[antlr-interest] How to use String Attributes in ANTLR3

[Foolish Ewe]

Hello All:

I'm trying to add backend support to my grammar and for my convenience,  I 
would like to have
Java Strings "synthetic attributes" passed from the bottom up in the grammar 
(so that I can
access them in non terminal productions).  I tried following the approach 
that appears to
be suggested in the expression evaluator in the wiki, at:
http://www.antlr.org/wiki/display/ANTLR3/Expression+evaluator

However, something like:

testCommandSuffix returns [String text]
	:
		ACTION {$text = $ACTION.text;}
	;

generates errors reported in the console reading:

[15:55:48] error(151): C:\temp\TestGrammar.g:111:10: cannot write to read 
only attribute: $text.
[15:55:49] error(10):  internal error: 
org.antlr.tool.Message.toString(Message.java:124): Assertion failed! Message 
ID 151 created but is not present in errorMsgIDs or warningMsgIDs.

Have I made an error here, if so, how can I fix it?  Otherwise, how does one 
specify a
synthetic attribute in ANTLR?

I have also noticed that in ANTLRworks 1.0b8, when trying to generate 
grammars, sometimes if I get
an error, I will get a popup window reading:
"Grammar Check failed:
  null
  Check Console for more Information"

and if I try to edit the grammar or regenerate it, the console window does 
not get any new
diagnostic messages routed to it.  Does anyone else get this?

Thanks:

Bill M.

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