dialyzer: Fix opaque bugs

t_from_form() sometimes returned a more general type than it should
have done due to a bug in from_form_loop(): it stopped when the limit
was exceeded, which could mean a collapsed type. Returning a type with
smaller depth should fix this.

is_specialization() now handles opaque types before unions, which
should fix another problem.

The bugs reported by Kostis.

1 files changed, 14 insertions, 11 deletions

diff --git a/lib/hipe/cerl/erl_types.erl b/lib/hipe/cerl/erl_types.erl
index 15f7b793a1..a6a7efb1de 100644
--- a/lib/hipe/cerl/erl_types.erl
+++ b/lib/hipe/cerl/erl_types.erl
@@ -3109,6 +3109,10 @@ is_specialization(?tuple_set(List1), ?tuple_set(List2)) ->
                              [sup_tuple_elements(T) || {_Arity, T} <- List2])
   catch _:_ -> false
   end;
+is_specialization(?opaque(_) = T1, T2) ->
+  is_specialization(t_opaque_structure(T1), T2);
+is_specialization(T1, ?opaque(_) = T2) ->
+  is_specialization(T1, t_opaque_structure(T2));
 is_specialization(?union(List1)=T1, ?union(List2)=T2) ->
   case specialization_union2(T1, T2) of
     {yes, Type1, Type2} -> is_specialization(Type1, Type2);
@@ -3124,10 +3128,6 @@ is_specialization(T1, ?union(List)) ->
       {yes, Type} -> is_specialization(T1, Type);
       no -> false
   end;
-is_specialization(?opaque(_) = T1, T2) ->
-  is_specialization(t_opaque_structure(T1), T2);
-is_specialization(T1, ?opaque(_) = T2) ->
-  is_specialization(T1, t_opaque_structure(T2));
 is_specialization(?var(_), _) -> exit(error);
 is_specialization(_, ?var(_)) -> exit(error);
 is_specialization(?none, _) -> false;
@@ -4482,28 +4482,31 @@ t_from_form1(Form, ET, Site, MR, V, C) ->
                      vtab   = V,
                      tnames = TypeNames},
   L = ?EXPAND_LIMIT,
-  {T1, L1, C1} = from_form(Form, State, ?EXPAND_DEPTH, L, C),
+  {T0, L0, C0} = from_form(Form, State, ?EXPAND_DEPTH, L, C),
   if
-    L1 =< 0 ->
-      from_form_loop(Form, State, 1, L, C1);
+    L0 =< 0 ->
+      {T1, _, C1} = from_form(Form, State, 1, L, C0),
+      from_form_loop(Form, State, 2, L, C1, T1);
     true ->
-       {T1, C1}
+       {T0, C0}
   end.
 
 initial_typenames({type, _MTA}=Site) -> [Site];
 initial_typenames({spec, _MFA}) -> [];
 initial_typenames({record, _MRA}) -> [].
 
-from_form_loop(Form, State, D, Limit, C) ->
+from_form_loop(Form, State, D, Limit, C, T0) ->
   {T1, L1, C1} = from_form(Form, State, D, Limit, C),
   Delta = Limit - L1,
   if
-    %% Save some time by assuming next depth will exceed the limit.
+    L1 =< 0 ->
+      {T0, C1};
     Delta * 8 > Limit ->
+      %% Save some time by assuming next depth will exceed the limit.
       {T1, C1};
     true ->
       D1 = D + 1,
-      from_form_loop(Form, State, D1, Limit, C1)
+      from_form_loop(Form, State, D1, Limit, C1, T1)
   end.
 
 -spec from_form(parse_form(),