remfin: fix a corner case for rabin_to_buchi_maybe

when fin_alone sets where presents (i.e., not really Rabin condition),
the rabin_to_buchi_maybe() could fail to notice DBA-typeness.

* spot/twaalgos/remfin.cc: Don't set scc_ba_type to false when
fin_alone is present.
* tests/core/remfin.test: Add a test case.

NEWS

@@ -36,6 +36,12 @@ New in spot 2.3.2.dev (not yet released)
   - In bench/stutter/ the .cc files were not compiling due to warnings being
     caught as errors.
 
+  - The code in charge of detecting DBA-type Rabin automata is
+    actually written to handle a slightly larger class of acceptance
+    conditions (e.g., Fin(0)|(Fin(1)&Inf(2))), however it failed to
+    correctly detect DBA-typeness in some of these non-Rabin
+    acceptance.
+
   Backward-incompatible changes:
 
   - spot::acc_cond::mark_t::operator bool() has been marked as

spot/twaalgos/remfin.cc

@@ -73,7 +73,7 @@ namespace spot
       // accepting, but which becomes non-accepting when extended with
       // more states.
       i -= f;
-      i |= (inf_alone & sets);
+      i |= inf_alone & sets;
       if (!i)
         {
           // Check whether the SCC is accepting.  We do that by simply
@@ -192,14 +192,9 @@ namespace spot
                 ba_final_states[s] = true;
               scc_ba_type = true;
             }
-          // Conversely, if all fin_alone appear in the SCC, then it
+          // In the general case, we need a dedicated check.  Note
-          // cannot be accepting.
+          // that the used fin_alone sets can be ignored, as they
-          else if (sets & fin_alone)
+          // cannot contribute to Büchi-typeness,
-            {
-              scc_ba_type = false;
-            }
-          // In the generale case (no fin_alone involved), we need
-          // a dedicated check.
           else
             {
               scc_ba_type = is_scc_ba_type(aut, si.states_of(scc),

tests/core/remfin.test

@@ -1,7 +1,8 @@
 #!/bin/sh
 # -*- coding: utf-8 -*-
-# Copyright (C) 2015, 2016 Laboratoire de Recherche et Développement
+
-# de l'Epita (LRDE).
+# Copyright (C) 2015-2017 Laboratoire de Recherche et Développement de
+# l'Epita (LRDE).
 #
 # This file is part of Spot, a model checking library.
 #
@@ -236,6 +237,19 @@ State: 15 [t] 15 {4 15} [1] 16 {4} [!1] 22 {15} State: 16 [t] 16 {4 16}
 [t] 31 {14} [!1] 32 State: 32 [t] 32 {15} [1] 33 State: 33 [t] 33 {16}
 [!1] 36 State: 34 [t] 34 State: 35 [1] 34 {11} [!1] 35 {5} State: 36
 [1] 34 {23} [!1] 36 {17} --END--
+HOA: v1
+States: 2
+Acceptance: 3 Fin(0) | (Fin(1)&Inf(2))
+Start: 0
+AP: 1 "a"
+--BODY--
+State: 0 {0}
+[0] 1
+[!0] 0
+State: 1 {2}
+[0] 1
+[!0] 0
+--END--
 EOF
 
 acctwelve='Inf(0)&Inf(1)&Inf(2)&Inf(3)&Inf(4)&Inf(5)'
@@ -713,6 +727,22 @@ State: 36
 [1] 34
 [!1] 36 {0 1 2 3 4 5 6 7 8 9 10}
 --END--
+HOA: v1
+States: 2
+Start: 0
+AP: 1 "a"
+acc-name: Buchi
+Acceptance: 1 Inf(0)
+properties: trans-labels explicit-labels state-acc complete
+properties: deterministic
+--BODY--
+State: 0
+[0] 1
+[!0] 0
+State: 1 {0}
+[0] 1
+[!0] 0
+--END--
 EOF
 
 cat >expected-tgba <<EOF
@@ -1156,6 +1186,22 @@ State: 36
 [1] 34
 [!1] 36
 --END--
+HOA: v1
+States: 2
+Start: 0
+AP: 1 "a"
+acc-name: Buchi
+Acceptance: 1 Inf(0)
+properties: trans-labels explicit-labels state-acc complete
+properties: deterministic
+--BODY--
+State: 0
+[!0] 0
+[0] 1
+State: 1 {0}
+[!0] 0
+[0] 1
+--END--
 EOF
 
 run 0 $autfilt -H --remove-fin test1 > output