# `Spectral.Type`
[🔗](https://github.com/andreashasse/spectral/blob/main/lib/spectral/type.ex#L1)

Elixir wrapper for the Erlang `:spectra_type` module.

Provides functions for inspecting `sp_type()` values. These are most useful
inside `Spectral.Codec` callbacks, where the `sp_type` argument carries the
instantiation node from the type traversal.

> #### Advanced integrations {: .info}
>
> This module is intended for advanced integrations, such as building custom
> web framework plugins or other tooling on top of Spectral. Most applications
> will not need to use it directly.

# `type_args`

```elixir
@spec type_args(term()) :: [term()]
```

Returns the concrete type-variable bindings for a generic `sp_type()` node.

When a codec is invoked during type traversal for a parameterised type such as
`MapSet.t(integer())` or `dict:dict(binary(), float())`, the `sp_type` argument
is the reference node and `type_args/1` returns the list of concrete type
arguments in declaration order.

Returns `[]` when the type has no type variables, or when the codec is invoked
directly from a `Spectral.encode/decode/schema` entry point rather than from
mid-traversal dispatch.

## Example

    # In a codec for MapSet.t(elem):
    def encode(:json, mod, {:type, :t, 1}, %MapSet{} = ms, sp_type, _params, _config) do
      case Spectral.Type.type_args(sp_type) do
        [elem_type] ->
          # recursively encode each element using elem_type
        [] ->
          # no type info available, fall back to plain list
          {:ok, MapSet.to_list(ms)}
      end
    end

---

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