Add validation for array expressions

[Miauwkeru]

In the case of the cstruct below DATA_LEN is a string called LENGTH. This makes it that char foo[DATA_LEN]; creates a type of <class 'types.char[DATA_LEN]'> which is unexpected as I would expect it to fail if it uses a string as a length specifier or if the expression doesn't resolve to an int.

c_def = """
#define DATA_LEN LENGTH
struct data {
    char foo[DATA_LEN];
};
"""
c_test = cstruct().load(c_def)

So is it an idea to be a bit stricter when parsing the cstruct so this cannot happen?
For example, in the case a #define ... was forgotten it would cause some unexpected behavior.