Raise a TypeError when slice-setting a Multirange with a non-iterable value

[dlax]

The type declaration is:

def __setitem__(index: slice, value: Iterable[Range[T]]) -> None:
    ...

so passing a non-iterable value should not be allowed. However, the
method implementation makes a special-case for non-iterable values with
a slice.

In accordance with MutableSequence behavior, e.g.:

  >>> x = [1, 2, 3]
  >>> x[1:3] = 0
  Traceback (most recent call last):
    File "<stdin>", line 1, in <module>
  TypeError: can only assign an iterable

it seems more correct to raise a TypeError.

(Alternatively, we could change the type declaration of MultiRange__setitem__() but that would make it incompatible with MutableSequence, which seems wrong.)

[dvarrazzo]

Ahhhh... I was sure I had tested it and that it was the expected behaviour...

>>> L = list('danie')
>>> L
['d', 'a', 'n', 'i', 'e']

>>> L[2:4] = 'x'
>>> L
['d', 'a', 'x', 'e']

except that a string is iterable... 😅