Extend `enum` from named int constants to a tagged union: a variant may
carry a payload (`enum Tile { Empty, Wall, Door(int), Portal(int, int) }`).
Such enums box to a heap record (an i32 tag at offset 0, then one 8-byte
slot per payload position); an all-bare enum keeps its zero-cost compile-
time-ordinal representation, byte-for-byte unchanged (every golden render
and the bootstrap fixpoint still hold).
- Parser: variant payload declarations, stored as N_PARAM kids on the
variant node.
- Construction: by name — `Door(3)`, `Portal(x, y)`, bare `Empty` — resolved
ahead of the function-call fallback and boxed with the payloads coerced to
their declared types.
- match: destructures a tagged scrutinee, switching on the tag and binding
each arm's payload names in a scoped local frame.
- Checking pass: a tagged `match` must be exhaustive (cover every variant or
end in `_`), and constructor/pattern arities and binding forms are checked
— all reported where the scrutinee's type is known.
Adds selfhost/tests/enums.ludic to the regression suite and documents the
feature in LANGUAGE.md and the enum/match pages.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Orkuncakilkaya
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