[antlr-interest] adding node to AST

[Martin Probst]

Hi,

> I need to check that the SubscriptionManager token *does* end with :INT, and add it as a node.

So why is the (":" INT) block optional then? Better leave syntax
analysis and errors to ANTLR.

> subscriptionManager!
> { boolean oldSubMgr = true; }
> 	:	x:"SubscriptionManager" (":" sm:INT { oldSubMgr = false; } )?
> 	{ 
> 	  #subscriptionManager = #x; 
> 		
> 	  if(oldSubMgr) {		
> 		throw new Exception("bad format");
> 	  }
> 	}
> 		LBRACE!
> 		RBRACE!
> 	;

Well, with the "!" no AST construction takes place in the rule, so the
ASTs for ":" and "sm:INT" are not attached anywhere. If you want them,
you have to add them manually in this case:
> x:"SubscriptionManager" col:":" sm:INT
> { #subscriptionManager = #(#x, #col, #sm); }

or, preferrably without action code 
(and with construction on, e.g. no "!"):
> x:"SubscriptionManager"^ col:":" sm:INT

This will give you
    x
  /   \
 col  sm

(Do you really need the ":"?)

> I previously tried to add the node in the usual way, using '^' (with the '!' removed from the rule
> name and the line "#subscriptionManager = #x;" omitted).

The above should work.

> I tried all of the following, but no luck:
> x^:"SubscriptionManager" (":" sm:INT { oldSubMgr = false; } )?
> x:"SubscriptionManager" (":" sm:INT { oldSubMgr = false; } )?^
> x:("SubscriptionManager" (":" sm:INT { oldSubMgr = false; } )?)^

I think those are not syntactically correct in ANTLR, are they? There is
a section in the manual about tree construction, though it's quite
hidden.

Martin