[antlr-interest] How to draw information from a returned AST

[Priya]

Hello all,
         I'm a newbie to antlr. I am currently working on an ANTLR-C++
compiler that parses a subset of C syntax.
Shown below is a portion of my parser grammar.

function_arg:
( !(COMMA!)? t1:type ( n:Name (l:LSQB d:Decimal_Number RSQB!)?)?);

type :(
    d1:"char"^  COLON! de:Decimal_Number  {#type=#(#d1,#(de));  }

    | d:"char"^ { #type=#(#d,#[Nint,"4"]);}

    | i2:"int"^ COLON! de1:Decimal_Number {#type=#(#i2,#(de1));}

    | i1:"int"^ {#type=#(#i1,#[Nint,"8"]);}

    | "void"!  { #type=#(#[Nint,"int"],#[Nint,"0"]);})
    ) ;

ex:
(int:3 a,int:4 b[5])
int:3 is the notation i'm using to declare 3 bit integer.
for int:3 ,type will return an AST like
int
|
|
3

to the call from function_arg rule. In function_arg rule ,how can I
operate on the returned tree to record the datatype and bit precision
information ?

Thanks in advance
Priya