wcc/cgen: route same-type tagged-cast return through the widener (wwstage align to cstage)
A same-type tagged cast return (`return x: u`, u == fnret) emitted tag=0 (a 2nd-variant value returned the wrong payload). Route it through the widener (needswiden when N_CAST && ru1==fu1, beside S1's ru1!=fu1) which peels the identity cast internally -> correct; same-type non-cast stays on the passthrough. Byte-id-neutral. test/wcc/837.
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190
test/wcc/837_idcast_tagged_return.c
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190
test/wcc/837_idcast_tagged_return.c
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/*
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* 837_idcast_tagged_return — S3 / #35: a SAME-TYPE tagged CAST in a RETURN
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* (`fn f() u = { ...; return v: u; }` where v: u — an identity cast).
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* ken2 spec .ai/ken2-family-spec.md (S3 section). Category A, CORRECTNESS
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* (widen-route), proven byte-id with cstage.
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*
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* ww's cgreturn keyed the tagged passthrough on rhs.kind; an N_CAST was
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* uncovered, so the same-type cast fell to the scalar-shuffle fast-path and
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* synthesised tag 0 — SILENT on any non-variant-0 value (a bool boxed as the
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* int variant: ran the int arm -> 70, want 11). cstage routes the N_CAST
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* through the scratch-widener (the N_CAST defeats its srcreg passthrough),
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* which peels the identity cast internally (cg_widen_tagged_store /
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* cg_tagged_castpeel). The fix adds the same-type N_CAST guard to cgreturn's
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* needswiden block so ww takes the widen route too — NOT a top-level peel,
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* which would reroute a call/dot source to passthrough and break byte-id.
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*
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* row | shape | want
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* -------------+----------------------------------------+------
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* S3_idcast | return x: u (x: u, 2nd-variant bool) | 11
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* S3_nocast | return x (same value, no cast) | 11
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* S3_intcast | return x: u (x: u, variant-0 int=7) | 7
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*
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* The 2nd-variant (bool) value is mandatory: a variant-0 (int) value boxes to
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* tag 0 coincidentally right (the S1 trap). S3_nocast pins the no-cast route
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* unchanged; S3_intcast pins the cast route on a variant-0 value.
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*
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* BYTE-ID: NEUTRAL. The newly-covered shape (same-type tagged CAST in return)
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* is non-bootstrap — had the bootstrap contained it the byte-id gate would
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* already be RED (pre-fix ww emitted tag-0 scalar-shuffle, cstage the
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* scratch-widen). 990-997 untouched.
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include <sys/stat.h>
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#include <sys/wait.h>
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static int
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runwait(const char *cmd)
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{
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int rc = system(cmd);
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if (rc == -1) return -1;
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if (WIFEXITED(rc)) return WEXITSTATUS(rc);
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return -1;
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}
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struct row { const char *label; const char *src; int want; };
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static const struct row rows[] = {
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/* S3 — same-type tagged CAST in return, 2nd-variant (bool) value.
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* Pre-fix ww ran the int arm (70); now the widen route boxes tag 1. */
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{ "S3_idcast",
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"package main;\n"
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"type u = (int | bool | str);\n"
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"fn f() u = { let x: u = true; return x: u; };\n"
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"export fn main() i32 = {\n"
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"\tmatch (f()) {\n"
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"\tcase let n: int => return 70;\n"
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"\tcase let b: bool => return 11;\n"
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"\tcase let s: str => return 22;\n"
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"\t};\n"
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"\treturn 99;\n"
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"};\n",
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11 },
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/* S3 — no-cast control: identical value, plain return. Pins the
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* forwardtagged/passthrough route unchanged. */
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{ "S3_nocast",
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"package main;\n"
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"type u = (int | bool | str);\n"
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"fn f() u = { let x: u = true; return x; };\n"
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"export fn main() i32 = {\n"
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"\tmatch (f()) {\n"
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"\tcase let n: int => return 70;\n"
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"\tcase let b: bool => return 11;\n"
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"\tcase let s: str => return 22;\n"
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"\t};\n"
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"\treturn 99;\n"
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"};\n",
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11 },
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/* S3 — cast route on a variant-0 (int) value: the widen route must
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* box tag 0 and carry the payload (7), not just coincidentally land
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* on tag 0. */
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{ "S3_intcast",
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"package main;\n"
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"type u = (int | bool | str);\n"
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"fn f() u = { let x: u = 7; return x: u; };\n"
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"export fn main() i32 = {\n"
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"\tmatch (f()) {\n"
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"\tcase let n: int => return n: i32;\n"
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"\tcase let b: bool => return 11;\n"
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"\tcase let s: str => return 22;\n"
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"\t};\n"
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"\treturn 99;\n"
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"};\n",
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7 },
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};
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static int
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run_driver(const char *driver, const struct row *r, int i)
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{
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char src[64], tmpdir[64], cmd[1024];
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snprintf(src, sizeof src, "/tmp/idc_%d_%d.ww", getpid(), i);
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snprintf(tmpdir, sizeof tmpdir, "/tmp/idc_%d_d_%d", getpid(), i);
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FILE *f = fopen(src, "wb");
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if (!f) return -1;
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fputs(r->src, f);
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fclose(f);
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mkdir(tmpdir, 0755);
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snprintf(cmd, sizeof cmd, "cd %s && %s build %s 2>/dev/null",
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tmpdir, driver, src);
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if (runwait(cmd) != 0) {
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fprintf(stderr, "row[%s]: build via %s failed\n",
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r->label, driver);
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unlink(src); rmdir(tmpdir);
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return -1;
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}
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const char *base = strrchr(src, '/');
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base = base ? base + 1 : src;
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char outbin[128];
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snprintf(outbin, sizeof outbin, "%s/%s", tmpdir, base);
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char *dot = strrchr(outbin, '.');
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if (dot && strcmp(dot, ".ww") == 0) *dot = '\0';
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int got = runwait(outbin);
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unlink(src); unlink(outbin); rmdir(tmpdir);
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return got;
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}
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int
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main(void)
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{
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const char *bin = getenv("BIN");
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if (!bin) bin = "out/bin";
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char absbin[1024];
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if (bin[0] != '/') {
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char cwd[1024];
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if (getcwd(cwd, sizeof cwd) == NULL) return 1;
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snprintf(absbin, sizeof absbin, "%s/%s", cwd, bin);
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bin = absbin;
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}
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char cdrv[1024];
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snprintf(cdrv, sizeof cdrv, "%s/ww", bin);
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char wdrv[1024];
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snprintf(wdrv, sizeof wdrv, "%s/ww_ww", bin);
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struct { const char *name; const char *path; int gated_on_existence; }
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drivers[] = {
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{ "cstage", cdrv, 0 },
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{ "wwstage", wdrv, 1 },
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{ NULL, NULL, 0 },
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};
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int n = (int)(sizeof rows / sizeof rows[0]);
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int total = 0, fail = 0;
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for (int d = 0; drivers[d].name; d++) {
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if (drivers[d].gated_on_existence
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&& access(drivers[d].path, X_OK) != 0) {
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fprintf(stderr, "idcast_tagged_return: skip %s (no %s)\n",
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drivers[d].name, drivers[d].path);
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continue;
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}
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for (int i = 0; i < n; i++) {
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int got = run_driver(drivers[d].path, &rows[i], i);
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total++;
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if (got != rows[i].want) {
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fprintf(stderr,
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"idcast_tagged_return[%s][%s]: exit=%d want=%d\n",
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drivers[d].name, rows[i].label,
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got, rows[i].want);
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fail++;
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}
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}
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}
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if (fail) {
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fprintf(stderr,
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"idcast_tagged_return: %d/%d fixtures failed\n", fail, total);
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return 1;
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}
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printf("idcast_tagged_return: %d/%d ok\n", total, total);
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return 0;
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}
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