Deal with assignments of the form: dest[] = newval destlow..upp = newval where newval has already been interpreted
If this is a four pointer relation, evaluate it, else return NULL.
Statement
Expression
Negate a relational operator, eg >= becomes <
Given an expression e which is about to be returned from the current function, generate an error if it contains pointers to local variables. Return true if it is safe to return, false if an error was generated.