Taking &x.o[i] (address-of) or slicing x.o[lo:hi] / x.o[lo:] of a
struct's [N]T-typed FIELD computed the field's VALUE as the base
address (MOVL off(BP),AX) instead of its ADDRESS (LEAQ off(BP),AX) ->
garbage pointer -> segfault. The index read/write path was fixed in
#135; this is the unwired addr-of + slice sibling — both base-address
paths fell to the generic cgexpr(base) auto-deref.
Wire the #135 cg_dotbase_addr / dotbaseaddr helper into the addr-of
N_INDEX complex-base arm and the N_SLICE base arm, symmetric on both
stages (guarded if(!dotbase) cgexpr(base)). Extend the slice element
stride (esz) and default-hi length to an N_DOT array-field base too,
read from the field's element tinfo / array length via the type table
(rule-13) — so non-u8 element slices scale correctly and s.obuf[lo:]
gets the array's element count.
cstage already derived default-hi via base->type (alen); only wwstage
needed the N_DOT default-hi arm. cs==ww byte-identical on every shape.
test/949_dotbase_addr_slice_run: 7 dual-stage rows (addr-of local +
*struct param, explicit + default-hi u8 slice, non-u8 [4]i32 stride,
bare-local control), run + cs==ww byte-id. Regen w6c/wwdump combined.ww.