replacing a call atom with a comprehension raises ParsingError

[graingert]

>>> red = redbaron.RedBaron("filter(fn, items).pop()")
>>> red[0]
filter(fn, items).pop()
>>> del red[0][1]
>>> red
0   filter.pop()

>>> red[0][0] = "[x for x in items if fn(x)]"
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/redacted/.virtualenvs/redbaron/local/lib/python/site-packages/redbaron/base_nodes.py", line 736, in __setitem__
    self.value[key] = value
  File "/home/redacted/.virtualenvs/redbaron/local/lib/python/site-packages/redbaron/base_nodes.py", line 1469, in __setitem__
    on_attribute=self.on_attribute)
  File "/home/redacted/.virtualenvs/redbaron/local/lib/python/site-packages/redbaron/base_nodes.py", line 1672, in _convert_input_to_node_object
    return self.node_list.parent._convert_input_to_node_object_list(value, parent, on_attribute).filtered()[-1]
  File "/home/redacted/.virtualenvs/redbaron/local/lib/python/site-packages/redbaron/base_nodes.py", line 188, in _convert_input_to_node_object_list
    return self._string_to_node_list(value, parent=parent, on_attribute=on_attribute)
  File "/home/redacted/.virtualenvs/redbaron/local/lib/python/site-packages/redbaron/nodes.py", line 98, in _string_to_node_list
    return NodeList.from_fst(baron.parse("(%s)" % string)[0]["value"]["value"], parent=parent, on_attribute=on_attribute)
  File "/home/redacted/.virtualenvs/redbaron/local/lib/python/site-packages/baron/baron.py", line 57, in parse
    to_return = _parse(tokens, print_function)
  File "/home/redacted/.virtualenvs/redbaron/local/lib/python/site-packages/baron/baron.py", line 24, in _parse
    return parser(tokens)
  File "/home/redacted/.virtualenvs/redbaron/local/lib/python/site-packages/baron/grammator.py", line 828, in parse
    return parser.parse(iter(tokens))
  File "/home/redacted/.virtualenvs/redbaron/local/lib/python/site-packages/baron/parser.py", line 167, in parse
    raise ParsingError(debug_output)
baron.parser.ParsingError: Error, got an unexpected token FOR here:

   1 (a[x for <---- here

The token FOR should be one of those: COLON, COMMA, RIGHT_SQUARE_BRACKET

Baron has failed to parse this input. If this is valid python code (and by that I mean that the python binary successfully parse this code without any syntax error) (also consider that python does not yet parse python 3 code integrally) it would be kind if you can extract a snippet of your code that make Baron fails and open a bug here: https://github.com/PyCQA/baron/issues

Sorry for the inconvenience.