From 02e0f98ab537b002f2ccb1092d9e7310d9e15c58 Mon Sep 17 00:00:00 2001
From: Stavros Aronis <aronisstav@gmail.com>
Date: Mon, 3 Jan 2011 15:07:55 +0200
Subject: Fix errors in the handling of 'and'/'or' guards

Apart from the obvious bug in the negative evaluation of an 'and'
guard, Dialyzer handled dont_know cases rather single-mindedly
towards the positive branch. This patch allows for negative results
as well and does some clever guesses to narrow them down. It was
constructed similarly to the handling of the 'not' guard.
---
 lib/dialyzer/src/dialyzer_dataflow.erl | 47 +++++++++++++++++++++++-----------
 1 file changed, 32 insertions(+), 15 deletions(-)

(limited to 'lib/dialyzer/src/dialyzer_dataflow.erl')

diff --git a/lib/dialyzer/src/dialyzer_dataflow.erl b/lib/dialyzer/src/dialyzer_dataflow.erl
index 0e51ce059c..1723380c8c 100644
--- a/lib/dialyzer/src/dialyzer_dataflow.erl
+++ b/lib/dialyzer/src/dialyzer_dataflow.erl
@@ -2250,24 +2250,30 @@ handle_guard_and(Guard, Map, Env, Eval, State) ->
 	catch throw:{fail, _} -> bind_guard(Arg2, Map, Env, pos, State)
 	end,
       {Map2, Type2} =
-	try bind_guard(Arg1, Map, Env, neg, State)
-	catch throw:{fail, _} -> bind_guard(Arg2, Map, Env, pos, State)
+	try bind_guard(Arg2, Map, Env, neg, State)
+	catch throw:{fail, _} -> bind_guard(Arg1, Map, Env, pos, State)
 	end,
       case t_is_atom(false, Type1) orelse t_is_atom(false, Type2) of
 	true -> {join_maps([Map1, Map2], Map), t_atom(false)};
 	false -> throw({fail, none})
       end;
     dont_know ->
-      True = t_atom(true),
       {Map1, Type1} = bind_guard(Arg1, Map, Env, dont_know, State),
-      case t_is_none(t_inf(Type1, t_boolean())) of
-	true -> throw({fail, none});
+      {Map2, Type2} = bind_guard(Arg2, Map, Env, dont_know, State),
+      Bool1 = t_inf(Type1, t_boolean()),
+      Bool2 = t_inf(Type2, t_boolean()),
+      case t_is_none(Bool1) orelse t_is_none(Bool2) of
+	true -> throw({fatal_fail, none});
 	false ->
-	  {Map2, Type2} = bind_guard(Arg2, Map1, Env, Eval, State),
-	  case t_is_none(t_inf(Type2, t_boolean())) of
-	    true -> throw({fail, none});
-	    false -> {Map2, True}
-	  end
+	  NewMap = join_maps([Map1, Map2], Map),
+	  NewType =
+	    case {t_atom_vals(Bool1), t_atom_vals(Bool2)} of
+	      {['true'] , ['true'] } -> t_atom(true);
+	      {['false'], _        } -> t_atom(false);
+	      {_        , ['false']} -> t_atom(false);
+	      {_        , _        } -> t_boolean()
+	    end,
+	  {NewMap, NewType}
       end
   end.
 
@@ -2303,11 +2309,22 @@ handle_guard_or(Guard, Map, Env, Eval, State) ->
 	  end
       end;
     dont_know ->
-      {Map1, Bool1} = bind_guard(Arg1, Map, Env, dont_know, State),
-      {Map2, Bool2} = bind_guard(Arg2, Map, Env, dont_know, State),
-      case t_is_boolean(Bool1) andalso t_is_boolean(Bool2) of
-	true -> {join_maps([Map1, Map2], Map), t_sup(Bool1, Bool2)};
-	false -> throw({fail, none})
+      {Map1, Type1} = bind_guard(Arg1, Map, Env, dont_know, State),
+      {Map2, Type2} = bind_guard(Arg2, Map, Env, dont_know, State),
+      Bool1 = t_inf(Type1, t_boolean()),
+      Bool2 = t_inf(Type2, t_boolean()),
+      case t_is_none(Bool1) orelse t_is_none(Bool2) of
+	true -> throw({fatal_fail, none});
+	false ->
+	  NewMap = join_maps([Map1, Map2], Map),
+	  NewType =
+	    case {t_atom_vals(Bool1), t_atom_vals(Bool2)} of
+	      {['false'], ['false']} -> t_atom(false);
+	      {['true'] , _        } -> t_atom(true);
+	      {_        , ['true'] } -> t_atom(true);
+	      {_        , _        } -> t_boolean()
+	    end,
+	  {NewMap, NewType}
       end
   end.
 
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