implement-domain-model

Map each documented element to a type, each operation to a method on the appropriate state type, and each rejection reason to a sentinel error. Use sealed interface sum types with per-state structs, value receivers returning Transition[Next, Event], and never add operations the document does not define.

Typestate gives each aggregate state its own struct type, so impossible operations simply have no method on that type. A sealed interface acts as the sum type, AsX functions narrow states with sentinel errors, and transitions return the next state value plus its domain event.

No. The domain package uses only the Go standard library (errors, time, context, slices) and must not import persistence, RPC, or logging packages. An import boundary check with go list verifies this constraint.

NewX returns an error only when the documented generation conditions include rejectable combinations, such as an empty identifier or end-before-start time slot. If no combination can be rejected, the constructor returns the value alone to avoid dead error branches.

Implementation stops rather than guessing. Missing operations, preconditions, events, or unresolved decisions are reported back to the document author with the specific gaps listed, and no defaults or placeholders are substituted.