[antlr-interest] De-emphasizing tree grammars?

[George S. Cowan]

Ter,
 
I am worried about my use extensive use of tree grammars in my project.
 
On the TODO List page
http://www.antlr.org/wiki/display/~admin/TODO+list?focusedCommentId=27656324
#comment-27656324
 
Ruben Laguna says:
> Can I ask why the "no ast output from tree grammar" bullet? Is there
something fundamentally wrong with generating ast from tree grammars?
 
then
 
Terence Parr says:
> Hi Ruben, turns out I'm de-emphasizing tree grammars and it's a rarely
used feature and hard to implement.
 
That "de-emphasizing tree grammars" is really scary. The TODO list still
contains some items about tree grammars, TreeFilter, and TreeRewriter so I'm
not clear. Also, in the Language Implementation Patterns book, the tree
grammar examples Reduce.g and Simplify.g use output=AST. You seemed very
excited about that capability not so long ago. 
 
Will I still be able to do extensive transformations of trees in ANTLR 4?
What approach should I plan on for multiple complicated outputs from a
single input?
 
George