Accept overloaded functions as parameter

[sklam]

Feature request

Related to #4602

Request: automatically jitting numba supported functions used in arguments for dispatcher.

For example:

In [1]: from numba import njit

In [2]: import numpy as np

In [3]: @njit
   ...: def foo(fn, arr):
   ...:     return fn(arr)
   ...:

In [4]: @njit
   ...: def call_jitted(arr):
   ...:     return foo(np.sum, arr)
   ...:

In [5]: call_jitted(np.ones(4))  # works fine
Out[5]: 4.0

but the below fails:

In [6]: foo(np.sum, np.ones(4))
...
TypingError: Failed in nopython mode pipeline (step: nopython frontend)
non-precise type pyobject
[1] During: typing of argument at <ipython-input-3-3df5be7cc64d> (3)

File "<ipython-input-3-3df5be7cc64d>", line 3:
def foo(fn, arr):
    return fn(arr)
    ^

This issue suggests that the above behavior inconsistency be fixed.