[antlr-interest] Custom AST nodes - attempt #2

[Bill Andersen]

Hi Folks,

This is my second attempt at asking this question.  Hopefully it is clear.  If not, please let me know.

I'm interested in using a custom AST node class to carry type information.

I do not want to build a custom TreeAdaptor to determine node type based on token id because only a few AST nodes will have to be of the custom class.

Here's a sample production from the tree generating grammar.

rule
	: ... match something ...
	-> ^(NODE<CustomType>[param] ...)
	;

So far so good.  I know how to do this.  

Let's say CustomType looks like this

class CustomType extends CommonTree {
	public T param;
	public CustomType(int ttype, T param) { ... }
	public T getParam() { ... }
	...
}

Now I have another grammar that consumes ASTs from the first grammar.  I want to do this:

rule
	: ^(NODE ...)
	  { ... do something with this information ... }
	;

So, what syntax do I need in the action to get a T-typed param value from this node?

Any help appreciated