rust: assertions: Support index field wrapped in BqlCell

Currently, if the `num` field of a varray is not a numeric type, such as
being placed in a wrapper, the array variant of assert_field_type will
fail the check.

HPET currently wraps num_timers in BqlCell<>. Although BqlCell<> is not
necessary from strictly speaking, it makes sense for vmstate to respect
BqlCell.

The failure of assert_field_type is because it cannot convert BqlCell<T>
into usize for use as the index.  Use a constant 0 instead for the index,
by avoiding $(...)? and extracting the common parts of
assert_field_type! into an internal case.

Commit message based on a patch by Zhao Liu <zhao1.liu@intel.com>.

Link: https://lore.kernel.org/r/20250414144943.1112885-3-zhao1.liu@intel.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

0 files changed, 0 insertions, 0 deletions