Hojun-Cho 3f4eeff7ff wcc: route is/as variant lookup through tinfo.params (#198) ...

checkisas walked the unflattened AST u.list via casevariantin (typeeqast
streq), so any variant introduced via a `...inner` spread was invisible
and rejected as "is/as: not a variant of operand". Repro:

    type rsh = (size | io.eof | ...io.error);
    let r: rsh = 42: size;
    if (r is io.underread) ...    -- pre-fix wwstage REJECTS

io.underread is in io.error.params, which tinfofornode splices into the
parent at L1827-1836, but the AST u.list still holds the single
`...io.error` entry that streq("io.underread", "io.error") rejects.

Route through flatvariantidxt — the same Phase-N helper #179 cgmatch
and #66 cgtagvariantidx already key off. Mirrors cstage cmd/wcc/check.c
:1662-1675 u->params + type_eq. Falls back to casevariantin AST walk
when tinfo isn't available (defensive — non-#198 path stays as-is).

project_tinfo_lossy_nominal: name-keying was the pre-Phase-N workaround
for tinfo lossy on nominal identity; typeeq inside flatvariantidxt now
handles NAMED ptr-id (#64), so the checker pair aligns with cgen on the
flattened-variant axis.

Closes the cgen-drain mini-cluster (#201 -> #199 -> #200 -> #198).

773_isas_spread_variant: 5 rows (spread_is_inline_variant,
direct_cross_mod_tagged, cross_mod_named_void, same_module_variant,
spread_as_inline_payload). Rows 2-4 byte-id; rows 1/5 skip byte-id due
to layout-asymmetry on `...wrapper` (cstage flattens at resolve_type,
wwstage computes maxsz off vt.size of the un-spliced alias) — sibling
not blocking the checker correctness fix.

2026-05-29 04:51:44 +09:00

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