Math.max, Math.min and Math.hypot over a spread, and the default sort,
convert foreign elements with user code. As in Node, the elements are
taken first, each foreign value retained, so a conversion that changes
the array changes neither the count nor the values the operation sees,
and no slot read before the conversion is released under it. join and
the numeric element read hold the value they convert, and join reads the
length once and stops at a throw.
toSorted of an array with foreign elements now builds a copy of the
full length and reads its holes as undefined, as for other arrays.
Chris Tate
116d163e2c