Orkuncakilkaya
872f458cb2
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>
50 lines
1.5 KiB
Text
50 lines
1.5 KiB
Text
program T {
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# a tagged-union enum (issue #56): variants carry payloads, are constructed by
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# name, and destructure in `match` with the payload names bound in each arm.
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enum Tile { Empty, Wall, Door(int), Portal(int, int) }
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# match binds each variant's payload; the arms are exhaustive (no `_`).
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function walk_cost(t: Tile) -> int {
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match t {
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Empty => { return 1 }
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Wall => { return 0 }
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Door(n) => { return 10 + n }
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Portal(x, y) => { return x + y }
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}
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return -1
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}
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# a nested match and an enum flowing through a return
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function open(t: Tile) -> Tile {
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match t {
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Door(n) => { return Portal(n, n) }
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_ => { return t }
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}
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return t
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}
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entry {
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print(walk_cost(Empty)) # 1
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print(walk_cost(Wall)) # 0
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print(walk_cost(Door(5))) # 15
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print(walk_cost(Portal(3, 4))) # 7
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let d = Door(9)
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print(walk_cost(d)) # 19
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print(walk_cost(open(d))) # 18 (Door(9) -> Portal(9,9) -> 18)
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print(walk_cost(open(Wall))) # 0 (default arm returns t unchanged)
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# a match with a default arm, OR-ed nullary patterns, and a bound arm
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let t = Portal(2, 40)
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match t {
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Empty, Wall => { print(100) }
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Portal(x, y) => { print(x * y) } # 80
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_ => { print(999) }
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}
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# payload-less variant boxed and matched
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var here: Tile = Empty
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here = Door(7)
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print(walk_cost(here)) # 17
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}
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}
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