[antlr-interest] error(106): reference to undefined rule

[Hesham Zakaria]

Hi,
I am new to antlr, and I am facing the error(106): reference to undefined rule.

The grammar check is successful but the code generation raises an error.

The grammar is just a test:

grammar test;
TERM    : atom ( ',' atom )*  ;
atom    : TERM ( ',' TERM)*   ; 

and the error is:
error(106): test.g:2:8: reference to undefined rule: atom

Thanks for help,
Hesham