Merge branch 'hb/stdlib/opaque_warnings/OTP-10436'

* hb/stdlib/opaque_warnings/OTP-10436:
  Refine a few opaque types
  Warn for underspecified opaque types
  Warn for opaque types that are not exported

1 files changed, 52 insertions, 9 deletions

diff --git a/lib/stdlib/src/erl_lint.erl b/lib/stdlib/src/erl_lint.erl
index 97dacac0a4..1e5f962375 100644
--- a/lib/stdlib/src/erl_lint.erl
+++ b/lib/stdlib/src/erl_lint.erl
@@ -365,6 +365,12 @@ format_error(callback_wrong_arity) ->
 format_error({imported_predefined_type, Name}) ->
     io_lib:format("referring to built-in type ~w as a remote type; "
 		  "please take out the module name", [Name]);
+format_error({not_exported_opaque, {TypeName, Arity}}) ->
+    io_lib:format("opaque type ~w~s is not exported",
+                  [TypeName, gen_type_paren(Arity)]);
+format_error({underspecified_opaque, {TypeName, Arity}}) ->
+    io_lib:format("opaque type ~w~s is underspecified and therefore meaningless",
+                  [TypeName, gen_type_paren(Arity)]);
 %% --- obsolete? unused? ---
 format_error({format_error, {Fmt, Args}}) ->
     io_lib:format(Fmt, Args);
@@ -851,7 +857,8 @@ post_traversal_check(Forms, St0) ->
     StC = check_untyped_records(Forms, StB),
     StD = check_on_load(StC),
     StE = check_unused_records(Forms, StD),
-    check_callback_information(StE).
+    StF = check_local_opaque_types(StE),
+    check_callback_information(StF).
 
 %% check_behaviour(State0) -> State
 %% Check that the behaviour attribute is valid.
@@ -2554,15 +2561,24 @@ find_field(_F, []) -> error.
 %%    Attr :: 'type' | 'opaque'
 %% Checks that a type definition is valid.
 
+-record(typeinfo, {attr, line}).
+
 type_def(_Attr, _Line, {record, _RecName}, Fields, [], St0) ->
     %% The record field names and such are checked in the record format.
     %% We only need to check the types.
     Types = [T || {typed_record_field, _, T} <- Fields],
     check_type({type, -1, product, Types}, St0);
-type_def(_Attr, Line, TypeName, ProtoType, Args, St0) ->
+type_def(Attr, Line, TypeName, ProtoType, Args, St0) ->
     TypeDefs = St0#lint.types,
     Arity = length(Args),
     TypePair = {TypeName, Arity},
+    Info = #typeinfo{attr = Attr, line = Line},
+    StoreType =
+        fun(St) ->
+                NewDefs = dict:store(TypePair, Info, TypeDefs),
+                CheckType = {type, -1, product, [ProtoType|Args]},
+                check_type(CheckType, St#lint{types=NewDefs})
+        end,
     case (dict:is_key(TypePair, TypeDefs) orelse is_var_arity_type(TypeName)) of
 	true ->
 	    case dict:is_key(TypePair, default_types()) of
@@ -2572,20 +2588,29 @@ type_def(_Attr, Line, TypeName, ProtoType, Args, St0) ->
 			true ->
 			    Warn = {new_builtin_type, TypePair},
 			    St1 = add_warning(Line, Warn, St0),
-			    NewDefs = dict:store(TypePair, Line, TypeDefs),
-			    CheckType = {type, -1, product, [ProtoType|Args]},
-			    check_type(CheckType, St1#lint{types=NewDefs});
+                            StoreType(St1);
 			false ->
 			    add_error(Line, {builtin_type, TypePair}, St0)
 		    end;
 	        false -> add_error(Line, {redefine_type, TypePair}, St0)
 	    end;
 	false ->
-	    NewDefs = dict:store(TypePair, Line, TypeDefs),
-	    CheckType = {type, -1, product, [ProtoType|Args]},
-	    check_type(CheckType, St0#lint{types=NewDefs})
+            St1 = case
+                      Attr =:= opaque andalso
+                      is_underspecified(ProtoType, Arity)
+                  of
+                      true ->
+                          Warn = {underspecified_opaque, TypePair},
+                          add_warning(Line, Warn, St0);
+                      false -> St0
+                  end,
+            StoreType(St1)
     end.
 
+is_underspecified({type,_,term,[]}, 0) -> true;
+is_underspecified({type,_,any,[]}, 0) -> true;
+is_underspecified(_ProtType, _Arity) -> false.
+
 check_type(Types, St) ->
     {SeenVars, St1} = check_type(Types, dict:new(), St),
     dict:fold(fun(Var, {seen_once, Line}, AccSt) ->
@@ -2895,7 +2920,7 @@ check_unused_types(Forms, #lint{usage=Usage, types=Ts, exp_types=ExpTs}=St) ->
 		fun(_Type, -1, AccSt) ->
 			%% Default type
 			AccSt;
-		   (Type, FileLine, AccSt) ->
+		   (Type, #typeinfo{line = FileLine}, AccSt) ->
                         case loc(FileLine) of
 			    {FirstFile, _} ->
 				case gb_sets:is_member(Type, UsedTypes) of
@@ -2914,6 +2939,24 @@ check_unused_types(Forms, #lint{usage=Usage, types=Ts, exp_types=ExpTs}=St) ->
 	    St
     end.
 
+check_local_opaque_types(St) ->
+    #lint{types=Ts, exp_types=ExpTs} = St,
+    FoldFun =
+        fun(_Type, -1, AccSt) ->
+                %% Default type
+                AccSt;
+           (_Type, #typeinfo{attr = type}, AccSt) ->
+                AccSt;
+           (Type, #typeinfo{attr = opaque, line = FileLine}, AccSt) ->
+                case gb_sets:is_element(Type, ExpTs) of
+                    true -> AccSt;
+                    false ->
+                        Warn = {not_exported_opaque,Type},
+                        add_warning(FileLine, Warn, AccSt)
+                end
+        end,
+    dict:fold(FoldFun, St, Ts).
+
 %% icrt_clauses(Clauses, In, ImportVarTable, State) ->
 %%      {NewVts,State}.