neverclaim: fix parsing of aliased states

* src/graph/ngraph.hh (alias_states): Deal with the case
of aliasing two existing states.
* src/hoaparse/hoaparse.yy: Fix handling of aliased states.
* src/tgbatest/neverclaimread.test: Augment test case.

src/graph/ngraph.hh

@@ -78,10 +78,36 @@ namespace spot
     }
 
     /// \brief Give an alternate name to a state.
-    /// \return true iff the newname was already used.
+    /// \return true iff the newname state was already existing
+    /// (in this case the existing newname state will be merged
+    /// with state s: the newname will be unreachable and without
+    /// successors.)
     bool alias_state(state s, name newname)
     {
-      return !name_to_state.emplace(newname, s).second;
+      auto p = name_to_state.emplace(newname, s);
+      if (!p.second)
+	{
+	  // The state already exists.  Change its number.
+	  auto old = p.first->second;
+	  p.first->second = s;
+	  // Add the successor of OLD to those of S.
+	  auto& trans = g_.transitions();
+	  auto& states = g_.states();
+	  trans[states[s].succ_tail].next_succ = states[old].succ;
+	  states[s].succ_tail = states[old].succ_tail;
+	  states[old].succ = 0;
+	  states[old].succ_tail = 0;
+	  // Remove all references to old in transitions:
+	  unsigned tend = trans.size();
+	  for (unsigned t = 1; t < tend; ++t)
+	    {
+	      if (trans[t].src == old)
+		trans[t].src = s;
+	      if (trans[t].dst == old)
+		trans[t].dst = s;
+	    }
+	}
+      return !p.second;
     }
 
     state get_state(name n) const

src/hoaparse/hoaparse.yy

@@ -88,6 +88,7 @@
 
     bool accept_all_needed = false;
     bool accept_all_seen = false;
+    bool aliased_states = false;
     std::map<std::string, spot::location> labels;
 
     ~result_()
@@ -732,6 +733,10 @@ never: "never" { res.namer = res.h->aut->create_namer<std::string>();
 	     unsigned n = res.namer->new_state("accept_all");
 	     res.h->aut->new_acc_transition(n, n, bddtrue);
 	   }
+	 // If we aliased existing state, we have some unreachable
+	 // states to remove.
+	 if (res.aliased_states)
+	   res.h->aut->purge_unreachable_states();
        }
 
 nc-states:
@@ -742,12 +747,6 @@ nc-states:
 
 nc-one-ident: IDENTIFIER ':'
     {
-      unsigned n = res.namer->new_state(*$1);
-      if (res.labels.empty())
-	{
-	  // The first state is initial.
-	  res.start.emplace_back(@$, n);
-	}
       auto r = res.labels.insert(std::make_pair(*$1, @1));
       if (!r.second)
 	{
@@ -759,9 +758,19 @@ nc-one-ident: IDENTIFIER ':'
     }
 
 nc-ident-list: nc-one-ident
+    {
+      unsigned n = res.namer->new_state(*$1);
+      if (res.start.empty())
+	{
+	  // The first state is initial.
+	  res.start.emplace_back(@$, n);
+	}
+      $$ = $1;
+    }
   | nc-ident-list nc-one-ident
     {
-      res.namer->alias_state(res.namer->get_state(*$1), *$2);
+      res.aliased_states |=
+	res.namer->alias_state(res.namer->get_state(*$1), *$2);
       // Keep any identifier that starts with accept.
       if (strncmp("accept", $1->c_str(), 6))
         {
@@ -791,10 +800,9 @@ nc-state:
       if (*$1 == "accept_all")
 	res.accept_all_seen = true;
 
-      res.namer->new_transition(*$1, *$1, bddtrue,
-				!strncmp("accept", $1->c_str(), 6) ?
-				res.h->aut->acc().all_sets() :
-				spot::acc_cond::mark_t(0U));
+      auto acc = !strncmp("accept", $1->c_str(), 6) ?
+	res.h->aut->acc().all_sets() : spot::acc_cond::mark_t(0U);
+      res.namer->new_transition(*$1, *$1, bddtrue, acc);
       delete $1;
     }
   | nc-ident-list { delete $1; }

src/tgbatest/neverclaimread.test

@@ -31,12 +31,15 @@ if
 :: (p1 && p0) -> goto T1
 fi;
 T1:
+T1b: /* alias */
 if
-:: (p1 && (! p0)) -> goto accept_all
-:: !(p1) -> goto T1
+:: (p1 && (! p0)) -> goto alias2
+:: !(p1) -> goto T1b
 :: ! (p1) -> goto T2_init
 fi;
+alias1:
 accept_all:
+alias2:
 skip
 }
 EOF