Files
ww/test/wcc
Hojun-Cho fddd167ce8 wcc/check: A7 honest-floor tagged-subset reject closes wide→narrow miscompile (wwstage)
wwstage's tagged→tagged subset-assign arm accepted all (lenient escape), silently miscompiling implicit wide→narrow: a (int|bool|str) holding a str, assigned to (int|bool), ran the int arm and read the str pointer as int. cstage rejects loud; this escape was the lone divergence.

Replace the escape with cstage's subset walk (src ⊆ dst): a src variant is covered iff typeeqast matches (structural — []u8/nested/primitives) OR both are N_TNAME with equal leaf names. The leaf bridge covers cross-module forwards where a callee's bare inline-union variant (utf8's `done`) meets the consumer's qualified `utf8.done` — raw typeeqast can't, and the escape was masking it for every forward. Mirrors casecovers (check.ww:4136). cstage untouched (align-up); spread-bearing unions keep the escape (#199b orthogonal).

Honest floor: leaf-only defers true module identity to #10 — a callee's defining module for an inline-union return is unrecoverable at check-time (the call node is gone; #211 fnretlookupmod is cgen-only). Retained divergence = cross-module same-leaf-collision over-accept (absent from bootstrap), documented at the site and filed as #10-A7 / census cat-A.

Test 989_tagged_subset_reject is table-driven with composition-discriminating rows: []u8 subset (typeeqast-only), bare↔qualified xmod forward (leaf-only), xmod named genuine-absence (reject). 352 green; w6c unchanged, w6c_ww 4b4496b8→4b316f01.
2026-06-10 00:22:22 +09:00
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