This code

    match range(42):
        case [x, *w, y]:
            z = 0

sets w to a list with 40 items : the length of the subject, minus the number of non-star subpatterns.

But this code (adapted from test_patma_186) enters an infinite loop

    import collections.abc

    class Seq(collections.abc.Sequence):
        def __getitem__(self, i):
            print('get item', i)
            return i
        def __len__(self):
            return 42

    match Seq():
        case [x, *w, y]:
            z = 0

__getitem__ gets called forever, instead of stopping when the expected number of items in w is reached.