In reply to chr_sue:
What is the intention of this typedef:
typedef bit crc_size;
We no 2 different typedefs.
The forward typedef for classes, like this typedef class C;
and the typedef to define a user-defined type like this
typedef logic [7:0] [3:0] T;
Here T is like an abbreviation with the following decalartion
T var;
mean this is a 2-dim variable var.