# `Mutare.Ecto.BindingReorder`
[🔗](https://github.com/foxbenjaminfox/mutare_ecto/blob/v0.4.2/lib/mutare/ecto/binding_reorder.ex#L1)

Positional **binding-reorder** mutants for every standalone/pipe query macro that takes a binding
pattern list — the `where`/`having` condition macros, `select`, `select_merge`, `order_by`,
`group_by`, `distinct`, `join`, `preload`, `windows`, …, and the free-standing `dynamic/2`
(the condition/clause/join/dynamic descriptors in `Mutare.Ecto.Surface`).

A binding list maps names to the query's bindings **by position**: `[a, b]` binds `a`→1st,
`b`→2nd. Transposing two positional entries (`[a, b]` → `[b, a]`) tests whether their order
matters. **Named** bindings (`comments: c`) are addressed by name, not position, so they are left
in place. `_`-prefixed bindings are intentionally ignored, matching core's pattern-swap policy.

The reorder is always delivered **in place** — by swapping the written list, never by rewriting the
condition body. The list sits in an ordinary argument position (not inside a macro-expanded query
fragment), so the whole macro call (itself an expression returning a query) uses Mutare's ordinary
selector `case`; no host / `dynamic` weaving is needed. Leaving the body byte-for-byte untouched is
also what makes the swap safe across an opaque author macro in that body (the author-macro rule —
see `Mutare.Ecto.Walk`). Wrong-schema field access from a swap surfaces at query-plan time
(runtime), not compile time, so a mutant never causes the single build to fail.

This covers the macros whose binding list is an **argument**. A `from`'s binding-list *source*
(`from [a, b] in q, …`) is written at the whole-`from` level, so its reorder is delivered there
(`Mutare.Ecto.Query`) — one whole-`from` mutant swapping the source declaration, never a per-clause
rewrite. A scalar `from` source (`u in User`) and the join-introduced bindings are synthesized, not
written as a list, so they never reorder.

Every pair of eligible bindings is swapped, even when one or both are unused. Such a surviving
mutant identifies a redundant binding declaration, matching core's pattern-swap policy.

# `mutations`

```elixir
@spec mutations(Mutare.Ecto.AST.QueryCall.t(), Mutare.Ecto.Context.t()) :: [
  Mutare.Ecto.Tag.t()
]
```

Binding-reorder mutants for `node` as `:binding_reorder` tags, or `[]`.

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