meaning of "Production 'xxx' is not reachable"? about rply HOT 1 OPEN

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.

from rply.