Antlr.Runtime.BaseRecognizer.GetErrorMessage C# (CSharp) Method

        public virtual string GetErrorMessage( RecognitionException e, string[] tokenNames )
        {
            string msg = e.Message;
            if ( e is UnwantedTokenException )
            {
                UnwantedTokenException ute = (UnwantedTokenException)e;
                string tokenName = "<unknown>";
                if ( ute.Expecting == TokenTypes.EndOfFile )
                {
                    tokenName = "EndOfFile";
                }
                else
                {
                    tokenName = tokenNames[ute.Expecting];
                }
                msg = "extraneous input " + GetTokenErrorDisplay( ute.UnexpectedToken ) +
                    " expecting " + tokenName;
            }
            else if ( e is MissingTokenException )
            {
                MissingTokenException mte = (MissingTokenException)e;
                string tokenName = "<unknown>";
                if ( mte.Expecting == TokenTypes.EndOfFile )
                {
                    tokenName = "EndOfFile";
                }
                else
                {
                    tokenName = tokenNames[mte.Expecting];
                }
                msg = "missing " + tokenName + " at " + GetTokenErrorDisplay( e.Token );
            }
            else if ( e is MismatchedTokenException )
            {
                MismatchedTokenException mte = (MismatchedTokenException)e;
                string tokenName = "<unknown>";
                if ( mte.Expecting == TokenTypes.EndOfFile )
                {
                    tokenName = "EndOfFile";
                }
                else
                {
                    tokenName = tokenNames[mte.Expecting];
                }
                msg = "mismatched input " + GetTokenErrorDisplay( e.Token ) +
                    " expecting " + tokenName;
            }
            else if ( e is MismatchedTreeNodeException )
            {
                MismatchedTreeNodeException mtne = (MismatchedTreeNodeException)e;
                string tokenName = "<unknown>";
                if ( mtne.Expecting == TokenTypes.EndOfFile )
                {
                    tokenName = "EndOfFile";
                }
                else
                {
                    tokenName = tokenNames[mtne.Expecting];
                }
                // workaround for a .NET framework bug (NullReferenceException)
                string nodeText = ( mtne.Node != null ) ? mtne.Node.ToString() ?? string.Empty : string.Empty;
                msg = "mismatched tree node: " + nodeText + " expecting " + tokenName;
            }
            else if ( e is NoViableAltException )
            {
                //NoViableAltException nvae = (NoViableAltException)e;
                // for development, can add "decision=<<"+nvae.grammarDecisionDescription+">>"
                // and "(decision="+nvae.decisionNumber+") and
                // "state "+nvae.stateNumber
                msg = "no viable alternative at input " + GetTokenErrorDisplay( e.Token );
            }
            else if ( e is EarlyExitException )
            {
                //EarlyExitException eee = (EarlyExitException)e;
                // for development, can add "(decision="+eee.decisionNumber+")"
                msg = "required (...)+ loop did not match anything at input " +
                    GetTokenErrorDisplay( e.Token );
            }
            else if ( e is MismatchedSetException )
            {
                MismatchedSetException mse = (MismatchedSetException)e;
                msg = "mismatched input " + GetTokenErrorDisplay( e.Token ) +
                    " expecting set " + mse.Expecting;
            }
            else if ( e is MismatchedNotSetException )
            {
                MismatchedNotSetException mse = (MismatchedNotSetException)e;
                msg = "mismatched input " + GetTokenErrorDisplay( e.Token ) +
                    " expecting set " + mse.Expecting;
            }
            else if ( e is FailedPredicateException )
            {
                FailedPredicateException fpe = (FailedPredicateException)e;
                msg = "rule " + fpe.RuleName + " failed predicate: {" +
                    fpe.PredicateText + "}?";
            }
            return msg;
        }

        public static SyntaxErrorException Report(BaseRecognizer source, RecognitionException e)
        {
            var input = source.Input.ToString();
            if (source.Input is ANTLRStringStream)
                input = new String((Char[])typeof(ANTLRStringStream).GetField("data", 
                    BindingFlags.NonPublic | BindingFlags.Instance).GetValue(source.Input));

            var antlrMessage = source.GetErrorHeader(e) + " " + source.GetErrorMessage(e, source.TokenNames);
            throw new SyntaxErrorException(input, antlrMessage, e);
        }