[antlr-interest] Duplicate nodes in different forms

[Stefan Bischof]

Hi guys!

I'm writing a source to source translator for a XQuery extension with
ANTLR and was very happy so far. I have created an AST and now want to
write a tree parser rewriting our custom parts of that AST to get a pure
XQuery AST. So I've created a tree parser using rewrite=true and
filter=true.

I have some special cases I couldn't find a solution in the book nor by
trying:

I have a list of variables and want to do two things with it
1. just put them there again
2. for every variable in that list: create some more variables with
different prefixes. 

Simplified example what I want to do:

$i=VAR+ -> 
  $i+ 
  VAR[$i, "_" + $i.text]+ 
  VAR[$i, "?_" + $i.text]+

I've tried different variants of that and couldn't get a valid solution.
I either get an Exception (see example at the end): 
  java.lang.IllegalArgumentException: Can't set single child to a list

or the successfully created Java code doesn't compile because a while
loop with an empty condition is generated:

while ( ) and while ( ! ( ) )

So, any ideas how this could be or should be handled?

best regards,
Stefan Bischof

---------------------------

Simplified example for "Can't set single child to a list":

^(INTEGERS INT+) -> INT+

leads to:

java.lang.IllegalArgumentException: Can't set single child to a list
  at org.antlr.runtime.tree.BaseTree.setChild(BaseTree.java:144)
  at
org.antlr.runtime.tree.BaseTreeAdaptor.setChild(BaseTreeAdaptor.java:225)
  at org.antlr.runtime.tree.TreeVisitor.visit(TreeVisitor.java:36)
  at org.antlr.runtime.tree.TreeVisitor.visit(TreeVisitor.java:33)
  at org.antlr.runtime.tree.TreeRewriter.downup(TreeRewriter.java:89)

(so the rewriting itself actually works, but the list can't be added as
a child to the parent node, i assume)

-- 
Stefan Bischof <stefan.bischof at deri.org>
DERI Galway