# `Mutare.Mutators.PatternWildcard`
[🔗](https://github.com/foxbenjaminfox/mutare/blob/v0.2.1/lib/mutare/mutators/pattern_wildcard.ex#L1)

Replaces repeated variables in a pattern with `_`, removing the equality constraint created by the repetition:

    def equal?(x, x), do: true  →  def equal?(_, _), do: true

The replacement policy keeps required bindings intact:

  * If the variable is read by the guard or body, or appears at least three times in the head, one mutant is produced for each wildcarded occurrence.
  * If it appears exactly twice and is not read elsewhere, both occurrences are replaced in one mutant. Replacing only one would leave an unused binding.

`_`, underscore-prefixed names, pinned variables, and module-attribute reads
(`%{@key => v}` — a compile-time constant whose inner AST merely looks like a
variable) are not counted or replaced. On the right side of a bitstring `::`, atoms such as `binary` have the same AST shape as variables, so that side is not searched for pattern occurrences.

A variable read by a bitstring specifier is also excluded. For example, the `n` bound and read by `<<n, rest::size(n)>>` cannot be wildcarded without leaving an invalid size reference.

This family is enabled by default and uses the `pattern_wildcard` ignore name.

# `pattern_mutations`

```elixir
@spec pattern_mutations([Macro.t()], MapSet.t()) :: [[Macro.t()]]
```

Returns the wildcard variants for repeated variables in `head_args`.

`used_outside` contains variable names read by the clause body or guard and
determines whether one occurrence must remain bound. Returns `[]` when no
variable is repeated.

---

*Consult [api-reference.md](api-reference.md) for complete listing*