prometeu-studio/docs/pbs/agendas/12.3. IR and Lowering Workshop 3 - Callables, Services, Contracts, and Callbacks.md

PBS IR and Lowering Workshop 3

Status: Active

Purpose

Run the third focused discussion for 12. IR and Lowering Specification.md on callable categories beyond ordinary top-level functions:

• callbacks,
• services,
• contracts,
• methods,
• and dispatch obligations.

Why This Slice Third

This slice should come after control-flow lowering because it builds on the general execution model while introducing runtime-dispatch and identity-sensitive concerns.

Proposed Meeting Order

1. Reconfirm callable categories and identity facts already fixed.
2. Close callback formation and invocation lowering.
3. Close service and method lowering.
4. Close contract-view and dispatch lowering.
5. Record builtin and host-binding specifics for Workshop 4.

Decisions To Produce

1. The lowering story for callback formation and invocation.
2. The lowering story for service singleton methods.
3. The lowering story for contracts and dispatch.
4. Which runtime-artifact facts must be explicit versus implementation-defined.

Candidate Decisions

1. Callback Lowering Must Preserve Captured Identity And Retention

Candidate direction:

• callback values created by bind lower to a representation that preserves: target callable identity, captured context identity, and retention-bearing lifetime facts.

Rationale:

• These are already required by memory and semantics specs.

2. Service Lowering Preserves Singleton Identity

Candidate direction:

• service method calls lower through the module-owned singleton identity,
• and lowering must not accidentally materialize new service instances.

Rationale:

• This is a language-observable property.

3. Contract Lowering Must Preserve Selected Implementation Identity

Candidate direction:

• contract values lower as runtime-dispatchable views over an underlying owner plus implementation selection,
• but 12 does not freeze one concrete table or object layout yet.

Rationale:

• This keeps the semantic contract clear while deferring layout choices.

4. Receiver-Bearing Method Calls Need Explicit Lowered Receiver Handling

Candidate direction:

• struct, service, and contract method calls lower through an explicit receiver-bearing callable shape,
• even if the backend later optimizes the representation.

Rationale:

• This keeps receiver identity and call semantics visible in the spec.

Questions To Resolve In The Room

1. Does contract dispatch need a dedicated runtime artifact category in the spec?
2. Does callback lowering need one explicit abstract representation?
3. How much of method dispatch belongs in 12 versus runtime execution specs?
4. Are service methods lowered like receiver calls or like specialized global calls?
5. Which of these constructs need explicit artifact invariants before 15?

Expected Outputs

1. a decision record for callback lowering,
2. a decision record for service and contract lowering,
3. and callable-category section targets for 12.

Explicit Deferrals For Workshop 4

• builtin projection lowering,
• builtin constants,
• host-binding emission,
• and verifier-facing artifact invariants.

Inputs

• docs/pbs/specs/4. Static Semantics Specification.md
• docs/pbs/specs/9. Dynamic Semantics Specification.md
• docs/pbs/specs/10. Memory and Lifetime Specification.md
• docs/pbs/specs/12. IR and Lowering Specification.md
• docs/pbs/agendas/12. IR and Lowering Agenda.md
• docs/pbs/agendas/12.2. IR and Lowering Workshop 2 - Control Flow, Evaluation Order, and Propagation.md