lib: Fix conversion to canonic automaton

In some cases, the states could be spuriously merged when converting to canonic
automaton. This is now fixed.

lib/dfa.py

@@ -312,26 +312,30 @@ class DFA:
         return name
 
     def canonize(self) -> DFA:
-        dfa = deepcopy(self)
-        remain = deepcopy(self.states)
-        characters = dfa.sorted_characters()
+        characters = self.sorted_characters()
+        state_map: Dict[State, State] = {}
 
-        i = 0
-        queue = deque([dfa.init])
+        i = 1
+        queue = deque([self.init])
         while len(queue) > 0:
             actual = queue.popleft()
-            if actual in remain:
-                remain.remove(actual)
+            if actual in state_map.keys():
+                continue
+            # alternatively, use self.bijective26(i) for base-26 alpha. names
+            state_map[actual] = State(str(i))
+            i += 1
 
             for character in characters:
-                if (actual, character) in dfa.transition and dfa.transition[actual, character] in remain:
-                    queue.append(dfa.transition[actual, character])
-                    remain.remove(dfa.transition[actual, character])
-
-            # use self.bijective26(i) for base-26 alphabetic names
-            dfa.rename_state(actual, str(i + 1))
-            i += 1
-        return dfa
+                tgt = self.transition.get((actual, character))
+                if tgt is not None and tgt not in state_map.keys():
+                    queue.append(tgt)
+
+        return DFA(set(state_map.values()),
+                   deepcopy(self.characters),
+                   {(state_map[st], ch): state_map[tgt]
+                    for (st, ch), tgt in self.transition.items()},
+                   state_map[self.init],
+                   {state_map[st] for st in self.final})
 
     # support function: decides from which of reachable states there is a way to final state
     def terminating_states(self, states: Set[State], pred: Dict[State, Set[State]]) -> Set[State]: