From bb6eca6b918e24343c2e094ab7a402b2bd63c692 Mon Sep 17 00:00:00 2001
From: agra <alex@swipelab.co>
Date: Wed, 27 May 2026 12:09:04 +0300
Subject: [PATCH] =?UTF-8?q?ffi=20M5.A.next.1c.A:=20pack=20type=20rep=20?=
 =?UTF-8?q?=E2=80=94=20lock=20in=20parser=20rejection?=
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Next slice of the variadic heterogeneous type packs (`..$args`)
feature: type-system representation. Per the FFI cadence rule, this
commit locks in the parser-rejection behavior so the next commit's
type-rep extension surfaces as a behavior shift.

examples/154-pack-type-rep.sx uses `..$args` inside a `Closure(...)`
type expression — the pack-shape spelling used by impl headers like
`impl Into(Block) for Closure(..$args) -> $R`. Today's parser
recognizes `..$args` only at the parameter-list site (1b);
`parseTypeExpr`'s `Closure(...)` arm calls `parseTypeExpr` per
position and hits "expected type name" at the `..` token. Snapshot
captures the rejection at line 18, column 26.

Next commit (1c.B):
- Parser: `parseTypeExpr` Closure arm accepts `..$args` as the
  trailing pack marker. AST gets a `pack_name: ?[]const u8` (or
  equivalent) field on `ClosureTypeExpr`.
- types.zig: `FunctionInfo` / `ClosureInfo` gain `pack_start: ?u32`
  so the pack shape is distinct from any concrete arity in the
  type table. Hash/eql updated.
- type_bridge: `resolveClosureType` threads pack_start through.
- 154 flips green.

192/192 example tests + `zig build test` green.
---
 examples/154-pack-type-rep.sx         | 23 +++++++++++++++++++++++
 tests/expected/154-pack-type-rep.exit |  1 +
 tests/expected/154-pack-type-rep.txt  |  1 +
 3 files changed, 25 insertions(+)
 create mode 100644 examples/154-pack-type-rep.sx
 create mode 100644 tests/expected/154-pack-type-rep.exit
 create mode 100644 tests/expected/154-pack-type-rep.txt

diff --git a/examples/154-pack-type-rep.sx b/examples/154-pack-type-rep.sx
new file mode 100644
index 0000000..582d84e
--- /dev/null
+++ b/examples/154-pack-type-rep.sx
@@ -0,0 +1,23 @@
+// Variadic heterogeneous type packs — `..$args` — type-system
+// representation lock-in.
+//
+// Step 1c slice for the pack feature (see
+// ~/.claude/plans/lets-see-options-for-merry-dijkstra.md). Exercises
+// the parser's acceptance of `..$args` inside a `Closure(...)` type
+// expression — the pack-shape spelling used by impl headers like
+// `impl Into(Block) for Closure(..$args) -> $R`.
+//
+// Today's parser only accepts `..$args` in fn parameter lists (1b);
+// the same syntax inside a `Closure(...)` type expression hits
+// `expected type name` at the `..` token. This file pins that
+// rejection. The next commit teaches `parseTypeExpr`'s `Closure(...)`
+// arm + the type-table representation to carry the pack.
+
+#import "modules/std.sx";
+
+takes_cb :: (cb: Closure(..$args) -> $R) -> void { }
+
+main :: () -> s32 {
+    print("pack type rep ok\n");
+    return 0;
+}
diff --git a/tests/expected/154-pack-type-rep.exit b/tests/expected/154-pack-type-rep.exit
new file mode 100644
index 0000000..d00491f
--- /dev/null
+++ b/tests/expected/154-pack-type-rep.exit
@@ -0,0 +1 @@
+1
diff --git a/tests/expected/154-pack-type-rep.txt b/tests/expected/154-pack-type-rep.txt
new file mode 100644
index 0000000..a324bd9
--- /dev/null
+++ b/tests/expected/154-pack-type-rep.txt
@@ -0,0 +1 @@
+/Users/agra/projects/sx/examples/154-pack-type-rep.sx:18:26: error: expected type name