Latent silent miscompile surfaced by worker-strcontains3 attempting
strings.contains tagged-variadic graduation: wwstage cgcall's
callee_variadic_param helper (cgenutil.ww:60-70) consumed the N_DOT
callee's leaf via callee.str but routed bare fnparamslookup — bypassed
the module hint at callee.lhs.str. When two modules export same-leaf
fns with differing variadic shapes (e.g. strings.contains(str|rune)...
+ bytes.contains scalar (u8|[]u8)), the bare walk returned the wrong
fn's params for arg-prep while the CALL targeted the correct
module-qualified symbol — ABI mismatch.
Direct sister of #34 (049ebc1) which graduated fnret's N_DOT arm
through fnretlookupmod. #4d's commit body (862715d) explicitly
deferred callee_variadic_param's *mod re-routing pending "future
stdlib port introducing a tagged-vs-scalar or variadic-vs-non-variadic
same-leaf N_DOT collision shape." This is that surfacing.
cgenutil.ww: split callee_variadic_param on callee.kind. N_IDENT stays
on bare fnparamslookup (same-module-first post-#4d). N_DOT routes
through fnparamslookupmod(c, callee.str, callee.lhs.str), pattern-
identical to cgcall's N_DOT branch at cgenexpr.ww:2922-2935.
Cstage cmd/w6c/cgen.c:4279-4302 reads callee params via typed AST
(n->lhs->type + cu->params) — module-aware natively, no sister
change needed (mirrors #4d/#28/#31/#34 cstage no-sister notes).
752_modparam_callee: table-driven 3 rows x 2 stages = 6 fixtures.
cross_module_same_leaf_variadic_vs_scalar (the wedge),
same_module_same_leaf (no-regress), bare_leaf_no_collision (control).
#17 filed for the wider convenience-wrapper audit (enumerate all
wwstage cgen* helpers that take *node and do bare-leaf lookups; sweep
for N_DOT-arm omissions). This commit is narrow to callee_variadic_param.
make test 126/126; ww2==ww3==ww4 byte-id holds via 995_self_rebuild.
Hojun-Cho
d9b0c90fbc