"Field expression is not valid" for Range in LuceneCheck

[SleepyMorpheus]

Hi,
I'm running the following snipped to parse and check a lucene query with the luqum=0.12.1 packet.

from luqum.parser import parser
from luqum.check import LuceneCheck

query = parser.parse('size:[1 TO 10]')
check = LuceneCheck()
print(check.errors(query))

I expect there to be no error as this is a valid query as mentioned in the official documentation of elastic. But instead the LuceneCheck returns the following error:

['field expression is not valid : size:[1 TO 10]']

I therefore suspect that there might be a problem in the check.py module. Can anyone confirm my findings or is this a problem on my end?

[SleepyMorpheus]

After checking out the check.py file it appears to me that the following check fails when parsing a SearchField with a Range as expr:

    SIMPLE_EXPR_FIELDS = (
        tree.Boost, tree.Proximity, tree.Fuzzy, tree.Word, tree.Phrase)

    FIELD_EXPR_FIELDS = tuple(list(SIMPLE_EXPR_FIELDS) + [tree.FieldGroup])

    # .....

    @_check_children
    def check_search_field(self, item, parents):
        if not self._check_field_name(item.name):
            yield "%s is not a valid field name" % item.name
        if not isinstance(item.expr, self.FIELD_EXPR_FIELDS):
            yield "field expression is not valid : %s" % item

In my opinion the tree.Range class should be a member of FIELD_EXPR_FIELDS as it is a valid lucene statement. I have therefore added the class to the list as well as created a dedicated test called test_search_field_range.

Would this work or am I forgetting something here?