anchor.diff:  
   
   stmt:
  -        (declaration_multi)
  +    SEMICOLON ->
  +    |   (declaration_multi)
       |   (assignment_expr)
       |   (expr_stmt)         SEMICOLON -> expr_stmt
       |   (if_stmt)
  
positive.code: // only allow function calls as non-assignment statements
  expr_stmt: e=function_call -> ^( EXPR_STMT $e )
      ;
      
  update_stmt: v=ID LT cmd=ID GT MUTATE expr SEMICOLON
  			-> ^( UPDATE $cmd $v expr)
  	;
  
negative.code: bool_lit: TRUE | FALSE
      ;
  
  function_call:
               priority? f=ID a=expr_argument_list -> ^( CALL_FUNCTION $f $a priority?)
      ;
  
  