anchor.diff:  call_args_parens -> open_paren ')' : [].
   call_args_parens -> open_paren call_args close_paren : '$2'.
   
  -call_args_parens_many -> open_paren kw_base close_paren : ['$2'].
  -call_args_parens_many -> open_paren expr ',' call_args close_paren : ['$2'|'$4'].
  +call_args_parens_not_one -> open_paren ')' : [].
  +call_args_parens_not_one -> open_paren kw_base close_paren : ['$2'].
  +call_args_parens_not_one -> open_paren expr ',' call_args close_paren : ['$2'|'$4'].
   
   % KV
   
  
positive.code:   open_curly close_curly
    open_bit close_bit
    base_comma_expr comma_expr optional_comma_expr matched_comma_expr
    call_args call_args_parens call_args_parens_many call_args_no_parens parens_call
    stab_expr stab_expr_list
    kw_eol kw_expr kw_comma kw_base
    matched_kw_expr matched_kw_comma matched_kw_base
  
negative.code: 
  % Note expressions are on reverse order
  expr_list -> expr : ['$1'].
  expr_list -> open_paren ')' : [nil].
  expr_list -> expr_list eol expr : ['$3'|'$1'].
  
  expr -> matched_expr : '$1'.
  