File 4365-erl_types-Ignore-opaque-type-arguments.patch of Package erlang

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File 4365-erl_types-Ignore-opaque-type-arguments.patch of Package erlang (Revision a7029ee97b719a45764ae3b135bbdda2)

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From facb47b03d4389c966ebc0857cfd45306aa210d5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?John=20H=C3=B6gberg?= <john@erlang.org>
Date: Mon, 20 Sep 2021 11:17:48 +0200
Subject: [PATCH 5/7] erl_types: Ignore opaque type arguments

TL;DR: Opaque types are rather convoluted, this commit removes one
of the hairiest parts.

----

It is not commonly known that opaque types are invariant on their
type parameters: an opaque type `foo:bar(gurka | gaffel)` _IS NOT_
a subtype of `foo:bar(atom())`, nor is it a supertype of
`foo:bar(gurka)`. For an opaque type to be compatible with
another instance of the same type, their type parameters have to be
exactly equal.

This may seem a bit strict but is required for correctness:
while it's trivial to see that one can pass an `[integer()]` to a
function expecting `[number()]` since the list type is covariant on
the element type, we don't have a way to express whether an opaque
type parameter is covariant, contravariant, or invariant. Nor can
we infer it beyond toy cases.

The easiest way to keep the type system sound in the face of that
is to treat all type parameters as invariant. It's perhaps a bit
surprising but there's nothing wrong with it. So far so good.

Then we hit this marvel in `gb_sets`:

```erlang
-spec add(Element, Set1) -> Set2 when
      Set1 :: set(Element),
      Set2 :: set(Element).
```

A strict reading of this says that it accepts a set containing a
singleton `Element`, and produces a set containing `Element`
alone. If we were to pass a set produced by this function to one
that expects `gb_sets:set(atom())`, we would get a type error
unless `Element` had already collapsed to `atom()`. (Other funny
consequences are left as an exercise to the reader)

Yet that works at the moment. Huh?!

1. dialyzer just throws away type variables in specs, replacing
   them with `term()` and removing all relations between them.

Trying to fix that is how I noticed this wonderful quirk.
2. dialyzer considers `any()` in type variables to be quasi-equal
   to all other types. That is, `gb_sets:set(any())` is okay in
   functions that expect (say) `gb_sets:set(atom())` and vice
   versa.

The former is awkward but the latter is where things go off the
rails. We may pass `any()`d and more strictly typed opaques around
interchangeably, but since type parameters are invariant there's no
 way for us to tell which is the subtype and which is the
supertype! This effectively breaks the type lattice and sends
dialyzer into infinite loops often enough that adding a test case
to this commit is rather pointless: you can hardly even begin
building a PLT of OTP before hitting it.

Since we can't do anything about this without inventing a new
notation and requiring people to rewrite their specs with it, I've
decided to ignore type parameters altogether in this commit. It
makes dialyzer less useful, but I believe it's worth it to ensure
that the results are correct.
---
 lib/dialyzer/src/erl_types.erl                | 166 +++---------------
 .../test/map_SUITE_data/results/opaque_key    |   4 +-
 .../test/opaque_SUITE_data/results/para       |  32 ++--
 3 files changed, 39 insertions(+), 163 deletions(-)

diff --git a/lib/hipe/cerl/erl_types.erl b/lib/hipe/cerl/erl_types.erl
index 37b7793d56..b9af689ea7 100644
--- a/lib/hipe/cerl/erl_types.erl
+++ b/lib/hipe/cerl/erl_types.erl
@@ -319,11 +319,9 @@
 
 -record(int_set, {set :: [integer()]}).
 -record(int_rng, {from :: rng_elem(), to :: rng_elem()}).
-%% Note: the definition of #opaque{} was changed to 'mod' and 'name';
-%% it used to be an ordsets of {Mod, Name} pairs. The Dialyzer version
-%% was updated to 2.7 due to this change.
+
 -record(opaque,  {mod :: module(), name :: atom(),
-		  args = [] :: [erl_type()], struct :: erl_type()}).
+                  arity = 0 :: arity(), struct :: erl_type()}).
 
 -define(atom(Set),                 #c{tag=?atom_tag, elements=Set}).
 -define(bitstr(Unit, Base),        #c{tag=?binary_tag, elements=[Unit,Base]}).
@@ -435,7 +433,7 @@ t_is_none(_) -> false.
 -spec t_opaque(module(), atom(), [_], erl_type()) -> erl_type().
 
 t_opaque(Mod, Name, Args, Struct) ->
-  O = #opaque{mod = Mod, name = Name, args = Args, struct = Struct},
+  O = #opaque{mod = Mod, name = Name, arity = length(Args), struct = Struct},
   ?opaque(set_singleton(O)).
 
 -spec t_is_opaque(erl_type(), [erl_type()]) -> boolean().
@@ -2327,7 +2325,6 @@ 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)]);
 t_has_var(?union(List)) ->
   t_has_var_list(List);
@@ -2367,7 +2364,6 @@ t_collect_var_names(?map(_, DefK, _) = Map, Acc0) ->
   Acc = t_collect_vars_list(map_all_values(Map), Acc0),
   t_collect_var_names(DefK, Acc);
 t_collect_var_names(?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);
 t_collect_var_names(?union(List), Acc) ->
   t_collect_vars_list(List, Acc);
@@ -2714,8 +2710,8 @@ sup_opaque(List) ->
   ?opaque(ordsets:from_list(L)).
 
 sup_opaq(L0) ->
-  L1 = [{{Mod,Name,Args}, T} ||
-         #opaque{mod = Mod, name = Name, args = Args}=T <- L0],
+  L1 = [{{Mod,Name,Arity}, T} ||
+         #opaque{mod = Mod, name = Name, arity = Arity}=T <- L0],
   F = family(L1),
   [supl(Ts) || {_, Ts} <- F].
 
@@ -3163,121 +3159,13 @@ compatible_opaque_types(?opaque(Es1), ?opaque(Es2)) ->
   [{O1, O2} || O1 <- Es1, O2 <- Es2, is_compat_opaque_names(O1, O2)].
 
 is_compat_opaque_names(Opaque1, Opaque2) ->
-  #opaque{mod = Mod1, name = Name1, args = Args1} = Opaque1,
-  #opaque{mod = Mod2, name = Name2, args = Args2} = Opaque2,
-  case {{Mod1, Name1, Args1}, {Mod2, Name2, Args2}} of
-    {ModNameArgs, ModNameArgs} -> true;
-    {{Mod, Name, Args1}, {Mod, Name, Args2}} ->
-      is_compat_args(Args1, Args2);
+  #opaque{mod = Mod1, name = Name1, arity = Arity1} = Opaque1,
+  #opaque{mod = Mod2, name = Name2, arity = Arity2} = Opaque2,
+  case {{Mod1, Name1, Arity1}, {Mod2, Name2, Arity2}} of
+    {ModNameArity, ModNameArity} -> true;
     _ -> false
   end.
 
-is_compat_args([A1|Args1], [A2|Args2]) ->
-  is_compat_arg(A1, A2) andalso is_compat_args(Args1, Args2);
-is_compat_args([], []) -> true;
-is_compat_args(_, _) -> false.
-
--spec is_compat_arg(erl_type(), erl_type()) -> boolean().
-
-%% The intention is that 'true' is to be returned iff one of the
-%% arguments is a specialization of the other argument in the sense
-%% that every type is a specialization of any(). For example, {_,_} is
-%% a specialization of any(), but not of tuple(). Does not handle
-%% variables, but any() and unions (sort of). However, the
-%% implementation is more relaxed as any() is compatible to anything.
-
-is_compat_arg(T, T) -> true;
-is_compat_arg(_, ?any) -> true;
-is_compat_arg(?any, _) -> true;
-is_compat_arg(?function(Domain1, Range1), ?function(Domain2, Range2)) ->
-  (is_compat_arg(Domain1, Domain2) andalso
-   is_compat_arg(Range1, Range2));
-is_compat_arg(?list(Contents1, Termination1, Size1),
-              ?list(Contents2, Termination2, Size2)) ->
-  (Size1 =:= Size2 andalso
-   is_compat_arg(Contents1, Contents2) andalso
-   is_compat_arg(Termination1, Termination2));
-is_compat_arg(?product(Types1), ?product(Types2)) ->
-  is_compat_list(Types1, Types2);
-is_compat_arg(?map(Pairs1, DefK1, DefV1), ?map(Pairs2, DefK2, DefV2)) ->
-  {Ks1, _, Vs1} = lists:unzip3(Pairs1),
-  {Ks2, _, Vs2} = lists:unzip3(Pairs2),
-  Key1 = t_sup([DefK1 | Ks1]),
-  Key2 = t_sup([DefK2 | Ks2]),
-  case is_compat_arg(Key1, Key2) of
-    true ->
-      Value1 = t_sup([DefV1 | Vs1]),
-      Value2 = t_sup([DefV2 | Vs2]),
-      is_compat_arg(Value1, Value2);
-    false ->
-      false
-  end;
-is_compat_arg(?tuple(?any, ?any, ?any), ?tuple(_, _, _)) -> false;
-is_compat_arg(?tuple(_, _, _), ?tuple(?any, ?any, ?any)) -> false;
-is_compat_arg(?tuple(Elements1, Arity, _),
-              ?tuple(Elements2, Arity, _)) when Arity =/= ?any ->
-  is_compat_list(Elements1, Elements2);
-is_compat_arg(?tuple_set([{Arity, List}]),
-              ?tuple(Elements2, Arity, _)) when Arity =/= ?any ->
-  is_compat_list(sup_tuple_elements(List), Elements2);
-is_compat_arg(?tuple(Elements1, Arity, _),
-              ?tuple_set([{Arity, List}])) when Arity =/= ?any ->
-  is_compat_list(Elements1, sup_tuple_elements(List));
-is_compat_arg(?tuple_set(List1), ?tuple_set(List2)) ->
-  try
-    is_compat_list_list([sup_tuple_elements(T) || {_Arity, T} <- List1],
-                        [sup_tuple_elements(T) || {_Arity, T} <- List2])
-  catch _:_ -> false
-  end;
-is_compat_arg(?opaque(_) = T1, T2) ->
-  is_compat_arg(t_opaque_structure(T1), T2);
-is_compat_arg(T1, ?opaque(_) = T2) ->
-  is_compat_arg(T1, t_opaque_structure(T2));
-is_compat_arg(?union(List1)=T1, ?union(List2)=T2) ->
-  case is_compat_union2(T1, T2) of
-    {yes, Type1, Type2} -> is_compat_arg(Type1, Type2);
-    no -> is_compat_list(List1, List2)
-  end;
-is_compat_arg(?union(List), T2) ->
-  case unify_union(List) of
-      {yes, Type} -> is_compat_arg(Type, T2);
-      no -> false
-  end;
-is_compat_arg(T1, ?union(List)) ->
-  case unify_union(List) of
-      {yes, Type} -> is_compat_arg(T1, Type);
-      no -> false
-  end;
-is_compat_arg(?var(_), _) -> exit(error);
-is_compat_arg(_, ?var(_)) -> exit(error);
-is_compat_arg(?none, _) -> false;
-is_compat_arg(_, ?none) -> false;
-is_compat_arg(?unit, _) -> false;
-is_compat_arg(_, ?unit) -> false;
-is_compat_arg(#c{}, #c{}) -> false.
-
-is_compat_list_list(LL1, LL2) ->
-  length(LL1) =:= length(LL2) andalso is_compat_list_list1(LL1, LL2).
-
-is_compat_list_list1([], []) -> true;
-is_compat_list_list1([L1|LL1], [L2|LL2]) ->
-  is_compat_list(L1, L2) andalso is_compat_list_list1(LL1, LL2).
-
-is_compat_list(L1, L2) ->
-  length(L1) =:= length(L2) andalso is_compat_list1(L1, L2).
-
-is_compat_list1([], []) -> true;
-is_compat_list1([T1|L1], [T2|L2]) ->
-  is_compat_arg(T1, T2) andalso is_compat_list1(L1, L2).
-
-is_compat_union2(?union(List1)=T1, ?union(List2)=T2) ->
-  case {unify_union(List1), unify_union(List2)} of
-    {{yes, Type1}, {yes, Type2}} -> {yes, Type1, Type2};
-    {{yes, Type1}, no} -> {yes, Type1, T2};
-    {no, {yes, Type2}} -> {yes, T1, Type2};
-    {no, no} -> no
-  end.
-
 -spec t_inf_lists([erl_type()], [erl_type()]) -> [erl_type()].
 
 t_inf_lists(L1, L2) ->
@@ -3492,9 +3380,8 @@ t_subst_aux(?map(Pairs, DefK, DefV), Map) ->
   t_map([{K, MNess, t_subst_aux(V, Map)} || {K, MNess, V} <- Pairs],
 	t_subst_aux(DefK, Map), t_subst_aux(DefV, Map));
 t_subst_aux(?opaque(Es), Map) ->
-  List = [Opaque#opaque{args = [t_subst_aux(Arg, Map) || Arg <- Args],
-                        struct = t_subst_aux(S, Map)} ||
-           Opaque = #opaque{args = Args, struct = S} <- set_to_list(Es)],
+  List = [Opaque#opaque{struct = t_subst_aux(S, Map)} ||
+           Opaque = #opaque{struct = S} <- set_to_list(Es)],
   ?opaque(ordsets:from_list(List));
 t_subst_aux(?union(List), Map) ->
   ?union([t_subst_aux(E, Map) || E <- List]);
@@ -3748,18 +3635,18 @@ unify_union(List) ->
 is_opaque_type(?opaque(Elements), Opaques) ->
   lists:any(fun(Opaque) -> is_opaque_type2(Opaque, Opaques) end, Elements).
 
-is_opaque_type2(#opaque{mod = Mod1, name = Name1, args = Args1}, Opaques) ->
+is_opaque_type2(#opaque{mod = Mod1, name = Name1, arity = Arity1}, Opaques) ->
   F1 = fun(?opaque(Es)) ->
-           F2 = fun(#opaque{mod = Mod, name = Name, args = Args}) ->
-                    is_type_name(Mod1, Name1, Args1, Mod, Name, Args)
+           F2 = fun(#opaque{mod = Mod, name = Name, arity = Arity}) ->
+                    is_type_name(Mod1, Name1, Arity1, Mod, Name, Arity)
                 end,
            lists:any(F2, Es)
        end,
   lists:any(F1, Opaques).
 
-is_type_name(Mod, Name, Args1, Mod, Name, Args2) ->
-  length(Args1) =:= length(Args2);
-is_type_name(_Mod1, _Name1, _Args1, _Mod2, _Name2, _Args2) ->
+is_type_name(Mod, Name, Arity, Mod, Name, Arity) ->
+  true;
+is_type_name(_Mod1, _Name1, _Arity1, _Mod2, _Name2, _Arity2) ->
   false.
 
 %% Two functions since t_unify is not symmetric.
@@ -4476,8 +4363,8 @@ t_to_string(?identifier(Set), _RecDict) ->
       flat_join([flat_format("~w()", [T]) || T <- set_to_list(Set)], " | ")
   end;
 t_to_string(?opaque(Set), RecDict) ->
-  flat_join([opaque_type(Mod, Name, Args, S, RecDict) ||
-              #opaque{mod = Mod, name = Name, struct = S, args = Args}
+  flat_join([opaque_type(Mod, Name, Arity, S, RecDict) ||
+              #opaque{mod = Mod, name = Name, struct = S, arity = Arity}
                 <- set_to_list(Set)],
             " | ");
 t_to_string(?matchstate(Pres, Slots), RecDict) ->
@@ -4650,19 +4537,18 @@ union_sequence(Types, RecDict) ->
   flat_join(List, " | ").
 
 -ifdef(DEBUG).
-opaque_type(Mod, Name, _Args, S, RecDict) ->
-  ArgsString = comma_sequence(_Args, RecDict),
+opaque_type(Mod, Name, Arity, S, RecDict) ->
   String = t_to_string(S, RecDict),
-  opaque_name(Mod, Name, ArgsString) ++ "[" ++ String ++ "]".
+  opaque_name(Mod, Name, Arity) ++ "[" ++ String ++ "]".
 -else.
-opaque_type(Mod, Name, Args, _S, RecDict) ->
-  ArgsString = comma_sequence(Args, RecDict),
-  opaque_name(Mod, Name, ArgsString).
+opaque_type(Mod, Name, Arity, _S, _RecDict) ->
+  opaque_name(Mod, Name, Arity).
 -endif.
 
-opaque_name(Mod, Name, Extra) ->
+opaque_name(Mod, Name, Arity) ->
   S = mod_name(Mod, Name),
-  flat_format("~ts(~ts)", [S, Extra]).
+  Args = lists:join($,, lists:duplicate(Arity, $_)),
+  flat_format("~ts(~ts)", [S, Args]).
 
 mod_name(Mod, Name) ->
   flat_format("~w:~tw", [Mod, Name]).
diff --git a/lib/dialyzer/test/map_SUITE_data/results/opaque_key b/lib/dialyzer/test/map_SUITE_data/results/opaque_key
index b3a2d2b78c..b70157f1af 100644
--- a/lib/dialyzer/test/map_SUITE_data/results/opaque_key
+++ b/lib/dialyzer/test/map_SUITE_data/results/opaque_key
@@ -4,8 +4,8 @@ opaque_key_adt.erl:41:2: Invalid type specification for function opaque_key_adt:
 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:13: The test opaque_key_use:t() =:= opaque_key_use:t(_) can never evaluate to 'true'
+opaque_key_use.erl:24: Attempt to test for equality between a term of type opaque_key_adt:t(_) 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 opacity of the term
 opaque_key_use.erl:48: Function adt_mu1/0 has no local return
diff --git a/lib/dialyzer/test/opaque_SUITE_data/results/para b/lib/dialyzer/test/opaque_SUITE_data/results/para
index d0ddab7b66..0ba2a24996 100644
--- a/lib/dialyzer/test/opaque_SUITE_data/results/para
+++ b/lib/dialyzer/test/opaque_SUITE_data/results/para
@@ -1,34 +1,24 @@
 
-para1.erl:18: The test para1:t(atom()) =:= para1:t(integer()) can never evaluate to 'true'
-para1.erl:23: The test para1:t(atom()) =:= para1:t() can never evaluate to 'true'
-para1.erl:28: The test para1:t() =:= para1:t(integer()) can never evaluate to 'true'
+para1.erl:18: The test para1:t(_) =:= para1:t(_) can never evaluate to 'true'
+para1.erl:23: The test para1:t(_) =:= para1:t() can never evaluate to 'true'
+para1.erl:28: The test para1:t() =:= para1:t(_) can never evaluate to 'true'
 para1.erl:33: The test {3,2} =:= {'a','b'} can never evaluate to 'true'
-para1.erl:38: Attempt to test for equality between a term of type para1_adt:t(integer()) and a term of opaque type para1_adt:t(atom())
-para1.erl:43: Attempt to test for equality between a term of type para1_adt:t() and a term of opaque type para1_adt:t(atom())
-para1.erl:48: Attempt to test for equality between a term of type para1_adt:t(integer()) and a term of opaque type para1_adt:t()
+para1.erl:38: The test para1_adt:t(_) =:= para1_adt:t(_) can never evaluate to 'true'
+para1.erl:43: Attempt to test for equality between a term of type para1_adt:t() and a term of opaque type para1_adt:t(_)
+para1.erl:48: Attempt to test for equality between a term of type para1_adt:t(_) and a term of opaque type para1_adt:t()
 para1.erl:53: The test {3,2} =:= {'a','b'} can never evaluate to 'true'
-para2.erl:103: Attempt to test for equality between a term of type para2_adt:circ(integer(),integer()) and a term of opaque type para2_adt:circ(integer())
-para2.erl:117: Attempt to test for equality between a term of type para2_adt:un(atom(),integer()) and a term of opaque type para2_adt:un(integer(),atom())
+para2.erl:103: Attempt to test for equality between a term of type para2_adt:circ(_,_) and a term of opaque type para2_adt:circ(_)
 para2.erl:31: The test 'a' =:= 'b' can never evaluate to 'true'
 para2.erl:61: Attempt to test for equality between a term of type para2_adt:c2() and a term of opaque type para2_adt:c1()
 para2.erl:66: The test 'a' =:= 'b' can never evaluate to 'true'
-para2.erl:88: The test para2:circ(integer()) =:= para2:circ(integer(),integer()) can never evaluate to 'true'
+para2.erl:88: The test para2:circ(_) =:= para2:circ(_,_) can never evaluate to 'true'
 para3.erl:28: Invalid type specification for function para3:ot2/0. The success typing is () -> 'foo'
 para3.erl:36: The pattern {{{17}}} can never match the type {{{{{{_,_,_,_,_}}}}}}
 para3.erl:55: Invalid type specification for function para3:t2/0. The success typing is () -> 'foo'
 para3.erl:65: The attempt to match a term of type {{{{{para3_adt:ot1(_,_,_,_,_)}}}}} against the pattern {{{{{17}}}}} breaks the opacity of para3_adt:ot1(_,_,_,_,_)
 para3.erl:68: The pattern {{{{17}}}} can never match the type {{{{{para3_adt:ot1(_,_,_,_,_)}}}}}
-para3.erl:74: The specification for para3:exp_adt/0 has an opaque subtype para3_adt:exp1(para3_adt:exp2()) which is violated by the success typing () -> 3
-para4.erl:21: Invalid type specification for function para4:a/1. The success typing is (para4:d_all() | para4:d_atom()) -> [{atom() | integer(),atom() | integer()}]
-para4.erl:26: Invalid type specification for function para4:i/1. The success typing is (para4:d_all() | para4:d_integer()) -> [{atom() | integer(),atom() | integer()}]
+para3.erl:74: The specification for para3:exp_adt/0 has an opaque subtype para3_adt:exp1(_) which is violated by the success typing () -> 3
 para4.erl:31: Invalid type specification for function para4:t/1. The success typing is (para4:d_all() | para4:d_tuple()) -> [{atom() | integer(),atom() | integer()}]
-para4.erl:59: Attempt to test for equality between a term of type para4_adt:t(atom() | integer()) and a term of opaque type para4_adt:t(integer())
-para4.erl:64: Attempt to test for equality between a term of type para4_adt:t(atom() | integer()) and a term of opaque type para4_adt:t(atom())
-para4.erl:69: Attempt to test for equality between a term of type para4_adt:int(1 | 2 | 3 | 4) and a term of opaque type para4_adt:int(1 | 2)
-para4.erl:74: Attempt to test for equality between a term of type para4_adt:int(2 | 3 | 4) and a term of opaque type para4_adt:int(1 | 2)
-para4.erl:79: Attempt to test for equality between a term of type para4_adt:int(2 | 3 | 4) and a term of opaque type para4_adt:int(5 | 6 | 7)
-para4.erl:84: Attempt to test for equality between a term of type para4_adt:un(3 | 4) and a term of opaque type para4_adt:un(1 | 2)
-para4.erl:89: Attempt to test for equality between a term of type para4_adt:tup({_,_}) and a term of opaque type para4_adt:tup(tuple())
-para4.erl:94: Attempt to test for equality between a term of type para4_adt:t(#{1=>'a'}) and a term of opaque type para4_adt:t(#{2=>'b'})
-para5.erl:13: Attempt to test for inequality between a term of type para5_adt:dd(atom()) and a term of opaque type para5_adt:d()
+para4.erl:79: The test para4_adt:int(_) =:= para4_adt:int(_) can never evaluate to 'true'
+para5.erl:13: Attempt to test for inequality between a term of type para5_adt:dd(_) and a term of opaque type para5_adt:d()
 para5.erl:8: The test para5_adt:d() =:= para5_adt:d() can never evaluate to 'true'
-- 
2.31.1

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File 4365-erl_types-Ignore-opaque-type-arguments.patch of Package erlang (Revision a7029ee97b719a45764ae3b135bbdda2)

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