Antlr4.Runtime.Atn.ATNDeserializer.VerifyATN C# (CSharp) Method

        protected internal virtual void VerifyATN(ATN atn)
        {
            // verify assumptions
            foreach (ATNState state in atn.states)
            {
                if (state == null)
                {
                    continue;
                }
                CheckCondition(state.OnlyHasEpsilonTransitions || state.NumberOfTransitions <= 1);
                if (state is PlusBlockStartState)
                {
                    CheckCondition(((PlusBlockStartState)state).loopBackState != null);
                }
                if (state is StarLoopEntryState)
                {
                    StarLoopEntryState starLoopEntryState = (StarLoopEntryState)state;
                    CheckCondition(starLoopEntryState.loopBackState != null);
                    CheckCondition(starLoopEntryState.NumberOfTransitions == 2);
                    if (starLoopEntryState.Transition(0).target is StarBlockStartState)
                    {
                        CheckCondition(starLoopEntryState.Transition(1).target is LoopEndState);
                        CheckCondition(!starLoopEntryState.nonGreedy);
                    }
                    else
                    {
                        if (starLoopEntryState.Transition(0).target is LoopEndState)
                        {
                            CheckCondition(starLoopEntryState.Transition(1).target is StarBlockStartState);
                            CheckCondition(starLoopEntryState.nonGreedy);
                        }
                        else
                        {
                            throw new InvalidOperationException();
                        }
                    }
                }
                if (state is StarLoopbackState)
                {
                    CheckCondition(state.NumberOfTransitions == 1);
                    CheckCondition(state.Transition(0).target is StarLoopEntryState);
                }
                if (state is LoopEndState)
                {
                    CheckCondition(((LoopEndState)state).loopBackState != null);
                }
                if (state is RuleStartState)
                {
                    CheckCondition(((RuleStartState)state).stopState != null);
                }
                if (state is BlockStartState)
                {
                    CheckCondition(((BlockStartState)state).endState != null);
                }
                if (state is BlockEndState)
                {
                    CheckCondition(((BlockEndState)state).startState != null);
                }
                if (state is DecisionState)
                {
                    DecisionState decisionState = (DecisionState)state;
                    CheckCondition(decisionState.NumberOfTransitions <= 1 || decisionState.decision >= 0);
                }
                else
                {
                    CheckCondition(state.NumberOfTransitions <= 1 || state is RuleStopState);
                }
            }
        }