A few issues with the mixing arrays and Python scalars section that came up from testing:

• The matmul operator (@) does not (and should not) support scalar types, so it should be excluded.
• Should boolean arrays be required to work with arithmetic operators. NumPy gives errors in some cases, for example:

>>> import numpy as np
>>> np.array(False) - False
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: numpy boolean subtract, the `-` operator, is not supported, use the bitwise_xor, the `^` operator, or the logical_xor function instead. 

• How should casting work? For example, int8 array + large Python int. Should it cast the int, or give an error. Or should this be unspecified.
• The above question also applies for Python float -> float32 casting, which is implicitly supported by the text that is currently there, but is unsafe in general (is there a "safe" variant of float64 -> float32, or is it always unsafe? Either way, this would be value based casting, which I thought we were trying to avoid).