meaning of "Production 'xxx' is not reachable"? #108

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1. nobodxbodon commented on Jun 8, 2021

   

   nobodxbodon

   on Jun 8, 2021

   Last edited by nobodxbodon

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   With some debugging, I realize that case 1 and 3 failed not because there was no warning, but because there were 2 warnings instead of 1. The additional warning was Token 'OTHER' is unused.

   So I adjust the case by removing 'OTHER', and it still gives warning "Production 'unused' is not reachable":

           pg = ParserGenerator(["VALUE"])
   
           @pg.production("main : VALUE")
           def main(p):
               return p[0]
   
           @pg.production("unused : main")
           def unused(p):
               pass

   Then, switch the order of the two production rules:

           pg = ParserGenerator(["VALUE"])
   
           @pg.production("unused : main")
           def unused(p):
               pass
   
           @pg.production("main : VALUE")
           def main(p):
               return p[0]

   Now it gives no warning.

   Seems a bug to me, as the order of production rules shouldn't have effects on the parsing outcome.