[antlr-interest] Command line option -Xnoprune, what does it do?

[The Researcher]

In my endeavor to understand all of the ANTLR options I am currently working
on -Xnoprune: do not test EBNF block exit branches.

I did search for an answer using Google, the book, the wiki, markmail, and
nothing of detail was found.

Comparing the parser code with and without the option,  it is apparent that
there are extra test for the lookaheads in certain rules. The extra test set
the value for the switch to a nonexistent case. So without the option these
test are pruned from the code.

>From what I can make of this, these extra test work like asserts to help
validate the input by verifying the lookahead against the computed
lookaheads.

Is this correct?

Thanks, Eric