go: types.sx — call type-checking + 8 tests; recursive funcs now type [nothing]

Phase 3 cont. The expression-synth :app dispatch is now bifurcated:

  * go-is-binop-call? — head is :var with an operator name AND 2 args
    AND the operator is in one of the binop tables. Short-circuits to
    go-synth-binop as before.
  * Everything else routes to go-synth-call.

go-synth-call:
  1. Synth the callee. Must produce a (list :ty-func PARAMS RESULTS).
     Otherwise → (:type-error :not-callable TYPE).
  2. Arity-check args vs params. Mismatch → (:type-error :arity-mismatch).
  3. go-check-args-against: each arg assignable to corresponding param
     (untyped-constant flow works — `f(42)` accepts the untyped int
     into an int param).
  4. Result by count:
       0 results → (list :ty-void)
       1 result  → that result directly
       N results → (list :ty-tuple TYPES)   for multi-return

The recursive case lights up: go-check-func-decl binds the function
in its own body's ctx before checking. So:

  func fib(n int) int { return fib(n) + fib(n) }

now type-checks because `fib` resolves inside the body, synth-call
sees its `:ty-func` and verifies the recursive call. Multi-return
functions destructure into `:ty-tuple` which short-decl will need to
consume next iteration.

types 55/55, total 360/360.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

lib/go/scoreboard.json

@@ -1,11 +1,11 @@
 {
   "language": "go",
-  "total_pass": 352,
-  "total": 352,
+  "total_pass": 360,
+  "total": 360,
   "suites": [
     {"name":"lex","pass":129,"total":129,"status":"ok"},
     {"name":"parse","pass":176,"total":176,"status":"ok"},
-    {"name":"types","pass":47,"total":47,"status":"ok"},
+    {"name":"types","pass":55,"total":55,"status":"ok"},
     {"name":"eval","pass":0,"total":0,"status":"pending"},
     {"name":"runtime","pass":0,"total":0,"status":"pending"},
     {"name":"stdlib","pass":0,"total":0,"status":"pending"},

lib/go/scoreboard.md

@@ -1,12 +1,12 @@
 # Go-on-SX Scoreboard
 
-**Total: 352 / 352 tests passing**
+**Total: 360 / 360 tests passing**
 
 |  | Suite | Pass | Total |
 |---|---|---|---|
 | ✅ | lex | 129 | 129 |
 | ✅ | parse | 176 | 176 |
-| ✅ | types | 47 | 47 |
+| ✅ | types | 55 | 55 |
 | ⬜ | eval | 0 | 0 |
 | ⬜ | runtime | 0 | 0 |
 | ⬜ | stdlib | 0 | 0 |

lib/go/tests/types.sx

@@ -326,6 +326,95 @@
     "g")
   (list :ty-func (list) (list (list :ty-name "int"))))
 
+(go-types-test
+  "call: synth result of typed func"
+  (go-synth
+    (go-ctx-extend
+      go-ctx-empty
+      "double"
+      (list
+        :ty-func (list (list :ty-name "int"))
+        (list (list :ty-name "int"))))
+    (go-parse "double(5)"))
+  (list :ty-name "int"))
+
+(go-types-test
+  "call: arg-count mismatch"
+  (go-synth
+    (go-ctx-extend
+      go-ctx-empty
+      "double"
+      (list
+        :ty-func (list (list :ty-name "int"))
+        (list (list :ty-name "int"))))
+    (go-parse "double(1, 2)"))
+  (list :type-error :arity-mismatch 1 2))
+
+(go-types-test
+  "call: arg-type mismatch"
+  (go-synth
+    (go-ctx-extend
+      go-ctx-empty
+      "f"
+      (list
+        :ty-func (list (list :ty-name "int"))
+        (list (list :ty-name "int"))))
+    (go-parse "f(\"hi\")"))
+  (list
+    :type-error :mismatch
+    (list :ty-name "int")
+    (list :ty-untyped-string)))
+
+(go-types-test
+  "call: not callable (calling an int)"
+  (go-synth
+    (go-ctx-extend go-ctx-empty "x" (list :ty-name "int"))
+    (go-parse "x(1)"))
+  (list :type-error :not-callable (list :ty-name "int")))
+
+(go-types-test
+  "call: no-result func (void) call"
+  (go-synth
+    (go-ctx-extend
+      go-ctx-empty
+      "log"
+      (list :ty-func (list (list :ty-name "string")) (list)))
+    (go-parse "log(\"hi\")"))
+  (list :ty-void))
+
+(go-types-test
+  "call: multi-return → :ty-tuple"
+  (go-synth
+    (go-ctx-extend
+      go-ctx-empty
+      "divmod"
+      (list
+        :ty-func (list (list :ty-name "int") (list :ty-name "int"))
+        (list (list :ty-name "int") (list :ty-name "int"))))
+    (go-parse "divmod(10, 3)"))
+  (list :ty-tuple (list (list :ty-name "int") (list :ty-name "int"))))
+
+(go-types-test
+  "call: recursive func works (fib)"
+  (go-ctx-lookup
+    (go-check-decl
+      go-ctx-empty
+      (go-parse "func fib(n int) int { return fib(n) + fib(n) }"))
+    "fib")
+  (list :ty-func (list (list :ty-name "int")) (list (list :ty-name "int"))))
+
+(go-types-test
+  "call: untyped-int arg accepted into int param"
+  (go-synth
+    (go-ctx-extend
+      go-ctx-empty
+      "double"
+      (list
+        :ty-func (list (list :ty-name "int"))
+        (list (list :ty-name "int"))))
+    (go-parse "double(42)"))
+  (list :ty-name "int"))
+
 (define
   go-types-test-summary
   (str "types " go-types-test-pass "/" go-types-test-count))

lib/go/types.sx

@@ -253,15 +253,67 @@
               (cond
                 (= t nil) (list :type-error :unbound name)
                 :else t)))))
-      ;; (:app (:var OP) [LHS RHS]) — binary operator
-      (and (list? expr) (= (first expr) :app)
-           (list? (nth expr 1)) (= (first (nth expr 1)) :var)
-           (= (len (nth expr 2)) 2))
-      (let ((op (nth (nth expr 1) 1))
-            (args (nth expr 2)))
-        (go-synth-binop ctx op (first args) (nth args 1)))
+      ;; (:app HEAD ARGS) — function application:
+      ;;   binop if HEAD is :var with an operator name + 2 args
+      ;;   else: general function call
+      (and (list? expr) (= (first expr) :app))
+      (let ((head (nth expr 1)) (args (nth expr 2)))
+        (cond
+          (go-is-binop-call? head args)
+          (go-synth-binop ctx (nth head 1) (first args) (nth args 1))
+          :else (go-synth-call ctx head args)))
       :else (list :type-error :unsupported-synth expr))))
 
+(define
+  go-is-binop-call?
+  (fn (head args)
+    (and (list? head) (= (first head) :var)
+         (= (len args) 2)
+         (let ((op (nth head 1)))
+           (or (some (fn (o) (= o op)) go-arith-binops)
+               (some (fn (o) (= o op)) go-bitwise-binops)
+               (some (fn (o) (= o op)) go-compare-binops)
+               (some (fn (o) (= o op)) go-logical-binops))))))
+
+(define
+  go-check-args-against
+  ;; Each arg in ARGS assignable to the corresponding PARAMS type.
+  ;; Caller already verified arities match.
+  (fn (ctx args params)
+    (cond
+      (or (= (len args) 0) (= (len params) 0)) :ok
+      :else
+      (let ((r (go-check ctx (first args) (first params))))
+        (cond
+          (go-type-error? r) r
+          :else (go-check-args-against ctx (rest args) (rest params)))))))
+
+(define
+  go-synth-call
+  ;; Synth a function call. Returns the result type, or :type-error.
+  ;;   0 results → (list :ty-void)
+  ;;   1 result  → that result type directly
+  ;;   N results → (list :ty-tuple TYPES) (multi-return)
+  (fn (ctx callee args)
+    (let ((fn-ty (go-synth ctx callee)))
+      (cond
+        (go-type-error? fn-ty) fn-ty
+        (not (and (list? fn-ty) (= (first fn-ty) :ty-func)))
+        (list :type-error :not-callable fn-ty)
+        :else
+        (let ((params (nth fn-ty 1)) (results (nth fn-ty 2)))
+          (cond
+            (not (= (len args) (len params)))
+            (list :type-error :arity-mismatch
+              (len params) (len args))
+            :else
+            (let ((err (go-check-args-against ctx args params)))
+              (cond
+                (go-type-error? err) err
+                (= (len results) 0) (list :ty-void)
+                (= (len results) 1) (first results)
+                :else (list :ty-tuple results)))))))))
+
 (define
   go-synth-binop
   (fn (ctx op lhs rhs)

plans/go-on-sx.md

@@ -239,14 +239,17 @@ Progress-log line → push `origin/loops/go`.
       signature, assignments verify RHS assignable to LHS). The function
       itself is bound in the body's ctx so recursion will work once
       call-checking lands. Signature-only (no body) just binds.
-- [ ] Call type-checking (synth callee, check args against param types,
-      synth result).
+- [x] Call type-checking. `go-synth-call`: synth callee → expect
+      `:ty-func`, arity-check, check each arg assignable to param,
+      then return type by result count (0 → `:ty-void`, 1 → that type,
+      N → `:ty-tuple`). Recursive calls now type-check because the func
+      is bound in the body's ctx. Untyped-constant args flow through.
 - [ ] Composite type element checking (slice / map / chan).
 - [ ] Interface satisfaction (structural match against method sets).
 - [ ] Short variable declaration `:=` (synth RHS into LHS bindings).
 - Defer: generics (Phase 7), full conversion rules, type assertions,
   type switches.
-- **Acceptance:** types/ suite at 60+ tests. Current: 47/47. Chisel note
+- **Acceptance:** types/ suite at 60+ tests. Current: 55/55. Chisel note
   `shapes-static-types-bidirectional` — sister-plan design diary is the
   cross-language record.
 
@@ -547,6 +550,20 @@ Minimal repro: see `lib/go/lex.sx#gl-oct-digit?` and `#gl-match-op`.
 
 _Newest first. Append one dated entry per commit._
 
+- 2026-05-27 — Phase 3 cont.: call type-checking. `go-synth-call`
+  synthesises the callee's type, asserts it's a `:ty-func`, arity-
+  checks args, then `go-check-args-against` runs each arg through
+  `go-check` against the corresponding param type (untyped-constant
+  flow works). Result: `:ty-void` for 0-result funcs, the result type
+  for 1-result, `(list :ty-tuple TYPES)` for multi-return. The
+  `:app` dispatch in `go-synth` now routes via `go-is-binop-call?`
+  (operator name + 2 args + op in the binop tables) — binops short-
+  circuit; everything else goes through the call path. **Recursive
+  functions now type-check** because the func is bound in its own
+  body's ctx by `go-check-func-decl`. +8 tests, types 55/55, total
+  360/360. `[nothing]` — Go-side composition on top of established
+  primitives; no new kit-relevant shapes (call semantics are uniform
+  across statically-typed guests).
 - 2026-05-27 — Phase 3 cont.: function-declaration checking +
   statement-level dispatch. `go-check-func-decl` binds the function in
   the outer ctx (so the body can see itself), extends the body's ctx