Merge branch 'egil/maps/OTP-11616'

* egil/maps/OTP-11616: (112 commits)
  compiler: Add core compile test for maps
  compiler: Fix core parse for Maps
  compiler: Fixup #map_pair{} spec
  erts: Strengthen map_SUITE tests
  erts: Update maps_fold test to respect maps:fold/3
  stdlib: Make maps:fold/3 order-independent
  erts: Fixup enif_make_map_put on windows
  erts: Update preloaded erts_internal.beam
  hipe: Fixup update cerl pretty printer
  erts: Add map construction to driver API
  dialyzer: Add maps tests
  dialyzer: Remove dead code
  dialyzer: Reflect map_pair core changes in dialyzer
  hipe: Update cerl pretty printer
  compiler: Update inliner tests
  compiler: Squash #c_map_pair_*{} to #c_map_pair{}
  compiler: Squash #k_map_pair_*{} to #k_map_pair{}
  preloaded: Fixup export cmp_term in erts_internal
  erts: Change 'size' argument of enif_get_map_size from int* to size_t*
  erts: Fix compile error for halfword emulator
  ...

14 files changed, 466 insertions, 5 deletions

diff --git a/lib/stdlib/examples/erl_id_trans.erl b/lib/stdlib/examples/erl_id_trans.erl
index 2c842fafc7..5fcb74310e 100644
--- a/lib/stdlib/examples/erl_id_trans.erl
+++ b/lib/stdlib/examples/erl_id_trans.erl
@@ -144,6 +144,13 @@ pattern({cons,Line,H0,T0}) ->
 pattern({tuple,Line,Ps0}) ->
     Ps1 = pattern_list(Ps0),
     {tuple,Line,Ps1};
+pattern({map,Line,Ps0}) ->
+    Ps1 = pattern_list(Ps0),
+    {map,Line,Ps1};
+pattern({map_field_exact,Line,K,V}) ->
+    Ke = pattern(K),
+    Ve = pattern(V),
+    {map_field_exact,Line,Ke,Ve};
 %%pattern({struct,Line,Tag,Ps0}) ->
 %%    Ps1 = pattern_list(Ps0),
 %%    {struct,Line,Tag,Ps1};
@@ -251,6 +258,20 @@ gexpr({float,Line,F}) -> {float,Line,F};
 gexpr({atom,Line,A}) -> {atom,Line,A};
 gexpr({string,Line,S}) -> {string,Line,S};
 gexpr({nil,Line}) -> {nil,Line};
+gexpr({map,Line,Map0,Es0}) ->
+    [Map1|Es1] = gexpr_list([Map0|Es0]),
+    {map,Line,Map1,Es1};
+gexpr({map,Line,Es0}) ->
+    Es1 = gexpr_list(Es0),
+    {map,Line,Es1};
+gexpr({map_field_assoc,Line,K,V}) ->
+    Ke = gexpr(K),
+    Ve = gexpr(V),
+    {map_field_assoc,Line,Ke,Ve};
+gexpr({map_field_exact,Line,K,V}) ->
+    Ke = gexpr(K),
+    Ve = gexpr(V),
+    {map_field_exact,Line,Ke,Ve};
 gexpr({cons,Line,H0,T0}) ->
     H1 = gexpr(H0),
     T1 = gexpr(T0),				%They see the same variables
@@ -356,6 +377,20 @@ expr({bc,Line,E0,Qs0}) ->
 expr({tuple,Line,Es0}) ->
     Es1 = expr_list(Es0),
     {tuple,Line,Es1};
+expr({map,Line,Map0,Es0}) ->
+    [Map1|Es1] = exprs([Map0|Es0]),
+    {map,Line,Map1,Es1};
+expr({map,Line,Es0}) ->
+    Es1 = exprs(Es0),
+    {map,Line,Es1};
+expr({map_field_assoc,Line,K,V}) ->
+    Ke = expr(K),
+    Ve = expr(V),
+    {map_field_assoc,Line,Ke,Ve};
+expr({map_field_exact,Line,K,V}) ->
+    Ke = expr(K),
+    Ve = expr(V),
+    {map_field_exact,Line,Ke,Ve};
 %%expr({struct,Line,Tag,Es0}) ->
 %%    Es1 = pattern_list(Es0),
 %%    {struct,Line,Tag,Es1};
diff --git a/lib/stdlib/src/Makefile b/lib/stdlib/src/Makefile
index f3387d669b..9ab2cd4134 100644
--- a/lib/stdlib/src/Makefile
+++ b/lib/stdlib/src/Makefile
@@ -91,6 +91,7 @@ MODULES= \
 	lib \
 	lists \
 	log_mf_h \
+	maps \
 	math \
 	ms_transform \
 	otp_internal \
diff --git a/lib/stdlib/src/erl_eval.erl b/lib/stdlib/src/erl_eval.erl
index 18d8148b15..5f96795d92 100644
--- a/lib/stdlib/src/erl_eval.erl
+++ b/lib/stdlib/src/erl_eval.erl
@@ -239,6 +239,29 @@ expr({record,_,Name,_}, _Bs, _Lf, _Ef, _RBs) ->
     erlang:raise(error, {undef_record,Name}, stacktrace());
 expr({record,_,_,Name,_}, _Bs, _Lf, _Ef, _RBs) ->
     erlang:raise(error, {undef_record,Name}, stacktrace());
+
+%% map
+expr({map_field_assoc,_,EK, EV}, Bs0, Lf, Ef, RBs) ->
+    {value,K,Bs1} = expr(EK, Bs0, Lf, Ef, none),
+    {value,V,Bs2} = expr(EV, Bs0, Lf, Ef, none),
+    ret_expr({map_assoc,K,V}, merge_bindings(Bs1,Bs2), RBs);
+expr({map_field_exact,_,EK, EV}, Bs0, Lf, Ef, RBs) ->
+    {value,K,Bs1} = expr(EK, Bs0, Lf, Ef, none),
+    {value,V,Bs2} = expr(EV, Bs0, Lf, Ef, none),
+    ret_expr({map_exact,K,V}, merge_bindings(Bs1,Bs2), RBs);
+expr({map,_, Binding,Es}, Bs0, Lf, Ef, RBs) ->
+    {value, Map0, Bs1} = expr(Binding, Bs0, Lf, Ef, RBs),
+    {Vs,Bs} = expr_list(Es, Bs1, Lf, Ef),
+    ret_expr(lists:foldl(fun
+		({map_assoc,K,V}, Mi) -> maps:put(K,V,Mi);
+		({map_exact,K,V}, Mi) -> maps:update(K,V,Mi)
+	end, Map0, Vs), Bs, RBs);
+expr({map,_,Es}, Bs0, Lf, Ef, RBs) ->
+    {Vs,Bs} = expr_list(Es, Bs0, Lf, Ef),
+    ret_expr(lists:foldl(fun
+		({map_assoc,K,V}, Mi) -> maps:put(K,V,Mi)
+	    end, maps:new(), Vs), Bs, RBs);
+
 expr({block,_,Es}, Bs, Lf, Ef, RBs) ->
     exprs(Es, Bs, Lf, Ef, RBs);
 expr({'if',_,Cs}, Bs, Lf, Ef, RBs) ->
@@ -994,6 +1017,7 @@ type_test(port) -> is_port;
 type_test(function) -> is_function;
 type_test(binary) -> is_binary;
 type_test(record) -> is_record;
+type_test(map) -> is_map;
 type_test(Test) -> Test.
 
 
@@ -1075,6 +1099,9 @@ match1({tuple,_,Elts}, Tuple, Bs, BBs)
     match_tuple(Elts, Tuple, 1, Bs, BBs);
 match1({tuple,_,_}, _, _Bs, _BBs) ->
     throw(nomatch);
+match1({map,_,Fs}, Map, Bs, BBs) ->
+    match_map(Fs, Map, Bs, BBs);
+
 match1({bin, _, Fs}, <<_/bitstring>>=B, Bs0, BBs) ->
     eval_bits:match_bits(Fs, B, Bs0, BBs,
 			 match_fun(BBs),
@@ -1118,6 +1145,18 @@ match_tuple([E|Es], Tuple, I, Bs0, BBs) ->
 match_tuple([], _, _, Bs, _BBs) ->
     {match,Bs}.
 
+match_map([{map_field_exact, _, K, V}|Fs], Map, Bs0, BBs) ->
+    Vm = try
+	{value, Ke, _} = expr(K, new_bindings()),
+	maps:get(Ke,Map)
+    catch error:_ ->
+	throw(nomatch)
+    end,
+    {match, Bs} = match1(V, Vm, Bs0, BBs),
+    match_map(Fs, Map, Bs, BBs);
+match_map([], _, Bs, _) ->
+    {match, Bs}.
+
 %% match_list(PatternList, TermList, Bindings) ->
 %%	{match,NewBindings} | nomatch
 %%  Try to match a list of patterns against a list of terms with the
diff --git a/lib/stdlib/src/erl_expand_records.erl b/lib/stdlib/src/erl_expand_records.erl
index 776b433613..4741bef6b9 100644
--- a/lib/stdlib/src/erl_expand_records.erl
+++ b/lib/stdlib/src/erl_expand_records.erl
@@ -132,6 +132,12 @@ pattern({cons,Line,H,T}, St0) ->
 pattern({tuple,Line,Ps}, St0) ->
     {TPs,St1} = pattern_list(Ps, St0),
     {{tuple,Line,TPs},St1};
+pattern({map,Line,Ps}, St0) ->
+    {TPs,St1} = pattern_list(Ps, St0),
+    {{map,Line,TPs},St1};
+pattern({map_field_exact,Line,Key,V0}, St0) ->
+    {V,St1} = pattern(V0, St0),
+    {{map_field_exact,Line,Key,V},St1};
 %%pattern({struct,Line,Tag,Ps}, St0) ->
 %%    {TPs,TPsvs,St1} = pattern_list(Ps, St0),
 %%    {{struct,Line,Tag,TPs},TPsvs,St1};
@@ -301,6 +307,20 @@ expr({bc,Line,E0,Qs0}, St0) ->
 expr({tuple,Line,Es0}, St0) ->
     {Es1,St1} = expr_list(Es0, St0),
     {{tuple,Line,Es1},St1};
+expr({map,Line,Es0}, St0) ->
+    {Es1,St1} = expr_list(Es0, St0),
+    {{map,Line,Es1},St1};
+expr({map,Line,Var,Es0}, St0) ->
+    {Es1,St1} = expr_list(Es0, St0),
+    {{map,Line,Var,Es1},St1};
+expr({map_field_assoc,Line,K0,V0}, St0) ->
+    {K,St1} = expr(K0, St0),
+    {V,St2} = expr(V0, St1),
+    {{map_field_assoc,Line,K,V},St2};
+expr({map_field_exact,Line,K0,V0}, St0) ->
+    {K,St1} = expr(K0, St0),
+    {V,St2} = expr(V0, St1),
+    {{map_field_exact,Line,K,V},St2};
 %%expr({struct,Line,Tag,Es0}, Vs, St0) ->
 %%    {Es1,Esvs,Esus,St1} = expr_list(Es0, Vs, St0),
 %%    {{struct,Line,Tag,Es1},Esvs,Esus,St1};
diff --git a/lib/stdlib/src/erl_internal.erl b/lib/stdlib/src/erl_internal.erl
index 28de7205ea..edfb097de0 100644
--- a/lib/stdlib/src/erl_internal.erl
+++ b/lib/stdlib/src/erl_internal.erl
@@ -70,6 +70,7 @@ guard_bif(bit_size, 1) -> true;
 guard_bif(byte_size, 1) -> true;
 guard_bif(element, 2) -> true;
 guard_bif(self, 0) -> true;
+guard_bif(map_size, 1) -> true;
 guard_bif(node, 0) -> true;
 guard_bif(node, 1) -> true;
 guard_bif(tuple_size, 1) -> true;
@@ -82,6 +83,7 @@ guard_bif(is_function, 1) -> true;
 guard_bif(is_function, 2) -> true;
 guard_bif(is_integer, 1) -> true;
 guard_bif(is_list, 1) -> true;
+guard_bif(is_map, 1) -> true;
 guard_bif(is_number, 1) -> true;
 guard_bif(is_pid, 1) -> true;
 guard_bif(is_port, 1) -> true;
@@ -113,6 +115,7 @@ new_type_test(is_function, 1) -> true;
 new_type_test(is_function, 2) -> true;
 new_type_test(is_integer, 1) -> true;
 new_type_test(is_list, 1) -> true;
+new_type_test(is_map, 1) -> true;
 new_type_test(is_number, 1) -> true;
 new_type_test(is_pid, 1) -> true;
 new_type_test(is_port, 1) -> true;
@@ -315,6 +318,7 @@ bif(is_function, 1) -> true;
 bif(is_function, 2) -> true;
 bif(is_integer, 1) -> true;
 bif(is_list, 1) -> true;
+bif(is_map, 1) -> true;
 bif(is_number, 1) -> true;
 bif(is_pid, 1) -> true;
 bif(is_port, 1) -> true;
@@ -335,6 +339,7 @@ bif(list_to_pid, 1) -> true;
 bif(list_to_tuple, 1) -> true;
 bif(load_module, 2) -> true;
 bif(make_ref, 0) -> true;
+bif(map_size,1) -> true;
 bif(max,2) -> true;
 bif(min,2) -> true;
 bif(module_loaded, 1) -> true;
diff --git a/lib/stdlib/src/erl_lint.erl b/lib/stdlib/src/erl_lint.erl
index f0d50df4c7..f630db6032 100644
--- a/lib/stdlib/src/erl_lint.erl
+++ b/lib/stdlib/src/erl_lint.erl
@@ -225,6 +225,8 @@ format_error({too_many_arguments,Arity}) ->
 		  "maximum allowed is ~w", [Arity,?MAX_ARGUMENTS]);
 %% --- patterns and guards ---
 format_error(illegal_pattern) -> "illegal pattern";
+format_error({illegal_map_key_variable,K}) ->
+    io_lib:format("illegal use of variable ~w in map",[K]);
 format_error(illegal_bin_pattern) ->
     "binary patterns cannot be matched in parallel using '='";
 format_error(illegal_expr) -> "illegal expression";
@@ -232,6 +234,9 @@ format_error({illegal_guard_local_call, {F,A}}) ->
     io_lib:format("call to local/imported function ~w/~w is illegal in guard",
 		  [F,A]);
 format_error(illegal_guard_expr) -> "illegal guard expression";
+%% --- maps ---
+format_error(illegal_map_construction) ->
+    "only association operators '=>' are allowed in map construction";
 %% --- records ---
 format_error({undefined_record,T}) ->
     io_lib:format("record ~w undefined", [T]);
@@ -1366,6 +1371,19 @@ pattern({cons,_Line,H,T}, Vt, Old,  Bvt, St0) ->
     {vtmerge_pat(Hvt, Tvt),vtmerge_pat(Bvt1,Bvt2),St2};
 pattern({tuple,_Line,Ps}, Vt, Old, Bvt, St) ->
     pattern_list(Ps, Vt, Old, Bvt, St);
+pattern({map,_Line,Ps}, Vt, Old, Bvt, St) ->
+    pattern_list(Ps, Vt, Old, Bvt, St);
+pattern({map_field_assoc,Line,_,_}, _, _, _, St) ->
+    {[],[],add_error(Line, illegal_pattern, St)};
+pattern({map_field_exact,Line,KP,VP}, Vt, Old, Bvt0, St0) ->
+    %% if the key pattern has variables we should fail
+    case expr(KP,[],St0) of
+	{[],_} ->
+	    pattern(VP, Vt, Old, Bvt0, St0);
+	{[Var|_],_} ->
+	    %% found variables in key expression
+	    {Vt,Old,add_error(Line,{illegal_map_key_variable,element(1,Var)},St0)}
+    end;
 %%pattern({struct,_Line,_Tag,Ps}, Vt, Old, Bvt, St) ->
 %%    pattern_list(Ps, Vt, Old, Bvt, St);
 pattern({record_index,Line,Name,Field}, _Vt, _Old, _Bvt, St) ->
@@ -1753,6 +1771,14 @@ gexpr({cons,_Line,H,T}, Vt, St) ->
     gexpr_list([H,T], Vt, St);
 gexpr({tuple,_Line,Es}, Vt, St) ->
     gexpr_list(Es, Vt, St);
+gexpr({map,_Line,Es}, Vt, St) ->
+    gexpr_list(Es, Vt, St);
+gexpr({map,_Line,Src,Es}, Vt, St) ->
+    gexpr_list([Src|Es], Vt, St);
+gexpr({map_field_assoc,_Line,K,V}, Vt, St) ->
+    gexpr_list([K,V], Vt, St);
+gexpr({map_field_exact,_Line,K,V}, Vt, St) ->
+    gexpr_list([K,V], Vt, St);
 gexpr({record_index,Line,Name,Field}, _Vt, St) ->
     check_record(Line, Name, St,
                  fun (Dfs, St1) -> record_field(Field, Name, Dfs, St1) end );
@@ -1970,6 +1996,24 @@ expr({bc,_Line,E,Qs}, Vt, St) ->
     handle_comprehension(E, Qs, Vt, St);
 expr({tuple,_Line,Es}, Vt, St) ->
     expr_list(Es, Vt, St);
+expr({map,Line,Es}, Vt, St) ->
+    {Rvt,St1} = expr_list(Es,Vt,St),
+    case is_valid_map_construction(Es) of
+	true  -> {Rvt,St1};
+	false -> {[],add_error(Line,illegal_map_construction,St1)}
+    end;
+expr({map,_Line,Src,Es}, Vt, St) ->
+    expr_list([Src|Es], Vt, St);
+expr({map_field_assoc,Line,K,V}, Vt, St) ->
+    case is_valid_map_key(K,St) of
+	true  -> expr_list([K,V], Vt, St);
+	{false,Var} -> {[],add_error(Line,{illegal_map_key_variable,Var},St)}
+    end;
+expr({map_field_exact,Line,K,V}, Vt, St) ->
+    case is_valid_map_key(K,St) of
+	true  -> expr_list([K,V], Vt, St);
+	{false,Var} -> {[],add_error(Line,{illegal_map_key_variable,Var},St)}
+    end;
 expr({record_index,Line,Name,Field}, _Vt, St) ->
     check_record(Line, Name, St,
                  fun (Dfs, St1) -> record_field(Field, Name, Dfs, St1) end);
@@ -2229,6 +2273,20 @@ is_valid_call(Call) ->
         _ -> true
     end.
 
+%% check_map_construction
+%% Only #{ K => V }, i.e. assoc is a valid construction
+is_valid_map_construction([{map_field_assoc,_,_,_}|Es]) ->
+    is_valid_map_construction(Es);
+is_valid_map_construction([]) -> true;
+is_valid_map_construction(_)  -> false.
+
+is_valid_map_key(K,St) ->
+    case expr(K,[],St) of
+	{[],_} -> true;
+	{[Var|_],_} ->
+	    {false,element(1,Var)}
+    end.
+
 %% record_def(Line, RecordName, [RecField], State) -> State.
 %%  Add a record definition if it does not already exist. Normalise
 %%  so that all fields have explicit initial value.
@@ -2549,6 +2607,13 @@ check_type({type, L, range, [From, To]}, SeenVars, St) ->
 	    _ -> add_error(L, {type_syntax, range}, St)
 	end,
     {SeenVars, St1};
+check_type({type, _L, map, any}, SeenVars, St) -> {SeenVars, St};
+check_type({type, _L, map, Pairs}, SeenVars, St) ->
+    lists:foldl(fun(Pair, {AccSeenVars, AccSt}) ->
+			check_type(Pair, AccSeenVars, AccSt)
+		end, {SeenVars, St}, Pairs);
+check_type({type, _L, map_field_assoc, Dom, Range}, SeenVars, St) ->
+    check_type({type, -1, product, [Dom, Range]}, SeenVars, St);
 check_type({type, _L, tuple, any}, SeenVars, St) -> {SeenVars, St};
 check_type({type, _L, any}, SeenVars, St) -> {SeenVars, St};
 check_type({type, L, binary, [Base, Unit]}, SeenVars, St) ->
@@ -2654,6 +2719,7 @@ is_default_type({iodata, 0}) -> true;
 is_default_type({iolist, 0}) -> true;
 is_default_type({list, 0}) -> true;
 is_default_type({list, 1}) -> true;
+is_default_type({map, 0}) -> true;
 is_default_type({maybe_improper_list, 0}) -> true;
 is_default_type({maybe_improper_list, 2}) -> true;
 is_default_type({mfa, 0}) -> true;
diff --git a/lib/stdlib/src/erl_parse.yrl b/lib/stdlib/src/erl_parse.yrl
index 59a05a48ee..6316db7054 100644
--- a/lib/stdlib/src/erl_parse.yrl
+++ b/lib/stdlib/src/erl_parse.yrl
@@ -34,6 +34,7 @@ binary_comprehension
 tuple
 %struct
 record_expr record_tuple record_field record_fields
+map_expr map_tuple map_field map_field_assoc map_field_exact map_fields map_key
 if_expr if_clause if_clauses case_expr cr_clause cr_clauses receive_expr
 fun_expr fun_clause fun_clauses atom_or_var integer_or_var
 try_expr try_catch try_clause try_clauses
@@ -47,6 +48,7 @@ opt_bit_size_expr bit_size_expr opt_bit_type_list bit_type_list bit_type
 top_type top_type_100 top_types type typed_expr typed_attr_val
 type_sig type_sigs type_guard type_guards fun_type fun_type_100 binary_type
 type_spec spec_fun typed_exprs typed_record_fields field_types field_type
+map_pair_types map_pair_type
 bin_base_type bin_unit_type type_200 type_300 type_400 type_500.
 
 Terminals
@@ -59,7 +61,7 @@ char integer float atom string var
 '*' '/' 'div' 'rem' 'band' 'and'
 '+' '-' 'bor' 'bxor' 'bsl' 'bsr' 'or' 'xor'
 '++' '--'
-'==' '/=' '=<' '<' '>=' '>' '=:=' '=/=' '<='
+'==' '/=' '=<' '<' '>=' '>' '=:=' '=/=' '<=' '=>' ':='
 '<<' '>>'
 '!' '=' '::' '..' '...'
 'spec' 'callback' % helper
@@ -154,6 +156,8 @@ type -> '[' ']'                           : {type, ?line('$1'), nil, []}.
 type -> '[' top_type ']'                  : {type, ?line('$1'), list, ['$2']}.
 type -> '[' top_type ',' '...' ']'        : {type, ?line('$1'),
                                              nonempty_list, ['$2']}.
+type -> '#' '{' '}'                       : {type, ?line('$1'), map, []}.
+type -> '#' '{' map_pair_types '}'        : {type, ?line('$1'), map, '$3'}.
 type -> '{' '}'                           : {type, ?line('$1'), tuple, []}.
 type -> '{' top_types '}'                 : {type, ?line('$1'), tuple, '$2'}.
 type -> '#' atom '{' '}'                  : {type, ?line('$1'), record, ['$2']}.
@@ -175,6 +179,10 @@ fun_type -> '(' top_types ')' '->' top_type
                                    : {type, ?line('$1'), 'fun',
                                       [{type, ?line('$1'), product, '$2'},'$5']}.
 
+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, ?line('$2'), map_field_assoc,'$1','$3'}.
+
 field_types -> field_type                 : ['$1'].
 field_types -> field_type ',' field_types : ['$1'|'$3'].
 
@@ -247,6 +255,7 @@ expr_500 -> expr_600 : '$1'.
 
 expr_600 -> prefix_op expr_700 :
 	?mkop1('$1', '$2').
+expr_600 -> map_expr : '$1'.
 expr_600 -> expr_700 : '$1'.
 
 expr_700 -> function_call : '$1'.
@@ -327,6 +336,30 @@ tuple -> '{' exprs '}' : {tuple,?line('$1'),'$2'}.
 %%struct -> atom tuple :
 %%	{struct,?line('$1'),element(3, '$1'),element(3, '$2')}.
 
+map_expr -> '#' map_tuple :
+	{map, ?line('$1'),'$2'}.
+map_expr -> expr_max '#' map_tuple :
+	{map, ?line('$2'),'$1','$3'}.
+map_expr -> map_expr '#' map_tuple :
+	{map, ?line('$2'),'$1','$3'}.
+
+map_tuple -> '{' '}' : [].
+map_tuple -> '{' map_fields '}' : '$2'.
+
+map_fields -> map_field : ['$1'].
+map_fields -> map_field ',' map_fields : ['$1' | '$3'].
+
+map_field -> map_field_assoc : '$1'.
+map_field -> map_field_exact : '$1'.
+
+map_field_assoc -> map_key '=>' expr :
+	{map_field_assoc,?line('$1'),'$1','$3'}.
+
+map_field_exact -> map_key ':=' expr :
+	{map_field_exact,?line('$1'),'$1','$3'}.
+
+map_key -> expr : '$1'.
+
 
 %% N.B. This is called from expr_700.
 %% N.B. Field names are returned as the complete object, even if they are
@@ -648,6 +681,8 @@ skip_paren(Type) ->
 
 build_gen_type({atom, La, tuple}) ->
     {type, La, tuple, any};
+build_gen_type({atom, La, map}) ->
+    {type, La, map, any};
 build_gen_type({atom, La, Name}) ->
     {type, La, Name, []}.
 
@@ -860,6 +895,12 @@ normalise({cons,_,Head,Tail}) ->
     [normalise(Head)|normalise(Tail)];
 normalise({tuple,_,Args}) ->
     list_to_tuple(normalise_list(Args));
+normalise({map,_,Pairs}=M) ->
+    maps:from_list(lists:map(fun
+		%% only allow '=>'
+		({map_field_assoc,_,K,V}) -> {normalise(K),normalise(V)};
+		(_) -> erlang:error({badarg,M})
+	    end, Pairs));
 %% Special case for unary +/-.
 normalise({op,_,'+',{char,_,I}}) -> I;
 normalise({op,_,'+',{integer,_,I}}) -> I;
@@ -1060,3 +1101,5 @@ get_attribute(L, Name) ->
 
 get_attributes(L) ->
     erl_scan:attributes_info(L).
+
+%% vim: ft=erlang
diff --git a/lib/stdlib/src/erl_scan.erl b/lib/stdlib/src/erl_scan.erl
index 4ba6dd01fa..ae59d5f44f 100644
--- a/lib/stdlib/src/erl_scan.erl
+++ b/lib/stdlib/src/erl_scan.erl
@@ -569,7 +569,7 @@ scan1("++"++Cs, St, Line, Col, Toks) ->
     tok2(Cs, St, Line, Col, Toks, "++", '++', 2);
 scan1("+"=Cs, _St, Line, Col, Toks) ->
     {more,{Cs,Col,Toks,Line,[],fun scan/6}};
-%% =:= =/= =< ==
+%% =:= =/= =< == =>
 scan1("=:="++Cs, St, Line, Col, Toks) ->
     tok2(Cs, St, Line, Col, Toks, "=:=", '=:=', 3);
 scan1("=:"=Cs, _St, Line, Col, Toks) ->
@@ -580,6 +580,8 @@ scan1("=/"=Cs, _St, Line, Col, Toks) ->
     {more,{Cs,Col,Toks,Line,[],fun scan/6}};
 scan1("=<"++Cs, St, Line, Col, Toks) ->
     tok2(Cs, St, Line, Col, Toks, "=<", '=<', 2);
+scan1("=>"++Cs, St, Line, Col, Toks) ->
+    tok2(Cs, St, Line, Col, Toks, "=>", '=>', 2);
 scan1("=="++Cs, St, Line, Col, Toks) ->
     tok2(Cs, St, Line, Col, Toks, "==", '==', 2);
 scan1("="=Cs, _St, Line, Col, Toks) ->
@@ -594,6 +596,9 @@ scan1("||"++Cs, St, Line, Col, Toks) ->
     tok2(Cs, St, Line, Col, Toks, "||", '||', 2);
 scan1("|"=Cs, _St, Line, Col, Toks) ->
     {more,{Cs,Col,Toks,Line,[],fun scan/6}};
+%% :=
+scan1(":="++Cs, St, Line, Col, Toks) ->
+    tok2(Cs, St, Line, Col, Toks, ":=", ':=', 2);
 %% :-
 scan1(":-"++Cs, St, Line, Col, Toks) ->
     tok2(Cs, St, Line, Col, Toks, ":-", ':-', 2);
diff --git a/lib/stdlib/src/io_lib.erl b/lib/stdlib/src/io_lib.erl
index 375d05f359..adc9a0cf5f 100644
--- a/lib/stdlib/src/io_lib.erl
+++ b/lib/stdlib/src/io_lib.erl
@@ -257,7 +257,9 @@ write(T, D) when is_tuple(T) ->
 	     [write(element(1, T), D-1)|
               write_tail(tl(tuple_to_list(T)), D-1, $,)],
 	     $}]
-    end.
+    end;
+%write(Term, D)  when is_map(Term) -> write_map(Term, D);
+write(Term, D) -> write_map(Term, D).
 
 %% write_tail(List, Depth, CharacterBeforeDots)
 %%  Test the terminating case first as this looks better with depth.
@@ -275,6 +277,18 @@ write_port(Port) ->
 write_ref(Ref) ->
     erlang:ref_to_list(Ref).
 
+write_map(Map, D) when is_integer(D) ->
+    [$#,${,write_map_body(maps:to_list(Map), D),$}].
+
+write_map_body(_, 0) -> "...";
+write_map_body([],_) -> [];
+write_map_body([{K,V}],D) -> write_map_assoc(K,V,D);
+write_map_body([{K,V}|KVs], D) ->
+    [write_map_assoc(K,V,D),$, | write_map_body(KVs,D-1)].
+
+write_map_assoc(K,V,D) ->
+    [write(K,D - 1),"=>",write(V,D-1)].
+
 write_binary(B, D) when is_integer(D) ->
     [$<,$<,write_binary_body(B, D),$>,$>].
 
diff --git a/lib/stdlib/src/io_lib_pretty.erl b/lib/stdlib/src/io_lib_pretty.erl
index 7637ad7a3d..f02a7921f8 100644
--- a/lib/stdlib/src/io_lib_pretty.erl
+++ b/lib/stdlib/src/io_lib_pretty.erl
@@ -101,6 +101,7 @@ print(Term, Col, Ll, D, M, RecDefFun, Enc, Str) when Col =< 0 ->
     print(Term, 1, Ll, D, M, RecDefFun, Enc, Str);
 print(Term, Col, Ll, D, M0, RecDefFun, Enc, Str) when is_tuple(Term);
                                                       is_list(Term);
+                                                      is_map(Term);
                                                       is_bitstring(Term) ->
     If = {_S, Len} = print_length(Term, D, RecDefFun, Enc, Str),
     M = max_cs(M0, Len),
@@ -137,6 +138,10 @@ pp({{tuple,true,L}, _Len}, Col, Ll, M, TInd, Ind, LD, W) ->
     [${, pp_tag_tuple(L, Col, Ll, M, TInd, Ind, LD, W + 1), $}];
 pp({{tuple,false,L}, _Len}, Col, Ll, M, TInd, Ind, LD, W) ->
     [${, pp_list(L, Col + 1, Ll, M, TInd, indent(1, Ind), LD, $,, W + 1), $}];
+pp({{map,Pairs},_Len}, Col, Ll, M, TInd, Ind, LD, W) ->
+    [$#,${, pp_list(Pairs, Col + 2, Ll, M, TInd, indent(2, Ind), LD, $,, W + 1), $}];
+pp({{map_pair,K,V},_Len}, Col, Ll, M, TInd, Ind, LD, W) ->
+    [pp(K, Col, Ll, M, TInd, Ind, LD, W), " => ", pp(V, Col, Ll, M, TInd, Ind, LD, W)];
 pp({{record,[{Name,NLen} | L]}, _Len}, Col, Ll, M, TInd, Ind, LD, W) ->
     [Name, ${, pp_record(L, NLen, Col, Ll, M, TInd, Ind, LD, W + NLen+1), $}];
 pp({{bin,S}, _Len}, Col, Ll, M, _TInd, Ind, LD, W) ->
@@ -283,6 +288,10 @@ write({{tuple, _IsTagged, L}, _}) ->
     [${, write_list(L, $,), $}];
 write({{list, L}, _}) ->
     [$[, write_list(L, $|), $]];
+write({{map, Pairs}, _}) ->
+    [$#,${, write_list(Pairs, $,), $}];
+write({{map_pair, K, V}, _}) ->
+    [write(K)," => ",write(V)];
 write({{record, [{Name,_} | L]}, _}) ->
     [Name, ${, write_fields(L), $}];
 write({{bin, S}, _}) ->
@@ -331,6 +340,8 @@ print_length([], _D, _RF, _Enc, _Str) ->
     {"[]", 2};
 print_length({}, _D, _RF, _Enc, _Str) ->
     {"{}", 2};
+print_length(#{}=M, _D, _RF, _Enc, _Str) when map_size(M) =:= 0 ->
+    {"#{}", 3};
 print_length(List, D, RF, Enc, Str) when is_list(List) ->
     case Str andalso printable_list(List, D, Enc) of
         true ->
@@ -356,6 +367,8 @@ print_length(R, D, RF, Enc, Str) when is_atom(element(1, R)),
     end;
 print_length(Tuple, D, RF, Enc, Str) when is_tuple(Tuple) ->
     print_length_tuple(Tuple, D, RF, Enc, Str);
+print_length(Map, D, RF, Enc, Str) when is_map(Map) ->
+    print_length_map(Map, D, RF, Enc, Str);
 print_length(<<>>, _D, _RF, _Enc, _Str) ->
     {"<<>>", 4};
 print_length(<<_/bitstring>>, 1, _RF, _Enc, _Str) ->
@@ -389,6 +402,25 @@ print_length(Term, _D, _RF, _Enc, _Str) ->
     S = io_lib:write(Term),
     {S, lists:flatlength(S)}.
 
+print_length_map(_Map, 1, _RF, _Enc, _Str) ->
+    {"#{...}", 6};
+print_length_map(Map, D, RF, Enc, Str) when is_map(Map) ->
+    Pairs = print_length_map_pairs(maps:to_list(Map), D, RF, Enc, Str),
+    {{map, Pairs}, list_length(Pairs, 3)}.
+
+print_length_map_pairs([], _D, _RF, _Enc, _Str) ->
+    [];
+print_length_map_pairs(_Pairs, 1, _RF, _Enc, _Str) ->
+    {dots, 3};
+print_length_map_pairs([{K,V}|Pairs], D, RF, Enc, Str) ->
+    [print_length_map_pair(K,V,D-1,RF,Enc,Str) |
+     print_length_map_pairs(Pairs,D-1,RF,Enc,Str)].
+
+print_length_map_pair(K, V, D, RF, Enc, Str) ->
+    {KS, KL} = print_length(K, D, RF, Enc, Str),
+    {VS, VL} = print_length(V, D, RF, Enc, Str),
+    {{map_pair, {KS,KL}, {VS,VL}}, KL + VL}.
+
 print_length_tuple(_Tuple, 1, _RF, _Enc, _Str) ->
     {"{...}", 5};
 print_length_tuple(Tuple, D, RF, Enc, Str) ->
diff --git a/lib/stdlib/src/maps.erl b/lib/stdlib/src/maps.erl
new file mode 100644
index 0000000000..41de174e7d
--- /dev/null
+++ b/lib/stdlib/src/maps.erl
@@ -0,0 +1,198 @@
+%%
+%% %CopyrightBegin%
+%%
+%% Copyright Ericsson AB 2013. All Rights Reserved.
+%%
+%% The contents of this file are subject to the Erlang Public License,
+%% Version 1.1, (the "License"); you may not use this file except in
+%% compliance with the License. You should have received a copy of the
+%% Erlang Public License along with this software. If not, it can be
+%% retrieved online at http://www.erlang.org/.
+%%
+%% Software distributed under the License is distributed on an "AS IS"
+%% basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
+%% the License for the specific language governing rights and limitations
+%% under the License.
+%%
+%% %CopyrightEnd%
+%%
+
+-module(maps).
+
+-export([
+	fold/3,
+	map/2,
+	size/1,
+	without/2
+    ]).
+
+
+%%% BIFs
+-export([
+	get/2,
+	find/2,
+	from_list/1,
+	is_key/2,
+	keys/1,
+	merge/2,
+	new/0,
+	put/3,
+	remove/2,
+	to_list/1,
+	update/3,
+	values/1
+    ]).
+
+%% Shadowed by erl_bif_types: maps:get/3
+-spec get(Key,Map) -> Value when
+    Key :: term(),
+    Map :: map(),
+    Value :: term().
+
+get(_,_) -> erlang:nif_error(undef).
+
+
+%% Shadowed by erl_bif_types: maps:find/3
+-spec find(Key,Map) -> {ok, Value} | error when
+    Key :: term(),
+    Map :: map(),
+    Value :: term().
+
+find(_,_) -> erlang:nif_error(undef).
+
+
+%% Shadowed by erl_bif_types: maps:from_list/1
+-spec from_list([{Key,Value}]) -> Map when
+    Key :: term(),
+    Value :: term(),
+    Map :: map().
+
+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().
+
+is_key(_,_) -> erlang:nif_error(undef).
+
+
+%% Shadowed by erl_bif_types: maps:keys/1
+-spec keys(Map) -> Keys when
+    Map :: map(),
+    Keys :: [Key],
+    Key :: term().
+
+keys(_) -> erlang:nif_error(undef).
+
+
+%% Shadowed by erl_bif_types: maps:merge/2
+-spec merge(Map1,Map2) -> Map3 when
+    Map1 :: map(),
+    Map2 :: map(),
+    Map3 :: map().
+
+merge(_,_) -> erlang:nif_error(undef).
+
+
+
+%% Shadowed by erl_bif_types: maps:new/0
+-spec new() -> Map when
+    Map :: map().
+
+new() -> erlang:nif_error(undef).
+
+
+%% Shadowed by erl_bif_types: maps:put/3
+-spec put(Key,Value,Map1) -> Map2 when
+    Key :: term(),
+    Value :: term(),
+    Map1 :: map(),
+    Map2 :: map().
+
+put(_,_,_) -> erlang:nif_error(undef).
+
+
+%% Shadowed by erl_bif_types: maps:put/3
+-spec remove(Key,Map1) -> Map2 when
+    Key :: term(),
+    Map1 :: map(),
+    Map2 :: map().
+
+remove(_,_) -> erlang:nif_error(undef).
+
+
+%% Shadowed by erl_bif_types: maps:to_list/1
+-spec to_list(Map) -> [{Key,Value}] when
+    Map :: map(),
+    Key :: term(),
+    Value :: term().
+
+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(),
+    Map1 :: map(),
+    Map2 :: map().
+
+update(_,_,_) -> erlang:nif_error(undef).
+
+
+%% Shadowed by erl_bif_types: maps:values/1
+-spec values(Map) -> Keys when
+    Map :: map(),
+    Keys :: [Key],
+    Key :: term().
+
+values(_) -> erlang:nif_error(undef).
+
+
+%%% End of BIFs
+
+-spec fold(Fun,Init,Map) -> Acc when
+    Fun :: fun((K, V, AccIn) -> AccOut),
+    Init :: term(),
+    Acc :: term(),
+    AccIn :: term(),
+    AccOut :: term(),
+    Map :: map(),
+    K :: term(),
+    V :: term().
+
+fold(Fun, Init, Map) when is_function(Fun,3), is_map(Map) ->
+    lists:foldl(fun({K,V},A) -> Fun(K,V,A) end,Init,maps:to_list(Map)).
+
+-spec map(Fun,Map1) -> Map2 when
+    Fun :: fun((K, V1) -> V2),
+    Map1 :: map(),
+    Map2 :: map(),
+    K :: term(),
+    V1 :: term(),
+    V2 :: term().
+
+map(Fun, Map) when is_function(Fun, 2), is_map(Map) ->
+    maps:from_list(lists:map(fun
+		({K,V}) ->
+		    {K,Fun(K,V)}
+	    end,maps:to_list(Map))).
+
+
+-spec size(Map) -> non_neg_integer() when
+    Map :: map().
+
+size(Map) when is_map(Map) ->
+    erlang:map_size(Map).
+
+
+-spec without(Ks,Map1) -> Map2 when
+    Ks :: [K],
+    Map1 :: map(),
+    Map2 :: map(),
+    K :: term().
+
+without(Ks, M) when is_list(Ks), is_map(M) ->
+    maps:from_list([{K,V}||{K,V} <- maps:to_list(M), not lists:member(K, Ks)]).
diff --git a/lib/stdlib/src/ms_transform.erl b/lib/stdlib/src/ms_transform.erl
index 25b04fe45e..27dfcf52e1 100644
--- a/lib/stdlib/src/ms_transform.erl
+++ b/lib/stdlib/src/ms_transform.erl
@@ -910,6 +910,7 @@ bool_test(is_pid,1) -> true;
 bool_test(is_port,1) -> true;
 bool_test(is_reference,1) -> true;
 bool_test(is_tuple,1) -> true;
+bool_test(is_map,1) -> true;
 bool_test(is_binary,1) -> true;
 bool_test(is_function,1) -> true;
 bool_test(is_record,2) -> true;
@@ -924,6 +925,7 @@ real_guard_function(node,0) -> true;
 real_guard_function(node,1) -> true;
 real_guard_function(round,1) -> true;
 real_guard_function(size,1) -> true;
+real_guard_function(map_size,1) -> true;
 real_guard_function(tl,1) -> true;
 real_guard_function(trunc,1) -> true;
 real_guard_function(self,0) -> true;
diff --git a/lib/stdlib/src/stdlib.app.src b/lib/stdlib/src/stdlib.app.src
index a30685e830..a64b8e13c0 100644
--- a/lib/stdlib/src/stdlib.app.src
+++ b/lib/stdlib/src/stdlib.app.src
@@ -71,6 +71,7 @@
 	     lib,
 	     lists,
 	     log_mf_h,
+	     maps,
 	     math,
 	     ms_transform,
 	     orddict,
diff --git a/lib/stdlib/test/erl_scan_SUITE.erl b/lib/stdlib/test/erl_scan_SUITE.erl
index e628f7248d..447e159cd4 100644
--- a/lib/stdlib/test/erl_scan_SUITE.erl
+++ b/lib/stdlib/test/erl_scan_SUITE.erl
@@ -224,8 +224,8 @@ atoms() ->
 
 punctuations() ->
     L = ["<<", "<-", "<=", "<", ">>", ">=", ">", "->", "--",
-         "-", "++", "+", "=:=", "=/=", "=<", "==", "=", "/=",
-         "/", "||", "|", ":-", "::", ":"],
+         "-", "++", "+", "=:=", "=/=", "=<", "=>", "==", "=", "/=",
+         "/", "||", "|", ":=", ":-", "::", ":"],
     %% One token at a time:
     [begin
          W = list_to_atom(S),