Could cases like these be made to work? *Should* cases like these be made to work?

L = [0, 1, 2]
L[::2], *rest = "abcdef"
# ValueError: attempt to assign sequence of size 1 to extended slice of size 2

a, L[::2] = "abc"
# ValueError: too many values to unpack (expected 2)

The list slice knows exactly how many slots need to be filled, so I can't immediately think of any obvious ambiguity. Maybe there are some implementation complications with supporting e.g. generators on the RHS (because RHS must be evaluated before LHS - https://docs.python.org/3/reference/expressions.html#evaluation-order).