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selfhost/cmd/wcc: type-key tagged variant match (#66, Phase-N step 3)

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The user-ruled B-full semantic change: flip tagged-union variant matching
from surface-NAME to TYPE-identity (typeeq over tinfo.params), mirroring
cstage cg_variant_match (cmd/w6c/cgen.c:451). A cross-module `a.T` != `b.T`
and `type linerr=!str` != str are now distinguished by the per-decl TY_NAMED
pointer (Phase-N #64). ww has no type_assignable, so the untyped/loose arm
keeps the str/slice shape fallback (rule-10 align-down). The 5 helpers
(flatvariantidx, flatslicevariantidx, taggedvariantindex, cgtagvariantidx,
cgmatch dispatch) flip; nomem propagation (NAMED-name scan, no source value)
and the f64 widen arm (float-kind classification, no pattern node) are not
arm-by-value discrimination and stay name/kind-keyed.

The flip requires value nodes to carry nominal identity. exprtype's
N_STRUCTLIT arm stamped the flattened body, so `overflow{}` (overflow=!void)
got TY_VOID and missed its variant -- fixed to stamp the per-decl NAMED
(mktname(lhs.str) -> tinfofornode reuses the #64 NAMED build/cache, same ptr
the union variant resolved to), mirroring the N_CAST/N_IDENT arms + cstage.
Returns the body node unchanged (only e.type_ rides NAMED); struct-lit layout
is unaffected -- cgstructlitfill is structlookup(name)-keyed, never reads
NAMED.fields. The fix now hits all `T{}` stamps, kept byte-id by the #63/#65
structural-walker peels.

931_variant_typekey_run: table-driven, both stages, /tmp-isolated. Two rows
widen an alias-FIRST variant from a call (no surface name): `(linerr|str)`
str-via-call -> idx 1, `(ec|i32)` i32-via-call -> idx 1. Empirically
discriminating: FAILS pre-flip (wwstage falls to the leading-shape variant,
exit 10; cstage exit 0) and PASSES post-flip -- locking in the capability
byte-id can't reach (the corpus has no name-key/type-key-disagreeing
co-variant, which is why name-keying survived).

make test 134/134 (byte-id 990-997 green; 995 self-rebuild green).
This commit is contained in:
Hojun-Cho
2026-05-23 21:22:24 +09:00
parent 0fde4beeb4
commit 3036ba766d
8 changed files with 634 additions and 369 deletions
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23
selfhost/cmd/wcc/cgenstmt.ww
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@@ -667,7 +667,28 @@ fn cglet(c: *cgen, n: *node) void = {
emitline("\tJNE\t");
emitline(okl);
emitline("\n");
let nidx: i32 = flatvariantidx(c, c.fnret, "nomem");
// #66 Phase-N step 3: nomem propagation has no
// pattern node, so it can't ride the typeeq
// flatvariantidx path. cstage passes the ty_nomem
// singleton to cg_tag_for_variant; the wwstage cgen
// holds no tinfo singleton, so find the nomem
// variant by its NAMED name over tinfo.params.
let nidx: i32 = -1;
let nti: *tinfo = nil;
if (c.fnret != nil) { nti = c.fnret.type_: *tinfo; };
for (nti != nil && nti.kind == tykind.TY_NAMED) { nti = nti.under; };
if (nti != nil) { if (nti.kind == tykind.TY_TAGGED) {
let np: *tparam = nti.params;
let nidx2: i32 = 0;
for (np != nil) {
let nvt: *tinfo = np.type_;
if (nvt != nil) {
if (variantnamematch(nvt.name, "nomem")) { nidx = nidx2; break; };
};
np = np.tnext;
nidx2 += 1;
};
}; };
if (nidx < 0) { nidx = 1; };
emitline("\tMOVQ\t$");
emitint(nidx: i64);