Hojun-Cho
b787641ef9
Wwstage matchscrutt now mirrors cstage's typed-AST scrutinee-type lookup for module-qualified mod.fn(...) callees, restoring per-arm tag dispatch on cross-module shadowed-name 4-arm matches. Class A runtime miscompile, silent across collectfnrets shadowing — was the 8th unmask of session 5. Pre-fix: wwstage's matchscrutt N_DOT branch (cgenutil.ww:2061) called `fnretlookup(c, callee.str)` — name-only resolution. collectfnrets prepends to c.fnrets, so when a caller fn (e.g. lib/strings's `next`) shadows a callee fn-name (utf8's `next`), the prepend chain has the caller's narrower tagged return at the head. matchscrutt then resolved the scrutinee type to the WRONG tagged shape, and variantindex lookups for arms past the shadowing caller's variant count returned -1 → want=0 → match-arm `CMPQ $0, AX` for arms 2 and 3 on a (rune | done | more | invalid) probe. Effect: arms 2/3 silently unreachable even when the runtime tag matched, falling through to default. Cstage gets the scrutinee type via the checker-set callee type on the N_DOT node, so picks the correct utf8.next return shape. Polarity catalog: wwstage UNDER — fnretlookup missing module- preferring discipline. **Third leaf in the same trio**: #27 (aliaslookupmod), #28 (fnparamslookupmod), #31 (fnretlookupmod). Pattern is recurring; full graduation of all leaf-name lookups to same-module-first is a candidate for STATUS-3 task #1 variant-widen consolidation refactor (deferred to next session opener per rob). Fix: new fnretlookupmod helper in cgen.ww (same-module-first walk, fallback to existing first-match — cell-for-cell mirror of fnparamslookupmod from #28). matchscrutt N_DOT branch extracts `cmod` from callee.lhs.str and routes through the helper. Other 13 fnretlookup callsites untouched per #28's "fix only what has a real consumer" discipline. fnret.fmod field + collectfnrets f.fmod assignment already landed in #28. Surfaced by lib/strings commit-2 pre-flight: probe iter+next shape calls utf8.next; the probe's own `fn next` shadows utf8.next at the c.fnrets head. Bootstrap-stable because no selfhost-corpus path shadows a fn name across modules with a wider tagged return on the shadowed side; lib/strings.iter pulling utf8.next under wwstage was the first exerciser. Filed follow-up (NOT in scope here): #32 wwstage runtime stomp on utf8.next via *iterator caller — separate Class A surfaced by 929 direct utf8.next regression row design. #31's fix is correct in isolation; #32 blocks lib/strings commit 2 (#30). Tests: - 728_match_4arm_cross_module pins distinct CMPQ $K, AX tags in TEXT b.next via bitmap covering [0..arms), robust to arm ordering. Three cross-module shadowed-name shapes × cmp -s byte-id. Sentinel-flip-verified: revert fnretlookupmod route → 3/6 wwstage fixtures fail "arm K repeats tag $0 (collapse)". - 929_match_4arm_cross_module_run runtime-pins 6 rows × 2 stages per-arm exit-code shape: 3/4/5/6-arm boundary, mixed (i32|str|rune|u8), reverse arm-order in match source. Confirms bug follows fnretlookup-resolved type, not match source order. 102/102 ok. 995_self_rebuild stays green (ww2==ww3==ww4 byte-id).