A report-location override for a Mutare.Mutator.Mutation (see its :attribution field).

Names the clause a whole-node rewrite should be reported at, independent of the node spliced into the metamutant. original is the clause before the change (its range locates the site and renders the diff's "before"); mutated is the clause after — a replacement node for at/2, or the atom :drop for at_drop/1 (a removed clause, reported as a delete). Built only through Mutare.Mutator.Mutation.at/2 and Mutare.Mutator.Mutation.at_drop/1.