docs(ffi-linkage): checkpoint — Phase 3.0 xfail logged

current/CHECKPOINT-EXTERN-EXPORT.md

@@ -5,7 +5,14 @@ Companion to `current/PLAN-EXTERN-EXPORT.md` — one merged plan: **Part A** add
 every commit, one step at a time per the cadence rule.
 
 ## Last completed step
-**Phase 2.2** (green) — **PHASE 2 COMPLETE.** `export` (define + expose) fully works:
+**Phase 3.0** (xfail) — `examples/1348-ffi-objc-extern-class.sx` exercises the new
+postfix-`extern` aggregate spelling (`NSObject :: #objc_class("NSObject") extern { … }`,
+the new way to write `#foreign #objc_class("NSObject") { … }`). RED: parser rejects
+`extern` after the `#objc_class(...)` directive (`expected '{'`). Green-state snapshots
+hand-authored (exit 0, stdout `extern-class dispatch ok`). Suite: 639 corpus / 443 unit,
+**1 fail (1348, the intended xfail)**. Step 3.1 wires parse+lowering to green it.
+
+### Prior: Phase 2.2 (green) — **PHASE 2 COMPLETE.** `export` (define + expose) fully works:
 external linkage + C ABI + no sx ctx + force-lowered root + optional `"csym"` rename.
 All four export-gap conditions filled in `decl.zig`: (i) `.external` linkage for
 `extern_export == .export_` on both define paths (`lowerFunctionBodyInto`,
@@ -40,11 +47,13 @@ gate). Examples: 1223 (extern bare fn), 1224 (extern fn rename), 1225 (extern ba
 global), 1226 (export bare fn, AOT), 1227 (export fn rename, AOT).
 
 ## Next step
-**Phase 3 — aggregates** (objc / jni runtime classes): `#objc_class("X") extern { … }`
+**Phase 3.1** (green) — wire the postfix `extern`/`export` aggregate path. `parseForeignClassDecl`
-(import) + `… export { … }` (define) parse alongside legacy `#foreign #objc_class`
+already consumes the directive + `("X")` + body; add an optional postfix-modifier slot
-(`parser.zig` `tryParseForeignClassPrefix`/`parseForeignClassDecl`); map postfix
+**after** the `)` and before the `{`: `extern`→reference (== `is_foreign`), `export`→
-`extern`→reference, `export`→define+register (`objc_class.zig`); per-runtime tests
+define+register (== no `#foreign`). Map the postfix modifier onto the same downstream
-(objc, jni). Then Phase 4 (interplay/diagnostics/docs + the A→B gate: unit test that
+`is_foreign` decision that `tryParseForeignClassPrefix` feeds, so `objc_class.zig` lowering
+is unchanged. Green 1348; add a jni postfix test + an `export` (defined-class) test for the
+per-runtime coverage. Then Phase 4 (interplay/diagnostics/docs + the A→B gate: unit test that
 `#foreign` and `extern`/`export` lower to identical IR) before Part B migration.
 
 **FUTURE MILESTONE — C→sx-by-name in JIT (`sx run`).** Investigated this session
@@ -131,6 +140,9 @@ historical carve-out — keep `issues/*.md` provenance, gate the live tree only.
   the body promotes into the C-named function (`define @triple_c`). sx-side call sites
   resolve via the same map (probe: 5*5→25). 1227 green (22); 1226 unregressed. Suite
   green (638/443). `green` commit. **PHASE 2 COMPLETE** — `export` fully works.
+- (3.0) Added `examples/1348-ffi-objc-extern-class.sx` (postfix `extern` on `#objc_class`,
+  new spelling of `#foreign #objc_class`). RED (parser: `expected '{'` after the
+  directive). Hand-authored green snapshots. `xfail` commit; 3.1 greens it.
 
 ## Known issues
 - **Workflow hazard (1.2):** an editor format-on-save (or `zig fmt`) clobbered the