Tuple-literal mutation: collapse a non-empty tuple literal to the empty tuple {}. The tuple sibling of Mutare.Mutators.List/MapLiteral — it asks "does anything destructure or match this tuple?". A {:ok, value} that is built but never pattern-matched (or whose shape no test pins down) lets {} survive; anywhere the shape is used, the mutant is killed.
Two AST shapes, because Elixir represents a 2-element tuple specially: a literal pair {a, b} parses as {:__block__, _, [{a, b}]} (the value is a raw 2-tuple), while {}, {a}, and {a, b, c, …} parse as {:{}, _, elements}. Both non-empty shapes collapse to {:{}, [], []} ({}); the empty tuple is left alone.
A tuple in a pattern is left alone, so a match like {:ok, v} = … is not corrupted.