Merge branch 'hb/type_fixes/OTP-11851'

* hb/type_fixes/OTP-11851:
  [stdlib] Simplify some linter warnings about specs
  Modify representation of the map type
  Disallow '_' as type variable
  Fix a -callback attribute bug
  Allow more type names

8 files changed, 267 insertions, 157 deletions

diff --git a/lib/edoc/src/edoc_specs.erl b/lib/edoc/src/edoc_specs.erl
index 211a354c74..3bf81c6503 100644
--- a/lib/edoc/src/edoc_specs.erl
+++ b/lib/edoc/src/edoc_specs.erl
@@ -362,7 +362,7 @@ d2e({type,_,map,any}) ->
     #t_map{ types = []};
 d2e({type,_,map,Es}) ->
     #t_map{ types = d2e(Es) };
-d2e({type,_,map_field_assoc,K,V}) ->
+d2e({type,_,map_field_assoc,[K,V]}) ->
     #t_map_field{ k_type = d2e(K), v_type=d2e(V) };
 d2e({type,_,map_field_exact,K,V}) ->
     #t_map_field{ k_type = d2e(K), v_type=d2e(V) };
@@ -388,6 +388,9 @@ d2e({record_field,L,_Name}=F) ->
 d2e({type,_,Name,Types0}) ->
     Types = d2e(Types0),
     typevar_anno(#t_type{name = #t_name{name = Name}, args = Types}, Types);
+d2e({user_type,_,Name,Types0}) ->
+    Types = d2e(Types0),
+    typevar_anno(#t_type{name = #t_name{name = Name}, args = Types}, Types);
 d2e({var,_,'_'}) ->
     #t_type{name = #t_name{name = ?TOP_TYPE}};
 d2e({var,_,TypeName}) ->
diff --git a/lib/hipe/cerl/erl_types.erl b/lib/hipe/cerl/erl_types.erl
index 6065b79664..473a9eba4a 100644
--- a/lib/hipe/cerl/erl_types.erl
+++ b/lib/hipe/cerl/erl_types.erl
@@ -4350,7 +4350,10 @@ t_from_form({type, _L, tuple, Args}, TypeNames, RecDict, VarDict) ->
 t_from_form({type, _L, union, Args}, TypeNames, RecDict, VarDict) ->
   {L, R} = list_from_form(Args, TypeNames, RecDict, VarDict),
   {t_sup(L), R};
+t_from_form({user_type, _L, Name, Args}, TypeNames, RecDict, VarDict) ->
+  type_from_form(Name, Args, TypeNames, RecDict, VarDict);
 t_from_form({type, _L, Name, Args}, TypeNames, RecDict, VarDict) ->
+  %% Compatibility. Modules compiled before 18.0.
   type_from_form(Name, Args, TypeNames, RecDict, VarDict);
 t_from_form({opaque, _L, Name, {Mod, Args, Rep}}, _TypeNames,
             _RecDict, _VarDict) ->
@@ -4588,9 +4591,12 @@ t_form_to_string({type, _L, Name, []} = T) ->
   try t_to_string(t_from_form(T))
   catch throw:{error, _} -> atom_to_string(Name) ++ "()"
   end;
-t_form_to_string({type, _L, Name, List}) -> 
+t_form_to_string({user_type, _L, Name, List}) ->
   flat_format("~w(~s)",
-              [Name, string:join(t_form_to_string_list(List), ",")]).
+              [Name, string:join(t_form_to_string_list(List), ",")]);
+t_form_to_string({type, L, Name, List}) ->
+  %% Compatibility. Modules compiled before 18.0.
+  t_form_to_string({user_type, L, Name, List}).
 
 t_form_to_string_list(List) ->
   t_form_to_string_list(List, []).
diff --git a/lib/stdlib/src/erl_internal.erl b/lib/stdlib/src/erl_internal.erl
index edfb097de0..5e6391da1f 100644
--- a/lib/stdlib/src/erl_internal.erl
+++ b/lib/stdlib/src/erl_internal.erl
@@ -1,7 +1,7 @@
 %%
 %% %CopyrightBegin%
 %%
-%% Copyright Ericsson AB 1998-2013. All Rights Reserved.
+%% Copyright Ericsson AB 1998-2014. 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
@@ -51,6 +51,8 @@
 	 type_test/2,new_type_test/2,old_type_test/2,old_bif/2]).
 -export([arith_op/2,bool_op/2,comp_op/2,list_op/2,send_op/2,op_type/2]).
 
+-export([is_type/2]).
+
 %%---------------------------------------------------------------------------
 
 %%  Erlang builtin functions allowed in guards.
@@ -530,3 +532,61 @@ old_bif(unlink, 1) -> true;
 old_bif(unregister, 1) -> true;
 old_bif(whereis, 1) -> true;
 old_bif(Name, A) when is_atom(Name), is_integer(A) -> false.
+
+-spec is_type(Name, NumberOfTypeVariables) -> boolean() when
+      Name :: atom(),
+      NumberOfTypeVariables :: non_neg_integer().
+%% Returns true if Name/NumberOfTypeVariables is a predefined type.
+
+is_type(any, 0) -> true;
+is_type(arity, 0) -> true;
+is_type(array, 0) -> true; % To be removed.
+is_type(atom, 0) -> true;
+is_type(binary, 0) -> true;
+is_type(bitstring, 0) -> true;
+is_type(bool, 0) -> true;
+is_type(boolean, 0) -> true;
+is_type(byte, 0) -> true;
+is_type(char, 0) -> true;
+is_type(dict, 0) -> true; % To be removed.
+is_type(digraph, 0) -> true; % To be removed.
+is_type(float, 0) -> true;
+is_type(function, 0) -> true;
+is_type(gb_set, 0) -> true; % To be removed.
+is_type(gb_tree, 0) -> true; % To be removed.
+is_type(identifier, 0) -> true;
+is_type(integer, 0) -> true;
+is_type(iodata, 0) -> true;
+is_type(iolist, 0) -> true;
+is_type(list, 0) -> true;
+is_type(list, 1) -> true;
+is_type(map, 0) -> true;
+is_type(maybe_improper_list, 0) -> true;
+is_type(maybe_improper_list, 2) -> true;
+is_type(mfa, 0) -> true;
+is_type(module, 0) -> true;
+is_type(neg_integer, 0) -> true;
+is_type(nil, 0) -> true;
+is_type(no_return, 0) -> true;
+is_type(node, 0) -> true;
+is_type(non_neg_integer, 0) -> true;
+is_type(none, 0) -> true;
+is_type(nonempty_improper_list, 2) -> true;
+is_type(nonempty_list, 0) -> true;
+is_type(nonempty_list, 1) -> true;
+is_type(nonempty_maybe_improper_list, 0) -> true;
+is_type(nonempty_maybe_improper_list, 2) -> true;
+is_type(nonempty_string, 0) -> true;
+is_type(number, 0) -> true;
+is_type(pid, 0) -> true;
+is_type(port, 0) -> true;
+is_type(pos_integer, 0) -> true;
+is_type(queue, 0) -> true; % To be removed.
+is_type(reference, 0) -> true;
+is_type(set, 0) -> true; % To be removed.
+is_type(string, 0) -> true;
+is_type(term, 0) -> true;
+is_type(tid, 0) -> true; % To be removed.
+is_type(timeout, 0) -> true;
+is_type(tuple, 0) -> true;
+is_type(_, _) -> false.
diff --git a/lib/stdlib/src/erl_lint.erl b/lib/stdlib/src/erl_lint.erl
index 5deddf6bd1..10ed9c27e1 100644
--- a/lib/stdlib/src/erl_lint.erl
+++ b/lib/stdlib/src/erl_lint.erl
@@ -340,14 +340,10 @@ format_error({undefined_type, {TypeName, Arity}}) ->
     io_lib:format("type ~w~s undefined", [TypeName, gen_type_paren(Arity)]);
 format_error({unused_type, {TypeName, Arity}}) ->
     io_lib:format("type ~w~s is unused", [TypeName, gen_type_paren(Arity)]);
-%% format_error({new_builtin_type, {TypeName, Arity}}) ->
-%%     io_lib:format("type ~w~s is a new builtin type; "
-%% 		  "its (re)definition is allowed only until the next release",
-%% 		  [TypeName, gen_type_paren(Arity)]);
-format_error({new_var_arity_type, TypeName}) ->
-    io_lib:format("type ~w is a new builtin type; "
+format_error({new_builtin_type, {TypeName, Arity}}) ->
+    io_lib:format("type ~w~s is a new builtin type; "
 		  "its (re)definition is allowed only until the next release",
-		  [TypeName]);
+		  [TypeName, gen_type_paren(Arity)]);
 format_error({builtin_type, {TypeName, Arity}}) ->
     io_lib:format("type ~w~s is a builtin type; it cannot be redefined",
 		  [TypeName, gen_type_paren(Arity)]);
@@ -361,10 +357,14 @@ format_error({type_syntax, Constr}) ->
     io_lib:format("bad ~w type", [Constr]);
 format_error({redefine_spec, {M, F, A}}) ->
     io_lib:format("spec for ~w:~w/~w already defined", [M, F, A]);
-format_error({redefine_callback, {M, F, A}}) ->
-    io_lib:format("callback ~w:~w/~w already defined", [M, F, A]);
-format_error({spec_fun_undefined, {M, F, A}}) ->
-    io_lib:format("spec for undefined function ~w:~w/~w", [M, F, A]);
+format_error({redefine_spec, {F, A}}) ->
+    io_lib:format("spec for ~w/~w already defined", [F, A]);
+format_error({redefine_callback, {F, A}}) ->
+    io_lib:format("callback ~w/~w already defined", [F, A]);
+format_error({bad_callback, {M, F, A}}) ->
+    io_lib:format("explicit module not allowed for callback ~w:~w/~w ", [M, F, A]);
+format_error({spec_fun_undefined, {F, A}}) ->
+    io_lib:format("spec for undefined function ~w/~w", [F, A]);
 format_error({missing_spec, {F,A}}) ->
     io_lib:format("missing specification for function ~w/~w", [F, A]);
 format_error(spec_wrong_arity) ->
@@ -1073,10 +1073,9 @@ check_undefined_types(#lint{usage=Usage,types=Def}=St0) ->
     Used = Usage#usage.used_types,
     UTAs = dict:fetch_keys(Used),
     Undef = [{TA,dict:fetch(TA, Used)} ||
-		{T,_}=TA <- UTAs,
+		TA <- UTAs,
 		not dict:is_key(TA, Def),
-		not is_default_type(TA),
-                not is_newly_introduced_var_arity_type(T)],
+		not is_default_type(TA)],
     foldl(fun ({TA,L}, St) ->
 		  add_error(L, {undefined_type,TA}, St)
 	  end, St0, Undef).
@@ -2652,30 +2651,21 @@ type_def(Attr, Line, TypeName, ProtoType, Args, St0) ->
         true ->
             case is_obsolete_builtin_type(TypePair) of
                 true -> StoreType(St0);
-                false -> add_error(Line, {builtin_type, TypePair}, St0)
-%%                     case is_newly_introduced_builtin_type(TypePair) of
-%%                         %% allow some types just for bootstrapping
-%%                         true ->
-%%                             Warn = {new_builtin_type, TypePair},
-%%                             St1 = add_warning(Line, Warn, St0),
-%%                             StoreType(St1);
-%%                         false ->
-%%                             add_error(Line, {builtin_type, TypePair}, St0)
-%%                     end
+                false ->
+                     case is_newly_introduced_builtin_type(TypePair) of
+                         %% allow some types just for bootstrapping
+                         true ->
+                             Warn = {new_builtin_type, TypePair},
+                             St1 = add_warning(Line, Warn, St0),
+                             StoreType(St1);
+                         false ->
+                             add_error(Line, {builtin_type, TypePair}, St0)
+                     end
             end;
         false ->
-            case
-                dict:is_key(TypePair, TypeDefs) orelse
-                is_var_arity_type(TypeName)
-            of
+            case dict:is_key(TypePair, TypeDefs) of
                 true ->
-                    case is_newly_introduced_var_arity_type(TypeName) of
-                        true ->
-                            Warn = {new_var_arity_type, TypeName},
-                            add_warning(Line, Warn, St0);
-                        false ->
-                            add_error(Line, {redefine_type, TypePair}, St0)
-                    end;
+                    add_error(Line, {redefine_type, TypePair}, St0);
                 false ->
                     St1 = case
                               Attr =:= opaque andalso
@@ -2712,7 +2702,7 @@ check_type({paren_type, _L, [Type]}, SeenVars, St) ->
 check_type({remote_type, L, [{atom, _, Mod}, {atom, _, Name}, Args]},
 	   SeenVars, #lint{module=CurrentMod} = St) ->
     case Mod =:= CurrentMod of
-	true -> check_type({type, L, Name, Args}, SeenVars, St);
+	true -> check_type({user_type, L, Name, Args}, SeenVars, St);
 	false ->
 	    lists:foldl(fun(T, {AccSeenVars, AccSt}) ->
 				check_type(T, AccSeenVars, AccSt)
@@ -2746,12 +2736,15 @@ 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, any}, SeenVars, St) ->
+    %% To get usage right while map/0 is a newly_introduced_builtin_type.
+    St1 = used_type({map, 0}, L, St),
+    {SeenVars, St1};
 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, _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};
@@ -2770,41 +2763,39 @@ check_type({type, L, record, [Name|Fields]}, SeenVars, St) ->
 	    check_record_types(L, Atom, Fields, SeenVars, St1);
 	_ -> {SeenVars, add_error(L, {type_syntax, record}, St)}
     end;
-check_type({type, _L, product, Args}, SeenVars, St) ->
+check_type({type, _L, Tag, Args}, SeenVars, St) when Tag =:= product;
+                                                     Tag =:= union;
+                                                     Tag =:= tuple ->
     lists:foldl(fun(T, {AccSeenVars, AccSt}) ->
 			check_type(T, AccSeenVars, AccSt)
 		end, {SeenVars, St}, Args);
 check_type({type, La, TypeName, Args}, SeenVars, St) ->
-    #lint{usage=Usage, module = Module, types=Types} = St,
+    #lint{module = Module, types=Types} = St,
     Arity = length(Args),
     TypePair = {TypeName, Arity},
-    St1 = case is_var_arity_type(TypeName) of
-	      true -> St;
-	      false ->
-                  Obsolete = (is_warn_enabled(deprecated_type, St)
-                              andalso obsolete_builtin_type(TypePair)),
-                  IsObsolete =
-                      case Obsolete of
-                          {deprecated, Repl, _} when element(1, Repl) =/= Module ->
-                              case dict:find(TypePair, Types) of
-                                  {ok, _} -> false;
-                                  error -> true
-                              end;
-                          _ -> false
-                      end,
-                  case IsObsolete of
-                      true ->
+    Obsolete = (is_warn_enabled(deprecated_type, St)
+                andalso obsolete_builtin_type(TypePair)),
+    St1 = case Obsolete of
+              {deprecated, Repl, _} when element(1, Repl) =/= Module ->
+                  case dict:find(TypePair, Types) of
+                      {ok, _} ->
+                          used_type(TypePair, La, St);
+                      error ->
                           {deprecated, Replacement, Rel} = Obsolete,
                           Tag = deprecated_builtin_type,
                           W = {Tag, TypePair, Replacement, Rel},
-                          add_warning(La, W, St);
-                      false ->
-                          OldUsed = Usage#usage.used_types,
-                          UsedTypes = dict:store(TypePair, La, OldUsed),
-                          St#lint{usage=Usage#usage{used_types=UsedTypes}}
-                  end
-	  end,
+                          add_warning(La, W, St)
+                end;
+            _ -> St
+        end,
     check_type({type, -1, product, Args}, SeenVars, St1);
+check_type({user_type, L, TypeName, Args}, SeenVars, St) ->
+    Arity = length(Args),
+    TypePair = {TypeName, Arity},
+    St1 = used_type(TypePair, L, St),
+    lists:foldl(fun(T, {AccSeenVars, AccSt}) ->
+			check_type(T, AccSeenVars, AccSt)
+		end, {SeenVars, St1}, Args);
 check_type(I, SeenVars, St) ->
     case erl_eval:partial_eval(I) of
         {integer,_ILn,_Integer} -> {SeenVars, St};
@@ -2846,74 +2837,17 @@ check_record_types([{type, _, field_type, [{atom, AL, FName}, Type]}|Left],
 check_record_types([], _Name, _DefFields, SeenVars, St, _SeenFields) ->
     {SeenVars, St}.
 
-is_var_arity_type(tuple) -> true;
-is_var_arity_type(map) -> true;
-is_var_arity_type(product) -> true;
-is_var_arity_type(union) -> true;
-is_var_arity_type(record) -> true;
-is_var_arity_type(_) -> false.
-
-is_default_type({any, 0}) -> true;
-is_default_type({arity, 0}) -> true;
-is_default_type({array, 0}) -> true;
-is_default_type({atom, 0}) -> true;
-is_default_type({atom, 1}) -> true;
-is_default_type({binary, 0}) -> true;
-is_default_type({binary, 2}) -> true;
-is_default_type({bitstring, 0}) -> true;
-is_default_type({bool, 0}) -> true;
-is_default_type({boolean, 0}) -> true;
-is_default_type({byte, 0}) -> true;
-is_default_type({char, 0}) -> true;
-is_default_type({dict, 0}) -> true;
-is_default_type({digraph, 0}) -> true;
-is_default_type({float, 0}) -> true;
-is_default_type({'fun', 0}) -> true;
-is_default_type({'fun', 2}) -> true;
-is_default_type({function, 0}) -> true;
-is_default_type({gb_set, 0}) -> true;
-is_default_type({gb_tree, 0}) -> true;
-is_default_type({identifier, 0}) -> true;
-is_default_type({integer, 0}) -> true;
-is_default_type({integer, 1}) -> true;
-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({maybe_improper_list, 0}) -> true;
-is_default_type({maybe_improper_list, 2}) -> true;
-is_default_type({mfa, 0}) -> true;
-is_default_type({module, 0}) -> true;
-is_default_type({neg_integer, 0}) -> true;
-is_default_type({nil, 0}) -> true;
-is_default_type({no_return, 0}) -> true;
-is_default_type({node, 0}) -> true;
-is_default_type({non_neg_integer, 0}) -> true;
-is_default_type({none, 0}) -> true;
-is_default_type({nonempty_list, 0}) -> true;
-is_default_type({nonempty_list, 1}) -> true;
-is_default_type({nonempty_improper_list, 2}) -> true;
-is_default_type({nonempty_maybe_improper_list, 0}) -> true;
-is_default_type({nonempty_maybe_improper_list, 2}) -> true;
-is_default_type({nonempty_string, 0}) -> true;
-is_default_type({number, 0}) -> true;
-is_default_type({pid, 0}) -> true;
-is_default_type({port, 0}) -> true;
-is_default_type({pos_integer, 0}) -> true;
-is_default_type({queue, 0}) -> true;
-is_default_type({range, 2}) -> true;
-is_default_type({reference, 0}) -> true;
-is_default_type({set, 0}) -> true;
-is_default_type({string, 0}) -> true;
-is_default_type({term, 0}) -> true;
-is_default_type({timeout, 0}) -> true;
-is_default_type({var, 1}) -> true;
-is_default_type(_) -> false.
-
-is_newly_introduced_var_arity_type(map) -> true;
-is_newly_introduced_var_arity_type(_) -> false.
-
-%% is_newly_introduced_builtin_type({Name, _}) when is_atom(Name) -> false.
+used_type(TypePair, L, St) ->
+    Usage = St#lint.usage,
+    OldUsed = Usage#usage.used_types,
+    UsedTypes = dict:store(TypePair, L, OldUsed),
+    St#lint{usage=Usage#usage{used_types=UsedTypes}}.
+
+is_default_type({Name, NumberOfTypeVariables}) ->
+    erl_internal:is_type(Name, NumberOfTypeVariables).
+
+is_newly_introduced_builtin_type({map, 0}) -> true;
+is_newly_introduced_builtin_type({Name, _}) when is_atom(Name) -> false.
 
 is_obsolete_builtin_type(TypePair) ->
     obsolete_builtin_type(TypePair) =/= no.
@@ -2946,7 +2880,7 @@ spec_decl(Line, MFA0, TypeSpecs, St0 = #lint{specs = Specs, module = Mod}) ->
 	  end,
     St1 = St0#lint{specs = dict:store(MFA, Line, Specs)},
     case dict:is_key(MFA, Specs) of
-	true -> add_error(Line, {redefine_spec, MFA}, St1);
+	true -> add_error(Line, {redefine_spec, MFA0}, St1);
 	false -> check_specs(TypeSpecs, Arity, St1)
     end.
 
@@ -2954,14 +2888,15 @@ spec_decl(Line, MFA0, TypeSpecs, St0 = #lint{specs = Specs, module = Mod}) ->
 
 callback_decl(Line, MFA0, TypeSpecs,
 	      St0 = #lint{callbacks = Callbacks, module = Mod}) ->
-    MFA = case MFA0 of
-	      {F, Arity} -> {Mod, F, Arity};
-	      {_M, _F, Arity} -> MFA0
-	  end,
-    St1 = St0#lint{callbacks = dict:store(MFA, Line, Callbacks)},
-    case dict:is_key(MFA, Callbacks) of
-	true -> add_error(Line, {redefine_callback, MFA}, St1);
-	false -> check_specs(TypeSpecs, Arity, St1)
+    case MFA0 of
+        {_M, _F, _A} -> add_error(Line, {bad_callback, MFA0}, St0);
+        {F, Arity} ->
+            MFA = {Mod, F, Arity},
+            St1 = St0#lint{callbacks = dict:store(MFA, Line, Callbacks)},
+            case dict:is_key(MFA, Callbacks) of
+                true -> add_error(Line, {redefine_callback, MFA0}, St1);
+                false -> check_specs(TypeSpecs, Arity, St1)
+            end
     end.
 
 %% optional_callbacks(Line, FAs, State) -> State.
@@ -3020,10 +2955,11 @@ check_specs([], _Arity, St) ->
     St.
 
 check_specs_without_function(#lint{module=Mod,defined=Funcs,specs=Specs}=St) ->
-    Fun = fun({M, F, A} = MFA, Line, AccSt) when M =:= Mod ->
-		  case gb_sets:is_element({F, A}, Funcs) of
+    Fun = fun({M, F, A}, Line, AccSt) when M =:= Mod ->
+                  FA = {F, A},
+		  case gb_sets:is_element(FA, Funcs) of
 		      true -> AccSt;
-		      false -> add_error(Line, {spec_fun_undefined, MFA}, AccSt)
+		      false -> add_error(Line, {spec_fun_undefined, FA}, AccSt)
 		  end;
 	     ({_M, _F, _A}, _Line, AccSt) -> AccSt
 	  end,
diff --git a/lib/stdlib/src/erl_parse.yrl b/lib/stdlib/src/erl_parse.yrl
index 1dc5fc52a7..828870d492 100644
--- a/lib/stdlib/src/erl_parse.yrl
+++ b/lib/stdlib/src/erl_parse.yrl
@@ -146,8 +146,7 @@ type -> '(' top_type ')'                  : {paren_type, ?line('$2'), ['$2']}.
 type -> var                               : '$1'.
 type -> atom                              : '$1'.
 type -> atom '(' ')'                      : build_gen_type('$1').
-type -> atom '(' top_types ')'            : {type, ?line('$1'),
-                                             normalise('$1'), '$3'}.
+type -> atom '(' top_types ')'            : build_type('$1', '$3').
 type -> atom ':' atom '(' ')'             : {remote_type, ?line('$1'),
                                              ['$1', '$3', []]}.
 type -> atom ':' atom '(' top_types ')'   : {remote_type, ?line('$1'),
@@ -181,7 +180,7 @@ fun_type -> '(' top_types ')' '->' top_type
 
 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'}.
+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'].
@@ -665,6 +664,8 @@ find_arity_from_specs([Spec|_]) ->
     {type, _, 'fun', [{type, _, product, Args},_]} = Fun,
     length(Args).
 
+build_def({var, L, '_'}, _Types) ->
+    ret_err(L, "bad type variable");
 build_def(LHS, Types) ->
     IsSubType = {atom, ?line(LHS), is_subtype},
     {type, ?line(LHS), constraint, [IsSubType, [LHS, Types]]}.
@@ -684,7 +685,8 @@ build_gen_type({atom, La, tuple}) ->
 build_gen_type({atom, La, map}) ->
     {type, La, map, any};
 build_gen_type({atom, La, Name}) ->
-    {type, La, Name, []}.
+    Tag = type_tag(Name, 0),
+    {Tag, La, Name, []}.
 
 build_bin_type([{var, _, '_'}|Left], Int) ->
     build_bin_type(Left, Int);
@@ -693,6 +695,16 @@ build_bin_type([], Int) ->
 build_bin_type([{var, La, _}|_], _) ->
     ret_err(La, "Bad binary type").
 
+build_type({atom, L, Name}, Types) ->
+    Tag = type_tag(Name, length(Types)),
+    {Tag, L, Name, Types}.
+
+type_tag(TypeName, NumberOfTypeVariables) ->
+    case erl_internal:is_type(TypeName, NumberOfTypeVariables) of
+        true -> type;
+        false -> user_type
+    end.
+
 %% build_attribute(AttrName, AttrValue) ->
 %%	{attribute,Line,module,Module}
 %%	{attribute,Line,export,Exports}
diff --git a/lib/stdlib/src/erl_pp.erl b/lib/stdlib/src/erl_pp.erl
index 788dbb40b6..10842d21ab 100644
--- a/lib/stdlib/src/erl_pp.erl
+++ b/lib/stdlib/src/erl_pp.erl
@@ -285,6 +285,9 @@ ltype({type,_,'fun',[{type,_,any},_]}=FunType) ->
 ltype({type,_Line,'fun',[{type,_,product,_},_]}=FunType) ->
     [fun_type(['fun',$(], FunType),$)];
 ltype({type,Line,T,Ts}) ->
+    %% Compatibility. Before 18.0.
+    simple_type({atom,Line,T}, Ts);
+ltype({user_type,Line,T,Ts}) ->
     simple_type({atom,Line,T}, Ts);
 ltype({remote_type,Line,[M,F,Ts]}) ->
     simple_type({remote,Line,M,F}, Ts);
@@ -307,7 +310,7 @@ map_type(Fs) ->
 map_pair_types(Fs) ->
     tuple_type(Fs, fun map_pair_type/1).
 
-map_pair_type({type,_Line,map_field_assoc,Ktype,Vtype}) ->
+map_pair_type({type,_Line,map_field_assoc,[Ktype,Vtype]}) ->
     {seq,[],[]," =>",[ltype(Ktype),ltype(Vtype)]}.
 
 record_type(Name, Fields) ->
diff --git a/lib/stdlib/test/erl_lint_SUITE.erl b/lib/stdlib/test/erl_lint_SUITE.erl
index 5506d3d166..5db0631f58 100644
--- a/lib/stdlib/test/erl_lint_SUITE.erl
+++ b/lib/stdlib/test/erl_lint_SUITE.erl
@@ -63,7 +63,7 @@
 	  too_many_arguments/1,
 	  basic_errors/1,bin_syntax_errors/1,
           predef/1,
-          maps/1,maps_type/1
+          maps/1,maps_type/1,otp_11851/1
         ]).
 
 % Default timetrap timeout (set in init_per_testcase).
@@ -92,7 +92,7 @@ all() ->
      bif_clash, behaviour_basic, behaviour_multiple, otp_11861,
      otp_7550, otp_8051, format_warn, {group, on_load},
      too_many_arguments, basic_errors, bin_syntax_errors, predef,
-     maps, maps_type].
+     maps, maps_type, otp_11851].
 
 groups() -> 
     [{unused_vars_warn, [],
@@ -2649,7 +2649,9 @@ otp_11872(Config) when is_list(Config) ->
                 1.
          ">>,
     {error,[{6,erl_lint,{undefined_type,{product,0}}}],
-     [{8,erl_lint,{new_var_arity_type,map}}]} =
+     [{8,erl_lint,{new_builtin_type,{map,0}}},
+      {8,erl_lint,
+       {deprecated_builtin_type,{dict,0},{dict,dict,2}, "OTP 18.0"}}]} =
         run_test2(Config, Ts, []),
     ok.
 
@@ -3246,7 +3248,7 @@ otp_11861(Conf) when is_list(Conf) ->
               -callback b(_) -> atom().
              ">>,
            [],
-           {errors,[{3,erl_lint,{redefine_callback,{lint_test,b,1}}}],[]}},
+           {errors,[{3,erl_lint,{redefine_callback,{b,1}}}],[]}},
           {otp_11861_17,
            <<"
               -behaviour(bad_behaviour2).
@@ -3657,7 +3659,94 @@ maps_type(Config) when is_list(Config) ->
 	    t(M) -> M.
 	 ">>,
 	 [],
-	 {warnings,[{3,erl_lint,{new_var_arity_type,map}}]}}],
+	 {warnings,[{3,erl_lint,{new_builtin_type,{map,0}}}]}}],
+    [] = run(Config, Ts),
+    ok.
+
+otp_11851(doc) ->
+    "OTP-11851: More atoms can be used as type names + bug fixes.";
+otp_11851(Config) when is_list(Config) ->
+    Ts = [
+	{otp_11851_1,
+	 <<"-export([t/0]).
+            -type range(A, B) :: A | B.
+
+            -type union(A) :: A.
+
+            -type product() :: integer().
+
+            -type tuple(A) :: A.
+
+            -type map(A) :: A.
+
+            -type record() :: a | b.
+
+            -type integer(A) :: A.
+
+            -type atom(A) :: A.
+
+            -type binary(A, B) :: A | B.
+
+            -type 'fun'() :: integer().
+
+            -type 'fun'(X) :: X.
+
+            -type 'fun'(X, Y) :: X | Y.
+
+            -type all() :: range(atom(), integer()) | union(pid()) | product()
+                         | tuple(reference()) | map(function()) | record()
+                         | integer(atom()) | atom(integer())
+                         | binary(pid(), tuple()) | 'fun'(port())
+                         | 'fun'() | 'fun'(<<>>, 'none').
+
+            -spec t() -> all().
+
+            t() ->
+                a.
+	">>,
+	[],
+	[]},
+	{otp_11851_2,
+	 <<"-export([a/1, b/1, t/0]).
+
+            -callback b(_) -> integer().
+
+            -callback ?MODULE:a(_) -> integer().
+
+            a(_) -> 3.
+
+            b(_) -> a.
+
+            t()-> a.
+	">>,
+	[],
+	{errors,[{5,erl_lint,{bad_callback,{lint_test,a,1}}}],[]}},
+	{otp_11851_3,
+	 <<"-export([a/1]).
+
+            -spec a(_A) -> boolean() when
+                  _ :: atom(),
+                  _A :: integer().
+
+            a(_) -> true.
+	">>,
+	[],
+	{errors,[{4,erl_parse,"bad type variable"}],[]}},
+	{otp_11851_4,
+	 <<"
+            -spec a(_) -> ok.
+            -spec a(_) -> ok.
+
+            -spec ?MODULE:a(_) -> ok.
+            -spec ?MODULE:a(_) -> ok.
+	">>,
+	[],
+         {errors,[{3,erl_lint,{redefine_spec,{a,1}}},
+                  {5,erl_lint,{redefine_spec,{lint_test,a,1}}},
+                  {6,erl_lint,{redefine_spec,{lint_test,a,1}}},
+                  {6,erl_lint,{spec_fun_undefined,{a,1}}}],
+          []}}
+          ],
     [] = run(Config, Ts),
     ok.
 
diff --git a/lib/stdlib/test/erl_pp_SUITE.erl b/lib/stdlib/test/erl_pp_SUITE.erl
index d0892c6d79..12817943d0 100644
--- a/lib/stdlib/test/erl_pp_SUITE.erl
+++ b/lib/stdlib/test/erl_pp_SUITE.erl
@@ -874,6 +874,7 @@ type_examples() ->
      {ex3,<<"-type paren() :: (ann2()). ">>},
      {ex4,<<"-type t1() :: atom(). ">>},
      {ex5,<<"-type t2() :: [t1()]. ">>},
+     {ex56,<<"-type integer(A) :: A. ">>},
      {ex6,<<"-type t3(Atom) :: integer(Atom). ">>},
      {ex7,<<"-type '\\'t::4'() :: t3('\\'foobar'). ">>},
      {ex8,<<"-type t5() :: {t1(), t3(foo)}. ">>},