wwstage's desugarcallargs ran no general per-arg typecheck (only the
narrow #258 array-to-slice arm): any mistyped scalar call-arg silently
miscompiled (int read as a 24B slice header; the -T face was a user
const __wwtests building a garbage test binary). Route every call-arg
through the predicate union isassignable()||assignableaddrfn(),
mirroring cstage type_assignable||assignable_addrfn and the check.c:1869
diagnostic. Confident scalar/aggregate and aggregate/aggregate
kind-mismatch rejects live in shared isassignable; the concrete-to-
tagged arm is shape-matched-lenient via tagshape() (AST mirror of cgen
taggedvariantindext) so genuine variant members keep flowing while
shape-mismatched aggregates reject. Reserve __wwtests under -T in both
stages (mirror the main reservation, check.c:2996). New table-driven
989_callarg_typecheck, 31 fixtures, reject rows proven red on pre-fix
binaries.
Deferred, filed, site-commented: the assign seam rides #178->#36
(typeeqast cannot compare variadic/module-qualified fn sigs); the
same-coarse-shape same-leaf nominal collision over-accept rides #37
(#10/#66 — the distinguishing module is absent from the AST surface
isassignable operates on).