}) ->
-  "#{}";
+t_form_to_string({type, _L, map, any}) -> "map()";
+t_form_to_string({type, _L, map, Args}) ->
+  "#{" ++ string:join(t_form_to_string_list(Args), ",") ++ "}";
+t_form_to_string({type, _L, map_field_assoc, [Key, Val]}) ->
+  t_form_to_string(Key) ++ "=>" ++ t_form_to_string(Val);
+t_form_to_string({type, _L, map_field_exact, [Key, Val]}) ->
+  t_form_to_string(Key) ++ ":=" ++ t_form_to_string(Val);
 t_form_to_string({type, _L, mfa, []}) -> "mfa()";
 t_form_to_string({type, _L, module, []}) -> "module()";
 t_form_to_string({type, _L, node, []}) -> "node()";
@@ -4789,11 +5318,70 @@ do_opaque(?union(List) = Type, Opaques, Pred) ->
 do_opaque(Type, _Opaques, Pred) ->
   Pred(Type).
 
-map_keys(?map(Pairs)) ->
-  [K || {K, _} <- Pairs].
+map_all_values(?map(Pairs,_,DefV)) ->
+  [DefV|[V || {V, _, _} <- Pairs]].
+
+map_all_keys(?map(Pairs,DefK,_)) ->
+  [DefK|[K || {_, _, K} <- Pairs]].
+
+map_all_types(M) ->
+  map_all_keys(M) ++ map_all_values(M).
+
+%% Tests if a type has exactly one possible value.
+-spec t_is_singleton(erl_type()) -> boolean().
+
+t_is_singleton(Type) ->
+  t_is_singleton(Type, 'universe').
+
+-spec t_is_singleton(erl_type(), opaques()) -> boolean().
+
+t_is_singleton(Type, Opaques) ->
+  do_opaque(Type, Opaques, fun is_singleton_type/1).
+
+%% Incomplete; not all representable singleton types are included.
+is_singleton_type(?nil) -> true;
+is_singleton_type(?atom(?any)) -> false;
+is_singleton_type(?atom(Set)) ->
+  ordsets:size(Set) =:= 1;
+is_singleton_type(?int_range(V, V)) -> true;
+is_singleton_type(?int_set(Set)) ->
+  ordsets:size(Set) =:= 1;
+is_singleton_type(?tuple(Types, Arity, _)) when is_integer(Arity) ->
+  lists:all(fun is_singleton_type/1, Types);
+is_singleton_type(?tuple_set([{Arity, [OnlyTuple]}])) when is_integer(Arity) ->
+  is_singleton_type(OnlyTuple);
+is_singleton_type(?map(Pairs, ?none, ?none)) ->
+  lists:all(fun({_,MNess,V}) -> MNess =:= ?mand andalso is_singleton_type(V)
+	    end, Pairs);
+is_singleton_type(_) ->
+  false.
+
+%% Returns the only possible value of a singleton type.
+-spec t_singleton_to_term(erl_type(), opaques()) -> term().
 
-map_values(?map(Pairs)) ->
-  [V || {_, V} <- Pairs].
+t_singleton_to_term(Type, Opaques) ->
+  do_opaque(Type, Opaques, fun singleton_type_to_term/1).
+
+singleton_type_to_term(?nil) -> [];
+singleton_type_to_term(?atom(Set)) when Set =/= ?any ->
+  case ordsets:size(Set) of
+    1 -> hd(ordsets:to_list(Set));
+    _ -> error(badarg)
+  end;
+singleton_type_to_term(?int_range(V, V)) -> V;
+singleton_type_to_term(?int_set(Set)) ->
+  case ordsets:size(Set) of
+    1 -> hd(ordsets:to_list(Set));
+    _ -> error(badarg)
+  end;
+singleton_type_to_term(?tuple(Types, Arity, _)) when is_integer(Arity) ->
+  lists:map(fun singleton_type_to_term/1, Types);
+singleton_type_to_term(?tuple_set([{Arity, [OnlyTuple]}]))
+  when is_integer(Arity) ->
+  singleton_type_to_term(OnlyTuple);
+singleton_type_to_term(?map(Pairs, ?none, ?none)) ->
+  maps:from_list([{singleton_type_to_term(K), singleton_type_to_term(V)}
+		  || {K,?mand,V} <- Pairs]).
 
 %% -----------------------------------
 %% Set
diff --git a/lib/runtime_tools/src/msacc.erl b/lib/runtime_tools/src/msacc.erl
index 612effa5aa..4db5dbec91 100644
--- a/lib/runtime_tools/src/msacc.erl
+++ b/lib/runtime_tools/src/msacc.erl
@@ -32,18 +32,18 @@
 
 -type msacc_data() :: [msacc_data_thread()].
 
--type msacc_data_thread() :: #{ '$type' => msacc_data,
-                                type => msacc_type(), id => msacc_id(),
-                                counters => msacc_data_counters() }.
+-type msacc_data_thread() :: #{ '$type' := msacc_data,
+                                type := msacc_type(), id := msacc_id(),
+                                counters := msacc_data_counters() }.
 -type msacc_data_counters() :: #{ msacc_state() => non_neg_integer()}.
 
 -type msacc_stats() :: [msacc_stats_thread()].
--type msacc_stats_thread() :: #{ '$type' => msacc_stats,
-                                 type => msacc_type(), id => msacc_id(),
-                                 system => float(),
-                                 counters => msacc_stats_counters()}.
--type msacc_stats_counters() :: #{ msacc_state() => #{ thread => float(),
-                                                       system => float()}}.
+-type msacc_stats_thread() :: #{ '$type' := msacc_stats,
+                                 type := msacc_type(), id := msacc_id(),
+                                 system := float(),
+                                 counters := msacc_stats_counters()}.
+-type msacc_stats_counters() :: #{ msacc_state() => #{ thread := float(),
+                                                       system := float()}}.
 
 
 -type msacc_type() :: scheduler | aux | async.
diff --git a/lib/stdlib/examples/erl_id_trans.erl b/lib/stdlib/examples/erl_id_trans.erl
index c2e345763a..eab2ec4164 100644
--- a/lib/stdlib/examples/erl_id_trans.erl
+++ b/lib/stdlib/examples/erl_id_trans.erl
@@ -671,6 +671,10 @@ map_pair_types([{type,Line,map_field_assoc,[K,V]}|Ps]) ->
     K1 = type(K),
     V1 = type(V),
     [{type,Line,map_field_assoc,[K1,V1]}|map_pair_types(Ps)];
+map_pair_types([{type,Line,map_field_exact,[K,V]}|Ps]) ->
+    K1 = type(K),
+    V1 = type(V),
+    [{type,Line,map_field_exact,[K1,V1]}|map_pair_types(Ps)];
 map_pair_types([]) -> [].
 
 field_types([{type,Line,field_type,[{atom,La,A},T]}|Fs]) ->
diff --git a/lib/stdlib/src/epp.erl b/lib/stdlib/src/epp.erl
index 936c095aef..55a818e87c 100644
--- a/lib/stdlib/src/epp.erl
+++ b/lib/stdlib/src/epp.erl
@@ -1,7 +1,7 @@
 %%
 %% %CopyrightBegin%
 %%
-%% Copyright Ericsson AB 1996-2015. All Rights Reserved.
+%% Copyright Ericsson AB 1996-2016. All Rights Reserved.
 %%
 %% Licensed under the Apache License, Version 2.0 (the "License");
 %% you may not use this file except in compliance with the License.
@@ -43,7 +43,10 @@
 -type name() :: atom().
 -type argspec() :: 'none'                       %No arguments
                  | non_neg_integer().           %Number of arguments
+-type argnames() :: [atom()].
 -type tokens() :: [erl_scan:token()].
+-type predef() :: 'undefined' | {'none', tokens()}.
+-type userdef() :: {argspec(), {argnames(), tokens()}}.
 -type used() :: {name(), argspec()}.
 
 -type function_name_type() :: 'undefined'
@@ -63,7 +66,7 @@
               sstk=[] :: [#epp{}],              %State stack
               path=[] :: [file:name()],         %Include-path
               macs = #{}		        %Macros (don't care locations)
-	            :: #{name() => {argspec(), tokens()}},
+	            :: #{name() => predef() | [userdef()]},
               uses = #{}			%Macro use structure
 	            :: #{name() => [{argspec(), [used()]}]},
               default_encoding = ?DEFAULT_ENCODING :: source_encoding(),
diff --git a/lib/stdlib/src/erl_parse.yrl b/lib/stdlib/src/erl_parse.yrl
index 6f8e5e8449..a896de4f1c 100644
--- a/lib/stdlib/src/erl_parse.yrl
+++ b/lib/stdlib/src/erl_parse.yrl
@@ -170,9 +170,16 @@ fun_type -> '(' top_types ')' '->' top_type
                                    : {type, ?anno('$1'), 'fun',
                                       [{type, ?anno('$1'), product, '$2'},'$5']}.
 
+map_pair_types  -> '...'           : [{type, ?anno('$1'), map_field_assoc,
+                                       [{type, ?anno('$1'), any, []},
+                                        {type, ?anno('$1'), any, []}]}].
 map_pair_types -> map_pair_type                    : ['$1'].
 map_pair_types -> map_pair_type ',' map_pair_types : ['$1'|'$3'].
-map_pair_type  -> top_type '=>' top_type           : {type, ?anno('$2'), map_field_assoc,['$1','$3']}.
+
+map_pair_type  -> top_type '=>' top_type  : {type, ?anno('$2'),
+                                             map_field_assoc,['$1','$3']}.
+map_pair_type  -> top_type ':=' top_type  : {type, ?anno('$2'),
+                                             map_field_exact,['$1','$3']}.
 
 field_types -> field_type                 : ['$1'].
 field_types -> field_type ',' field_types : ['$1'|'$3'].
@@ -810,7 +817,8 @@ Erlang code.
                      | {'type', anno(), 'map', [af_map_pair_type()]}.
 
 -type af_map_pair_type() ::
-        {'type', anno(), 'map_field_assoc', [abstract_type()]}.
+        {'type', anno(), 'map_field_assoc', [abstract_type()]}
+      | {'type', anno(), 'map_field_exact', [abstract_type()]}.
 
 -type af_predefined_type() ::
         {'type', anno(), type_name(),  [abstract_type()]}.
diff --git a/lib/stdlib/src/erl_pp.erl b/lib/stdlib/src/erl_pp.erl
index c5177aca90..ca764675fc 100644
--- a/lib/stdlib/src/erl_pp.erl
+++ b/lib/stdlib/src/erl_pp.erl
@@ -1,7 +1,7 @@
 %%
 %% %CopyrightBegin%
 %%
-%% Copyright Ericsson AB 1996-2015. All Rights Reserved.
+%% Copyright Ericsson AB 1996-2016. All Rights Reserved.
 %%
 %% Licensed under the Apache License, Version 2.0 (the "License");
 %% you may not use this file except in compliance with the License.
@@ -344,11 +344,31 @@ binary_type(I1, I2) ->
 map_type(Fs) ->
     {first,[$#],map_pair_types(Fs)}.
 
-map_pair_types(Fs) ->
+map_pair_types(Fs0) ->
+    Fs = replace_any_map(Fs0),
     tuple_type(Fs, fun map_pair_type/2).
 
+replace_any_map([{type,Line,map_field_assoc,[KType,VType]}]=Fs) ->
+    IsAny = fun({type,_,any,[]}) -> true;
+    %%         ({var,_,'_'}) -> true;
+               (_) -> false
+            end,
+    case IsAny(KType) andalso IsAny(VType) of
+        true ->
+            [{type,Line,map_field_assoc,any}];
+        false ->
+            Fs
+    end;
+replace_any_map([F|Fs]) ->
+    [F|replace_any_map(Fs)];
+replace_any_map([]) -> [].
+
+map_pair_type({type,_Line,map_field_assoc,any}, _Prec) ->
+    leaf("...");
 map_pair_type({type,_Line,map_field_assoc,[KType,VType]}, Prec) ->
-    {list,[{cstep,[ltype(KType, Prec),leaf(" =>")],ltype(VType, Prec)}]}.
+    {list,[{cstep,[ltype(KType, Prec),leaf(" =>")],ltype(VType, Prec)}]};
+map_pair_type({type,_Line,map_field_exact,[KType,VType]}, Prec) ->
+    {list,[{cstep,[ltype(KType, Prec),leaf(" :=")],ltype(VType, Prec)}]}.
 
 record_type(Name, Fields) ->
     {first,[record_name(Name)],field_types(Fields)}.
diff --git a/lib/stdlib/src/io_lib.erl b/lib/stdlib/src/io_lib.erl
index f070a7192d..ad98bc0420 100644
--- a/lib/stdlib/src/io_lib.erl
+++ b/lib/stdlib/src/io_lib.erl
@@ -112,14 +112,14 @@
 
 -type format_spec() ::
         #{
-           control_char => char(),
-           args         => [any()],
-           width        => 'none' | integer(),
-           adjust       => 'left' | 'right',
-           precision    => 'none' | integer(),
-           pad_char     => char(),
-           encoding     => 'unicode' | 'latin1',
-           strings      => boolean()
+           control_char := char(),
+           args         := [any()],
+           width        := 'none' | integer(),
+           adjust       := 'left' | 'right',
+           precision    := 'none' | integer(),
+           pad_char     := char(),
+           encoding     := 'unicode' | 'latin1',
+           strings      := boolean()
          }.
 
 %%----------------------------------------------------------------------
diff --git a/lib/stdlib/src/maps.erl b/lib/stdlib/src/maps.erl
index ba9ad4f549..5dafdb282a 100644
--- a/lib/stdlib/src/maps.erl
+++ b/lib/stdlib/src/maps.erl
@@ -31,6 +31,7 @@
          new/0, put/3, remove/2, take/2,
          to_list/1, update/3, values/1]).
 
+%% Shadowed by erl_bif_types: maps:get/2
 -spec get(Key,Map) -> Value when
     Key :: term(),
     Map :: map(),
@@ -46,7 +47,7 @@ get(_,_) -> erlang:nif_error(undef).
 
 find(_,_) -> erlang:nif_error(undef).
 
-
+%% Shadowed by erl_bif_types: maps:from_list/1
 -spec from_list(List) -> Map when
     List :: [{Key,Value}],
     Key :: term(),
@@ -56,6 +57,7 @@ find(_,_) -> erlang:nif_error(undef).
 from_list(_) -> erlang:nif_error(undef).
 
 
+%% Shadowed by erl_bif_types: maps:is_key/2
 -spec is_key(Key,Map) -> boolean() when
     Key :: term(),
     Map :: map().
@@ -71,6 +73,7 @@ is_key(_,_) -> erlang:nif_error(undef).
 keys(_) -> erlang:nif_error(undef).
 
 
+%% Shadowed by erl_bif_types: maps:merge/2
 -spec merge(Map1,Map2) -> Map3 when
     Map1 :: map(),
     Map2 :: map(),
@@ -86,6 +89,7 @@ merge(_,_) -> erlang:nif_error(undef).
 new() -> erlang:nif_error(undef).
 
 
+%% Shadowed by erl_bif_types: maps:put/3
 -spec put(Key,Value,Map1) -> Map2 when
     Key :: term(),
     Value :: term(),
@@ -110,6 +114,7 @@ remove(_,_) -> erlang:nif_error(undef).
 
 take(_,_) -> erlang:nif_error(undef).
 
+%% Shadowed by erl_bif_types: maps:to_list/1
 -spec to_list(Map) -> [{Key,Value}] when
     Map :: map(),
     Key :: term(),
@@ -118,6 +123,7 @@ take(_,_) -> erlang:nif_error(undef).
 to_list(_) -> erlang:nif_error(undef).
 
 
+%% Shadowed by erl_bif_types: maps:update/3
 -spec update(Key,Value,Map1) -> Map2 when
     Key :: term(),
     Value :: term(),
diff --git a/lib/stdlib/src/rand.erl b/lib/stdlib/src/rand.erl
index d455abf7b0..93409d95df 100644
--- a/lib/stdlib/src/rand.erl
+++ b/lib/stdlib/src/rand.erl
@@ -44,11 +44,11 @@
 %% This depends on the algorithm handler function
 -type alg_seed() :: exs64_state() | exsplus_state() | exs1024_state().
 %% This is the algorithm handler function within this module
--type alg_handler() :: #{type      => alg(),
-			 max       => integer(),
-			 next      => fun(),
-			 uniform   => fun(),
-			 uniform_n => fun()}.
+-type alg_handler() :: #{type      := alg(),
+			 max       := integer(),
+			 next      := fun(),
+			 uniform   := fun(),
+			 uniform_n := fun()}.
 
 %% Internal state
 -opaque state() :: {alg_handler(), alg_seed()}.
diff --git a/lib/stdlib/src/supervisor.erl b/lib/stdlib/src/supervisor.erl
index 37c3927739..38b764541a 100644
--- a/lib/stdlib/src/supervisor.erl
+++ b/lib/stdlib/src/supervisor.erl
@@ -57,8 +57,8 @@
                   | {'global', Name :: atom()}
                   | {'via', Module :: module(), Name :: any()}
                   | pid().
--type child_spec() :: #{id => child_id(),       % mandatory
-			start => mfargs(),      % mandatory
+-type child_spec() :: #{id := child_id(),       % mandatory
+			start := mfargs(),      % mandatory
 			restart => restart(),   % optional
 			shutdown => shutdown(), % optional
 			type => worker(),       % optional
diff --git a/lib/stdlib/test/erl_pp_SUITE.erl b/lib/stdlib/test/erl_pp_SUITE.erl
index 6dc285e448..a48ba7b5b7 100644
--- a/lib/stdlib/test/erl_pp_SUITE.erl
+++ b/lib/stdlib/test/erl_pp_SUITE.erl
@@ -50,7 +50,7 @@
 
 	  otp_6321/1, otp_6911/1, otp_6914/1, otp_8150/1, otp_8238/1,
 	  otp_8473/1, otp_8522/1, otp_8567/1, otp_8664/1, otp_9147/1,
-          otp_10302/1, otp_10820/1, otp_11100/1, otp_11861/1]).
+          otp_10302/1, otp_10820/1, otp_11100/1, otp_11861/1, pr_1014/1]).
 
 %% Internal export.
 -export([ehook/6]).
@@ -79,7 +79,7 @@ groups() ->
      {tickets, [],
       [otp_6321, otp_6911, otp_6914, otp_8150, otp_8238,
        otp_8473, otp_8522, otp_8567, otp_8664, otp_9147,
-       otp_10302, otp_10820, otp_11100, otp_11861]}].
+       otp_10302, otp_10820, otp_11100, otp_11861, pr_1014]}].
 
 init_per_suite(Config) ->
     Config.
@@ -902,6 +902,7 @@ maps_syntax(Config) when is_list(Config) ->
           "-compile(export_all).\n"
           "-type t1() :: map().\n"
           "-type t2() :: #{ atom() => integer(), atom() => float() }.\n"
+          "-type t3() :: #{ atom() := integer(), atom() := float() }.\n"
           "-type u() :: #{a => (I :: integer()) | (A :: atom()),\n"
           "               (X :: atom()) | (Y :: atom()) =>\n"
           "                   (I :: integer()) | (A :: atom())}.\n"
@@ -1106,6 +1107,24 @@ otp_11861(Config) when is_list(Config) ->
 pf(Form) ->
     lists:flatten(erl_pp:form(Form, none)).
 
+pr_1014(Config) ->
+    ok = pp_forms(<<"-type t() :: #{_ => _}. ">>),
+    ok = pp_forms(<<"-type t() :: #{any() => _}. ">>),
+    ok = pp_forms(<<"-type t() :: #{_ => any()}. ">>),
+    ok = pp_forms(<<"-type t() :: #{any() => any()}. ">>),
+    ok = pp_forms(<<"-type t() :: #{...}. ">>),
+    ok = pp_forms(<<"-type t() :: #{atom() := integer(), ...}. ">>),
+
+    FileName = filename('pr_1014.erl', Config),
+    C = <<"-module pr_1014.\n"
+          "-compile export_all.\n"
+          "-type m() :: #{..., a := integer()}.\n">>,
+    ok = file:write_file(FileName, C),
+    {error,[{_,[{3,erl_parse,["syntax error before: ","','"]}]}],_} =
+        compile:file(FileName, [return]),
+
+    ok.
+
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 
 compile(Config, Tests) ->
diff --git a/system/doc/reference_manual/typespec.xml b/system/doc/reference_manual/typespec.xml
index c5d24a96b5..9e26e9058d 100644
--- a/system/doc/reference_manual/typespec.xml
+++ b/system/doc/reference_manual/typespec.xml
@@ -132,15 +132,18 @@
         | nonempty_list(Type)                  %% Proper non-empty list
 
   Map :: map()                                 %% stands for a map of any size
-       | #{}                                   %% stands for a map of any size
+       | #{}                                   %% stands for the empty map
        | #{PairList}
 
   Tuple :: tuple()                             %% stands for a tuple of any size
          | {}
          | {TList}
 
-  PairList :: Type => Type
-            | Type => Type, PairList
+  PairList :: Pair
+            | Pair, PairList
+
+  Pair :: Type := Type                         %% notes a pair that must be present
+        | Type => Type
 
   TList :: Type
          | Type, TList
@@ -170,6 +173,23 @@
     The notation <c>[]</c> specifies the singleton type for the empty list.
   </p>
   <p>
+    The general form of maps is <c>#{PairList}</c>. The key types in
+    <c>PairList</c> are allowed to overlap, and if they do, the leftmost pair
+    takes precedence. A map value does not belong to this type if contains a key
+    that is not in <c>PairList</c>.
+  </p>
+  <p>
+    Because it is common to end a map type with <c>any() =&gt; any()</c> to denote
+    that keys that do not belong to any other pair in <c>PairList</c> are
+    allowed, and may map to any value, the shorthand notation <c>...</c> is
+    allowed as the last pair of a map type.
+  </p>
+  <p>
+    Notice that the syntactic representation of <c>map()</c> is <c>#{...}</c>
+    (or <c>#{_ =&gt; _}</c>, or <c>#{any() =&gt; any()}</c>), not <c>#{}</c>.
+    The notation <c>#{}</c> specifies the singleton type for the empty map.
+  </p>
+  <p>
     For convenience, the following types are also built-in. 
     They can be thought as predefined aliases for the type unions also shown in 
     the table.
@@ -302,12 +322,6 @@
     This is described in <seealso marker="#typeinrecords">
     Type Information in Record Declarations</seealso>.
   </p>
-  <note>
-    <p>Map types, both <c>map()</c> and <c>#{...}</c>,
-      are considered experimental during OTP 17.</p>
-    <p>No type information of maps pairs, only the containing map types,
-      are used by Dialyzer in OTP 17.</p>
-  </note>
   </section>
 
   <section>