[antlr-interest] empty tree assertion rule

[Bryan Ewbank]

> > So I came up with the idea to write a tree parser rule to ensure
> > that given input tree is empty:
> >
> > 001 nullp
> > 002 {
> > 003    if( #nullp != null ) {
> > 004     System.err.println("error: tree not empty!");
> > 005     System.exit(1);
> > 006    else {
> > 007     return;
> > 008    }
> > 009 }
> > 010    : #(INT INT)
> > 011    ;

This is marvelous!  I will be using this to ensure total tree match, instead
of
partial.  What I have is a production called <and_nothing_else> that looks
like
this:

    251 and_nothing_else
    252     :
    253         ( node:.
    254             {
    255                 cerr << "spurious node of type "
    256                     << node->getType()
    257                     << " ("
    258                     << getTokenName(node->getType())
    259                     << ") w/ text='"
    260                     << node->getText()
    261                     << "' detected in tree" << endl;
    262             }
    263         )*
    264     ;

Now I just need to get the parent linkages, and I'll be able to show the
context in which the problem occurs.

Tree audits, here I come.  In conjunction with adding a wildcard production
to the topmost rule (and ignoring the ambiguity) to detect unimplemented
node types, I think I can do this pretty cleanly.

Thanks again!



 
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