go: parse.sx — function calls + member access + 12 tests [consumes-ast proposes-ast]

Adds postfix expression forms per Go spec:
  f()  f(x)  f(x, y, z)       — function calls
  x.y  x.y.z  obj.method(x)   — selector / member access

gp-parse-postfix sits between gp-parse-unary and gp-parse-primary,
so calls and selectors bind tighter than any unary prefix — `-f(x)`
parses as `-(f(x))`, not `(-f)(x)`. Postfix is left-associative
(`x.y.z` = `(x.y).z`), so the loop iterates rather than recurses
on the LHS.

AST shapes:
  Call:     (ast-app FN ARGS)              — canonical
  Selector: (list :select OBJ "field")     — Go-specific tag

The selector shape is a kit gap — lib/guest/ast.sx ships ast-app but
no ast-select, despite `obj.field` being universal across Go, Rust,
Swift, TS, JS, Python, Ruby, Java, C#. Logged in Blockers; tagging
[proposes-ast]. Worth promoting on the next nominally-typed guest.

parse 49/49, total 178/178.

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

lib/go/parse.sx

@@ -64,6 +64,72 @@
               (= ty "ident")
               (do (gp-advance!) (ast-var v))
               :else nil))))
+      (define
+        gp-parse-call-args
+        ;; Parse comma-separated args inside (...). Caller has already
+        ;; consumed the opening "(". Consumes the closing ")".
+        ;; Returns a list of argument AST nodes.
+        (fn
+          ()
+          (let ((args (list)))
+            (cond
+              (and (= (gp-tok-type) "op") (= (gp-tok-value) ")"))
+              (do (gp-advance!) args)
+              :else
+              (do
+                (let ((first (gp-parse-expr 1)))
+                  (when (not (= first nil)) (append! args first)))
+                (define
+                  gp-args-rest
+                  (fn
+                    ()
+                    (cond
+                      (and (= (gp-tok-type) "op") (= (gp-tok-value) ","))
+                      (do
+                        (gp-advance!)
+                        (let ((arg (gp-parse-expr 1)))
+                          (when (not (= arg nil)) (append! args arg)))
+                        (gp-args-rest))
+                      (and (= (gp-tok-type) "op") (= (gp-tok-value) ")"))
+                      (gp-advance!)
+                      :else nil)))
+                (gp-args-rest)
+                args)))))
+      (define
+        gp-parse-postfix
+        ;; Left-associative postfix loop on top of gp-parse-primary:
+        ;;   x.field    →  (list :select x "field")  — Go-specific node,
+        ;;                 no kit shape covers selector access
+        ;;   f(args...) →  (ast-app f args)          — canonical
+        (fn
+          ()
+          (let ((base (gp-parse-primary)))
+            (gp-postfix-loop base))))
+      (define
+        gp-postfix-loop
+        (fn
+          (base)
+          (cond
+            (= base nil) nil
+            :else
+            (let ((tok (gp-cur)))
+              (cond
+                (and (= (get tok :type) "op") (= (get tok :value) "."))
+                (do
+                  (gp-advance!)
+                  (let ((field-tok (gp-cur)))
+                    (cond
+                      (= (get field-tok :type) "ident")
+                      (do
+                        (gp-advance!)
+                        (gp-postfix-loop
+                          (list :select base (get field-tok :value))))
+                      :else base)))
+                (and (= (get tok :type) "op") (= (get tok :value) "("))
+                (do
+                  (gp-advance!)
+                  (gp-postfix-loop (ast-app base (gp-parse-call-args))))
+                :else base)))))
       (define
         gp-unary-ops
         ;; Go spec § Operators: prefix unary, all higher precedence than
@@ -84,7 +150,7 @@
                   (cond
                     (= operand nil) nil
                     :else (ast-app (ast-var (get tok :value)) (list operand)))))
-              :else (gp-parse-primary)))))
+              :else (gp-parse-postfix)))))
       (define
         gp-parse-expr
         (fn

lib/go/scoreboard.json

@@ -1,10 +1,10 @@
 {
   "language": "go",
-  "total_pass": 166,
+  "total_pass": 178,
-  "total": 166,
+  "total": 178,
   "suites": [
     {"name":"lex","pass":129,"total":129,"status":"ok"},
-    {"name":"parse","pass":37,"total":37,"status":"ok"},
+    {"name":"parse","pass":49,"total":49,"status":"ok"},
     {"name":"types","pass":0,"total":0,"status":"pending"},
     {"name":"eval","pass":0,"total":0,"status":"pending"},
     {"name":"runtime","pass":0,"total":0,"status":"pending"},

lib/go/scoreboard.md

@@ -1,11 +1,11 @@
 # Go-on-SX Scoreboard
 
-**Total: 166 / 166 tests passing**
+**Total: 178 / 178 tests passing**
 
 |  | Suite | Pass | Total |
 |---|---|---|---|
 | ✅ | lex | 129 | 129 |
-| ✅ | parse | 37 | 37 |
+| ✅ | parse | 49 | 49 |
 | ⬜ | types | 0 | 0 |
 | ⬜ | eval | 0 | 0 |
 | ⬜ | runtime | 0 | 0 |

lib/go/tests/parse.sx

@@ -172,6 +172,76 @@
     (ast-var "+")
     (list (ast-var "a") (ast-app (ast-var "-") (list (ast-var "b"))))))
 
+(go-parse-test
+  "call: f() (no args)"
+  (go-parse "f()")
+  (ast-app (ast-var "f") (list)))
+
+(go-parse-test
+  "call: f(x)"
+  (go-parse "f(x)")
+  (ast-app (ast-var "f") (list (ast-var "x"))))
+
+(go-parse-test
+  "call: f(x, y, z)"
+  (go-parse "f(x, y, z)")
+  (ast-app (ast-var "f") (list (ast-var "x") (ast-var "y") (ast-var "z"))))
+
+(go-parse-test
+  "call: f(1, 2)"
+  (go-parse "f(1, 2)")
+  (ast-app (ast-var "f") (list (ast-literal "1") (ast-literal "2"))))
+
+(go-parse-test
+  "call: f(a + b) — arg can be a binary expr"
+  (go-parse "f(a + b)")
+  (ast-app
+    (ast-var "f")
+    (list (ast-app (ast-var "+") (list (ast-var "a") (ast-var "b"))))))
+
+(go-parse-test
+  "call: f(g(x)) — nested"
+  (go-parse "f(g(x))")
+  (ast-app
+    (ast-var "f")
+    (list (ast-app (ast-var "g") (list (ast-var "x"))))))
+
+(go-parse-test
+  "select: x.y"
+  (go-parse "x.y")
+  (list :select (ast-var "x") "y"))
+
+(go-parse-test
+  "select: x.y.z (chained left-assoc)"
+  (go-parse "x.y.z")
+  (list :select (list :select (ast-var "x") "y") "z"))
+
+(go-parse-test
+  "method: obj.method()"
+  (go-parse "obj.method()")
+  (ast-app (list :select (ast-var "obj") "method") (list)))
+
+(go-parse-test
+  "method: obj.method(x, y)"
+  (go-parse "obj.method(x, y)")
+  (ast-app
+    (list :select (ast-var "obj") "method")
+    (list (ast-var "x") (ast-var "y"))))
+
+(go-parse-test
+  "postfix: -f(x) → unary applies after call"
+  (go-parse "-f(x)")
+  (ast-app
+    (ast-var "-")
+    (list (ast-app (ast-var "f") (list (ast-var "x"))))))
+
+(go-parse-test
+  "postfix: f(x) + 1 → call binds tighter than binary +"
+  (go-parse "f(x) + 1")
+  (ast-app
+    (ast-var "+")
+    (list (ast-app (ast-var "f") (list (ast-var "x"))) (ast-literal "1"))))
+
 (go-parse-test "non-primary: '+'" (go-parse "+") nil)
 
 (go-parse-test "non-primary: empty" (go-parse "") nil)

plans/go-on-sx.md

@@ -163,7 +163,10 @@ Progress-log line → push `origin/loops/go`.
 - [x] Unary operators (`+x`, `-x`, `!x`, `^x`, `*p`, `&v`, `<-ch`).
       `gp-parse-unary` recursive, sits between `gp-parse-expr` and
       `gp-parse-primary`; right-associative chains (`!!x`).
-- [ ] Function calls `f(a, b)` and member access `x.field`.
+- [x] Function calls `f(a, b)` (canonical `ast-app`) and member access
+      `x.field` (Go-specific `(list :select OBJ "field")` — the AST kit
+      doesn't ship a selector node; this is a sister-plan-static-types
+      data point about what the canonical AST is missing).
 - [ ] Index `x[i]` and slice `x[a:b]`/`x[a:b:c]`.
 - [ ] Type assertion `v.(T)`.
 - [ ] Type expressions: basic, slice `[]T`, array `[N]T`, map `map[K]V`,
@@ -178,7 +181,7 @@ Progress-log line → push `origin/loops/go`.
       assign, short-decl `:=`, send `ch <- v`, recv `<-ch`.
 - [ ] End-to-end: hello-world, fibonacci, FizzBuzz, goroutine ping-pong,
       struct + method.
-- **Acceptance:** parse/ suite at 80+ tests. Current: 37/37.
+- **Acceptance:** parse/ suite at 80+ tests. Current: 49/49.
 
 ### Phase 3 — Bidirectional type checker, MVP (`lib/go/types.sx`) ⬜
 - **Independent implementation.** Do NOT use lib/guest/static-types-
@@ -414,6 +417,19 @@ Every commit ends its message with a chisel note in brackets:
 
 ## Blockers
 
+### Kit-gap proposals against `lib/guest/ast.sx`
+
+Observed from building the Go parser:
+
+1. **No selector / field-access node.** `obj.field` is a universal shape
+   across nominally-typed languages — Go, Rust, Swift, TS, JS, Python,
+   Ruby, Java, C#. The kit ships `ast-app` (function application) but
+   not `ast-select`. We rolled `(list :select OBJ "field")` locally as
+   a Go-specific tag. Worth promoting once a second consumer hits the
+   same need (likely immediately — almost every guest needs it).
+
+Minimal repro: see `lib/go/parse.sx#gp-parse-postfix` (`.` branch).
+
 ### Kit-gap proposals against `lib/guest/lex.sx`
 
 Observed from building the Go tokenizer. Not blocking Phase 2; surfaced
@@ -437,6 +453,15 @@ 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 2 cont.: postfix forms — function calls `f(a, b)`
+  via canonical `ast-app`, and member access `x.field` via Go-specific
+  `(list :select OBJ "field")`. The AST kit has no selector node;
+  logged in Blockers as `[proposes-ast]` — every nominally-typed guest
+  will hit the same gap, worth promoting on the next consumer. Postfix
+  loop sits between unary and primary so calls bind tighter than unary
+  (`-f(x)` = `-(f(x))`). Covers nested calls, chained selectors,
+  methods `obj.m(x)`, mixed precedence. +12 tests, parse 49/49, total
+  178/178. `[consumes-ast proposes-ast]`.
 - 2026-05-27 — Phase 2 cont.: unary prefix operators (`+`, `-`, `!`, `^`,
   `*`, `&`, `<-`). `gp-parse-unary` is recursive (`!!x`) and sits between
   `gp-parse-expr` and `gp-parse-primary` so unary always binds tighter