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 sym carried an is_const flag (lib/ww/sym.ww) but wwstage never
set it at the let-install nor consumed it at assignment, so mutating
a `const` slipped through silently. Mirror cstage's two sites: set
is_const when n.op == TK_CONST at the local let-install (cmd/wcc/
check.c:2408) and reject an N_ASSIGN whose lhs ident resolves to an
is_const sym (cmd/wcc/check.c:1889-1896). cstage already rejected;
this aligns wwstage's w6c_ww UP. A bare `_` discard lvalue (empty
str) is skipped.
Regen w6c/wwdump combined.ww (checker embeds in both). Valid-program
codegen unchanged → cs==ww byte-id gate stays green.
