Declaring vectorized ufunc with numba, signature error: 'Float' instance not allowed

Question

I'm trying to write a function that can be vectorized by numba to act as a ufunc on a set of arrays:

from numba import float32, float64, vectorize

@vectorize([float32, float32, float32, float32(float32, float32, float32, float32, float32, float32, float32, numba.float32),
            float64, float64, float64, float64(float64, float64, float64, float64, float64, float64, float64, numba.float64)])
def _cafec_coeff_ufunc(ET_bar,
                       PET_bar,
                       R_bar,
                       PR_bar,
                       L_bar,
                       PL_bar,
                       RO_bar,
                       PRO_bar):
            
    # calculate alpha
    if PET_bar == 0:
        if ET_bar == 0:
            alpha = 1
        else:
            alpha = 0
    else:
        alpha = ET_bar / PET_bar

    # calculate beta
    if PR_bar == 0:
        if R_bar == 0:
            beta = 1
        else:
            beta = 0
    else:
        beta = R_bar / PR_bar

    # calculate gamma
    if PRO_bar == 0:
        if RO_bar == 0:
            gamma = 1
        else:
            gamma = 0
    else:
        gamma = RO_bar / PRO_bar

    # calculate delta
    if PL_bar == 0:
        if L_bar == 0:
            delta = 1
        else:
            delta = 0
    else:
        delta = L_bar / PL_bar

    return alpha, beta, gamma, delta

I call the above function in another function, passing the eight arrays it needs as arguments. My expectation is that this function will be applied in a broadcasting fashion, as if a 1-D loop for each element i (assuming all input arrays are equal size) with the ufunc getting scalars from each array at the i-th index as its arguments, finally returning with four arrays with corresponding values in the i-th locations of the output arrays (result of the ufunc broadcast reduced into output arrays).

alpha, beta, gamma, delta = _cafec_coeff_ufunc(ETbar, PETbar, Rbar, PRbar, Lbar, PLbar, RObar, PRObar)

When I run the code above as part of a unit test for the calling method I get the following errors in console:

  File "C:\home\git\indices_python\palmer.py", line 342, in <module>
    numba.float64, numba.float64, numba.float64, numba.float64(numba.float64, numba.float64, numba.float64, numba.float64, numba.float64, numba.float64, numba.float64, numba.float64)])
  File "C:\Anaconda3\lib\site-packages\numba\npyufunc\decorators.py", line 120, in wrap
    vec.add(sig)
  File "C:\Anaconda3\lib\site-packages\numba\npyufunc\dufunc.py", line 139, in add
    args, return_type = sigutils.normalize_signature(sig)
  File "C:\Anaconda3\lib\site-packages\numba\sigutils.py", line 35, in normalize_signature
    % (sig.__class__.__name__,))
TypeError: invalid signature: 'Float' instance not allowed

I can modify the signature by adding quotes around the signature itself in order to turn it into a string. and when I do this the error now becomes this:

  File "C:\home\git\indices_github\palmer.py", line 346, in <module>
    @numba.vectorize(['f8,f8,f8,f8(f8,f8,f8,f8,f8,f8,f8,f8)'])
  File "C:\home\Anaconda3\lib\site-packages\numba\npyufunc\decorators.py", line 120, in wrap
    vec.add(sig)
  File "C:\home\Anaconda3\lib\site-packages\numba\npyufunc\dufunc.py", line 139, in add
    args, return_type = sigutils.normalize_signature(sig)
  File "C:\home\Anaconda3\lib\site-packages\numba\sigutils.py", line 45, in normalize_signature
    check_type(ty)
  File "C:\home\Anaconda3\lib\site-packages\numba\sigutils.py", line 40, in check_type
    "got %r" % (ty,))
TypeError: invalid signature: expected a type instance, got (float64, float64, float64, float64, float64, float64, float64, float64) -> float64

What am I doing wrong here?