Reject helpers checked only rc!=0, so a SEGFAULT (exit 139, or the
driver's "w6c failed" exit 1) counted as a clean reject -- a wwstage
crash could pass vacuously (it did, latently, on bodied bare-... pre
#11). Every reject row now captures stderr and requires the actual
diagnostic substring (rc!=0 AND strstr) across all 16 reject tests; a
crash emits no diagnostic, so it now fails. This is the
differential-reject backstop (#15): both stages must cleanly reject
with the expected message.
Two genuine cstage/wwstage diagnostic-body divergences are documented
inline via per-stage substrings, not papered over (845 tuple parse,
catA_f2 tuple arity); catalogued in #21.
The wwstage checker silently accepted enums with a non-integer storage type, duplicate members, or a non-constant member value; cstage already rejects all three (cmd/wcc/check.c:1000-1042). Add validateenummembers, a pure read-only diagnostic dispatched once per enum decl from resolvewalk's N_TENUM arm (check.ww:791, beside stampenumvals -- not the per-query recompute arms), mirroring the catB-7/14 validatestructfields pattern. Storage gate uses typeisint on the resolved tinfo (the exact type_isint mirror: chases TY_NAMED.under and TY_ENUM.sub, so an int-alias storage is accepted; raw-AST isinttypeast would not). Duplicate members: O(n^2) name walk. Unfoldable values reuse enumvalfold with until=member (forward-only). Emits via cerr + c.errs, no mutation, so valid-program codegen is unchanged and cstage==wwstage byte-id holds.
wwstage's value-fold message is intentionally generic where cstage's eval_enum_value gives per-reason text (enumvalfold returns a bool, not a reason); both reject. Documented at the site, filed as follow-up task #10.
Test: new table-driven both-stage reject test 850_enum_reject (non-int storage / duplicate member / forward-ref rows + a distinct-member control whose backward-ref value builds and runs). Full make test: 452 green incl. 990-997 byte-id.
