# Enum values and failures through a package

How your app writes a package's enum values and failures: through the
package's name, as its types are.

- **One path for every name through a package.** An enum's value is
  written through its package as its type is, `AcmeCouriers.Window.morning`,
  and through the package and its version while two are held,
  `Postcodes.v3.Round.morning`; the version is missing or needless exactly
  as for a type (`package.version_needed`, `package.version_unneeded`), and
  the type must be one the package makes public. The same holds wherever a
  value is written: in a body, a constant, a test's `fakes:`, a variant
  built with its fields (`Postcodes.v3.Round.shared { ... }`) and a
  `match` arm's pattern, whose names resolution checks as a value's; a pattern resolution refuses leaves
  its arm's case unknown, so the `match` isn't also reported as not
  covering it. The enum written alone, `Postcodes.Round`, is
  `type.not_a_value` naming the enum, not the package.

- **A package's failure in an outcome `match`.** An app's `match` on a
  provider call, a package action or a library package's function names
  the package's failure in its arm as `fails` and `attempt` write it,
  through the package, `AcmeCouriers.SlotTaken ->`, and through the
  package and its version while two are held,
  `Postcodes.v3.InvalidPostcode ->`; an arm it misses is named the same
  way. The version is missing or needless exactly as for a type, and an
  arm resolution refuses leaves its failure unknown, so the `match`
  isn't also told it misses one. Inside its own code a package still
  names its failures bare.