anchor.diff:  
   %% Method declarations
   method -> function : '$1'.
  +method -> class_method : '$1'.
  +
  +%% Class methods
  +class_method -> def self '.' function_name eol body 'end' : 
  +  #class_method{
  +    line = ?line('$1'), 
  +    name = '$2', 
  +    body = '$4'
  +  }.
  +class_method -> def self '.' function_name args eol body 'end' :
  +  #class_method{
  +    line  = ?line('$1'), 
  +    name  = '$2', 
  +    args  = '$3'#args.args,
  +    block = '$3'#args.block,
  +    body  = '$5'
  +  }.
   
   %% Valid function names
   function_name -> function_identifier : ?identifier_name('$1').
  
positive.code:   class_decl
    methods
    method
    functions
    function
    body
  
negative.code:     block = '$3'#args.block,
      body  = '$5'
    }.
    
  %% Class declarations
  class_decl -> class module_name methods 'end' : 
  