@spec build(module(), term(), String.t(), map(), non_neg_integer()) :: map()

Builds a single mutation map. The description is prefixed with the mutator's name/0; the file falls back to "unknown" when the context omits it.

@spec clause_deletions(
  module(),
  list(),
  [non_neg_integer()],
  (list() -> Macro.t()),
  map(),
  non_neg_integer()
) :: [map()]

Produces one "delete clause" mutation per index in deletable_positions.

items is the full list a clause is removed from; rebuild turns a reduced list back into the enclosing AST node. Labels are 1-based over the deletable positions (delete clause N of M).

@spec module_fn_swap(Macro.t(), map(), module(), [atom()], %{
  required(atom()) => atom()
}) :: [map()]

Swaps a module-qualified function call (Mod.fun(...)) for Mod.opposite(...).

Returns a single mutation when mod is in modules and fun is a key in opposites, otherwise an empty list. The module and arguments are preserved.

@spec operator_swap(Macro.t(), map(), module(), %{required(atom()) => atom()}) :: [
  map()
]

Swaps a binary operator for the value mapped to it in swaps.

Returns a single mutation when the operator is a key in swaps, otherwise an empty list. The two operands are preserved.