ffi 1.11–1.13: #objc_call inside struct method / protocol / closure / generic

108/108 regression tests pass (+ffi-objc-call-09-in-construct,
+issue-0038 from the prior commit).

One trivial Obj-C call (`[obj hash]` returning NSUInteger) routed
through four sx surface constructs:

  1. struct method body          Probe.fetch
  2. protocol impl method body   impl Hashable for Probe
  3. closure value body          make_hasher
  4. generic function body       hash_through(recv: $T)

No new ABI shapes touched — pins that the `objc_msg_send` lowering
emits identical call shapes regardless of enclosing scope. Each
case validates the result `h_N == h_1` after threading `recv`
appropriately for each context.

The closure path reaches `recv` via a module-level global rather
than capturing the surrounding parameter — issue-0038 (prior
commit) documents the closure free-variable analyzer missing the
`FfiIntrinsicCall` node, with a clean workaround pinned.

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

@@ -0,0 +1,85 @@
+// Phase 1 steps 1.11–1.13 (PLAN-FFI.md): `#objc_call` call sites
+// embedded inside the sx surface constructs. None touch a new ABI
+// path — the lowering routes the call identically regardless of
+// the enclosing scope, and this test pins that lemma.
+//
+//   1. Struct method body                  Probe.fetch
+//   2. Protocol impl method body           impl Hashable for Probe
+//   3. Closure value body                  closure that calls hash
+//
+// 1.14 (separate test): `inline if OS == { case }` gating across
+// targets — verified by `tests/cross_compile.sh`.
+
+#import "modules/std.sx";
+#import "modules/compiler.sx";
+#import "modules/std/objc.sx";
+
+// ── 1. Struct method calling #objc_call ─────────────────────────────
+Probe :: struct {
+    receiver: *void = null;
+    fetch :: (self: *Probe) -> s64 {
+        #objc_call(s64)(self.receiver, "hash");
+    }
+}
+
+// ── 2. Protocol impl method ────────────────────────────────────────
+Hashable :: protocol {
+    sx_hash :: (self: *Self) -> s64;
+}
+
+impl Hashable for Probe {
+    sx_hash :: (self: *Probe) -> s64 {
+        #objc_call(s64)(self.receiver, "hash") * 2;
+    }
+}
+
+// ── 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"));
+}
+
+// ── 4. Generic function body — instantiated per call site ───────────
+hash_through :: (recv: $T) -> s64 {
+    p : *void = xx recv;
+    #objc_call(s64)(p, "hash");
+}
+
+main :: () -> s32 {
+    inline if OS == .macos {
+        ns_object := objc_getClass("NSObject".ptr);
+
+        p : Probe = .{ receiver = ns_object };
+
+        // 1. struct method
+        h1 := p.fetch();
+        print("fetch != 0   = {}\n", h1 != 0);
+
+        // 2. protocol method (doubles the raw hash; mostly checking
+        //    dispatch / arg threading, not the math)
+        h2 := p.sx_hash();
+        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();
+        h3 := hasher(0);
+        print("closure h3  = {}\n", h3 == h1);
+
+        // 4. generic function — instantiates with T = *void here
+        h4 := hash_through(ns_object);
+        print("generic h4  = {}\n", h4 == h1);
+    }
+    inline if OS != .macos {
+        print("skipped (not macos)\n");
+    }
+    0;
+}

tests/expected/ffi-objc-call-09-in-construct.exit

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

tests/expected/ffi-objc-call-09-in-construct.txt

@@ -0,0 +1,4 @@
+fetch != 0   = true
+protocol h2 = true
+closure h3  = true
+generic h4  = true