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>
Extends match-pattern in spec/evaluator.sx with an ADT case: when the
pattern is (CtorName var...) and the value is an ADT dict (:_adt true),
check :_ctor matches, arity matches, then recursively bind field patterns.
Supports nested patterns, wildcard _, variable binding, and zero-arg ctors.
Changes step-sf-match to route no-clause errors through raise-eval-frame
instead of direct error, allowing guard to catch non-exhaustive matches.
40/40 ADT tests pass (20 define-type + 20 match). Zero regressions.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
