anchor.diff:      | pid
       | port
       | reference
  +    | none
       | {typedef, module(), atom()}
       | atom
       | float
  
positive.code:     UnknownTypes;
  find_unknown_types_helper(reference, _TypeInfo, UnknownTypes) ->
      UnknownTypes;
  find_unknown_types_helper(nil, _TypeInfo, UnknownTypes) ->
      UnknownTypes;
  find_unknown_types_helper(node, _TypeInfo, UnknownTypes) ->
  
negative.code:     nil;
  parse_type({type, _Line, node, []}, _Module) ->
      node;
  parse_type({type, _Line, none, []}, _Module) ->
      none;
  parse_type({type, _Line, reference, []}, _Module) ->
      reference;
  parse_type({type, _Line, term, []}, _Module) ->
  