match cvt_a
    select cvt_a->attributes.count(\nan_b2f) || cvt_a->attributes.count(\nan_f2b)
endmatch

match cvt_b
    select cvt_b->attributes.count(\nan_b2f) || cvt_b->attributes.count(\nan_f2b)
    index <IdString> cvt_b->type === cvt_a->type
    index <SigSpec> port(cvt_b, \A) === port(cvt_a, \A)
endmatch