# sx `extern`/`export` + `#foreign` retirement — Checkpoint (FFI-linkage stream)

Companion to `current/PLAN-EXTERN-EXPORT.md` — one merged plan: **Part A** adds
`extern`/`export`, **Part B** migrates `#foreign` and purges `foreign`. Update after
every commit, one step at a time per the cadence rule.

## Last completed step
**Phase 0.0** (lock) — added `kw_extern`/`kw_export` to `token.Tag` + the
`keywords` `StaticStringMap` (beside `kw_callconv`, `token.zig:45,282`); classified
both as `ST.keyword` in the LSP `classifyToken` exhaustive switch
(`lsp/server.zig`); added `test "lex linkage keywords"` in `lexer.zig`. Suite green
(441 unit / 633 corpus, 0 fail). `extern`/`export` are now reserved words; corpus
sweep confirmed no `.sx` identifier used either (only comments + the unpinned
`issues/0030-*` repro, which doesn't run in the suite).

## Current state
Syntax decided + ratified: bare `extern`/`export`, postfix in the `callconv(.c)`
slot, `extern ⇒ callconv(.c)`, library separate. Touch-points mapped — token
`token.zig:45,282`; parser `1950,3669,316,425,1305`; lowering
`decl.zig:1123,387,2110,2382,2514`; IR/emit already capable (no codegen change).
Export gap = 4 lowering conditions. Part B `foreign` footprint to purge: 643 lines /
~57 identifiers in `src/` + 28 doc lines. End-state invariant: **zero `foreign`** in
the live tree (Phase 9.4 gate). Tokens exist (0.0); parser/AST not yet plumbed.

## Next step
**Phase 0.1** (lock) — `parseOptionalExternExport()` (mirror `parseOptionalCallConv`,
`parser.zig:3669`) + `ast.ExternExportModifier` enum + `FnDecl.extern_export` +
`VarDecl.is_extern`/`extern_name` fields; **parsed but not yet consumed**; unit AST
test. Then Phase 1 (`extern` working: 1.0 xfail accept postfix, 1.1 green lower via
`declareExtern`, 1.2 green rename + extern-global). See the plan's **"Kickoff
prompt"**. Stop at end of Phase 1.

## Open decisions
Part A ratified (bare / postfix / `⇒ callconv(.c)` / lib-separate). Part B (confirm
before Phase 9): runtime-class rename target — `Runtime*Class*` (recommended);
historical carve-out — keep `issues/*.md` provenance, gate the live tree only.

## Log
- (init) Plan written; FFI-linkage stream opened.
- (merge) Folded FOREIGN-MIGRATION in as Part B; deleted the split plan + checkpoint.
- (0.0) Added `kw_extern`/`kw_export` tokens + keyword-map entries + LSP keyword
  classification + `lex linkage keywords` test. Suite green; no identifier collisions
  in the corpus. `lock` commit.

## Known issues
None yet.