lua: coroutines (create/resume/yield/status/wrap) via call/cc +8 tests

lib/lua/runtime.sx

@@ -529,3 +529,125 @@
   (fn
     (args i)
     (if (< i (len args)) (nth args i) nil)))
+
+;; ── Coroutines (call/cc based) ────────────────────────────────
+(define __current-co nil)
+
+(define
+  lua-coroutine-create
+  (fn
+    (f)
+    (let ((co {}))
+      (begin
+        (dict-set! co "__co" true)
+        (dict-set! co "status" "suspended")
+        (dict-set! co "body" f)
+        (dict-set! co "resume-k" nil)
+        (dict-set! co "caller-k" nil)
+        co))))
+
+(define
+  lua-coroutine-status
+  (fn
+    (co)
+    (if (and (= (type-of co) "dict") (has-key? co "__co"))
+        (get co "status")
+        (error "lua: not a coroutine"))))
+
+(define
+  lua-co-wrap-result
+  (fn (r)
+    (cond
+      ((lua-multi? r) (cons (quote lua-multi) (cons true (rest r))))
+      (else (list (quote lua-multi) true r)))))
+
+(define
+  lua-co-first-call
+  (fn (co rvals prev)
+    (let ((r (lua-apply (get co "body") rvals)))
+      (begin
+        (dict-set! co "status" "dead")
+        (set! __current-co prev)
+        ((get co "caller-k") (lua-co-wrap-result r))))))
+
+(define
+  lua-co-continue-call
+  (fn (co rvals)
+    (let ((rk (get co "resume-k")))
+      (begin
+        (dict-set! co "resume-k" nil)
+        (rk (if (> (len rvals) 0) (first rvals) nil))))))
+
+(define
+  lua-coroutine-resume
+  (fn
+    (&rest args)
+    (let ((co (first args)) (rvals (rest args)))
+      (cond
+        ((not (and (= (type-of co) "dict") (has-key? co "__co")))
+          (list (quote lua-multi) false "not a coroutine"))
+        ((= (get co "status") "dead")
+          (list (quote lua-multi) false "cannot resume dead coroutine"))
+        ((= (get co "status") "running")
+          (list (quote lua-multi) false "cannot resume running coroutine"))
+        (else
+          (call/cc
+            (fn (k)
+              (let ((prev __current-co))
+                (begin
+                  (dict-set! co "caller-k" k)
+                  (dict-set! co "status" "running")
+                  (set! __current-co co)
+                  (guard
+                    (e (true
+                         (begin
+                           (dict-set! co "status" "dead")
+                           (set! __current-co prev)
+                           (list (quote lua-multi) false e))))
+                    (cond
+                      ((= (get co "resume-k") nil) (lua-co-first-call co rvals prev))
+                      (else (lua-co-continue-call co rvals)))))))))))))
+
+(define
+  lua-coroutine-yield
+  (fn
+    (&rest yvals)
+    (cond
+      ((= __current-co nil) (error "lua: attempt to yield from outside a coroutine"))
+      (else
+        (call/cc
+          (fn (k)
+            (let ((co __current-co))
+              (begin
+                (dict-set! co "resume-k" k)
+                (dict-set! co "status" "suspended")
+                (set! __current-co nil)
+                ((get co "caller-k") (cons (quote lua-multi) (cons true yvals)))))))))))
+
+(define
+  lua-co-wrap-caller
+  (fn (co args)
+    (let ((r (sx-apply-ref lua-coroutine-resume (cons co args))))
+      (cond
+        ((and (lua-multi? r) (> (len r) 1) (= (nth r 1) true))
+          (cond
+            ((<= (len r) 2) nil)
+            ((= (len r) 3) (nth r 2))
+            (else (cons (quote lua-multi) (rest (rest r))))))
+        ((and (lua-multi? r) (> (len r) 1))
+          (error (if (> (len r) 2) (nth r 2) "coroutine error")))
+        (else nil)))))
+
+(define
+  lua-coroutine-wrap
+  (fn (f)
+    (let ((co (lua-coroutine-create f)))
+      (fn (&rest args) (lua-co-wrap-caller co args)))))
+
+(define coroutine {})
+
+(dict-set! coroutine "create" lua-coroutine-create)
+(dict-set! coroutine "resume" lua-coroutine-resume)
+(dict-set! coroutine "yield" lua-coroutine-yield)
+(dict-set! coroutine "status" lua-coroutine-status)
+(dict-set! coroutine "wrap" lua-coroutine-wrap)

lib/lua/test.sh

@@ -710,6 +710,24 @@ cat > "$TMPFILE" << 'EPOCHS'
 (epoch 980)
 (eval "(lua-eval-ast \"local t = setmetatable({x = 1, y = 2}, {}) local n = 0 for k in pairs(t) do n = n + 1 end return n\")")
 
+;; ── Phase 5: coroutines ────────────────────────────────────────
+(epoch 1000)
+(eval "(lua-eval-ast \"local co = coroutine.create(function() end) return coroutine.status(co)\")")
+(epoch 1001)
+(eval "(lua-eval-ast \"local co = coroutine.create(function() return 42 end) coroutine.resume(co) return coroutine.status(co)\")")
+(epoch 1010)
+(eval "(lua-eval-ast \"local co = coroutine.create(function() coroutine.yield(1) coroutine.yield(2) return 3 end) local ok1, v1 = coroutine.resume(co) local ok2, v2 = coroutine.resume(co) local ok3, v3 = coroutine.resume(co) return v1 * 100 + v2 * 10 + v3\")")
+(epoch 1011)
+(eval "(lua-eval-ast \"local co = coroutine.create(function(a, b) return a + b end) local ok, v = coroutine.resume(co, 10, 20) return v\")")
+(epoch 1012)
+(eval "(lua-eval-ast \"local co = coroutine.create(function() local x = coroutine.yield() return x + 100 end) coroutine.resume(co) local ok, v = coroutine.resume(co, 42) return v\")")
+(epoch 1020)
+(eval "(lua-eval-ast \"local co = coroutine.create(function() return 42 end) coroutine.resume(co) local ok, err = coroutine.resume(co) if ok then return \\\"no\\\" else return err end\")")
+(epoch 1030)
+(eval "(lua-eval-ast \"local gen = coroutine.wrap(function() coroutine.yield(1) coroutine.yield(2) coroutine.yield(3) end) return gen() + gen() + gen()\")")
+(epoch 1040)
+(eval "(lua-eval-ast \"local function iter() coroutine.yield(10) coroutine.yield(20) coroutine.yield(30) end local co = coroutine.create(iter) local sum = 0 for i = 1, 3 do local ok, v = coroutine.resume(co) sum = sum + v end return sum\")")
+
 EPOCHS
 
 OUTPUT=$(timeout 60 "$SX_SERVER" < "$TMPFILE" 2>/dev/null)
@@ -1062,6 +1080,16 @@ check 970 "stateful closure iter"           '15'
 check 971 "3-value iterator form"           '30'
 check 980 "pairs skips __meta"              '2'
 
+# ── Phase 5: coroutines ────────────────────────────────────────
+check 1000 "coroutine.status initial"       '"suspended"'
+check 1001 "coroutine.status after done"    '"dead"'
+check 1010 "yield/resume × 3 sequence"      '123'
+check 1011 "resume passes args to body"     '30'
+check 1012 "resume passes args via yield"   '142'
+check 1020 "resume dead returns error"      '"cannot resume dead coroutine"'
+check 1030 "coroutine.wrap"                 '6'
+check 1040 "iterator via coroutine"         '60'
+
 TOTAL=$((PASS + FAIL))
 if [ $FAIL -eq 0 ]; then
   echo "ok $PASS/$TOTAL Lua-on-SX tests passed"

plans/lua-on-sx.md

@@ -65,7 +65,7 @@ Each item: implement → tests → tick box → update progress log.
 - [x] Generic `for … in …`
 
 ### Phase 5 — coroutines (the showcase)
-- [ ] `coroutine.create`/`.resume`/`.yield`/`.status`/`.wrap` via `perform`/`cek-resume`
+- [x] `coroutine.create`/`.resume`/`.yield`/`.status`/`.wrap` via `perform`/`cek-resume`
 
 ### Phase 6 — standard library
 - [ ] `string` — `format`, `sub`, `find`, `match`, `gmatch`, `gsub`, `len`, `rep`, `upper`, `lower`, `byte`, `char`
@@ -82,6 +82,7 @@ Each item: implement → tests → tick box → update progress log.
 
 _Newest first. Agent appends on every commit._
 
+- 2026-04-24: lua: phase 5 — coroutines (create/resume/yield/status/wrap) via `call/cc` (perform/cek-resume not exposed to SX userland). Handles multi-yield + final return + arg passthrough. Fix: body's final return must jump via `caller-k` to the **current** resume's caller, not unwind through the stale first-call continuation. 273 tests.
 - 2026-04-24: lua: generic `for … in …` — parser split (`=` → num, else `in`), new `lua-for-in` node, transpile to `let`-bound `f,s,var` + recursive `__for_loop`. Added `ipairs`/`pairs`/`next`/`lua-arg` globals. Lua fns now arity-tolerant (`&rest __args` + indexed bind) — needed because generic for always calls iter with 2 args. Noted early-return-in-nested-block as pre-existing limitation. 265 tests.
 - 2026-04-24: lua: `pcall`/`xpcall`/`error` via SX `guard` + `raise`. Added `lua-apply` (arity-dispatch 0-8, apply fallback) because SX `apply` re-wraps raises as "Unhandled exception". Table payloads preserved (`error({code = 42})`). 256 total tests.
 - 2026-04-24: lua: phase 4 — metatable dispatch (`__index`/`__newindex`/arith/compare/`__call`/`__len`), `setmetatable`/`getmetatable`/`type` globals, OO `self:method` pattern. Transpile routes all calls through `lua-call` (stashed `sx-apply-ref` to dodge user-shadowing of SX `apply`). Skipped `__tostring` (needs `tostring()` builtin). 247 total tests.