test: migrate 802_lenidx to @test + runww rejects, retire C twin (fold-3)

#19 len/index family: value rows -> test/lang/lenidx_test.ww (primitive-only asserts), 3 reject (callres/sliceexpr/strlit) -> runww //ww:error dual-stage carriers. byteid floor 52->53.

test/lang/lenidx_test.ww

@@ -0,0 +1,139 @@
+// lenidx_test — the `len()` builtin over a non-IDENT operand shape (#19, then
+// the C5 sweep #10 F2 + #41 FA2/FB1), migrated from test/wcc/802_lenidx_run.c.
+// `len(xs[i])` / `len(*p)` / `len(s.field)` etc. once fell to a bare cgexpr
+// fallback that left AX = the slice/str DATA POINTER, so len() returned the
+// PTR as the length — silent ptr-garbage, byte-identical in BOTH stages (the
+// bootstrap corpus never indexes-then-len()s an element, so byte-id was
+// blind). The fix routes every place-resolvable operand through one uniform
+// header-place arm (.len at place+8) in both stages; non-place operands
+// (string literal, slicing expr, call result) now die LOUD (rule 7) — those
+// three are the runww reject carriers. The empty/zero rows are the strongest
+// pins: a leaked ptr is nonzero, so `len(empty) == 0` catches the regression
+// where a bare exit code couldn't. PRIMITIVE-only asserts (no fmt/strconv) so
+// a co-miscompile in the assert path cannot mask the bug. The .len/.ptr
+// pseudo-field control pins that the fix left the already-correct field paths
+// untouched. T2 keeps cs==ww (the #19 lineage: len of an INDEXED element is
+// exactly where cs!=ww would surface).
+
+package lenidx_test;
+
+// global [N]str table — the exact #19 repro operand (static-init str array,
+// #18 family); referenced from several rows to keep the global codegen path.
+let t: [3]str = ["a", "bcd", ""];
+
+type S = struct { pad: i64, name: str };
+
+@test fn lenidx_arrtab_mid() void = {
+	// len(t[1]) == 3; pre-fix this returned a ptr low-byte, not 3.
+	assert(len(t[1]) == 3);
+};
+
+@test fn lenidx_arrtab_empty() void = {
+	// empty element: a leaked ptr is nonzero, len must be 0.
+	assert(len(t[2]) == 0);
+};
+
+@test fn lenidx_arrtab_first() void = {
+	// guards an off-by-one in the index scale.
+	assert(len(t[0]) == 1);
+};
+
+fn slen(xs: []str, i: i64) int = { return len(xs[i]): int; };
+
+@test fn lenidx_slice_param_sum() void = {
+	// len(xs[i]) over a []str slice ARG (callee-side shape), 1 + 3 + 0 == 4.
+	let arr: [3]str = ["a", "bcd", ""];
+	let xs: []str = arr;
+	assert(slen(xs, 0) + slen(xs, 1) + slen(xs, 2) == 4);
+};
+
+@test fn lenidx_neg_control_field_agree() void = {
+	// the `.len` pseudo-field on the same indexed element must agree with
+	// len(), AND `.ptr` must still deref to the first byte — the fix must
+	// leave the already-correct .len/.ptr field paths untouched.
+	assert(len(t[1]) == t[1].len);
+	let p: *u8 = t[1].ptr;
+	assert(*p == 'b');
+	assert(len(t[1]) == 3);
+};
+
+fn derefn(p: *[]i64) int = { return len(*p): int; };
+
+@test fn lenidx_deref_param() void = {
+	// len(*p) through a *[]T PARAM (FB1) loaded the header's word 0 (the
+	// data pointer) as the length.
+	let xs: []i64 = [10, 20, 30];
+	assert(derefn(&xs) == 3);
+};
+
+@test fn lenidx_deref_local() void = {
+	let xs: []i64 = [10, 20, 30];
+	let p: *[]i64 = &xs;
+	assert(len(*p) == 3);
+};
+
+@test fn lenidx_deref_empty() void = {
+	// EMPTY-slice deref: the off-by-header bug returns .ptr (nonzero),
+	// len() must say 0 — only a non-exit primitive assert pins this.
+	let xs: []i64 = [1];
+	let ys: []i64 = xs[0:0];
+	let p: *[]i64 = &ys;
+	assert(len(*p) == 0);
+};
+
+@test fn lenidx_deref_chain() void = {
+	// chained deref len(**pp) — the resolver spine must recurse both hops.
+	let xs: []i64 = [10, 20, 30];
+	let p: *[]i64 = &xs;
+	let pp: **[]i64 = &p;
+	assert(len(**pp) == 3);
+};
+
+@test fn lenidx_idx_field() void = {
+	// len(xs[i].field) (F2) — N_DOT over an N_INDEX base matched no arm.
+	let xs: [2]S = [S{ pad = 1, name = "a" }, S{ pad = 2, name = "bcde" }];
+	assert(len(xs[1].name) == 4);
+};
+
+fn derefidxn(p: *[]S, i: i64) int = { return len((*p)[i].name): int; };
+
+@test fn lenidx_deref_idx_field() void = {
+	// full deref spine: len((*p)[i].field).
+	let arr: [2]S = [S{ pad = 1, name = "a" }, S{ pad = 2, name = "bcde" }];
+	let xs: []S = arr;
+	assert(derefidxn(&xs, 1) == 4);
+};
+
+fn derefidxcn(p: *[]S, i: i64) int = { return len((*p)[i + 1].name): int; };
+
+@test fn lenidx_deref_idx_field_computed() void = {
+	// computed index through the spine — i+1 must resolve like a constant.
+	let arr: [2]S = [S{ pad = 1, name = "a" }, S{ pad = 2, name = "bcde" }];
+	let xs: []S = arr;
+	assert(derefidxcn(&xs, 0) == 4);
+};
+
+@test fn lenidx_dot_field() void = {
+	// len(s.field) — the #235 arm's inner non-tuple fallback was ptr-garbage.
+	let s: S = S{ pad = 7, name = "abc" };
+	assert(len(s.name) == 3);
+};
+
+@test fn lenidx_ptr_field() void = {
+	// len(p.field) through a *struct.
+	let s: S = S{ pad = 7, name = "abc" };
+	let p: *S = &s;
+	assert(len(p.name) == 3);
+};
+
+@test fn lenidx_neutral_array_const() void = {
+	// neutrality control — the [N]T const fast-path still holds.
+	let a: [5]u8 = [1, 2, 3, 4, 5];
+	assert(len(a) == 5);
+};
+
+@test fn lenidx_neutral_ident_str() void = {
+	// neutrality control — the ident-str fast-path still holds.
+	let s: str = "abcd";
+	assert(len(s) == 4);
+};

test/wcc/802_lenidx_run.c

@@ -1,417 +0,0 @@
-/*
- * 802_lenidx_run — BUG #19. Runtime + cs==ww byte-id net for the
- * `len()` builtin applied to an INDEXED str/slice element (`len(xs[i])`).
- *
- * THE BUG (cstage == wwstage, BOTH wrong — shared gap, NOT rule-10):
- *   `len(t[i])` over a `[N]str` / `[]str` returned the element's .ptr,
- *   not its length. The len() builtin (cgen.c / cgenexpr.ww) had arms for
- *   an N_IDENT slice/str operand (.len at BP+off+8), a tuple-element N_DOT
- *   (#235), and a whole TY_ARRAY (→ alen) — but NOT an N_INDEX element.
- *   So `len(xs[i])` fell to the bare `cgexpr(arg)` fallback, which loads
- *   the str/slice element header via cgslicehdr leaving AX=.ptr, BX=.len,
- *   CX=.cap — and len() then returned AX (the ptr) AS the length. Same
- *   family as #14 (literal `.len` returned ptr) and #18 (shared static-init
- *   gap). byte-id was BLIND: no bootstrap source uses len(indexed-element)
- *   — the corpus indexes-then-reads .len explicitly or hardcodes lengths.
- *   CONTRAST (controls, all already correct): `t[i].len` pseudo-field,
- *   `t[i].ptr`, and scalar `len(s)` over a bare str variable.
- *
- * THE FIX (#19): add an N_INDEX arm to the len() builtin in BOTH stages —
- * `cgexpr(arg)` to materialise the element, then `MOVQ BX, AX` to shuffle
- * the len word (already in BX after cgslicehdr) into the result reg. The
- * same MOVQ BX,AX shape as #14's `.len` pseudo-field fix. Covers str AND
- * slice elements (both are 24B headers loaded by cgslicehdr).
- *
- * EACH ROW CARRIES BOTH DIMENSIONS (801 model):
- *   (a) cstage `ww build` + run, asserting the exit — pins that the
- *       converged asm is runtime-correct (real lengths, not ptr bytes).
- *   (b) w6c vs w6c_ww `.s` cmp — FAILS if the stages diverge (rule-10).
- *
- * GATE POLARITY: must stay GREEN. A wrong exit means len(indexed-element)
- * regressed back to returning the ptr; a byte-id FAIL means the stages
- * diverged.
- *
- * SCOPE NOTE: the []T (slice-of-slice) ELEMENT len shares the identical
- * codegen path (cgslicehdr → BX=len → MOVQ BX,AX) and is byte-id-clean in
- * isolation, but a clean runtime row for it is blocked by a SEPARATE
- * pre-existing bug — the `[2][]u8` array-literal → slice coercion emits a
- * divergent frame offset (cstage -24(BP) vs wwstage -40(BP)). That gap is
- * unrelated to len() (it reproduces with the `.len` pseudo-field too) and
- * is filed separately; these rows stay on str elements to avoid it.
- *
- * C5 SWEEP (#10 F2 + #41 FA2/FB1): the arm enumeration leaked FOUR
- * siblings over time (#235 → #19 → F2 → FA2/FB1) — every unhandled
- * operand shape fell to a bare cgexpr fallback returning the slice DATA
- * POINTER as the length, silent and byte-id-blind. The fix replaces the
- * fallback with ONE uniform header-place route (cgplaceaddr → .len at
- * place+8) in BOTH stages; non-place operands (string literal, slicing
- * expr, call result — all previously the same silent ptr-garbage) now
- * die LOUD (rule 7). Rows below pin: len(*p) param + local (FB1),
- * len(*p) on an EMPTY slice (a bare exit-code row can't pin this — the
- * garbage ptr's low byte masks to 0 — hence the branchy discriminator),
- * len(**pp) (chained deref, same resolver spine), len(xs[i].field)
- * (F2), len((*p)[i].field) incl. computed index, len(s.field) +
- * len(p.field) (struct-field cousins), the [N]T-const and ident-str
- * neutrality controls (global and tuple fast-paths have dedicated runs:
- * 797, 903), and reject rows with the exact rule-7 text. All
- * garbage/reject rows verified FAILING at the parent e481cb8 (the
- * per-row garbage exits below cite the d642017 probes; garbage is
- * frame-layout-dependent and drifts between commits — the FAILING
- * status is the pin, not the value).
- */
-#include <stdio.h>
-#include <stdlib.h>
-#include <string.h>
-#include <unistd.h>
-#include <sys/stat.h>
-#include <sys/wait.h>
-
-static int
-runwait(const char *cmd)
-{
-	int rc = system(cmd);
-	if (rc == -1) return -1;
-	if (WIFEXITED(rc)) return WEXITSTATUS(rc);
-	return -1;
-}
-
-/* reject != NULL marks a build-reject row: both stages must refuse the
- * source LOUD and the diagnostic must contain that exact text. */
-struct row { const char *label; const char *src; int want_exit;
-	const char *reject; };
-
-static const struct row rows[] = {
-	/* the exact #19 repro: a [3]str table, len(t[1]) == 3. Pre-fix this
-	 * returned a ptr low-byte (58), not 3. */
-	{ "arrtab_mid",
-	  "package main;\n"
-	  "let t: [3]str = [\"a\", \"bcd\", \"\"];\n"
-	  "export fn main() i32 = { return len(t[1]): i32; };\n", 3 },
-	/* empty-string element edge: len(t[2]) == 0 (a ptr would be nonzero). */
-	{ "arrtab_empty",
-	  "package main;\n"
-	  "let t: [3]str = [\"a\", \"bcd\", \"\"];\n"
-	  "export fn main() i32 = { return len(t[2]): i32; };\n", 0 },
-	/* first element: len(t[0]) == 1 — guards an off-by-one in the index
-	 * scale (a ptr or the wrong element would not be 1). */
-	{ "arrtab_first",
-	  "package main;\n"
-	  "let t: [3]str = [\"a\", \"bcd\", \"\"];\n"
-	  "export fn main() i32 = { return len(t[0]): i32; };\n", 1 },
-	/* []str slice parameter — the callee-side shape: len(xs[i]) over a
-	 * slice arg, summing all three lengths (1 + 3 + 0 == 4). */
-	{ "slice_param_sum",
-	  "package main;\n"
-	  "fn slen(xs: []str, i: i64) i32 = { return len(xs[i]): i32; };\n"
-	  "export fn main() i32 = {\n"
-	  "  let arr: [3]str = [\"a\", \"bcd\", \"\"];\n"
-	  "  let xs: []str = arr;\n"
-	  "  return slen(xs, 0) + slen(xs, 1) + slen(xs, 2);\n"
-	  "};\n", 4 },
-	/* NEGATIVE CONTROL: the `.len` pseudo-field on the same indexed
-	 * element must agree with len() (both == 3), AND `.ptr` must still
-	 * deref to the first byte ('b' == 98) — proving the fix left the
-	 * already-correct .len/.ptr field paths untouched. Returns 3 only if
-	 * len()==.len AND *.ptr=='b'. */
-	{ "neg_control_field_agree",
-	  "package main;\n"
-	  "let t: [3]str = [\"a\", \"bcd\", \"\"];\n"
-	  "export fn main() i32 = {\n"
-	  "  if (len(t[1]) != t[1].len) { return 91; };\n"
-	  "  let p: *u8 = t[1].ptr;\n"
-	  "  if (*p != 'b') { return 92; };\n"
-	  "  return len(t[1]): i32;\n"
-	  "};\n", 3 },
-
-	/* ---- C5 sweep rows (#10 F2 + #41 FA2/FB1) ---- */
-
-	/* FB1 exact repro: len(*p) through a *[]T PARAM loaded the slice
-	 * header's word 0 (the data pointer) as the length — silent
-	 * ptr-garbage (exit 48 at d642017), byte-id both stages. */
-	{ "deref_param",
-	  "package main;\n"
-	  "fn n(p: *[]i64) i32 = { return len(*p): i32; };\n"
-	  "export fn main() i32 = {\n"
-	  "  let xs: []i64 = [10, 20, 30];\n"
-	  "  return n(&xs);\n"
-	  "};\n", 3, NULL },
-	/* FB1, local-ptr variant (exit 64 at d642017). */
-	{ "deref_local",
-	  "package main;\n"
-	  "export fn main() i32 = {\n"
-	  "  let xs: []i64 = [10, 20, 30];\n"
-	  "  let p: *[]i64 = &xs;\n"
-	  "  return len(*p): i32;\n"
-	  "};\n", 3, NULL },
-	/* EMPTY-slice deref: the off-by-header bug returns .ptr (nonzero),
-	 * len() must say 0. A bare exit row can't pin it — the garbage
-	 * ptr's low byte happens to mask to 0 (verified at e481cb8) — so
-	 * branch on len()!=0 and return distinct codes. */
-	{ "deref_empty",
-	  "package main;\n"
-	  "fn n(p: *[]i64) i32 = {\n"
-	  "  if (len(*p) != 0) { return 9; };\n"
-	  "  return 42;\n"
-	  "};\n"
-	  "export fn main() i32 = {\n"
-	  "  let xs: []i64 = [1];\n"
-	  "  let ys: []i64 = xs[0:0];\n"
-	  "  return n(&ys);\n"
-	  "};\n", 42, NULL },
-	/* chained deref len(**pp) — the resolver spine must recurse through
-	 * BOTH hops (exit 208 garbage at e481cb8). */
-	{ "deref_chain",
-	  "package main;\n"
-	  "export fn main() i32 = {\n"
-	  "  let xs: []i64 = [10, 20, 30];\n"
-	  "  let p: *[]i64 = &xs;\n"
-	  "  let pp: **[]i64 = &p;\n"
-	  "  return len(**pp): i32;\n"
-	  "};\n", 3, NULL },
-	/* F2 exact repro: len(xs[i].field) — N_DOT over an N_INDEX base
-	 * matched no arm (the #235 arm requires an IDENT base) and fell to
-	 * the ptr-garbage fallback (exit 147 at d642017). */
-	{ "idx_field",
-	  "package main;\n"
-	  "type S = struct { pad: i64, name: str };\n"
-	  "export fn main() i32 = {\n"
-	  "  let xs: [2]S = [S{ pad = 1, name = \"a\" }, S{ pad = 2, name = \"bcde\" }];\n"
-	  "  return len(xs[1].name): i32;\n"
-	  "};\n", 4, NULL },
-	/* full deref spine: len((*p)[i].field) (exit 10 at d642017). */
-	{ "deref_idx_field",
-	  "package main;\n"
-	  "type S = struct { pad: i64, name: str };\n"
-	  "fn n(p: *[]S, i: i64) i32 = { return len((*p)[i].name): i32; };\n"
-	  "export fn main() i32 = {\n"
-	  "  let arr: [2]S = [S{ pad = 1, name = \"a\" }, S{ pad = 2, name = \"bcde\" }];\n"
-	  "  let xs: []S = arr;\n"
-	  "  return n(&xs, 1);\n"
-	  "};\n", 4, NULL },
-	/* computed index through the spine — cgplaceaddr cgexpr's the index
-	 * operand, so i+1 must resolve identically to a constant. */
-	{ "deref_idx_field_computed",
-	  "package main;\n"
-	  "type S = struct { pad: i64, name: str };\n"
-	  "fn n(p: *[]S, i: i64) i32 = { return len((*p)[i + 1].name): i32; };\n"
-	  "export fn main() i32 = {\n"
-	  "  let arr: [2]S = [S{ pad = 1, name = \"a\" }, S{ pad = 2, name = \"bcde\" }];\n"
-	  "  let xs: []S = arr;\n"
-	  "  return n(&xs, 0);\n"
-	  "};\n", 4, NULL },
-	/* struct-field cousins: len(s.field) (exit 75 at d642017) and
-	 * len(p.field) through a *struct (exit 87 at d642017) — the #235
-	 * arm's inner non-tuple fallback was the same ptr-garbage. */
-	{ "dot_field",
-	  "package main;\n"
-	  "type S = struct { pad: i64, name: str };\n"
-	  "export fn main() i32 = {\n"
-	  "  let s: S = S{ pad = 7, name = \"abc\" };\n"
-	  "  return len(s.name): i32;\n"
-	  "};\n", 3, NULL },
-	{ "ptr_field",
-	  "package main;\n"
-	  "type S = struct { pad: i64, name: str };\n"
-	  "export fn main() i32 = {\n"
-	  "  let s: S = S{ pad = 7, name = \"abc\" };\n"
-	  "  let p: *S = &s;\n"
-	  "  return len(p.name): i32;\n"
-	  "};\n", 3, NULL },
-	/* neutrality controls — already correct pre-sweep, pin that the
-	 * enumerated fast-paths ([N]T const fold, ident str) still hold. */
-	{ "neutral_array_const",
-	  "package main;\n"
-	  "export fn main() i32 = {\n"
-	  "  let a: [5]u8 = [1, 2, 3, 4, 5];\n"
-	  "  return len(a): i32;\n"
-	  "};\n", 5, NULL },
-	{ "neutral_ident_str",
-	  "package main;\n"
-	  "export fn main() i32 = {\n"
-	  "  let s: str = \"abcd\";\n"
-	  "  return len(s): i32;\n"
-	  "};\n", 4, NULL },
-	/* non-place operands: previously the same SILENT ptr-garbage
-	 * (strlit exit 40, slice-expr exit 48, call-result exit 0 at
-	 * master); now LOUD per rule 7 in both stages. */
-	{ "reject_strlit",
-	  "package main;\n"
-	  "export fn main() i32 = { return len(\"abc\"): i32; };\n",
-	  0, "#10/#41: len() operand shape not place-resolvable (rule-7)" },
-	{ "reject_sliceexpr",
-	  "package main;\n"
-	  "export fn main() i32 = {\n"
-	  "  let xs: []i64 = [10, 20, 30, 40];\n"
-	  "  return len(xs[1:3]): i32;\n"
-	  "};\n",
-	  0, "#10/#41: len() operand shape not place-resolvable (rule-7)" },
-	{ "reject_callres",
-	  "package main;\n"
-	  "fn mk() []i64 = {\n"
-	  "  let xs: []i64 = [10, 20, 30];\n"
-	  "  return xs;\n"
-	  "};\n"
-	  "export fn main() i32 = { return len(mk()): i32; };\n",
-	  0, "#10/#41: len() operand shape not place-resolvable (rule-7)" },
-	{ NULL, NULL, 0, NULL }
-};
-
-static int
-file_contains(const char *path, const char *needle)
-{
-	FILE *f = fopen(path, "rb");
-	if (!f) return 0;
-	char buf[8192];
-	size_t got = fread(buf, 1, sizeof buf - 1, f);
-	buf[got] = '\0';
-	fclose(f);
-	return strstr(buf, needle) != NULL;
-}
-
-static int
-slurp_eq(const char *a, const char *b)
-{
-	FILE *fa = fopen(a, "rb");
-	FILE *fb = fopen(b, "rb");
-	if (!fa || !fb) { if (fa) fclose(fa); if (fb) fclose(fb); return -1; }
-	int rc = 0;
-	for (;;) {
-		int ca = fgetc(fa);
-		int cb = fgetc(fb);
-		if (ca != cb) { rc = -1; break; }
-		if (ca == EOF) break;
-	}
-	fclose(fa); fclose(fb);
-	return rc;
-}
-
-int
-main(void)
-{
-	const char *bin = getenv("BIN");
-	if (!bin) bin = "out/bin";
-	char absbin[1024];
-	if (bin[0] != '/') {
-		char cwd[1024];
-		if (getcwd(cwd, sizeof cwd) == NULL) return 1;
-		snprintf(absbin, sizeof absbin, "%s/%s", cwd, bin);
-		bin = absbin;
-	}
-
-	char w6c[1100], w6c_ww[1100];
-	snprintf(w6c, sizeof w6c, "%s/w6c", bin);
-	snprintf(w6c_ww, sizeof w6c_ww, "%s/w6c_ww", bin);
-	if (access(w6c_ww, X_OK) != 0) {
-		fprintf(stderr, "lenidx: w6c_ww missing — cannot run the "
-		    "cs==ww byte-id gate\n");
-		return 1;
-	}
-
-	int n = 0, fail = 0;
-	for (int i = 0; rows[i].src; i++, n++) {
-		char src[64];
-		snprintf(src, sizeof src, "/tmp/wwli_%d_%d.ww", getpid(), i);
-		FILE *f = fopen(src, "wb");
-		if (f == NULL) { fail++; continue; }
-		fputs(rows[i].src, f);
-		fclose(f);
-
-		/* reject rows: BOTH stages must refuse with the exact rule-7
-		 * text — a silent accept means the ptr-garbage fallback is
-		 * back. */
-		if (rows[i].reject) {
-			char errf[64], cmd2[2048];
-			int bad = 0;
-			snprintf(errf, sizeof errf, "/tmp/wwli_%d_%d.err",
-			    getpid(), i);
-			snprintf(cmd2, sizeof cmd2, "%s -o /dev/null %s 2>%s",
-			    w6c, src, errf);
-			if (runwait(cmd2) == 0) {
-				fprintf(stderr, "row[%s]: w6c ACCEPTED a "
-				    "reject row\n", rows[i].label);
-				bad = 1;
-			} else if (!file_contains(errf, rows[i].reject)) {
-				fprintf(stderr, "row[%s]: w6c rejected but "
-				    "without the rule-7 text\n",
-				    rows[i].label);
-				bad = 1;
-			}
-			snprintf(cmd2, sizeof cmd2, "%s -o /dev/null %s 2>%s",
-			    w6c_ww, src, errf);
-			if (runwait(cmd2) == 0) {
-				fprintf(stderr, "row[%s]: w6c_ww ACCEPTED a "
-				    "reject row\n", rows[i].label);
-				bad = 1;
-			} else if (!file_contains(errf, rows[i].reject)) {
-				fprintf(stderr, "row[%s]: w6c_ww rejected but "
-				    "without the rule-7 text\n",
-				    rows[i].label);
-				bad = 1;
-			}
-			if (bad) fail++;
-			unlink(errf); unlink(src);
-			continue;
-		}
-
-		/* (a) cstage build + run in a scratch dir. */
-		char tmpdir[64];
-		snprintf(tmpdir, sizeof tmpdir, "/tmp/wwli_%d_d_%d", getpid(), i);
-		mkdir(tmpdir, 0755);
-
-		char cmd[2048];
-		snprintf(cmd, sizeof cmd, "cd %s && %s/ww build %s",
-		    tmpdir, bin, src);
-		if (runwait(cmd) != 0) {
-			fprintf(stderr, "row[%s]: cstage build failed\n",
-			    rows[i].label);
-			fail++;
-			unlink(src); rmdir(tmpdir);
-			continue;
-		}
-
-		char outbin[128];
-		const char *base = strrchr(src, '/');
-		base = base ? base + 1 : src;
-		snprintf(outbin, sizeof outbin, "%s/%s", tmpdir, base);
-		char *dot = strrchr(outbin, '.');
-		if (dot && strcmp(dot, ".ww") == 0) *dot = '\0';
-
-		int got = runwait(outbin);
-		if (got != rows[i].want_exit) {
-			fprintf(stderr, "row[%s]: cstage exit %d, want %d\n",
-			    rows[i].label, got, rows[i].want_exit);
-			fail++;
-		}
-		unlink(outbin); rmdir(tmpdir);
-
-		/* (b) cs==ww byte-id gate. */
-		char cs_s[64], ws_s[64];
-		snprintf(cs_s, sizeof cs_s, "/tmp/wwli_%d_%d_cs.s", getpid(), i);
-		snprintf(ws_s, sizeof ws_s, "/tmp/wwli_%d_%d_ww.s", getpid(), i);
-
-		snprintf(cmd, sizeof cmd, "%s -o %s %s 2>/dev/null", w6c, cs_s, src);
-		if (runwait(cmd) != 0) {
-			fprintf(stderr, "row[%s]: w6c failed\n", rows[i].label);
-			fail++; unlink(src); continue;
-		}
-		snprintf(cmd, sizeof cmd, "%s -o %s %s 2>/dev/null",
-		    w6c_ww, ws_s, src);
-		if (runwait(cmd) != 0) {
-			fprintf(stderr, "row[%s]: w6c_ww failed\n", rows[i].label);
-			fail++; unlink(src); unlink(cs_s); continue;
-		}
-		if (slurp_eq(cs_s, ws_s) != 0) {
-			fprintf(stderr, "row[%s]: cstage/wwstage .s DIFFER "
-			    "(rule-10 byte-id violation)\n", rows[i].label);
-			fail++;
-		}
-		unlink(src); unlink(cs_s); unlink(ws_s);
-	}
-
-	if (fail) {
-		fprintf(stderr, "%d/%d lenidx tests failed\n", fail, n);
-		return 1;
-	}
-	printf("lenidx: %d/%d ok (cstage run + cs==ww byte-id)\n", n, n);
-	return 0;
-}

test/wcc/data/lenidx_callres/case.ww

@@ -0,0 +1,13 @@
+//ww:error "len() operand shape not place-resolvable (rule-7)"
+// Lifted from test/wcc/802_lenidx_run.c reject row "reject_callres"
+// (#10/#41/rule-7): len() over a CALL RESULT (`mk()`) is not a
+// place-resolvable operand and MUST loud-fail in both stages, not silently
+// return the data pointer as the length. The substring is the shared
+// diagnostic body — byte-identical on both stages (no file:line, no cstage
+// "ww: " prefix — both differ cs vs ww).
+package main;
+fn mk() []i64 = {
+	let xs: []i64 = [10, 20, 30];
+	return xs;
+};
+export fn main() i32 = { return len(mk()): i32; };

test/wcc/data/lenidx_sliceexpr/case.ww

@@ -0,0 +1,12 @@
+//ww:error "len() operand shape not place-resolvable (rule-7)"
+// Lifted from test/wcc/802_lenidx_run.c reject row "reject_sliceexpr"
+// (#10/#41/rule-7): len() over a SLICING expression (`xs[1:3]`) is not a
+// place-resolvable operand and MUST loud-fail in both stages, not silently
+// return the data pointer as the length. The substring is the shared
+// diagnostic body — byte-identical on both stages (no file:line, no cstage
+// "ww: " prefix — both differ cs vs ww).
+package main;
+export fn main() i32 = {
+	let xs: []i64 = [10, 20, 30, 40];
+	return len(xs[1:3]): i32;
+};

test/wcc/data/lenidx_strlit/case.ww

@@ -0,0 +1,9 @@
+//ww:error "len() operand shape not place-resolvable (rule-7)"
+// Lifted from test/wcc/802_lenidx_run.c reject row "reject_strlit"
+// (#10/#41/rule-7): len() over a string LITERAL is not a place-resolvable
+// operand and MUST loud-fail in both stages, not silently return the data
+// pointer as the length. The substring is the shared diagnostic body —
+// byte-identical on both stages (no file:line, no cstage "ww: " prefix —
+// both differ cs vs ww).
+package main;
+export fn main() i32 = { return len("abc"): i32; };