Build: NetBeans IDE 8.1 (Build 201510222201)
VM: Java HotSpot(TM) 64-Bit Server VM, 25.141-b15, Java(TM) SE Runtime Environment, 1.8.0_141-b15
OS: Mac OS X

User Comments:
mklaehn: editing a grammar. the editor marks several lines as error notations ("error(100): line:column: syntax error: antlr: NoViableAltException(69@[])"

this happens for example at the following rule:
globalStatement
    :
        KEYWORD_GLOBAL
        (
            IDENTIFIER
            CHAR_COMMA?
        )+?
    ;
with the question mark underlined

here:
// newline
NL
    :
        (
            '\r'?
            '\n'
        )-> channel(HIDDEN)
    ;

with channel(HIDDEN) underlined

or at the following rule:
// white space to be ignored
WS
    :
        (
            ' '
        |
            '\t'
        ) -> skip
    ;
with skip underlined

GUEST: when creating new rules or moving to rules per navigator

GUEST: Opening a antlr3 grammar file

GUEST: -

GUEST: error

GUEST: Anytime I Open the grammar file, this exception occurs.




Stacktrace: 
java.lang.NullPointerException
   at org.antlr.works.editor.grammar.experimental.CurrentRuleContextParserTask.parse(CurrentRuleContextParserTask.java:83)
   at org.antlr.netbeans.parsing.spi.impl.ParserTaskManagerImpl$UpdateDataCallable.callImpl(ParserTaskManagerImpl.java:662)
   at org.antlr.netbeans.parsing.spi.impl.ParserTaskManagerImpl$UpdateDataCallable.callImpl(ParserTaskManagerImpl.java:618)
   at org.antlr.netbeans.parsing.spi.impl.ParserTaskManagerImpl$UpdateCallable.call(ParserTaskManagerImpl.java:607)
   at java.util.concurrent.FutureTask.run(FutureTask.java:266)
   at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:180)