Cannot create datetime inside njit

[astrojuanlu]

Reporting a bug

• I have tried using the latest released version of Numba (most recent is
  visible in the change log (https://github.com/numba/numba/blob/master/CHANGE_LOG).
• I have included a self contained code sample to reproduce the problem.
  i.e. it's possible to run as 'python bug.py'.

By reading in https://numba.readthedocs.io/en/stable/reference/numpysupported.html#scalar-types that Numba supports NumPy datetimes and timestamps of any unit, I tried creating one inside a @njitted function, but it failed:

$ cat dt_test.py 
import numpy as np
from numba import njit


@njit
def f(dt64):
    return dt64

print(f(np.datetime64(100, "D")))  # Works


@njit
def d():
    return np.datetime64(100, "D")

print(d())  # Fails
$ python dt_test.py 
1970-04-11
Traceback (most recent call last):
  File "dt_test.py", line 16, in <module>
    print(d())  # Fails
  File "/home/juanlu/.pyenv/versions/sgp38/lib/python3.8/site-packages/numba/core/dispatcher.py", line 414, in _compile_for_args
    error_rewrite(e, 'typing')
  File "/home/juanlu/.pyenv/versions/sgp38/lib/python3.8/site-packages/numba/core/dispatcher.py", line 357, in error_rewrite
    raise e.with_traceback(None)
numba.core.errors.TypingError: Failed in nopython mode pipeline (step: nopython frontend)
No implementation of function Function(datetime64[]) found for signature:
 
 >>> <unknown function>(Literal[int](100), Literal[str](D))
 
There are 2 candidate implementations:
 - Of which 2 did not match due to:
 Overload in function 'make_callable_template.<locals>.generic': File: numba/core/typing/templates.py: Line 170.
   With argument(s): '(int64, unicode_type)':
  Rejected as the implementation raised a specific error:
    TypeError: typer() takes 1 positional argument but 2 were given
  raised from /home/juanlu/.pyenv/versions/sgp38/lib/python3.8/site-packages/numba/core/typing/templates.py:399

During: resolving callee type: class(datetime64[])
During: typing of call at dt_test.py (14)


File "dt_test.py", line 14:
def d():
    return np.datetime64(100, "D")
    ^

Tested on Python 3.8, Linux, latest numba installed from pip using manylinux wheels.

[stuartarchibald]

Thanks for the report. From memory, creation of datetime types inside JIT code regions is not supported yet, however most operations should work.