Native algebraic data type representation in the OCaml SX evaluator.
Replaces the dict-based shim that simulated ADT values via tagged dicts.
- sx_types.ml: add AdtValue variant + adt_value record (av_type, av_ctor,
av_fields). type_of returns the type name (e.g. "Maybe"); inspect renders
as a constructor call (e.g. "(Just 42)" or "(Nothing)").
- sx_runtime.ml: get_val handles AdtValue with :_adt/:_type/:_ctor/:_fields
keys for back-compat with spec-level match-pattern code.
- sx_primitives.ml: dict? returns true for AdtValue (so existing match
dispatch keeps working); new adt? predicate distinguishes ADT values.
- sx_ref.ml: sf_define_type now constructs AdtValue instead of Dict.
Predicates (Name?, Ctor?) and accessors (Ctor-field) match on AdtValue
with proper type/ctor name and field index checks.
- spec/tests/test-adt.sx: 3 new tests covering type-of, adt?, and inspect.
Tests: 4532 passed (was 4529 + 3 new), 1339 failed (unchanged baseline).
All 43 ADT tests pass on the native representation.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
giles
1f49242ae3