anchor.diff:  
   if_op -> 'if'   : '$1'.
   if_op -> unless : '$1'.
  +
  +else_clause -> else inline_statements eol : {else_clause, line('$1'), '$2'}.
  +else_clause -> else eol indent statements dedent : {else_clause, line('$1'), '$4'}.
   
   %% For loops
   for_expr -> for match_expr in expr eol indent statements dedent : {for, line('$1'), '$2', '$4', '$7'}.
  
positive.code:   case_expr
    case_clauses
    case_clause
    else_clause
    if_expr
    inline_if_expr
    if_op
    for_expr
    try_expr
  
negative.code: 
  %% Case expressions
  case_expr -> 'case' expr eol indent case_clauses dedent : {'case', line('$1'), '$2', '$5'}.
  
  case_clauses -> case_clause case_clauses : ['$1'|'$2'].
  case_clauses -> case_clause : ['$1'].
  
  case_clause -> expr ':' eol indent statements dedent : {clause, line('$2'), '$1', '$5'}.
  
  %% If expressions
  if_expr -> if_op expr eol indent statements dedent : if_forms({'$1', '$2', '$5'}).
  