anchor.diff:  catchBlock returns [CatchClause clause]
       : CATCH_CLAUSE 
         { $clause = new CatchClause($CATCH_CLAUSE); }
  +      //TODO: correct span calculation
         LPAREN 
         variable 
         { $clause.setVariable($variable.variable); }
  
positive.code:     ;
  
  resource returns [Resource resource]
      : (COMPILER_ANNOTATION|declarationStart|specificationStart) 
        => specifiedVariable
        { $resource = new Resource(null);
          $resource.setVariable($specifiedVariable.variable); }
      //-> ^(RESOURCE specifiedVariable2)
      | expression
        { $resource = new Resource(null);
          $resource.setExpression($expression.expression); }
      //-> ^(RESOURCE expression)
      ;
  
  specifiedVariable returns [Variable variable]
  
negative.code:     : TRY_CLAUSE 
        { $clause = new TryClause($TRY_CLAUSE); }
        (
          resource
          { $clause.setResource($resource.resource); }
        )? 
        block
        { $clause.setBlock($block.block); }
  