assert(SvTYPE(_svi) == SVt_NV || SvTYPE(_svi) >= SVt_PVNV); \
assert(SvTYPE(_svi) != SVt_PVAV); \
assert(SvTYPE(_svi) != SVt_PVHV); \
+ assert(SvTYPE(_svi) != SVt_PVCV); \
assert(SvTYPE(_svi) != SVt_PVFM); \
assert(!isGV_with_GP(_svi)); \
&(((XPVNV*) SvANY(_svi))->xnv_u.xnv_nv); \