Each type info class representing a VHDL integer type is derived from
integer_info_base. This base class stores some characteristic
information about the integer type e.g. its bounds. However, this data
is accessed by the kernel only while the code generated by the code
generator uses other faster methods to access this
information. E.g. the kernel uses the left_bound value stored
in integer_info_base to get the left bound of an integer type
while code created by the code generator uses a special static method
left() provided by the corresponding integer type info class
derived from integer_info_base.