lastIndexOf with a needle of the element type read every non-hole index
as the element type. An undefined or foreign element written through a
dynamic view (or a hole that toSorted turned into undefined) has no
element-typed payload, so the read aborted with "array index N is
undefined". The search now reads an index only when it holds a value,
and skips undefined and foreign elements, as Node's strict equality
does for a string or number needle.
Chris Tate
a538ff42f0