[antlr-interest] start/stop tokens for subrules?

[David Holroyd]

Knowing the start/stop tokens for an AST node is very important to my
application.

ANTLRv3 generated parsers don't currently seem to set start/stop tokens
for the root AST nodes created by subrules.  Only the final result of the
rule as a whole gets these values defined.  e.g. in,

  identifier
   :  (  qualifiedIdent -> qualifiedIdent
      )
      (  options{greedy=true;}
      :   d=DOT qualifiedIdent
          -> ^(PROPERTY_OR_IDENTIFIER[$d] $identifier qualifiedIdent)
      )*
      -> ^(IDENTIFIER $identifier)

the generated PROPERTY_OR_IDENTIFIER node which is created as the root
of the subtree does not get the adaptor.setTokenBoundaries() love.


Admittedly, even if the subrule's root *did* get these values defined,
they would be 'wrong' for the tree I want to construct (I want the
startToken to reflect the start of the first child, not LT(1) at the
start of the subrule).

I therefore end up creating auxiliary rules like this:

  identifier 
   :  (  qualifiedIdent -> qualifiedIdent
      )
      (  options{greedy=true;}
      :  poi=propOrIdent[root_0, retval.start] -> $poi
      )*
      -> ^(IDENTIFIER $identifier)
    ;

  propOrIdent[Tree identPrimary, Token startToken]
   :  { retval.start = startToken; }
      d=DOT propId=qualifiedIdent
      -> ^(PROPERTY_OR_IDENTIFIER[$d] {$identPrimary} $propId)
    ;

and while this seems to work, I feel dirty.


Is there a better way?


ta,
dave

-- 
http://david.holroyd.me.uk/