How to convert from antlr v2 to v3 grammar?

Question

I have the below grammar in v2 of ANTLR, I need help to convert it to v3

expression
: ( simpleLookup
  | lookup
  )
  ( x:LSQRBRACKET^ {#x.setType(ATTRIBUTES);} attributesExpr RSQRBRACKET! )?
;enter code here

Actually I tried below but not sure if it will be same or not and also getting the below error while trying to build the parser

expression
: ( simpleLookup
  | lookup
  )
  (x=LSQRBRACKET b=attributesExpr RSQRBRACKET )?) -> ^(ATTRIBUTES[$x] $a $b)?
;

and getting below error

expecting SEMI, found '->'
unexpected token: $
unexpected token: $
unexpected token: )

How to convert "!" in v3 from v2?

Kindly help me with your expertise.....

One more question I have is how can I write tree parser in v3 at grammar level, like in v2 we used to write in the below format

class CustomTreeParser extends TreeParser;

Answer 1

Try something like this:

grammar YourGrammarName;

options {
  output=AST;
}

tokens {
  ATTRIBUTES;
}

// ...

expression
 : ( simpleLookup
   | lookup
   )
   ( x=LSQRBRACKET^ {$x.setType(ATTRIBUTES);} attributesExpr RSQRBRACKET! )?
 ;

// ...

How to convert "!" in v3 from v2?

The inline ! operator, which excludes certain rules/tokens from an AST, is unchanged in v3.

One more question I have is how can I write tree parser in v3 at grammar level, like in v2 ...

Like this:

options {
  output=AST;
}