`new Set([a, b])`, where `a` and `b` are reads of the same InlineArray
field, gave a Set of size 2 where Node gives size 1: each read may give
another array, and the source proof checked Set elements only when they
were added with `add`. It now reports SC7009 when the seed of a new Set,
or the values of a Map that become a Set (`new Set(map.values())`), may
hold a field's array.
Chris Tate
c2ebd0d4a4