# `Statifier.Machine.Data`
[🔗](https://github.com/riddler/statifier-ex/blob/v2.0.0/lib/statifier/machine/data.ex#L1)

One compiled `<data>` element - the interned counterpart to
`Statifier.Document.Data`, dense from `d_index` 0 across the whole machine
(ADR-0012 item 3), read via `Statifier.Machine.data/2`.

`value` selects among the value-source precedence spec 5.3.2 gives
`<data>` (`expr`, `src`, child content, or none), decided once at
Machine-build time by `Statifier.Compiler`:

- `expr` compiles through `Statifier.Compiler.Expressions.compile/3` like
  any other expression - **except** a compile failure is captured as
  `{:invalid, error}` on this struct rather than failing
  `Statifier.Compiler.compile/1`: spec
  5.9.4 permits either load-time rejection or a runtime `error.execution`,
  and `data_invalid_test.exs` in the corpus needs the latter.
- `src` never resolves in this pure core (ADR-0003) - it is carried as
  `{:src, uri}` and always fails at binding time (spec 5.3.2's "empty data
  element" clause).
- non-blank child text is folded to `{:static, _}` at compile time
  (Decision 8, `Statifier.Compiler.Expressions.inline_value/1`) - it is
  never a `{:compiled, ...}` read of the datamodel.
- no value source at all is `{:static, nil}`.

`value_location` is the diagnostic span, following `cond_location` and
`expr_location`'s "caller's choice" contract
(`lib/statifier/compiler/expressions.ex:36-45`): the written attribute's
value span when written, the `<data>` node's own `location` otherwise.

# `t`

```elixir
@type t() :: %Statifier.Machine.Data{
  d_index: non_neg_integer(),
  id: String.t(),
  location: Statifier.Parser.Location.t(),
  value: value(),
  value_location: Statifier.Parser.Location.t() | nil
}
```

# `value`

```elixir
@type value() ::
  Statifier.Machine.expr()
  | {:invalid, Statifier.Compiler.Error.t()}
  | {:src, uri :: String.t()}
```

---

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