Keyword-only arguments and default arguments always do the wrong thing when combined

Reporting a bug

Default arguments never work with keyword-only arguments:

import numba 
@numba.njit
def foo(a, b = 1, *, c = 10):
    return a + b + c

foo(1, 2) 
# gives: 4
# expected: 13

foo(1) 
# gives: TypeError: not enough arguments: expected at least 2, got 1
# expected: 12

@numba.njit
def bar(a, b = 1, *, c):
    return a + b + c

bar(1, c=2)
# gives: TypeError: missing argument 'b'
# expected: 4

bar(1, 2)
# gives: 4
# expected: TypeError: missing argument 'c'

@numba.njit
def baz(a, b, *, c = 1):
    return a + b + c

baz(1, 1)
# gives: TypeError: not enough arguments: expected 3, got 2
# expected: 3

• I am 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 below a minimal working reproducer (if you are unsure how to write one see http://matthewrocklin.com/blog/work/2018/02/28/minimal-bug-reports).

[stuartarchibald]

I think the immediate task here is to just outright ban situations that produce nonsense, fixes can then be performed in the relative safety of knowing that there’s nothing out there half working.

[eric-wieser]

Agreed, it’s way more important to stop code silently producing wrong results than it is to add support for a wider range of calling conventions - so starting with the extensive rewrite is a bad idea.