Match results record their metadata lazily. The results of one exec or
matchAll call share a source (the subject and the regex), and each
result keeps its start index. index, input and a null-prototype groups
object are built when a result is converted to a dynamic value; .index
and .input on a match slice read the source directly.
matchAll rows are allocated inline, like exec results. A drain whose
rows are read only through their elements, .length, the .groups
projection and the companion index uses matchAllCaptures or
matchAllCapturesInto, whose rows carry no metadata.
Chris Tate
526415a91c