Any Failure at all — the type to reach for when a signature accepts failures it does not enumerate, e.g. Result<T, Failure.Any> at a boundary that only logs.

import * as Failure from './failure.ts'; // the consumer spelling this module's docs use

function report(failure: Failure.Any) {
  console.error(failure.code, failure.data); // every Failure has these, whatever its kind
}

Since Data defaults to unknown, this is the same type as an unparameterised Failure — the alias earns its keep twice anyway. Under the standard import * as Failure namespace import, the class type is not nameable without the stuttering Failure.Failure, so Failure.Any is the spelling that reads. And §8.15 of the docs warns that widening to the top type early silently discards exhaustiveness checking — because every deliberate widening is spelled Any, grep 'Failure.Any' audits exactly where the taxonomy goes un-enumerated.