[antlr-interest] RewriteEmptyStreamException

[Jamie Penney]

Hi All,
I am getting the following exception when executing a rewrite rule:

Antlr.Runtime.Tree.RewriteEmptyStreamException: rule type
   at Antlr.Runtime.Tree.RewriteRuleElementStream`1._Next()
   at 
Antlr.Runtime.Tree.RewriteRuleSubtreeStream.FetchObject(ProcessHandler ph)
   at Antlr.Runtime.Tree.RewriteRuleSubtreeStream.NextTree()
   at Kerriv.CSharpML.CSharp3ParserSyntax.using_namespace_directive() in 
....


This is cause by the code generated from the following rule:
using_namespace_directive
    :    USING type SEMICOLON -> ^(USING type SEMICOLON)
    ;

Any ideas as to where I should start with this? The documentation and 
Google haven't given me any clues.

Thanks,
Jamie Penney