[pypy-dev] undefined symbol in ParserGenerator

[Terrence Cole]

On Sun, 2010-04-18 at 21:13 -0500, Benjamin Peterson wrote:
> 2010/4/18 Terrence Cole <list-sink at trainedmonkeystudios.org>:
> > In pypy/interpreter/pyparser/metaparser.py in get_first on line 233:
> > the name 'symbol' is undefined.
> >
> > I hit this when parsing the python grammar from the 3.1.2 release.
> > Oddly, the current py3k trunk does not hit this.  I'll dig more to see
> > if I can figure out why the grammar is causing this, but the error
> > handling here is obviously bogus, so I thought I'd go ahead and report
> > it.
> 
> This is because the 3.1.2 grammar is incorrect, and CPython's parser
> generator accepts it. See
> http://svn.python.org/view?view=rev&revision=75080. It's safe to use
> the py3k branch one, since it hasn't changed.

Awesome!  You've just saved me a lot of difficult, pointless work.

Below is the svn diff I ended up with when testing.

-Terrence


Index: pypy/interpreter/pyparser/metaparser.py
===================================================================
--- pypy/interpreter/pyparser/metaparser.py	(revision 73878)
+++ pypy/interpreter/pyparser/metaparser.py	(working copy)
@@ -230,7 +230,8 @@
         for label, their_first in overlap_check.iteritems():
             for sub_label in their_first:
                 if sub_label in inverse:
-                    raise PgenError("ambiguous symbol %s" % (symbol,))
+                    raise PgenError("ambiguous symbol at '%s': %s" % (label, 
+                                    sub_label))
                 inverse[sub_label] = label
         self.first[name] = all_labels
         return all_labels