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/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))