Build an independent OSTW/DeltinScript-compatible implementation with canonical Workshop integration

[Teakowa]

Goal

Build deltin-rs into an independent, corpus-backed implementation of the declared OSTW/DeltinScript language and compiler semantics, integrated with the canonical workshop-rs backend without duplicating Workshop ownership.

Context

deltin-rs owns DEL/OSTW project loading, source syntax, semantic analysis, type/runtime semantics, typed backend-neutral HIR, diagnostics/provenance, source-language tooling, lowering, and scoped reconstruction.

workshop-rs owns canonical raw Workshop semantics, WIR, catalog, validation, localization, settings, and emission.

The durable forward boundary is:

DEL/OSTW source -> source/project model -> DEL semantic model -> typed DEL HIR -> workshop-rs canonical WIR -> validation/emission

Compatibility targets observable semantics for the declared support surface, not upstream compiler architecture or output-text identity.

Scope

• Maintain provenance-aware compatibility evidence against pinned OSTW/DeltinScript references and representative real projects.
• Own recoverable parsing, multi-file/import behavior, semantic resolution, type checking, advanced DEL/OSTW language/runtime semantics, and typed backend-neutral HIR.
• Expose semantic APIs useful for check, diagnostics, inspect, lint, validated source tooling, CI, and agents independently of Workshop emission.
• Integrate Workshop builtins/catalog binding, concrete runtime lowering, WIR validation, settings, localization, and emission strictly through canonical workshop-rs contracts.
• Model target-specific allocation, deletion, references, virtual dispatch, storage, recursion, closures, and related runtime behavior only where observable DEL/OSTW semantics require it.
• Use semantic/normalized Workshop equivalence and runtime-sensitive evidence rather than compiler-output identity as the compatibility target.
• Pursue Workshop -> DEL/OSTW reconstruction only through a separately reviewed useful-source/semantic-equivalence contract with explicit information-loss boundaries.

Non-goals

• Reproducing the VS Code extension or editor UI as part of core language compatibility.
• Copying upstream compiler architecture, temporary variables, optimizer internals, formatting, helper naming, or byte-identical Workshop output.
• Duplicating canonical Workshop actions, values, events, settings, locale/catalog data, parser, WIR, validation, or emitter logic in deltin-rs.
• Treating every utility in the upstream repository as part of the compatibility contract without evidence.
• Freezing reconstruction architecture before forward integration establishes a useful canonical round-trip boundary.
• Maintaining live implementation progress, release versions, or active-child status in this parent issue.

Acceptance criteria

• The declared OSTW/DeltinScript language/compiler surface is tracked by provenance-aware executable evidence with explicit compatibility states.
• Supported source can be parsed, resolved, inspected, and diagnosed independently of Workshop emission.
• High-level language/runtime semantics have corpus-backed tests independent of concrete Workshop encoding.
• Supported end-to-end source lowers to canonical Workshop semantics and emits through workshop-rs with evidence-backed behavior.
• Workshop-dependent and unsupported gaps remain explicit rather than being hidden by output differences or counted as successful compatibility.
• deltin-rs never becomes a second authoritative Workshop implementation.
• Cross-repository gaps follow the owner sequence: owning repo -> owner contract/tests -> consumable contract/release -> deltin-rs integration -> corpus/real-workflow verification.
• Workshop -> DEL/OSTW reconstruction is validated against the established forward/canonical semantic boundary rather than literal source recovery.

Related work

Forward Workshop integration and reconstruction are decomposed into executable child/follow-up issues. Their current state and execution ordering should be derived from GitHub relationships, PRs, releases, and executable evidence rather than duplicated here.