numpy ediff1d tests have TypeError in `to_end` (numpy 1.19)

• I have tried using the latest released version of Numba: 0.50.1
• I have included below a minimal working reproducer

I’m seeing some errors in tests, building and running numba 0.50.1 on Debian unstable (python 3.8.3, numpy 1.19.0).

I’ll focus on runtime test failures here (running tests on installed system, not build-time tests). Runtime tests are triggered with MPLBACKEND=Agg python3.8 -Wd -m numba.runtests -v -m but the failing test can be run manually:

python3 -m pytest -k "test_ediff1d_edge_cases" /usr/lib/python3/dist-packages/numba/tests/test_np_functions.py -v

The error summary is

======================================================================
ERROR: test_ediff1d_edge_cases (numba.tests.test_np_functions.TestNPFunctions)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/numba/tests/test_np_functions.py", line 2045, in test_ediff1d_edge_cases
    _check_raises_type_error(params, 'to_begin')
  File "/usr/lib/python3/dist-packages/numba/tests/test_np_functions.py", line 2012, in _check_raises_type_error
    pyfunc(**params)
  File "/usr/lib/python3/dist-packages/numba/tests/test_np_functions.py", line 229, in ediff1d
    return np.ediff1d(ary, to_end, to_begin)
  File "<__array_function__ internals>", line 5, in ediff1d
  File "/usr/lib/python3/dist-packages/numpy/lib/arraysetops.py", line 107, in ediff1d
    raise TypeError("dtype of `to_end` must be compatible "
TypeError: dtype of `to_end` must be compatible with input `ary` under the `same_kind` rule.

This is with numpy 1.19 which has only just been released, so I’m wondering if it’s an adjustment which numba needs to make in test_ediff1d_edge_cases to work with the new numpy.

[stuartarchibald]

I just tried writing the patch to make this work and discovered https://github.com/numpy/numpy/pull/17457

[drew-parsons]

Confirmed, still failing with numpy 1.91.1.