issue-0038 fixed: closure capture through FfiIntrinsicCall args

`collectCaptures` in `src/ir/lower.zig` was the closure free-variable
analyzer that decides which names from a closure body need to be
boxed into the env struct at lambda-build time. Its switch on AST
node kind enumerated every other shape (`.call`, `.if_expr`,
`.match_expr`, `.for_expr`, etc.) but no arm for `.ffi_intrinsic_call`,
so the trailing `else => {}` quietly dropped its `args[]` and
`return_type` walks. Names referenced inside `#objc_call(T)(recv,
"sel:", ...)` from a closure body never made it into the captures
list, so when lowering bound the closure scope from env, those names
came back as "unresolved".

The fix adds the missing arm — walk `return_type` and every `args[i]`
the same way `.call` walks `callee` + `args`.

Companion changes:
- `examples/issue-0038.sx` → `examples/103-ffi-closure-capture.sx`
  (out of the open-issue namespace; comment header tightened to
  describe the feature, not the historical bug).
- `examples/ffi-objc-call-09-in-construct.sx` drops the
  `g_hasher_recv` module-global workaround that was added for this
  bug — the closure now captures `recv` from `make_hasher`'s arg
  list normally.

examples/103-ffi-closure-capture.sx

@@ -0,0 +1,38 @@
+// Closure free-variable capture works through `FfiIntrinsicCall`
+// nodes — names referenced inside `#objc_call` / `#jni_call` /
+// `#jni_static_call` argument lists from inside a closure body are
+// recognized as captured variables and bound from the closure's env
+// struct at call time. `passthrough_works` is the baseline (normal
+// expression capture); `passthrough_via_objc_call` exercises the same
+// capture through an FFI intrinsic call's arg list.
+
+#import "modules/std.sx";
+#import "modules/compiler.sx";
+#import "modules/std/objc.sx";
+
+passthrough_works :: (recv: *void) -> Closure(s32) -> *void {
+    closure((d: s32) -> *void => recv);  // captures `recv` — fine
+}
+
+passthrough_via_objc_call :: (recv: *void) -> Closure(s32) -> s64 {
+    // Same `recv` capture, but inside `#objc_call(...)`'s arg list.
+    closure((d: s32) -> s64 => #objc_call(s64)(recv, "hash"));
+}
+
+main :: () -> s32 {
+    inline if OS == .macos {
+        f := passthrough_works(null);
+        p := f(0);
+        print("ok (passthrough works) = {}\n", p == null);
+
+        // Capture inside the `#objc_call` arg list.
+        ns_object := objc_getClass("NSObject".ptr);
+        g := passthrough_via_objc_call(ns_object);
+        h := g(0);
+        print("ok (passthrough via #objc_call) = {}\n", h != 0);
+    }
+    inline if OS != .macos {
+        print("skipped (not macos)\n");
+    }
+    0;
+}

examples/ffi-objc-call-09-in-construct.sx

@@ -34,14 +34,11 @@ impl Hashable for Probe {
 }
 
 // ── 3. Closure body invoking #objc_call ─────────────────────────────
-// Closure-captured `recv` isn't traced through the `#objc_call` AST
-// node by sema today, so we reach the receiver via a module-level
-// global. The lemma we lock here is that lowering routes the call
-// the same way inside a closure body as it does at top level.
-g_hasher_recv : *void = null;
-
-make_hasher :: () -> Closure(s32) -> s64 {
-    closure((dummy: s32) -> s64 => #objc_call(s64)(g_hasher_recv, "hash"));
+// The closure captures `recv` from its enclosing function and
+// references it inside the `#objc_call` arg list. Locked in by
+// `examples/103-ffi-closure-capture.sx`.
+make_hasher :: (recv: *void) -> Closure(s32) -> s64 {
+    closure((dummy: s32) -> s64 => #objc_call(s64)(recv, "hash"));
 }
 
 // ── 4. Generic function body — instantiated per call site ───────────
@@ -66,11 +63,9 @@ main :: () -> s32 {
         print("protocol h2 = {}\n", h2 == h1 * 2);
 
         // 3. closure (receives a dummy arg to keep the `Closure(T) -> R`
-        //    arity matching 35-closures.sx; recv comes via a global —
-        //    closure capture through `#objc_call` AST nodes isn't
-        //    traced by sema today and would error "unresolved").
-        g_hasher_recv = ns_object;
-        hasher := make_hasher();
+        //    arity matching 35-closures.sx; `recv` is captured from
+        //    `make_hasher`'s arg list and used inside the `#objc_call`).
+        hasher := make_hasher(ns_object);
         h3 := hasher(0);
         print("closure h3  = {}\n", h3 == h1);
 

examples/issue-0038.sx

@@ -1,47 +0,0 @@
-// Closure capture analysis doesn't trace into the `FfiIntrinsicCall`
-// AST node — identifiers used inside `#objc_call` / `#jni_call` /
-// `#jni_static_call` from a closure body aren't recognized as
-// captured variables. Surfaced when writing `ffi-objc-call-09-in-
-// construct.sx`.
-//
-// Reduced repro: capture in a closure body works fine for
-// "normal" expressions (see `passthrough_works`), but the same
-// capture inside `#objc_call`'s arg list trips
-// "unresolved: 'recv'" (see `passthrough_via_objc_call` — would
-// fail at parse time, so it's commented out).
-//
-// Likely fix: in the closure free-variable analyzer (sema.zig /
-// lower.zig), add a recursive arm for `ffi_intrinsic_call` that
-// visits `return_type` + every `args[i]` the same way the `.call`
-// arm walks `callee` + `args`.
-
-#import "modules/std.sx";
-#import "modules/compiler.sx";
-#import "modules/std/objc.sx";
-
-passthrough_works :: (recv: *void) -> Closure(s32) -> *void {
-    closure((d: s32) -> *void => recv);  // captures `recv` — fine
-}
-
-passthrough_via_objc_call :: (recv: *void) -> Closure(s32) -> s64 {
-    // Same `recv` capture, but inside `#objc_call(...)`.
-    closure((d: s32) -> s64 => #objc_call(s64)(recv, "hash"));
-}
-
-main :: () -> s32 {
-    inline if OS == .macos {
-        f := passthrough_works(null);
-        p := f(0);
-        print("ok (passthrough works) = {}\n", p == null);
-
-        // After the fix, capture in an FfiIntrinsicCall arg list works.
-        ns_object := objc_getClass("NSObject".ptr);
-        g := passthrough_via_objc_call(ns_object);
-        h := g(0);
-        print("ok (passthrough via #objc_call) = {}\n", h != 0);
-    }
-    inline if OS != .macos {
-        print("skipped (not macos)\n");
-    }
-    0;
-}

src/ir/lower.zig

@@ -5073,6 +5073,12 @@ pub const Lowering = struct {
             .defer_stmt => |ds| {
                 self.collectCaptures(ds.expr, param_names, captures);
             },
+            .ffi_intrinsic_call => |fic| {
+                self.collectCaptures(fic.return_type, param_names, captures);
+                for (fic.args) |arg| {
+                    self.collectCaptures(arg, param_names, captures);
+                }
+            },
             else => {},
         }
     }

tests/expected/103-ffi-closure-capture.exit

@@ -0,0 +1 @@
+0

tests/expected/103-ffi-closure-capture.txt

@@ -0,0 +1,2 @@
+ok (passthrough works) = true
+ok (passthrough via #objc_call) = true

tests/expected/issue-0038.exit

@@ -1 +0,0 @@
-1

tests/expected/issue-0038.txt

@@ -1 +0,0 @@
-/Users/agra/projects/sx/examples/issue-0038.sx:28:48: error: unresolved: 'recv'