python-lark fails to build with Python 3.14.0a1.

+ /usr/bin/python3 -m tests
ERROR: test_partial (tests.test_trees.TestTrees.test_partial)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/builddir/build/BUILD/python-lark-1.2.2-build/lark-1.2.2/lark/visitors.py", line 122, in _call_userfunc
    return f.visit_wrapper(f, tree.data, children, tree.meta)
           ~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/builddir/build/BUILD/python-lark-1.2.2-build/lark-1.2.2/lark/visitors.py", line 504, in _vargs_inline
    return f(*children)
  File "/builddir/build/BUILD/python-lark-1.2.2-build/lark-1.2.2/lark/visitors.py", line 482, in __call__
    return self.base_func(*args, **kwargs)
           ~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
TypeError: TestTrees.test_partial.<locals>.test() got multiple values for argument 'postfix'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/builddir/build/BUILD/python-lark-1.2.2-build/lark-1.2.2/tests/test_trees.py", line 361, in test_partial
    res = T().transform(tree)
  File "/builddir/build/BUILD/python-lark-1.2.2-build/lark-1.2.2/lark/visitors.py", line 161, in transform
    res = list(self._transform_children([tree]))
  File "/builddir/build/BUILD/python-lark-1.2.2-build/lark-1.2.2/lark/visitors.py", line 146, in _transform_children
    res = self._transform_tree(c)
  File "/builddir/build/BUILD/python-lark-1.2.2-build/lark-1.2.2/lark/visitors.py", line 156, in _transform_tree
    children = list(self._transform_children(tree.children))
  File "/builddir/build/BUILD/python-lark-1.2.2-build/lark-1.2.2/lark/visitors.py", line 146, in _transform_children
    res = self._transform_tree(c)
  File "/builddir/build/BUILD/python-lark-1.2.2-build/lark-1.2.2/lark/visitors.py", line 157, in _transform_tree
    return self._call_userfunc(tree, children)
           ~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^
  File "/builddir/build/BUILD/python-lark-1.2.2-build/lark-1.2.2/lark/visitors.py", line 128, in _call_userfunc
    raise VisitError(tree.data, tree, e)
lark.exceptions.VisitError: Error trying to process rule "a":

TestTrees.test_partial.<locals>.test() got multiple values for argument 'postfix'

======================================================================
ERROR: test_smart_decorator (tests.test_trees.TestTrees.test_smart_decorator)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/builddir/build/BUILD/python-lark-1.2.2-build/lark-1.2.2/lark/visitors.py", line 122, in _call_userfunc
    return f.visit_wrapper(f, tree.data, children, tree.meta)
           ~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/builddir/build/BUILD/python-lark-1.2.2-build/lark-1.2.2/lark/visitors.py", line 504, in _vargs_inline
    return f(*children)
  File "/builddir/build/BUILD/python-lark-1.2.2-build/lark-1.2.2/lark/visitors.py", line 482, in __call__
    return self.base_func(*args, **kwargs)
           ~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
TypeError: reduce() arg 2 must support iteration

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/builddir/build/BUILD/python-lark-1.2.2-build/lark-1.2.2/tests/test_trees.py", line 293, in test_smart_decorator
    result = test_instance.transform(Tree(method_name, children))
  File "/builddir/build/BUILD/python-lark-1.2.2-build/lark-1.2.2/lark/visitors.py", line 161, in transform
    res = list(self._transform_children([tree]))
  File "/builddir/build/BUILD/python-lark-1.2.2-build/lark-1.2.2/lark/visitors.py", line 146, in _transform_children
    res = self._transform_tree(c)
  File "/builddir/build/BUILD/python-lark-1.2.2-build/lark-1.2.2/lark/visitors.py", line 157, in _transform_tree
    return self._call_userfunc(tree, children)
           ~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^
  File "/builddir/build/BUILD/python-lark-1.2.2-build/lark-1.2.2/lark/visitors.py", line 128, in _call_userfunc
    raise VisitError(tree.data, tree, e)
lark.exceptions.VisitError: Error trying to process rule "partial_reduce_mul":

reduce() arg 2 must support iteration

----------------------------------------------------------------------
Ran 1115 tests in 4.794s

FAILED (errors=2, skipped=131)

https://docs.python.org/3.14/whatsnew/3.14.html

For the build logs, see:
https://copr-be.cloud.fedoraproject.org/results/@python/python3.14/fedora-rawhide-x86_64/08198407-python-lark/

For all our attempts to build python-lark with Python 3.14, see:
https://copr.fedorainfracloud.org/coprs/g/python/python3.14/package/python-lark/

Testing and mass rebuild of packages is happening in copr.
You can follow these instructions to test locally in mock if your package builds with Python 3.14:
https://copr.fedorainfracloud.org/coprs/g/python/python3.14/

Let us know here if you have any questions.

Python 3.14 is planned to be included in Fedora 43.
To make that update smoother, we're building Fedora packages with all pre-releases of Python 3.14.
A build failure prevents us from testing all dependent packages (transitive [Build]Requires),
so if this package is required a lot, it's important for us to get it fixed soon.

We'd appreciate help from the people who know this package best,
but if you don't want to work on this now, let us know so we can try to work around it on our side.