[antlr-interest] java.lang.NullPointerException

[QinYong]

HI
if UP or DOWN keyword is in ANTLRv3 tokens grammar

tokens {
 UP='up';
}
or
tokens {
 DOWN='down';
}

I got following java.lang.NullPointerException , who can tell me why?

[antlr:antlr3] ANTLR Parser Generator  Version 3.0.1 (August 13, 2007)  1989-2007
[antlr:antlr3] error(10):  internal error: C:\eclipse3.1.1\workspace\CobolParser\grammar\Cobol.g : java.lang.NullPointerException
[antlr:antlr3] org.antlr.tool.AssignTokenTypesWalker.aliasTokenIDsAndLiterals(AssignTokenTypesWalker.java:257)
[antlr:antlr3] org.antlr.tool.AssignTokenTypesWalker.assignTypes(AssignTokenTypesWalker.java:211)
[antlr:antlr3] org.antlr.tool.AssignTokenTypesWalker.grammar(AssignTokenTypesWalker.java:375)
[antlr:antlr3] org.antlr.tool.Grammar.setGrammarContent(Grammar.java:547)
[antlr:antlr3] org.antlr.tool.Grammar.<init>(Grammar.java:456)
[antlr:antlr3] org.antlr.Tool.getGrammar(Tool.java:331)
[antlr:antlr3] org.antlr.Tool.process(Tool.java:267)
[antlr:antlr3] org.antlr.Tool.main(Tool.java:70)


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