On Fri, Dec 28, 2007 at 07:11:23PM -0800, chromatic wrote:
> On Friday 28 December 2007 16:16:55 Patrick R.Michaud wrote:
>
> > Whenever a PAST::Op node gets a non-PAST child, PCT currently
> > throws a cryptic exception message like:
> >
> > Method 'named' not found for invocant of class 'Perl6::Grammar'
> >
> > A better exception message would be something like:
> >
> > Perl6::Grammar ("2") child of PAST::Op cannot be converted to POST.
>
> How does this node "get" a non-PAST child? Is there a single point at which
> you add a child to a PAST::Op node? (I'm pretty sure I know the answer, but
> I'm not entirely sure.)
Yes, however, adding a non-PAST child to a PAST node isn't necessarily
an error. The exception should probably be thrown at the point where
PAST::Compiler attempts to convert the (non-PAST) child to POST, not
at the point where the child is added to a PAST::Node.
The fix is easy enough to do -- just a small modification to the
'post_children' method of PAST::Compiler (src/PAST/Compiler.pir)
to throw an exception when it sees a non-PAST child. I simply entered
the ticket as a placeholder so it's not forgotten.
Or, we could perform the check at the point of the 'push' or 'unshift'
method that adds nodes to a PAST child, with an optional :force
flag to allow non-PAST children to be added.
As to how it's possible for a non-PAST node to appear as a child,
it comes up when a transformation method inadvertently adds a match
object or constant to a PAST::Node instead of the ast (PAST)
representation of the match object or constant.
Thanks!
Pm
